Dynamic CT Measurement of Cerebral Blood Flow: A Validation Study
,
Aleksa Cenica,
Darius G. Nabavia,
Rosemary A. Craena,
Adrian W. Gelba and
Ting-Yim Lee,a
a From the Imaging Research Laboratories, John P. Robarts Research Institute (A.C., D.G.N., T-Y.L.); the Medical Biophysics Department, The University of Western Ontario (A.C., T-Y.L.); the Lawson Research Institute, St Joseph's Health Centre, (A.C., T-Y.L.); and the Department of Anaesthesia, University Campus, London Health Sciences Centre (R.A.C., A.W.G.), London, Ontario, Canada.
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FIG 1. A, Example of the impulse residue function of the brain, R(t), obtained by deconvolution of Ca(t) and Q(t) in B, illustrating the expected general shape.
B, Examples of arterial, Ca(t) (closed circles), and regional brain tissue, Q(t) (open circles), contrast-enhancement curves obtained from dynamic CT scanning.
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FIG 2. Axial CT scan of the PE tubes phantom used to correct for PVA. PE tubes on the left contain 40 mL of distilled water with 2.7 mL of Isovue 300 (300 mg I/mL contrast material) added. PE tubes on the right contain only distilled water to serve as background (ie, unenhanced). A two-pixel-radius ROI was drawn in the center of each tube, and the mean CT number was determined within these circular ROIs
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FIG 3. Contrast-enhanced coronal CT scan of a rabbit. Two parietal ROIs of similar size and one central region in the basal ganglia, as shown on the image, were used for all measurements of rCBF. An ear artery (EA) was used to measure the arterial enhancement curve. The postcommunicating arteries (in the middle of the brain) and the internal carotid arteries (ICA) are also visible
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FIG 4. A, Background-subtracted image profile of a PE-160 tube with the fitted gaussian curve. The calculated gaussian SD was 2.58 for the known inner diameter of 1.14 mm.
B, Background-subtracted image profile of a rabbit ear artery with the fitted gaussian curve. The calculated gaussian SD was 2.58, corresponding to an estimated inner diameter of about 1.14 mm for the ear artery.
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FIG 5. Results of the PE tubes phantom experiments.
A, A significant linear correlation was found between the gaussian SDs and the inner diameters of the PE tubes (r =. 998, P < .001).
B, PVSF calibration curve obtained from the PE tubes phantom (fig 2). A significant exponential correlation was found between PVSF and gaussian SDs for the PE tubes (r =. 996, P < .001).
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FIG 6. Dynamic CT measurements plotted against microsphere measurements of rCBF (mL/min per 100 g) for 39 ROIs. A strong correlation was found between these two sets of measurements (r =. 837, P < .001). The slope of the regression line (0.97 ± 0.03) was close to unity
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