WO2008059164A1

WO2008059164A1 - Device comprising means for detecting ionizing radiation and optical visualization means

Info

Publication number: WO2008059164A1
Application number: PCT/FR2007/052328
Authority: WO
Inventors: Benoît HAUTEFEUILLE; Olivier Tillement; Claire Billotey; Christophe Dujardin; Marc Janier; Frédéric PRAT; Nicolas Mathieu; Olivier Brosset; Philippe Anfre
Original assignee: Universite Claude Bernard Lyon I; Axess Vision Technology; Hospices Civils De Lyon
Priority date: 2006-11-13
Filing date: 2007-11-13
Publication date: 2008-05-22
Also published as: FR2908283A1; FR2908283B1

Abstract

The subject of the invention is a device equipped with a part that can be inserted into a tubular cavity that comprises: a miniaturized probe for detecting gamma radiation comprising a part that can be inserted into a tubular cavity which comprises at least: one scintillator crystal which emits light in response to ionizing radiation, preferably gamma radiation, and which has a volume of less than 30 mm3, the maximum transverse cross section of the probe being less than 10 mm2, one optical fibre that ensures the collection of at least some of the light emitted by the scintillator material and its transmission to a photoelectric converter, one photoelectric converter to which the crystal is connected via the optical fibre which ensures the collection and transmission of at least some of the light emitted by the scintillator crystal to the photoelectric converter, and optical means for visualizing the cavity, that can be inserted into the latter.

Description

DEVICE COMPRISING MEANS FOR DETECTING IONIZING RADIATION AND OPTICAL VISUALIZATION MEANS

The present invention relates to the technical field of endovascular devices. More specifically, the present invention relates to a device coupling a probe that allows the detection of gamma radiation emitted by certain areas of the cavity and optical means for viewing the cavity.

In nuclear medicine, the detection of cancer by injection of radioactive pharmaceutical products that are preferentially localized in tumors is a largely trivialized technique. The localization and the shape of the tumor can thus be imaged by external gamma camera, with single-photon emission computed tomography (SPECT) and more and more of the PET ("positron emission tomography") type, for example by administering radioisotopes of the type: ¹³¹ I, ¹⁹⁸ Au, ⁹⁹ Tc or ¹⁸ F to patients. However, the sensitivity of existing imaging systems is not always satisfactory. In addition, the allowable doses and the labeling specificities of the radiopharmaceuticals used are limiting parameters, so that it is difficult in practice to achieve resolutions of less than a few millimeters. However, the detection of the smallest possible tumors is essential because an early detection of these allows the soonest to take the necessary treatment measures and thereby improves the prognosis of patients.

Moreover, as part of the regular monitoring of patients at risk, screening diagnoses are often made by endoscopy, usually by simple optical observation. These methods of identification often remain insufficient in the case, for example, of superficial tumors or of an early extension of tumors to lymph nodes.

At the end of the 1970s, small radiation detectors, insertable directly into the body near tumors, were developed for bronchoscopies or surgical operations (H. Barber et al., "Miniature radiation detectors for surgical tumor staging". 32 ACEMB, Denver, CoIo., Oct. 6-10, 1979); H. Barber et al., "Small radiation detectors for bronchoscopic tumor localization", IEEE Transactions on Nuclear Science, Vol. NS-27, No. 1, feb. 1980). Such detectors have the advantage of approaching the source of emission and to increase considerably the number of photons detected. A disadvantage of these detectors, however, appeared very quickly: their size and their high sensitivity to the radioactive continuous background hinders the interpretation of the signal collected. In addition, any local variation in background radioactivity that corresponds to unmarked areas makes the problem even more difficult.

Several proposals were then made to try to reduce these harmful effects related to background noise and to increase the sensitivity at the signal-to-noise ratio.

US Patent 4,595,014 proposes to add to a probe for detecting radioactivity, insertable into the human body, a device for identifying ionizing radiation entering in a preferred direction within the scintillator crystal. In these types of probes, a collimator element of very high density, such as tungsten, is arranged around the crystal, with geometries and assemblies that are often complex. However, the collimator to allow sufficient masking of certain gamma rays, must have a certain thickness and therefore occupy an even larger volume. This thickness must be even greater for more energetic radiation. This is why the collimation of scintillating crystals does not seem to be a sufficient solution, especially in the uses for the detection of high energy gamma.

To solve this problem, it has been proposed to use a plurality of different scintillator crystals each coupled to an optical fiber. No. 5,331,961 proposes to use an endoscopic probe using at least two tandem scintillators, specifically arranged relative to one another and coupled to two optical fibers. The proposed configuration allows better directionality but still requires at least the use of two crystals, two optical fibers, and also requires two photodetectors which are, to obtain a good efficiency, often a high cost. In addition, the useful area per crystal (and therefore the light signal) arriving at each photodetector is divided by two. Therefore, what is gained on the one hand in specificity, in particular to identify the direction of the emitted radiation, is partially lost at the signal-on-noise level collected by each detector. Moreover, this device always provides for associating with at least two scintillator crystals disposed so specific to each other and often on the same front section, which makes a significant minimum section and limits the use in some applications including access to cavities of small sections.

