3D image-based dosimetry for Yttrium-90 radioembolization of hepatocellular carcinoma: Impact of imaging method on absorbed dose estimates.

BACKGROUND

To improve therapy outcome of Yttrium-90 selective internal radiation therapy (Y SIRT), patient-specific post-therapeutic dosimetry is required. For this purpose, various dosimetric approaches based on different available imaging data have been reported. The aim of this work was to compare post-therapeutic 3D absorbed dose images using Technetium-99m (Tc) MAA SPECT/CT, Yttrium-90 (Y) bremsstrahlung (BRS) SPECT/CT, and Y PET/CT.

METHODS

Ten SIRTs of nine patients with unresectable hepatocellular carcinoma (HCC) were investigated. The Tc SPECT/CT data, obtained from Tc-MAA-based treatment simulation prior to Y SIRT, were scaled with the administered Y therapy activity. 3D absorbed dose images were generated by dose kernel convolution with scaled Tc/Y SPECT/CT, Y BRS SPECT/CT, and Y PET/CT data of each patient. Absorbed dose estimates in tumor and healthy liver tissue obtained using the two SPECT/CT methods were compared against Y PET/CT.

RESULTS

The percentage deviation of tumor absorbed dose estimates from Y PET/CT values was on average -2 ± 18% for scaled Tc/Y SPECT/CT, whereas estimates from Y BRS SPECT/CT differed on average by -50 ± 13%. For healthy liver absorbed dose estimates, all three imaging methods revealed comparable values.

CONCLUSION

The quantification capabilities of the imaging data influence Y SIRT tumor dosimetry, while healthy liver absorbed dose values were comparable for all investigated imaging data. When no Y PET/CT image data are available, the proposed scaled Tc/Y SPECT/CT dosimetry method was found to be more appropriate for HCC tumor dosimetry than Y BRS SPECT/CT based dosimetry.