Increased Renal Oxygenation and Angiotensin Converting Enzyme Inhibition
Condition: Renal Disease
MeSH terms: Kidney Diseases
Study type: Interventional
Phase: Phase 4

Summary: 
      It is well established that renal hypoxia is associated with the development of renal injury.
      The purpose of this study is measure the alterations in renal blood oxygenation after
      angiotensin II converting enzyme inhibition. The understanding of kidney adaptive mechanisms
      to renin angiotensin system effects in healthy subjects will be useful for the early
      detection of renal disease and for the development of new therapies to decrease the
      progression of the disease and its consequences.
    

Detailed description: 
      Subjects The study will be conducted under a protocol (number 4111/08) approved by the Ethics
      Committee of the Instituto de Cardiologia do Rio Grande do Sul-Fundação Universitária de
      Cardiologia/Brazil. After giving their informed consent,the patients will participate in the
      study. None of the subjects will take medication,food and water overnight. All measurements
      will be performed at the end of the morning.

      After control BOLD-MRI measurements acquisition, subjects will take an oral ACE inhibitor
      (captopril 25 mg). Thirty minutes after captopril administration, without moving from the
      scanner, blood pressure will be measured and a second BOLD acquisition will be performed to
      detect a possible alteration in the renal oxygenation. Data will be collected by two
      radiologists and interpreted by a physician and a physiologist.

      MR Imaging Technique Images were acquired using 1.5T HDx (Sigma, GE Healthcare, Waukesha,
      Win) and an 8 channels body coil.

      Localizer images will be performed with axial and sagittal planes following the long axis of
      both kidneys, using breath hold and fast spoiled gradient echo (FSPGR) technique.

      Oblique axial and coronal reference images will be acquired for color maps following
      approximately the short and long axis of both kidneys using FSPGR with the following
      parameters: FOV=40cm, matrix 256x128, slice thickness=5cm, slice gap 6cm, 3 slices per plane
      in one breath hold. TR=150ms, TE=min full, FLIP=90, rBW=62KHz, 1NEX. This sequence provides
      an excellent contrast between cortex and medulla and avoid the unnecessary use of a contrast
      agents.

      BOLD sensitive images will be acquired using the multiple echo FGRE sequence with the same
      geometrical parameters. The reference images considered will have the following parameters:
      TR = 60ms, FLIP=30, rBW=60KHz, 16 echoes from TE=2.1ms until 49.6ms, echo interval of 3.2ms,
      1 NEX.

      BOLD imaging Data Processing Bold image processing will be performed using the Function R2*
      module for R2*/T2* fitting, assuming single exponential decay without constant offset at
      AW4.3 (GE Healthcare).

      For visualization and quantification, R2* parametric maps will be generated for each
      slice.(11, 18-19) A Puh Talium color table will be used, since it was a dynamic range with
      minimum value set at 7.0/sec and maximum value at 23/sec. Color will be ranged from blue to
      red, close to minimum R2* and below and close to maximum R2* and above, respectively. The
      green/yellow will be assumed as intermediate. When a position mismatch due to a different
      breath hold state, anatomical fat suppressed FSPGR images were used as transparent references
      over a parametric map or original BOLD images.

      One slice out of three, which provided the best differentiation between cortex and medulla
      and minimum partial volume, will be selected for quantification. A total of 6 regions of
      interest (ROI) with a 9 pixel size were used, 3 positioned at the cortex and 3 at the medulla
      for each plane.

      The ROIs will be positioned at the cortex according to the anatomical reference image (light
      gray) and blue on the parametric map. The ROIs will be positioned at the medulla using either
      the anatomical reference image (dark gray) or the parametric map that showed a green, yellow
      and red gradient (figure 1). Areas with susceptibility artifacts, such as bowel gas or areas
      with renal hilum vessels, will be avoided.

      Data analysis The statistical analysis will be determined by variance test for three repeated
      measures (ANOVA). Data are presented as the mean ± SD. P<0.05 will be considered
      statistically significant.
    

Intervention name(s): captopril 25mg
Intervention type(s): Drug
Intervention description(s): renal blood oxygenation after captopril
Other intervention name(s): BOLD-MRI
Intervention MeSH terms: Captopril
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Health Services Research
Keywords: ECA; BOLD-MRI; kidney