低剂量CT肺部扫描技术值得提倡与推广

自 2 0世纪 70年代CT问世以来 ,经历了数次技术创新 ,如滑环CT、螺旋CT以及多层螺旋CT(MSCT)等 ,与X线胸片相比 ,明显提高了早期肺癌的检出能力 ,但其X线照射剂量也明显高于胸片 ,限制了CT在普通人群和肺癌高危人群筛查中的广泛应用。为了解决这一问题 ,Naidich等于 1990年首次提出了低剂量CT的概念 ,即在其他扫描参数不变的情况下 ,降低管电流成像亦能达到诊断要求。由于放射线剂量与X线球管呈线性关系 ,因此 ,降低管电流可使受检者的辐射剂量也相应下降。低剂量CT肺部扫描技术提出伊始尚未引起世人的注意 ,随着公众放射卫生和自…     

肺部低剂量螺旋CT扫描的应用

随着人们健康意识的增强，CT价格的降低，其肺部检查率将显著增长，其常规扫描CT球管的负荷将加大，在不影响诊断的前提下有效的降低管电流可延长其使用寿命，为医院节省开支，有效的降低了病人的辐射剂量。本文着重探讨低剂量螺旋CT扫描在胸部的应用。     

多层螺旋CT肺部低剂量扫描的应用价值

1990年的统计，显示在世界范围内肺癌已成为发病率与死亡率最高的恶性肿瘤。早发现早治疗，显然是降低肺癌死亡率的关键。本研究通过本院71例体检者肺部低剂量与常规剂量多层螺旋CT扫描图像的对照分析，探讨多层螺旋CT肺部低剂量扫描的应用价值。皆在寻找一种较科学、经济的肺部检查。     

低剂量螺旋CT肺部扫描对肺密度的评价

目的　探讨螺旋CT扫描剂量、层厚是否对肺密度有影响 ,以决定常规剂量螺旋CT扫描测得的肺密度值能否适用于低剂量螺旋CT。资料与方法　对 2 0名志愿者进行胸部螺旋CT扫描 ,采用 5种不同参数重复扫描 :低剂量 (5 0mA) ,层厚 8mm、5mm、3mm ;常规剂量 (2 0 0mA) ,层厚 5mm、3mm。分别在主动脉弓、气管隆突、下肺静脉干平面测量肺密度 (HU) ,计算不同剂量、层厚平均肺密度并进行统计学分析。结果　低剂量CT扫描 3种层厚中 8mm的肺密度值为 - 793± 4 5HU ,5mm为 - 80 0± 4 6HU ,3mm为 - 80 2± 5 1HU ,三者无统计学差异 (P >0 .0 5 ) ;层厚 5mm的肺密度值 ,低剂量为 - 80 0± 4 6HU ,常规剂量为 - 80 1± 37HU ,两者无统计学差异 (P >0 .0 5 ) ;层厚 3mm的肺密度值 ,低剂量为 - 80 2± 5 1HU ,常规剂量为 - 80 5± 4 9HU ,两者无统计学差异 (P >0 .0 5 )。结论　扫描剂量和层厚对肺密度没有显著影响 ,低剂量螺旋CT值可以参考常规剂量扫描测得的肺密度值来判断有无肺气肿等异常。     

多层螺旋CT肺部低剂量扫描的应用价值

目的：探讨多层螺旋CT肺部低剂量扫描的应用价值。材料和方法：对77例体检者行多层螺旋CT常规剂量肺部扫描后再行低剂量扫描,对照分析其质量。结果：77例受检者中,两种检查方法均发现异常35例,无异常42例,对病变征象和正常结构的显示率均为45%和55%,图像质量均为优。低剂量扫描较常规剂量扫描的X线剂量少。结论：肺部多层螺旋CT低剂量扫描能提供与常规剂量扫描相近的诊断与鉴别诊断信息,适用于大规模体检及高危人群普查。     

