NL2010055C2

NL2010055C2 - A brachytherapy apparatus.

Info

Publication number: NL2010055C2
Application number: NL2010055A
Authority: NL
Inventors: John Arthur Lapré; Paulus Cornelis Hendrikus Maria Krechting
Original assignee: Nucletron Operations Bv
Priority date: 2012-12-24
Filing date: 2012-12-24
Publication date: 2014-06-25
Also published as: FR2999940A1

Abstract

Apparatus (1) comprises: a projector device for transporting a radioactive source (4b) to a location outside the projector device; and a source (4a) for emitting low energy beta and/or gamma radiation of 20-200 keV, and having a resistance value of 2040-9000 cGy.cm 2>.h -> 1>.

Description

P98431NL00

Title: A brachytherapy apparatus

FIELD OF THE INVENTION

The invention relates to a brachytherapy apparatus.

The invention further relates to a treatment environment.

5

BACKGROUND OF THE INVENTION

In clinical practice brachytherapy applications are gaining importance. In the course of a brachytherapy treatment a radioactive source, usually a gamma emitter, is introduced into a target volume of a patient by means of a suitable 10 conduit, such as a brachytherapy applicator, an interstitial needle, a catheter, or the like. The radioactive source may be introduced manually or using an afterloader device. Generally, the afterloader device is used for providing the radioactive source or sources inside the patient for a given (short) period of time, inside suitable pre-positioned conduits. In such a case, the gamma source may be a 15 high dose rate (HDR) source or a low dose rate (LDR) source. Definitions of the HDR and the LDR sources may be found in the so-called ICRU reports (ICRU-38 and ICRU-58, for example). Alternatively, the sources (seeds) may be provided inside the target volume of the patient for a prolonged time (several hours) or even for permanent dwelling (until the full decay). Such sources may be the low dose 20 rate sources. Usually sources comprising Cobalt-60, Cesium-137 or Iridium-192 are used for brachytherapy.

It is a disadvantage of the contemporary brachytherapy technique that the corresponding procedures have to be carried out inside a radiation-protected 25 room, having walls of considerable thickness in order to substantially absorb radiation emitted by such sources for protecting hospital personnel and other hospital attendants.

2

SUMMARY OF THE INVENTION

It is an object of the invention to provide a novel brachytherapy apparatus which may be operable outside the radiation-protected environment, such as a treatment room, or, using an environment having relaxed radiation 5 protection requirements.

To this end the brachytherapy apparatus comprises an afterloader device operable to transport a radioactive source from an inner volume of the afterloader device to a location outside the afterloader device and a low energy 10 source emitting beta- and/or gamma radiation in the range of 20 - 200 keV, wherein the source has a strength in the range of 2000 - 9000 cGycm2^1. In accordance with the AAPM Radiation Therapy Committee task Group 43, this value is usually measured at a distance, which is large with respect to the lateral dimension of the source. Usually this value is measured at the distance of 1 m from 15 the source.

It is found that it is particularly advantageous to provide an afterloading device with a radioactive source, which has a strength of about 2000 -9000 cGycm2,h-1. Such source may be referred to as a pulse dose rate (PDR) source. 20 A PDR source is a treatment modality which is found to be an excellent alternative for a LDR treatment and has an advantage that substantially no radiation-protected booth is necessary, because the PDR source has a 10 - 20 times less activity than a HDR source.

25 In a preferred embodiment of the apparatus according to an aspect of the invention, the source is selected from the group consisting of: 57Co, 170Tm, 32P, !69Yb, 145Sm, 153 Gd, 195Au, 181 W, 1251, ^Dy.

