宽体探测器CT不同扫描方式对体模图像质量影响的初步研究  

Preliminary study on the effects of different scanning methods on phantom image quality in a wide-body detector CT scanner

作　　者：亓慧 崔丁也[2] 李伟[2] Qi Hui;Cui Dingye;Li Wei(Graduate School,Shandong First Medical University and Shandong Academy of Medical Sciences,Jinan 250117,China;Department of Radiology,The First Affiliated Hospital of Shandong First Medical University&Shandong Provincial Qianfoshan Hospital,Jinan 250014,China)

机构地区：[1]山东第一医科大学、山东省医学科学院研究生部,济南250117 [2]山东第一医科大学第一附属医院、山东省千佛山医院放射科,济南250014

出　　处：《中华放射医学与防护杂志》2024年第7期622-627,共6页Chinese Journal of Radiological Medicine and Protection

基　　金：山东省科技发展计划(2014GSF118091);山东省医药卫生发展计划(2017WS715)。

摘　　要：目的利用体模探究宽体探测器CT使用不同的扫描模式和探测器宽度时对图像质量和辐射剂量的影响。方法使用320排CT在不同扫描方式下对Catphan500模体的CTP404和CTP486模块进行扫描,并将每个模块置于扫描野的中心位置。轴扫模式时,分别选择80、120、140和160 mm探测器准直宽度;螺旋扫描模式时,选择40和80 mm。两种扫描模式的管电流均选择240和100 mAs。采用基于任务的传递函数(TTF)来衡量空间分辨率,以噪声功率谱(NPS)衡量噪声的imQuest软件进行客观评价,并记录图像的特征数据和CT容积剂量指数(CTDI_(vol))值。结果扫描模式对图像的空间分辨率和噪声有主要影响。对于空间分辨率,轴扫模式的TTF曲线较螺旋扫描模式略右移,表明轴扫模式具有更高的空间分辨率;对于噪声,NPS峰值频率和平均空间频率提示两种扫描模式的噪声纹理相似,但噪声值和NPS曲线下面积一致均提示轴扫模式的噪声更低,轴扫模式较螺旋扫描模式噪声降低14%,曲线下面积减少26%。轴扫模式图像质量优于螺旋扫描模式,辐射剂量降低约13%。虽然探测器准直宽度对高对比度分辨率和噪声无明显影响,但随着探测器宽度的增加,CTDI_(vol)值有所减低,轴扫模式下当探测器准直宽度增加1倍时,CTDI_(vol)减少了9%。结论不同的扫描方式对图像质量和辐射剂量具有一定的影响,尤其是扫描模式。在临床上应该根据扫描部位以及诊断要求选择适合的扫描方式。Objective To explore the effects of different scan modes and detector widths on image quality and radiation dose in a wide-body detector CT scanner using phantoms.Methods A 320-row CT scanner was used to scan Catphan500 CTP404 and CTP486 modules under different scan modes,during which each module was positioned in the center of the scanning field.On the axial scan,the detector collimating width options of 80,120,140,and 160 mm were applied successively;on the helical scan,the options of 40 and 80 mm were applied.Tube currents of 240 and 100 mAs were used for both scan modes.The imQuest software,which measures spatial resolution by task-based transfer function(TTF)and noise by noise power spectrum(NPS),was used for objective evaluation,and feature data and CTDI_(vol)values of images were recorded.Results Scan modes had a significant effect on the spatial resolution and noise of images.For spatial resolution,the TTF curve on the axial scan shifted slightly to the right compared with that on the helical scan,suggesting the association between axial scan and higher spatial resolution;for noise,the NPS peak frequency and average spatial frequency revealed a similar noise texture with the two scan modes,but the noise value and the identical area under the NPS curve suggested that axial scan was less noisy.It had 14%less noise,26%less area under the curve,better image quality,and about 13%less radiation dose on axial scan than those on spiral scan.The detector collimating width had no significant effect on high contrast resolution and noise,but CTDI_(vol)decreased with its increase,and CTDI_(vol)reduced by 9%when it was doubled on the axial scan.Conclusions Different scanning method have certain effects on image quality and radiation dose,especially scan modes.In clinical practice,it is required to choose an appropriate scanning method based on the scanning sites and diagnostic requirements.

关 键 词：探测器宽度 扫描模式 空间分辨率 噪声 

分 类 号：R812[医药卫生—放射医学]