低剂量高分辨CT扫描在肺部病变诊断中的应用价值

近年来,随着环境污染不断加剧,肺部病变发生率也呈现上升趋势,严重影响患者的生活质量。肺部病变属于临床常见疾病,其起病隐匿,发病早期通常无明显症状,部分患者可能伴有胸痛、咯血等症状,就诊时多已发展至中晚期,患者预后较差[1]。目前,临床上常用的肺部病变诊断方法包括穿刺活检、X线片、CT等,其中穿刺活检敏感度较高,但其有创性使部分患者无法接受[2];X线片敏感度较低,且可能受到呼吸伪影的影响[3]。而CT扫描的密度分辨率较高,可对病变范围、大小及性质进行准确定位,但常规高分辨CT放射剂量较大,致畸性高[4]。基于此,本研究主要探讨低剂量高分辨CT扫描在肺部病变诊断中的应用价值。现报告如下。     

低剂量CT扫描对乳突病变的临床应用研究

目的：探讨低剂量高分辨率CT扫描对乳突病变的诊断价值。方法：低利量50mA扫描30例，其基准线为上颌窦后壁平行线做周围螺旋扫描，与用100mA常规扫描的30例进行比较，对图像质量及对诊断的影响进行评估。结果：低剂量组30例中良好片25张，占83．3％，一般片5张，占16.7％，差片0，与常规组基本一致。结论：低利量高分辨率CT扫描完全能满足临床对乳突病变的诊断要求。该扫描方法降低病人单次检查的接受辐射剂量，能延长球管的寿命，从而降低医疗成本，值得推广应用。     

低剂量CT扫描技术的胸部应用

1990年Naidich等 [1]率先提出低剂量CT扫描技术 ,1995年Mayo等[2 ]的研究表明 ,当毫安秒低于 80mAs时 ,图像质量有显著下降。他们的临床应用实践为低剂量CT扫描技术的胸部应用打开了前景。随着CT技术的不断完善 ,在不影响图像质量情况下 ,使得低剂量检查成为可能。笔者在分析60例低剂量扫描成像质量的基础上 ,将该技术在胸部检查中的应用作一评价 ,现报道如下。一、材料和方法1 材料 :选择有咳嗽 ,咯痰 ,胸痛等呼吸道症状者 ,可疑肺内有病变者 60例 ,男 44例 ,女 16例 ,年龄 2 3～ 78岁 ,平均55岁。2 仪器 :北京医疗器械研究所生产的B…     

Effect of reconstruction algorithm on image quality and identification of ground-glass opacities and partly solid nodules on low-dose thin-section CT: Experimental study using chest phantom

Purpose

The purpose of this study was to assess the influence of reconstruction algorithm on identification and image quality of ground-glass opacities (GGOs) and partly solid nodules on low-dose thin-section CT.

Materials and methods

A chest CT phantom including simulated GGOs and partly solid nodules was scanned with five different tube currents and reconstructed by using standard (A) and newly developed (B) high-resolution reconstruction algorithms, followed by visually assessment of identification and image quality of GGOs and partly solid nodules by two chest radiologists. Inter-observer agreement, ROC analysis and ANOVA were performed to compare identification and image quality of each data set with those of the standard reference. The standard reference used 120 mA s in conjunction with reconstruction algorithm A.

Results

Kappa values (κ) of overall identification and image qualities were substantial or almost perfect (0.60 < κ). Assessment of identification showed that area under the curve of 25 mA reconstructed with reconstruction algorithm A was significantly lower than that of standard reference (p < 0.05), while assessment of image quality indicated that 50 mA s reconstructed with reconstruction algorithm A and 25 mA s reconstructed with both reconstruction algorithms were significantly lower than standard reference (p < 0.05).

Conclusion

Reconstruction algorithm may be an important factor for identification and image quality of ground-glass opacities and partly solid nodules on low-dose CT examination.     

