Personalized predictive lung dosimetry by technetium-99m macroaggregated albumin SPECT/CT for yttrium-90 radioembolization

Background:
For yttrium-90 (90Y) radioembolization, the common practice of assuming a standard 1,000-g lung mass for predictive dosimetry is fundamentally incongruent with the modern philosophy of personalized medicine. We recently developed a technique of personalized predictive lung dosimetry using technetium-99m (99mTc) macroaggregated albumin (MAA) single photon emission computed tomography with integrated CT (SPECT/CT) of the lung as part of our routine dosimetric protocol for 90Y radioembolization. Its rationales are the technical superiority of SPECT/CT over planar scintigraphy, ease and convenience of lung auto-segmentation CT densitovolumetry, and dosimetric advantage of patient-specific lung parenchyma masses.
Methods:
This is a retrospective study of our pulmonary clinical outcomes and comparison of lung dosimetric accuracy and precision by 99mTc MAA SPECT/CT versus conventional planar methodology. 90Y resin microspheres (SIR-Spheres) were used for radioembolization. Diagnostic CT densitovolumetry was used as a reference for lung parenchyma mass. Pulmonary outcomes were based on follow-up diagnostic CT chest or X-ray.
Results:
Thirty patients were analyzed. The mean lung parenchyma mass of our Southeast Asian cohort was 822???103?g standard deviation (95% confidence interval 785 to 859?g). Patient-specific lung parenchyma mass estimation by CT densitovolumetry on 99mTc MAA SPECT/CT is accurate (bias ?21.7?g) and moderately precise (95% limits of agreement ?194.6 to +151.2?g). Lung mean radiation absorbed doses calculated by 99mTc MAA SPECT/CT and planar methodology are both accurate (bias <0.5?Gy), but 99mTc MAA SPECT/CT offers better precision over planar methodology (95% limits of agreement ?1.76 to +2.40?Gy versus ?3.48 to +3.31?Gy, respectively). None developed radiomicrosphere pneumonitis when treated up to a lung mean radiation absorbed dose of 18?Gy at a median follow-up of 4.4?months. Conclusions: Personalized predictive lung dosimetry by 99mTc MAA SPECT/CT is clinically feasible, safe, and more precise than conventional planar methodology for 90Y radioembolization radiation planning.

Source: http://www.ejnmmires.com/content/4/1/33

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