title: BOLD imaging: a potential predictive biomarker of renal functional outcome following revascularization in atheromatous renovascular disease.
abstract: BACKGROUND
  Stenting of the stenosed renal artery is commonly employed in atheromatous renovascular disease (ARVD) in order to revascularize the affected kidney. However, it is still far from clear which patient subgroups should be revascularized as stenting carries small but significant risks. We have previously demonstrated that the ratio of magnetic resonance-measured renal volume to isotopic single kidney glomerular filtration rate (isoSK-GFR) is higher in kidneys which show functional improvement after revascularization. Blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) does not require contrast administration and is sensitive to changes in tissue concentration of deoxyhaemoglobin.
  
  
  METHODS
  In this study, we test the hypothesis that baseline BOLD R2* map signal and R2*:isoSK-GFR ratio will provide an additional independent predictive biomarker of response to revascularization.
  
  
  RESULTS
  Studies were performed in 28 subjects (16 ARVD and 12 controls). All subjects had R2* mapping and isoSK-GFR measured at baseline and at 4-month follow-up. MRI data were collected on a 3 T whole-body MRI scanner using a coronal dual-echo, 2D gradient-echo breath-hold acquisition. Parenchymal regions of interest (ROIs) were drawn on a representative slice through the middle of the kidney. Parametric maps of R2* were generated and mean values of R2* were calculated for every ROI. The ratio of R2*:isoSK-GFR at baseline was significantly greater in kidneys where renal function improved (5.91 ± 6.51) versus stable (1.78 ± 1.11), deteriorated (2.15 ± 1.79) or controls (1.5 ± 0.91), P = 0.003. R2*:isoSK-GFR ratio that was greater than 95% confidence interval of the control kidneys was 66.7% sensitive, but 85.7% specific in predicting a positive renal functional outcome.
  
  
  CONCLUSIONS
  These pilot data show that BOLD R2* imaging, presumably by detecting intra-renal deoxyhaemoglobin in still viable 'hibernating' parenchyma, coupled with isoSK-GFR may provide an effective predictive biomarker for positive renal functional response to revascularization. R2* imaging is non-invasive, quick to perform and could provide further insight into reversible parenchymal changes in ARVD kidneys.
authors.affiliation: The University of Manchester, Manchester Academic Health Science Centre, Salford Royal Hospital, Salford, UK. tinachrys@doctors.org.uk
authors.forename: Constantina
authors.initials: C
authors.lastname: Chrysochou
authors.forename: Iosif A
authors.initials: IA
authors.lastname: Mendichovszky
authors.forename: David L
authors.initials: DL
authors.lastname: Buckley
authors.forename: Ching M
authors.initials: CM
authors.lastname: Cheung
authors.forename: Alan
authors.initials: A
authors.lastname: Jackson
authors.forename: Philip A
authors.initials: PA
authors.lastname: Kalra
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D050197:Atherosclerosis / Q000150:complications* / Q000473:pathology*; D016022:Case-Control Studies; D002908:Chronic Disease; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000098:blood supply* / Q000503:physiopathology; D007674:Kidney Diseases / Q000097:blood / Q000209:etiology* / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D010865:Pilot Projects; D011379:Prognosis; D012307:Risk Factors; D015607:Stents
chemical_list: D010100:Oxygen