WO2002000298A1

WO2002000298A1 - Use of temperature sensitive liposomes

Info

Publication number: WO2002000298A1
Application number: PCT/IL2000/000375
Authority: WO
Inventors: Zvi Friedman; David Freundlich; Dov Maor; Yoav Medan
Original assignee: Insightec - Image Guided Treatment, Ltd.
Priority date: 2000-06-28
Filing date: 2000-06-28
Publication date: 2002-01-03
Also published as: AU2000255610A1

Abstract

Apparatus for temperature-monitored heat treatment monitoring, comprising: a radiant heat source adapted for heating of internal body tissue at a location; an imager suitable for providing an image that differentiates between whole and collapsed liposomes, viewing said heated tissue at said location; and a controller that analyses a view of said tissue acquired by said viewer and generates a temperature indicating map of the heated tissue, based on a known temperature-varying collapse characteristic of said liposomes.

Description

USE OF TEMPERATURE SENSITIVE LIPOSOMES FIELD OF THE INVENTION

The present invention relates to the field of therapeutic ultrasound, and especially to treatment and/or monitoring of treatment using temperature-sensitive hposomes. BACKGROUND OF THE INVENTION

Lipid coated gas-filled micro-bubbles (hposomes) are known in the art, being used, for example, for destroying tissue by cavitation, a process in which the liposome is excited by ultrasonic waves until it causes local cavitation. It is well known to using hposomes to deliver cancer-fighting drugs to tumors. "Effect of Drug Exposure Duration and Sequencing on Hyperthermic Potentiation of

Mitomycin-C and Cisplatin", by K. E. Wallner et al, in Cancer Research 47 493-495, January 15, 1987, the disclosure of which is incorporated herein by references, describes in general combined hyperthermia and pharmaceutical treatment for cancer.

"The design and Characterization of Temperature Sensitive Liposomes", by R L Magin and J N Weinstein, in Liposome Technology, ed. G Gregoriadis, pg. 137-155, the disclosure of which is incorporated herein by reference, describes various practical aspects of creating liposomes having desirable temperature characteristics, for example describes temperature sensitive liposomes whose coating undergoes a phase change at a certain temperature, causing the liposome to collapse. NIST standard reference database 34, the disclosure of which is incorporated herein by reference, describes phase transition temperatures for various lipids, such as symmetric saturated and unsaturated glycerophospholipids and sodium salt saturated symmetric phosphatidylglycerol.

"Targeting Chemotherapy using Thermosensitive Liposome", in J Neurosurg Vol. 84, February 1996, pp 180- 184, suggests heating a target volume using RF, so that liposomes collapse only at the target volume, releasing their drug.

"Hyperthermia Induces Doxorubicin Release from Long-Circulating Liposomes and Enhances their Anti-Tumor Efficacy", by S. Ning, et al, in Int. J. radiation Oncology Biol Phys Vol. 29, No. 4 pp. 827-834, 1994, the disclosure of which is incorporated herein by reference, describes a two step heat treatment using ultrasound, in which a first heating step of a target volume assists liposomes in reaching the target volume from the blood stream and a second heating step assists in collapsing the liposomes, which are long duration liposomes

(also known as stealth liposomes, as they stay patent in the body for a long time) and not the above described temperature sensitive phase-change liposomes. "Thermal Damage Assessment of Blood Vessels in a Hamster Skin Flap Model by Florescence Measurement of a Liposome-dye System" by S. Mordon, et al. in Lasers Surg Med 1997; 20(2): 131-41, "Control of Photocoagulation Intensity by Thermo-Induced Release of a Fluorescent Marker Encapsulated in Liposomes: Study of an In Vivo Vascular System", by T Desmettre, et al., in J Fr Ophtalmol 1996;19(11):667-78 and "Fluorescence Measurement of 805 nm Laser Induced Release of 5,6-CF from DSPC Liposomes for Real-time Monitoring of Temperature: an In Vivo Study in Rat Liver Using Indocyanine Green Potentiation", by S. Mordon et al., in Lasers Surg Med 1996;18(3):265-70, the disclosures of which are incorporated herein by reference describe monitoring temperature in tissue (e.g., caused by laser irradiation), by providing dye filled liposomes and examining the distribution of the dye in the tissue, after some of the liposomes are deteriorated by heat, by measuring a fluorescence of the dye.

SUMMARY OF THE INVENTION An aspect of some exemplary embodiments of the invention relates to monitoring a temperature inside a patient, using temperature-sensitive liposomes. In an exemplary embodiment of the invention, a mixture of a plurality of different sets of liposomes is used, each set of liposome having a phase transition at a different temperature. Thus, different liposomes will collapse at different temperatures. Optionally, the liposomes that collapse at different temperatures have different sizes. Alternatively or additionally, others structural distinctions, such as contents or wall thickness differentiate between liposomes that collapse at different temperatures. In one exemplary embodiment, the temperature at a location heated by ultrasound is inversely related to the amplitude of the reflection from the liposomes, since, as the temperature rises, more liposomes are burst. The mixture of liposomes may be selected to provide a discrete temperate scale or a quasi-continuous scale. In a discrete scale the liposome phase transition temperatures are clustered in groups at the temperature scale points of interest. In a continuous scale, the phase transition temperatures are more evenly distributed in the temperature range of interest. In some embodiments of the invention, the temperature scale is continuous in some parts and discrete in others. Optionally, the liposomes are selected to give a temperature resolution of about 1°. In an exemplary embodiment of the invention, ultrasonic waves are used both for imaging the liposomes and, with an increased intensity, for collapsing them. Alternatively or additionally, light is used to detect the liposomes, for example, by detecting a Doppler shift in light reflected from ultrasound-excited liposomes. Although ultrasonic heating is preferred in some embodiments, other heating methods, such as RF, laser and hot-water bath may be used. Typically, a volume to be treated using thermal therapy is surrounded by a volume not to be treated. In an exemplary embodiment of the invention, this surrounding volume is provided with liposomes, so that inadvertent heating of not-to-be-treated volume is signaled by a creation of a non-reflecting volume. Heating in this surrounding volume may be detected automatically or manually.

