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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 Harker, A. Articles by Avram, A. PubMed Articles by Harker, A. Articles by Avram, A.

I-131 SPECT/CT scintigraphy: What are the optimal acquisition and reconstruction parameters?

¹ Nuclear Medicine, University of Michigan, Ann Arbor, Michigan

2015

Objectives: Diagnostic 1 mCi I-131 scans obtained in 56 thyroid cancer patients showed that 16% of OSEM SPECT scans did not portray all foci of activity visible on planar and FBP SPECT images. We used an anthropomorphic phantom to determine the activity threshold at which low count foci visible on planar imaging are not visualized on OSEM SPECT, and which reconstruction techniques might recover these foci.

Methods: Lesions were simulated with 0.6, 0.8, 2.7 and 16.2 µCi I-131 capsules placed in the neck, and 0.8 and 5.0 µCi capsules placed in the thorax. Planar images were acquired for 20 minutes and SPECT images acquired with a non-circular orbit, at 15 and 30 secs/stop, 64 steps, with 128 and 64 matrices. SPECT data were processed with FBP and 3D-OSEM, with and without attenuation correction. The 128 matrix acquisitions were reformatted to 64 and processed using the same methods.

Results: All phantom foci were visualized on planar imaging. FBP images using 128 matrix data visualized all foci; however adjacent neck lesions were obscured by star artifact. Low activity foci (0.6 and 0.8 uCi), although seen on planar and FBP, were not visualized on OSEM. Reformatting the 128 to a 64 matrix allowed all foci to be visualized on OSEM; however the increased pixel size led to reduced spatial resolution. Results were identical for 15 and 30 secs/stop acquisitions.

Conclusions: Low count activity foci visible on planar I-131 scintigraphy may not be visualized on OSEM reconstruction. For optimal imaging SPECT should be acquired on 128 matrix for 30 sec/frame to maintain the best spatial resolution, then be reformatted to 64 matrix to increase counts/pixel. SPECT data should be reconstructed using both FBP and 3D-OSEM with attenuation correction and reviewed with planar images.

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 Harker, A. Articles by Avram, A. PubMed Articles by Harker, A. Articles by Avram, A.