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Purpose: The aims of this study were to develop and apply a method to correct for the differences in partial volume effects of pre-therapy Technetium-99 m (Tc)-MAA SPECT and post-therapy Yttrium-90 (Y) bremsstrahlung SPECT imaging in selective internal radiation therapy, and to use this method to improve quantitative comparison of predicted and delivered Y absorbed doses.
Methods: The spatial resolution of Tc SPECT data was converted to that of Y SPECT data using a function calculated from Tc and Y point spread functions. This resolution conversion method (RCM) was first applied to Tc and Y SPECT phantom data to validate the method, and then to clinical data to assess the power of Tc SPECT imaging to predict the therapeutic absorbed dose.
Results: The maximum difference between absorbed doses to phantom spheres was 178%. This was reduced to 27% after the RCM was applied. The clinical data demonstrated differences within 38% for mean absorbed doses delivered to the normal liver, which were reduced to 20% after application of the RCM. Analysis of clinical data showed that therapeutic absorbed doses delivered to tumours greater than 100 cm were predicted to within 52%, although there were differences of up to 210% for smaller tumours, even after the RCM was applied.
Conclusions: The RCM was successfully verified using phantom data. Analysis of the clinical data established that the Tc pre-therapy imaging was predictive of the Y absorbed dose to the normal liver to within 20%, but had poor predictability for tumours smaller than 100 cm.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8501309 | PMC |
| http://dx.doi.org/10.1016/j.ejmp.2021.07.026 | DOI Listing |
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