By selecting liposomes that change phases more slowly in response to temperature changes, a heat-dosage measurement (integrated temperature) can be obtained, alternatively or additionally to a relatively instant temperature measurement.

An aspect of some exemplary embodiments of the invention relates to controlling the release of chemicals in the body, especially pharmaceuticals, by selectively heating temperature sensitive liposomes. In an exemplary embodiment of the invention, the released chemical is one that assists the activity of a second chemical, for example by modifying reaction conditions, such as pH. Alternatively or additionally, the released chemical assists in the absorption of a pharmaceutical. For example, a release of Mannitol opens a blood-brain barrier for a second chemical. Optionally, the second chemical is also provided using temperature sensitive liposomes, although other local and/or systemic delivery systems may be used instead.

In an exemplary embodiment of the invention, the liposomes are designed to collapse and release an enclosed chemical, at a temperature at which the enclosed chemical has a desired effect.

An aspect of some exemplary embodiments of the invention relates to controlling the provision of liposomes and/or a therapeutic chemical to a volume being thermally treated, using the liposomes themselves. As known in the art, when a volume is heated, blood supply to that volume increases. In an exemplary embodiment of the invention, temperature-triggered liposomes are provided enclosing a vasodilator. Thus, when a locality is heated, the liposomes collapse, freeing a chemical which will enhance the inflow of blood over and above that provided by heating alone, and encourage the inflow of blood carried materials, such as additional liposomes (of a same or different type) or of a blood carried therapeutic. The vasodilator may have a local effect and/or a more regional effect, depending on the particular vasodilator chosen. Alternatively, the liposomes may enclose a vasostrictor chemical, to block further inflow of blood (and export of heat and/or therapeutics) from the heated volume. Both types of vascular control chemicals may be provided, for example sequentially, or to be triggered at different temperatures, with, for example, the vasodilator being triggered at a first, lower temperature and the vasostrictor being provided at a second, higher, temperature. An aspect of some exemplary embodiments of the invention relates to providing two- part pharmaceuticals at a locality, by selectively heating the locality, for example when both pharmaceuticals are locally present. In an exemplary embodiment of the invention, the two pharmaceuticals work together. Alternatively, a two step treatment is provided, in which a second step is applied in response to an effect of the first step. Optionally, but not essentially, the effects of the first step are monitored using ultrasonic imaging.

An aspect of some exemplary embodiments of the invention relates to a method of removing a toxic drug from the body, in which temperature-sensitive liposomes containing the pharmaceutical are collapsed at a location in the body at which they do less damage, by heating that location. The tissue at the location may be less sensitive to damage at the location or an antidote to the chemical may be provided thereat.

An aspect of some exemplary embodiments of the invention relates to a method of marking a volume to be treated in which liposomes containing a contrast material are selectively collapsed at desired locations. Thus, a marking of a volume to be treated and/or fiduciary marks or other markings may be generated inside the body, substantially non- invasively. During a procedure, for example open surgery or CT guided radiation therapy, the markings are used to guide the procedure. By using several different contrast materials, various effects, such as marking of zones, can be achieved. In a particular implementation, the contrast material is toxic, for example Gd+3, so localized delivery enables reducing the total amount of toxic material delivered and/or restricting its spatial distribution.

An aspect of some exemplary embodiments of the invention relates to providing a toxic material at limited location, by collapsing liposomes encapsulating the material only at the locality or a vascular bed thereof, using localized heating. In one example, the toxic material is urokinease for clot dissolving, where its release by heating damages a blood vessel significantly less than would its release by cavitation. Other exemplary toxic materials are contrast materials, such as Gd+3.

An aspect of some exemplary embodiments of the invention relates to a method of indicating temperatures for non-ultrasonic type imaging. In an exemplary embodiment of the invention, temperature-sensitive liposomes, which act as a contrast material, for example, as a result of their structure or contents, are provided in the body. As a result of the temperature, the liposomes fail and collapse and their contents dilute, thereby reducing or eliminating the contrast. Exemplary imaging methods for which this method can work, include, US, NM, CT, MRI and/or combinations. An aspect of some exemplary embodiments of the invention relates to a method of calibration of temperature sensitive imaging techniques. Many such imaging techniques provide images whose pixel values are affected by the tissue constituents as well as by the actual temperature. For example, temperature-sensitive MRI sequences are affected to a great degree by the ratio of fat to muscle tissue in the imaged tissue, since different tissue types have different temperature dependent image characteristics. In an exemplary embodiment of the invention, temperature sensitive liposomes are used to determine the true temperature inside the body. This true temperature is used to calibrate an imaging sequence, for example by determining a fat/muscle ratio of that volume and/or for determining a function of phase change as a function of temperature.

An aspect of some exemplary embodiments of the invention relates to a method of targeted therapy. In an exemplary embodiment of the invention, a temperature-sensitive liposome having an affinity for a certain structure, for example by being encapsulated or ligated with a suitable anti-body, is provided in the body. Once it is determined to be located at the locality, the liposome is collapsed using heat, for example ultrasound or RF, so that a therapeutic contents of the liposome is locally released.

There is thus provided in accordance with an exemplary embodiment of the invention, apparatus for temperature-monitored heat treatment monitoring, comprising: a radiant heat source adapted for heating of internal body tissue at a location; an imager suitable for providing an image that differentiates between whole and collapsed liposomes, viewing said heated tissue at said location; and a controller that analyses a view of said tissue acquired by said viewer and generates a temperature indicating map of the heated tissue, based on a known temperature-varying collapse characteristic of said liposomes. Optionally, said radiant heat source comprises an ultrasound source. Alternatively, said radiant heat source is adapted for transcutaneous heating.