It is found that these sources are particularly suitable for implementing 30 a low energy PDR source to be used in an afterloader device. 57Co is particularly suitable, because the half life time is about 272 days, which is considerably long for ensuring suitable source delivery logistics. i70Tm has a half-life time of about 128 days, which is found to be sufficient for implementing PDR brachytherapy using 3 low energy sources. 32P has an advantage that this is a beta emitter having a half-life time of about 14 days. Although this half-life time is considerably shorter than that of 57Co and 170Tm, it is found to be practical to provide a low energy beta-emitting radioisotope for brachytherapy applications. For example, endovascular 5 irradiations may be envisaged using a suitable 32P source operable by an afterloader device.

It is found that 169Yb sources are very attractive since they emit photons of intermediate energy (averaged energy of 93 keV) high enough to minimize 10 photoelectric interactions in soft tissue, and at the same time low enough not to require excessive radiation shielding. Because the half-life time of 169 Yb is about 32 days, it may be easily produced and delivered on demand having desirable source strength values, which is advantageous.

15 145Sm source for brachytherapy may be produced by neutron irradiation of 144Sm (96.5% enriched). It’s half-life time is about 340 days, which relaxes source delivery logistics substantially. Decay is by electron capture with 140 K x-rays per 100 disintegrations in the energy region between 38-45 keV, and 13 gamma-rays at 61 keV. 145Sm sources may be encapsulated in Ti tubes, 20 approximately 0.8 mm by 4.5 mm, and may be used for temporary implantation in brain and ocular tumors. The 38-61 keV photons make such sources suitable to be used in environments having relaxed radiation shielding, similar to X-ray examination rooms, while providing a dose distribution from source arrays somewhat more homogeneous than that from 1251. In addition, the 340 days half 25 life of 145Sm permits its use for times significantly longer than that of 1251 having the half-life time of 60 days.

Isotope 153Gd has been also found to be particularly suitable in the apparatus according to the invention due to its relatively long half-life of about 241 30 day. 195Au having the half-life of 186 days is also found suitable for use with the apparatus according to the invention. Sources, formed from 181W, 125I or 159Dy are also advantageous, especially when brachytherapy treatment is envisaged within a 4 treatment environment having minimally shielding, such as or similar to an X-ray treatment room.

In a still further embodiment of the apparatus according to a still 5 further aspect of the invention, the apparatus further comprises a high dose rate (HDR) radioactive source having a strength of about 40000 cGy*cm2-h1.

It is found to be particularly advantageous to provide an afterloading device with a dual radiation mode, that is, a first mode using a low energy PDR 10 source and a second mode using a HDR source. From phantom studies it appeared that supplementing a usual HDR source irradiation using, for example, 192Ir or 137Cs, with a low dose rate source may substantially improve dose distribution in a target area. This may be explained by the fact that low energy radiation delivered by the PDR source supplements the radiation emitted from the HDR source at 15 short distances from the source. Accordingly, it is expected that cold spots or hot spots near the source conduit may effectively be avoided.

In accordance with a still further embodiment of the apparatus according to a further aspect of the invention the low energy source is attached to a 20 first drive cable of the afterloader device and the HDR source is attached to a second drive cable of the afterloader device.

It is found to be particularly advantageous to provide an afterloader-based apparatus, wherein each source is attached to its own dedicated drive cable. 25 However, it will be appreciated that it may also be possible to load a drive wire with a source on demand. The source may be stored in a suitable bunker, if necessary. This may be particularly advantageous for handling the HDR source, in order to reduce the radiation load on a regular hospital dwelling, such as a regular treatment room, which is not provided with radiation protection walls.

In a still further embodiment of the apparatus according to a still further aspect of the invention the apparatus comprises a radiation detector for 30 5 detection which source is being transported outside the afterloader device.

It is found that for a configuration, when the afterloader device is 5 provided with a low energy PDR source and a HDR source, it is particularly advantageous to provide a detector for real-time detection which of the two sources is being actually transported outside the afterloader device. It will be appreciated that provision of the radiation detector may be advantageous not only when both sources are permanently dwelling inside the afterloader device, but also for 10 circumstances when the afterloader device is temporary equipped with two different sources.

