Singh Shilpa, Sukkala Rajesh
Department of Radiology, Maharishi Markandeshwar (Deemed to be University), Ambala, Haryana, India.
Department of Radiology, Centurion University, Vizianagaram, Andhra Pradesh, India.
J Carcinog. 2021 Sep 23;20:13. doi: 10.4103/jcar.JCar_25_20. eCollection 2021.
Radiation dose in computed tomography (CT) has been the concern of physicists ever since the introduction of CT scan. The objective of this study was to evaluate the performance of low-dose 128-slice CT scanner with different mAs values.
Quantitative study was carried out at different values of mAs. Philips brilliance CT phantom with Philips ingenuity 128-slice low-dose CT scanner was chosen for this study. CT number linearity, CT number accuracy, slice thickness accuracy, high-contrast resolution, and low-contrast resolution were calculated and estimated computed tomography dose index volume (CTDI) for all the mAs values were recorded. Noise was calculated for all mAs values for comparison.
Data analysis shows that image quality was acceptable for all protocols. High-contrast resolution for all protocols was 20 line pairs per centimeter. Low-contrast resolution for 50 mAs images was 4 mm and 3 mm for other mAs protocols. Images acquired using 100 mAs revealed ring artifacts. CTDI using 50 mAs was 33% of the CTDI using 150 mAs. The dose-length product at 100 mAs was reduced to 66% of the dose-length product at 150 mAs, and the same at 50 mAs was reduced to 33%.
It is evident here that mAs has direct impact on the radiation dose to patient. With iDose4, mAs can be reduced to 50 mAs in multislice low-dose CT scan to reduce the radiation dose with minimal effect on image quality for slice thickness 4 mm. However, noise would dominate at tube current lower than 50 mAs for 120 kVp.
自计算机断层扫描（CT）问世以来，CT辐射剂量一直是物理学家关注的问题。本研究的目的是评估不同毫安秒（mAs）值下低剂量128层CT扫描仪的性能。
在不同mAs值下进行定量研究。本研究选用配备飞利浦智能128层低剂量CT扫描仪的飞利浦Brilliance CT体模。计算CT值线性、CT值准确性、层厚准确性、高对比度分辨率和低对比度分辨率，并记录所有mAs值下的估计计算机断层扫描剂量指数体积（CTDI）。计算所有mAs值下的噪声以作比较。
数据分析表明，所有扫描方案的图像质量均可接受。所有扫描方案的高对比度分辨率均为每厘米20线对。50 mAs图像的低对比度分辨率为4 mm，其他mAs扫描方案的低对比度分辨率为3 mm。使用100 mAs采集的图像出现环形伪影。50 mAs时的CTDI为150 mAs时CTDI的33%。100 mAs时的剂量长度乘积降至150 mAs时剂量长度乘积的66%，50 mAs时的剂量长度乘积降至33%。
显然，mAs对患者接受的辐射剂量有直接影响。使用iDose4技术，在多层低剂量CT扫描中mAs可降至50 mAs，以降低辐射剂量，同时对4 mm层厚的图像质量影响最小。然而，对于120 kVp，管电流低于50 mAs时噪声将占主导。
