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

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Biomedical Engineering

Background:

• Accurate quantification in micro-single-photon emission computed tomography (SPECT) is crucial for preclinical research.
• Ray-based iterative reconstruction methods offer potential for improved image quality and accuracy.
• Existing methods may face challenges in achieving precise in vivo quantification.

Purpose of the Study:

• To measure and minimize in vivo quantification errors in micro-SPECT using ray-based iterative reconstruction.
• To evaluate the performance of advanced reconstruction techniques on a cadmium zinc telluride (CZT)-based small-animal scanner.
• To demonstrate the feasibility of absolute quantitative SPECT without explicit system matrix measurements.

Main Methods:

• Utilized GPU-based ray tracing for iterative reconstruction, incorporating scatter correction, CT-based attenuation correction, resolution recovery, and edge-preserving smoothing.
• Validated the reconstruction algorithm using a National Electrical Manufacturers Association (NEMA) phantom.
• Assessed in vivo quantification errors using two radiotracers: 99mTc-dimercaptosuccinic acid ([99mTc]DMSA) in mouse kidneys and 111In-octreotide in neuroendocrine tumor xenografts.

Main Results:

• The reconstruction method significantly reduced uncorrected quantification errors for 99mTc from 28 ± 3% to 8 ± 3% and for 111In from 26 ± 14% to 6 ± 22%.
• In vivo errors for [99mTc]DMSA were reduced from 16.2 ± 2.8% to -0.3 ± 2.1%, and for [111In]octreotide from 16.7 ± 10.1% to 2.2 ± 10.6%.
• Achieved an absolute in vivo quantification error smaller than 5% for both tested radiotracers.

Conclusions:

• Ray-based iterative reconstruction with advanced corrections enables absolute quantitative in vivo SPECT.
• The developed method provides high accuracy without requiring explicit system matrix measurements.
• This approach is effective for quantitative imaging of various radiotracers in small-animal models.