Clinical Application Of Cerebral CT Perfusion Imaging In Cerebral Ischemic Disease With Carotid Artery Stenosis

Part1study of Dual-source CT perfusion imaging in normal adult[Objective]29normal adult volunteers were performed with cerebral perfusion imaging using dual-source CT machine, in order to get the reference value of perfusion parameters in normal adults.[Materials and methods]1. Clinical data29healthy volunteers (18males and11females,21-76years old, mean age=47.62±13.61years) examined with DSCT brain perfusion imaging were divided into3groups according to the following age standards:the ones younger than35were the youth group, the age between35to55ones were the middle-age group and older than55ones were the older-age group. All the volunteers hadn’t had any head-and-neck vascular diseases or cerebral diseases and without positive nervous system symptoms. All the volunteers were scanned with plain brain CT and showed normal before the DSCTP scan. 2. InstrumentsCT scanner:Siemens SOMATOM Definition dual-source CT High-pressure double-barrel syringe:MEDRAD Contrast agent:Ultravist,(iodine concentration:370mgI/ml)3. DSCTP scan protocolSpecial neuro PCT was used.(1) Routine head plain scan parameters:5mm slice thickness,5mm slice distance,120Kv and420mAs.(2) DSCTP scan:refered to plain CT scan images, crentred on suprasellar or basal ganglia region layer to set up scanning scope, continuous cyclic scaned3layers once,8mm slice thickness, covered region of24mm. CTP scan parameters:80Kv voltage and270mAs, FOV200mm, scanned speed:1s/r, scanned39times totally,117images were obtained, monitored time:40sec. The scan of DSCT perfusion began at the time of4s after a bolus of45ml Ultravist (concentration:370mgI/ml) and followed by40ml saline solution were injected with the rate of5.5ml/sec by using high-pressure double-barrel syringe. Before the DSCTP scanning,20ml saline solution was injected with a speed of5.5ml/s for pre-injection.4. DSCTP image post-processingAfter DSCTP scan, all the data were transferred to an offline workstation named Syngo2008G which was equipped with a automatic post-processing software package (Syngo CT Workplace, Version syngo CT2008G, Siemens Healthcare) of perfusion."Auto Stroke MTT" was selected to automatic post-processing and got tine-density curve (TDC). Meanwhile, the maximum intensity projection (MIP), and the color map of parameters as cerebral blood flow (CBF), cerebral blood volume (CBV), time to start (TTS), time to peak (TTP), time to drain (TTD) and mean transit time (MTT) were automaticly obtained.5.The region of interest (ROI) Mirrored for middle line structure, set up quasi-circular ROI respectively in bilateral frontal lobe, temporal lobe and occipital lobe grey matter, bilateral basal ganglia region(included caudate nucleus and putamen), internal capsule, dorsal thalamus, bilateral anterior and posterior watershed write matter in the3layers of the obtained perfusion images. Every location were set up round ROIs, each ROI area was1cm2(the cerebral lobe grey matter, write matter) or0.5cm2(basal ganglia region, capsula interna, dorsal thalamus). The mean of the parameters of ipsilateral Frontal, temporal and occipital lobes grey matter would be considered as the unilateral parameters of "grey matter". The mean of the parameters of homolateral anterior and posterior periventricular write matter would be considered as the parameters of "white matter". Unilateral grey matter and white matter parameters were the average of unilateral parameters of3layers. Basal ganglia region, capsula interna, dorsal thalamus parameters were obtained by measured3times.6. Statistics analysis:SPSS13.0software package were applied to statistical analysis in this study. The measurement data were recorded as (mean±standard deviation). The statistically significant difference was set at P<0.05.(1)Paired-Samples T Test or2Independent Samples Test was performed to compare the parameters between bilateral cerebral hemisphere in the same location depended on the homogeneity or heterogeneity of variance.(2)Parameters of different genders were compared with independent sample t-test.(3) Parameters of different age groups in the same location were compared with One-Way ANOVA.