Comparison of 90Y SIRT predicted and delivered absorbed doses using a PSF conversion method. (September 2021)

• Record Type: Journal Article
• Authors: Craig, Allison J.; Murray, Iain; Denis-Bacelar, Ana M.; Rojas, Bruno; Gear, Jonathan I.; Hossen, Lucy; Maenhout, Annelies; Khan, Nasir; Flux, Glenn D.
• Is Part Of: Physica medica. Volume 89(2021)
• Page Start: 1
• Page End: 10
• Publication Date: 2021-09
• Subjects: Radioembolisation -- Y-90 -- SIRT -- Liver -- Dosimetry -- Microspheres; Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2021.07.026
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: The resolution conversion method allowed comparison of 99m Tc and 90 Y imaging. 99m Tc pre-therapy imaging was predictive of the 90 Y absorbed dose to normal liver. 99m Tc pre-therapy imaging had poor predictability for tumours smaller than 100 cm 3 . Abstract: 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 ( 99m Tc)-MAA SPECT and post-therapy Yttrium-90 ( 90 Y) bremsstrahlung SPECT imaging in selective internal radiation therapy, and to use this method to improve quantitative comparison of predicted and delivered 90 Y absorbed doses. Methods: The spatial resolution of 99m Tc SPECT data was converted to that of 90 Y SPECT data using a function calculated from 99m Tc and 90 Y point spread functions. This resolution conversion method (RCM) was first applied to 99m Tc and 90 Y SPECT phantom data to validate the method, and then to clinical data to assess the power of 99m 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 3 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 99m Tc pre-therapy imaging was predictive of the 90 Y absorbed dose to the normal liver to within 20%, but had poor predictability for tumours smaller than 100 cm 3 .