Device for shaping an electron beam of a machine for intraoperative radiation therapy

1. Electron beam shaping device suitable for a machine for intraoperative radiation therapy (IORT—Intra Operative Radiation Therapy), said machine comprising a mobile unit, provided with a linear accelerator having an electrons radiating head, and an operating control rack, which are wired connected to each other, said shaping device including a circular applicator, comprising a cylindrical tube and having a duct through which the electron beam is transmitted, which is rigidly attached to said radiating head and which includes a proximal element, that is attached to said radiating head, and a distal element ( 3 ), that is placed in contact with the area to radiate and that is attached to said proximal element, the shaping device being characterised in that it comprises:

a slab ( 1 ), which is removably attached to said distal element ( 3 ) and which is provided with a hole ( 2 ) corresponding to the duct of the circular applicator,

at least two planar elements ( 10 ), whereby each planar element ( 10 ) comprises two overlapping plates ( 11 , 12 ) which are attached to each other through first mechanical coupling means ( 13 ) and whereby each planar element ( 10 ) is attached to said slab ( 1 ) in a variable position with continuity as a function of the attachment position of said first mechanical coupling means ( 13 ) and of second mechanical coupling means ( 14 ),

said at least two planar elements ( 10 ) being reciprocally arranged so as to be adjacent to each other and each planar element ( 10 ) sliding with respect to another adjacent planar element ( 10 ) through mechanical guide and slide means ( 12 C, 12 D), whereby the reciprocal arrangement of said at least two planar elements ( 10 ) is adjustable so as to define an aperture ( 20 ) of lower area than that of the section of the duct of said circular applicator,

said two overlapping plates ( 11 , 12 ) being made of different materials, so that a first plate ( 11 ) is made of a first sterilisable material with a first atomic number and a second plate ( 12 ) is made of a second sterilisable material with a second atomic number larger than the first atomic number, whereby the second plate ( 12 ) attenuates X-rays produced by the first plate ( 11 ).

2. Device according to claim 1 , characterised in that said mechanical guide and slide means ( 12 C, 12 D) comprises at least one slider ( 12 C) and at least one corresponding guide ( 12 D).

3. Device according to claim 1 , characterised in that said planar elements ( 10 ) are four, each planar element ( 10 ) having a first side ( 11 A, 12 A) provided with a projecting edge ( 12 C) with an L-shaped section,—and a second side ( 11 B, 12 B) provided with a notch ( 11 D, 12 D) with an L-shaped section, of shape and size corresponding to the ones of the projecting edge ( 12 C), whereby the projecting edge ( 12 C′) of a planar element ( 10 ′) is insertable and slidable in the notch ( 12 D″) of another planar element ( 10 ″).

4. Device according to claim 1 , characterised in that said first mechanical coupling means ( 13 ) comprises at least one screw ( 13 ).

5. Device according to claim 1 , characterised in that the first plate ( 11 ) of at least one planar element ( 10 ) has a larger surface than the second plate ( 12 ), a lower surface of the first plate ( 11 ) having a hollowed seat that houses the second plate ( 12 ), said first mechanical coupling means ( 13 ) comprising a screw ( 13 ).

6. Device according to claim 1 , characterised in that said second mechanical coupling means ( 13 , 14 ) comprises at least one screw ( 13 ) which is attached to the planar element ( 10 ) through a respective slot ( 14 ) of the slab ( 1 ).

7. Device according to claim 1 , characterised in that said first sterilisable material is selected from the group comprising polytetrafluoroethylene (PTFE), silicone and polymethylmethacrylate (PMMA), the first plate ( 11 ) having thickness ranging from 8 mm to 40 mm.

8. Device according to claim 1 , characterised in that said second sterilisable material is a metal selected from the group comprising stainless steel and titanium, said second plate ( 12 ) having a thickness ranging from 3 mm to 15 mm.

9. Device according to claim 1 , characterised in that it further comprises a frame ( 4 ) attached to the slab ( 1 ) and connected with adjustable spatial orientation, through third mechanical coupling means ( 5 , 6 , 7 , 8 , 9 ) for coupling to an operating table, said third mechanical coupling means comprising a first joint ( 5 ) for connecting the frame ( 4 ) to a first arm ( 6 ) which is in turn connected, through a second joint ( 7 ), to a second arm ( 8 ) connected to the operating table.

10. Automatic method for computing distribution of dose radiated by a IORT machine through a device for shaping an electron beam according to claim 1 , comprising the following steps:

measuring data related to said aperture ( 20 ) due to the reciprocal arrangement of said at least two planar elements ( 10 ),

measuring the energy of the electron beam generated by the IORT machine, determining a three-dimensional dose distribution after the device for shaping the electron beam corresponding to the reciprocal arrangement of said at least two planar elements ( 10 ), on the basis of simulated data, preferably according to a Monte Carlo simulation, of the three-dimensional dose distribution.