基于感染防控的新型冠状病毒肺炎低剂量CT扫描方案的临床应用研究

目的 探讨感染防控下新型冠状病毒（COVID-19）肺炎低剂量CT扫描方案的临床应用。方法 分析2020年1月20日到2020年2月28日在华中科技大学同济医学院附属协和医院确诊的COVID-19病例的CT影像140例,将患者分为低剂量组和常规剂量组。低剂量组（120 kV,31 mAs）70例,其中轻症51例,重症15例,危重症4例;常规剂量组（120 kV,自适应毫安秒）70例,其中轻症48例,重症17例,危重症5例。比较两组病例有效剂量（E）、图像信噪比（SNR）、对噪比（CNR）,由两位高、中年资影像诊断医生对图像进行主观评分。结果 低剂量组和常规剂量组E比较,差异有统计学意义（t=-48.343,P<0.05）。低剂量组的SNR和常规剂量组的SNR比较,差异无统计学意义（P>0.05）。低剂量组的CNR和常规剂量组的CNR比较,差异无统计学意义（P>0.05）。主观评价均满足诊断需求,轻症患者中,低剂量组和常规剂量组的影像主观评分比较,差异无统计学意义（P>0.05）;重症与危重患者中,低剂量组和常规剂量组的影像主观评分比较,差异有统计学意义（t=-2.781,P<0.05）;但两组图像均符合诊断要求。结论 对COVID-19患者进行低剂量CT扫描,可在满足诊断需求的前提下降低患者辐射剂量。     

头部体模扫描试验对成人头颅CT低剂量扫描的优化初探

目的：通过对头部体模扫描试验,探讨成人头颅CT低剂量扫描参数。方法：以层厚10 mm,扫描时间为1 s,通过改变mA值,以10 mA为间隔,20-300 mA间29个不同mA条件对头部体模进行轴向扫描,对容积CT剂量指数（CTDIvol）、噪声（SD）和对比-噪声比（CNR）进行客观评价分析与统计学处理,对图像低密度分辨力进行主观评价。结果：①CTDIvol随mAs增大而增大,呈线线关系;与300 mAs的CTDIvol（42 mGy）比较,80-150 mAs的CTDIvol（11-21 mGy）下降73%-50%。②SD值随mAs升高而降低;SD值随mAs变化曲线可分为SD改变非常显著段（20-50 mAs）、显著段（50-80 mAs）、缓坡段（90-150 mAs）和平缓段（160-300 mAs）。③CNR随mAs改变与SD值改变相反。④SD值与CNR统计学处理：20 mAs与30 mAs、30 mAs与50 mAs5、0 mAs与80 mAs、80 mAs与150 mAs、150 mAs与300 mAs的各SD值及CNR有统计学差异（P〈0.05）;160-300 mAs的各SD值与CNR无统计学差异（P〉0.05）。⑤图像LCR主观评价：20-50 mAs,分辨低密度圆柱体困难;50-80 mAs,主观图像质量明显下降,图像对诊断有影响;90-150 mAs主观图像质量有一定改变;160-300 mAs主观图像质量改变不明显。结论：80-150 mAs为低对比要求较高的成人颅脑低剂量平扫可用区间,为临床降低扫描剂量提供了依据。临床患者检查,可以用100 mAs进行平扫,CT剂量指数明显降低。     

64层CT容积与常规高分辨率CT图像质量的比较

目的 比较容积高分辨率CT(VHRCT)与常规高分辨率CT(CHRCT)的图像质量,探讨VHRCT的可行性.方法 对Catphan 412模具行VHRCT及CHRCT扣描,测量和记录图像的空间分辨率、噪声及放射剂量并进行比较;对32例患者行VHRCT及CHRCT检查,对图像质量进行评分并比较.模具部分采用配对t检验比较噪声的差异;临床部分采用Wilcoxon配对符号秩和检验比较图像质量的差异.结果 模具研究中,VHRCT横断面图像的空间分辨率与CHRCT相同,均为11 LP/cm,其z轴分辨率为12 LP/cm.剂量相近时,VHRCT的噪声为(69.18±2.77)HU,大于CHRCT的噪声(54.62±2.12)HU,(t=-15.929,P＜0.01);噪声相近时,VHRCT的剂量较CHRCT增加19.09 mGy.临床研究中,VHRCT与CHRCT横断面图像的质量评分分别为3.22与3.24,差异无统计学意义(Z=-0.319,P＞0.05),VHRCT与CHRCT冠状面蕈建图像的质量评分分别为3.05与1.88,差异有统计学意义(Z=-5.088,P＜0.01).结论 对于64层CT,VHRCT的横断面图像质量接近CHRCT,多平面重组图像具有高分辨率可广泛应用,其扫描剂量尚有待优化.     

