心肌灌注显像CT衰减校正伪影产生的初步研究

目的：研究心肌灌注显像（MPI）经CT衰减校正（CTAC）后伪影的产生及其对临床诊断的影响。方法：回顾性分析按Bayesian理论，冠心病患病率〈5％的48例受检者所行的72例次MPI（负荷41例次，静息31例次），图像在未行CTAC时显示正常者进行研究。将左心室心肌划分为20个节段，半定量分析（0分＝放射性分布正常；1分＝放射性分布轻度减低；2分＝放射性分布中度降低；3分＝放射性分布重度减低；4分＝放射性分布缺损）各心肌节段在CTAC后放射性分布变化情况。结果：72例次MPI中，16例次（22．2％）的75个心肌节段（均在左心室心尖、前壁、前间壁区域）在CTAC后出现了放射性分布不同程度的减低。75个受累节段中分别有51、21和3个节段评分增加了1、2和3分，平均每个心肌节段评分增加了1．3分。41例次负荷MPI和31例次静息MPI中，分别有9例次（21．9％）的39个心肌节段、7例次（22．6％）的36个心肌节段在CTAC后出现了放射性分布减低，负荷与静息MPI相比，CTAC后发生心肌节段放射性分布减低的概率（χ^2＝2．84，P〉0．05）与程度（μ=0．54，P〉0．05）均无显著统计学差异。10例负荷／静息MPI都满足纳入标准而纳入研究者中，4例的负荷／静息MPI在CTAC后，出现了相同部位（尖前壁、尖下壁）、相同程度（评分均增加了2分）的灌注降低；3例出现了同一部位，但不同程度的灌注减低；另有3例出现了不同部位心肌节段的灌注减低。CTAC后出现心肌节段灌注减低者与未出现者相比年龄、性别构成无统计学差异。结论：分析SPECT／CT心肌灌注图像时，应同时分析CTAC前后的灌注图像。对于只在CTAC后出现的灌注缺损，需要考虑可能存在CT与SPECT图像配位不准。

Artifacts in CT-based Attenuation Correction Myocardial Perfusion SPECT: A Preliminary Study

Objective,. To investigate the artifacts in myocardial perfusion imaging （MPI） after CT-based attenuation correction （CTAC） and their effect on clinical diagnosis. Methods：According to Bayesian theory,we studied 72 consecutive MPI （41 stress MPI,31 rest MPI） of 48 patients with the prevalence of coronary artery disease 〈5% retrospectively. Patients underwent stress and/or rest MPI with ^99mTc-methoxyisobutylisonitrile with SPECT/CT and showed normal perfusion in noncorrected attenuation MPI. Tracer uptake in 20 segments of left ventricular myocardium was semi-quantitatively assessed （0= normal, 1= mild defect, 2 = moderate defect, 3 = severe defect, 4 = absence of perfusion） before and after CTAC. Results： After CTAC, 16/72 （22.2%） MPI showed perfusion defect in 75 segments in apical, anterior or anteroseptal region. Of these 75 segments, 51,21 and 3 segments had scores increased by 1,2 and 3, respectively. The mean incremental score was 1.3. Of 41 stress MPI, 9 MPI（21.9%）with 39 segments showed perfusion reduction after CTAC. Of 31 rest MPI, however, 7 MPI （22.6%） with 36 segments showed perfusion defect after CTAC. Neither the prevalence nor severity of perfusion reduction after CTAC was different between rest MPI and stress MPI （χ^2 =2.84,P〉0.05;μ=0. 54,P〉0.05,respectively）. Among 10 patients whose stress and rest MPI were included in the study,after CTAC,4 patients had the same perfusion defect,another 3 patients had the same segments with varied severity of perfusion defect, the left 3 patients had different changes, between stress MPI and rest MPI. There were no differences of gender or age between the patients whose MPI showed perfusion defect after CTAC and those who did not. Conclusion： The presence of artifacts after AC can influence the accuracy of MPI in detecting coronary artery disease. Physicians should view both uncorrected and corrected imagings. When the perfusion defect is found just after CTAC,one should consider the possibility of misregistration