肥胖患者80kV不同级别迭代重建技术CTPA图像质量分析

目的评估80kV条件下不同级别迭代重建技术对肥胖患者CT肺动脉造影(CTPA)图像质量的影响。方法收集临床疑似肺栓塞并行CTPA检查的肥胖患者40例,采用滤波反投影(FBP)及3个级别的迭代重建技术(iDose~1:20%IR/80%FBP;iDose~3:40%IR/60%FBP;iDose~5:60%IR/40%FBP)重建图像。测量图像的肺动脉主干、右肺上叶动脉及右肺下叶后基底段动脉CT值、噪声,计算并比较4组数据的噪声、SNR及CNR。结果 4组重建图像噪声、SNR及CNR差异均有统计学意义(P均0.001),图像噪声两两比较差异均有统计学意义(P均0.05);FBP组的SNR及CNR与iDose~3组和iDose~5组比较,差异有统计学意义(P0.01)。结论与FBP比较,80kV联合不同级别IR技术可明显降低CTPA图像噪声,提高图像质量,并可进一步降低肥胖患者接受的辐射剂量。     

应用iDose4软件对低剂量胸部CT增强扫描图像质量的影响

目的评价将iDose4迭代重建（IR）技术用于胸部低剂量增强扫描的可行性。方法选取71例体质量指数（BMI）正常（18.5≤BMI〈25.0kg/m2）且接受胸部CT增强扫描的患者,随机分为A组（120kVp,100 mAs）、B组（80kVp,100mAs）、C组（120kVp,50mAs）,分别采用iDose4 IR技术和FBP进行重建,记录各组的噪声、SNR、CNR和有效剂量（ED）。按1～3分评价各组总体图像质量,并对3组结果进行比较。结果比较同一个患者的FBP和IR图像,IR技术明显降低了图像的噪声,提高了图像的SNR、CNR。B、C组IR后的图像噪声、SNR和CNR与A组FBP图像比较差异均无统计学意义（P均〉0.05）。B、C组IR后的图像总体质量与A组FBP重建图像质量差异无统计学意义（P〉0.05）。结论运用IR技术进行低剂量胸部CT增强扫描可获得满足诊断要求的图像。     

迭代重建算法在肥胖患者冠状动脉CT成像中的应用

目的 与滤波反投影法(FBP)相比,观察正弦图确认的迭代重建算法(SAFIRE)可否改善肥胖患者冠状动脉CTA(CTCA)图像质量及有效降低辐射剂量.方法 连续收集49例接受CTCA的肥胖患者,对其中39例使用常规序列扫描(120 kV,A组),分别选用FBP(FBP亚组)和SAFIRE(SAFIRE亚组)重建;对另10例使用低剂量扫描序列(100 kV,B组),SAFIRE重建.比较各组间主观(冠状动脉评分)和客观图像质量(图像噪声,SNR,CNR)的差异.结果 SAFIRE亚组的图像噪声、SNR、CNR比均优于FBP亚组和B组(P＜0.05),但FBP亚组的图像主观评分与B组差异无统计学意义.B组的有效辐射剂量[(4.36±0.75) mSv]明显小于A组[(8.83±1.74) mSv] (P＜0.01).结论 与FBP相比,SAFIRE可显著提高相同剂量水平的CTCA图像质量,并能在降低约50％辐射剂量的条件下保证图像质量.     

智能最佳管电压调节技术在儿童埋伏牙CT扫描中的应用

目的探讨双源CT智能最佳管电压调节(CARE kV)技术在儿童埋伏牙扫描中的应用价值。方法对90例埋伏牙患儿行CT扫描,并分为A、B、C 3组,每组30例,A组常规扫描(100kVp/150mAs),B组开启CARE Dose 4D扫描(100kVp/参考管电流150 mAs),C组CARE kV联合CARE Dose 4D扫描(参考管电压100kV/参考管电流120mAs)。比较3组的辐射剂量、图像平均CT值、噪声、SNR、CNR、主观评分及CT诊断与临床诊断的差异。结果 3组实际扫描管电流、管电压及辐射剂量差异均有统计学意义(P均0.05),与A组比较,B组有效剂量(ED)减低约15.74%,C组ED减低26.85%;图像的平均CT值、噪声、SNR、CNR及主观评分比较差异均无统计学意义(P均0.05);3组CT与临床诊断结果比较差异无统计学意义(P0.05)。结论采用双源CT智能最佳管电压调节技术行儿童埋伏牙CT扫描,可有效降低辐射剂量,在保证图像质量的同时,不影响诊断。     

