title: Comparison of prone versus supine 18F-FDG-PET of locally advanced breast cancer: Phantom and preliminary clinical studies.
abstract: OBJECTIVE
  Previous studies have demonstrated how imaging of the breast with patients lying prone using a supportive positioning device markedly facilitates longitudinal and/or multimodal image registration. In this contribution, the authors' primary objective was to determine if there are differences in the standardized uptake value (SUV) derived from [(18)F]fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) in breast tumors imaged in the standard supine position and in the prone position using a specialized positioning device.
  
  
  METHODS
  A custom positioning device was constructed to allow for breast scanning in the prone position. Rigid and nonrigid phantom studies evaluated differences in prone and supine PET. Clinical studies comprised 18F-FDG-PET of 34 patients with locally advanced breast cancer imaged in the prone position (with the custom support) followed by imaging in the supine position (without the support). Mean and maximum values (SUVpeak and SUVmax, respectively) were obtained from tumor regions-of-interest for both positions. Prone and supine SUV were linearly corrected to account for the differences in 18F-FDG uptake time. Correlation, Bland-Altman, and nonparametric analyses were performed on uptake time-corrected and uncorrected data.
  
  
  RESULTS
  SUV from the rigid PET breast phantom imaged in the prone position with the support device was 1.9% lower than without the support device. In the nonrigid PET breast phantom, prone SUV with the support device was 5.0% lower than supine SUV without the support device. In patients, the median (range) difference in uptake time between prone and supine scans was 16.4 min (13.4-30.9 min), which was significantly-but not completely-reduced by the linear correction method. SUVpeak and SUVmax from prone versus supine scans were highly correlated, with concordance correlation coefficients of 0.91 and 0.90, respectively. Prone SUVpeak and SUVmax were significantly lower than supine in both original and uptake time-adjusted data across a range of index times (P < < 0.0001, Wilcoxon signed rank test). Before correcting for uptake time differences, Bland-Altman analyses revealed proportional bias between prone and supine measurements (SUVpeak and SUVmax) that increased with higher levels of FDG uptake. After uptake time correction, this bias was significantly reduced (P < 0.01). Significant prone-supine differences, with regard to the spatial distribution of lesions relative to isocenter, were observed between the two scan positions, but this was poorly correlated with the residual (uptake time-corrected) prone-supine SUVpeak difference (P = 0.78).
  
  
  CONCLUSIONS
  Quantitative 18F-FDG-PET/CT of the breast in the prone position is not deleteriously affected by the support device but yields SUV that is consistently lower than those obtained in the standard supine position. SUV differences between scans arising from FDG uptake time differences can be substantially reduced, but not removed entirely, with the current correction method. SUV from the two scan orientations is quantitatively different and should not be assumed equivalent or interchangeable within the same subject. These findings have clinical relevance in that they underscore the importance of patient positioning while scanning as a clinical variable that must be accounted for with longitudinal PET measurement, for example, in the assessment of treatment response.
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee 37232 and Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee 37232.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Williams
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee 37232 and Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee 37232.
authors.forename: Sudheer D
authors.initials: SD
authors.lastname: Rani
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee 37232 and Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee 37232.
authors.forename: Xia
authors.initials: X
authors.lastname: Li
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee 37232.
authors.forename: Lori R
authors.initials: LR
authors.lastname: Arlinghaus
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington 98195.
authors.forename: Tzu-Cheng
authors.initials: TC
authors.lastname: Lee
authors.affiliation: Department of Radiology, University of Washington, Seattle, Washington 98195.
authors.forename: Lawrence R
authors.initials: LR
authors.lastname: MacDonald
authors.affiliation: Department of Radiology, University of Washington, Seattle, Washington 98195.
authors.forename: Savannah C
authors.initials: SC
authors.lastname: Partridge
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee 37232 and Department of Biostatistics, Vanderbilt University, Nashville, Tennessee 37232.
authors.forename: Hakmook
authors.initials: H
authors.lastname: Kang
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee 37232 and Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee 37232.
authors.forename: Jennifer G
authors.initials: JG
authors.lastname: Whisenant
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee 37232 and Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee 37232.
authors.forename: Richard G
authors.initials: RG
authors.lastname: Abramson
authors.affiliation: Department of Medical Oncology, University of Washington, Seattle, Washington 98195.
authors.forename: Hannah M
authors.initials: HM
authors.lastname: Linden
authors.affiliation: Department of Radiology, University of Washington, Seattle, Washington 98195; Department of Bioengineering, University of Washington, Seattle, Washington 98195; Department of Physics, University of Washington, Seattle, Washington 98195; and Department of Electrical Engineering, University of Washington, Seattle, Washington 98195.
authors.forename: Paul E
authors.initials: PE
authors.lastname: Kinahan
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee 37232; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee 37232; Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee 37232; Department of Physics, Vanderbilt University, Nashville, Tennessee 37232; and Department of Cancer Biology, Vanderbilt University, Nashville, Tennessee 37232.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Yankeelov
mesh_terms: D000328:Adult; D000368:Aged; D001940:Breast / Q000000981:diagnostic imaging / Q000503:physiopathology; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000503:physiopathology; D004867:Equipment Design; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008137:Longitudinal Studies; D008327:Mammography / Q000295:instrumentation / Q000379:methods; D008875:Middle Aged; D008954:Models, Biological; D064847:Multimodal Imaging / Q000295:instrumentation / Q000379:methods; D056888:Patient Positioning / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000295:instrumentation / Q000379:methods*; D016684:Prone Position; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D016683:Supine Position; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18