CA2110858C - Radiation responsive surgical instrument - Google Patents

Abstract

A crystal containing detector particularly suited for use in immunoguided surgery capable of detecting gamma emissions present at tumor sites. The instrument utilizes a cadmium-zinc-telluride detector crystal which may be retained within a finger mount positioned over the surgeon's finger. Within this mount there also is incorporated a first preamplification stage designed to accumulate charge signals from the detector as well as to drive a relatively short length of cable to a second preamplification stage located, for example, within a housing at the surgeon's upper arm. The small finger mounted probe may be moved between operative orientations at the underside of the tip of the finger to stand-by orientations at the top of the finger adjacent the knuckles In an additional embodiment, the finger probe incorporates a sodium iodide crystal, the scintillations from which are transmitted via a short length of fiber optic cable to an upper arm mounted housing which contains a photomultiplier tube. Signals from the remote, arm-mounted housing then are transmitted via longer cabling or the like to a control console.

Description

2~ 1~%58 ~.
Attorney Docket NEO 2-149 RADLATION RESPONSIVE SURCICAL INSTRUMENT

Bacl~.ouild of ~he Invention Current and hi~t~ric~l procedures for the ~ ent of colon and rectal cancer have been base~ upon the natural history of tumor spread, and thence, upon operative and non-operative options. Operative options generally have looked to the physical location and surgical resection of tumor. A variety of techniques have been brought to bear in the art with the purpose of aiding the su~ on in ~etec~ing and loc~li7ing neoplastic tissue as part of this surgical procedure. ("Neoplastic tissue", for present p~ ,oses, often is referred to as cancerous tissue, though m~ n~ turnor and m~ n~n- tumor cells also are found in the terminology of the art.
10 The term "ne~pl~hic tissue" inr,l~ldes all of these.) A s~lbst~n~ molln~ of effort in aiding the sùrge~n in loc~ting neoplastic tissue has been through the uhli7~hor- of r~io!~bele~ antibody for detection pu~oses. For eY~mrle~ one technique includes the scinh~ hon sc~nning of p~hent~ injected with relatively high energy, e.g. 13~I labeled antibodies. Such phot~sc~nning or s~inhll~hnn sc~nning provides scinh~ms ~lifficlll~ to int~.~ret or of little value for d~tec~ion of srnall lesions because of blood pool bacLg,ound r~lio~tivity. Co~ ul~ subtraction of io~ ve blood pool agents and dle use of two labeled antibodies (one specific for the tumor and one non-s~;r.~,) have been a(~ cd to enh~ce imq~n~ Nev~ eless, such techniques have been found to provide little, if any, useful i~-fo...~l;oll to the SulgeOIl, especiq-lly over and above CAT scans, m~eti~ reson~,nce imqgings~ and like tr~ition~l techniques. Typically, 20 large tumor is readily located by the ~ur~eon by vi~llqli7 ~ion at the ope.~ lg theater as well as through p~qlpq-~ion~ i.e. the feel of a tumor as op~os~ to that of normal tissue. To achieve operative success, ho.. e~r, it is n~cess~ ~ for the surgeon to somehow locate neoplastic tissue at positions within the body cavity not acc~s~ibl~e with vision, for exqmple intern~lly within the pelvic region or behind the liver or pancreas. It also is n~cess~l.y for the ~urgeon to locate "occult" tumor at any position. Occult tumor or occult neoplastic tissue is that which is so ~imllnitive in size as to be uni~ ntifiqble either by sight or feel. Failure to locate and remove such occult and non-visible tumors generally will result in the continued growth of cancer in the patient, a condition often mi~identifie~ as '~tecull~ntl~ cancer. In general, convendonal diagnostic techniques as, for example, use of the classic gamma camera and the like, fail to find 30 or locate occult tumor. As tumor sites become sm~ller~ the radionuclei~e concenhadons at a given tumor site will tend to be lost, from an imaging standpoint, in the bacL~ound r~ tion necess~ily present.
U.S. Pat. No. 4,782,840 by Martin, M.D. and Thurston, Ph.D., endtled "Method forT~hng, Differentiadng, and Removing Neoplasms, issued Nov. 8, 1988 , ~ .
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reviews such s~int~ tiQn su~ ~ teclm:que and ~l;cc~ses a much improved method for locating, dine~ g and ~movillg nP4p~ Such tecl-n~ e utilizes a r~io1~beled antibody and a po~ 'e radiation detection probe which the ~.~rgeoll may use intraoperatively in orderto detect sites of l~l;o~ ity. Re~llce ofthe prc.~i-""y ofthe detection probe to the labeled antibody, the faint r liqti~n e...~n~ , from neoplastic tissue at occult sites becQ~ Fs detectable, for example, in part bec2~1se ofthe il~hel~,.l application ofthe appro~ e inverse square law of radiation propa~tiQn The procedure is known as the R~1io .. u~o~lided SurgerylM system (12~ l;ded Surgery being a trademark of Neoprobe Corporation, C~-lmhll~, Ohio) and is s~lcGçs~fill n1-liti~n~lly because of a recoglli~on that tumor detectil~n should be delayed until the blood pool bac~ md of cir~lqti~ ra~iol~led antibody has had an opportunity to be cleared from the body. As a ~n~e~ çncç~ the photon emissions or r~ ti~ n ernitted by minor tumors co"~)a ed to su"o~ g tissue beco",es detect~'e in view ofthe pruAimily ofthe probe device to it. Fortuitously, the '840 patent ~ c1osPs the ability of the r~ 1F~I antibody to remain bound to or associated with neoplaslic tissue for e~Pn~led periods of time with the radio tag still bound thereto. Moreover, even though the accretion of radio~ctivity at the tumor site decreases over time, the blood pool bacLgrolmd and surrounding tissue (relative to the tumor sites) decrease at a much greater rate so that the M-lioactive sites can be dele",~ ed readily l~tili7ing a hand held probe pocitioned in close pro~rnity with the tissue under in~ ;~l;ol- Also ~ u~d in the '840 patent is the improved inventive ~ odolo~y foc 1sed upon lower level energy isotopes e~ ng photon çmicsi~s of energy levels less than about 300 Kev adv~nt~geol1sly and, prere~bly, less than about 150 Kev.
The il~ ;nn dc~_loped to support the radio;.. ~-o~ ed surgery system has been called upon to meet rigorous pe,~o""~lce criteria. R~ li~tiQn emitted from occult tumor necess~rily is very sparse and will emit to evoke a relatively low count rate upon detection.
This low count rate, in turn, is developed with a co~,~s~,onding count rate from the same radioisotope which is bac~ground r~ tion~ albeit in itself low, but which must be ~c~4.. -0date~ for. The circuitry involved for such hlsl~ l ;Qn is described, for e~l,p'e, in U.S. Pat. No. 4,801,803 by Denen, et al., entitled "Detector and Localizer for Low Energy , ,~
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ti~n F~ OI-Q~, issued January 31, 1989. To evaluate ~letected emissions and the counts generated the,~iull, with the instrl)mPnt~tion a microprocessor-driven control program has been dc~_loped as is dç~il~d in U.S. Pat. No. 4,889,991, by Ramsay, et al., entitled "Gamma tion Detector with Fnh~n-~d Signal Tr~...P..~", issued Decel.ll,er 26, 1989.
This instn!n.~ iQn suppolling the probe device which is held by the s.lr~eoll and maneuvered within the body cavity is retained within a battery-powe,ed COI cole located within the opel~in~, room. Because of the low levels of signal evoked at the crystal detector within the probe, that device itself carries a p~ r!ifie~ti~n stage for the purpose of gel~lalin~ a signal output sl)it~ble for tr~n~mi~Q;~n by cable or the like to the ndjDcçnt con~ole The -2a-B

