A novel X-ray transmission ionization chamber dosemeter for patient dose measurements in diagnostic radiology

This paper describes an X-ray transmission ionization chamber diagnostic dosemeter for patient dose measurements and control. The chamber uses a commercially available radiofrequency screen as the wall material in a parallel-plate configuration. A digital varactor bridge electrometer serves to measure air kerma times area of fluoroscopic and radiographic beams. Detailed investigations on the characteristics of the chamber such as saturation, sensitivity, energy dependence (50-150 kV), response versus radiation field area, uniformity of response of the chamber, effects of distance and long-term stability have been carried out. The results demonstrate that the chamber meets all the requirements and can measure the incident patient dose with an overall uncertainty of +/- 11%. The chamber can be either mounted on the housing of the light beam diaphragm of the X-ray unit or used as a stand-alone system along with an image-intensifier TV monitor. It is inexpensive to build and is recommended particularly for hospitals in developing countries.