It will be appreciated that for increasing accuracy of the source detection, the afterloader device maybe provided with two dedicated detectors, i.e. 15 a first detector for detecting passage of a low energy source and a second detector for detecting passage of the HDR source. However, it may also be possible to select a single detector for discriminating between the sources. For example, the detector may be adapted to determine the energy of the passing source and to provide a feedback on it. In situation, when a first source is a gamma emitter and a second 20 source is a beta emitter, use of two different detectors may be advantageous. Those skilled in the art would readily appreciate which detector or detectors are suitable for accurately discriminating between a low energy PDR source and a HDR source passing to the outside from the afterloader device.

25 The treatment environment according to an aspect of the invention comprises the apparatus as is set forth in the foregoing. In particular, the treatment environment is a treatment room, such as a hospital treatment room. More in particular the treatment environment is a minimally radiation shielded room. It will be appreciated that the apparatus according to claim 1 is suitable for 30 use in a minimally radiation shielded room.

These and other aspects of the invention will be discussed with reference to Figures, wherein like reference numbers refer to like elements. It will 6 be appreciated that the figures are provided for illustrative purposes only and may not be used for limiting the scope of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS 5 Figure 1 presents in a schematic way an embodiment of an apparatus according to an aspect of the invention.

Figure 2 presents in a schematic way a further embodiment of the apparatus according to a further aspect of the invention.

10

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 presents in a schematic way an embodiment of an apparatus 1 according to an aspect of the invention. The apparatus 1 comprises a radiation-protection chamber 2 for storing at least one low energy PDR radioactive source 4a.

15 It will be appreciated that in practice the radioactive source 4a comprises an external capsule enclosing a radioactive material 3. In order to maneuver the radioactive source 4a in and out the afterloader device, it is connected to a drive wire 6a, which may be wound on a reel 5a. The radioactive source may comprise or may consist of 57Co, 170Tm, 1 2 3P, 169Yb, 145Sm,153 Gd,195 Au,181 W, 125 1, 159Dy, which is 20 suitably shaped and encapsulated.

Although the apparatus 1 may operate using a single low energy PDR source 4a, in accordance with an aspect of the invention, the apparatus 1 may further comprise an additional HDR source 4b, which may be connected to a 25 dedicated transport cable 6b wound about a reel 5b. It will be appreciated that although the sources 4a, 4b are schematically depicted in a respective spatial correspondence, any suitable order of mounting the sources 4a, 4b inside the chamber 2 may be envisaged.

When any of the sources 4a, 4b (if present) are transported by the 2 respective transport cables 6a, 6b outside the apparatus 1, the sources pass a 3 transport tube 7 in the remote afterloader, which may be connected to one or more conduits having a proximal end 7, 7’, 7” and a distal end 8, 8’, 8”. The conduits may 7 be fully or partially positioned inside a patient 9. It will be appreciated that any suitable embodiment of the conduit is contemplated, comprising, but not limited to an interstitial needle, a brachytherapy applicator, or a catheter.

5 When the low energy PDR source 4a is used, necessary irradiation to the patient 9 may be achieved during one or more treatment sessions. In an exemplary embodiment the source 4a(or the capsule comprising the radioactive material 3) may have a diameter of at most 2.5 mm, preferably about 0.9 mm, which is found advantageous for minimizing the overall sizes of the conduits and 10 other supplementary equipment. The radioactive source 4a (or the capsule comprising the radioactive material 3) may have a length in the range of about 5 -50 mm.

In case when the apparatus 1 is provided with a dual functionality, i.e. 15 when it comprises the low energy PDR source 4a, such as, for example 57Co, 170Tm, 32p ΐ69γ]3 i45gm 153 Gd;i95 Au,181 W, 125 I, 159Dy and, additionally, a HDR source, such as, for example, is 192Ir or 137Cs, a dual mode irradiation may be enabled. The dual mode irradiation envisages transport of the low energy PDR source along one or more conduits and supplementary transport of the HDR source along one or 20 more conduits. As a result, energy modulation is achieved which has an effect that a more conformal dose distribution with respect to the target volume is provided.

