Establishing Updated Safety Standards for Independent 99mTc-MAA SPECT/CT Treatment Planning in Radioembolization.

Significant improvements within radioembolization imaging and dosimetry permit the development of an accurate and personalized pretreatment plan with technetium 99 m –labeled macroaggregated albumin single-photon emission computed tomography (99m Tc-MAA SPECT/CT). Despite these potential advantages, the clinical transition to pretreatment protocols with SPECT/CT is hindered by its unknown safety constraints. This study aimed to address this issue by establishing novel dose limits for 99m Tc-MAA SPECT/CT to enable quantitative pretreatment planning. Stratification criteria to determine images most viable for dosimetry analysis were created from a cohort of 85 patients. SPECT/CT, cone beam CT, and activity calculations derived from the local deposition method were used to create an accurate pretreatment protocol. Planar and SPECT/CT images were compared using linear regression and modified Bland-Altman analyses to convert accepted planar dose limits to SPECT/CT. To validate these new dose limits, activity calculations based on SPECT/CT were compared with those calculated with the body surface area and planar methods for 3 treatment plans. A total of 38 of 85 patients were deemed viable for dosimetry analysis. SPECT lung shunt fractions (LSFs) yielded greater values than planar imaging when LSFs were <4.89%, whereas planar imaging was greater than SPECT when LSFs were >4.89. Planar to SPECT/CT dose safety conversions were 0.76 ×, 0.70 ×, and 0.55 × for the whole liver, normal liver, and lungs, respectively. Patients with SPECT LSFs <4.89% were safely treated with the direct application of planar lung dose limits. Activity calculations with SPECT/CT were greater than the body surface area method by a median of 33.1% to 61.9% and were lower than planar-based activity calculations by 12.5% to 13.7% for the whole liver and by 29.4% to 32.2% for the normal liver. A generalized method to establish safety dose limits between 2 modalities was used to translate safety dose limits from planar imaging to 99m Tc-MAA SPECT/CT. An accurate 99m Tc-MAA SPECT/CT treatment protocol was developed guided by the current knowledge in the field. Established SPECT/CT dose limits safely treated 97.5% of patients and permitted the application of independent pretreatment planning with 99m Tc-MAA SPECT/CT. [ABSTRACT FROM AUTHOR]