title: Lung dose calculation with SPECT/CT for ⁹⁰Yittrium radioembolization of liver cancer.
abstract: OBJECTIVE
  To propose a new method to estimate lung mean dose (LMD) using technetium-99m labeled macroaggregated albumin ((99m)Tc-MAA) single photon emission CT (SPECT)/CT for (90)Yttrium radioembolization of liver tumors and to compare the LMD estimated using SPECT/CT with clinical estimates of LMD using planar gamma scintigraphy (PS).
  
  
  METHODS
  Images of 71 patients who had SPECT/CT and PS images of (99m)Tc-MAA acquired before TheraSphere radioembolization of liver cancer were analyzed retrospectively. LMD was calculated from the PS-based lung shunt assuming a lung mass of 1 kg and 50 Gy per GBq of injected activity shunted to the lung. For the SPECT/CT-based estimate, the LMD was calculated with the activity concentration and lung volume derived from SPECT/CT. The effect of attenuation correction and the patient's breathing on the calculated LMD was studied with the SPECT/CT. With these effects correctly taken into account in a more rigorous fashion, we compared the LMD calculated with SPECT/CT with the LMD calculated with PS.
  
  
  RESULTS
  The mean dose to the central region of the lung leads to a more accurate estimate of LMD. Inclusion of the lung region around the diaphragm in the calculation leads to an overestimate of LMD due to the misregistration of the liver activity to the lung from the patient's breathing. LMD calculated based on PS is a poor predictor of the actual LMD. For the subpopulation with large lung shunt, the mean overestimation from the PS method for the lung shunt was 170%.
  
  
  CONCLUSIONS
  A new method of calculating the LMD for TheraSphere and SIR-Spheres radioembolization of liver cancer based on (99m)Tc-MAA SPECT/CT is presented. The new method provides a more accurate estimate of radiation risk to the lungs. For patients with a large lung shunt calculated from PS, a recalculation of LMD based on SPECT/CT is recommended.
authors.affiliation: Department of Radiation Oncology, Cleveland Clinic, Cleveland, OH, USA. yun@ccf.org
authors.forename: Naichang
authors.initials: N
authors.lastname: Yu
authors.forename: Shaym M
authors.initials: SM
authors.lastname: Srinivas
authors.forename: Frank P
authors.initials: FP
authors.lastname: Difilippo
authors.forename: Sankaran
authors.initials: S
authors.lastname: Shrikanthan
authors.forename: Abraham
authors.initials: A
authors.lastname: Levitin
authors.forename: Gordon
authors.initials: G
authors.lastname: McLennan
authors.forename: James
authors.initials: J
authors.lastname: Spain
authors.forename: Ping
authors.initials: P
authors.lastname: Xia
authors.forename: Allan
authors.initials: A
authors.lastname: Wilkinson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000379:methods*; D006528:Carcinoma, Hepatocellular / Q000532:radiotherapy / Q000556:secondary; D004621:Embolization, Therapeutic / Q000379:methods; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000532:radiotherapy* / Q000556:secondary; D008168:Lung / Q000000981:diagnostic imaging* / Q000528:radiation effects*; D008297:Male; D008875:Middle Aged; D009068:Movement; D064847:Multimodal Imaging / Q000379:methods*; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D012119:Respiration; D012189:Retrospective Studies; D013668:Technetium Tc 99m Aggregated Albumin; D014057:Tomography, X-Ray Computed; D015021:Yttrium Radioisotopes / Q000008:administration & dosage*
chemical_list: D019275:Radiopharmaceuticals; D013668:Technetium Tc 99m Aggregated Albumin; D015021:Yttrium Radioisotopes