title: Computed diffusion-weighted MR imaging may improve tumor detection.
abstract: OBJECTIVE
  To describe computed diffusion weighted (DW) magnetic resonance (MR) imaging as a method for obtaining high-b-value images from DW MR imaging performed at lower b values and to investigate the feasibility of the technique to improve lesion detection in oncologic cases.
  
  
  METHODS
  The study was approved by the institutional and research committee, and written informed consent was obtained from all patients. DW MR imaging was performed on a CuSO(4) phantom at 1.5 T with a range of b values and compared with computed DW MR imaging images synthesized from lower b values (0 and 600 sec/mm(2)). The signal-to-noise ratio (SNR) was compared, and agreement between the SNR of computed DW MR imaging and theoretical estimation assessed. Computed DW MR imaging was evaluated in 10 oncologic patients who underwent whole-body DW MR imaging with b values of 0 and 900 sec/mm(2). Computed DW MR images at computed b values of 1500 and 2000 sec/mm(2) were generated. The image quality and background suppression of acquired and computed images were rated by a radiologist using a four-point scale. The diagnostic performance for malignant lesion detection using these images was evaluated and compared by using the McNemar Test.
  
  
  RESULTS
  The SNR of computed DW MR imaging of the phantom conformed closely to theoretical predictions. Computed DW MR imaging resulted in a higher SNR compared with acquired DW MR imaging, especially at b values greater than 840 sec/mm(2). In patients, images with a computed b value of 2000 sec/mm(2) produced good image quality and high background suppression (mean scores of 2.8 and 4.0, respectively). Evaluation of images with a computed b value of 2000 sec/mm(2) resulted in higher overall diagnostic sensitivity (96.0%) and specificity (96.6%) compared with images with an acquired b value of 900 sec/mm(2) (sensitivity, 89.4%; specificity, 87.5%; P < .01).
  
  
  CONCLUSIONS
  Computed DW MR imaging in the body allows higher-b-value images to be obtained with a good SNR. Clinical computed DW MR imaging is feasible and may improve disease detection.
  
  
  BACKGROUND
  http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101919/-/DC1.
authors.affiliation: Cancer Research UK and Engineering and Physical Sciences Research Council Cancer Imaging Centre, Institute of Cancer Research and Royal Marsden Hospital, Downs Rd, Sutton, Surrey SM2 5PT, England.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Blackledge
authors.forename: Martin O
authors.initials: MO
authors.lastname: Leach
authors.forename: David J
authors.initials: DJ
authors.lastname: Collins
authors.forename: Dow-Mu
authors.initials: DM
authors.lastname: Koh
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000175:diagnosis*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008223:Lymphoma / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D011471:Prostatic Neoplasms / Q000175:diagnosis*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D051598:Whole Body Imaging