Full body counter

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Whole body counter for quick measurements while standing with a built-in calibration phantom
Whole body counter of the German Federal Office for Radiation Protection in Neuherberg for measurements of even small body activity

Whole body counter ( English whole-body counter ) are used to determine the activity and distribution of gamma-emitting nuclides in the living body ( in vivo determination). The underlying measuring principle is gamma spectrometry .

purpose

Whole-body counters are used in radiation protection to detect the uptake ( incorporation ) of radionuclides in people who deal with gamma-emitting unsealed radioactive substances and may be contaminated through food, inhalation of dusts and gases or through open wounds .

Gamma emitters adhering to the surface of the body are inevitably also measured, so that the search for absorbed nuclides can only begin if the same activity is measured before and after cleaning, which may require several cleanings in succession. Only then can this remaining activity be ascribed to the incorporated radiators alone.

For use in areas that are difficult to access, whole-body counters are also installed in appropriate measuring vehicles.

Basis of the measurements

Measurements with this method are only possible if radionuclides have been recorded that emit gamma radiation ( α and β emitters cannot be measured with them). The gamma radiation is measured with several large, mostly movable gamma detectors , namely both the amount of radiation and its energy distribution, which allows conclusions to be drawn about the nuclides incorporated in each case. Even more precise results can be obtained from measurements at time intervals from which the half-lives can also be calculated, so that the type of incorporated radioactive nuclides can be precisely determined from the energy distribution and the associated half-life. Body areas with more intense radiation can be narrowed down; this allows conclusions to be drawn as to which organs are affected.

The amount of gamma radiation is calculated based on the count rates measured by the gamma detectors. When taking a measurement, the results of all the detectors available are usually added together. The energy distribution results from the recorded spectra.

Whole-body counters are surrounded by shields (e.g. made of lead) so that very low levels of activity can be detected that would otherwise be masked by the terrestrial ambient radiation. The residual background radiation that is still present despite the shielding must be determined separately and subtracted from the measurement result.

Whole body counter in Germany, Austria and Switzerland

(Examples)

swell

  1. ↑ H. Dederichs, J. Pillath, B. Heuel-Fabianek, P. Hill, R. Lennartz: Long-term observation of the dose exposure of the population in radioactively contaminated areas of Belarus - Korma study (=  writings of the Research Center Jülich Series Energy & Environment . Volume 31 ). Forschungszentrum Jülich , 2009, ISBN 978-3-89336-562-3 ( hdl: 2128/11363 , full text as PDF file, 105 MByte, at fz-juelich.de ).

literature

  • T. Ishikawa: Performance of a whole-body counter with five high-purity germanium detectors . In: Applied Radiation and Isotopes . tape 64 , March 2006, p. 386-389 , doi : 10.1016 / j.apradiso.2005.09.004 .
  • S. Kinase, H. Noguchi, T. Nakamura: Application of a Ge semi-conductor detector to whole-body counter . In: Radiation Protection Dosimetry . tape 105 , July 1, 2003, p. 467-472 , doi : 10.1093 / oxfordjournals.rpd.a006283 .
  • S. Kinase, S. Takagi, H. Noguchi, K. Saito: Application of voxel phantoms and Monte Carlo method to whole-body counter calibration . In: Radiation Protection Dosimetry . tape 125 , no. 1-4 , July 2007, pp. 189-193 , doi : 10.1093 / rpd / ncm197 .
  • GH Kramer, K. Capello: The StandFast whole body counter: efficiency as a function of BOMAB phantom size and energy modeled by MCNP5 . In: Health Physics . tape 92 , no. 3 , 2007, p. 290-296 , doi : 10.1097 / 01.HP.0000246233.61967.3a .
  • H. Schicha, O. Schober: Nuclear medicine: basic knowledge and clinical application . Schattauer Verlag, Stuttgart, New York 2007, ISBN 3-7945-2438-1 , pp. 68–69 (With an explanation of the functionality and areas of application of whole-body counters).
  • M. Schläger: Precise modeling of coaxial germanium detectors in preparation for a mathematical calibration . In: Nuclear Instruments & Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment . tape 580 , no. 1 , September 21, 2007, p. 137–140 , doi : 10.1016 / j.nima.2007.05.053 (explanations on the mathematical calibration of a whole-body counter ).

Web links

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