WO2014125516A1

WO2014125516A1 - Shielding device for radiation emitted by an electron accelerator

Info

Publication number: WO2014125516A1
Application number: PCT/IT2014/000037
Authority: WO
Inventors: Giuseppe FELICI; Alessia Ciccotelli; Nicola Mangiaracina
Original assignee: Sordina S.P.A.
Priority date: 2013-02-13
Filing date: 2014-02-13
Publication date: 2014-08-21
Also published as: ITVI20130031A1

Abstract

The present invention relates to a shielding device (10), in particular from radiation emitted from an electron accelerator according to a prefixed direction, comprising a frame (1), which is coupled with a main shield (2), arranged substantially parallel to said prefixed direction of emission, said device being characterized by comprising an additional shield (3), arranged substantially transversally with respect to the prefixed direction of emission, said main shield and said additional shield being made of material (s) such that said radiation are shielded. The invention also relates to a set of shielding devices, in particular from radiation emitted from an electron accelerator according to a prefixed direction, comprising at least one shielding device (10).

Description

SHIELDING DEVICE FOR RADIATION EMITTED BY AN ELECTRON ACCELERATOR

The present invention relates to the field of biomedical equipment and more precisely relates to a shielding device, which is able to protect from radiation emitted by an electron accelerator.

It is known that the electron accelerator is used to perform the intra-operative radiotherapy (IORT) , for example when it is necessary to perform a surgical radiotherapy in a patient to whom a malignant neoplasm has been removed.

In order to limit the effects of radiations emitted from the electron accelerator, different technical solutions have been carried out up to now, so as to provide a suitable shielding of said radiations, in particular in order to prevent any spread outside the operating room.

Therefore, shifting protection screens are known; they are moved, at a suitable time, in front of the patient and placed in a suitable position for being connected to the electron accelerator. Then, the operating room is evacuated and from the outside and from a remote position an authorized operator gives a command for starting the electron irradiation; once the electron irradiation is finished, it is possible to remove the mobile protective screens or shields and to conclude the surgical operation. The length of said irradiation is typically not more than two minutes and therefore it does not have a significant impact on the length of the whole surgical operation.

The above technique is used in cancer patients suffering of different malignant neoplasm, especially in the abdomen or in the breast. Moreover, the use of the above equipment is of course reserved for the technical staff of a radiotherapy department.

Data on emissions given by an electron accelerator operating at a maximum energy of lOMeV are submitted in the following.

In particular, determination of the annual workload is equal to (A*B) / (prescription isodose( )), where A is the number of IORT treatments that are annually made (pure number) , B is the prescribed radiation dose [Gy] at a given prescription isodose (percentage) .

If we consider, for example, a treatment of the breast cancer according to the protocol developed by U. Veronesi (see "Intraoperative Electrons", Sem. Rad. One, April 2005, 15(2):76-83, by Roberto Orecchia and Umberto Veronesi) , assuming 200 IORT per year, the prescribed dose is 21Gy at a isodose equal to 90% and the workload W is equal about to 4700Gy/year.

According to the publication Med Phys . N. 37 of March 2010 "Radiation protection measurements around a 12 MeV mobile dedicated IORT accelerator", it is believed that the dose (HT) provided by X-rays at a distance of 1 meter, at 0° and 90°, which is equivalent to an electron beam of 10 MeV given by an applicator having a diameter of 10 cm, is respectively equal to C=130 ± 13 ( Sv/Gy) and D=12.5 ± 1.3 ( Sv/Gy) .

Thus, the annual equivalent dose given at a distance equal to 1 meter is equal to:

Ht (0°) = W*C = 4700Gy/year * 130 pSv/Gy = 6.11 * 10⁵ Sv/year = 6.11 * 10² mSv/year;

Ht (90°) = *D = 4700Gy/year * 12.5 pSv/Gy = 5.875 * 10⁴ Sv/year = 5.875 * 10¹ mSv/year.

Other technical solutions provide for involving screening systems comprising five side screens or shields and a lower beam stopper, in order to have a suitable shielding around the electron beam.

Two of said screens have a screening surface of 60.0 x 60.0 cm² and they have a layer made of steel and having a thickness of 53 mm and a layer made of polycarbonate having a thickness of 20 mm, while the other three screens have a screening surface of 180 cm x 98 cm and they have a layer made of steel having a thickness of 19.5 mm and a layer made of polycarbonate having a thickness of 5 mm.

