64层螺旋CT脑灌注间隔轴扫模式降低扫描剂量的可行性研究

Feasibility of reducing X-ray dose in 64-slice CT brain perfusion by increasing interval between scans with an axial scan mode

目的探讨64层螺旋CT脑灌注间隔轴扫模式降低扫描剂量的可行性。方法临床可疑卒中患者145例，按照时间顺序分别进行连续轴扫模式（电影组）和间隔扫描模式（轴扫组）的脑灌注成像，选择两组检查结果正常者各20例。电影组采用Cinefull扫描模式，扫描时间1S，在50S内连续曝光扫描。轴扫组使用Axialfull扫描模式，扫描时间1S，间隔时间2S，两组扫描范围均为40mm。测量两组双侧额叶、颞叶、枕叶的灰质、白质和基底节区脑血流量（CBF）、血容量（CBV）、平均通过时间（MTT），两组间比较采用t检验。记录两组扫描辐射剂量CT容积剂量指数（CTDIvol）和剂量长度乘积（DLP），采用百分数进行对比分析。结果电影组脑灰质、白质及豆状核CBF分别为（48．8±16．0）、（28．3±12．0）、（55．4±11．2）ml·100g^-1·min^-1，轴扫组分别为（47．6±9．6）、（23．9±6．9）、（53．1±5．1）ml·100g^-1·min^-1；电影组CBV分别为（2．2±0．7）、（1．5±0．5）、（2．3±0．8）mL／100g，轴扫组分别为（2．2±0．6）、（1．5±0．4）、（2．2±0．7）ml／100g；电影组MrITr分别为（3．9±0．8）、（5．3±0．9）、（2．8±0．4）S，轴扫组分别为（6．0±1．7）、（6．0±1．7）、（3．0±0．3）S，两组间CBF、CBV及MTT差异均无统计学意义（t值分别为0．244、1．533、0．832、0．166、0．411、0．537、1．688、1．471、1．638，P值均〉0．05）。电影组DLP为2361．92mGy·cm，轴扫组为803．04mGy·cm，比电影组降低66％。结论使用扫描时间1s、间隔2s的轴扫模式可以在保证脑灌注参数准确性的基础上降低辐射剂量。

Objective To investigate the feasibility of reducing X-ray dose in 64-slice CT brain perfusion by relaxing the temporal resolution with an axial scan mode. Methods Forty patients who underwent CT perfusion scans for suspicion of stroke but turned out to have normal brain perfusion were selected for the study. Among these patients, 20 were scanned with cine scan mode, which meant continuous scanning for 50 s with scan time of I s. And other 20 patients were scanned with axial mode, which was consisted of 1 s scan time and 2 s interval between scans. The axial coverage was 40 mm for all patients. The regional cerebral blood flow （CBF）, regional cerebral blood volume （CBV） and mean transit time （MTF） were analyzed by t-test for three anatomic features： the cortical gray matter（ GM）, the normal white matter （WM） and the lentiform nucleus（LN）. The radiation dose between the two groups was compared. Results The CBF of GM, WM, I,N measured with cine scan mode were （48.8 ± 16. 0 ）, （28.3 ± 12. 0 ）, （55.4±11.2） ml · 100g^-1·min-1 TheCBVwere （2.2±0.7）,（1.5±0.5）,（2.3±0.8） ml/100g. TheMTT were （ 3.9±0. 8 ）, （5.3±0. 9）, （2. 8 ± 0. 4 ） s. The CBF of GM, WM, LN measured with axial mode were （47.6±9.6）,（23.9±6.9）,（53.1±5.1） ml·100g^-1·min^-1 TheCBVwere（2.2±0.6）,（1.5± 0.4）,（2.2±0.7） ml/100 g. The MTT were （6.0±1.7）,（6.0±1.7）,（3.0±0.3）s. There were no statistically significant differences between the corresponding parameters for the two groups （t = 0. 244,1. 533,0. 832,0. 166,0. 411,0. 537,1. 688,1. 471,1. 638, P 〉 0. 05 ）. The radiation dose with the axial mode was 803. 04 mGy· cm, which was 66% lower than that with cine scan mode （2361.92 mGy · cm）. Conclusion The use of relaxed temporal resolution with 1 s scan time and 2 s interval in CT brain perfusion can provide accurate perfusion parameters while reducing radiation by 66%.