The use of a gamma radioactivity detection probe, which can be inserted into the human or animal body, still remains very marginal and the results in terms of localization performance and signal-to-noise ratio still seem insufficient with the techniques developed, centered on the directional localization of the source of emission.

In addition, the complexity of the systems proposed in the prior art makes them particularly expensive and prevents their sole use. The reuse of such probes makes, therefore, mandatory cleaning and sanitizing probes used between each use.

In addition, the detection carried out using probes used in the prior art, in particular in the documents US 2005/012043 and EP 0788766, does not provide sufficient information to obtain a complete diagnosis. In particular, it is not possible to have precise information on the location of the radioactive zone.

One of the objectives of the invention is therefore to propose a device comprising an insertable part in a tubular cavity which makes it possible at the same time to detect gamma radiation in a cavity and to accurately visualize the cavity. For this, a probe for the detection of gamma radiation is used which is insertable into a tubular cavity of a living being and which offers a high sensitivity of detection and allows a precise location of the radioactive zone, while presenting a low cost cost, allowing one-time use.

In this context, the subject of the invention is a device provided with at least one insertable part in a tubular cavity, which comprises:

a miniaturized gamma radiation detection probe comprising an insertable portion in a tubular cavity which comprises at least:

A scintillator crystal which emits light in response to ionizing radiation, preferably gamma radiation, and which has a volume of less than 30 mm ³ , the maximum transverse cross-section of the probe being less than 10 mm ² , • an optical fiber ensuring the collection of at least a portion of the light emitted by the scintillator material, and its transmission to a photoelectric converter,

a photoelectric converter to which the crystal is connected via the optical fiber which ensures the collection and transmission of at least a portion of the light emitted by the scintillator crystal to the photoelectric converter, and optical display means of the cavity, insertable in the latter.

The following description, with reference to the accompanying drawings, provides a better understanding of the invention.

Figure 1 illustrates an example of an insertable portion of an endoscopic device according to the invention incorporating a part in which are positioned a probe and optical means for viewing the cavity in which they are inserted.

Figure 2 shows the evolution obtained in Example 1 of the number of strokes detected, as a function of the distance in mm between the probe and the source. Figure 3 shows the evolution obtained in Example 2 of the number of strokes detected, as a function of the distance in mm separating the probe from the source.

FIG. 4 is a profile representation of the probe used in example 3, FIG. 5 diagrammatically illustrates the device implemented and FIG. 6 shows the evolution obtained in example 3 of the number of shots detected, depending on the distance in mm between the probe and the source.

Figure 7 schematically illustrates the device implemented and Figure 8 shows the evolution obtained in Example 4 of the number of strokes detected, as a function of time.

Figure 9 shows the evolution obtained in Example 5 of the number of strokes detected, with and without collimator, as a function of the distance in mm separating the probe from the source. Figure 10 shows the evolution obtained in Example 6 of the number of strokes detected, with a probe departure contact or 1 cm from the source, depending on the distance in mm between the probe of the source.

Figure 11 shows the signals obtained in Example 7 according to the different passages at different flow rates C1 to C9.

A device according to the invention comprises, in an insertable part in a tubular cavity of a living being, on the one hand, a detection probe by ionizing radiation and, on the other hand, optical display means, the probe and the optical means being in an insertable configuration in a tubular cavity.

Such a combination makes it possible to have a more complete information of the cavity, the direct visual information provided by the optical viewing means also making it possible to direct the probe towards the zone of interest of the cavity and then to precisely locate the zone of the cavity. 'program. A probe as defined below, because of its miniaturization, will be able to be integrated or inserted as an accessory in different medical or diagnostic devices such as catheters, and in particular multichannel catheters, endoscopes, celioscopy, devices used during surgical procedures. An endoscope traditionally comprises optical means for viewing the cavity in which it is inserted, as well as an operating channel and / or an insertion channel. FIG. 1 illustrates the insertable portion of an endoscopic device incorporating a probe 1 according to the invention comprising an optical fiber 2 equipped at one of its ends with a photoscintillator crystal 3 and means 6 for visualizing the cavity, under the form of an optical fiber, both inserted in the same channel 7 of the endoscope. It is also possible for the probe and the visual display means to be inserted into two different channels present in the insertable part of the device. The other end of the optical fiber 2, constituting the probe, is connected to a photoelectric converter 4. Most often this photoelectric converter 4 is connected by any appropriate means to a user interface 5. The display means may be one or several optical fibers connected to an optoelectronic converter making it possible to obtain an image of the cavity. he is also possible to use a miniaturized camera that will be positioned at the distal end of the endoscope.