迭代重建算法前瞻性心电门控大螺距肺动脉双源CT成像的图像质量

目的与滤波反投影(FBP)算法比较,探讨基于原始数据的迭代重建(SAFIRE)算法大螺距肺动脉双源CT(DSCT)成像的图像质量。方法对临床怀疑肺栓塞的69例患者行前瞻性心电门控大螺距肺动脉CT扫描,分别采用SAFIRE和FBP算法进行图像重建,比较两种重建算法的肺动脉CT图像质量、噪声、SNR和CNR。结果 SAFIRE算法图像的肺动脉CT图像质量显著优于FBP算法[图像质量评分分别为(1.28±0.36)分和(1.99±0.56)分,P<0.001];SAFIRE算法的噪声显著低于FBP算法[分别为(14.60±2.11)HU和(18.52±2.65)HU,P<0.001];SAFIRE算法的SNR和CNR显著高于FBP算法(SNR分别为26.57±4.99和20.23±3.94,P<0.001;CNR分别为23.41±4.58和17.77±3.62,P<0.001)。结论前瞻性心电门控大螺距肺动脉DSCT成像时,与FBP算法相比,SAFIRE算法的肺动脉CT图像噪声更低,图像质量更高,显示肺动脉细小分支更佳。     

能谱纯化结合高级模拟迭代重建在成人胸部低剂量CT中的应用

目的探讨第3代双源CT能谱纯化结合高级模拟迭代重建(ADMIRE)技术在成人胸部低剂量CT检查中的应用价值。方法将100名成年体检者随机均分为A组和B组,采用Siemens Force双源CT扫描仪行胸部CT检查。对A组采用常规100kV扫描结合ADMIRE(强度3级)重建(获得A-ADMIRE图像),B组采用能谱纯化(Sn 100kV)扫描结合ADMIRE(强度1~5级)重建(分别获得B-ADMIRE1、B-ADMIRE2、B-ADMIRE3、B-ADMIRE4、B-ADMIRE5图像)。肺窗及纵隔窗图像ROI包括肺组织、胸主动脉、竖脊肌、背部皮下脂肪及背景空气。比较2组间辐射剂量指标的差异及2组不同ADMIRE图像间客观评价指标、主观图像质量评分的差异。结果 B组CT剂量指数(CTDIvol)、剂量长度乘积(DLP)及有效剂量(ED)均较A组明显下降(P均0.01)。2组不同ADMIRE图像间肺窗及纵隔窗各ROI图像噪声差异均有统计学意义(P均0.01),其中B-ADMIRE1图像噪声最高;肺组织、胸主动脉、竖脊肌信噪比(SNR)及肺组织-背部皮下脂肪、胸主动脉-竖脊肌、胸主动脉-背部皮下脂肪对比噪声比(CNR)差异均有统计学意义(P均0.01),其中AADMIRE图像SNR、CNR最高。B组中ADMIRE1~5图像噪声呈逐级递减趋势,SNR及CNR均呈逐级递增趋势(P均0.01)。2组不同ADMIRE图像间肺窗及纵隔窗图像质量评分差异均有统计学意义(P均0.01),其中AADMIRE图像质量评分最高。B组中B-ADMIRE3图像肺窗及纵隔窗图像质量评分最高,分别为(3.89±0.26)分和(3.00±0.15)分,均可满足诊断要求。结论成人胸部低剂量CT检查中,采用能谱纯化结合ADMIRE技术可在满足诊断要求的同时有效减低辐射剂量,且ADMIRE 3级强度重建图像质量最佳。     

迭代重建技术在新生儿急诊头颅CT检查中的应用

目的探讨迭代重建(IRIS)技术在新生儿急诊头颅CT检查中的临床应用价值。方法收集本院40例临床怀疑颅内出血并接受急诊头部CT常规剂量平扫的的足月新生儿,分别采用滤波反投影法(FBP组)及IRIS法(IRIS组)进行重建;比较两组图像的噪声、SNR及灰白质CNR,并以4分分级法对两组图像的主观噪声、颅底伪影、灰白质对比及病变显示进行主观评价。结果 IRIS组的图像噪声(1.13±0.15)明显低于FBP组(1.70±0.17,P<0.05),IRIS组的SNR(18.26±3.18)及CNR(6.97±2.42)均高于FBP组(12.58±1.86,4.41±1.52,P均<0.05)。IRIS组图像质量主观评价积分明显高于FBP组(P<0.05)。结论应用IRIS技术可明显改善急诊新生儿头颅CT检查中的图像质量。     

