Active Pixel Sensor As Dosimetric Device For Interventional Radiology

Interventional Radiology (IR) is a subspecialty of radiology comprehensive of all minimally invasive diagnostic and therapeutic procedures performed using radiological devices to obtain image guidance. The interventional procedures are potentially harmful for interventional radiologists and medical staff due to the X-ray diffusion by the patient's body. The characteristic energy range of the diffused photons spans few tens of keV. Individual operators monitoring is very important and is performed via effective dose (whole body) and equivalent dose (hands, arms, legs, lens and thyroid). In this work we will present a proposal for an X-ray dosimeter prototype, capable of real-time measurement, packaged in a small form-factor, with wireless communication and no external power supply to be used for individual operators dosimetry for IR procedures. The sensor elements proposed are Active pixel sensors. They have shown a good capability as ionizing radiation detectors for the X-ray energy range of interest. The performance of several sensors, both research prototype and standard CMOS imagers have been studied in realistic Interventional Radiology conditions. Two dosimetric quantities have been studied, the number of detected photons and the measured energy deposition. Both observables have a linear dependence with the dose measured by commercial dosimeters. The uncertainties in the measurement are dominated by statistic and can be pushed below 5%. The acquisition frequency can be kept at 1 Hz thus allowing a fast enough dose rate measurement. The high sensor segmentation permits to measure high photon fluxes (tens of thousands of photons in each frame) without signal saturation. Another desirable characteristic of Active Pixel Sensors is the sensitivity to low energy photons (down to few keV) considerably lower than the commercially available dosimeters, allowing to measure this radiation component, important for the evaluation of epidermis damages.