In accordance with a further aspect of the invention, in order to maintain safety, the apparatus 1 is provided with a radiation detector, for 25 detecting an event of a radiation source passing through the connecting tube 7 to the outside of the afterloader device 1. Preferably, especially in the dual mode situation, the radiation detector is arranged to discriminate between the low energy PDR source and the HDR source for providing a feedback to the medical personnel. An embodiment of a suitable radiation detector is briefly discussed with 30 reference to Figure 2.

Figure 2 presents in a schematic way a further embodiment of the apparatus 20 according to a further aspect of the invention. The apparatus 20 8 comprises a low energy PDR source 27, which is connected to a drive cable 26, cooperating with a drive mechanism 25. In addition, the apparatus 20 comprises a HDR source 23, mounted on a separate drive cable 22, cooperating with a drive mechanism 21. Both source may be individually transported using the respective 5 drive cables to the outside of the inner volume 20a of the afterloader device through an exit space 24.

In order to facilitate detection and discrimination of the radiation source passing through the exit space, the afterloader device 20 may be provided 10 with a first radiation detector 27a and a second radiation detector 27b.

In a first embodiment, the first radiation detector 27a is substantially sensitive to only the energy range corresponding to the low energy PDR source 27 (20 - 200 keV) and the second detector 27b is substantially sensitive to the energy 15 range corresponding to the selected HDR source.

In a second embodiment, the first radiation detector 27a is substantially sensitive to only gamma radiation and the second radiation detector 27b is substantially sensitive to beta radiation. This embodiment is found to be 20 particularly useful when sources emitting different radiation types are used.

It will be appreciated that it may also possible to use a single, suitably calibrated detector, for discriminating between the low energy radiation and the HDR radiation as well as between gamma radiation and beta radiation. Those 25 skilled in the art would readily appreciate which type of radiation detectors may be used in this case.

Accordingly, when a radioactive source 27 passes through the exit space 24 a detector generates a signal, which is provided into a processing unit 28. The processing unit may be adapted to generate a suitable feed-back to medical 30 personnel informing them which type of the source is being transported towards the patient. Preferably, the processing unit 28 comprises a logic unit (not shown) which may compare a pre-set tag of the intended source and a tag of the currently transported tag. When two tags match each other, the source may be transported 9 further through the transport tube 29, as is schematically indicated by the arrow R, towards the conduit 30, positioned inside the patient. Should the tags not match, the processing unit may generate an abort signal and the source may be retracted back into the inner volume 20a of the apparatus 20. In this way an 5 overall safety of the procedure may be substantially increased.

While specific embodiments have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus, it will be 10 apparent to one skilled in the art that modifications may be made to the invention as described in the foregoing without departing from the scope of the claims set out below.

Claims

A brachytherapy device comprising: a follow-up device operable to transport a radioactive source from an inner volume of the follow-up device to a location outside the follow-up device; A low energy source which emits beta and / or gamma radiation in the range of 20 - 200 keV, the source having a strength in the range of 2040 - 9000 cGy-cm 2 -h · 1.

The device according to claim 1, wherein the source is selected from the group consisting of 57 Co, 170 TM, 32 P, 169 Yb, 145 SM, 153 Gd,

195 Au, 181 w, 125 I, 159 Dy.

3. The device of claim 1 or 2, further comprising a high dose rate (HDR) radioactive source with a strength of about 40,000 cGycm2, h-i.

The device of claim 3, wherein the high dose rate source is i92Ir or i37Cs.

The device according to claim 3 or 4, wherein the low energy source is connected to a first drive cable of the after-device and the HDR source is connected to a second drive cable of the after-device.

The device of claim 5, further comprising a radiation detector to detect which source is being transported outside of the after-device.

A treatment environment comprising the device according to any one of the preceding claims.

8. The environment according to claim 7, comprising a treatment chamber or a minimum radiation-shielded chamber.