~2110858 -p~ )lification stage performs in conjunction with a cadmium telluride crystal detector, and this combination of components is called upon to perform at the temperatures of the human body while undergoing calibration at subst~nti~lly cooler temperatures found, for exarnple, in the operating room environment. This requirement has tended to reduce the energy level 5 discrimin~tiQn flexibility of the devices. The architecture of the hand-held probe, particularly as it is concerned with the noise-free mounting of the cadmium telluride crystal, has been described, for example, in the noted U.~. Pat. No. 4,801,803, U.S. Pat. No. 4,893,013, by Denen, entitled "Detector and Localizer for Low Energy Radiation Emissions", issued January 9, 1990, and in U.S. Pat. No. 5,070,878, by Denen, entitled "Detector and Localizer for Low 10 Energy Radiation Emissions", issued December 10, 1991. The probe so described has an overall length of about 15 cm; is tubular in cross section, and has a forward tip portion canted at an angle of about 30 to aid the surgeon in maneuvering it within the body cavity. Where such maneuvering requires access to tissue adjacent the pelvis or behind the liver or pancreas, even this relatively small hand-held probe may become difficult for the surgeon to position as 15 desired. Once the surgeon has located neoplastic tissue at these hidden locales, it may be desirable then to use the rçm~ining available perception of feel for the purpose of additional verification of a tumor site. However, where the hand is called upon to grasp the tubular handle component of the probe, this surgical exercise may become ~liffi~nlt 20 Su~
The present invention is addressed to apparatus and in~tlulll~nlation for locating sources of radiation e.mi~sions which exhibit improved detec~in~ capability both from the aspect of crystal response and with respect to the accessing of radiation sources. Crystal response and corresponding insll~m~,.lt performance is enhanced through the utili7~tion of a cadmium-25 zinc-telluri~e crystal detector. This improved detector performance is complemente~ with an improved p~ er. The c~lminm-_inc-tellllri~e crystal detector exhibits an output stability improved over the t~,m~l~ture excursions typically encountered within an operating room environment. In complement, the improved preamplifier achieves gain stability under le.ll~ dlule variations as well as an operation exhibiting low noise characteristics. Because of 30 theimprovedoperationalaspectsofthec~ -i.,,n-zinc-telllln~ecrystalforthein~lu.,hl~tionat hand, the mounting a~ ec~ thereof may be somewhat simplified as col~al~d to previous instl.~ e.l-t~l;on utili_ing non-alloyed cadmium telluride crystals. This, in turn, permits the implem~nt~tion of the crystals within probe devices having quite variant structuring, including re si_es.
To achieve improved surgical access to remote body regions, the probe or instrument of the invention is configured with a finger mount which is slidably retained on a select finger of ~1108S8 -the surgeon, for example the second finger. In this regard, the device may be moved forwardly upon that finger to an operative position where the detection components are at the underside of the finger. When so held, stability is imparted to the device by the abutment of adjacent fingers upon guideways formed along the sides of the probe. The probe configuration S also ~lmi~ easy maneuvering of the instrument to a stand-by orientation at the upper side of the mounting finger at a l~ ard location adjacent the surgeon's knuckles. This stand-by orientation permits flexure of the hand for palpation procedures and the like while holding the probe at a convenient location where it readily is ~n~r~l~;d back to an operational orientation.
To achieve the requisite ~ re size required for finger mounting using practical electronic design, a split preampliffcation feature is presented With this arrangement, the finger mount carries a first pre~mplifi~tion stage including a charge accum~ tion network and an amplification stage which, in turn, is cor-fi~lred for conveying crystal derived signals over a relatively short length of cable. That cable of restricted length extends, for example, to a circuit housing attached to the surgeon's arm in the vicinity of the shoulder. Within that remote housing, additional amplification stages are installed for effecting signal tr~nsmission over somewhat lengthy shielded cable to a control console. These latter, relatively higher gain amplification stages exhibit temperature compensation attributes to stabilize gain performance.
Of further advantage, these remotely located amplification stages are within a so~Gwhat stable temperature environment away from heat exchange with the w~ Kl surgeon's hand and patient's body.
In an alternate embodiment of the finger mounted probe, a sodium iodide crystal is employed in conjunction with a relatively short length of fiber optic tr~n~mi~sion cable. This cable extends, as before, to a small housing mountable upon the surgeon's arm in the vicinity of the shoulder. However, the housing now contains a small photo-multiplier tube for conversion of scintillation-based data signals as received from the fiber optic bundle to electrical transmit signals. Isolation of the photo-multiplier tube is initially desirable for this embodiment in~sm~lch as such devices require relativley higher voltages which would not be desirable within inst,~ -el-t~tion positioned closely adjacent a patient or within that patient's body cavity.
Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.
The invention, accordingly, comprises the apparatus and technique possessing theconstruction, combination of elem.onts and arrangement of parts which are exemplified in the following det~iled disclosure. For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings.

- ~ 2110~58 Bnef Description of the Drawings Fig. 1 is a perspective view of a surgeon's hand, arm, and shoulder showing the mounting of a probe according to the invention;
S Fig. 2 is a front view of a ~ulgeoll~s hand showing a probe according to the invention mounted in another operative ~ri~nt~ )n Fig. 3 is a perspective view of a hand of a surgeon showing a probe according to the invention at its stand-by ~ .nt~tion;
Fig. 4 is a ~l~pe~ e view of a probe according to the invention;
Fig. 5 is a top view of the probe of Fig. 6 with a cap component removed to reveal inner structure;
Fig. 6 is a section~l view taken through the plane 6-6 of Fig. 5;
Fig. 7 is an exploded pe~ iV~ view of a crystal mounting employed with the probeof Fig. 4;
Fig. 8 is a multi-channel analyzer plot taken in conjunction with a CdTe crystal;
Fig. 9 is a sequence of plots of counts versus lower window settings or energy for a se.lue~e of le~ tur~s as applied to a CdTe crystal;
Fig. 10 is a plot developed with a multi-ch~nn.,l analyzer ~ltili~ing an alloyed CdZnTe crystal at O C;
Fig. 11 is a plot corresponding to Fig. 12 but employing a CdZnTe crystal at room tem~
Figs. 12A and 12B combine as labeled to form a block diagram of the functional cc.~ onents of a cont~l system ~Cso~te~ with the instrument of the invention;
Figs. 13A and 13B combine as labeled thereon to shown an electrical schematic diagram of a two-stage ~ or employed with the in~ull~n~ of the invention;
Fig. 14 is a top view of another embodiment of a finger mounted probe according to the invention with a cap portion removed to reveal internal structure; and Fig. 15 is a sectional view taken through the plane 15-15 shown in Fig. 14.

Detailed Description The general RIGS procedure colllll~llces with the a~lminictration to the patient of an effective amount of a radiolabelled locator which specifically binds a marker produced or associated with neoplastic tissue. A "locator" includes a substance which preferentially concentrates at tumor sites by binding with a marker (the cancer cell or product of the cancer, for example) produced by or associated with neoplastic tissue or neoplasms. Appropriate locators today primarily include antibodies (whole and monoclonal), antibody fragments, ch; n~i~ versions of whole antibodies and antibody L~ , and l.. ~n;,~l ve,~;olls thereo~
It should be appreciated, however, that single chain antibodies (SCAs such as ~ ose~ in U.S.
Patent No. 4,946,778) and lilce s~lbsl~nces have been developed and they primarily prove efficacious. BioçhP-mictry and genetic ~8in~ 8 may yet produce substances which mimic the fim~inn of antibodies in selectively concPn~ ~ ~ling at sites of neoplastic tissue, though such s~lb~l~n~os may not be subsllmed within the tr~tlitinn~l definition of"antibody". "T orstor" is a term chosen to include present-day ~ntibotlies and equivalents thereof, as well as those s~lbst~nr~,s yet to be d~lelll,ined which mimic ~ntibotlies in the method ofthe RIGS system.
The c~.ying out of r~ ;mmun~guided surgical techn:ques (RIGS) calls for a certain dexterity on the part of the surgeon in maneuvering the crystal co.~l~inil~g probe in close pr~A~mlly and at proper rates along the tissue under investi~tion The probe, which is hand-held by the surgeon, will have a window surface behind which is located a detertor such as a Mr~m:-lm telluride crystal. Re~llse the RIGS surgical approach is one ~I,erein the extent of r~ tion ~ n~ g ~om the locator positioned at neoplastic tissue is quite faint, it becomes n~s~;~ y that a close p,~ "al ~soç;qtion be e~kli~l~ed b~lweell that probe and such tissue.
Because of the rapid fall-off of rn~ tinn as the crystal surface is moved away from such a tissue re~ion in e4ll~l~lence of the inverse square law of ra~ ion propagation, it is ess~ nl ;~1 that the surgeon n~;n~in this close pro,~.""l~ belweell the crystal surface and tissue at which the radioactive locator is conce~ led. The probe window, of course, p~ul~;lj the crystal surface from the tissue and its emril~l""e,lt. In effect, this ~rp1i~tion ofthe inverse square law of radiation prop~tiol- aids in sharply de1i~ g the extent or boundaries of neoplastic tissue. ~ obviously are not employed with such a system where low energy r~ tionis involved, in~much as they would not sharpen the location of r. ~i~tio~ but would lessen the nurnber of received e~ ;ol~C from the faint r~ tion source at the tumor site. It is appalenl, ~I,el~rol~, that a facility of maneuverability ofthese probes becomes an important aspect ofthe surgical procedure. Using co"~Pn1ionq1 probe structures, such maneuverability becon~Ps ~liffic--lt as the sur~eon must probe the pelvic region or regions behind the pancreas or liver.
As this region is ~cc~ 1 the surgeon loses the per~epli./e aspect of sight and must then rely upon the perceplion of feel and ~nh~n~ PI~l of that perceplion with the RIGS system. For B