At the level of the probe 1, the very small section associated with the flexible form of the optical fiber 2 ensuring the deportation of the signal emitted by the scintillator crystal 3 allows direct use of the probe 1 in the standard endoscopic channels. The optical display means 6 and the gamma radiation detection probe 1 are positioned in an optionally compartmentalized guide tube. The probe may, for example, be introduced directly into the introducer tube or the endoscope operating channel and the scintillating crystal positioned at the distal end of the endoscope. The coupling of the traditional optical detection technique with the probe according to the invention is particularly advantageous. Firstly, the probe makes it possible to detect the radioactive isotopes that accumulate in the tumors and thus makes it possible to confirm the diagnosis obtained by the visual means of visualization, in the case of visible tumors. In addition, the probe can detect tumors present deep tissue and therefore invisible by direct observation. The detection of an ionizing radiation marking, thanks to the probe, offers a significant complementarity to existing optical endoscopic systems: detection of small lesions, detection of non-superficial zones (1 to 5 cm beyond the walls and not accessible in optics) and more generally the detection in "strongly upset" areas where the optical analysis remains delicate ... This technique has a very great potential and a very important field of medical applications, which can evolve and enrich itself with the development of more and more specific probes and / or radiopharmaceuticals. The probe used in the context of the invention will now be described in detail. The probe uses a scintillator crystal that emits light in response to ionizing radiation, preferably gamma radiation, and has a volume less than 30 mm ³ , the maximum transverse cross section of the probe being less than 10 mm ² . Because of the small size of the crystal used, the amount of light captured by the optical fiber is still substantially the same regardless of where the ionizing radiation arrives at the crystal. The very small size and the high efficiency of the crystal offers a high sensitivity of detection and an optimal ratio signal / noise for the detection of lesions at a very early stage. In particular, the probe according to the invention is of shape and size adapted to be inserted into a tubular cavity of a living being, and in particular of man.

This type of miniaturized probe, endo-cavitary type is a tool to help the detection of specific lesions particularly effective. Such a probe is an insertable accessory in an endo-cavitary system existing during endoscopic diagnostic procedures or during videoscopic surgery procedures. Such a probe makes it possible to obtain precise information on the local radioactivity inside a living being. Compared with existing scintillating systems that can be used in vivo, it is proposed to improve the quality of detection by an original approach that does not seek to identify the direction of origin of the intercepted gamma, which was achieved, previously, by collimation. either by use of two different crystals and recombination of the signal, but the distance from the emission zone. Indeed, the inventors have imagined to use the fact that, for a given radioactivity zone, the measurable gamma flux evolves as a function of the solid angle and thus decreases as a function of the inverse of the distance squared with respect to to the zone of emission. Also, by measuring the local radioactivity, we have a very efficient means of localization by simple study of the evolution of the number of photon packets emitted by the scintillating crystal in direct relation with the measurable gamma flux coming from the radioactive zone. .

In the old devices, it was used, conversely, important scintillating crystals, which also often had at least one axis of great length in the direction of the probe, in order to obtain a greater probability of interaction . As a result, the ionizing radiation received at one end of the crystal was in probability very different from the ionizing radiation received at the other end.

In the context of the invention, it is proposed to use a very small scintillator crystal with a volume of less than 30 mm ³ , which behaves, in fact, as a quasi-point crystalline detector, which makes it possible to gain considerably in terms of sensitivity and accuracy on the location of the emission area. According to a preferred embodiment, the crystal has a volume of less than 10 mm ³ , preferably less than 5 mm ³ and preferably less than 1 mm ³ . Of Preferably, in the probe according to the invention, the crystal is not associated with any means of collimation. Nevertheless, in certain cases, especially when the probe is used to detect low energy radiation, the crystal may be equipped with a collimator. Preferably, the crystal used has a maximum length of 5 mm, preferably 1 mm. Advantageously, the crystal has a cross section relative to the longitudinal axis of the optical fiber less than 8 mm ² and preferably less than 1 mm ² . The crystal advantageously has a cylindrical shape, preferably with a section of diameter less than 5 mm and preferably less than 2 mm. It is particularly advantageous to choose a crystal whose shape is such that the ratio of the largest dimension of the crystal passing through its center to the smallest dimension of the crystal passing through its center is less than or equal to 3, preferably less than or equal to at 1.5.

Depending on the desired detection, the geometry, the composition and the spectral and temporal characteristics of the crystal or crystals positioned at the end of the probe will be specifically chosen.

The purpose of the probe according to the invention is to make it possible to precisely locate a small radioactive zone. For this, a translucent scintillating crystal is used: this crystal will absorb ionizing radiation, and in particular gamma and beta, and emit photons in response. Crystal means a monocrystalline or polycrystalline crystal, for example in the form of a coarse grain ceramic. A crystal, depending on its geometry and composition in particular will have a given sensitivity, that is to say, it will allow the detection of a given activity, located at a greater or lesser distance from the probe. The probe must locate the radioactive area.

The radiation absorption power of the crystal is related to the density of the crystal.

