EP2235564A2

EP2235564A2 - Scintigrafic probe

Info

Publication number: EP2235564A2
Application number: EP08859900A
Authority: EP
Inventors: Marco Morelli; Claudio Scarponi; Marco Torelli
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-12-10
Filing date: 2008-12-10
Publication date: 2010-10-06
Also published as: WO2009074959A2; ITRM20070633A1; WO2009074959A3

Abstract

An endocavitary scintigraphic probe, for the detection of a radiation emitted by a radiopharmaceutical, does not requires the presence of wirings and it is therefore provided with a noticeable handiness and comprises a case and a radiation detection system composed by a scintillating crystal coupled with a photomultiplier, wherein inside said case are housed: means for processing the signals of the photomultiplier, converting them in data to be transmitted to a suitable remote processing unit, external to the case; means for the wireless connection between said means for processing the signals and said remote processing unit; means of variable collimation, to modify the width of the measurement cone of the probe; and an autonomous supply system incorporating at least one accumulator.

Description

SCINTIGRAPHIC PROBE

Description

The invention is referred to a scintigraphic probe, particularly an endocavitary scintigraphic probe being used for a radioactivity-guided search of tissue anomalies like tumour masses with various sizes and nature. Such instrument is offered to the surgeon for a precise and selective localization of tumours in patients preliminarily treated with a radioactive substance called radiopharmaceutical. The probe is directly used on the inner tissue of an internal organ of the patient, beforehand incised by the surgeon for the insertion thereof. The detection of the anomalous mass is carried out through the detection of an ionizing radiation, X-rays or gamma rays, emitted by an accumulation of said substance into the examined tissue. Said radiation is emitted, directly or indirectly, by the decay of radioisotopes used for the radiopharmaceutical marking. Therefore, the identification of the tumour site occurs by an analysis of the radioisotope distribution. The used radiopharmaceutical is accumulated into the tumour mass, so acting as a high emission site, easily detectable by a scintigraphic probe.

In the probe, when a ionizing photon interacts with a scintillating crystal, it determines the light emission from the crystal itself. A photomultiplier converts the light signal from the crystal into a measurable electric signal.

The number of photons detected in the time unit is proportional to the concentration of radioisotope into the instrument measurement cone. The identification of high emission sites is carried out through the comparison of the computations executed in real time at the interesting region. The surgeon is informed on the activity of the investigated site both by the direct display of the detected photon number and by a sound indicator frequency modulated proportionally according to the level of the computing itself.

Further examples of endocavitary probes are known in the market, for the detection of photons emitted by radionuclides injected into the patient's body. Often, they are provided with long wires for the connection to the central processing unit and for the electric supply of the electronics in the probe. The presence of such wiring implies an apparent limit for the handiness of the probe. Moreover, the current sterilisation techniques involve frequent working anomalies, just because of the connection wire.

Furthermore, many available probes have architectures based on the coupling of photodiodes with semiconductor detectors, like Cd-Te or Cd-Zn-Te or inorganic crystal as well, like Cs-I(TI). The use of semiconductor detectors assures a good spatial resolution to the instrument, but poor detection sensitivity.

Then, devices are known bases on the scintillating crystal-photomultiplier coupling, having instead simple gamma detectors, apt only to detect the gamma radiation and to amplify the electric signal to the photomultiplier anode. The signal processing is the operated by appropriate processing units, outside the device.

At last, further endocavitary probes are commercially available, apt to vary the collimation thereof. Such operation is carried out through different methodologies, like the replacement of the collimator inside the device and the relative shift of the member housing the collimator with respect to the one housing the crystal.

The technical problem underlying the present invention is to obviate to the drawbacks mentioned with reference to the known art, providing the surgeon with a new instrument, apt to remarkably improve the quality and the effectiveness of the surgical operation. Such a problem is solved by a scintigraphic probe as defined in claim 1.

This probe does not require the presence of any wiring and therefore it has an outstanding handiness.

The present invention will be described hereinafter in connection with a preferred embodiment thereof, provided to a purely exemplificative and non limitative purpose, with reference to the annexed drawings wherein:

• Figure 1 is a side view (a), a top plan view (b) and an axonometric view (c) showing the external casing of a scintigraphic probe according to the invention.

