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The effects of mismatch between SPECT and CT images on quantitative activity estimation - A simulation study
Yingqing Lyu1, Gefei Chen1, Zhonglin Lu1
1Biomedical Imaging Laboratory (BIG), Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Taipa, Macau SAR, China.
Zeitschrift Fur Medizinische Physik
|June 1, 2022
Summary
Image mismatch in nuclear medicine significantly impacts quantitative activity estimation. Volume-of-interest delineation errors cause the largest inaccuracies, highlighting the need for precise SPECT/CT registration.
Area of Science:
- Nuclear Medicine Imaging
- Medical Physics
- Radiopharmaceutical Therapy
Background:
- Accurate quantitative activity estimation is crucial in nuclear medicine.
- Patient movement between SPECT and CT scans introduces image mismatch, affecting diagnostic accuracy and radionuclide therapy dosimetry.
Purpose of the Study:
- To investigate the impact of CT-SPECT image mismatch on attenuation correction (AC), volume-of-interest (VOI) delineation, and image registration for quantitative activity estimation.
- To quantify the errors introduced by these mismatches in diagnostic studies and therapy dosimetry.
Main Methods:
- Generated 4D XCAT phantoms with varying parameters at different time points post-injection.
- Simulated realistic SPECT projections and reconstructed images using OS-EM.
- Introduced controlled shifts in CT images to simulate mismatch for AC, VOI delineation, and registration.
- Calculated organ activity errors (%OAE) and time-integrated activity errors (%TIAE) after bi-exponential curve fitting.
Main Results:
- Attenuation correction mismatch errors were larger for organs near ribs.
- Volume-of-interest delineation errors significantly impacted small and low-uptake organs.
- Time-integrated activity errors were highest for VOI mismatch (20.62%), followed by registration (9.33%) and AC (1.13%).
Conclusions:
- Image mismatch, particularly from VOI delineation, substantially degrades quantitative activity estimation accuracy.
- Synchronized registration of emission (SPECT) and transmission (CT) images at the same time point is recommended to ensure diagnostic and dosimetric precision.