In an exemplary embodiment of the invention, said imager is a one dimensional imager. Alternatively, said imager is a two dimensional imager. Alternatively, said imager is a three dimensional imager. Alternatively, said imager is a point imager that generates a scalar image of a single point volume. In an exemplary embodiment of the invention, said imager comprises an ultrasound imager. Optionally, said imager detects waves that are related to transmitted waves by nonlinear response of said liposomes. Alternatively or additionally, said imager comprises a separate ultrasound source from said radiant heat source. Alternatively, said imager uses said radiant heat source as an ultrasound source for imaging. In an exemplary embodiment of the invention, said imager comprises a light source having a wavelength reflected by said liposomes and a Doppler shift optical detector to detect Doppler shifted reflections from said liposomes.

In an exemplary embodiment of the invention, said radiant heat source comprises an RF source. Alternatively or additionally, said temperature indicating map include absolute temperature indications. Alternatively or additionally, the apparatus comprises a display for displaying said map. Alternatively or additionally, the apparatus comprises a heating monitor that determines that a required temperature is reached in a target portion of said location. Alternatively or additionally, the apparatus comprises a danger monitor that determines that a danger temperature is not exceeded in a non-target portion of said location.

Alternatively or additionally, the apparatus comprises a dosage monitor that determines that an integrated temperature dosage is not exceeded in a non-target portion of said location.

In an exemplary embodiment of the invention, said controller modifies an activity of said radiant heat source responsive to said map. Optionally, said activity comprises a spatial localization of the heating. Alternatively or additionally, said activity comprises a heating intensity.

In an exemplary embodiment of the invention, the apparatus comprises a pharmaceutical pump that provides at least one pharmaceutical to a body containing said tissue such that at least some of said pharmaceutical is carried to said location, wherein said controller modifies an activity of said pump responsive to said map.

Optionally, said activity comprises a flow rate.

In an exemplary embodiment of the invention, said liposomes comprises a plurality of liposome sets, each set having a distinct and different collapsing temperature, which different sets are distinguished by said controller. Optionally, at least one of said sets has a collapsing temperature of about 38°. Alternatively or additionally, at least one of said sets has a collapsing temperature of about 42°. Alternatively or additionally, at least one of said sets has a collapsing temperature of about 44°. Alternatively or additionally, said plurality of sets comprises at least three sets. Alternatively or additionally, said plurality of sets comprises at least four sets. In an exemplary embodiment of the invention, said liposomes comprises at least one set of liposomes having a continuous distribution of temperature collapse characteristic over a range of temperatures.

There is also provided in accordance with an exemplary embodiment of the invention, a liposome comprising: a temperature sensitive liposome body; and an encapsulated indirect activity chemical, which chemical comprises at least one of a tissue barrier control agent, a toxic non-optical contrast agent, a clot dissolution agent, a vasostriction control agent or a component of a binary chemical treatment. Optionally, the liposome comprises a chemical therapy agent, whose activity is enhanced by said indirect activity agent.

There is also provided in accordance with an exemplary embodiment of the invention, a method for analyzing images to calibrate a temperature sensitive imaging method, comprising: receiving at least one liposome-showing image of a temperature-sensitive liposome containing tissue; receiving at least one temperature sensitive image of the tissue, using a temperature sensitive imaging method; and analyzing said images to determine a temperature sensitive behavior of said tissue under said temperature sensitive imaging method. Optionally, said liposome based image comprises an ultrasound image. Alternatively or additionally, said liposome based image comprises an MRI image.

In an exemplary embodiment of the invention, said temperature sensitive image is an MRI image. In an exemplary embodiment of the invention, said at least one temperature sensitive image comprises at least two temperature sensitive images taken at different temperature conditions.

In an exemplary embodiment of the invention, said at least one temperature sensitive image comprises at least three temperature sensitive images taken at different temperature conditions.

In an exemplary embodiment of the invention, said at least one liposome image comprises at least two liposome images taken at different temperature conditions.

In an exemplary embodiment of the invention, said at least one liposome image comprises at least three liposome images taken at different temperature conditions. BRIEF DESCRIPTION OF THE DRAWINGS

Particular embodiments of the invention will be described with reference to the following description of some embodiments of the invention, in conjunction with the figures, wherein identical structures, elements or parts which appear in more than one figure are generally labeled with a same or similar number in all the figures in which they appear, in which:

Figs. 1A-1C illustrate a body part to be treated and as viewed prior to and during therapy, in accordance with an exemplary embodiment of the invention; Fig. 2 is a schematic block diagram illustration of an ultrasonic imaging and therapy device, in accordance with an exemplary embodiment of the invention;

Fig. 3 is a graph showing the dependence of a reflection intensity on the temperature, in accordance with some embodiments of the invention;

Figs. 4A and 4B illustrate a temperature sensitive image acquired in an ultrasound modality and in an MRI modality, respectively, in accordance with an exemplary embodiment of the invention;

Fig. 5 is a flowchart of a method of temperature calibration, in accordance with an exemplary embodiment of the invention;

Fig. 6 is a schematic illustration of a therapy for brain lesions, in accordance with an exemplary embodiment of the invention;

Fig. 7 is a flowchart of a method of dual-chemical treatment, in accordance with an exemplary embodiment of the invention;

Fig. 8 illustrates a body tissue marked with a contrast agent, in accordance with an exemplary embodiment of the invention; Fig. 9 illustrates providing urokinease to dissolve a clot, in accordance with an exemplary embodiment of the invention; and

Fig. 10 illustrates a method of blood flow control utilizing liposomes, in accordance with an exemplary embodiment of the invention.