• Figure 2 shows an axonometric view illustrating two sections composing the body of the probe of Figure 1 ;

• Figure 3 shows an exploded axonometric view of the probe of Figure 1 , minutely illustrating the parts composing the probe body;

• Figure 4 shows a sectioned axonometric view illustrating the arrangement of internal components inside the probe body of Figure 1 ;

• Figure 5 shows an exploded axonometric view of the parts composing a removable supply module of the probe of Figure 1 ;

• Figure 6 shows a detailed axonometric view of the hardware of the probe of Figure 1 ;

• Figure 7 shows a block diagram illustrating the internal processing of the signal drawn at the output of a photomultiplier of the probe of Figure 1 ; and

• Figure δ illustrates the operation principle of the variable collimation applied to the probe of Figure 1.

With reference to Figure 1 , a scintigraphic probe has an external case provided with an ergonomic and peculiar shape, elongated according to a main axis and defined by a revolution surface related to said axis, with a cylindrical end section with a reduced diameter, ending with a distal end, and a probe body easily graspable, with a central swelling.

With reference to Figure 2, the probe body (a) is detachable from a removable supply module (b), which can be fastened to said body with a snap device.

With reference to figure 3, the probe body comprises a container of the electronics 1 to which a supply module is connected, provided with a connection element 2. It comprises further a joint ring 3 linking the container of the electronics 1 with the remaining portion of the probe, allowing the rotation of the front portion of the probe with respect to the back portion, thereby assuring the variation of collimation.

At a narrowed portion of the probe, it comprises a container 4 of the scintillating crystal, of the photomultiplier, of the voltage divider and of the preamplifier. It represents the mobile portion, allowing the variation of collimation. Further, joint member 5, 6 are provided, connected, to one part and to the other, to said end section moving, protected by the external case 8 thereof, with respect to the inner patient's organs. On the inner walls of these members, suitable grooves are formed, representing one of the fundamental elements of the variable collimation mechanism. A collimator 7 in tungsten alloy, operating as a screen, is housed in a case 8 at the end of the container 4, in close contact to the bottom thereof. The joint members 5, 6 have in detail helicoidal grooves formed on the inner wall thereof, these grooves make possible the variation of the collimation substantially acting as cam profiles for guiding the movement of the container and of the content thereof, i.e. the mobile portion of the probe, protected by the case 8. To this purpose, the container 4 has pins (not shown) in engagement into said grooves of the joint members 5, 6, just to be able to freely rotate with respect to the ring δ and to the case δ.

With reference to Figure 4, the internal components of the probe are shown in detail: a scintillating crystal 9 which can be of the PbWO₄ type, positioned at the distal end of the probe; a photomultiplier 10, completed with voltage divider, placed immediately close to the crystal 9 in the reduced diameter section; an electronic board constituting means for the management and the processing of the signal produced by the photomultiplier and which is housed in the central portion of the probe body; and a high voltage module 12 for the supply of the photomultiplier.

Figure 5 shows in detail the constituting portions of the removable supply module, particularly a battery case 13 hosting a battery 14 and which, at the bottom thereof, has a release latch flat member 15 provided with holes cooperating with hooks of the probe body. Such supply system can be based on the use of accumulators of different typologies, i.e. accumulators Ni-Cd (Nickel-Cadmium), Ni-MH (Nickel-metallic hydride), Li-ion (Lithium-ion) and Li-Po (Lithium-Polymer).

Preferably, an accumulator Li-ion is used.

Figure 6 instead shows in detail the various components of the above mentioned electronic board 11. It comprises, on a board support, a pre-amplifying unit A, an amplifying unit B, an analogical-digital converter C, a signal processing unit D and a data wireless transmission unit E.

These components hence embody means for processing the signals from the photomultiplier, converting them in data to be transmitted to a suitable remote processing unit, external to the case; and wireless connection means between said means for processing the signals and said remote processing unit.

Figure 7 shows in detail the internal processing method of the signal collected at the anode of the photomultiplier inside the previously described board.

An integrated component A is used for pre-amplifying the output signal from the photomultiplier, which is then amplified by the subsequent integrated component B connected to the module A.

The signal is converted by the integrated component C from analogical to digital. The used sampling is of the variable kind (sample/hold) and it is controlled by a microcontroller system, indicated as module D, where a discrimination function is present, apt to eliminate all the input analogical signals not exceeding a certain threshold value.

Then, a signal processing unit, composed by a micro controller D with a micro software loaded in a flash memory able to carry out time-variable integration functions, (Fast Fourier Transformations) and to compare in real time samples coming from said module C with those loaded in the memory, processes digital signals as result of such a conversion.