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very small tumor size, i.e. occult tumor, the sense oftouch or feel is reduced or lost within le areas and the value of the RIGS system beco.~ .es appale.ll. However, indicsti~-nc of occult tumor within such .liffi~JIt to access regions should permit the surgeon's hand to m~nir~ e the tissue found suspect following the in~l;c~tiQn of tumor by the hand letailled probe. This reql~icite flexibility and aCcesQ;t~ility is achieved with the present invention by a probe design which is cc~nfigl~red to be carried and supported by a finger of the ;,. r~eoll and which in the course of difficult acces~; ~g procedure may be moved be~ween active dete~ing -6a-B

and stand-by positions, the latter positions pe-rmitt1ng essent~ y full hand maneuverability at the site of tissue investig~tion.
Refening to Fig. 1, a probe ~sseml~ly according to the invention is represented generally at 10 as it is carried by a ~ulgc~n represented sch~m~tic~lly at 12. The probe or probe component of the assembly 10 is shown at 16 being slidably mounted on the second finger 18 of the hand 20 of surgeon 12. Probe co.llpol1ent 16 is ~~ ,sented as being in an active detection position such that it is mollnted over the portion of finger 18 co...s~,onding with one phalanx bone (connected to the tip ph~l~nx) although location beneath a glove has been contempl~t~ It may, of course, be used on a dir~e.lt finger at the sur~geoll's discretion.
10 In general, the probe 16 will be positioned over the surgical glove ofthe sufgeon 12.
Ad~i~ion~lly outwardly of the glove is an initial length of co.. ~ ting cable or wiring 22 which exten-1s a limited ~iict~nGe along the fore~l.~ 24 of s~geon 12, whc,~ ~pon it is secured by a strap 26 in the vicinity of the elbow joint. It then is seen to extend to the shou~ r region 28 of surgeon 12 at which position a circuit ho~o;r~g 30 is l~ A to the ~ eon's arm for exarnple, by a strap or conn~ctor 32. From the circuit housing 30, a cable 34 extends to a battery powered console located in ~jacency to the surgeon within the operating room. The tr~ncmic~ion arrangement thus shown inclu~1es a pre~mplifc~tion stage (not shown) which is mounted within the probe 16 itself and which is designed to provide an ~mrlifl~atioll of its ~etector output suited particularly for tr~nsmicsiol~ along the length of cable 22 to a second 20 preamplification circuit retained within circuit housing 30. The latter, second pre~mrlifis~tion stage derives a ~rancmit output of ~ iate chara~t~rictic for tr~ncmiss;on over the re!atively lengthier cable 34. This arrangement enhances the c~p~bility for structllnng the n~cess~ y small or ~;...;n~ e probe component 16.
In Fig. 1, the "back" side of probe 16, which is an elastomeric strap, is seen. ~oot~ing to Fig. 2, the opposi~e side of this probe component 16 is revealed. Shown in Fig. 2 as being mounted at or near the tip of the underside of finger. 18, i.e. adjacent or over the t~lmin~l phalanx bone, the length of probe 16 along finger 18 is about 2 cm. This short length permits retçntion of the device while allowing finger flexure. Shown in phantom in the figure is a cavity 36 which serves as a seat within which a crystal ~etector is mounted and an adjacent 30 rectangular ent~losilre or cavity 38 within which the noted initial pre-~mrlific~tion stage may be ret~ine~ With this configuration, it is evident that the ~ulgeon 12 is capable of maneuvering the probe at regions of the human ~n~tomy otherwise quite difficult to access. In the course of such utili7~tion of the probe 16, its oriçnt~ion in the hand 20 is stabili_ed by those fingers of the surgeon's hand 20 as at 40 and 42, the side surfaces of which press against the co,l. ~onding side surfaces of the device in a somewhat natural manner. To enh~nce this stability and ease in maneuver of the probe 16 about the finger 18, guideways of, for exarnple, ,_i shallow curved configuration, extend along each side of the device 16 throughout its lengthwise extent. Thus, the sulgeon can control the orientation of probe 16 by manipulation of adjacent fingers 40 and 42 with respect to finger 18. In effect, a "one-handed" ~na~ipvla~iQn carabili y is realized. This manipulation may caIry out a rotation and tr~ncl~hon of the probe 16 to a stand-by position upon finger 18. Such position may, for example, move the device 16 to a 1QC~;OI1 over the upper side of the third ph~lanx adjacent the palm as shown in Fig. 3. In this stand-by orien-~tion, the active side of the probe 16 as seen in Fig.2 is rotated to the top of the hand 20, as well as moved backwardly toward the palm or knuckles for flexure and llnhins~ered use of hand 20.
Looking to Fig. 4, the probe CO~ ?Ollf nt 16 is shown in pel~pccLi~e. Probe 16 may be formed, for eY~mrle, from ~lllminnm or plastic, and is conffgured having a finger mount ~se-n~t~ generally at S0 which includes a SU1)1JO1l region 52 and an oppositely-disposed concave mount portion 54. Looking additionally to Fig. 5, the support region 52 is seen to include a ~3etector mount portion 56 and a pre-amplifier cont~ainms~t portion 58. Within s3etecto- mount portion 56 there is formed the earlier-noted crystal receiving cavity 36 and in adjacency thereto within the pre-amrlifier con~ainment portion 58 there is located the earlier-noted pre-amplifier coi~ f n~ cavity 38.
Flg.4 reveals that the oulw~ surface of the concave mount portion 54 is configured in concave fashion to develop the above-f3iccllsced slongp~s guideways 62 and 64 eYtf n-ling along the lengthwise extent of finger mount 50. These guideways 62 and 64 aid in m~int~ining and ch~n~ing the orien~tion of the probe 16 through their abufflng contact with adjacent fingers of the su~geon's hand. The intf-rn~l region of the concave mount portion 54 is configured subst~nti~lly as a half cylin-lrir~l surface 63 of radius sele~t~d for nesting against the sulg~on's moun~ing finger as dest~ribed at 18 in Figs. 1-3. This surface 63 extends to two opposilely disposed strap connector portions 66 and 68. Looking additionally to Fig. 6, the strap connector portion 68 is seen to be formed as an elQ~g~te slot . Strap col~ne~ Lor portion 66 is identic~lly f~shio~et3 These connfc~r portions 66 and 68 serve to provide for the a~ h...f .-t of an el~ctomeric web-like strap 70 which functionc to retain the finger mount 50 against the s~,con's hand and eYhibitc s~lfficjçnt flexure or el~stis~i~y so as to permit the movement of the 30 probe 16 about the finger, for eY~mple, in the orient~tions n~ ,se-nl~3 in Figs. 1-3.
Ret~ ing to Fig. 4, the support region 52 is seen to ~ddition~lly support a cap or cover 72. This cover 72 is confi~lred of a material and is ~imf ncione~l so as to seal the cavities 36 and 38 while pc- ~;tl;n~ the ingress or passage of r~ tion into the s~etector mounted within detector cavity 36. In this regard, the cover 72 may be formed of aluminum having a thi~ness~ for eY~mple, of about 0.01 inch (0.25 mm). Figs. 4 and 6 show that the cover 72 is f~chioned having a dowllwd~dly disposed and integrally formed flange or skirt 74 which nests B

21i 0~58 '....
over the support region 52 of finger mount 50. To seal the assembly against the incursion of cont~min~nt~ such as body fluids and the like, attachment between the cover 72 and support region 52 may be provided, for example, with an epoxy cement.
Figs. S and 6 reveal that the preamplifier cont~inm~.nt portion 58 and associated cavity 5 38 serve to mount and retain the first preamplifier stage represented in general at 80. In order to achieve requisite small size and volume, stage 80 preferably is formed including a printed circuit board 82 which serves, in turn, to support surface mounted components, certain of which are l~,lesellted at 84. Typically, the board 82 will function to mount those components on each of its oppositely disposed s~lrf~ces. ~ccessinE the first preamplification stage 80 is the 10 earlier-noted cable 22, the portion thereof imm~Aiately adjacent support region 52 being buttressed by a strain relief 86 formed, for example, of a soft rubber coating. Cable 22 is seen to extend th~ugh an apellurt; in the support region 52 for appl~liate solder connections with circuit board 82. Board 82 is retained within the cavity 38 by an insulative silicon rubber compound represented at 88. Compound 88 is, for example, heat-stable silicone rubber sold 15 under the tr~tlem~rk "SILASTIC". The latter product is an electrically insulative elastomeric adhesive which functions to retain its elastic plo~ ies over a broad range of environmental te~ elatures. The m~t~ri~l is generally referred to as silicone rubber which is an elastomer in which the C linkages of a polymeri7~d hydr~c~l~n are replaced by Si-O linkages. Electrical cc,.--.,-...-ication between the first preamplifier stage 80 and the detector components of probe 16 is provided through a channel or slot 90 extending between chambers 38 and 36. In this regard, a small lead assemblage is shown at 92 e~ten~ling through slot 90. Looking to Figs. 6 and 7, the assemblage providing for the retention of a CdZnTe detector crystal 94 is revealed in general at 96. The outermost co~ onent of assemblage 96 is provided as a cup-shaped crystal - retainer or outer shield 98 formed of lead of relatively thin ~im~ ion~ for example, having a thickness of 0.25 mm. Cup 98 may be press fitted within cavity 36 and is formed having an aperture 100 (Fig. 7) through which the lead assembly 92 may pass. Positioned over the lower surface or seat 102 (Fig. 6) of the cup 98 is a layer of the above-described silicon rubber or "SILASTIC" compound. Extending over the layer 104 are a plurality of strands 106 from a multi-strand wire within the cabling 92 functioning to provide an electrical bias for assertion against the inwardly disposed surface of crystal 94. The strands 106 of the biasing input to the assemblage are seen to be positioned over the upper surface of layer 104 such that they are electrically in~ t~A from the seat 102 and so that they may contact a next adjacently-disposed disk shaped electrically conductive confolmable cushion layer 108 having a lower disposed surface 110 po~i~ioneA over the strands 106 and upon the forwardly facing surface of insulative elastomeric layer 104. The adhesive ~ chm~ nt between these components serves to avoid rnicrophonically induced noise at the crystal 94. With the arrangement thus shown, electircal 2 ~ ~ $
r bias, as well as electrical comrnunction with respect tO charge transfer is asserted from the strands 106 into the electrically conductive cushion layer 108 and, thence, through freely-abutting rel~tionshir with the lower surface of crystal 94 to that component. Preferably, the electric-~lly conductive cushion layer 108 is provided as a non-woven Teflon cloth which is carbon-filled to the extent rendering it an effective conductor of electricity. In general, the m tteri~l is a carbon-cont~ining stretched, highly cryst~lline, ~nsintered polytetrafluol~th~lene InAl l.eted under the tradçm~ "GORETEX". To avoid cont~mination~ it is desirable that the cushion layer 108 be as pure as possible through appropliate wash-type ~ n..~lt or the like.
While no adhesive or the like is employed in the union be~-. Cell the lower surface of crystal 94 10 and the upwardly dis~osed surface of layer 108, some silicone adhesive may migrate about the edge of crystal 94 with ben~fi~! effect. This ~l~'~g~ l is n~h:~vcd in~entl~çh as the periphery of crystal 94 is spaced from the inwardly-disposed surface of cup 98 to define a gap 109 (Fig. 6).
Positioned over the upwardly-disposed surface of crystal 94 is another electrically cor~ ctive deformable layer 114. Formed, for eY~mple, of material ide-ntie~l to that of layer 108, layer 114 serves to cushion the upper surface of crystal 94 against vibratory induce~
microphonic or the like effects as well as to provide electrical contact bel-. ~n its lower surface 116 and the upwardly-disposed surface of crystal 94. In this regard, the electric-~tlly-con~uc-tive layer 114 fUnctiol-c to assert a ground by virtue of the freely-abutting contact of its upwardly 20 disposed surface 118 with a ground lead 120 (Fig. 7) extentling from the lead glou~ing of cable n.
Ret~tining the entire ~csemb!~ge including layer 104, biasing strands 106, cnchionin~
layer 108, crystal 94, cushioning layer 114, and ground lead 120 in proper mntll~lly ~qbl~tting ~ssoc;~tion as well as in a slight compl~,ssion is a disk 122. Formed of r~ tion tr~ncmissive plastic or the like, the disk 122 is sl,uctu~ed so as to provide a press fit within the intern~l slt~Ges of cup 98. To assure the m~inten~nce of this compressive rete~tio~ of the noted co~ onents, disk 122 may be secured a&esively udlizing the noted silicone rubber m~tteri~tl Fig. 6 reveals that the disk 122 retains the crystal sul)pol~ng assemblage at a posidon below the cover 72 in a manner defining a gap 124. This gap 124 serves to isolate the crystal 30 ret~ining assemblage from physical engagement with the cover 72. Gap 124 fimctiollc to provide an acoustic illl~lce to avoid the tr~ncmicsion of vibration from cover 72 which may be occ~cioned by the maneuvering of the probe 16 along tissue under investig~tion Gap 124 is of relatively small height, for example about 0.5 mm, to assure that the rol~ surface of crystal 94 is as close as practical to the tissue under invesdgation. Such distancing of that folwdld surface with respect to the tissue under investigation is quite important in view of the low level of ra 1i~tio~ involved and the noted inverse rel~tionship of ra~i~tion propa~tio~ In . .
B