[Results]1. In the normal adult, there were no statistically significant difference of the parameters between bilateral cerebral hemisphere in the same location (P>0.05).The mean parameters of each location were obtained: the means of different parameters in differet locations (x±s) Unit:CBF:ml.100g-1.min-1; CBV:ml.100g-1; TTP:s; MTT:s. the ranks of parameters in different locations:CBF:putamen>grey matter/caudate nucleus> dorsal thalamus> internal capsule>white matterCBV:putamen> grey matter/caudate nucleus> dorsal thalamus>internal capsule> white matterTTP:white matter>grey matter/dorsal thalamus/internal capsule>caudate nucleus/putamenMTT:white matter>grey matter/internal capsule>putamen/caudate nucleus/dorsal thalamus2. There were no statistically significant difference of the parameters in different genders (P>0.05), and the parameters in the same location among different age groups (p>0.05).[Conclusions]1.In this study, we implemented DSCT perfusion scan by using Siemens SOMATOM Definition DSCT scanner, a bolus of45ml iodinated contrast medium (370mgI/ml) and a automatic post-processing software based on the maximum slope mathematical model were used. At last, we got the CTP parameters(CBF/CBV/TTP/MTT) of normal adult as following:grey matter (70.36±4.8) ml.100g-1.min-1/(3.60±0.24) ml.100g-1/(9.44±0.72) s/(3.14±0.09) s; white matter(28.59±2.8) ml.100g-1.min-1/(1.71±0.13) ml.100g-1/(10.88±0.93) s/(3.89±0.50)s. The rate of grey matter CBF and white matter CBF was2.5:1. These results could reflect the normal adult cerebral perfusion condition.3. There were no statistically significant difference of the parameters in different genders (P>0.05), the CBF and CBV of gray matter among different age groups were no statistically significant difference too, but showed a decreased tendency with the increasement of age.Part2Correlation between the degree of arteries stenosis and cerebral perfusion in the patients of unilateral ICA/MCA stenosis[Objective]To evaluate the cerebral perfusion in patients with unilateral internal carotid artery (ICA) or middle cerebral artery (MCA) stenosis, and explore the interrelation between degree of arteries stenosis, collateral circulation and DSCTP parameters.[Materials and methods]1. Clinical data34patients (19males and15females,21-75years old, mean age=51.07±12.21years) with unilateral ICA or MCA stenosis were examined with DSCTP. The clinical symptoms include different degrees of repeating or intermittent dizziness or headaches, unilateral limb weakness or unstable gait. All the patients had course of2week to3years. All the patients were made sure without acute cerebral hemorrhage with plain CT and underwent DSCTP scan in the intermission of symptoms onset.30patients were underwent digital subtraction angiography (DSA) in3days before or after DSCTP scan,1patients were examined with color doppler flow imaging (CDFI) and3patients with computed tomography angiography (CTA).2. Instruments the same as to Part13. DSCTP scan protocolMost of protocol were the same to Part1but the following:if there was no large hypodensity lesion in the plain CT imageS, the DSCTP scan scope was the same to Part1:centred on suprasellar or basal ganglia region layer; if there was hypodensity lesion, the scan scope was crentred on the layer of the largest area of the lesion.4. Set up the ROIMirrored for middle line structure too, and then obtained the same ROIs in the offside.(1)If the perfusion maps were symmetrical normal, ROIs were set up in both temporal lobes.(2) If the perfusion maps were unilateral abnormal, create irregular ROI according to the lesion in the maximum area of lesion layer, kept away from the large and remarkable malacia lesion when measured. Considered the actual measured value as the absolute value of the parameters, the ratio of parameters obtained respectively from the lesion side and the healthy side was considered to be the relative value of the parameters.5. Grouped the vessels according to the artery stenosis rateAccording to the standard of North American Symptomatic Carotidtomy Trial(NESCET), divided the narrow ICA into3groups:mild artery stenosis:0%-29%; moderate artery stenosis:30%-69%, severe stenosis and occlusion.-70%-99%and100%. Grouped stenosis degree of MCA as the following:mild artery stenosis:<50%, moderate artery stenosis:50%-75%; severe stenosis and occlusion:>75%. Evaluated the condition of collateral circulation and then grouped it by "open" or "not open" in the severe artery stenosis patients.6. Statistics analysis:SPSS13.0software package were applied to statistical analysis in this study. The measurement data were recorded as (mean±standard deviation). The statistically significant difference was set at P<0.05, the significant statistically significant difference was set at P<0.01.