After, the unit E arranged for the wireless transmission of data appropriately transmits the data according to a software which will be detailed in the following. The above described wireless transmission means has a transmission bandwidth comprised in the ISM 2.4 GHz band, and modulations GFSK (Gaussian shaped Frequency Shift Keying), DPSK (Differential Phase Shift Keying) or DQPSK (Differential Quadrature Phase Shift Keying) to an external calculator, provided with a suitable software for the management of the received data. Figure 8 shows in its entirety the operation principle of the variable collimation. With reference to Figure 8a, it is illustrated how the variable collimation be obtained thank to a mechanical-kind actuation.

As a matter of fact, the surgeon rotates the front portion of the probe and, according to the entity of the rotation, he achieve a different positioning of the scintillating crystal with respect to the collimator.

With reference to Figure 8, a s a consequence of the rotation visible in the previous Figure, the rotary movement of the front portion of the probe implies the axial movement of the container 4 housing the crystal and the photomultiplier, achieving the variation of the collimation. The variation of the "sight" angle of the sensor helps the surgeon in the definition of the cancer region to be removed.

The transformation of the rotary movement of the lower portion of the probe into the axial movement of the container 4 (Figure 8) is made possible by the simultaneous action of the joint ring 3 (Figure 3) and of the two helicoidal grooves formed on the inner walls of the joint members 5, 6 (Figure 3b). Hence, the variable collimation system for the variation of the measurement cone of the probe itself is composed by a rotating mechanism, so as to vary the relative position of the scintillating crystal (mobile portion of the mechanism) and of the internal collimator (fixed portion of the mechanism), to render maximum the spatial resolution of the probe itself, preferably achieved by moving the scintillating crystal with respect to the collimator, so as to vary the half width of the measurement cone between 20° and 90°.

In general, in the light of what described in the foregoing, in the realization of the probe no limitation is present concerning the usable scintillating crystal: any scintillating crystal appropriately used for the detection of radiations can be used. Particularly, a crystal capable to reveal gamma radiations will be preferred, e.g. belonging to the class of the inorganic scintillating crystals (NaITI, CsI :TI, CaF₂:Eu, Bi₄GeO₄, BaF₂, Y₃AI₅Oi₂Oe, YAIO₃:Ce, Gd₂Si0₅:Ce, CdWO₄, PbWO₄, Nb(WO₄)₂, Lu₃AI₅O₇, Lu₂Si0₅:Ce, ZnWO₄), preferably of the kind PbWO₄. Further, no limitation is present concerning the photomultiplier which can be used: any photomultiplier used for the detection of radiations emitted by the crystal can be used.

For instance, bialkali, multialkali, Sb-Cs and Ga-As photocathode photomultipliers are appropriate. However, in a preferred embodiment of the invention, a bialkali photocathode photomultiplier is used.

From the description of the probe, it is noted the complete absence of cables connected to the device. This innovation is made possible through the simultaneous use of a wireless connection and by a battery supply. The advantages of such solution consist in an improved handiness and in the absence of problem implied in the sterilization, deriving from the presence of the cable itself.

It is provided the possibility to remove the module containing the battery thank to a snap mechanism. This solution prevents any possible damaging of persons and/of things in the device sterilization step and allows an easy recharge of the accumulator.

The removable supply module of the device can be fastened to and removed from the probe body through the operation of a suitable spring system. The accumulator is connected to the supply circuit through suitable electrodes, assuring the electrical connection. The coupling of a scintillating crystal and a photomultiplier allows a sharp improvement of both the sensitiveness and of the spatial resolution of the instrument, advantaging the precision and therefore the quality of the operation.

A clear advantage due to the use of the above described probe is constituted by the processing inside the probe of the signal collected at the anode of the photomultiplier through the use of an innovative electronics.

The signal collected at the anode of the photomultiplier is first amplified up to a level so as to allow the analogical-to-digital conversion thereof. Then, the digitalized signal is processed by a suitable microcontroller, which first compares the received signal with the calibration values pre-charged in a memory and then it carries out various integration operations variable in time and of Fast Fourier Trasformate (FFT). The processed signal is sent to a wireless transmission module, providing to the sending thereof.

The probe is provided with an automatic calibration system through which a clear improvement of the instrument functionality is achieved, advantaging the quality of the operation.

In general, in the making of the probe object of the invention, no limitation is present concerning the selection of the electronic components for the management and the processing of the signal; any electronic component used for the management of signals related to the detection of gamma radiation can be used.

