Article Figures & Data
Figures
- Fig 1.
PET-CBF, CT-CBF, and CT-CBV images obtained in the five subjects. The CBF images of both PET and CT are displayed at the same window level. Note that large vessels on the brain surface are more prominent on CT-CBF than PET-CBF images. CT-CBV images were used for the VPE method.
- Fig 2.
Vascular maps and CT-CBF images obtained in subject 1 at various levels of VPE threshold. On the vascular maps, gray matter is displayed in green, and white matter in dark blue. The separation between gray matter and white matter was performed on the basis of the pixel attenuation on nonenhanced scans. Vascular pixels are expressed in red. The extent of the vascular area increases as the level of VPE threshold decreases. VPE threshold is indicated below the CT-CBF images. If the VPE threshold is very small (such as 5 mL/100 g), part of the brain parenchyma also disappears from the CT-CBF image.
- Fig 3.
Scatterplot of CT-CBF without VPE against PET-CBF and associated linear regression in subject 1. The slope is larger than 1.0, which suggests overestimation of CBF measured with perfusion CT. The correlation coefficient (r = 0.51) indicates moderate correlation.
- Fig 4.
Scatterplot of CT-CBF with VPE (threshold of 8 mL/100 g) against PET-CBF and associated linear regression in subject 1. The slope approaches 1.0, and the correlation coefficient (r = 0.69) increases compared with that without VPE.
- Fig 5.
Results of linear regression analysis obtained in subject 1 against various VPE thresholds. Values without VPE are plotted at the most right-hand side (threshold of 104 mL/100 g).
A, Correlation coefficient. As the VPE threshold decreases, the correlation coefficient increases. The best correlation is observed at a VPE threshold of 8 mL/100 g. Note that correlation coefficients rapidly decrease when VPE threshold is less than 8 mL/100 g.
B, Slope of linear regression. As the VPE threshold decreases, the slope also decreases and approaches 1.0. When the VPE threshold is less than 8 mL/100 g, the slope becomes less than 1.0.
C, Intercept of linear regression. As the VPE threshold decreases, the intercept increases and approaches zero.
- Fig 6.
Average CBF values of the whole section (pixels) with both CT and PET against varying VPE threshold values in subject 1. Without VPE (plotted at the most right-hand side, threshold of 104 mL/100 g), the CT-CBF value is higher than the PET value. CBF values with PET are almost constant despite the change in the VPE threshold. As the VPE threshold decreases, CBF values with CT decrease and approach the corresponding PET values. * indicates a statistically significant difference (P < .01)
- Fig 7.
Average CBF values of gray matter with both CT and PET against varying VPE threshold values in subject 1. Without VPE (plotted at the most right-hand side, threshold of 104 mL/100 g), the CT-CBF value is overestimated. As the VPE threshold decreases, CT-CBF values decrease and approach the corresponding PET values. * indicates a statistically significant difference (P < .01)
- Fig 8.
Average CBF values of white matter with both CT and PET against varying VPE threshold values in subject 1. Overestimation of CT-CBF is not observed. As the VPE threshold decreases, CT-CBF values decrease. * indicates a statistically significant difference (P < .01)
Tables
Subject No. VPE Threshold of the Best Correlation (mL/100g) Correlation Coefficient Slope Intercept Without VPE With VPE Without VPE With VPE Without VPE With VPE 1 8 0.51 0.69 1.55 1.05 −18.81 −7.91 2 8 0.52 0.65 2.65 1.55 −62.61 −26.36 3 6 0.38 0.63 1.27 1.02 −2.72 −3.38 4 8 0.37 0.62 1.69 1.25 −13.92 −10.43 5 8 0.44 0.65 1.58 1.00 −15.48 −3.33 Average 7.6 0.44 0.65 1.75 1.17 −22.71 −10.28 Subject No. Whole Section Gray Matter White Matter Without VPE With VPE Without VPE With VPE Without VPE With VPE PET CT PET CT PET CT PET CT PET CT PET CT 1 45.91 52.44* 46.20 40.70* 49.34 58.81* 50.02 47.69* 35.17 32.44 35.08 25.46* 2 46.73 61.30* 46.90 46.91 50.53 73.98* 51.05 55.65* 40.49 40.47 40.50 33.44* 3 49.20 59.85* 49.43 47.67 54.61 70.08* 55.03 57.60 39.53 41.59 38.76 28.72* 4 44.20 60.71* 44.57 46.36* 48.43 64.54* 48.75 53.81* 38.31 55.36* 37.64 33.97* 5 48.26 60.76* 48.73 47.80* 51.54 66.22* 52.02 50.73 37.50 42.80 37.32 30.34* Average 46.86 59.01 47.17 45.56 50.89 66.73 51.37 52.75 38.20 42.53 37.86 30.38 * Indicates a statistically significant difference (P < .01).
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