general, the user of the instrument 16 will witness a rapid fall-off of count response to radiation with the distancing of the forward surface of crystal 94 from such source.
The diminutive size of the probe 16 is achieved both with the utili7~tion of a dual stage preamplification arrangement as well as with the more simplified crystal mounting approach thus described. This latter mounting approach is, in part, made available through the selection of a CdTe material alloyed with zinc and generally l~lesellted by the expression: Cdl xZn~Te.
In general, CdTe detecting crystals exhibit benefits such as operability at room tem~lalu,~, high counting rates and small size. However, for the surgical implementation at hand, they exhibit a noise evoking temperature dependence which heretfore has been accommodated for through the elevation of lower window or threshold energy levels within control Cu~;uilly.
Such an approach to accommodating these attributes of the non-alloyed crystals has, in the past, called for an operational trade-off representing loss of some radiation count data. In general, c~dmi~lm telluride based in~llun~n~s as employed in the operating theater are calibrated at a room or environment~l temperature, for example, the temperature witnessed by the probe during calibration within an operating room may be somewhat below 15-C (59~F). The probe then is grasped by the surgeon, a maneuver which, in itself, will develop a higher ~ell~el~lure from the co~ ication between the surgeon's hand and the probe. For the RIGS procedure, the probe is used within the body cavity where body lempelature is about 39~C. Thus employed, the crystal component of the probe will more than likely reach a lelll~el~ture of about 35 C and in some instances higher. The result from this temperature excursion heretofore utili7ing CdTe crystals has been a generation of crystal dominant noise for which the instrllment~tion has been called upon to evoke an albi~l~y lower window adjllctm~nt.
Looking to Fig. 8, a plot developed with a multi-channel analyzer utilizing a non-alloyed CdTe crystal in conjunction with a 129I check source is revealed. The curve represented in the figure was developed at room temperature (20~C) and in conjunction with a pre-amplifier as described in the above noted U.S. Patent No. 4,801,803 pelrolll~ing in conjunction with a console also as described therein. Count values as identified along the vertical scale of the figure were developed in conjunction with the relatively lengthy count interval of 20 seconds. The horizontal scale of the figure is representative of energy and is graduated in ~bi~ y channel designated units. In this regard, the channel identified at 800 will represent an energy of 29 kev, while that at the channel 200 designation will exhibit an energy valuation of about 7.5 kev. The figure reveals a principal count region 130 peaking at the noted 800 channel designation which is represent~tive of the response of the crystal and preamplifier to impinging radiation from the 129I check source. Adjacent to the peak portion 130 is a relatively constricted region 132 leading from a skirt portion 134 of the peak region 130 to a rapidly rising noise response curve 136. As is apparent, in operating systems ~ 1 1 0 ~ 5 8 _ according to the invention, a lower energy window is elected at the region 132 and at a location there-along which permits the ~thenng of all data possible from the desired skirt region 134.
As the lower window is, in effect, moved to the right in the sense of channel numbering or energy, count data at the skirt region 134 is effectively discarded in the interest of noise 5 avoidance. Where CdTe crystals are utilzied as in the past, the elevation of operational temperature or environment, in effect, has evoked a movement of the noise region 136 to the right in the sense of the figure, thus requiring that the lower window threshold or energy level of the system be co.~ ondingly moved toward and into the skirt region 134.
The effect of temperature upon the noise Cha~ h~ of a CdTe crystal is illustrated in connection with Fig. 9. Refe~ing to Fig. 9, curves as at 138-143 were developed from data generated in connection with the taking of a sequence of count ouhputs from a CdTe crystal mounted as a probe for temp~lul~s, respectively, of 10, 15-, 20-, 25, 30, and 35 C. The hc";zol~lal scale of the chart is gra~u~ted in lower window settings for a console as described in the above-noted U.S. Patent No. 4,801,803. The preamplification stage utilized in compiling the data also is described in that lGÇcrence. In general, it has been dele. " .;n~l that the domin~nt noise evolved in systems employing CdTe crystals is a characteristic of the crystal itself as opposed to being a characteristic of, for example, supporting circuitry such as a p,ea~lification stage. In conh~listinction, for the alloyed CdZnTe crystals, the opposite condition obtains, the crystals eYhibiting a stability over a broader temperature ranges to the extent that noise which may g~"lcl~ted is domin~ntly genel~ted from the ~u~lling cir~;uilly.
Fig. 9 shows that at relatively cooler temperatures, i.e. lO C as represented at curve 138, a broad selection of lower window settings as thresholds is available, noise development being relatively low. Thus, should the probe be used only at that temperature, the lower window or energy threshold setting can be elected at a leftward region of the chart well away from the data containing skirt collll)onent as at 134 described in conjullclion with Fig. 8. Note that a noise count generally will be about 25 counts per 10 seconds as l~r~sented in Fig. 9 in conjunction with curve 138. For the surgical applications required, however, this lower tem~l~ture is not realistic. Background noise will vary radically as tel~e,ature increases. For example, increasing the temperature by 5 C as represented at curve 139, results in an elevation of noise inti~lce~ counts from about 100 to 200. Correspondingly, elevation in operation te~ll~,ature to 20 C as represented at curve 140 evokes an off-scale noise in the 400 to 500 counts per 10 second range. Accordingly, the lower window setting or lower threshold of evaluation must be moved towards the skirt coulpollent 134 as described in conjunction with Fig. 8. At room tem~ature, for example 25 C, the system will look for a stable lower window setting, for example, as at position 84. However, for the probe to operate at 30 C or 35 C, then the lower window setting must be moved substantially to the right representing a much higher lower ~ 2110~8 threshold of energy and a level encroaching upon the valid count data otheIwise available from the skirt 134.
The preferred Cdl xZnxTe detector crystals for the probe 16 as well as other probes exhibit very high stability with respect to noise generation when subjected to variations in 5 temperature. Thus, these crystals are ideally suited for surgical procedures where calibration will occur at operating theater temperatures, i.e. about 15~C and the probe devices will absorb the heat of the surgeon's hand as well as the heat em~n~ting from the body cavity of the patient undergoing surgery, a temperature excursion amounting, for example, to about 15 or 20~C.
The proportioning of the Cd component and Zn component of the improved crystals may vary 10 to provide an effective ratio selected to suit the particular requirements of the user. However, a lower limit or boundary for the proportion of zinc wherein x equals about 0.2 has been determined, while a correspondingly high boundary or limit wherein x equals 0.8 has been determined. The alloyed crystals are m~rketed by Aurora Technologies Corporation, San Diego, California, 92067. Additional information concerning the alloyed crystals is provided 15 in the following publi~tions:

Butler, Lingren and Doty, "Cdl xZnxTe Gamma Ray Deleclor~", IEEE Transactions on Nuclear Science, Santa Fe, New Mexico, Butler, Doty, and Lingren, "Recent Developments in CdZnTe Gamma Ray Detector Technology", Proceedings of the International Symposium of the SPIE, San Fe, New Mexico, July, 1992 Doty, Butler, Schetzina and Bowers, "Properties of Cadmium Zinc Telluride Grown by a High ~Gs~ule Bridgman Method", J. Vac. Sci. Technol., Vol. B10, June/July, 1992.
Referring to Fig. 10, an evaluation of a Cd.g7.n.2Te crystal employing a 129I check source and the pleall~lifier described later herein is charted as the output of a multi-channel analy~r. Vertical scale in the figure lep~sel-ts counts per 20 second interval, while the horizontal scale, as before, represents multi-channel analy~r channel designations which, in effect, represent energy. In this regard, the radiation-based count data is derived at about 29 kev and is l~r~sell~ed as the peak region 144. Correspondingly, the relatively flat region 146 shown on the curve exten-ling to the skirt region 148 is desirably of relatively large extent and considered to represent predominantly preamplifier noise, the latter noise being principally present at the spike region 150. The data repl~sellted by the chart at Fig. 10 was taken within an ice bath, i.e. with the alloyed crystal at 0~C.

