title: (⁹⁹m)Tc-MAA overestimates the absorbed dose to the lungs in radioembolization: a quantitative evaluation in patients treated with ¹⁶⁶Ho-microspheres.
abstract: OBJECTIVE
  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 doses after (166)Ho radioembolization.
  
  
  METHODS
  This prospective clinical study included 14 patients with chemorefractory, unresectable liver metastases treated with (166)Ho radioembolization. (99m)Tc-MAA-based and (166)Ho-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 (166)Ho radioembolization.
  
  
  RESULTS
  In the phantom study, (166)Ho SPECT/CT-based lung absorbed dose estimates were more accurate (absolute error range 0.1 to -4.4 Gy) than (166)Ho 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 (166)Ho-microsphere SPECT/CT imaging. Lung absorbed doses estimated on the basis of pretreatment diagnostic (166)Ho-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 (166)Ho-microsphere planar scintigraphy (median 10.4 Gy, range 4.0 to 17.3 Gy; p < 0.001), (99m)Tc-MAA SPECT/CT imaging (median 2.5 Gy, range 1.2 to 12.3 Gy; p < 0.001), and (99m)Tc-MAA planar scintigraphy (median 5.5 Gy, range 2.3 to 18.2 Gy; p < 0.001).
  
  
  CONCLUSIONS
  In clinical practice, lung absorbed doses are significantly overestimated by pretreatment diagnostic (99m)Tc-MAA imaging. Pretreatment diagnostic (166)Ho-microsphere SPECT/CT imaging accurately predicts lung absorbed doses after (166)Ho radioembolization.
authors.affiliation: Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands.
authors.forename: Mattijs
authors.initials: M
authors.lastname: Elschot
authors.forename: Johannes F W
authors.initials: JF
authors.lastname: Nijsen
authors.forename: Marnix G E H
authors.initials: MG
authors.lastname: Lam
authors.forename: Maarten L J
authors.initials: ML
authors.lastname: Smits
authors.forename: Jip F
authors.initials: JF
authors.lastname: Prince
authors.forename: Max A
authors.initials: MA
authors.lastname: Viergever
authors.forename: Maurice A A J
authors.initials: MA
authors.lastname: van den Bosch
authors.forename: Bernard A
authors.initials: BA
authors.lastname: Zonnenberg
authors.forename: Hugo W A M
authors.initials: HW
authors.lastname: de Jong
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004621:Embolization, Therapeutic / Q000009:adverse effects / Q000379:methods*; D005260:Female; D006695:Holmium / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000627:therapeutic use; D006801:Humans; D008175:Lung Neoplasms / Q000532:radiotherapy*; D008297:Male; D008863:Microspheres; D008875:Middle Aged; D011446:Prospective Studies; D011868:Radioisotopes / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000627:therapeutic use; D019275:Radiopharmaceuticals / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000627:therapeutic use; D011879:Radiotherapy Dosage; D013668:Technetium Tc 99m Aggregated Albumin / Q000493:pharmacokinetics*; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D011868:Radioisotopes; D019275:Radiopharmaceuticals; D013668:Technetium Tc 99m Aggregated Albumin; D006695:Holmium