The data processed and transmitted by the probe are managed through the use o fan appropriately developed software, compatible with any kind of operation system, both at 32 and at 64 bit. The software allowing the visualization of the signal processed by the invention is composed by the following functional modules and it has scalable features, so as to allow the introduction of further additional modules according to a astandard. It realizes:

• A user profile management interface; • A functional module for he control of the calibration and of the precision;

• A centering and calibration module for the energetic spectrum;

• A battery-charge state module and management of diagnostic alarms of the probe; • A user interface with time diagram and multi-digit visualization of the real time detected signal and of the computing-by-second, with the possibility of varying, according to the kind of surgical intervention, the integration pitch along the time; • A functional module for the acquisition and real time visualization of the energetic spectrum and the dynamic adjustment of the energetic windows and of the number of counting per second (counting-rate) on a programmable time interval, to simultaneously visualize the spectrum and the position of the energetic windows and thereby obtaining an absolutely precise calibration;

• A statistic management interface for the data with the computation of the standard deviation, the expected value, the probability distribution with non linear data interpolation;

• A control interface for the calibration of the probe with calibration of the energy spectrum of the radioisotope used as a marker;

• A visualization of the Energy spectrum;

• A monitoring system and a remote diagnostic via modem, wireless, radio, Fast Ethernet LAN;

• A management of the clinical data of the patients with the possibility of interlacing with data bases;

• A hold function of the real time marking of one or more historical markers for comparison purposes; hard-copy function of the trend-real time;

• An on line control of two or more different energetic windows;

• A sound emission function (beep) frequency-variable by the counting; • A sound silencer function for the determination of the threshold

(background radiation);

• A statistic processing function of the data for the discrimination of the "background":

• A management of the probe calibration with possibility of calibration by an external sample source; and

• An alarm probe and diagnostic management; management of the main functions, i.e. start, stop, hold, scan through vocal recognition; management of the communication protocols through data bases and loading and processing of data from other formats of other manufacturers.

The internal processing of the signal allows to the probe of transmitting, through wireless connection, easily manageable data from any kind of calculator provided with the above described software, to an external remote processing unit. It can be realized by any kind of calculator and operative system, allowing to limit at the minimum the non-use periods.

The shape of the probe is distinguished by an innovative and functional design, apt to assure to the surgeon the maximum comfort and handiness. The ergonomic profile is particularly important, since the good use of the device is bond to the handiness thereof.

The probe has a shielding system of the scintillating crystal, particularly composed by a tungsten (W) alloy shield, apt to limit at the minimum the negative effects of the background radiation.

The shield mounted inside the invention assures a reliable shielding for photons up to 170 KeV. The use of the probe with more energetic radioisotopes can be carried out with the coupling to a series of additional external collimators, or with a collimator of greater thickness. The internal variable collimation system is able to assure a full adaptability of the device to any of the applications to which it has been designed. The way through which the variation of collimation is carried out is particularly innovative: by the rotation of a portion of the probe is in fact possible to vary the relative position between scintillating crystal (mobile portion) and internal collimator (fixed portion), to optimize the spatial resolution of the instrument.

In general, in the realization of the variable collimation of the probe, no limitation is present concerning the value of the width angles of the measurement cone: any angle can be used and realized. However, a preferred embodiment of the invention uses half-width angles of the measurement cone within 20° and 90°. Further, no limitation is present concerning the materials which can be used: any biocompatible metal, alloy or other, used in biomedical devices is admitted.

Preferably, the components are made of Titanium, Steel and PTFE (Polytetrafluoroethylene).

It is understood that, with respect to that shown in the drawings, the proportions among the parts may vary. The geometrical dimensions can vary within the following ranges: length 20-60 cm, minimum and maximum diameter 1-7 cm. In the present embodiment, the dimension are: length about 30 cm, minimum diameter 1 ,5 cm, maximum diameter about 4 cm. In particular the front end of the probe (reference numeral 8 in Figure 3) can be inclined of an angle comprised between 0° and 90°, preferably 0°.

The probe is specifically designed for all the applications in radioguided surgery, based on the administering of radiopharmaceuticals marked with ^99mTc, ¹²⁵I, ¹¹¹In and ¹⁸F. The applicability of the device is coupled with the currently used pharmaceuticals. Particularly, the probe can be appropriately developed for detecting gamma radiations with an energy within 30 KeV and 1 MeV.

Finally, it is understood that the probe may be associated to any commercial calculator, although provided with the related management software.

