Development of in-vivo dosimetry for applications in radiotherapy (J2-5474)

The project aims for development of technologies which lead to construction of one or two dimensional dosimetric sensors fields for in-vivo dosimetry in medical applications, mainly radiotherapies. The sensor technologies chosen for investigation are mono-crystalline diamond detectors and special p-MOSFET transistors (RadFET). Both sensor types differ in almost all relevant parameters: crystal properties (atomic number Z), the radiation detection principle, geometry and readout, hence represent a complementary choice.

Dosimeters will be hosted by a thin ()=50 mm) flexible printed circuits with a minimum pitch of 100 mm. In addition to the consequent reduced influence of substrate material to the measured dose for X and g rays, the flexible circuits will enable construction of different sensor patterns at small printed circuit dimensions (large density of sensors).

As an example of in-vivo dosimetric array a linear sensor array (dosimeter) with diameter of (2 mm will be developed. Such dimensions roughly correspond to the thickness of the catheter inserted in the tumour during PDR/HDR (High Dose Rate/Pulse Dose Rate) brachytherapy. During the brachytherapy an after-loading applicator inserts a highly active radioisotope 192Ir to different locations in the catheters and in such a way delivers the dose to the carcinoma. The dosimeter will consist of 5-10 sensors (size ~mm3) stretched over ~10 cm distance. It will enable in-vivo dose measurements at known points in the tumour and will contribute to much higher quality of the therapy: cross-check of the treatment plan, on-line correction of the treatment plan, damage assessment to the cancerous and healthy tissue. Arrays of sensitive dosimetric sensors (sensitive from ~10-4-10-3 Gy) can also be exploited for tracking the source locations during the treatment in brachytherapy and therefore contributes to the quality assurance of the treatment.

One of the main goals of the project is therefore the development of multi-channel (~2x10 channels) readout electronics, which will be read out on the scale of seconds. The readout electronics will be connected to the PC, which will monitor the readout electronics and provide the user interface to the measurements.

The development of the in-vivo dosimetry will be supported by Monte-Carlo simulation, which is of crucial importance for understanding the measurements and calibration of the dosimeters. The software tools will be modular and therefore enable fast adaptation to any other sensor array or/and application.

Sensors and sensor arrays will be extensively tested in the system for sensor characterization with electrons from 90Sr source and X-rays and also in phantom with therapeutic source (192Ir).