Utilizing the same test set-up and the same alloyed crystal, the same crystal evaluation then was undertaken at room te,l.pe,~ture, i.e. at 22 C and the results plotted at Fig. 11. Note in Fig. 11 that the data coll~ctioll peak region 151 remains essentially the same as that observed at 144 in Fig. 10. Similarly, the flat region representing concistçnt noise at 152 remains subst~nti~lly the same as that described at 146 in Fig. 10 and that the noise spike excursion 154 remains essçnti~lly the same as that shown at 150 in Fig. 10. In effect, the alloyed crystal is seen to ~rOl~ with a stability over a subs~nh~ t~hQrl of temperature. The flat, concictent noise regions as at 152 and 146 in Figs. 11 and 10 also represent an improvement in preamplifier ~lr~ nce. for eY~mrle over the performance l~pl~ senLed at Fig. 8.
Referring to Figs. I2A and 12B, a block diagl~ atic represe~t~tion of the signaltreatm~nt and control circuitry employed with the probe ~csembly 10 is revealed. In Fig. 12A, that crystal which is being employed, for example crystal 94, is again so labeled for this figure, and is shown having one face courleA to ground through line 157, while the opposite, biased face thereof is coupled via lines 158 and 159 to a bias filter lepl~sçnte~ at block 160. Bias filter 160 is part of the earlier~es~ibe~ first or inidal pre~rnrlifi~tion stage 80 herein idçntified in Fig. 12A by a dashed boundary with the same numeradon. The input to the filter 160 is derived llltim~tely from cable 34 (Fig. 1) and is ,~pr~sulted in Fig. 1 lA at line 161 as being applied through that cable which again is l~n sented by the numeral 34. Line 158 col,.,;,~onds with the muld-strand line 106 described in connectio~ with Fig. 7 and functions to supply an 20 a~pr~liate bias, for eY~mrle, 80 v to the l~dlwa -l surface of crystal 94. This bias em~n~tes from a power supply shown at block 162 in Fig. 1 lB and ,~l~;sented at the labeled line 163.
Line 158 from c~ystal 94 is shown eYt~n-lin~ to an integrator stage 164 of the first ~mrlifiçr stage 80. The integrated v~ tion of a detected radiation disturbance or charge c-h~t~7e~ signal then is shown dil~cl~ as ~ ,sent~ by line 165a to a driver-amplifir~tion network shown at block 166. Line 165 ad(litioll~lly is part of the cable or wiring 22 as it eYtel-d~ along the arm 24 of surgeon 12 as ~1iccusse~1 in conjunction with Fig. 1. Line 165a extends to a second pre~mrlifiration stage ~esç~i~ as located within a housing 30 ~t~ ~h~A, in turn, to the shoulder region 2B of the a~n of the surgeon 12. Cable 22 also may carry ground and +12v supply as shown"es~ ely, at lines 165b and 165c. The noted 12v power supply 30 as r~l~s~ted at line 165c is derived for the driver amplifier stage 166 from the power supply 162 (Fig. 12B) as represented at line 167 which, as shown in Fig. 12A, is ~ ecl~l to a probe cuIrent network ~ple~llted at block 168. Under lllic,oco"~pu~el control as rtl,r~sente~ by line 169, the networ~ 168 develops signals, for e~mple, determining whether the cable 34 (Fig. 1) has been properly collnected to a console-based control system as described in above-noted U.S. Pat. No. 4,801,803. Delive~y ofthe 12v B