DETAILED DESCRIPTION OF SOME EMBODIMENTS Figs. 1A-1C illustrate a body part 100 to be treated and as viewed prior to and during therapy, in accordance with an exemplary embodiment of the invention. In the particular example used, body part 100 includes a tumor 102 adjacent to healthy tissue 104. Fig. 1A shows body part 100 as it would be viewed, for example using ultrasound imaging, without any particular contrast agent. Body part 100 may be any part of the body, but it may especially be tissues where lesions and small sensitive structures are adjacent, for example the eyes and the brain.

Fig. IB shows the effect of injecting temperature sensitive liposomes so that they reach body part 100. The liposomes may be locally or systemically provided. Typically, tumor 102 will be darker (if gray scale is inversely related to the intensity of reflection or lighter, for some imaging techniques and/or other parameter settings, for example reversing the gain) than other tissue, as it contains more blood vessels and/or liposomes are more likely to lodge in tumor tissue than in healthy tissue, as the blood vessels of tumor tissue are typically somewhat more permeable. In an exemplary embodiment of the invention, the liposomes are gas enclosing liposomes. Exemplary gasses include air, CO2, and perflourocarbons. However, as will be described below, at least some of the enclosed volume may include other chemicals, which may be, for example, gaseous, liquid or solid.

Fig. 1C shows body part 100 during thermal therapy, provided, for example, using ultrasound. Alternatively, other types of heating, such as RF, may be used. As the tissue is heated, the temperature sensitive liposomes collapse. Thus, a volume 108 that has already been heat-treated, is lighter (fewer reflections), as the reflection from tissue is weaker than the reflection from liposomes. Optionally, a mixture of different sets of liposomes is provided, each set collapsing at a different temperature. Generally, the temperature in the tissue is inversely related to the intensity of ultrasound reflection. A volume 106 inside the healthy tissue 104 may also be affected by the heat treatment, for example being a secondary ultrasound focal point or a microwave node location. This heating is undesirable, as it may damage healthy tissue 104. In an exemplary embodiment of the invention, the presence of this heating is detected by viewing volume 106, with viewing parameters such that the image is dependent on the collapse state of the liposomes, thereby indicating the local temperature and/or duration of the temperature application. Optionally, a liposome is selected to have similar dosage/temperature heat-damage characteristics as a human cell of interest, for example, so that it collapses when the tissue is expected to be damaged, or shortly before. Responsive to the detected temperature, the heat-treatment can be modified, for example to move the node, or pause the heating. Optionally, liposomes including a local vessel dilator chemical are provided at the periphery of the heat-treated volume, to assist in heat removal from that peripheral volume. In some types of heat-treatment, the location of the heat source can be changed, thereby spreading inadvertently heated volume 106 over a larger part of healthy tissue 104 and reducing the damage.

It is noted that volume 108, by persisting in its lower reflection intensity, also provides an assurance that all of tumor 102 has been treated. However, it is noted that as time goes by and the tissue cools, new liposomes may enter the tissue and provide a reflection. Optionally, such liposomes are intentionally provided to "regenerate" the liposomes in volume 106, so that the hot-spot detection mechanism can be used again. Alternatively, the rate of regeneration can be used as an indication of heat dosage and/or thermal flow. Optionally, liposomes including vessel constricting (or dilating) chemicals are provided to reduce (or increase) the liposome replacement rate and/or cooling rate.

Fig. 2 is a schematic block diagram illustration of an ultrasonic imaging and therapy device 120, in accordance with an exemplary embodiment of the invention. In an exemplary embodiment of the invention, device 120 includes an ultrasonic transmitter 124 for transmitting waves to body part 100, and an ultrasonic receiver 128 for receiving the reflection of the waves from the tissue and the liposomes. Optionally, the liposomes are imaged separately from the rest of the tissue, for example by receiver 128 being tuned especially to detect non-linear interactions of the transmitted ultrasonic waves and the liposomes. Transmitter 124 may also be used for providing ultrasonic energy to heat body part 100. Alternatively or additionally, a separate ultrasound transmitter (not shown) for heating is provided. In some cases, system 120 monitors and/or controls heating effects of cavitation, however, typically, regular heating effects are desired. Alternatively or additionally, a heater 126, for example an RF heating element, is used to provide the heating, while the ultrasound elements are used to provide feedback on the therapy. Alternatively or additionally, other imaging methods that detect the presence or absence of liposomes may be used, for example MRI and X-RAY CT may be used. When used with some of these imaging modalities, the liposomes may contain a contrast material that is imaged by the imaging method and is concentrated enough only so long as the liposome does not collapse from heating. Alternatively or additionally, the liposome itself is imaged.

In an alternative embodiment of the invention, transmitter 124 and/or receiver 128 include optical transmission and receiving elements. When a liposome is irradiated by ultrasound waves from transmitter 124 or heater 126, light reflected from the liposome is Doppler shifted by the induced vibration of the liposome. In an exemplary embodiment of the invention, 250 nm diameter liposomes (with or without gas filling) are illuminated using 800 nm wavelength infra-red light, for example from a laser source. Other liposome geometries may be selected for other light sources, or vice versa, for example first selecting a light source and then selecting a liposome size to match the light source. In some embodiments of the invention, multiple liposome diameters are provided, so that different liposomes reflect different wavelengths of light. In one exemplary embodiment, different temperature sensitivities are associated with different diameters, so that a tissue temperature can be estimated by a relative signal intensity at different illumination wavelengths.

In an alternative embodiment, at least some of the liposomes include an optical contrast material, such as ICG, which changes its optical properties when released from a liposome (which may contain one solvent environment) into the blood stream (which generally comprises a second solvent environment). In the example of ICG, a shift of an absorption band of several tens of nm is expected when ICG is released from the liposome and comes into contact with albumin. Optionally, a second shift of the absorption spectra is detected when the material is taken up by the cells. Alternatively or additionally, a third shift of the absorption spectra is detected when the ICG is in the presence of a material released from other liposomes, such as anti-cancer drugs. It should be appreciated that other optical contrast materials may be provided, for example materials whose absorption or reflection spectra is changed by a change in pH (between inside and outside the liposome). A signal processor 130 is optionally provided for analyzing the reflections detected by receiver 128. A controller 122 optionally controls device 120, for example synchronizing the transmission and reception of signals.

