title: Intravoxel Incoherent Motion Magnetic Resonance Imaging in Partially Nephrectomized Kidneys.
abstract: OBJECTIVE
  The aim of this study was to investigate the effects of partial nephrectomy (PN) in kidneys with solid renal masses on the apparent diffusion coefficient (ADC) and on intravoxel incoherent motion (IVIM)-based parameters using diffusion-weighted magnetic resonance imaging (DWI).
  
  
  METHODS
  Fifteen patients with renal masses underwent DWI before and 1 week after PN on a clinical 3 T scanner using a single-shot echo planar imaging sequence with 10 diffusion weightings. Motion-corrected images were quantified using a monoexponential model fit to calculate ADCs and a segmented biexponential fit to calculate IVIM parameters f (perfusion fraction), Dslow and Dfast ("slow" and "fast" diffusion coefficients), as well as the pseudoflow (PF) Dfast × f. The median values derived from multislice (minimum of 3 slices) regions of interest encompassing the kidney cortex were used for statistical analysis. Estimated glomerular filtration rate values were calculated based on serum creatinine levels on each examination day using the Modification of Diet in Renal Disease formula.
  
  
  RESULTS
  The follow-up measurement yielded significantly lower values in the partially nephrectomized kidneys compared with contralateral kidneys for the parameters ADC (P = 0.002), Dfast (P = 0.43), f (P = 0.001), and PF (P = 0.0008). Comparing baseline and follow-up, partially nephrectomized kidneys showed a significant decrease for ADC (P = 0.01), Dfast (P = 0.43), f (P = 0.002), and PF (P = 0.002). Nonnephrectomized kidneys expressed a significant increase for ADC (P = 0.01) and PF (P = 0.01). Follow-up Modification of Diet in Renal Disease showed positive correlations with all DWI parameters in the partially nephrectomized kidneys (ADC: r(2) = 0.63, P = 0.0004; Dfast: r(2) = 0.59, P = 0.0009; f: r(2) = 0.36, P = 0.018; PF: r(2) = 0.60, P = 0.00075) except for Dslow.
  
  
  CONCLUSIONS
  Our study suggests that quantitative parameters derived from DWI are highly indicative of renal function. Apparent diffusion coefficients showed substantial differences in the renal cortex after PN, whereas an IVIM analysis delivered additional insight into kidney physiology. Quantitative DWI, particularly perfusion-related IVIM parameters, therefore demonstrated great potential as truly noninvasive biomarker to obtain information about single kidney function.
authors.affiliation: From the *Josef Lissner Laboratory for Biomedical Imaging, Institute for Clinical Radiology, †Institute for Clinical Radiology, and ‡Department of Urology, Ludwig-Maximilians-University Hospital Munich, Munich; and §Department of Diagnostic and Interventional Radiology, University Hospital Tübingen, Tübingen, Germany.
authors.forename: Moritz Jörg
authors.initials: MJ
authors.lastname: Schneider
authors.forename: Olaf
authors.initials: O
authors.lastname: Dietrich
authors.forename: Michael
authors.initials: M
authors.lastname: Ingrisch
authors.forename: Andreas
authors.initials: A
authors.lastname: Helck
authors.forename: Katharina Stella
authors.initials: KS
authors.lastname: Winter
authors.forename: Maximilian F
authors.initials: MF
authors.lastname: Reiser
authors.forename: Michael
authors.initials: M
authors.lastname: Staehler
authors.forename: Jozefina
authors.initials: J
authors.lastname: Casuscelli
authors.forename: Mike
authors.initials: M
authors.lastname: Notohamiprodjo
mesh_terms: D015331:Cohort Studies; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007674:Kidney Diseases / Q000000981:diagnostic imaging* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009392:Nephrectomy