title: Comparison of calculated and acquired high b value diffusion-weighted imaging in prostate cancer.
abstract: OBJECTIVE
  To determine whether the performance of calculated high b value diffusion-weighted images (DWI) derived from regular lower b value DWI using exponential diffusion decay models (intravoxel incoherent motion = IVIM and diffusional kurtosis = DK) is comparable to acquired high b value DWI in prostate cancer detection.
  
  
  METHODS
  One hundred six patients underwent diagnostic multiparametric prostate MRI at 3T using an endorectal coil. Five b value (b = 0, 188, 375, 563, 750 s/mm(2)) DWI and high b value (b = 0, 1000 and 2000 s/mm(2)) DWI were acquired. Calculated high b value (b = 1000 s/mm(2) and b = 2000 s/mm(2)) DWI were derived from the DWI dataset using DK and IVIM models. Calculated and acquired high b value DWI images were compared for lesion visibility and image quality by two experienced radiologists (1 and 6 years of experience). GEE with Wald test was used to compare the image quality among the four calculated high b value DWI by comparing the proportion of lesions in each model which were comparable to the acquired images. This comparison was done for all lesions and by lesion location (PZ or CG; low apical/anterior or apical/mid/base)
  
  
  RESULTS
  More lesions were visible on acquired b = 2000 s/mm(2) compared to b = 1000 s/mm(2) DWI. Calculated high b value DWI using the IVIM model had approximately the same number of lesions as acquired high b value DWI, whereas the DK model had fewer lesions than acquired images. The image quality of calculated high b value DWI was comparable to that of acquired images, and the highest quality images were obtained with b1000IVIM. The image quality of calculated b1000IVIM was the same as that of acquired DWI in apical/mid/base (98%) locations and comparable in low apical and anterior (95.4%) locations. The image quality of calculated b2000IVIM was inferior in both apical/mid/base (86.2%) locations and comparable in low apical and anterior (83.9%) locations.
  
  
  CONCLUSIONS
  Calculated high b value DWI obtained using IVIM model has same lesion visibility as that of acquired DWI. The image quality of calculated high b value DWI relative to corresponding acquired DWI decreases with increase in b value.
authors.affiliation: Molecular Imaging Program, National Cancer Institute (NCI), NIH 10 Center Dr, MSC 1182, Bldg 10, Room B3B85, Bethesda, MD, 20892-1088, USA.
authors.forename: Kinzya B
authors.initials: KB
authors.lastname: Grant
authors.forename: Harsh K
authors.initials: HK
authors.lastname: Agarwal
authors.forename: Joanna H
authors.initials: JH
authors.lastname: Shih
authors.forename: Marcelino
authors.initials: M
authors.lastname: Bernardo
authors.forename: Yuxi
authors.initials: Y
authors.lastname: Pang
authors.forename: Dagane
authors.initials: D
authors.lastname: Daar
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Merino
authors.forename: Bradford J
authors.initials: BJ
authors.lastname: Wood
authors.forename: Peter A
authors.initials: PA
authors.lastname: Pinto
authors.forename: Peter L
authors.initials: PL
authors.lastname: Choyke
authors.forename: Baris
authors.initials: B
authors.lastname: Turkbey
mesh_terms: D000328:Adult; D000368:Aged; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000473:pathology*; D012189:Retrospective Studies