In an exemplary embodiment of the invention, a display 132 is provided so that a user can view the effect of the therapy (at least on the liposomes) in real-time. Optionally, a user enters the liposome parameters, for example one or more of type(s) of liposomes used, amounts and time(s) of injection. Alternatively or additionally, the display presents either a detected temperature or a liposome degradation display showing the degradation rate and/or the degradation as a function of time. Alternatively or additionally, a watchdog program or hardware 134 is provided, which can generate an alert and/or shut-down the heating if a portion of healthy tissue 104 is inadvertently heated above a described temperature. A user interface 136 is optionally provided for controlling device 120. In an exemplary embodiment, a graphical interface is provided and used to delineate volumes to be heated and/or not to be heated on a display such as that of Fig. IB.

In an exemplary embodiment of the invention, device 120, at least insofar as its hardware, is substantially a standard heat-treatment and/or imaging system. A stored program memory 138, which can be used by controller 122, is optionally provided to provide required functions so that device 120 can operate as described herein. It should be appreciated that in some embodiments of the invention, an ultrasonic image guided heating therapy device may be reprogrammed to be used as device 120, especially with regard to determining temperature based on liposome collapse.

In an exemplary embodiment of the invention, a suitable windowing is used, to allow the different densities of liposomes to be viewed as temperatures. For example, a displayed color may vary as a function of the temperature (inverse intensity of reflection from liposomes). Alternatively or additionally, non-linear effects, such as can be viewed using second harmonic imaging are used to selectively image (and thus display) the liposomes.

Optionally the treatment is manually directed. However, in an alternative exemplary embodiment of the invention, the treatment is automatically directed, for example responsive to echoes from the tumor that indicate that not all the liposomes have collapsed, e.g., that a required temperature has not been reached, a variety of responses may be performed, for example, a heating may be increased, decreased, started or stopped and/or provision of a pharmaceutical from an associated pharmaceutical pump may be increased, decreased and/or the pharmaceutical changed. Optionally, such automatic directing utilizes the ability to image the location of the heat source. Although the treatment is preferably transcutaneous, in some embodiments, the treatment is applied during minimally invasive (e.g., using a heater and/or imager on an endoscope or catheter) or open surgery.

Receiver 128 is preferably adapted to generate a 2D or 3D image, however, in some embodiments of the invention, the receiver only generates a one dimensional image. In some embodiments of the invention receiver 128 generates a scalar value, for example for indicating temperature at a preset or controllable position relative to the receiver.

Fig. 3 is a graph 150 showing the dependence of a reflection intensity on the temperature, in accordance with exemplary embodiments of the invention. Line 152 refers to a situation in which a substantially uniform distribution of temperature sensitivities is used. Thus, as the temperature increases, more liposomes collapse and the reflection intensity goes down. Line 154 refers to a situation in which a non-uniform distribution is used, for example including only liposomes for specific temperatures of interest. Thus, a step-wise response is expected. Generally, the sharpness of the steps depends on the degree of control available during liposome preparation. In the particular example shown a plurality of temperatures are used. However, in a typical application, only one or a small number of thresholds are of interest so fewer sets of liposomes will be provided, increasing the size of step when the threshold is passed and, possibly, increasing the detectability of the step. In an exemplary embodiment of the invention, some non-temperature sensitive liposomes are also provided (or liposomes that are sensitive at significantly higher temperatures), so that even at high temperatures, at least a reference signal from some liposomes can be detected.

Although the temperature monitoring method may be used to monitor heat therapy, it may also be used for temperature measurement for other uses, for example studying heat propagation through the body and for studying blood flow to ischemic and/or damaged tissue. In an exemplary embodiment of the invention, temperature-sensitive liposomes are used to calibrate a different temperature-sensitive imaging method. There are two problems with temperature sensitive imaging methods in general. One problem is setting a base line and gain for the temperature sensitivity. A second problem is correcting for tissue-related effects. Figs. 4A and 4B illustrate a temperature sensitive image of a body part 160 acquired in an ultrasound modality and in an MRI modality, respectively, in accordance with an exemplary embodiment of the invention. Body part 160 comprises, for example a bone 162, a muscle tissue 164 and a fatty tissue 166. Generally, the distinction between tissue types is not binary and a mixture of different tissue types exists in each section of the body. Fig. 4A illustrates an ultrasound image, in which bone is white (as all the waves are reflected from its surface) and both fat and tissue, that incorporate temperature sensitive-liposomes, have substantially a same reflection intensity. This picture is not expected to change as the temperature increases, except that the intensity of reflection from both of tissues 166 and 164 will change by a same amount. Even if the different tissue types absorb different concentrations of liposomes the change in intensity as a function of temperature, in a particular tissue, is optionally significantly less dependent on the tissue type than the changes caused by passing a critical temperature threshold at which liposomes collapse, at which temperature threshold the ratios are optionally determined and the system calibrated. Alternatively or additionally, non-linear interaction of the liposomes with the ultrasonic waves are used to detect them.

Fig. 4B is an image acquired using a temperature sensitive MRI sequence. Such sequences usually detect temperature differences by a phase shift in a detected RF signal, caused by the temperature. However, this phase shift is also affected by the type of tissue imaged. Thus, the picture of Fig. 4B will change, with respect to relative density of tissues 164 and 166, as the temperature changes. Exemplary sequences of temperature-sensitive MRI imaging are described in US patents 5,711,300 and 5,307,812, the disclosures of which are incorporated herein by reference.