8 ~ ~
._ power supply for the dual stage preamplifier system is represented at line 170 as extentling to the driver-amplifier stage 166 via cable 34 and line 171.
Ground to the instrument 167 also is developed from the power supply at block 162 as represented at line 172 in Fig. 12A and which is seen exlending to cable 34 and via line 173 to the driver-amplification stage 166.
The output of the driver amplification stage 166 is represented at line 174 extending through the cable 34 and then is represented as line 175 to the input of a normAli7ing amplifier depicted at block 176. The network represented by block 176 functions to amplify or atten~ te, i.e. scale the noise characteristic of any given in .11 ulllent as at 16 and normali~ the value thereof or render it consistent for later comparison stages. Generally, for example, the 27 kev energy level gamma ray generated pulses in a system employing 125I will be about five times higher than noise levels. Normalizing amplifier network 176 will establish those noise levels at some predetermined level, for example 200 millivolts, and the resultant proportional valid gamma related pulses will become about lv high for purposes of ensuing comparison functions. It may be observed that the amplifier network at block 176 is controlled from a digital-to-analog converter network represented at block 177 via line 178. Network 177, in turn, is controlled from line 179 exten~ling, as shown in Fig. 12B, to block 180 representing a microcc,lllpLIlel network. The norm~li7~d output developed from network 176 is presented along lines 181 and 182 to a noise average circuit as r~,Gsented at block 183. This network 183 determines an averager amplitude value for the noise of a given system with a given instrument 16 and provides a corresponding signal as represented at line 184 (noise amp) which is employed as above described as information used by the rnicrocolllpulel 180. This information, in addition to being employed with the normAli7ing amplifier network l~pl-,sented at block 176, may be used to develop a low window valuation for the comp.rllison function.
Line 182 also extends via line 186 to a pulse acquire network leplesenteA at block 188.
This network funcdons, when activated, by the microcomputer represented at block 180, to acquire the value of the highest pulse amplitude witnessed at line 186. Periodically, this information then is tr~nsmitte~ to the microcomputer at block 180 as represented by line 190.
Representing a form of peak detector, the network is sometimes referred to as a "snapshot circuit". Also produced from line 182, as at line 192 and block 194, is a buffer amplifier which will provide at line 196 an output representing received pulses which may be made available to the system, for example, at a console (not shown).
Line 181 extends, as shown in Fig. 12B, at line 198, to one input of an upper window coll~ator represented at block 200 and a lower window comparator illustrated at block 202.
The threshold level for comp.rllative purposes employed by the network at block 202 is shown asserted from line 204 and, preferably, is developed by the logic of rnicrocomputer network ~110~58 180 at a level selected above the noise amplitude signals generated from line 184. Of course, manual setting of such windows can be carried out and such setting in either event is in reliance upon the discourse presented hereinabove, for example, in connection with Figs. 8 through 11.
The upper window of acceptance for valid radiation interaction is established from a 5 corresponding line 206. This threshold setting may be made from the information taken from pulse acquire network 188.
Returning to Fig. 12A, the upper window and lower window threshold selections are made under the control of the micl~co,ll~ulGl network at block 180 which controls the digital-to-analog network shown at block 177. It is the characteristic of such networks as at block 177 10 to provide an output which is comrri~e l, for example, of 256 steps of varying amplitude. The pclcenlage of incl.,melllation from step to step will vary somewhat over a range of voltage values provided. Accordingly, the outputs from this conversion network at block 177, as shown at lines 208 and 210 are directed to squarer network shown, respectively, at blocks 212 and 214. These networks function to square the current outputs at lines 208 and 210 and thus 15 achieve a ullirolm ~.~e,llage in~G...~.-t;-l;on of the threshold defining outputs at lines 204 and 206.
Returning to Fig. 12B, the outputs of the col~tor networks shown at blocks 200 and 202 represent c~n(lid~te pulses which may be above or below the given thresholds and are i(let~tifie~l as being presented as "UW PULSE" and "LW PULSE" along respective lines 216 20 and 218. These lines are shown directed to a rGal time pulse ~li~imin~tor network represented at block 220 which carries out Boolean logic to determine the presence or absence of valid pulses. Valid pulses are introduced to the microcolllpuler network 180 as represented by line 122.
The microcomputer nclw~,lh l~rGsented at block 180 pelrolms under a number of 25 operational modes to provide both audio and visual outputs to aid the surgeon in locating and dirrelc..li~ting tumorous tissue. In the former regard, as l~lesellted at line 224 and block 226, a volume control function may be asserted with amplitude variations controlled from a solid-state form of potentiometer lGpf~sented at line 228 and block 230. Control to potentiometer 230 is represented at line 229. Further, a "siren" type of frequency variation may be asserted as represented at line 232 to an audio ~mplification circuit represented at block 234 for driving a speaker as represented at 236 and line 238. With the noted siren arrangement, the frequency output from speaker 236 increases as the instrument 16 is moved closer to the situs of concentrated radiation. of course, conventional clicks and beeps can be provided at the option of the operator.
The microcolll~uler n~,lwclh 180, as represented by bus-defining arrow 240 and block 242 also addresses an input-output network which, as lGplesented at bus arrow 244, functions 8 ~ 8 '_ to provide a pulse count output of varying types as well as outputs representing volume levels, pulse height, noise levels, and battery status. These outputs are provided in visual format at a visual display represented at block 245. Similarly, the input-output function represented at block 242 provides apl"o~liate sc~nning of switches or the like which may be employed with the control and are represented by block 241 and bus input arrow 243. During a given counting operation, the microcomputer network at block 180 functions to control a light emitting diode drive network represented by block 246 from line 248. The drive network represented at block 246 is shown providing an input as represented by line 250, to a light emitting diode (IED) display as represented by block 251. A serial output port of conventional variety also may be provided with the system, such ports being represented at block 252 ~eing addressed from the micn~compuler represented at block 80 from line 254 and having output and input co~ onents l~)l.,se,lled by arrow 256. A real time clock-c~len~r cc~ on~l,t having a non-volatile memory also may be provided in conjunction with the functions of the microcomputer network 180 as represented by block 258 and bus-arrow 260. Further, the microcolll~ul~r may be employed to monitor the p~.Çol~l~ance of the power supply represented at block 162. This is shown being carried out by the interaction of the microcolll~)ul~i network with a multiplexer represented at block 262 and having an association represented by arrows 264 and 266. It may be observed that the power supply also provides a +5v source for the logic level coll-pollents of the circuit as represented by line 268; a -5v source at line 270, as well as a -9 source at line 272 for purposes of display drive, and finally, a 2.5v reference as represented at !ine 274 to provide reference input for the preamplification analog circuitry.
Retmning to Fig. 12A, the microcompuler network as represented at block 180 alsoprovides an input to the digital-to-analog conversion network represente-1 at block 177 which corresponds with the in~ eous pulse rate and this information is conveyed to a pulse rate amplifier network l~l~senled at block 276 via line 278. The res~llt~nt output, as lt;p~esenled at line 280, may be provided, for example, at a convenient location upon a console. This circuit represented at block 276 also may be employed to generate a calibrating pulse for testing the downstream components of the system. Thus, the microcomputer represented at block 180 applies a prefletermined pulse level through the digital-to-analog conversion network at block 177 for presentation to the amplifier network represented at block 276. The r~slllt~nt output at line 282 is selectively switched, as represented by block 284, to define pulse width from the microcolll~ul~r input at line 286 to generate the calibrating pulse at line 288.The ~liminlltive~ finger-ring-like structure of the probe 16 is achievable on a practical basis initially through the employment of a plean~lificatiQn system which incorporates first and second stages. These stages are interconnected along the surgeon's a-rm by the earlier-noted cable n and the first stage 80 is so designed as to provide an initial signal tre~tm~nt and Il 2 1 ~Q~
" ~.
an output topology particularly deAicated to the driving of data along the limited length of that shielded cable. The practically ~ssemble~ but small size of this first stage 80 additionally is achieved through the utili7~tion of, for example, surface mounted co,~ponents. While the entire structure in~!Urling the first and second stages may be foITned together in a unitary f~chion, for probe applications such as the present requiring a splitting of these stages, the printed circuit may be made so as to be severable at an app~opliate location. The first stage is represente~l at Fig. 13A and the second stage is shown as such a continll~tion for the entire circuit in Fig. 13B. A parting line beL~n these components of the circuit is conjunctional with the ~s~ci~tion~ belin~ belw~ll the two drawings.
10Looking to Fig. 13A, the crystal 94 reappears with the same numeration. The upward facing surface of crystal 94 is coupled to ground as l~pl~sented by line is7 which lea~pe from Fig. 12A. Similarly, bias is asserted to the r~alward face of crystal 94 from line 158, again lcappea-~ng from Fig. 12A. An 80v bias voltage is applied to crystal 94 through the earlier-noted bias filter 160. In this regard, the voltage is seen applied from line 161 to a - ~e~ourling network inch~ling resistor R1 and c~p~itor Cl. This network reduces noise which might otherwise be injected f~m the power supply line 161. From the network incorporating c~ tor C1 and resistor Rl, the bias voltage is supplied through a very large value resistor R2 to lines 158 and 159. In general, the larger the re-sist~nce value of resistor R2, the smaller the ~qmo~)nt of noise which may be contributed by that cclll~onent. A small amount of current will 20 flow through resistor R2 and its functio~ is to m~int~in an appr~liate bias at the crystal 94.
That bias will approach the bias voltage applied from line 161. In this regard, the reCict~nce of crystal 94 generally will be quite large. Line 158 is seen to extend to a bloc~ing c~rar-itor C2 filnctiol-ing to block the bias voltage at the crystal 94 from the inputs of subseque.lt i~l~f.~li..g or ~mrlificatiQn stages. Accordingly, the o~osile side of caracit~r C2 is seen coupled via line 290 which is coupled, res~cc~i~ely, via lines 292 and 294 to a network including a charge aCcumnl~tor c~pacitor C3 and a bleed resistor R3. C~pacitor C3 receives the charge which is liberated by the crystal 94 in the event of a gamma strike. This voltage is witnesse~l, for eY~mrte at node A, while the voltage at node B will have an appr~ ately O value. Resistor R3 slowly bleeds the charge at c.~rac-itor C3 and, thus, has a relatively high resict~nce value, 30 for example, about 200 meg~ohm~ Such blee~ing activity avoids saturation of the system. In view of the ~cumnl~tion of charge with respect to capacitor C3, the first pre~mplifier stage generally is r~fe.,~d to as an int~ tor as described earlier in conjunction with block 164. That block numeration a~e~ in general in conjuncl-on with such integrating co~.~onents of the instant first stage. Line 290 also is seen to extend to the gate of a junction field effect t~nCistor (J~T) Ql. Transistor Q1, in combin~tion with PNP transistor Q2, and NPN transistor Q3 parti~ir~teS in this charge ~cc~ml~l~tion at c~r~citor C3 of the inlC~alOr categori~d stage 164.

