title: Noninvasive assessment of early kidney allograft dysfunction by blood oxygen level-dependent magnetic resonance imaging.
abstract: BACKGROUND
  Blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) is a noninvasive method to assess tissue oxygen bioavailability, using deoxyhemoglobin as an endogenous contrast agent. We hypothesized that BOLD-MRI could accurately discriminate different types of rejection early after kidney transplantation.
  
  
  METHODS
  Twenty-three patients underwent imaging in the first four months posttransplant. Five had normal functioning transplants and 18 had biopsy-proven acute allograft dysfunction (acute tubular necrosis [ATN, n=5] and acute rejection [n=13] including borderline rejection: n=3; IA rejection: n=4; IIA rejection: n=6: C4d(+) rejection: n=9).
  
  
  RESULTS
  Mean medullary R2* (MR2*) levels (a measure directly proportional to tissue deoxyhemoglobin levels) were significantly higher in normal functioning allografts (R2*=24.3/s+/-2.3) versus acute rejection (R2*=16.6/s+/-2.1) and ATN (R2*=20.9/s+/-1.8) (P<0.05). The lowest MR2* levels were observed in acute rejection episodes with vascular injury i.e. IIA and C4d (+). Similarly, the lowest medullary to cortical R2* ratios (MCR2*) were present in allografts with IIA (1.24+/-0.05) and C4d(+) rejection (1.26+/-0.06). ROC curve analyses suggested that MR2* and MCR2* values could accurately discriminate acute rejection in the early posttransplant period.
  
  
  CONCLUSIONS
  BOLD-MRI demonstrated significant changes in medullary oxygen bioavailability in allografts with biopsy-proven ATN and acute rejection, suggesting that there may be a role for this noninvasive tool to evaluate kidney function early after transplantation.
authors.affiliation: Department of Medicine, University of Wisconsin Madison, Madison, WI, USA. axd@medicine.wisc.edu
authors.forename: Arjang
authors.initials: A
authors.lastname: Djamali
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Sadowski
authors.forename: Millie
authors.initials: M
authors.lastname: Samaniego-Picota
authors.forename: Sean B
authors.initials: SB
authors.lastname: Fain
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Muehrer
authors.forename: Sara K
authors.initials: SK
authors.lastname: Alford
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Grist
authors.forename: Bryan N
authors.initials: BN
authors.lastname: Becker
mesh_terms: D000328:Adult; D001706:Biopsy; D005260:Female; D006084:Graft Rejection / Q000453:epidemiology; D006085:Graft Survival / Q000502:physiology; D006801:Humans; D007677:Kidney Function Tests; D016030:Kidney Transplantation / Q000009:adverse effects* / Q000473:pathology / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D011183:Postoperative Complications / Q000097:blood / Q000473:pathology / Q000503:physiopathology*; D014184:Transplantation, Homologous
chemical_list: D010100:Oxygen