容积高分辨CT对肺弥漫病变显示能力的评价

目的 评价容积高分辨CT (VHRCT)对肺弥漫病变的显示能力,探讨VHRCT取代传统高分辨CT (CHRCT)的可行性.资料与方法 102例肺弥漫病变患者行VHRCT及CHRCT检查,比较二者的图像质量,包括图像的伪影、分辨能力及噪声水平:选择无明显呼吸伪影的层面,比较二者对于线状影及网状影、微结节影及树芽征、细支气管扩张、磨玻璃影、肺气肿5种肺弥漫病变征象的显示情况.结果 图像质量比较:VHRCT与CHRCT的图像分辨能力及噪声水平差异均无统计学意义(P=0.317,P=0.091);CHRCT的呼吸伪影较VHRCT明显,二者伪影评分差异有统计学意义(P=0.008).在无明显呼吸伪影的层面中,VHRCT与CHRCT对线状影及网状影、微结节影及树芽征、细支气管扩张、磨玻璃影、肺气肿显示情况评分差异均无统计学意义(P=0.729,P=0.603,P=0.189,P=0.672,P=0.541).结论 VHRCT对于肺弥漫病变的显示能力与CHRCT接近,可以通过一次螺旋扫描得到全肺的高分辨率图像,其取代CHRCT具有可行性.     

Comparison of low-dose CT and MR for measurement of intra-abdominal adipose tissue: a phantom and human study

RATIONALE AND OBJECTIVES: The aim of this study was to determine the accuracy and reproducibility of low-dose computed tomography (CT) and magnetic resonance (MR) for abdominal adipose tissue quantification on phantom and human studies. MATERIALS AND METHODS: An adiposity phantom (with known internal/external oil volumes) was scanned at three different tube voltages (140, 120, and 90 kVp) using a 16-detector row CT scanner and was imaged using a T1-weighted spin echo MR sequence. For human studies, whole-volume coverage of the abdomen was obtained using CT (at 140 and 90 kVp) and T1-weighted spin echo MR imaging from five obese male volunteers (mean age, 40.6 years; mean body mass index, 30.2). The volumes of total, visceral, and subcutaneous adipose tissues (TAT, VAT, and SAT, respectively) were calculated independently by two radiologists for each CT scan and MR imaging using a computer-aided semiautomatic program. RESULTS: The estimated radiation dose could be reduced by approximately 75% with a 90-kVp protocol as compared with the 140-kVp protocol. Phantom studies showed that there was no statistically significant difference between the four methods in estimating the percentage predicted of the true volumes (measurement errors <4% for all methods, P > .05). In human studies, we found no statistically significant difference between the three methods in TAT, VAT, and SAT volumes (P > .05). Inter- and intraobserver reproducibilities of the CT volume estimates using the 90-kVp protocol were better than those obtained from MR imaging (kappa > 0.9 versus 0.4-0.5; coefficient of variation < 1% versus 15-22%). CONCLUSION: Low-dose CT provides accurate and reproducible measurement of abdominal adipose tissue volumes with a relevant dose reduction.     

Influence of detector collimation and beam pitch for identification and image quality of ground-glass attenuation and nodules on 16- and 64-detector row CT systems: experimental study using chest phantom

OBJECTIVE: The purpose of the present study was to determine the influence of detector collimation and beam pitch for identification and image quality of ground-glass attenuation (GGA) and nodules on 16- and 64-detector row CTs, by using a commercially available chest phantom. MATERIALS AND METHODS: A chest CT phantom including simulated GGAs and nodules was scanned with different detector collimations, beam pitches and tube currents. The probability and image quality of each simulated abnormality was visually assessed with a five-point scoring system. ROC-analysis and ANOVA were then performed to compare the identification and image quality of either protocol with standard values. RESULTS: Detection rates of low-dose CTs were significantly reduced when tube currents were set at 40mA or less by using detector collimation 16 and 64x0.5mm and 16 and 32mmx1.0mm for low pitch, and at 100mA or less by using detector collimation 16 and 64x0.5mm and 16 and 32mmx1.0mm for high pitch (p<0.05). Image qualities of low-dose CTs deteriorated significantly when tube current was set at 100mA or less by using detector collimation 16 and 64x0.5mm and 16 and 32x1.0mm for low pitch, and at 150mA or less by using detector collimation 16 and 64x0.5mm and 16 and 32x1.0mm for high pitch (p<0.05). CONCLUSION: Detector collimation and beam pitch were important factors for the image quality and identification of GGA and nodules by 16- and 64-detector row CT.     