B

Note that +12v from earlier-described line 165c is provided to the stage 164 from a line - designated with the same numeration through resistor R24 to a line 296. Similarly, ground is asserted from along line 165b as earlier ~le~s~ibe~ which is in~ir~ted to extend to a line 298. In similar f~chioll, the output of the first preamplificatiQn stage 80 is seen, as before, at line 165a.
Line 296 extends to a connection with a resistor R5 to line 300 which is coupledbetween the drain terminal of tr~nsictQr Q1 and the emitter of tr~nsictor Q2. Line 296 also eYten~s through resistor R4 to a network 302 incl~l~ing c~racitor C4 and Zener diode Dl which are coupled to the source te~nin~l of tr~n~Cictor Q1 via line 304. Network 302 func~ions to bias the source t~orrnin~l of tr~ncistQr Q1 to a~lu~ ely 3v. The collector of transistor Q2 10 is coupled to line 306 which extr-nds to node A at line 292. Line 306 is seen to col~l;n~t as line 308 to the co!lp~ctor of tr~nsist~r Q3 and the emitter thereof at line 310 extends through resistor R8 to ground line 298. The ba~ses of tr~ncictors Q2 and Q3 are ~ssoci~te~ with a divider network within line 312 ext~n~1ing between lines 296 and 298, and incorporating ~s;st~ R6-R9. In this regard, the base of tr~ncictor Q2 is coupled via line 314 to line 312 inle~ te resistors R6 and R7, while the base of tr~nsictor Q3 is coupled via line 316 to line 312 in~el...~.1i~te resistors R7 and R9. Thus configured, a const~nt voltage is applied at the base of tr~nCictor Q2 via line 314. C~r~citQr C5 carries out a noise re~lction function at that base. In similar fashion, the jllnctiot- bel-.een resistors R7 and R9 provide a bias voltage to the base of tr~nSictor Q3 via line 316. r~p~çitor C6 within line 318 is seen coupled from line 312 at line 20 316 to ground line 298 and functions to by-pass a.c. p~, lullations at the base of tr~nCictOr Q3 to ground. -With the arrangement shown, tr~nsistors Q1 and Q2 operate as a current mirror whiletr~nCict~or Q3 ~,.ro.ms as a current source. The output of the integrator function is di~t~,d via earlier-clescrib~ line 292 to the base of NPN tr~nCistor Q5. Tr~ncictor Q5 in col-jullclion with PNP tr~ncictor Q4 cons~ te a non-inverting voltage ~mplifier with a gain of about 3. The amplifier is configured such that the collector of tr~ncictor Q5 is co~ne~te~ via line 320 to line 296 and illcol~l~tes a bias resistor R11. The emitter of tr~ncictor Q5 is coupled via line 322 to line 324 interme~i~te gain ~efining resistors R12 and R13. Line 324 is seen to extend bel-.een ground line 298 and the collector of tr~ncictor Q4. The latter compo.lellt Q4 is 30 configured such that its base is coupled to line 320 via line 326 and its emitter is connr,c~ to line 296 via line 328. A capacitor C9 is seen coupled to line 296. To achieve a ullirolmilr from one prearnplifier ~csembly to another in the instant system, the gain of this ~mp!ificatioll stage is establishe~l by the ratio of the sum of the reSist~nce values of resistors R12 and R13 to the resict~nce value of resistor R13. This arrangement avoids having a gain depe~lent upon the functioning of the trancictQr devices thlo-mcelves. A desirable plope ly of the ~nlrlifier configuration of tr~nsic~tors Q4 and Q5 is that the input r~cict~nce at the base of transistor Q5 is Il 2 ~ 5 8 very, very large. This is provided in order to avoid the loading of the output of the circuit.
Correspondingiy, another advantageous prope,l~ of the transistor Q5-transistor Q4 co~fi~ration resides in the aspect that the output impedance or resistance, i.e. the output resistztnce at the collector of trSancistQr Q4 which is asserted at line 165a is rather low. For exarnple, the m~gnit~ e of this output reCictstnce is on the order of 90 ohms, a level which permits the driving of the shi~lded cable descrtbecl in collnection with Fig. 1 which e~ttends from the probe 16 to the second ~)r~ t~ lificSttion stage houcing 30 and is represented as being inc~.~ted within cable line ~. In general, for the isotopes corttemrlStted~ the output voltage swing at line 165a is ~~ 5 and 10 rnillivolts.
Now looking to Fig. 13B, the second preamplification stage is revealed. For the embodiment lG~r~s~,~to~ in Fig. 1, this stage will be incol~latcd within the amplificSttion stage housing 30 affixed to the ~ ,~n~s sho~llder. However, it should be understood that the entire ~rc~n~l.lificSttiolt unit lc~senled within Figs. 13A and 13B can be employed as a continuous circuit without the noted srlitting. The task of the second prestmr!ificsttio~ stage is to provide S~d~itiQnStl gain in view of the relatively low voltages asse.t~d at line 165a and to achieve a form of repro~ ctiolt of the waveform r~sent~.d by the input signal to the system and sou.e~hat r~l~luc~ in A~pl l~Pd form at line 165a Line 165a is seen directed to a network serving to carry out an applo~ of di~erentist i~n which i~ ndes c~ or C7 and resistor R15 within line 330. Line 330, il~COl~ nting resistor R14, extends to line 332 and resistor R26 to +12v 20 supply at line 165c. A diode col~nected tr~ncistor Q10 is coupled within line 330 between resistor R15 and line 165b or ground. NPN device Q10 fltnetioltc to retain the Ope~dlil~g point bias at the base of NPN transistor Q7 which is seen coupled to line 330 via line 334. The peak output of the a~lo~ e dirr~ ;Sttion evoked in CO~ CS;Ol- with resistor R15 and c- tp~ or C7 is considered to ,~senl the ms~nitude of the charge evoked at the crystal 94 and as ~,ese-ntc~d at line 334 to the base of NPN ~anSictor Q7. Trs~ncictor Q7 and PNP ~nCictor Q6 form an amplifi~S~tion stage quite similar to that ~esçribed in conjunc~ion with transistors Q4 and QS in Pig. 13B. To enhSlnce a dirre~ ~ti~Sltion filnction~ the input resict~nce at the base of tr~nCictor Q7 is rather large and the gain of the ~mrlifi~tion stage inrlu~ing t~nCictors Q6 and Q7 is controllable and sel..~cte~ as about 19 or 20. Note that the stage is configured such that 30 the coll~ctor of tr~ncictor Q7 is coupled via line 336 through bias resistor R16 to line 330 while the emitter thereof is couple~ via line 338 to line 340 which, in turn, is connecle~ belween the collector of tr~nsistor Q6 and ground line 165b. Line 338 is positioned interm~ te resistors R17 and R18 in line 340. The emitter of transistor Q6 is coupled via line 342 to line 330 and the output of the stage at the collector thereof is present at line 344. As in the earlier case, the gain of this ~mrlifi~tion stage is very controllable and is determined by the ratio of the ~s;,l~nce values of le~ist~.~ R17 and R18. The output imre~nce at the co!lector of transistor B

~110~58 Q6 is rather low, again on the order of 90 ohms. This low output impedance permits a considerable flexibility with respect to the m~Fnitll~e of the components ~vithin the topology to follow. As before, the gain of the configuration of the amplification stage is quite stable, not being a function of the individual transistor devices. Output line 344 is seen to extend through resistor R10 which is associated with a c~paoitor C10 coupled within line 346 between line 344 and ground line 165b. Thus configured, the network including resistor R10 and capacitor C10 conctitl~tes a low pass filter with the function of elimin~ting as much electrically generated noise as possible. Line 344 then is seen to extend to a coupling capacitor C8 which functions to couple the resulting voltage at the junction of resistor R10 and capacitor C10 in conjunction with resistor R20 to the input of a next amplification stage. That next amplification stage is comprised of NPN transistor Q9 and PNP transistor Q8.
Bias voltage is supplied to the base of transistor Q9 in conjunction with resistors R19, R25, and diode co~lne.;le~ transistor Q11 in the same fashion as the bias selected with respect to transistor Q7. In this regard, note that resistors R19, R25, and transistor Q11 are coupled within line 348 between lines 330 and 165b. Resistor R20 is coupled to the base of transistor Q9 and thence via line 350 to line 348 at a location inte~neAi~te resistors R19 and R25. If there is a bias point variation at transistors Q8 and Q9, for example, as a function of temperature change, it is likely that the output of the stage would evoke a corresponding and objectionably large change. The majority of such variation resides in a change at the base-emitter voltage of transistor Q9. Transistor Q11 functions to offset that change in bias voltage to greatly reduce the lem~.~ dependency of the ~mplification stage. In effect, utilization of transistors Q10 and Q11 in the circuit of Fig. 13B provides a substantial and important t~ el~Lul~ stability for the circuit. The same form of stability is not implemented in connection with the circuit of Fig.
13A in view of the relatively low gain developed by that circuity. It may be observed ad-lition~lly that with the split prearnplifier approach, the longer gain stages of the amplifier are retained within a more stable t~m~ e environment.
Now looking to the final amplification stage in detail, it may be observed that the collector of NPN transistor Q9 is coupled via line 352 through bias resistor R21 to line 330, while the emitter thereof is coupled via line 354 to line 356 which, in turn, incorporates gain de~ming resistors R22 and R23 and extends between line 165b and the collector of PNP
transistor Q8. The base of transistor Q8 is coupled via line 358 to line 352, while the emitter thereof is coupled to line 330 via line 360. The output of the final amplification stage is provided at the collector of transi~tor Q8 which is seen, in turn, coupled to earlier-described line 174 (Fig. 12A) which reappears in the instant figure. In general, it is desired to set the biasing of transistors Q8 and Q9 such that the output at line 174 under queiscent conditions is 8 ~ 8 -just above 0 volts. This permits accommodation of energetic isotopes which may produce excursions of 8 or 10 volts.
The finger mounting probe arrangement of the invention also can be employed withdifferent forms of radiation detectors. Looking to Figs. 14 and 15, a sodium iodide-based S finger mounted probe is r~presel1ted generally at 370. Probe 370 exhibits the same appeal~lce as the probe 16 represented in Fig.4 and, in particular, includes a support region 372 similar to that at 52 in the earlier embodiment beneath which is located a concave mount portion 374 (Fig.
15). Elongate concave guideways 376 and 378 are located on either side of the support region 372 and generally outwardly of the concave mount portion 374. These guideways, as before, aid the surgeon in maneuvering the probe 370 about the finger when ~ltili7ing the next adjacent fingers. Just below these guideways at 376 and 378 are elongate slots, one of which is shown in Fig. 15 at 380 in Fig. 15. An identical slot is located beneath guideway 378 and these slots provide strap connector portions of the device for purposes of mounting an el~stom~ri~ web or strap 382 in the same fashion that strap 70 is connected to device 16. Just above the support portion 372 is a detector mount portion 384 within which a crystal ret~ining cavity 386 is formed. Fig. 14 reveals a bore through which a fiber optic bundle 390 extends inco,-""..--ic~tion with the cavity 386. The base components of device 370 including the support region 372, concave mount portion 374, and the guideways 376 and 378 may be formed integrally of an opaque plastic. Over that portion, there is positioned a plastic cover 392 having a skirt portion 394 (Fig. 15) which nests against a ridge 396 (Fig. 14) formed within the support region 372. The cover may, for example, be adhesively attached to the unit 370. A
sodium iodide crystal is shown in Fig. 15 at 398 being positioned within a thin lead cup 400 and retained in position within that cup 400 by a silicon rubber adhesive represented at 402.
Preferably, the crystal 398 is silvered on all sides except at its light commuting contact with bundle 390. At that location as seen at 404 in Fig. 15, an optical grease may be employed to improve the ~ncmicsion of light from the crystal 398 to the bunde 390. Note that a gap 406 is derived belween the forward surface 408 of crystal 398 and a portion 410 of the underside of cover 392 for crystal protection. Bundle 390 extends to a photomultiplier device (not shown) which is retained within a shoulder mounted housing such as that shown at 30 in Fig. 1. The output signals from the photomultiplier device extend via cable as at 34 to a central console which may be configured as described in conjunction with Figs. 12A and 12B. Exemplary of photomultiplier devices which may be employed with the instant probe embodirnent is a Model R-1635-02 photomultiplier tube marketed by ~m~m~tsu Corp., Bridgewater, N.J. In general, that device has overall ~lim~ncions of about 1 cm x 5 cm. Advantage further accrues with the remote location of the photo-multiplier. In this regard, such devices perform at ~ 2110~58 ~ .
relatively high voltage, i.e. 1000 v. By so remotely locating them, they are desirably positioned away from the patient.
Since certain changes may be made in the above-described system, apparatus, and method without departing from the scope of the invention herein involved, it is intended that all matter contained in the description thereof or shown in the accompanying drawings shall be in~ lt;led as illustrative and not in a limiting sense.