Each of said screens is mounted on a metal frame with wheels, which allows said screens to move. The final maximum height of the screen is equal to 124.7 cm.

Said screens must be placed as close as possible to the area where electrons interact with the patient and said screens must also be positioned with the layer made of polycarbonate facing the patient, so that the low- energy electrons are stopped by the material having a low atomic number.

The X-rays having higher intensity and energy are produced in the main direction of emission of the electron beam and for this reason a shield or a beam stopper having substantial thickness and density is provided below the area where the electron beam interacts with the patient. The technical features of the beam stopper are given in the following:

- size: 40.0 X 40,0 cm²;

- thickness: 9.0 cm (a layer made of lead) .

As shown in the enclosed figure 10, which is a graph showing the electron radiations spread by an electron accelerator having 5 screens and a lower central beam stopper, a lateral diffusing radiation passes and said radiation hits the floor of the operating room; furthermore, the radiation has a peak in correspondence of a cone formed by an inclined surface having an angle of 45° and having a vertex corresponding with the electron source.

For this reason, the floor of the operating room may require, in some cases, an additional shield; however, this technical solution, although effective, is too cumbersome and it has the drawback of loading the floor with a relevant weight which includes the weights of said shifting screens and of the additional shielding. A main object of the present invention is therefore to provide a solution to the above technical problem, which is able to lighten the loads on the floor of the operating room, while also ensuring a reduction of the electron radiation over the shielding.

Another object of the invention is to provide a shielding device that is able to have a suitable safety level .

Another object of the invention is to provide a shielding device that can be easily moved by an operator.

A further object of the present invention is to provide a system of two or more shielding devices.

These and other objects will be clear from the following description which relates to a shielding device .

These and other objects are also achieved by a shielding device, in particular from radiation emitted from an electron accelerator, according to the attached claim 1; other technical features are included in the subsequent dependent claims.

Advantageously, the shielding device of the invention relates in particular to shielding from radiation emitted from an electron accelerator according to a predefined direction and comprises a frame, which is coupled with a main screen arranged substantially parallel to a prefixed direction of emission, and a further screen, arranged substantially transversely to the prefixed direction of emission; the main screen and the further screen are made of material (s) such as to provide a shielding action of the radiation.

It is thus possible to intercept and then shield the radiation emitted according to a cone having an angle of 45°, which cannot be intercepted by the screens made according to the prior art .

Preferably, according to the invention, said further screen is placed substantially orthogonally with respect to said prefixed direction of emission.

Furthermore, according to the invention, said further screen can be set in different positions along a direction parallel to the prefixed direction of emission, between a first position and a second position, in order to move it towards or away from the source of radiation emitted by the electron accelerator.

According to the invention, rotation means can be provided for connecting the further screen and the frame, so that said further screen can move from a first resting position, according to which it is parallel to the prefixed direction of emission, to a second working position, according to which it is placed at an angle with respect to the prefixed direction of emission, so as to intercept most of the emitted electrons. This advantageously allows to obtain the same overall dimensions of the known devices. A particular object of the present invention is to provide a system of shielding devices, comprising at least one of said screen devices.

Preferably, according to the invention, two pairs of screen devices are provided, which are mutually arranged substantially at an angle of 180°.

It is a further object of the invention a lower shield or beam stopper, which has a frame, to which a main screen is coupled, and a further screen, both placed transversely with respect to the prefixed direction of emission, wherein said further screen is partially superimposed to the main screen, and/or partially protruding outside the overall dimensions of the main screen .

Moreover, according to the invention, the main screen of the shield has a shielding surface with a first and a second dimensions, while said further screen of the shield has a shielding surface having a third dimension, which is parallel to the first dimension, and a fourth dimension, which is parallel to the second dimension; the third dimension may be greater than the first dimension and/or the fourth dimension can be less than the second dimension.

Still according to the invention, said further screen of the shield can be placed in different positions along a direction parallel to the prefixed direction of emission.

The present invention will be described in the following according to preferred embodiments and with reference to the attached figures, in which:

- figure 1 shows a perspective view of a first embodiment comprising three devices according to the invention; - figure 2 shows a first side view of the embodiment of figure 1;

- figure 3 shows a top view of the embodiment of figure 1;

- figure 4 shows a perspective view of the embodiment of figure 1;

- figure 5 shows a second side view of the embodiment of figure 1;

- figure 6 shows a first side view of a further protective device forming the shielding device according to the invention;

- figure 7 shows a second side view of the device of figure 6;

- figure 8 shows a first perspective view of the device of figure 6 ;

- figure 9 shows a second perspective view of the device of figure 6;

- figure 10 is a graph showing the spread of radiation emitted by an electron accelerator.

