title: A Comparison of Lumpectomy Cavity Delineations Between Use of Magnetic Resonance Imaging and Computed Tomography Acquired With Patient in Prone Position for Radiation Therapy Planning of Breast Cancer.
abstract: OBJECTIVE
  To compare lumpectomy cavity (LC) and planning target volume (PTV) delineated with the use of magnetic resonance imaging (MRI) and computed tomography (CT) and to examine the possibility of replacing CT with MRI for radiation therapy (RT) planning for breast cancer.
  
  
  METHODS
  MRI and CT data were acquired for 15 patients with early-stage breast cancer undergoing lumpectomy during RT simulation in prone positions, the same as their RT treatment positions. The LCs were delineated manually on both CT (LC-CT) and MRI acquired with 4 sequences: T1, T2, STIR, and DCE. Various PTVs were created by expanding a 15-mm margin from the corresponding LCs and from the union of the LCs for the 4 MRI sequences (PTV-MRI). Differences were measured in terms of cavity visualization score (CVS) and dice coefficient (DC).
  
  
  RESULTS
  The mean CVSs for T1, T2, STIR, DCE, and CT defined LCs were 3.47, 3.47, 3.87, 3.50. and 2.60, respectively, implying that the LC is mostly visible with a STIR sequence. The mean reductions of LCs from those for CT were 22%, 43%, 36%, and 17% for T1, T2, STIR, and DCE, respectively. In 14 of 15 cases, MRI (union of T1, T2, STIR, and DCE) defined LC included extra regions that would not be visible from CT. The DCs between CT and MRI (union of T1, T2, STIR, and DCE) defined volumes were 0.65 ± 0.20 for LCs and 0.85 ± 0.06 for PTVs. There was no obvious difference between the volumes of PTV-MRI and PTV-CT, and the average PTV-STIR/PTV-CT volume ratio was 0.83 ± 0.23.
  
  
  CONCLUSIONS
  The use of MRI improves the visibility of LC in comparison with CT. The volumes of LC and PTV generated based on a MRI sequence are substantially smaller than those based on CT, and the PTV-MRI volumes, defined by the union of T1, T2, STIR, and DCE, were comparable with those of PTV-CT for most of the cases studied.
authors.affiliation: Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Radiation Oncology, Shandong's Key Laboratory of Radiation Oncology, Shandong Cancer Hospital and Institute, Jinan, P.R. China.
authors.forename: Wei
authors.initials: W
authors.lastname: Huang
authors.affiliation: Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin.
authors.forename: Adam
authors.initials: A
authors.lastname: Currey
authors.affiliation: Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin.
authors.forename: Xiaojian
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, Shandong's Key Laboratory of Radiation Oncology, Shandong Cancer Hospital and Institute, Jinan, P.R. China.
authors.forename: Baosheng
authors.initials: B
authors.lastname: Li
authors.affiliation: Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin.
authors.forename: Carmen
authors.initials: C
authors.lastname: Bergom
authors.affiliation: Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin.
authors.forename: Tracy
authors.initials: T
authors.lastname: Kelly
authors.affiliation: Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin.
authors.forename: J Frank
authors.initials: JF
authors.lastname: Wilson
authors.affiliation: Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin. Electronic address: ali@mcw.edu.
authors.forename: X Allen
authors.initials: XA
authors.lastname: Li
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015412:Mastectomy, Segmental; D008875:Middle Aged; D056888:Patient Positioning; D016684:Prone Position; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D047368:Tumor Burden