【作者】 黄玲；

【导师】 秦维昌；

【作者基本信息】 泰山医学院 ， 影像医学与核医学， 2009， 硕士

【摘要】 目的1.通过实验分析,探讨双源CT(dual-source computed tomography, DSCT)冠状动脉成像时,影响受检者辐射剂量的各种因素。2.通过统计学软件分析,得出辐射剂量与各影响因素之间的拟合曲线及拟合方程,即得到各辐射剂量与影响因素的关系,。3.优化双源CT冠状动脉成像的扫描方案,降低受检者的辐射剂量。方法1.用双源CT对插入左冠状动脉的胸部模体(RS-330)进行扫描,采用心脏常规螺旋扫描模式(回顾性心电门控重建技术),心电图设为DEMO模式,心率固定为60 bpm,调节扫描参数包括管电压、mAs、扫描长度(LEN)、全剂量扫描时间窗。首先固定其他扫描条件,变动管电压(80、100、120、140)进行扫描,然后变动mAs(320、340、360、380、400、420)。再分别变动扫描长度(100 mm、110 mm、120 mm、130 mm、140 mm)及全剂量扫描时间窗的宽度(15%、20%、25%、35%、40%、48%),固定其他扫描参数进行扫描。记录每次扫描得到的容积CT剂量指数(CTDIvol)及剂量长度乘积(DLP),每种剂量的获得均扫描3次,取平均值。2.将不同扫描参数获得的相应的辐射剂量,输入统计学软件SPSS 13.0,分别得到在其他扫描条件不变的情况下,该扫描条件与容积CT剂量指数(CTDIvol)和剂量长度乘积(DLP)之间的拟合曲线及拟合方程。3.随机记录日常工作中受检者的体重指数(BMI),取所有扫描条件(kV、mAs、扫描长度及螺距等)均相同的受检者,得到不同体重指数的辐射剂量,再利用SPSS 13.0统计分析软件,得出BMI与容积CT剂量指数(CTDIvol)之间的拟合曲线及拟合方程。根据之前得到的kV、mAs与容积CT剂量指数(CTDIvol)之间的拟合方程,两方程进行换算得到BMI与kV、mAs之间的拟合方程,然后即可根据体重指数调节kV与mAs。4.记录日常检查受检者的心率与其最佳的重建期相,可得出心率与最佳重建期相的关系。从而据此以及患者的心率等诸多因素,确定采用何种扫描模式,前瞻性心电触发扫描或回顾性心电门控重建技术;如果采用回顾性心电门控重建技术,据此调节全剂量时间窗的设置,降低受检者的辐射剂量。结果1.不同kV(80、100、120、140)所对应的CTDIvol分别为14.15 mGy、31.35 mGy、54.00 mGy、82.51 mGy;不同mAs(320、340、360、380、400、420)所对应的CTDIvol分别为54.74 mGy、57.49 mGy、61.44 mGy、64.19 mGy、67.67 mGy、71.16 mGy;不同扫描长度(100 mm、110 mm、120 mm、130 mm、140 mm)所对应的DLP分别为663 mGy、722 mGy、775 mGy、827 mGy、886 mGy;不同全剂量扫描时间窗宽度(15%、20%、25%、35%、40%、48%)所对应的CTDIvol分别为40.07mGy、42.35 mGy、44.34 mGy、48.98 mGy、51.12 mGy、54.67 mGy。2.通过统计学软件SPSS得到不同扫描参数与辐射剂量之间的关系。除kV与辐射剂量成二次方程的关系外,其余各扫描参数如mAs、扫描长度及全剂量扫描时间窗的宽度均与辐射剂量成正相关的线性关系。3.BMI与辐射剂量、mAs呈正相关的线性关系,当BMI <21时,采用100 kV、<320 mAs;当BMI>30时,采用140 kV、>380 mAs;当BMI介于21-30之间时,采用120 kV,mAs从320到380线性选择增长。4.通过对受检者的统计,心率越高的受检者其最佳重建期相越靠前,即越接近收缩末期。当心率小于60 bpm,其最佳重建期相介于65%-75%之间,当心率大于80 bpm,其最佳重建期相介于35%-50%之间,当心率位于60-80 bpm之间时,其最佳重建期相介于35%-75%之间。结论1.影响双源CT冠状动脉成像的辐射剂量因素,除了常规的管电压(kV)、管电流与扫描时间的乘积(mAs),扫描长度、扫描次数,还包括心率(HR)以及全剂量扫描时间窗的宽度。2.对于心率小于60 bpm或大于80 bpm的受检者,可采取前瞻性心电门控触发扫描模式,此模式为非螺旋扫描,且仅在一个心动周期内的固定期相产生X线,因此有效的降低了受检者的辐射剂量,但对心率及受检者的呼吸配合要求及其严格。3.对于心率介于60-80bpm的受检者或者心率不稳定的受检者,不宜采用前瞻性心电门控触发扫描模式,利用回顾性心电门控重建模式进行扫描,可改变相应的扫描参数来进行剂量控制。根据受检者的BMI,改变kV与mAs;根据受检者的心率,调节全剂量扫描时间窗。更多还原

