title: Ga-68 MAA Perfusion 4D-PET/CT Scanning Allows for Functional Lung Avoidance Using Conformal Radiation Therapy Planning.
abstract: BACKGROUND
  Ga-68-macroaggregated albumin ((68)Ga-perfusion) positron emission tomography/computed tomography (PET/CT) is a novel imaging technique for the assessment of functional lung volumes. The purpose of this study was to use this imaging technique for functional adaptation of definitive radiotherapy plans in patients with non-small cell lung cancer (NSCLC).
  
  
  METHODS
  This was a prospective clinical trial of patients with NSCLC who received definitive 3-dimensional (3D) conformal radiotherapy to 60 Gy in 30 fx and underwent pretreatment respiratory-gated (4-dimensional [4D]) perfusion PET/CT. The "perfused" lung volume was defined as all lung parenchyma taking up radiotracer, and the "well-perfused" lung volume was contoured using a visually adapted threshold of 30% maximum standardized uptake value (SUV max). Alternate 3D conformal plans were subsequently created and optimized to avoid perfused and well-perfused lung volumes. Functional dose volumetrics were compared using mean lung dose (MLD), V5 (volume receiving 5 Gy or more), V10, V20, V30, V40, V50, and V60 parameters.
  
  
  RESULTS
  Fourteen consecutive patients had alternate radiotherapy plans created based on functional lung volumes. When considering the original treatment plan, the dose to perfused and well-perfused functional lung volumes was similar to that of the conventional anatomical lung volumes with an average MLD of 12.15, 12.67, and 12.11 Gy, respectively. Plans optimized for well-perfused lung improved functional V30, V40, V50, and V60 metrics (all P values <.05). The functional MLD of well-perfused lung was improved by a median of 0.86 Gy, P < .01. However, plans optimized for perfused lung only showed significant improvement in the functional V60 dose parameter (median 1.00%, P = .04) but at a detriment of a worse functional V5 (median 3.33%, P = .05).
  
  
  CONCLUSIONS
  This study demonstrates proof of principle that 4D-perfusion PET/CT may enable functional lung avoidance during treatment planning of patients with NSCLC. Radiotherapy plans adapted to well-perfused but not perfused functional lung volumes allow for reduction in dose to functional lung using 3D conformal radiotherapy.
authors.affiliation: Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria, Australia Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia shankar.siva@petermac.org.
authors.forename: Shankar
authors.initials: S
authors.lastname: Siva
authors.affiliation: Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Thomas
authors.initials: T
authors.lastname: Devereux
authors.affiliation: Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria, Australia Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: David L
authors.initials: DL
authors.lastname: Ball
authors.affiliation: Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria, Australia Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: Michael P
authors.initials: MP
authors.lastname: MacManus
authors.affiliation: Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Hardcastle
authors.affiliation: Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: Tomas
authors.initials: T
authors.lastname: Kron
authors.affiliation: Department of Biostatistics and Clinical Trials, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: Mathias
authors.initials: M
authors.lastname: Bressel
authors.affiliation: Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria, Australia Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: Farshad
authors.initials: F
authors.lastname: Foroudi
authors.affiliation: Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: Nikki
authors.initials: N
authors.lastname: Plumridge
authors.affiliation: Division of Cancer Medicine, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: Daniel
authors.initials: D
authors.lastname: Steinfort
authors.affiliation: Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: Mark
authors.initials: M
authors.lastname: Shaw
authors.affiliation: Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Jason
authors.initials: J
authors.lastname: Callahan
authors.affiliation: Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria, Australia Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Hicks
authors.affiliation: Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville, Victoria, Australia Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Hofman
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D056973:Four-Dimensional Computed Tomography; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000473:pathology; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D008875:Middle Aged; D059351:Organ Sparing Treatments; D009942:Organometallic Compounds; D055420:Perfusion Imaging; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal; D012709:Serum Albumin
chemical_list: D009942:Organometallic Compounds; D019275:Radiopharmaceuticals; D012709:Serum Albumin; C059652:gallium macroaggregated human serum albumin
keywords: 4D imaging; functional imaging; lung cancer; perfusion scintigraphy; positron emission tomography; radiation therapy PET/CT