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This Article Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Song, N. Articles by Frey, E. PubMed Articles by Song, N. Articles by Frey, E.

Evaluation of accuracy and precision of organ activity estimates from quantitative I-131 SPECT

¹ Radiology, Johns Hopkins University, Baltimore, Maryland

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Objectives: Estimating organ activities is essential in targeted radionuclide therapy treatment planning. A number of therapies involve I-131 labeled agents where septal penetration and scatter are significant factors. The goal of this work was to adapt quantitative SPECT (QSPECT) reconstruction methods that include various combinations of attenuation (A), scatter (S), and the geometric (G) or full (D) collimator-detector response for I-131 imaging and evaluate them for organ activity estimation.

Methods: We used the realistic 3D NCAT phantom to model patient anatomy and organ activities based on I-131 Bexxar patient scans. Simulated projection data were generated using previously-validated Monte Carlo simulation techniques. We generated 50 projection datasets with independent, clinically realistic noise levels. Images were then reconstructed using the ordered subsets-expectation maximization (OS-EM) algorithm with A, AS, AGS or ADS compensation. The resulting images were evaluated in terms of the error and standard deviation (SD) of the organ activity estimates in the heart, lungs, kidneys, liver, and spleen.

Results: In almost all cases, the rankings of the compensation methods in terms of accuracy, from worst to best, was A, AGS, AS and ADS. All combinations of compensations except ADS and AS (in one organ) resulted in overestimation of organ activities by more than 10% for all organs, while the average error for ADS was better than 5% for all organs. In all cases, the percent SD was much smaller than the percent error.

Conclusions: We conclude that the use of ADS compensation dramatically improves the accuracy of activity estimates in I-131 SPECT, and can provide errors in organ activity estimates better than 5%.

This Article Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Song, N. Articles by Frey, E. PubMed Articles by Song, N. Articles by Frey, E.