Joe J. Barfett, Presenter: Nothing to Disclose

Christian Kloeters MD, Abstract Co-Author: Nothing to Disclose

Nivethan Velauthapillai, Abstract Co-Author: Nothing to Disclose

Jeff Jaskolka, Abstract Co-Author: Nothing to Disclose

Critical limb ischemia is a significant cause of morbidity and mortality in the diabetic population. The goal of this study was to examine the potential of volumetric CT perfusion of the feet for demonstration of vascular compromise.

With informed consent, 16 healthy male subjects, aged 25-50 underwent dynamic 4D CT perfusion of their feet on a 320 detector CT scanner with 70cc's of IV contrast. 8 patients were scanned with a blood pressure cuff inflated around the left calf (4 subjects at 120 mmHg, 4 at 200mmHg) to simulate large vessel obstruction. After defining a posterior tibial arterial input function (AIF), a time-enhancement curve for the soft tissues of the entire foot was created. The perfusion index (PI) was obtained by dividing the maximum slope of the tissue enhancement curve by the peak of the AIF. Ratios of PIs and maximum slopes were defined as greater/lesser value in the unobstructed group and right/left foot in subjects with left-sided obstruction.

Normal subjects demonstrated an average PI ratio of 1.3 +/- 0.3 and maximum slope ratio of 1.3 +/- 0.2. Patients with 120mmHg circumferential pressure applied to the left calf demonstrated an average PI ratio of 0.7 +/- 0.1 and slope ratio of 1.3 +/- 0.2. Patients with 200mmHg of pressure applied to the left calf did not show appropriate AIFs for calculation of perfusion index. The ratio of maximum slopes at 200mmHg was 4.6 +/- 2.6. Difference in slope was statistically significant (p=0.05) between the 200mmHg and 120mmHg groups and the 200mmHg and unobstructed groups.

The PI ratio in patients with 120mmHg of vascular obstruction was paradoxically decreased due to the decrease in peak density of the AIF with relative preservation of tissue enhancement, resulting in an overall decrease of the PI on the “obstructed” side. Maximum slope of tissue enhancement was, however, successfully used as a surrogate measure of decreased perfusion in all subjects. This approach is not dependent upon the presence of visible or uncalcified large blood vessels and discriminates between normal, mild and severe vascular compromise, making it feasible for use in the diabetic population.

CT perfusion may potentially be applied to the ischemic lower limb of diabetic patients, both to gauge severity of disease and evaluate response to medical, endovascular or surgical treatment.

Barfett, J, Kloeters, C, Velauthapillai, N, Jaskolka, J, CT Perfusion of the Lower Limb Using a 4D Volumetric Approach on a 320 Detector Scanner Discriminates Normal versus Ischemic States.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9010568.html