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Objective To prospectively determine whether position and size of tumor region of interest (ROI) influence estimates of lung cancer vascular parameters at 256-slice CT perfusion study.Methods After institutional review board approval and informed consent,16 men and 11 women with lung cancer underwent 70-second CT perfusion study. Perfusion, blood volume, peak enhancement weredetermined for 60 or 120 mm2 circular ROIs placed at the tumor edge and center and around (outlining) visible tumor. ROI analysis was repeated twice by two observers in the same way to get the average values.The correlation between the measurements and microvascular density counts was determined in 19 patients with operation.Measurements were compared by using Pair-Samples t test,a difference with P≤0.05 was significant.Results Perfusion,blood volume,peak enhancement measurements were substantially higher at the edge than at the center for both 60 and 120 mm2 ROI. For 60 and 120 mm2 ROI,median of the three measurements were (M=15.40,9.50 ml · min- 1 · 100 ml - 1,M =35.60,25.40 ml · 100 g-1,and M=16.47,10.20 HU),respectively,at the edge versus(M =14.80,8.52 ml · min- 1 · 100 ml- 1,M =33.50,23.90 ml · 100 g- 1,and M =15.64,9.40 HU),respectively,at the center(t value was 10.95,9.80,7.06,2.93,7.74 and 10.09,respectively,all P ＜ 0.05 ). Measurements varied substantially depending on the ROI size,values for the ROI for outlined tumor were intermediate between those at the tumor edge and center.Perfusion(M=12.51 ml.min- 1 · 100 ml-1),blood volume(M=29.31 ml.100 g-1),peakenhancement (M =12.93 HU) for the ROI outlining tumor were intermediate between those at the tumor edge and center.There was a good correlation between perfusion,blood volume,peak enhancement for the ROI outlining tumor and microvascular density[ ( 19.43 ± 8.78 ) vessels/0.74 mm2 ],respectively ( r value 0.732,0.590 and 0.544,all P ＜ 0.05 ).Conclusions Position and size of tumor ROI substantially influence ultimate perfusion values.ROI for outlined entire tumor is more reliable for perfusion measurements and more appropriate clinically than use of arbitrarily determined smaller ROI.
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Objective To compare the low- and standard-dose protocols in the evaluation of coronary artery calcification (CAC) scores and in image quality,and to assess the accuracy of low-dose prospective ECG-gated helical CT in CAC measurements.Methods Forty-three patients with CAC were scanned twice using a tube current setting of 100 and 55 mA retrospectively.CAC scores (Agatston) of different branches of coronary artery were recorded.The mean and SD of the CT attenuation values in regions of interest in the aorta were measured,and the value (mean + 2 × SD) were obtained.Results Calcification plaques were found in 105 of the 172 vessels in the 43 subjects.The radiation dose of the 50 mAs group was (0.72 ± 0.04) mSy,significantly lower by 0.6 mSv than that of the 100 mAs group [(1.32 ± 0.08) mSv,P ＜ 0.05].The total calcification score of the 55 mAs group was significantly positively correlated with the routine dose group after performing the square root transformation (r =0.998).A signficant correlation existed in vessel-based calcification between these 2 groups (r= 0.997).Conclusions Low-dose prospective ECG-gated 64-slice CT yields high accuracy on CAC scoring while maintaining the image quality needed to measure CAC.
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Objective To study the value of MR diffusion tensor tractography(DTT) in evaluating the white matter(WM) tracts in cerebral neoplasm.Methods Fiber tractography was used in this study to assess tumour-induced changes in WM trajectories in three cases of cerebral neoplasm: glioblastoma multiforme, meningioma and anaplastic astrocytoma.Results Three patterns of WM alteration were identified:(1) disruption;(2) displacement and (3) infiltration. Tumor disruption of WM tracts was observed in glioblastoma multiforme, in which the terminated fibers could crossed the corpus callosum. In meningioma, DTT illustrated bulk displacement ,remnant and separation of WM tracts.In anaplastic astrocytoma,WM tracts were disrupted and infiltrated by tumors. Conclusion The changes of WM tracts on DTT are correlated with the clinical and histopathological features of the tumor.