Fig. 5 is a flowchart 170 of a method of temperature calibration, in accordance with an exemplary embodiment of the invention. An image using MRI (172) and an image using ultrasound (174) are optionally acquired. The order is not critical, however, in some cases, it may be useful to acquire the MRI image either with the liposomes or without, prompting a particular acquisition order. Also, in some embodiments, an MRI image is used to detect the degree of presence of liposomes. Exemplary images are shown in Figs. 4A and 4B, above. From these two images, it is possible to determine the approximate tissue dependent characteristics (e.g., of phase-temperature relationship). However, in an exemplary embodiment of the invention, the image acquisitions are repeated at a second or even a third temperature (176). Thus, the effects of changes in temperature can be determined and compared. In the ultrasound image the temperature changes are expected not to depend directly on tissue type, only on liposome concentration, while in the MRI image they are expected to also depend on the tissue type. The result can be calibration parameters for the particular body part imaged (178). Alternatively, a determination of fat/muscle ratio for the tissue, or other tissue characteristics, can be made based on the temperature dependencies. It should be noted that a single image can provide a temperature dependency behavior of the tissue, in some embodiments of the invention, for example, if a same tissue is heated in an irregular pattern. Each different temperature location can be utilized as a different image for purposes of calibration.

Alternatively or additionally to imaging the liposomes using ultrasonic imaging, MRI or other imaging techniques may be used. Fig. 6 is a schematic illustration of a therapy for brain lesions, in accordance with an exemplary embodiment of the invention. In a brain 200, a lesion 204 is generally near one or more blood vessels 202. A plurality of therapy- vector carrying liposomes 210 can be provided in vessel 202, however, due to a blood brain barrier, symbolized here by a plurality of pores 208, the liposomes and/or the vector itself cannot enter lesion 204. In an exemplary embodiment of the invention, a plurality of enabling liposomes 206 are also provided. Enabling liposomes 206, encapsulate a material, for example Mannitol or Bradykinin analogs, that causes the blood-brain barrier to open. Same or other chemicals may be used to effect opening of other endothelial tissues and/or blood vessels in other parts of the body.

In an exemplary embodiment of the invention, liposomes 206 are temperature sensitive liposomes that are collapsed by heating the vicinity of lesion 204. It is noted that regular heating, such as using RF or ultrasound may be more desirable than cavitation level ultrasound beams and/or can be better controlled, as they require lower power levels. Additionally, simpler equipment, for example imaging-power-level equipment can be used.

Although the therapy vector is optionally provided using liposomes, alternatively, other provision methods, such as local injection or systemic injection may be used instead.

Alternatively or additionally, the enabling composition and the therapy vector may be encapsulated in a single liposome. Alternatively or additionally, the pharmaceutical(s) used may interact with the temperature, in that they have an optimal effect at a similar temperature to that at which the liposomes collapse. Possibly, both pharmaceuticals are released by heating temperature sensitive liposomes, each one sensitive to a different temperature. Thus, it can be assured that both pharmaceuticals will be released in a desired order or simultaneously (if same type of liposomes).

Alternatively or additionally to binary release of the pharmaceuticals, in an exemplary embodiment of the invention, the local concentration of a phannaceutical may be controlled over time by providing a same pharmaceuticals in a variety of temperature-sensitivity levels and selectively collapsing liposomes to achieve a desired effect. Optionally, a concentration of the pharmaceutical is determined by mixing a contrast material in with the liposomes and differentiating between the signals from the contrast material (which represents the free and encapsulated pharmaceutical and the reflections from the liposomes (which represents only the encapsulated pharmaceutical).

Fig. 7 is a flowchart 220 of a method of dual-chemical treatment, in accordance with an exemplary embodiment of the invention. Both a first and a second drug are provided (222, 226) and released (228, 224) optionally using temperature sensitive liposomes. In various embodiments, the drugs are provided together or in a certain order. The second drug may also be provided only after the first drug is released, possibly after it is removed from the target volume. For example, one drug may be a systemic or a local antidote for the other drug. Alternatively, the drags may be part of a two step treatment. As described above, it may be desirable for the two drugs to be released simultaneously, for example being encapsulated in a same type liposome. This may be useful, for example, for two-part pharmaceuticals or for treatments in which there is a synergetic interaction between the drugs. Alternatively or additionally, simultaneous or consecutive release is useful when one drug enables the other drug to operate, for example by opening tissue or cellular barriers (e.g., Mannitol then a Galanin antagonist for Alzheimer's disease) or by modifying pH or other chemical environment variables. Consecutive release may be achieved, for example, by setting different temperature thresholds or different heat dosages for the collapse of different liposomes.

Once the drugs are released, or between the two releases, an optional step of applying a treatment (230), such as heating, may be performed. In an optional feedback step (232) an assessment of the effect of the total process may be assessed. In another example of a two step treatment, one drug is released at a first location and a second drug at a second location. In a filtration application, temperature-sensitive liposomes are intentionally collapsed at locations where their contents will not cause damage, for example where they will be diluted or where an antidote is present. Thus, a toxic drug can be safely removed from the body, typically after a desired amount was already liberated at a treatment zone.

It should be noted that in some cases the liposomes flow through the volume, for example as a bolus, and the application of heating is optionally timed to the appearance of the bolus. In other cases, the liposomes accumulate in the volume, for example as a result of the lesion, as a result of accumulating all over the body, as a result of attraction to certain tissue types and/or as a result of local injection and/or local control of the blood supply. In this case, the application of heat is optionally started after there is a feedback (e.g., ultrasound reflection) that the liposomes are properly placed. Optionally, the liposome includes, in its coating an agent with an affinity for certain tissue, thus, aiding in the accumulation of liposomes at desired locations.

