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AssigneeQualiformed Sarl
InventorsSTEPHANE BEAUMONT, MARGIT VILLING, YVES BARBOTTEAU, RACHID BOUCENNA
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This phantom object is designed for a Winston-Lutz test on a device for radiation therapy treatment comprising a patient support having a rotation axis (V), a stand having a rotation axis (H) and a collimator having a rotation axis (C), locating means being provided for visually representing the theoretical positions (V′, H′, C′) of the three axes (V, H, C). A spherical ball is positioned at the center of a sphere in a material of electron density lower than that of the ball, the ball and the sphere both constituting the phantom object. The sphere has on its outer surface means for a visual alignment with the locating means allowing a positioning of the phantom object at the point of convergence of the three axes (V′, H′, C′).
1- Phantom object for a quality control test of a device for radiation therapy treatment, comprising a spherical ball made of a material with an electron density d1, wherein the spherical ball of electron density d1 is positioned at the center of a sphere made of a material having an electron density d2, the sphere and the ball both constituting the phantom object, wherein said ball has a diameter between 2 and 10 mm, preferably between 5 and 6 mm, and said sphere has a diameter between 80 and 200 mm, the ratio of the electron density d1 on the electron density d2 being superior or equal to 1.1, and wherein said sphere bears on its outer surface visual alignment means consisting in three visible equatorial lines orthogonal pairwise, formed on the surface of the sphere and allowing a positioning of the phantom object, said sphere comprising means for securing it to placing means for placing the phantom object on the device for radiation therapy treatment.
2- Phantom object according to claim 1, wherein the material of electron density d2 from which the sphere is made is a plastic material, in particular a plastic material transparent for the visible light, preferably in poly(methylmethacrylate) (PMMA).
3- Phantom object according to claim 1, wherein the means for aligning-positioning formed on the surface of the sphere made in a material of electron density d2 are represented physically by a painted or printed line, or by an engraved groove.
4- Phantom object according to claim 3, wherein the means for aligning-positioning the sphere further comprise, on either side of each equatorial line, additional visible lines, preferably discontinuous, parallel to the three equatorial lines, wherein said additional visible lines are represented physically by a painted or printed line, or by an engraved groove and said additional visible lines are formed at a preset spacing from the associated equatorial line.
5- Phantom object according to claim 4, wherein the visible lines and, when provided, the additional visible lines, are covered with a substance adapted to reflect the light in the visible spectrum, to be illuminated with the same color as the color of laser layers, when said visible lines, and when provided, when said additional visible lines, are aligned with the laser layers.
6- Phantom object according to claim 4, wherein the visible lines, and, when provided, the additional visible lines, are provided in strip-shaped equatorial areas of the surface of the sphere, which have been treated to absorb or to diffuse light in the visible spectrum.
7- Phantom object according to claim 6, wherein the strip-shaped areas are formed by grinding or by a dark colored paint.
8- Phantom object according to claim 4, wherein the visible lines, and, when provided, the additional visible lines have a width between 0.1 mm and 0.5 mm, preferably of 0.2 mm, and the additional visible lines, when provided, are spaced by 1 mm on either side of each equatorial visible line, and the strip-shaped areas, when provided, have a width between 2 mm and 10 mm, preferably of 5 mm.
9- Phantom object according to claim 1, wherein the material of electron density d1 from which the ball is made is tungsten.
10- Phantom object according to claim 1, wherein the placing means consists in a rod-like or tube-like metal elongated element, the metal being titanium or aluminium, an end of which is to be inserted in a hole provided in the sphere and to be secured therein by screwing, and in a plate which is attached at the other end of the elongated element and which is arranged to act as a counter-weight to the phantom object and to the elongated element when the plate is positioned with respect to the device for radiation therapy treatment.
11- Phantom object according to claim 10, wherein the plate is provided with means for adjusting the level of said plate with respect to the plane of a patient support of the device for radiation therapy treatment during the positioning of the phantom object.
12- Phantom object according to claim 10, wherein the sphere is provided with a radial channel with a diameter slightly larger than the diameter of the ball, said channel being plugged by a rod made of a material of electron density d2, which can protrude out the surface of the sphere, and wherein the elongated element is adapted to be connected to the sphere by screwing at the periphery of the rod, said elongated element comprising an axial recess shaped complementarily to the shape of the rod when said rod is protruding, in order to accommodate this protruding part.
13- Phantom object according to claim 10, wherein the elongated element is secured to the sphere at the intersection of two equatorial visible lines.
14- Method for the manufacture of a phantom object as defined in claim 6, wherein the method comprises the steps of:
15- Method of checking the coincidence, the orthogonality and the position in a treatment room space of the locating means of the isocenter of a device for radiation therapy treatment, wherein said isocenter is the intersection point of the three theoretical rotation axes (V′, H′, C′) of the device for radiation therapy treatment, wherein the method comprises the steps of:
16- Method of searching the isocenter of a device of radiation therapy treatment, using a phantom object as defined in claim 1, wherein external and/or device-supported means are provided for representing visually the three theoretical axes (V′, H′, C′) of the device and their intersection point or isocenter, wherein the method comprises the steps of: