Functional renal perfusion imaging with colour mapping: is it a useful adjunct to spiral CT of in the assessment of abdominal aortic aneurysm (AAA)?
OBJECTIVE
To ensure optimal timing with pre-operative spiral CT for abdominal aortic aneurysms (AAA), an initial 'timing' single level CT is commonly performed with a small bolus of contrast. This can be exploited to obtain adjunct functional information on renal perfusion. We have investigated the potential of this to measure renal perfusion, to produce colour renal perfusion maps and to predict surgical outcome in infrarenal aortic aneurysm assessment.


METHODS
We studied 21 patients being assessed for repair of infrarenal AAA. Prior to the spiral CT, a single level through the renal hili and aorta was scanned after the intravenous injection of 25 ml of contrast given at 10 ml/s. Ten 1 s duration scans were performed from 8 to 30 s after injection. Optimal timing for CT angiography can then be determined. Time-density curves were then drawn for both kidneys and aorta using regions of interest (ROIs) or pixel-by-pixel analysis. Renal cortical perfusion was measured using both ROI analysis and pseudocolour perfusion images. Following previous work, perfusion was calculated as the peak upslope of the tissue time density curve divided by peak aortic enhancement.


RESULTS
Cortical mean perfusion averaged 2.48 ml/min per ml (range 0.8-3.7 ml/min per ml n = 34) and the values obtained agreed with literature expectations. Follow up in the 10 patients proceeding to AAA repair suggest low mean perfusion values and predict a raised postoperative creatinine (P < 0.05)


CONCLUSIONS
Additional functional data and imaging can be obtained from the initial timing scan of a CT study, without requiring a dedicated study.
Blomley
M J
MJ
Department of Radiology, Hammersmith Hospital, London, UK. m.bromley@rpms.ac.uk
McBride
A
A
Mohammedtagi
S
S
Albrecht
T
T
Harvey
C J
CJ
Jäger
R
R
Standfield
N J
NJ
Dawson
P
P
D000368:Aged; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging* / Q000601:surgery; D003287:Contrast Media; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D012079:Renal Circulation; D014057:Tomography, X-Ray Computed
D003287:Contrast Media