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A new method for quantification of image distortion due to pile-up in scintillation cameras

Author:
  • Crister Ceberg
  • Ingemar Larsson
  • Sven-Erik Strand
Publishing year: 1991
Language: English
Pages: 959-963
Publication/Series: European Journal Of Nuclear Medicine
Volume: 18
Issue: 12
Document type: Journal article
Publisher: Springer

Abstract english

Characterization of the count-rate performance of scintillation cameras should include not only the specification of count losses. At high count rates, there is also an image distortion due to the mispositioning of pile-up events. In this paper a simple and clinically relevant procedure to quantify this distortion is presented. The images of a square uniform technetium-99m phantom at high and low count rates are used. The fraction of the total counts being correctly positioned is determined as the peripheral count density divided by the total average count density. This ratio, corrected for the camera non-uniformity at low count rates, is called the 'positioning ability'. According to the National Electrical Manufacturers' Association (NEMA), the 'system count rate performance with scatter' should be reported as the measured count rate giving 20% count losses. In this paper it is suggested that this measure be complemented by a measure of the fraction correct positioned events at this count rate. This fraction, the 'high count rate positioning ability', can be easily and accurately measured using our method. The method has been tested on two different scintillation cameras. For one of them the high count rate positioning ability was determined as 91% at a measured count rate of 30,000 s-1 with 20% count losses. For the other camera, the corresponding figures were 88% at 59,000 s-1 and close to 100% at 38,000 s-1, before and after the installation of a new pile-up rejection circuit, respectively.

Keywords

  • Radiology, Nuclear Medicine and Medical Imaging
  • Scintillation camera
  • Pile-up
  • Image distortion
  • Quantification

Other

Published
  • ISSN: 1432-105X
Sven-Erik Strand
E-mail: sven-erik.strand [at] med.lu.se

Project manager

Systemic Radiation Therapy Group

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Professor emeritus

Medical Radiation Physics, Lund

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