A Workflow for Dosimetry of Y-90 Radioembolization Based on Quantitative Tc-99(m)-MAA SPECT/CT Imaging and a 3D-Printed Phantom

At a time of increasing evidence for dose-effect relationships in radioembolization (RE) with Y-90-microspheres, the general consensus is that there is an urgent need for accurate treatment planning and dose assessment in patients undergoing RE treatment. This work aimed at assessing the usefulness of Tc-99(m) macroaggregated albumin (MAA) SPECT/CT imaging for personalized provisional RE dosimetry considering a 3D-printed patientlike phantom (AdboMan phantom). A homemade tool was developed in MATLAB for image analysis and absorbed dose calculation. Two dose calculaton methods were implemented and used to calculate dose volume histograms: (I) dose kernel method and (II) local energy deposition method. The accuracy of the two different dosimetric methods was evaluated by means of 3D gamma-index (1%-1 mm and 2%-2 mm) implemented in the tool. Differences between the two dose calculation methods using the 3D gamma-index are within 1%-1 mm and 2%-2 mm for all AbdoMan inserts, with a passing rate of 99.9% and 100%, respectively, proving a good agreement between the two calculation methods. The present study supports the use of Tc-99(m)-MAA SPECT acquisition for provisional dosimetry along with the local energy deposition method to convert reconstructed SPECT data into absorbed dose maps. As long as Tc-99(m)-MAA SPECT acquisitions are performed on liver lesions larger than 40 mm, the absorbed dose computed by means of the local energy deposition method can lead to results in line with those obtained by Monte Carlo calculations.