ISSN 1004-4140
CN 11-3017/P

不同管电压联合器官剂量调制技术对脑灌注图像质量及眼晶体辐射剂量的影响研究

Study on the Impact of Different Tube Voltages Combined with Organ Dose Modulation on Cerebral Perfusion Image Quality and Ocular Lens Radiation Dose

  • 摘要: 目的:探讨不同管电压下启用器官剂量调制(ODM)技术在颅脑灌注CT(CTP)中对图像质量及眼晶体辐射剂量的影响。方法:以临床CTP扫描方案为基准,在其他参数相同情况下分别使用5种管电压(70、80、100、120、140 kV)对Catphan模体和一具新鲜离体头颅标本进行3种管电流调制模式的扫描:不使用剂量调制技术(Manual模式)、使用智能管电流调制技术(Smart mA模式)、使用器官剂量调制技术(ODM模式)。在右眼晶体前方相同位置固定长杆电离室,每组参数重复9次扫描,记录平均眼晶体剂量值(Dav)。对Catphan模体中CTP528高对比分辨力模块进行调制传递函数(MTF)的测量。在头颅标本影像中的基底节层面选取尾状核头、豆状核、丘脑作为信号区,选取侧脑室、内囊前肢、内囊后肢作为对应背景区,测算对比度噪声比(CNR)。分割同层面脑组织测量纹理对比度、纹理相关性、差分方差等三项纹理特征参数。对MTF、CNR的比较采用两因素方差分析,对晶体剂量、图像纹理的比较采用多因素非参数方差分析。结果:MTF在不同管电压间差异具有统计学意义,在80 kV以上时其值与管电压呈正相关,在不同管电流调制模式间差异无统计学意义。各信号区与背景区间的CNR在不同管电压间差异均有统计学意义,其中尾状核头-侧脑室的CNR值在120 kV时最大。后两者的CNR值与管电压呈负相关。三者的CNR值在不同管电流调制模式间差异均无统计学意义。各纹理参数与管电流调制模式无关。不同管电压和管电流调制模式下的Dav值差异均存在统计学意义,在管电压120 kV以下时晶体剂量与管电压呈负相关,各管电压下ODM技术均可降低约20%的晶体剂量。结论:使用80至100 kV进行CTP扫描并启用器官剂量调制(ODM)技术可均衡图像的各参数指标,在保证图像质量前提下降低眼晶体辐射剂量,建议临床推广使用。

     

    Abstract: Objective: To investigate the effect of using organ dose modulation (ODM) technology at different tube voltages on image quality and eye lens radiation dose in brain perfusion CT (CTP). Methods: Based on a clinical CTP scanning protocol, five tube voltages (70, 80, 100, 120, and 140 kV) were used to scan a Catphan phantom and a fresh, isolated human head specimen with three tube current modulation modes: without dose modulation technology (Manual mode), with smart tube current modulation technology (Smart mA mode), and with organ dose modulation technology (ODM mode). A long rod ionization chamber was fixed at a consistent position in front of the right eye lens. Each parameter combination was scanned nine times, and the average eye lens dose (Dav) was recorded. The modulation transfer function (MTF) of the CTP528 high-contrast resolution module in the Catphan phantom was measured. In the images of the head specimen, the heads of the caudate nucleus, lenticular nucleus, and thalamus were selected as signal regions at the basal ganglia level, and the lateral ventricle, anterior limb of the internal capsule, and posterior limb of the internal capsule were selected as respective background regions to measure the contrast-to-noise ratio (CNR). The same level of brain tissue was segmented to measure three texture feature parameters: contrast, correlation, and difference variance. Two-factor analysis of variance was used to compare MTF and CNR, and multi-factor non-parametric analysis of variance was used to compare eye lens dose and texture parameters. Results: The differences in MTF across the different tube voltages were statistically significant , with MTF values positively correlated with tube voltage above 80 kV. However, there was no significant difference between different tube-current modulation modes. The CNR of each signal and background region showed significant differences among different tube voltages. The CNR for the caudate nucleus head to lateral ventricle was the largest, at 120 kV. The CNR for the lenticular nucleus/thalamus were negatively correlated with tube voltage. There were no significant differences in CNR among different tube-current modulation modes. No texture parameter was significantly associated with the tube current modulation mode. There were significant differences in Dav values with respect to both different tube voltages and tube current modulation modes. When the tube voltage was below 120 kV, the eye lens dose was negatively correlated with tube voltage, and the ODM technology reduced the eye lens dose by approximately 20% at each tube voltage. Conclusion: Employing 80–100 kV CTP scanning with organ dose modulation technology can balance image parameters and reduce radiation dose to the eye lens while ensuring adequate image quality, as recommended for clinical use.

     

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