All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted , in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of the publisher. FOREWORD This report, \"Scintillation Camera Acceptance Testing and Performance Evaluation,\" is the sixth in a series of AAPM Reports. It is designed to provide users of the scintillation cameras with test procedures for performance evaluation. This report was prepared by the Nuclear Medicine Committee of the AAPM, under the chairmanship of Audrey V. Wegst. It was reviewed for the Publications Committee by Adrian LeBlanc to whom we are indebted for his careful review and comments. Issuance of such reports is one of the means that the AAPM employs to carry out its responsibility to prepare and disseminate technical information in medical physics and related fields. Its reports cover topics which may be scientific, educational or professional in nature, and final approval is given by the Council of the Association charged with responsibility for the particular concerns of each report.

https://tech.snmjournals.org/content/jnmt/9/2/105.4.full.pdf

Scintillation camera acceptance testing and performance evaluation

For more effective Tl-201 imaging, the location and width of the energy window set on the Hg-201 x-rays photopeak was investigated using Monte Carlo simulation and phantom experiments. We calculated energy spectra and investigated the amount of primary and scattered photons within various energy windows set on the x-rays photopeak. The energy resolution (ER) at 71 keV (the peak of the x-rays photopeak) was changed to 10%, 12%, 14% and 16%. The relationships between the energy window and the primary counts rate or the scatter fraction (= scattered counts/primary counts, SF) were obtained. By compromise between the primary counts rate and the SF for ER = 12%, the optimum energy window was determined as a wider off-peak window, 77 keV ± 14.3% (66–88 keV). This off-peak window increased the primary counts rate by 12.5% and decreased the SF by ~17% as compared with the conventional on-peak energy window (71 keV ± 10%, 64–78 keV). When this off-peak widow acquisition was compared with the conventional on-peak window one on a gamma camera, planar and SPECT images using the off-peak widow clearly showed superior results qualitatively and quantitatively.

Optimum energy window setting on Hg-201 x-rays photopeak for effective Tl-201 imaging

A scatter correction using a two-dimensional (2D) deconvolution method has been developed which compensates for Compton scattering in a triple-head gamma camera images It assumes that the scatter distribution in any projection can be estimated from sinogram activity distribution using a position-invariant scatter kernel The scatter distribution function has been derived from the measurements of a point source in a plastic phantom The scatter correction technique is based on filtering by 2D convolution in the spatial domain The spatial filter was designed to implement a 2D IIR filter The quality of the compensation is also evaluated by comparing the ratio of the average counts/pixel with and without scatter correction in clinical brain blood flow studies

A scatter correction based on the deconvolution method in SPECT

Quality of scintiscans taken with an Anger camera is dependent on the window settings. The authors derive an analytic expression to find the optimum window based on maximizing the signal to noise ratio. The signal is defined as the unscattered radiation both totally and partially absorbed in the NaI crystal, the noise is defined as scattered and background radiation. Signal and noise are characterized by an energy spectrum which are approximated by two Gaussians to simplify calculations. The effect of window settings on the line spread function obtained by an Anger camera with a 99Tcm line source in a water phantom were determined experimentally. The results suggest that the optimum window setting can be calculated using measured energy spectra of signal and noise.

P Spiegler

Papers

Optimizing the window of an Anger camera