Use of a ray-based reconstruction algorithm to accurately quantify preclinical microspect images

Abstract

This work aimed to measure the in vivo quantification errors obtained when ray-based iterative reconstruction is used in micro-singlephoton emission computed tomography (SPECT). This was investigated with an extensive phantom-based evaluation and two typical in vivo studies using 99mTc and 111In, measured on a commercially available cadmium zinc telluride (CZT)-based small-animal scanner. Iterative reconstruction was implemented on the GPU using ray tracing, including (1) scatter correction, (2) computed tomography- based attenuation correction, (3) resolution recovery, and (4) edge-preserving smoothing. It was validated using a National Electrical Manufacturers Association (NEMA) phantom. The in vivo quantification error was determined for two radiotracers: [99mTc]DMSA in naive mice (n = 10 kidneys) and [111In]octreotide in mice (n = 6) inoculated with a xenograft neuroendocrine tumor (NCI-H727). The measured energy resolution is 5.3% for 140.51 keV ( 99mTc), 4.8% for 171.30 keV, and 3.3% for 245.39 keV (111In). For [99mTc, an uncorrected quantification error of 2863% is reduced to 8 63%. For [111In, the error reduces from26614% to ± 622%. The in vivo errorobtained with 99mTc-dimercaptosuccinic acid ([[99mTc] DMSA) is reduced from16.2±2.8%to20.3 62.1% and from16.7±10.1% to 2.2 ± 10.6% with [[111In]octreotide. Absolute quantitative in vivo SPECT is possible without explicit system matrix measurements. An absolute in vivo quantification error smaller than 5% was achieved and exemplified for both [[99mTc]DMSA and [111In]octreotide. © 10.2310/7290.2014.00007.