The Radiation Dose Control In Coronary Artery Angiography Of DSCT

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.