Claims (27)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Apparatus manipulable with the arm and fingers of a surgeon to detect and locate sources of radiation, comprising:
a finger mount having a support region and an oppositely disposed finger mount portion configured for slideable positioning and retention upon a portion of a select, one of said fingers, and a detector mount portion positioned at said support region having a detector seat and sidewalls extending to a forward opening;
a crystal detector mounted at said detector seat for response to said radiation to provide a detector output;
a window transmissive of said radiation, mounted over said detector mount portion;
transmission means responsive to said detector output for providing a transmit output; and control means responsive to said transmit output for deriving an output selectively perceptible to said surgeon.

2. The apparatus of claim 1 in which said finger mount portion includes at leastone externally disposed guideway configured for stabilizing abutting engagement with a said finger of said surgeon next adjacent said select finger.

3. The apparatus of claim 1 in which said finger mount portion is concave and configured substantially as a half-cylindrical surface of curvature selected for nesting against said surgeon's select finger.

4. The apparatus of claim 3, in which:
said finger mount portion extends to two, spaced apart and oppositely disposed strap connector portions; and including a flexible retainer strap connected across said half-cylindrical surface to said strap connector portions and configured for retaining said finger mount portion in slideable engagement against said select finger.

5. The apparatus of claim 1 in which said finger mount portion includes elastomeric retainer means for alternately retaining said finger mount in an operative orientation adjacent an outward portion of said select finger wherein said window is positioned upwardly of the underside of said select finger, and said finger mount being slidably movable to a standby orientation adjacent the inward portion of said select finger wherein said window is positioned outwardly of the upper side of said select finger.

6. The apparatus of claim 1 in which:
said finger mount support region includes a circuit enclosure;
said transmission means includes a first pre-amplification stage mounted within said circuit enclosure, having an input coupled with said crystal detector and responsive to said detector output to derive a first amplified output, a circuit housing located remotely from said finger mount, a second preamplification stage within said circuit housing for deriving said transmit output, and a first cable coupled in electrical communication between said first pre-amplification stage and said second pre-amplification stage.

7. The apparatus of claim 6 in which:
said circuit housing includes a connector for effecting its mounting at the arm of said surgeon remotely from said fingers; and said first cable is of a restricted length selected for extending between said first and second pre-amplification stages in substantial adjacency with said arm.

8. The apparatus of claim 7 including a second cable of length greater than saidfirst cable, coupled between said second preamplifier stage and said control means for conveying said transmit output thereto.

9. The apparatus of claim 6 in which said first preamplification stage comprises:
a charge accumulating network coupled with said crystal detector and deriving a charge responsive voltage signal in response to said detector output; and a first voltage amplifier stage responsive to said charge responsive voltage signal to derive a first amplifier voltage signal, having an output coupled with said first cable, said output exhibiting a low output impedance selected for transmitting said first amplified voltage signal through said first cable.

10. The apparatus of claim 9 in which said second pre-amplification stage comprises:
a second voltage amplifier stage responsive to said first amplified voltage signal, having a first bias point value dependent gain selected to derive a second amplified voltage signal, and first temperature responsive solid-stage means for effecting a stabilization of said first bias point value under conditions of environmental temperature change; and a third voltage amplifier stage responsive to said second amplified voltage signal, having a second bias point value dependent gain selected to effect a predetermined amplification of said second amplified voltage signal, and second temperature responsive solid-state means for effecting a stabilization of said second bias point value under conditions of environmental temperature change.

11. The apparatus of claim 1 in which said crystal detector is a cadmium-zinc-telluride crystal.

12. The apparatus of claim 1 in which:
said crystal detector is a sodium iodide crystal deriving said detector output as scintillations;
said transmission means comprises a fiber optic transmission cable having one end coupled in light transmitting relationship with said crystal detector and extending a predetermined distance to an output end, a housing located removably from said finger mount, a photo-multiplier mounted within said housing having an input coupled in light receiving relationship with said fiber optic transmission cable opposite end and having an output deriving said transmit output.

13. The apparatus of claim 12 in which:
said housing includes a connector for effecting its mounting at the arm of said surgeon remotely from said fingers; and said fiber optic transmission cable is of a restricted length selected for extending between said detector crystal and said housing in substantial adjacency with said arm.

14. The apparatus of claim 13 including a communication cable of length greater than said transmission cable coupled between said photo-multiplier output and said control means for conveying said transmit output thereto.

15. An instrument for detecting and locating sources of radiation emission at predetermined energy levels while within a surgical environment exhibiting temperature variations extending from about room temperature to about 37°C, comprising:
a housing having a forward support region;
a crystal retainer assembly supported by said forward support region;
a cadmium-zinc-telluride crystal having forwardly and rearwardly disposed faces, mounted by said crystal retainer assembly and having said Zn component alloyed with said Cd and Te components in an amount effective to substantially avoid change in the generation of electrical noise by said crystal within said temperature variations, and generating a detector output in response to said radiation emission;
transmission means for applying electrical ground to said crystal forward face and an electrical bias to said crystal rearward face and for conveying and treating said detector output to provide a transmitted output; and control means responsive to said transmitted output for deriving a perceptible output corresponding therewith.

16. The instrument of claim 15 in which said cadmium-zinc-telluride crystal can be represented by the formula: Cd1-x Zn x Te, where the value of x ranges from about 0.2 to about 0.8.

17. The instrument of claim 16 in which said value of x is about 0.2.

18. The instrument of claim 15 in which said transmission means includes a pre-amplifier, comprising:
a charge accumulating network coupled with said crystal and deriving a charge-responsive voltage signal in response to said detector output;
a first voltage amplifier stage responsive to said charge responsive voltage signal to derive a first amplified voltage signal at an output;
a second voltage amplifier stage responsive to said first amplified voltage signal, having a first bias point value dependent gain selected to derive a second amplified voltage signal, and first temperature responsive solid-stage means for effecting a stabilization of said first bias point value under conditions of environmental temperature change; and a third voltage amplifier stage responsive to said second amplified voltage signal, having a second bias point value dependent gain selected to effect a predetermined amplification of said second amplified voltage signal, and second temperature responsive solid-state means for effecting a stabilization of said second bias point value under conditions of environmental temperature change.

19. The instrument of claim 18 in which:
said charge accumulating network and said first voltage amplifier are mounted with said housing;
including a remote circuit housing located remotely from said housing, within which said second and third voltage amplifier stages are mounted;

a first cable of selectively restricted length coupled in electrical communication between said first voltage amplifier stage output and said second voltage amplifier stage;
said first amplifier stage output exhibiting a low output impedance selected fortransmitting said first amplified voltage signal through said first cable; and including a second cable of length greater than said restricted length of said first cable coupled between said remote circuit housing and said control means for conveying said transmitted output thereto.

20. Apparatus for detecting sources of radiation, comprising:
a hand supported housing having a support region;
a crystal retainer positioned at said support region formed of material attenuating said radiation, having a seat and sidewall extending therefrom to a forward opening;
an electrically conductive conformable cushion layer having an outwardly disposed surface and an oppositely disposed inward surface positioned upon said seat;
a cadmium-zinc-telluride detector crystal having an inward surface positioned inabutment against said cushion layer, having a side surface extending to an outward surface facing said opening;
an electrically conductive deformable layer formed of material transmitting saidradiation positioned in compressing abutment over said detector crystal outward surface;
first electrically conductive contact means positioned intermediate said seat and said cushion layer for effecting application of an electrical bias to said detector crystal inward surface through said cushion layer and for conveying radiation induced charge signals therefrom, second electrically conductive contact means positioned over said deformable layer for applying ground potential at said detector crystal outward surface through said deformable layer;
a window through which said radiation is transmissibly mounted upon said housing over said crystal retainer at said support region and spaced from said deformable layer a distance defining an acoustical impedance deriving gap therebetween, and circuit means for applying said electrical bias and establishing said ground andincluding charge accumulating amplification means for receiving and electrically treating said charge signals to provide transmit signals.

21. The apparatus of claim 20 including a layer of electrically insulative elastomeric adhesive intermediate said cushion layer and said seat for positionally retaining said cushion layer and insulating said first electrical contact means from said seat.

22. The apparatus of claim 20 in which said cadmium-zinc-telluride detector crystal can be represented by the formula: Cd1-x Zn x Te, where the value of x ranges from about 0.2 to about 0.8.

23. The apparatus of claim 22 in which said value of x is about 0.2

24. The apparatus of claim 20 in which said detector crystal and said crystal retainer sidewall are configured to provide a gap between said crystal retainer sidewall and said crystal side surface.

25. The apparatus of claim 20 including a retainer insert transmissive of said radiation, positioned over said deformable layer to effect compressible mutual engagement of said deformable layer, said detector crystal and said cushion layer against said seat.

26. The apparatus of claim 20 in which said housing is configured as a finger mount with a finger mount portion located oppositely from said support region, said finger mount portion being configured for slideable positioning and retention upon a portion of a human finger.

27. The apparatus of claim 26 in which said finger mount portion includes elastomeric retainer means for alternately retaining said finger mount in an operative orientation adjacent an outward portion of said finger wherein said window is positioned upwardly of the underside of said finger, and said finger mount being slidably movable to a standby orientation adjacent the inward portion of said finger wherein said window is positioned outwardly of the upper side of said finger.