Low dose multi-detector CT of the chest (iLEAD Study): Visual ranking of different simulated mAs levels

Purpose

Detailed evaluation of the lung parenchyma might be impaired by use of low dose CT as image noise increases and subsequently image quality decreases. The aim of our study was to determine the accuracy of visual perception of differences in image quality and noise at low dose chest CT.

Materials and methods

Forty-four patients suffering from emphysema underwent CT (Aquilion-16, 120 kV, 150 mAs, 1 mm-collimation). Original raw data were used for simulation of 10 different mAs settings from 10 mAs to 100 mAs in 10 mAs increments. Three representative hard copy images (carina, 4 cm above, 5 cm below) were printed for evaluation of lung parenchyma (high-resolution kernel, lung window) and mediastinum (soft-kernel, soft tissue window). Ranking of expected low mAs level was performed for lung and soft tissue separately based on visual perception by three-blinded chest radiologist independently. Results were compared to the real simulated mAs.

Results

The accuracy for correct ranking of the original 150 mAs scan was 89% for lung and 86% for soft tissue while it was 99% for the simulated 10 mAs for both windows. In comparison to the lowest mAs a significant error increase was found for the lung at 60-100 mAs (with error increase of 30-47%) for reader-I; 60-100 mAs for (33-64%) for reader-II and 70-100 mAs (38-57%) for reader-III. For the soft tissue: 60-150 mAs (with error increase of 28-63%) for reader-I; 50-100 mAs (35-56%) for reader-II and 50-90 mAs (35-40%) for reader-III.

Conclusion

Simulated dose levels below 60 mAs (=42 mAs_eff) were clearly differentiated from higher dose levels by all readers. Therefore, imaging doses could be lowered down to 60 mAs without a diagnostically relevant increase in noise impairing image quality.     

64层螺旋CT肺部高分辨率图像质量影响因素的体模研究

目的 分析影响肺部高分辨率CT(HRCT)图像质量的主要因素,探讨常规肺部容积扫描条件下获得HRCT图像质量的可行性.方法 应用64层CT对Catphan500模具进行连续、重复扫描.对比内容:扫描方式(轴面扫描、螺旋扫描)、kV值(140、120 kV)、层厚(1.25、5.00 mm,其中5.00 mm图像折分为1.25 mm)、重建算法(骨+算法、肺算法).评价内容:空间分辨率、密度分辨率、图像噪声.统计分析采用析因设计方差分析.结果 扫描方式在密度分辨率(轴面扫描:11.44±0.04;螺旋扫描:12.61±0.04)、图像噪声(轴面扫描:5.89±0.05;螺旋扫描:6.92±0.05)上差异均有统计学意义(F值分别为539.61、179.02,P值均＜0.01),轴面扫描密度分辨率高于螺旋扫描,图像噪声低于螺旋扫描;重建算法间在空间分辨率(骨+:9.90±0.09;肺:7.40±0.09)、密度分辨率(骨+:11.39±0.04;肺:12.65±0.04)、图像噪声(骨+:6.55±0.05;肺:6.28±0.05)上差异均具有统计学意义(F值分别为375.00、627.95、13.97,P值均＜0.05),骨+算法优于肺算法但噪声值略高.结论 容积扫描在密度分辨率、图像噪声控制上较传统HRCT稍差,但在空间分辨率上容积扫描骨+算法重建与HRCT图像质量相当,用于显示肺内细节时容积高分辨率CT可代替常规HRCT.