99mTc-MAA overestimates the absorbed dose to the lungs in radioembolization: a quantitative evaluation in patients treated with 166Ho-microspheres
European journal of nuclear medicine and molecular imaging, 2014•Springer
Purpose Radiation pneumonitis is a rare but serious complication of radioembolic therapy of
liver tumours. Estimation of the mean absorbed dose to the lungs based on pretreatment
diagnostic 99m Tc-macroaggregated albumin (99m Tc-MAA) imaging should prevent this,
with administered activities adjusted accordingly. The accuracy of 99m Tc-MAA-based lung
absorbed dose estimates was evaluated and compared to absorbed dose estimates based
on pretreatment diagnostic 166 Ho-microsphere imaging and to the actual lung absorbed …
liver tumours. Estimation of the mean absorbed dose to the lungs based on pretreatment
diagnostic 99m Tc-macroaggregated albumin (99m Tc-MAA) imaging should prevent this,
with administered activities adjusted accordingly. The accuracy of 99m Tc-MAA-based lung
absorbed dose estimates was evaluated and compared to absorbed dose estimates based
on pretreatment diagnostic 166 Ho-microsphere imaging and to the actual lung absorbed …
Purpose
Radiation pneumonitis is a rare but serious complication of radioembolic therapy of liver tumours. Estimation of the mean absorbed dose to the lungs based on pretreatment diagnostic 99mTc-macroaggregated albumin (99mTc-MAA) imaging should prevent this, with administered activities adjusted accordingly. The accuracy of 99mTc-MAA-based lung absorbed dose estimates was evaluated and compared to absorbed dose estimates based on pretreatment diagnostic 166Ho-microsphere imaging and to the actual lung absorbed doses after 166Ho radioembolization.
Methods
This prospective clinical study included 14 patients with chemorefractory, unresectable liver metastases treated with 166Ho radioembolization. 99mTc-MAA-based and 166Ho-microsphere-based estimation of lung absorbed doses was performed on pretreatment diagnostic planar scintigraphic and SPECT/CT images. The clinical analysis was preceded by an anthropomorphic torso phantom study with simulated lung shunt fractions of 0 to 30 % to determine the accuracy of the image-based lung absorbed dose estimates after 166Ho radioembolization.
Results
In the phantom study, 166Ho SPECT/CT-based lung absorbed dose estimates were more accurate (absolute error range 0.1 to −4.4 Gy) than 166Ho planar scintigraphy-based lung absorbed dose estimates (absolute error range 9.5 to 12.1 Gy). Clinically, the actual median lung absorbed dose was 0.02 Gy (range 0.0 to 0.7 Gy) based on posttreatment 166Ho-microsphere SPECT/CT imaging. Lung absorbed doses estimated on the basis of pretreatment diagnostic 166Ho-microsphere SPECT/CT imaging (median 0.02 Gy, range 0.0 to 0.4 Gy) were significantly better predictors of the actual lung absorbed doses than doses estimated on the basis of 166Ho-microsphere planar scintigraphy (median 10.4 Gy, range 4.0 to 17.3 Gy; p < 0.001), 99mTc-MAA SPECT/CT imaging (median 2.5 Gy, range 1.2 to 12.3 Gy; p < 0.001), and 99mTc-MAA planar scintigraphy (median 5.5 Gy, range 2.3 to 18.2 Gy; p < 0.001).
Conclusion
In clinical practice, lung absorbed doses are significantly overestimated by pretreatment diagnostic 99mTc-MAA imaging. Pretreatment diagnostic 166Ho-microsphere SPECT/CT imaging accurately predicts lung absorbed doses after 166Ho radioembolization.
Springer
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