The effect of calibration factor geometries on the accuracy of 99mtc spect activity quantification
Quantitative SPECT imaging has become increasingly important in disease diagnosis and monitoring. Achieving accurate absolute quantification of radiotracer distribution is essential for dosimetry-based personalized radionuclide therapy. A key determinant of SPECT/CT quantification accuracy is the...
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| Format: | Thesis |
| Language: | en |
| Published: |
2025
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| Subjects: | |
| Online Access: | http://eprints.usm.my/62962/1/AZMIN%20NUR%20AINA%20AZMI.-E.pdf http://eprints.usm.my/62962/ |
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| Summary: | Quantitative SPECT imaging has become increasingly important in disease
diagnosis and monitoring. Achieving accurate absolute quantification of radiotracer
distribution is essential for dosimetry-based personalized radionuclide therapy. A key
determinant of SPECT/CT quantification accuracy is the calibration factor (CF). This
study aimed to evaluate the impact of CFs and recovery coefficients (RCs) derived from
different calibration geometries on SPECT/CT quantification accuracy. Three phantom
geometries were assessed: a petri dish filled with 99mTc (Geometry 1), a whole body
NEMA phantom filled with 99mTc (Geometry 2), and a sphere filled with 99mTc attached
to the cylindrical in NEMA phantom (Geometry 3). CFs were calculated for each
geometry, and RCs were obtained for six spheres with varied diameters (1.0 to 3.7 cm).
Quantification errors were analysed both before and after the application of partial
volume correction (PVC).
Geometry 1 yielded the highest CF, primarily due to the use of a different activity
concentration. This resulted in lower RCs and greater quantification errors, largely
attributable to pronounced PVE. Consequently, the results from Geometry 1 are not
directly comparable to those of the other geometries due to the disparity in activity
concentration. Geometry 2 demonstrated the most accurate and consistent RCs reaching
values as high as 1.03 indicating optimal conditions for quantification. Geometry 3
yielded moderate performance, although spill-in effects were observed at smaller sphere
sizes. PVC substantially improved quantification for small spheres across all geometries.
However, overestimation errors emerged in larger volumes, especially in Geometries 1
and 3. In conclusion, the choice of calibration geometry has a significant influence on the
quantitative accuracy of SPECT/CT imaging. These findings highlight the importance of selecting appropriate calibration strategies and applying geometry-specific corrections to
improve clinical accuracy in radionuclide therapy. |
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