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Proceedings Paper

Effects of dead time on quantitative dual-energy imaging using a position-sensitive spectroscopic detector
Author(s): Louise M. Dummott; Giuseppe Schettino; Paul Seller; Matthew D. Wilson; Matthew C. Veale; Silvia Pani
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Paper Abstract

Dual energy imaging (DE) is a potential alternative to conventional mammography for patients with dense breasts. It requires intravenous injection of contrast agent (CA) and subsequent acquisition of images at two different energies. Each pixel is seen as a vector and is projected onto a two-material basis, e.g. water, CA, to form separate water-equivalent and CA-equivalent images. On conventional detectors, this requires two separate exposures. Spectroscopic detectors allow multiple images from a single exposure by integrating appropriate energy bands. This work investigates the effects of high count rates on quantitative DE imaging using a CdTe spectroscopic detector. Because of its small pixel size (250 μm), a limitation of the detector is charge sharing between pixels, which must be corrected to avoid degradation of the detected spectrum. However, as charge sharing is identified by neighbouring pixels registering a count in a given readout frame, an effective maximum count rate (EMR) is imposed, above which linearity between incident and detected counts is lost. A simulation was used to model detector response of a test object composed of water and iodine, with different EMRs and incident count rates. Using a known iodine thickness of 0.03 cm, and an EMR of 103 s−1 , the reconstructed thickness of iodine was found to be 97%, 74% and 24% of the true value for incident count rates of 100, 1000 and 10000 photons/pixel/s respectively. The simulation was validated by imaging a water-equivalent test phantom containing iodinated CA at different X-ray currents, to determine the optimum beam conditions.

Paper Details

Date Published: 9 March 2017
PDF: 9 pages
Proc. SPIE 10132, Medical Imaging 2017: Physics of Medical Imaging, 101323C (9 March 2017); doi: 10.1117/12.2254274
Show Author Affiliations
Louise M. Dummott, Univ. of Surrey (United Kingdom)
National Physical Lab. (United Kingdom)
Giuseppe Schettino, National Physical Lab. (United Kingdom)
Paul Seller, STFC Rutherford Appleton Lab. (United Kingdom)
Matthew D. Wilson, STFC Rutherford Appleton Lab. (United Kingdom)
Matthew C. Veale, STFC Rutherford Appleton Lab. (United Kingdom)
Silvia Pani, Univ. of Surrey (United Kingdom)

Published in SPIE Proceedings Vol. 10132:
Medical Imaging 2017: Physics of Medical Imaging
Thomas G. Flohr; Joseph Y. Lo; Taly Gilat Schmidt, Editor(s)

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