Direct Monitoring Method to Detect Internal Radioactive Contamination

Direct monitoring technique for evaluation of internal contamination is a century old mature method used for assessment of internal dose. It is used for estimation of organ/whole body activity of low or high energy photon emitters and energetic beta emitters such as actinides, fission and activation products. It is considered to be the fastest, non-invasive and most accurate method for measuring internal activity among all the available methods. Evolution of detectors, shielding, measurement geometry and calibration methods as well as phantoms is provided in this chapter. In detector, beginning from ionisation chamber to the currently used HPGe detectors are covered. Shielding evolution is described from earlier water shielded systems to presently available totally shielded steel rooms and portable systems. Monitoring geometries such as arc, chair, scanning bed, as well as organ specific geometries are explained in detail. Evolution of calibration methods right from in-vivo inhalation experiments to the advanced mesh phantoms is explained. Finally, importance of well calibrated system with the proper phantoms is stressed and explained in detail. Using proper detection system, measurement geometry and phantom, calculation of organ/whole body activity is described. The chapter covers all the important aspects of direct monitoring technique. It will be useful for the beginners as well as the persons working in the direct monitoring laboratories.