Fig. 8 illustrates a body tissue 300 marked with a contrast agent, in accordance with an exemplary embodiment of the invention. In an exemplary embodiment of the invention, alternatively or additionally to providing a treatment vector in a liposome, a persisting contrast agent is provided. Once the contrast agent is released (e.g., during heat therapy or during a dedicated marking session), it persists in the locality where it was released, for a significant period of time. This contrast agent is optionally used during therapy of the locality, for example to aid in identifying a lesion and/or to mark sensitive tissues. The type of contrast agent is adapted for the type of therapy and the type of guidance used, for example, adhesive liposomes for ultrasound guided therapy and endoscopes, visible, invisible and florescent dyes for open surgery and optical endoscopes, MRI-contrast agents for MRI and radio-opaque or radioactive materials for X-ray guided and nuclear imaging guided therapies.

In one example, an MRI imaging sequence is used to guide an ultrasound heating-beam so that a lesion 306 is marked (by heating liposomes to release a dye). Thereafter, during open surgery, for example to remove remainders of a tumor, the boundaries of the lesion can be easily seen. Especially in open and endoscopic surgery, it is useful to mark, possibly with a different color, volumes that are healthy and/or volumes that are especially sensitive, such as nerves. Thus, as shown, a marking 310 is used to warn about the presence of a nearby sensitive tissue 308. Alternatively or additionally, the marked volumes can serve as fiduciary marks which guide the navigation and/or other aspect of the procedure. Thus, as shown, a plurality of marks 304 can serve to guide a catheter to tumor 306, in a vascular tree 302. Such guidance is especially important in tissues that change shape periodically or as a result of the therapy, such as the lungs or the brain.

Alternatively or additionally to containing a contrast agent and/or one or more pharmaceuticals, a temperature sensitive liposome may also comprise a second liposome, either temperature-sensitive or not, for example an adhesive liposome which can serve as an ultrasound contrast agent.

Encapsulation and then local release of a contrast agent is also useful if the agent is toxic, for example Gd+3, thus allowing a smaller and/or temporally controlled amount of toxic material to be released in contact with specific body tissues.

Fig. 9 illustrates providing urokinase to dissolve a clot 324, in accordance with an exemplary embodiment of the invention. A clot 324 (complete as shown, or partial) is formed in a vessel 320. A plurality of liposomes 322 encapsulating a clot dissolution material, such as urokinase are provided near clot 324, for example using systemic or local injection or using an endoscope. A heater 328, for example using focused ultrasound heats a volume 326 near clot 324, such that the heated liposomes collapse and release a clot dissolution material.

As only volume 326 is heated, the released material does not damage other portions of blood vessel 320. Alternatively or additionally, the heat intensity is much lower, so the heating itself does not cause considerable damage. It is noted that ultrasound heating in general is less damaging than ultrasound cavitation effects.

The heater may also be a non-focused heater, for example a hot bottle. Alternatively other types of external focus or unfocused heaters may be used. Further, the heater may be on a catheter or needle that provides the liposomes.

It is noted that if clot 324 is not a complete occlusion, blood will flow by it. However, if such flow is low enough and/or the heating is intense enough, the clot dissolution material will be locally released to do its work of dissolving the clot, and when washed away will be replenished from the upstream portions of vessel 320 or from the catheter. In some embodiments, no catheter is used and the liposomes are provided systemically or locally, for example using an injection. Fig. 10 illustrates a method of blood flow control utilizing liposomes, in accordance with an exemplary embodiment of the invention. By encapsulating a chemical that affects vascular dilation and/or other blood-flow parameters, such as viscosity, in a temperature- triggered release liposome, various desirable effects can be achieved, that integrate the blood flow and the therapy being applied. As shown in Fig. 10, a lesion 332 and a sensitive tissue 334 in a body part 300 are both affected by a heater 344, tissue 332 being affected in a desirable manner and tissue 334 in an undesirable manner.

A first type of possibly desirable effect is preferentially providing a chemical or liposomes to tissue 332. A vessel 336 provides blood with liposomes 340 therein to tissue 332. If the liposomes encapsulate a vasodilator, such as lactic acid, acetyl-choline or Bradykinin, when tissue 332 is heated, vessel 336 will provide more blood to tissue 332, bringing the desired chemical and/or liposomes. Thus, more of the chemical will arrive at tissue 332 than at tissue 334. It is noted that also plain heating increases vascular flow, however, by providing chemical signaling molecules, an even further increased flow can be achieved. The vasodilator type may be local (nearby vessels), semi-local or even body wide, in some embodiments. Alternatively or additionally, the released materials may be short term, medium term or long term onset and/or duration vascular control substances. It is noted that some capillaries open only occasionally. Such a vasodilator may be used to force them to open and enhance the penetration of liposomes and therapeutic materials.

Alternatively or additionally, liposomes 340 may include a vessel constricting chemical, for example to compensate for the increased flow brought about by the heat and/or to reduce the outflow of heat and locally (or systemically) released chemicals.

Alternatively or additionally, a vasodilator may be used to protect sensitive tissue 334, by increasing blood supply to tissue 334, thereby increasing heat losses.

As can be appreciated, different types of liposomes may be supplied to different tissues. Alternatively or additionally, a mixture of liposome sets may be supplied, for example to promote a range effect e.g., restricted blood flow up to one temperature threshold and increased flow above it. Alternatively or additionally, the different types of liposomes, therapeutic chemicals and application of heating may be timed to have a desired effect, for example:

(a) providing liposomes that, once heated release a long term vascular constrictor; then

(b) providing liposomes that once heated release a therapeutic chemical; and then

(c) at the sensitive tissue only, providing liposomes that increase blood flow if heated. In some cases, the sensitive tissue is near the treatment volume, so that once the therapeutic chemical is released, a dilator may be released to wash away excess therapeutics.

