低剂量双源CT颅脑灌注成像在超急性期脑梗死中的诊断价值

Diagnostic value of low dose dual-source CT cerebral perfusion imaging in patients with hyperacute cerebral infarction

目的探讨管电压为70 kV时不同管电流及采集频次对双源CT颅脑灌注成像(CTP)图像质量、辐射剂量的影响,及其在超急性期脑梗死患者中的诊断价值。方法前瞻性选取2017年12月至2019年2月浙江省丽水市中心医院临床可疑的超急性期脑梗死患者190例,按照数字表法随机分为4组,A、B、C组均50例,D组40例,均在发病6 h内行双源CT平扫及70 kV管电压颅脑灌注成像。A组管电流120 mA,B组和C组管电流均为100 mA,D组管电流80 mA。A、B、D组采集频次21次,C组采集频次17次。测量脑血流量(CBF)、脑血容量(CBV)、平均通过时间(MTT)、达峰时间(TTP)等,评价图像质量,记录有效剂量(ED)。各参数组间图像质量及辐射剂量的比较采用单因素方差分析。结果4组CTP伪彩图灰质和白质灌注参数(CBF、CBV、MTT及TTP)的差异均无统计学意义(P>0.05),所有图像均可满足诊断要求。A组颈内动脉、大脑中动脉血管管腔边缘锐利度、整体图像质量及颈内动脉图像噪声评级高于D组(P<0.05);A组颈内动脉血管管腔边缘锐利度高于B、C组(P<0.05);B、C组颈内动脉及大脑中动脉血管管腔边缘锐利度均高于D组(P<0.05)。CT平扫及A、B、C、D组的ED分别为1.10、2.11、1.76、1.42、1.40 mSv,差异有统计学意义(P<0.05)。与A组相比,B、C及D组的ED均有不同程度的降低,分别降低16.6%(0.35/2.11)、32.7%(0.69/2.11)及33.6%(0.71/2.11),差异均有统计学意义(P均<0.05)。对于超急性期脑梗死,低剂量双源CTP阳性率为93.5%(172/184),CT平扫阳性率为52.2%(96/184);对于超急性期腔隙性脑梗死,低剂量双源CTP阳性率为72.1%(31/43),CT平扫阳性率为16.3%(7/43)。结论70 kV管电压CTP,适当减低管电流(100 mA)及采集频次(17次)可降低辐射剂量且图像质量可满足诊断需求。相较于CT平扫,低剂量双源CTP对于超急性期脑梗死尤其是腔隙性脑梗死更为敏感。

Objective To evaluate image quality and radiation dosage of CT cerebral perfusion(CTP)imaging of 70 kV with different tube current and scanning passes and its diagnostic value for hyperacute cerebral infarction.Methods A total of 190 patients with suspected hyperacute cerebral infarction in Lishui Central Hospital of Zhejiang Province from December 2017 to February 2019 were selected prospectively,and all patients were divided into 4 groups according to random number table and received non-contrast CT examination and dual-source CT cerebral perfusion imaging with 70 kV protocol simultaneously within 6 hours after the onset of symptoms:group A,120 mA,21 scanning time points;group B,100 mA,21 scanning time points;group C,100 mA,17 scanning time points;group D,80 mA,21 scanning time points.The values of perfusion parameters such as cerebral blood flow(CBF),crerbral blood volume(CBV),mean transit time(MTT),time to peak(TTP)were acquired.Image quality was evaluated and effective dose(ED)was recorded.The quantitative variables of image quality and radiation dosage were compared between four groups using one-way analysis of variance test.Results There was no differences between groups on the CBF,CBV,MTT,TTP maps for all CTP values(P>0.05),and all images could meet the diagnostic requirements.The subjective image quality score of vessel sharpness and overall image quality of both internal carotid artery and middle cerebral artery and the degree of noise of internal carotid in artery in group A was higher than that in group D(P<0.05).The score of vessel sharpness of internal carotid in artery ingroup A was higher than those in both groups B and C(P<0.05).The scores of vessel sharpness of both internal carotid artery and middle cerebral artery internal carotid in artery ingroups B and C were higher than that in group A(P<0.05).The mean EDs of non-contrast CT in group A,B,C,D were 1.10,2.11,1.76,1.42,1.40 mSv;compared to group A,ED was reduced approximately 16.6%(0.35/2.11),32.7%(0.69/2.11)and 33.6%(0.71/2.11),respectively(P<0.05).The diagnostic accuracy of low dose dual source CTP for detecting hyperacute cerebral infarction was 93.5%(172/184),while that of non-contrast CT was 52.2%(96/184);for detecting hyperacutelacunar cerebral infarction,it was 72.1%(31/43)and 16.3%(7/43)respectively(P<0.05).Conclusion Appropriate reduction of tube current(100 mA)and scanning passes(17 scanning time points)can reduce the radiation dosage and acquire comparable image quality for 70 kV protocol CTP.Compared with non-contrast CT,low dose dual-source CTP is more sensitive to hyperacute cerebral infarction,especially hyperacute lacunar cerebral infarction.