To the above described scintigraphic probe a man skilled in the art, to meet further and contingent needs, can introduce several additional variants and changes, however all falling within the protection scope of the present invention, as defined by the annexed claims.

Claims

1. Scintigraphic probe, for the detection of a radiation emitted by a radiopharmaceutical, comprising a case and a radiation detection system composed by a scintillating crystal coupled with a photomultiplier, characterized in that inside said case are housed: a) Means for processing the signals of the photomultiplier, converting them in data to be transmitted to a suitable remote processing unit, external to the case; b) Means for the wireless connection between said means for processing the signals and said remote processing unit; c) Means of variable collimation, to modify the width of the measurement cone of the probe; and d) An autonomous supply system incorporating at least one accumulator.

2. Probe according to claim 1 , wherein the scintillating crystal belongs to the inorganic scintillating crystal class (Nal:TΪ, Csl:TI, CaF2:Eu, Bi₄GeO₄, BaF₂, Y₃AI₅O₁₂ICe, YalO₃:Ce, Gd₂Si0₅:Ce, CdWO₄, PbWO₄, Nb(WO₄)₂, Lu₃AI₅O₇, Lu₂SiO₅:Ce, ZnWO₄), preferably of the PbWO₄ kind.

3. Probe according to claim 1 , wherein the photomultiplier is of the bialkali, multialkali, Sb-Cs, Ga-As photocathode, preferably of the bialkali kind.

4. Probe according to claim 1 , wherein the variable collimation means for the variation of the measurement cone of the probe are composed by a rotating mechanism, capable to vary the relative position of the scintillating crystal on a mobile portion of the mechanism, and of the internal collimator, on a fixed portion of the mechanism, so as to render maximum the spatial resolution of the probe, preferably realized moving the scintillating crystal with respect to the collimator so as to vary the half width angle of the measurement cone between 20° and 90°.

5. Probe according to claim 1 , wherein said wireless connection means has a transmission bandwidth comprised in the ISM 2.4 GHz band, and modulations GFSK (Gaussian shaped Frequency Shift Keying), DPSK (Differential Phase Shift Keying) o DQPSK (Differential Quadrature Phase Shift Keying) for the transmission of data to an external calculator, provided with a suitable software for the management of the received data.

6. Probe according to claim 1 , having an external case provided with an elongated shape according to a main axis and defined by a revolution surface related to said axis, with a cylindrical end section with a reduced diameter, ending with a distal end, and a probe body easily graspable, a removable supply module of the autonomous supply system, being removably fastened to said body by a snap mechanism.

7. Probe according to claim 4, wherein said variable collimation means comprises a joint ring (3) linking the mobile portion of the probe with the fixing portion, allowing the reciprocal rotation thereof, thereby assuring the variation of collimation.

8. Probe according to claim 7, wherein said variable collimation means comprises joint member (5, 6) connected to the mobile portion, having helicoidal grooves formed on the inner wall thereof, acting for guiding the mobile portion, making possible the variation of the collimation.

9. Probe according to claim 1 , wherein said accumulatori s preferably of the kind Li-ion.

10. Probe according to claim 1 , wherein the means for processing the photomultiplier signals comprises a pre-amplifying unit (A), an amplifying unit (B), an analogical-digital converter (C) and a signal processing unit (D).

11. Probe according to claim 10, wherein the signal processing unit comprises a micro controller with a micro software loaded in a flash memory able to carry out time-variable integration functions, (Fast Fourier Transformations) and to compare in real time samples coming from said module C with those loaded in the memory, processes digital signals as result of such a conversion.

12. Probe according to claim 1 , wherein the wireless connection means has a transmission bandwidth comprised in the ISM 2.4 GHz band, and modulations GFSK (Gaussian shaped Frequency Shift Keying), DPSK (Differential Phase Shift Keying) o DQPSK (Differential Quadrature Phase Shift Keying) for the transmission of data to an external calculator, provided with a suitable software for the management of the received data.

13. Probe according to claim 1 , wherein comrising a shielding system of the scintillating crystal, particularly composed by a tungsten (W) alloy shield, apt to limit at the minimum the negative effects of the background radiation, assuring a reliable shielding for photons up to 170 KeV.

14. Probe according to claim 6, wherein the front end of the probe is inclined of an angle comprised between 0° and 90°, preferably 0°.

15. Probe according to claim 1 , wherein the means for processing the signals of the photomultiplier comprises an automatic electronic calibration system of the probe.