With particular reference to figures 1-5, according to a first embodiment of the invention, a shielding device 10 has a frame 1, to which is coupled a main shield or screen 2, arranged parallel to the main direction of emission of the electron beam (not shown) , and a further or additional shield or screen 3, arranged according to a transverse orientation with respect to the main direction of emission of the electron beam to be shielded.

"Transverse orientation" means any orientation of a plane which intersects said main direction of emission of the electron beam to be shielded.

In particular, it is extremely effective to provide for an additional shield 3 which is placed according to a direction which is substantially orthogonal with respect to said main direction of emission.

According to the invention, said shield 3 can be fixed according to different positions along the direction indicated by the arrow F, from a higher position A which is closer to the surgical table, to a lower position B, which is farther away from the surgical table, depending on the amount of electrons to be shielded.

According to a preferred embodiment of the invention, it is possible to provide a rotational movement of the additional shield 3 through rotation means (not shown) , such as for example a hinge, which connect a portion of the additional shield 3, preferably an edge, with the frame 1, so that said additional shield 3 can move from a first resting position (not shown) according to which it is parallel to the main direction of emission of electrons (for example, in order to be packed away with the minimum overall dimensions) to a second working position (figures 1-5) according to which it is located at an angle with respect to said main direction, so as to intercept most of the emitted electrons.

Preferably, the frame 1 also provides a moving structure 4 comprising moving means 5, such as for example wheels.

In addition, the moving structure 4 is able to include blocking means 6, which secure said moving means at a given position predefined by the user. Therefore, it is possible to move the device of the invention and to make it firm at a given position, thus preventing further movements .

The device of the invention also comprises gripping means 7, which are provided for picking it and moving it from a first position to a second position, for example from a working position to a resting position. With reference to figures from 1 to 5, according to an embodiment of the structure including the shielding devices of the invention, a shielding device 20 has a frame 21, which is coupled to a main shield 23; the main shield 23 is also placed at an angle (transversely) with respect to the main direction of emission of the electron beam to be shielded.

In particular, a main shield 23 which is placed substantially perpendicular to said main direction is extremely effective.

According to the invention, said main shield 23 can be arranged according to different positions, i.e. from a higher position to a lower position, depending on the amount of electrons to be shielded.

Preferably, the frame 21 also provides a moving structure 24 comprising moving means 25, such as for example wheels.

Furthermore, the moving structure 24 is able to include blocking means 26, which secure said moving means at a given position predefined by the user. Therefore, it is possible to move the device 20 of the invention and secure it at a given location, thus preventing further movements .

With reference to figures from 6 to 9, according to a second embodiment of the invention, the structure of shielding devices of the invention comprises a shielding device 30, which has a frame 31 coupled to a main shield 32, and an additional shield 33, both said shields 32 and 33 being arranged at an angle (transversely) with the main direction of emission of the electron beam to be shielded and the additional shield 33 being partially superimposed on the main shield 32 and partially projecting outside its overall dimensions .

In particular, given two dimensions L and M of the shielding surface of the main shield 32, it has been shown that an additional shield 33 having dimensions 1 and m, such that at least one of the relationships 1>L and/or m_<M is satisfied, is extremely effective. It is thus possible to concentrate the shielding in particularly critical areas, such as the areas near the emission peak, in correspondence of an axis having an angle of 45° with respect to said main direction and passing through the source of electrons.

According to the invention, said shield 33 can be secured at different positions, from a higher position to a lower position, depending on the amount of electrons to be shielded.

Preferably, the frame 31 also provides a moving structure 34 comprising moving means 35, such as for example wheels.

Furthermore, the moving structure 34 is able to include blocking means 36, which secure the moving means at a given location predefined by the user. It is thus possible to move the device 30 of the invention and secure it at a given location, thus preventing further movements .

The devices used in the structure of shielding devices 10, 20 and 30 of the invention are usually made with the same materials used for known devices, but they can also be made with different materials, provided they are suitable to shield the electron beam.