In the context of the invention, it is possible to use a fast scintillator, preferably chosen from the families of LSO (Lu ₂ SiO ₅ ) and in particular LSO: Ce (Ce ³⁺ doped Lu ₂ SiO ₅ ), LYSO (Lu ₂ ( _I - _X ) Y _2x SiO ₅ ), (which corresponds to the LSO in which a small amount of lutetium is replaced by yttrium) and also GSO or GYSO (which correspond to LSO and LYSO in which lutetium is replaced by gadolinium) . Such crystals offer good detection sensitivity, combined with a very good conduction, by the optical fiber connected to the crystal, of the light emitted at the emission wavelength of these crystals. One can also use a scintillator crystal of Luag families (LU ₂ Al ₅ O _12), LaBr _3, LACI _3, YAG (Y ₂ Al ₅ O _2), YAP (YAIO ₃₎ all doped with luminescent ions (preferably This ³⁺ , but also Pr ³⁺ , Yb ³⁺ , Eu ³⁺ , Tb ³⁺ or others) or BGO (Bi ₄ Ge ₃ Oi ₂ ) undoped.

According to another embodiment, one can use a scintillator having a density greater than 7, preferably selected from the LuAP families doped Ce ^3+, Ce ³⁺ doped LuYAP, CdWO _4, PbWO ₄ or a monocrystalline or polycrystalline scintillator having a density greater than 7, preferably a density greater than 9, advantageously chosen from the families of sesquioxides LU ₂ O ₃ , Gd ₂ θ ₃ doped with luminescent ions, or tungstates or HfO ₂ .

These crystals, to be scintillators, are doped with a lanthanide or transition metal, preferably cerium at most often less than 5%, preferably less than 1 atomic%. In the case of the compounds CdW04 and PbWO4, non-luminescent is not a dopant but directly an ion of the crystal.

Advantageously, the scintillator crystal (s) will have a decay time of less than 100 ns. It is also advantageous to use a scintillating crystal with a high luminous efficiency, preferably greater than 10,000 photons / MeV.

It is also possible that the probe combines the use of several crystals with different luminescence properties to possibly probe areas at different distances from the probe. In this case a scintillating material with slower decline can be envisaged.

In addition, the marked areas to be detected generally have a low penetration beta (<2mm) and a very penetrating gamma (several cm) radioactivity. According to an advantageous variant of the invention, the crystal is coated on one side by a layer of a scintillator material which emits light in response to beta radiation in a spectral range different from the crystal or with a different temporal response. This layer is fine and preferably has a thickness of less than 100 microns. A combined detection: gamma detection and more distinct beta detection is thus performed, allowing a better location of the radioactive zone.

According to a particular embodiment, the probe may have a protection tip of the crystal vis-à-vis the external light. This tip can for example be HDPE (high density polyethylene). A sheath surrounding the optical fiber connected to the crystal, and thermoformed at its end at the crystal to form the protective tip, may be used. It is also possible that the crystal is partially covered, or not covered, by a reflective coating. Such a coating reflects visible light, and in particular the visible light emitted by the interaction of ionizing radiation with the crystal. Indeed, when a gamma radiation arrives on the crystal and is stopped by the crystal, the crystal emits in response a large amount of visible photons that go in all directions. The photons emitted in the direction of the optical fiber are directly received by the latter. To reorient the other photons emitted in the direction of the optical fiber, it may be provided to cover the surface of the crystal which is not directly connected to the fiber of a reflective coating. The crystal is thus partially covered by a coating that reflects a part of the visible light emitted by the interaction of the ionizing radiation with the crystal, in order to increase the amount of light collected by the optical fiber. Such a coating may, for example, be of a metal mirror type or of a different index to return part of the visible light emitted by the crystal towards the optical fiber side. It is also possible that this coating is also diffusing.

The connection between the crystal and the optical fiber can be done by any appropriate means, for example by bonding with a resin in particular. The optical fiber most often comprises a connection end to a photoelectric converter and is generally surrounded by a protective sheath. The probe itself may be disposable.

It is also possible to provide that at least two optical fibers are connected to one of the faces of the crystal and are, for example, each connected to a different photoelectric converter. This then makes it easier to identify and differentiate the light emitted in response to the detection of beta radiation and the detection part emitted in response to the detection of gamma radiation. The probe is integrated in a device according to the invention which also comprises a photoelectric converter. FIG. 1 illustrates a device comprising a probe 1 according to the invention comprising an optical fiber 2 equipped at one of its ends with a scintillator crystal 3. The probe can be inserted into the tubular cavity and move within it, to detect the presence of any source S of gamma radiation.

