A CT Method to Measure Hemodynamics in Brain Tumors: Validation and Application of Cerebral Blood Flow Maps
Aleksa Cenica,
Darius G. Nabavia,
Rosemary A. Craena,
Adrian W. Gelba and
Ting-Yim Lee
,a
a From the Imaging Research Laboratories (A.C., D.G.N., T-Y.L.), John P. Robarts Research Institute, London; Medical Biophysics Department (A.C., T-Y.L.), The University of Western Ontario, London; Imaging Division, Lawson Research Institute (A.C., T-Y.L.), St. Joseph's Health Centre, London; and Anesthesia Department (R.A.C., A.W.G.), London Health Sciences Centre, London, Ontario, Canada.
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FIG 1. A, Schematic representation of IRF in a tissue with an intact (ie, impermeable to contrast molecules) BBB.
B, Schematic representation of an IRF, R(t), in tissue with a permeable BBB. The first plateau reflects the intravascular phase of the contrast material. The second (and much lower) plateau reflects the extravascular phase. The extraction fraction, E, is derived by dividing the second plateau height by the first plateau height.
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FIG 2. Examples of dynamic CT-measured contrast-enhancement curves of an artery (line), normal tissue (squares), and tumor (circles) in a rabbit with brain tumor. For clarity, the tissue curves are displayed using a different scale of CT numbers (right axis). Thus, the arterial enhancement curve (left axis) is more than 10 times higher than that of the tumor curve, and 50 times higher than that of the normal tissue curve. Note the higher washout phase of the tumor curve relative to the normal tissue.FIG 3. Contrast-enhanced CT image illustrating tumor, peritumor and contralateral normal ROIs found in a rabbit. The radial arteries (RA) are clearly displayed at the bottom of the figure (adjacent to the radial and ulna bones)
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FIG 4. Dynamic CT measurements plotted against microsphere measurements of regional CBF (mL/min/100 g) for 54 ROIs (18 ROIs for each tumor, peritumor, and normal tissue) in nine rabbits with brain tumor. A strong correlation was found between these two sets of measurements (r = 0.847). The slope of the regression line (0.99 ± 0.03, P < .001) was not significantly different from unity
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FIG 5. CBF maps derived from a rabbit with brain tumor. The CBF values, ranging from low-to-high flow are color-coded from black (0 mL/min/100 g) to blue and green (100 mL/min/100 g) to yellow and red (200 mL/min/100 g). For both PaCO2 levels, the tumor is clearly delineated by the red and yellow colors.
A, Plain (precontrast) CT Image. The following X-ray CT parameters were used to acquire the image: 80 kVp, 80 mA, 10-cm field of view, and 3-mm slice thickness. Hyperdense areas corresponding to the tumor were observed in the right parietal and temporal regions.
B, Normocapnia CBF map. CBF in the tumor ranged from 66 to 208 mL/min/100 g, whereas CBF in the contralateral normal hemisphere ranged from 14 to 75 mL/min/100 g.
C, Hypocapnia CBF map. The maximum and minimum CBF values in tumor were 56 and 170 mL/min/100 g, whereas the contralateral normal hemisphere showed CBF values ranging from 3 to 43 mL/min/100 g.
D, Subtraction of the hypocapnia CBF map from the normocapnia map. The mean global CBF difference was 18.7 mL/min/100 g. Reduction in CBF upon hyperventilation is shown in both tumor and normal tissues. The green circular areas in the center of the brain are cerebral arteries.
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