(1)The different groups of diseases groups:Paired-Samples T Test was performed to compare the absolute value of parameters in inter-groups; the comparisons of the relative value of parameters among the groups were used independent-samples T Test.(2) The groups of different degree of stenosis: Paired-Samples T Test was performed to compare the absolute value of parameters in inter-groups too; the compare of the relative value of parameters among the groups were used one-way ANOVA. LSD method was used for the pairwise comparison.(3) Independent-samples T Test were performed to compare the relative value of parameters between the groups of collateral circulation condition.(4) Used Spearman correlation analysis to analysis the correlation between the degree of stenosis and relative value of parameters, the correlation was close if the correlation coefficient was larger than0.5.[Results]1. Among the34patients, there were15cases (44%) whose arteries stenosis occurred in the right side, and19cases (56%) occurred in the left. Unilateral ICA stenosis occurred in20cases (59%), and unilateral ICA stenosis occurred in14cases (41%). According to the brain lesions found in plain CT and MRI performances, the patients were divided into3group, normal without infarction group12cases (35.3%), multiple lacunar infarction group18cases (52.9%), and large piece of infarct4cases (11.8%).2. There were statistically significant difference (P<0.05) in the comparison of the absolute values of parameters obtained from artery stenosis side and the healthy side of brains in normal without infarction group and multiple lacunar infarction group. CBF of stenosis side was less than the offside, and the TTP, MTT were lager than offside. There was no significant difference in the comparisons of relative values among the groups.3. About the comparison of the absolute value of parameters obtained from the stenosis side and the healthy side in each group of different degree of stenosis in the patients of artery stenosis:there was statistically significant difference only in TTP (P<0.05) among the4parameters in the group of mild stenosis while the CBF, TTP, MTT were different (P<0.05) in the groups of moderate stenosis and severe stenosis or occlusion.4. There was statistical significance in the difference of rCBF and rMTT (P<0.05) while there was no statistical significance in the rCBV and rTTP (P>0.05) in the comparisons among the different groups of variousd degrees of stenosis. Multiple comparisons:rCBF:there was statistical significance between the groups of mild stenosis and severe stenosis or occlusion (P=0.004). rMTT:The difference between the group of mild stenosis and severe stenosis or occlusion, and between the groups of moderate stenosis and severe stenosis or occlusion were statistical significance (P=0.001、P=0.022)5. There correlation analysis between the different groups of stenosis degree and the relative value of the parameters show a significant negative correlated between the degree of stenosis and rCBF (r=-0.542, P<0.01), rTTP was positively correlated with the degree of stenosis (r=0.420, P<0.05) and rMTT was significant negative correlated with it (r=0.652, P=0.000).6.There was statistical significance difference of rTTP only between the groups of "open "and "not open" of collateral circulation (t=3.349, P<0.01).It meaned rTTP of the open collateral circulation was larger than the not open groups.[Conclusions] 1.when unilateral ICA/MCA stenosis occurred, There were statistically significant difference (P<0.05) in the comparison of the CBF,TTP and MTT values between artery stenosis side and the healthy side in normal without infarction group and multiple lacunar infarction group. Which indicated that the cerebral perfusion migtht be significant abnormal while even though there was no large piece of infarction. There was no significant difference in the comparisons of CBV between these two groups, which indicated that the cerebral tissues now was in the compensation stage.2. TTP was the earliest parameter which could reflect the abnormality of hemodynamics.3. When unilateral ICA/MCA stenosis occurred, the effect of the degree of arterial stenosis was significant on ipsilateral cerebral perfusion:the cerebral perfusion was inversely related to the degree of artery stenosis. A decrease in CBF and an increase in MTT are the most significantly reflective of hemodynamic compromise.4. The effect of collateral circulation on the cerebral perfusion was mainly a increase in TTP, while the effect was not significant in CBF.