The other end of the optical fiber 2 is connected to a photoelectric converter 4. Most often this photoelectric converter 4 is connected by any suitable means to a user interface 5. One end of the optical fiber is connected to the scintillator crystal, the other end to the photoelectric converter. Optical fiber is a means of collecting and transmitting the light emitted by the crystal. The optical fiber may have an inorganic core, for example silica, or a polymer, for example PMMA. The part of the light emitted by the crystal that is collected by the optical fiber is transmitted by the latter to the photoelectric converter which will ensure its conversion into an electrical signal and in particular electric pulses. Advantageously, the coupling between the optical fiber and the crystal ensures the collection of more than 5% of the emitted scintillation photons, and preferably more than 10%. To optimize the collected light, the optical fiber is preferably connected to a face of the crystal according to a connection section and the ratio between the crystal surface on which the fiber is connected and the surface of the connection section is preferably close to 1 and preferably less than or equal to 5. The crystal + optical fiber assembly can be inserted into a sheath made of a material allowing gamma radiation to pass through. Such a sheath may advantageously be HDPE, to ensure easy movement of the probe in the insertable part of the device in which it will be integrated.

Advantageously, the total diameter of the probe section is small enough to enter the working channel of a commercial endoscope and as large as possible to obtain a better sensitivity. In the case of a colescope, the total diameter of the probe will be 2.5 to 3.5 mm and in the case of a gastroscope of 1.8 to 2.5 mm.

The optical fiber is flexible and will therefore be able to circulate and adapt to the shape of the cavity in which it will be inserted. It is possible, depending on the application, to use a fiber of very great length, and in particular of a length greater than or equal to 10 m. The total length of the optical fiber which corresponds substantially to the length of the probe, will advantageously be between 2 and 4 m. The insertable part of the probe will preferably be less than or equal to 2 m. Advantageously, the core of the fiber has a diameter of preferably less than or equal to 1.5 mm and the total fiber (core + cladding) has a diameter preferably of less than 3 mm. According to a preferred embodiment, the entire insertable portion may be curved with a radius of curvature of less than 5 cm, preferably less than 2 cm. To obtain a radius of curvature of less than 1.5 cm with silica-core fibers, several fibers may be coupled to the same crystal. Advantageously, the insertable portion has a cross section (taken transverse to the longitudinal axis of the probe) maximum between 0.1 and 10 mm ² and preferably between 0.2 and 5 mm ² . According to an alternative embodiment of the invention, the probe is equipped with means for positioning the latter within a channel of the insertable part of the device. Such means make it possible in particular to position the probe, so that its end comprising the crystal is directly viewable by means of optical viewing means. According to another variant of the device, it also comprises means for quantifying the gamma radiation received by the crystal, by analyzing the electrical signals emitted by the photoelectric converter. This analysis can, for example be performed by a counting unit. The count rate then reflects the amount of gamma radiation directly related to the distance between the emission radioactive zone and the probe. The device may also include means for calculating the distance between the probe and the detected radioactive zone.

The transmitted light can be converted, before analysis, by a photomultiplier or a photodiode. According to one embodiment, the signal from the photoelectric converter (which can be amplified if necessary) is connected to a discriminator (SCA for "Single Channel Analyzer"). The signal from the discriminator is then sent on a counting scale. In the case of the use of two crystals a slow and a fast, it is possible to duplicate the signal from the photoelectric converter and redirect it to two discriminators. One of the discriminators will have a set threshold for the detection of photons emitted by a "fast" crystal following the absorption of gamma radiation, the other will have a threshold set for the detection of photons resulting from the detection of beta, these last arrivals diluted in time in the case of a slow scintillator.

The probe present in the device according to the invention can be used for the detection of gamma radiation from one of the isotopes chosen from: ⁹⁹ Tc, ¹²³ I, ¹⁸ F or any other isotope emitting gamma photons of higher energy at 50 KeV. The probe according to the invention is also suitable for the detection of high energy ionizing radiation, in particular gamma radiation with energy higher than 300 KeV.

The examples below make it possible to illustrate the probes that can be used in the context of the invention. Example 1

The detector is a rectangular crystal of LYSO: Ce ³⁺ (Fibercryst SAS, France at 0.5% Ce) of dimensions 3 * 1 * 1 mm polished on all sides. The optical fiber is a reference Thorlabs BFH37-800 fiber core 800 mm silica and a numerical aperture of 0.37. The total diameter of the fiber is 1.4 mm. The fiber measures 1 m and is polished at both ends. The crystal is glued on one side of the fiber by a two-component epoxy glue (Géofix from ESCIL) transparent to the light emitted by the crystal. The probe's head is then painted with a white acrylic paint, then the entire probe is painted with a black acrylic paint. The output end of the probe is placed on a Hamamatsu R647 photomultiplier. The signal of the photomultiplier is sent to a preamplifier and a shaping amplifier, then it is recovered on a pulse counter also called shots. The probe is then placed in contact with a radioactive source of ¹³⁷ Cs (662 KeV gamma emitter) of activity 20 KBq. The geometry of the source can be likened to a disk 3 mm in diameter. The probe is then retracted parallel to the axis of the disk in steps of 0.25 mm, the number of measured shots is integrated over a period of one second. Figure 2 shows the evolution of the number of hits detected, in depending on the distance in mm between the probe and the source. This experiment shows that a signal is detected even when the probe is at a distance of more than 1 cm from the source.