【Abstract】 Objective1. Study and analysis all kinds of factors about radiation dose by experiment, while coronary artery angiography is imaged by dual-source computed tomography (DSCT).2. Get the relationship of radiation and its influencing factors by one statistics software (spss). Exactly, to get the fitted curve and eqution of radiation and its influencing factors.3. Obtain optimal scanning parameters to Reduce patient’s radiation dose of coronary artery angiography by DSCT.Methods1. The lung phantom (RS-330) inserted left coronary artery was scanned by DSCT. The scanning sequence was retrospectively ECG-Gated spiral scanning, in which heart rate was fitted 60 beats/min. The changing parameters were kV, mAs, scanning length, width of pulsing window. First of all, changed kV (80、100、120、140) and fitted other parameters while scanning. And then changed mAs (320、340、360、380、400、420) and fitted other parameters. Changed scanning length (100mm、110mm、120mm、130mm、140mm) and width of pulsing window (15%、20%、25%、35%、40%、48%) respectively. Recorded volume CT dose index (CTDIvol) and dose length product (DLP) of every scanning. Every dose was repeated 3 times and average value was calculated.2. The data got in first step was handing by spss, according to different scanning parameters. And then, the fitted curves and equtions of radiation dose (CTDIvol and DLP) and its infulencing factors were got.3. Recorded body mass index (BMI) of routine examiner randomly. Picked out the patient which all scannning parameters ( kV, mAs, scanning length and pitch ) were same. Then obtain the fitted curve and eqution of radiation dose and BMI by spss. According to the fitted eqution of kV, mAs and radiation dose, the relationship of BMI and kV, mAs was converted.According to this relation, kV and mAs was changed by BMI.4. Recorded heart rate and its optimal reconstructant pulse of routine examiner. Summarized the relationship of heart rate and the optimal reconstructant pulse. The scanning mode is selected according to it, prospectively ECG-triggered scanning or retrospectively ECG-Gated scanning. If retrospectively ECG-Gated scanning is used, how to set puling window by the relationship of heart rate and optimal recon pulse.Results1. CTDIvol (14.15 mGy、31.35 mGy、54.00 mGy、82.51 mGy) corresponded to Different kV(80、100、120、140). CTDIvol (54.74 mGy、57.49 mGy、61.44 mGy、64.19 mGy、67.67 mGy、71.16 mGy) corresponded to different mAs (320、340、360、380、400、420). DLP (663 mGy、722 mGy、775 mGy、827 mGy、886 mGy) corresponded to different scanning length (100mm、110mm、120mm、130mm、140mm). CTDIvol (40.07mGy、42.35 mGy、44.34 mGy、48.98 mGy、51.12 mGy、54.67 mGy) corresponded to different width of pulsing window (15%、20%、25%、35%、40%、48%).2. The relationships of radiation and various of scanning parameters were got by spss Most relations were linear positively except kV, such as mAs, scanning length, width of pulsing window and radiation. The relationship of kV and rediation was quadratic.3. The relationship of BMI and radiation dose, mAs all are linear positively. While BMI <21, 120 kV, <320mAs should be used; While BMI>30, 140kV、>380mAs should be used; While BMI is from 21 to 30, 120kV should used, mAs should be increase from 320 to 380.4. While heart rate is higher, the optimal reconstruction pulse is in the early part of an R-R interval, such as the last stage of systole. Optimal reconstruct pulse were 65%-75% while patient’s heart rate is lower than 60 beats per minute; Optimal reconstruct pulse were 35%-50% while patient’s heart rate is higher than 80 beats per minute. Optimal reconstruct pulse were 35%-75% while patient’s heart rate is 60-80 beats per minute.Conclusions1. The factors of influencing radiation dose are various. Besides conventional scanning parameters, such as kV, mAs, scanning length, scanning times, there are heart rate and width of pulsing window.2. If patient’s heart rate is lower than 60 bpm or higher than 80 bpm, the scanning mode may be prospectively ECG-triggered scanning. Prospectively ECG-triggering is limited to sequential scanning in a certain phase of the cardiac cycle. So it reduced radiation dose effectively. However, heart rate and holding patient’s breath is rigorous.3. If heart rate is higher than 60 bpm and lower than 80 bpm, or the heart rate fluctuate seriously. retrospectively ECG-Gated spiral scanning is better than prospectively ECG-triggered scanning. Retrospectively ECG-Gated spiral scanning should reduce radiation dose by changing scanning parameters. For instance, decreace kV and mAs by patient’s BMI; change width of pulsing window by patient’s heart rate.更多还原