Cgr Mev

Rene Boux

Guy Azam

Claude Levaillant

Jean Noel Bourlier

Device making it possible to check, prior to or after each irradiation treatment session, the proper operation of the dose-measuring systems associated with a radiotherapy apparatus and comprising at least one dose-measuring circuit equipped with a counter system of preselect design. This device comprises a pulse generator G, means for applying said pulses to the counter system of at least one of the measuring circuits and means making it possible to halt the generator G and reset the counter system to zero when coincidence occurs between the preselected number of pulses corresponding to a preselected dose level D and the displayed number of pulses corresponding to the dose level effectively delivered by an irradiation source S.

Device for checking the irradiation dose measuring circuits used to

A system for measuring radiation doses in radiotherapy comprises two identical metering networks energized in parallel from a common radiation source, each network including an integrating amplifier whose time constant is variable by the short-circuiting of an input resistor. A manually or automatically reversible switch selectively foreshortens the time constant of one or the other amplifier whereby the corresponding metering network controls the cutoff of the radiation source whenever the emitted radiant energy reaches a predetermined value. The other network, acting as a backup, takes over the radiation cutoff upon failure of the controlling network; this takeover may be indicated by a set of signal lamps jointly controlled by the reversing switch and by a counting unit of the standby network.

System for measuring radiation doses in radiotherapy apparatus

An ionization chamber is peripherally bounded by a stack of four coaxial annular frames with rabbeted confronting faces forming three annular recesses on the peripheral chamber wall, the middle recess receiving a transverse partition whereas the other two recesses form seats for peripheral zones of two dielectric disks with discontinuous metallic coatings constituting mutually insulated segmental electrode elements. The segmental elements terminate short of the peripheral chamber wall, except for a tab extending from each element onto the peripheral disk zone received in the corresponding recess within which that tab is connected to an external lead. The tabs of the two disks are angularly offset from one another, as are the segmental boundaries of their conductive elements.

Device for monitoring the position, intensity, uniformity and

A centering process for detecting the centering errors of a sweep beam impinging on a target and correcting them, this process comprising comparing a signal V.sub.E, corresponding to the difference between electric signals received on the two halves of an electrode, with threshold voltages .+-.v.sub.e and comparing a signal V.sub.B, corresponding to the voltage controlling the sweep of the beam, with threshold voltages .+-.v.sub.b, the transmission of a signal V.sub.p corresponding to V.sub.E &lt; + v.sub.e and V.sub.B &lt; - v.sub.b (or of a signal v.sub.n corresponding to V.sub.E &lt; - v.sub.e and V.sub.B &gt; + v.sub.b) indicating the direction of the centering error and its amplitude. The process permits controlling the centering of a sweep beam on secant axes making an angle .theta. therebetween.

Process for centering an ionizing radiation sweep beam and device for

A monitoring device transparent to ionizing radiation, designed to measure the orientation, intensity and uniformity of an incident beam, comprises a cylindrical housing forming at least one ionization chamber with one or more ion-collecting electrodes transverse to the housing axis, each electrode being subdivided into a plurality of mutually insulated conductive elements connected to respective amplifiers. The elements of at least one electrode include one or more outer elements surrounding or bracketing one or more inner elements to measure the radiation in a central zone and a peripheral zone. The outputs of the respective amplifiers are additively and subtractively combined in an evaluation circuit.

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Paris, France

Rene Boux