Example 2

The detector is a rectangular crystal of LYSO: Ce ³⁺ corresponding to that of Example 1 of dimensions 3 * 1 * 1 mm polished on all sides. The optical fiber is a reference Thorlabs BFH37-800 fiber core 800 mm silica and a numerical aperture of 0.37. The total diameter of the fiber is 1.4 mm. The fiber measures 1 m and is polished at both ends. The crystal is glued on one side of the fiber by a two-component epoxy glue (Géofix from ESCIL) transparent to the light emitted by the crystal. The probe's head is then painted with a white acrylic paint, then the entire probe is painted with a black acrylic paint. The output end of the probe is placed on a hamamatsu photomultiplier R647. The signal of the photomultiplier is sent to a preamplifier and then a shaping amplifier, and is then recovered on a pulse counter. The radioactive source used is a ¹³⁷ Cs (gamma 662 KeV emitter) source of activity 20 KBq. The geometry of the source can be likened to a disk 3 mm in diameter. The probe is moved in front of the source along an axis parallel to the plane of the source and placed 6 mm from it. The axis of the probe is aligned along its axis of translation. This experiment makes it possible to study the variation of the signal detected during the passage of the probe close to the source, but without being in contact with it. Figure 3 shows the evolution of the number of detected shots, as a function of the distance in mm separating the probe from the source. The maximum signal is obtained when the probe is at a distance of between 4 and 6 mm from the source.

Example 3

The detector is a cylindrical crystal 3 of LYSO: Ce ³⁺ (Fibercryst SAS, France at 0.5% Ce) of dimensions 1 mm in height to 1 mm in diameter, polished on all sides. The optical fiber 2 is a Thorlabs reference fiber BFH48-100 with a 1000 mm silica core and a numerical aperture of 0.48. the total diameter of the fiber is 1.4 mm. The fiber measures 1 m and is polished at both ends. The crystal is glued on one side of the fiber by a two-component epoxy glue 8 (Géofix from ESCIL) transparent to the light emitted by the crystal. The head of the probe is then painted with a white acrylic paint, then the entire probe is sheathed with a black heat-shrinkable sheath 9. Figure 4 is a profile representation of the probe used. The output end of the probe is placed on a Hamamatsu R647 photomultiplier. The photomultiplier signal is sent to a Hamamatsu C6465 discriminator, then to a NI USB6008 counter and is recorded by visualization and backup software developed under laboratory labview. The radioactive source used is one liquid source ¹⁸ FDG (511 KeV gamma emitter) placed in a quartz tube. The geometry of the source can be likened to a cylinder 3 mm in diameter and 5 mm in height, the radioactivity is distributed homogeneously in this cylinder. The activity of this source during this test is about 5 MBq. The source tube is introduced into an experimental support 11 for moving the probe in front of the source at an adjustable distance: the source is moved on an axis located at D = 1 cm from the source. Figure 5 schematically illustrates the device implemented. Figure 6 shows a revolution in the number of hits detected, depending on the distance in mm between the probe and the source. This experiment makes it possible to study the variation of signal during the passage in front of the probe and demonstrates that it is possible to locate a radioactive source of the same nature as that used for the medical applications placed at 1 cm of depth.

Example 4: The detector is a cubic crystal of LYSO: Ce ³⁺ (Fibercryst SAS, France at 0.5% Ce) of dimensions 1 * 1 * 1 mm polished on all sides. The optical fiber is a Thorlabs reference fiber BFH48-1000 1000 mm silica core and 0.48 numerical aperture. The total diameter of the fiber is 1.4 mm. The fiber measures 1 m and is polished at both ends. The crystal is glued on one side of the fiber by a two-component epoxy glue (Géofix from ESCIL) transparent to the light emitted by the crystal. The probe head is then painted with a white acrylic paint, and then the entire probe is sheathed with a black heat-shrinkable sheath. The output end of the probe is placed on a Hamamatsu photomultiplier R647. The photomultiplier signal is sent to a C6465 Hamamatsu pulses discriminator, then to a NI USB6008 counter and is recorded by a visualization and backup software developed under Labview in the laboratory. The radioactive sources Si and S ₂ used are liquid ¹⁸ FDG sources (511 KeV gamma emitter) placed in quartz tubes. The geometry of the sources can be likened to cylinders 3 mm in diameter and 5 mm in height, the radioactivity is distributed homogeneously in these cylinders. The activity of these sources during this test is about 5 MBq per source. The source tubes are introduced into an experimental support 11 making it possible to move the probe in front of the sources at an adjustable distance: the sources are displaced on an axis located at D = 1 cm from each of the sources. The two sources Si and S ₂ are placed at the same distance from the axis of movement of the probe, and are spaced from each other by 4 cm. Figure 7 schematically illustrates the device implemented. This experiment makes it possible to see the variation of signal during the passage in front of the sources. Figure 8 shows the evolution of the number of hits detected, as a function of time. This example shows that the probe used is able to differentiate two equivalent sources placed at 1 cm deep and 4 cm apart. This result is particularly interesting for medical applications.

Example 5

The detector is a rectangular crystal of LYSO: Ce ³⁺ corresponding to that of Example 1 of dimensions 3 * 1 * 1 mm polished on all sides. The optical fiber is a reference Thorlabs BFH37-800 fiber core 800 mm silica and a numerical aperture of 0.37. The total diameter of the fiber is 1.4 mm. The fiber measures 1 m and is polished at both ends. The crystal is glued on one side of the fiber by a two-component epoxy glue (Géofix from ESCIL) transparent to the light emitted by the crystal. The probe's head is then painted with a white acrylic paint, then the entire probe is painted with a black acrylic paint. The source is a ²⁴¹ Am source of 395 KBq (60 keV gamma emitter). The output end of the probe is placed on a Hamamatsu R647 photomultiplier. The photomultiplier signal is sent to a preamplifier and then a shaping amplifier, and then recovered on a pulse counter. The geometry of the source can be likened to a disk 3 mm in diameter. The probe is moved towards the source along an axis parallel to the plane of the source and placed 10 mm away from it. The axis of the probe is aligned perpendicular to its axis of translation (the probe "looks" towards the source). The probe is placed in a metal tube dense enough to stop the majority of penetrating gamma rays: it acts as a collimator. The measurement is performed with and without the collimator. Figure 9 shows the evolution of the number of detected shots, with and without collimator, as a function of the distance in mm between the probe and the source. This experiment shows that on the one hand a device according to the invention is capable of detecting a source of ²⁴¹ Am and that on the other hand a suitable collimator makes it possible to bring out a signal when the variation of the signal is strongly spread.

Example 6: The detector is a rectangular crystal of LYSO: Ce ³⁺ corresponding to that of Example 1 of dimensions 3 * 1 * 1 mm polished on all sides. The optical fiber is a reference Thorlabs BFH37-800 fiber core 800 mm silica and a numerical aperture of 0.37. The total diameter of the fiber is 1.4 mm. The fiber measures Im and is polished at both ends. The crystal is glued on one side of the fiber by a two-component epoxy glue (Géofix from ESCIL) transparent to the light emitted by the crystal. The probe's head is then painted with a white acrylic paint, then the entire probe is painted with a black acrylic paint. The radioactivity source is a ¹³⁷ Cs source of 373 KBq (gamma emitter at 662KeV). The output end of the probe is placed on a hamamatsu photomultiplier R647. The signal of the photomultiplier is sent to a preamplifier and then a shaping amplifier, and is then recovered on a pulse counter. The geometry of the source can be likened to a disk 3 mm in diameter. The probe is moved towards the source along an axis parallel to the plane of the source: in a first case, it is initially placed in contact with the probe and then moved away gradually and in a second case, it is placed initially at 1 cm from that -this. The axis of the probe is aligned perpendicular to its axis of translation (the probe "looks" towards the source). Figure 10 shows the evolution of the number of hits detected, with a probe leaving the contact or 1 cm from the source, depending on the distance in mm between the probe and the source. This experiment demonstrates that a device according to the invention is capable of detecting a source of ¹³⁷ Cs, and this all the more precisely as the probe will be close to the source.

[Example 7:

The detector is a cubic crystal of LYSO: Ce ³⁺ (Fibercryst SAS, France at 0.5% Ce) of dimensions 1 * 1 * 1 mm polished on all sides. The optical fiber is a Thorlabs reference fiber BFH48-1000 1000 mm silica core and 0.48 numerical aperture. The total diameter of the fiber is 1.4 mm. The fiber measures 1 m and is polished at both ends. The crystal is glued on one side of the fiber by a two-component epoxy glue (Géofix from ESCIL) transparent to the light emitted by the crystal. The probe head is then painted with a white acrylic paint, and then the entire probe is sheathed with a black heat-shrinkable sheath. The output end of the probe is placed on a Hamamatsu R647 photomultiplier. The photomultiplier signal is sent to a C6465 Hamamatsu pulses discriminator, then to a NI USB6008 counter and is recorded by a visualization and backup software developed under Labview in the laboratory. The source used is a gas / metastable Krypton gas mixture ( ⁸¹¹⁷¹ Kr gamma emitter at 190 KeV). The marked gas is injected into a pipe where it circulates at a speed that is varied. Figure 11 shows the signals obtained according to the different passages at different flow rates C1 to C9. This experiment makes it possible to show that the device used is capable of detecting a source ^81m Kr in a sufficiently effective manner so that the device can be adjusted so as to count a large part of the rays stopped by the scintillator crystal while not emitting any false blow of "electronic noise".

Claims

1 - Device comprising:

A scintillating crystal which emits light in response to ionizing radiation, preferably gamma radiation, and which has a volume of less than 30 mm ³ , the maximum transverse cross section of the probe being less than 10 mm ² ,

An optical fiber ensuring the collection of at least a portion of the light emitted by the scintillator material, and its transmission to a photoelectric converter, a photoelectric converter to which the crystal is connected via the optical fiber which carries out the collection and transmitting at least a portion of the light emitted by the scintillator crystal to the photoelectric converter, and

optical means for viewing the cavity, insertable in the latter. 2 - Device according to claim 1 characterized in that the crystal has a maximum length of 5 mm, preferably lmm.