In particular, the additional shield 3, 33 may comprise a multilayer panel having: - a polycarbonate layer having a thickness of 1 cm;

- a lead layer 2 having a thickness of 2 cm;

- a stainless steel layer having a thickness of 0.5 cm. The additional weight for each shielding device of the invention, compared to known devices, is therefore equal to about 55 Kg.

Moreover, if two devices 10 of the invention are not able to cover the total cone, it is possible to provide one additional device 10.

The overall shielding effect is comparable to the effect obtained with the known devices, however the device according to the invention has a minimum weight loading on the floor.

In fact, the object of the invention is to provide a known shielding device with an additional shield 3, 33, which is placed at an angle or substantially perpendicular to the electron beam and which is positioned under the surgical table; said additional shield or barrier, which is composed by said additional shields 3, 33, can be positioned at a shorter distance from the surgical table, with respect to the known beam stopper. Furthermore, according to the invention, by combining two different types of devices 10 and 20 or 10 and 30, it is possible to have a total overlap between the surgical table (not shown) and the additional shields 3, 33 (as shown in the enclosed figures from 1 to 5) .

The additional shields 3, 33 can be moved, if required, upward (figures from 1 to 5, position A) and downward (figure 1, position B) , in order to ensure compliance with a minimum distance from the lower surface of the surgical table.

The technical solution as described above advantageously allows a maximization of the shadow cone with respect to the electron beam, also having a low additional weight.

Finally, it is clear that many other variations may be made to the shielding device of the invention, without departing from the principles of novelty inherent in the inventive idea, as it is clear that materials, shapes and dimensions of the technical features may be any according to requirements and they can be replaced with other technically equivalent, without thereby departing from the scope of protection as defined by the appended claims.

Claims

1. Shielding device (10), in particular from radiation emitted by an electron accelerator along a prefixed direction, comprising a frame (1) , which is coupled with a main shield (2), placed substantially parallel to said prefixed emitting direction, said device being characterized in comprising an additional shield (3) , placed substantially transversal in respect with the prefixed emitting direction, said main shield (2) and said additional shield (3) being made up of material (s) so as to exert a shielding action from said radiation.

2. Shielding device (10) according to claim 1, characterized in that the additional shield (3) is placed substantially orthogonal in respect with said prefixed emitting direction.

3. Shielding device (10), according to claim 1 or 2, characterized in that the additional shield (3) can be fixed in several positions along a direction (F) which is parallel to the prefixed emitting direction, between a first position (A) and a second position (B) , in order to move the additional shield (3) close or away from the source of radiations which are emitted by the electron accelerator.

4. Shielding device (10), according to one of the claims 1-3, characterized in comprising rotating means for the rotating connection between the additional shield (3) and the frame (1) , so that the additional shield (3) can move from a first rest position wherein the additional shield (3) is parallel to the prefixed emitting direction, to a second working position wherein the additional shield (3) is oriented transversally to the prefixed emitting direction, in order to intercept most of the emitted electrons.

5. Set of shielding devices, in particular for shielding from radiation which is emitted from an electron accelerator along a prefixed direction, comprising at least a device according to claims 1-4.

6. Set according to claim 5, characterized in providing two pairs of devices according to claims 1-4, said pairs being placed substantially at 180° each other.

7. Set of shielding devices according to claim 5 or 6, characterized in comprising further a beam stopper (30) at the bottom.

8. Set of shielding devices according to claim 7, characterized in that the beam stopper (30) has a frame (31) , which is coupled with a main shield (32) , and an additional shield (33), both placed transversal in respect to the prefixed emitting direction, wherein the additional shield (33) is partially overlapping on the main shield (32) and/or partially protruding from the whole volume of the main shield (32) .

9. Set of shielding devices according to claim 8, characterized in that the main shield (32) of the beam stopper (30) has a shielding surface having a first dimension (L) and a second dimension (M) , in that the additional shield (33) of the beam stopper (30) has a shielding surface having a third dimension (1) parallel to the first dimension (L) and a fourth dimension (m) parallel to the second dimension (M) , and in that the third dimension (1) is bigger than the first dimension (L) and/or the fourth dimension (m) is smaller than the second dimension (M) .

10. Set of shielding devices according to one of the claims 5-9, characterized in that the additional shield (33) of the beam stopper (30) can be fixed in several positions along a direction parallel to the prefixed emitting direction, between a first position and a second position, in order to move the additional shield (33) of the beam stopper (30) close or away from the source of radiations which are emitted by the electron accelerator .