It will be appreciated that the above described methods of using temperature-sensitive liposomes and the various apparatus described may be varied in many ways. In addition, a multiplicity of various features, both of methods and of devices have been described. It should be appreciated that different features may be combined in different ways. In particular, not all the features shown above in a particular embodiment are necessary in every similar exemplary embodiment of the invention. Further, combinations of the above features are also considered to be within the scope of some exemplary embodiments of the invention. Also included in the scope if the invention are kits of prepared liposomes or liposome raw materials, optionally with usage instructions and/or parameter settings or software modifications for the apparatus. When used in the following claims, the terms "comprises", "includes", "have" and their conjugates mean "including but not limited to".

It will be appreciated by a person skilled in the art that the present invention is not limited by what has thus far been described. Rather, the scope of the present invention is limited only by the following claims.

Claims

1. Apparatus for temperature-monitored heat treatment monitoring, comprising: a radiant heat source adapted for heating of internal body tissue at a location; an imager suitable for providing an image that differentiates between whole and collapsed liposomes, viewing said heated tissue at said location; and a controller that analyses a view of said tissue acquired by said viewer and generates a temperature indicating map of the heated tissue, based on a known temperature-varying collapse characteristic of said liposomes.

2. Apparatus according to claim 1, wherein said radiant heat source comprises an ultrasound source.

3. Apparatus according to claim 1, wherein said radiant heat source is adapted for transcutaneous heating.

4. Apparatus according to claim 2, wherein said imager is a one dimensional imager.

5. Apparatus according to claim 2, wherein said imager is a two dimensional imager.

6. Apparatus according to claim 2, wherein said imager is a three dimensional imager.

7. Apparatus according to claim 2, wherein said imager is a point imager that generates a scalar image of a single point volume.

8. Apparatus according to any of claims 2-7, wherein said imager comprises an ultrasound imager.

9. Apparatus according to claim 8, wherein said imager detects waves that are related to transmitted waves by non-linear response of said liposomes.

10. Apparatus according to any of claims 8-9, wherein said imager comprises a separate ultrasound source from said radiant heat source.

11. Apparatus according to any of claims 8-9, wherein said imager uses said radiant heat source as an ultrasound source for imaging.

12. Apparatus according to claim 1 or claim 2, wherein said imager comprises a light source having a wavelength reflected by said liposomes and a Doppler shift optical detector to detect Doppler shifted reflections from said liposomes.

13. Apparatus according to claim 1, wherein said radiant heat source comprises an RF source.

14. Apparatus according to any of claims 1-13, wherein said temperature indicating map include absolute temperature indications.

15. Apparatus according to any of claims 1-14, comprising a display for displaying said map.

16. Apparatus according to any of claims 1-15, comprising a heating monitor that determines that a required temperature is reached in a target portion of said location.

17. Apparatus according to any of claims 1-16, comprising a danger monitor that determines that a danger temperature is not exceeded in a non-target portion of said location.

18. Apparatus according to any of claims 1-17, comprising a dosage monitor that determines that an integrated temperature dosage is not exceeded in a non-target portion of said location.

19. Apparatus according to any of claims 1-18, wherein said controller modifies an activity of said radiant heat source responsive to said map.

20. Apparatus according to claim 19, wherein said activity comprises a spatial localization of the heating.

21. Apparatus according to claim 19, wherein said activity comprises a heating intensity.

22. Apparatus according to any of claims 1-21, comprising a pharmaceutical pump that provides at least one pharmaceutical to a body containing said tissue such that at least some of said pharmaceutical is carried to said location, wherein said controller modifies an activity of said pump responsive to said map.

23. Apparatus according to claim 22, wherein said activity comprises a flow rate.

24. Apparatus according to any of claims 1-23, wherein said liposomes comprises a plurality of liposome sets, each set having a distinct and different collapsing temperature, which different sets are distinguished by said controller.

25. Apparatus according to claim 24, wherein at least one of said sets has a collapsing temperature of about 38°.

26. Apparatus according to claim 24, wherein at least one of said sets has a collapsing temperature of about 42°.

27. Apparatus according to claim 24, wherein at least one of said sets has a collapsing temperature of about 44°.

28. Apparatus according to any of claims 24-27, wherein said plurality of sets comprises at least three sets.

29. Apparatus according to any of claims 24-26, wherein said plurality of sets comprises at least four sets.

30. Apparatus according to any of claims 1-29, wherein said liposomes comprises at least one set of liposomes having a continuous distribution of temperature collapse characteristic over a range of temperatures.

31. A liposome comprising: a temperature sensitive liposome body; and an encapsulated indirect activity chemical, which chemical comprises at least one of a tissue barrier control agent, a toxic non-optical contrast agent, a clot dissolution agent, a vasostriction control agent or a component of a binary chemical treatment.

32. A liposome according to claim 31, comprising a chemical therapy agent, whose activity is enhanced by said indirect activity agent.

33. A method for analyzing images to calibrate a temperature sensitive imaging method, comprising: receiving at least one liposome-showing image of a temperature-sensitive liposome containing tissue; receiving at least one temperature sensitive image of the tissue, using a temperature sensitive imaging method; and analyzing said images to determine a temperature sensitive behavior of said tissue under said temperature sensitive imaging method.

34. A method according to claim 33, wherein said liposome based image is an ultrasound image.

35. A method according to claim 33, wherein said liposome based image is an MRI image.

36. A method according to claim 33, wherein said temperature sensitive image is an MRI image.

37. A method according to any of claims 33-36, wherein said at least one temperature sensitive image comprises at least two temperature sensitive images taken at different temperature conditions.

38. A method according to any of claims 33-36, wherein said at least one temperature sensitive image comprises at least three temperature sensitive images taken at different temperature conditions.

39. A method according to any of claims 33-36, wherein said at least one liposome image comprises at least two liposome images taken at different temperature conditions.

40. A method according to any of claims 33-36, wherein said at least one liposome image comprises at least three liposome images taken at different temperature conditions.