3 - Device according to one of the preceding claims characterized in that the insertable portion has a maximum transverse cross section of between 0.1 and 10 mm ² and preferably between 0.2 and 5 mm ² . 4 - Device according to one of the preceding claims characterized in that the crystal emits more than 10,000 Photons / Mev.

5 - Device according to one of the preceding claims characterized in that the crystal has a decay time less than 100 ns.

6 - Device according to one of the preceding claims characterized in that the crystal is a fast scintillator, preferably selected from the families of LSO,

LYSO, GSO, GYSO, LuAG, LaBr ₃ , LaCI ₃ , YAG, YAP doped with luminescent ions, preferably trivalent cerium. 7 - Device according to one of claims 1 to 5 characterized in that the crystal is a scintillator having a density greater than 7, preferably selected from families LuAP, LuYAP, CdWO ₄ , PbWO ₄ (doped or not with ions) luminescent). 8 - Device according to one of claims 1 to 5 characterized in that the crystal is composed of a monocrystalline scintillator or polycrystalline having a density greater than 7, preferably a density greater than 9, preferably selected from LU sesquioxide families ₂ O ₃ , Gd ₂ θ ₃ , or tungstates or hafnate, for example HfO ₂ . 9 - Device according to one of the preceding claims characterized in that the crystal has a cylindrical shape with a diameter of less than 5 mm and preferably less than 2 mm.

10 - Device according to one of the preceding claims characterized in that the crystal has a volume less than 5 mm ³ and preferably less than 1 mm ³ . 11 - Device according to one of the preceding claims characterized in that the optical fiber is connected to a crystal face according to a connecting section and the ratio between the crystal surface on which the fiber is connected and the surface of the section of connection is less than or equal to 5 and preferably close to 1. 12 - Device according to one of the preceding claims characterized in that the crystal is coated on one side by a layer of a scintillator material which emits light in response to beta radiation in a spectral range different from the crystal and that is preferably less than 100 microns thick. 13 - Device according to one of the preceding claims characterized in that it comprises at least two scintillator crystals, the total volume of all scintillator crystals used remaining less than 30 mm ³ .

14 - Device according to claim 13 characterized in that the crystals used have different spectral or temporal luminescence properties.

15 - Device according to one of claims 1 to 14 characterized in that the coupling between the optical fiber and the crystal ensures the collection of more than 5% of scintillation photons emitted per event, and preferably more than 10%. 16 - Device according to one of claims 1 to 15 characterized in that at least two optical fibers are connected to one of the faces of the crystal and are, for example, each connected to a different photoelectric converter.

17 - Device according to one of claims 1 to 16 characterized in that the entire insertable portion can be curved with a radius of curvature less than 5 cm and preferably less than 2 cm.

18 - Device according to one of claims 1 to 17 characterized in that a plurality of optical fibers are coupled to the same crystal and that the insertable portion can be bent with a radius of curvature less than 1.5 cm. 19 - Device according to one of claims 1 to 18 characterized in that it has a protective tip of the crystal vis-à-vis the outer light.

20 - Device according to one of claims 1 to 19 characterized in that the crystal is covered in part by a coating reflecting a portion of the visible light emitted by the interaction of ionizing radiation with the crystal, to increase the amount of light collected by the optical fiber.

21 - Device according to one of claims 1 to 20 characterized in that it further comprises means for quantifying the gamma radiation received by the crystal, by analyzing the electrical signals emitted by the photoelectric converter. 22 - Device according to one of claims 1 or 21 characterized in that it further comprises means for counting the light transmitted by the optical fiber.

23 - Device according to one of claims 1 to 22 characterized in that the optical display means are one or more optical fibers or a miniaturized camera.

24 - Device according to one of claims 1 to 23 characterized in that the optical display means and the gamma radiation detection probe are positioned in a possibly compartmentalized guide tube.

25 - Device according to one ofdes claims 1 to 24 characterized in that the optical fiber has a polymer core, preferably PMMA.

26 - Use of a device according to one of claims 1 to 25 for the detection of gamma radiation from an isotope chosen from: ⁹⁹ Tc,

123 _T ±, 18c r. 27 - Use of a device according to one of claims 1 to 25 for the detection of high energy ionizing radiation, in particular gamma radiation energy greater than 300 KeV.

28 - Medical or diagnostic device characterized in that it comprises a device according to one of claims 1 to 25 selected from:

catheters, and in particular multichannel catheters

- endoscopes and endoscopes of a form suitable for diagnosis in urology, of a form suitable for diagnosis in colonoscopy, of a form suitable for diagnosis in gastroenterology, or of a form suitable for diagnosis in ENT, - instruments of celioscopy,

- devices used during laparoscopic surgery, surgical procedures in urology, surgical procedures in arthroscopy, or surgical procedures using rigid optics, particularly using stainless steel tubes.