双源CT低剂量扫描在上腹部增强检查中的应用

目的探讨双源CT上腹部增强扫描中低剂量技术的应用。方法搜集2011年7月至2012年2月期间来我院行双源CT上腹部增强检查的连续600例患者,按就诊时间先后分别依次采用常规管电流量(210 mAs)和低管电流量(200、190、180、170及165 mAs)扫描,分别为常规管电流量组和低管电流量组。测量、计算并评估各组患者动脉期和门脉期图像的皮下脂肪标准差(SD)值、肝脏和胰腺信噪比(SNR)、肝脏-竖脊肌和胰腺-竖脊肌对比噪声比(CNR)、图像主观质量评分以及射线剂量指标CT剂量指数(CTDI)、剂量长度乘积(DLP)、有效剂量(ED)。结果各组患者动脉期和门脉期图像的皮下脂肪SD值、肝脏和胰腺SNR、图像主观质量评分和射线剂量指标CTDI、DLP、ED之间差异均有统计学意义(P<0.05);各组肝脏-竖脊肌和胰腺-竖脊肌CNR之间差异无统计学意义(P>0.05)。其中165 mAs管电流量组图像SNR、射线剂量和主观质量评分均为最低,不能满足诊断需求。结论上腹部增强CT检查,通过阶段性降低管电流量使诊断医生逐渐适应低剂量图像质量,从而普及现有设备的低剂量扫描的方法是可行的。双源CT采用170 mAs的参考管电流量,既能获得满足临床诊断的合格图像,又能大大降低患者群体接受的辐射剂量。     

体质量指数结合iDose4迭代重建算法在低剂量冠状动脉CT成像中的应用

目的探讨基于受检者体质量指数（BMI）并应用前瞻性心电门控结合iDose^4迭代重建技术降低冠状动脉CT成像（CTCA）辐射剂量的可行性。方法选取120例CTCA受检者,根据不同BMI将其分为4组,A组（BMI≤21kg／m^2）、B组（21kg／m^2〈BMI≤24kg／m^2）、C组（24kg／m^2〈BMI〈28kg／m2、D组（BMI≥28kg／m^2）,每组各30例。预设A组、B组、C组、D组管电流分别为100、150、200、250mAs,应用前瞻性心电门控技术进行扫描,之后采用iDose4迭代重建算法对图像分别进行标准滤波反投影（FBP）、iDose^4-3、iDose^4-5重建。由2名放射科医师采用4分制对图像质量进行主观评估,测量图像的客观噪声。记录4组的CT剂量指数（cTDIvol）、剂量长度乘积（DLP）,并估算有效剂量（ED）。结果各组中3种重建图像的客观噪声差异有统计学意义（P〈0．001）。与FBP相比,iDose^4-3和iDose4-5的图像客观噪声分别平均降低23．11％和35．61％,且应用iDose^4-3和iDose^4-5重建算法获得的CTCA图像主观评分≥3分的比率高于FBP（P〈0．05）,但iDos4-3和iDose4-55之间的差异无统计学意义。4组受检者ED均值分别为（1．36±0．10）mSV、（1．98±0．10）mSV、（2．67±0．21）mSV和（3．33±0．24）mSV。结论应用前瞻性心电门控技术结合iDose4迭代重建技术,根据受检者BMI采用不同扫描参数,可有效减低CTCA辐射剂量。     

柔性减影CE-Boost技术对下肢动脉CT血管造影图像质量的影响

目的 观察柔性减影CE-Boost技术对下肢动脉CT血管造影(CTA)图像质量的影响。方法 对50例疑诊下肢动脉疾病患者采集双下肢动脉CTA,之后以常规混合迭代算法重建获得常规重建图像(A组),以柔性减影CE-Boost技术对其进行处理而获得CE-Boost图(B组)。对比2组图像质量主观评分,以及下肢动脉不同位置CT值、图像噪声、信噪比(SNR)及对比度噪声比(CNR)。结果 B组图像质量主观评分[4(3,4)]高于A组[3(2,3),Z=-4.880,P<0.001]。B组下肢动脉不同位置CT值、SNR及CNR均高于A组(P均<0.001),图像噪声均低于A组(P均<0.001)。结论 采用柔性减影CE-Boost技术可提高下肢动脉CTA图像质量。     

Feasibility of lung imaging with a large field-of-view spectral photon-counting CT system

PurposeThe purpose of this study was to characterize the technical capabilities and feasibility of a large field-of-view clinical spectral photon-counting computed tomography (SPCCT) prototype for high-resolution (HR) lung imaging.Materials and methodsMeasurement of modulation transfer function (MTF) and acquisition of a line pairs phantom were performed. An anthropomorphic lung nodule phantom was scanned with standard (120 kVp, 62 mAs), low (120 kVp, 11 mAs), and ultra-low (80 kVp, 3 mAs) radiation doses. A human volunteer underwent standard (120 kVp, 63 mAs) and low (120 kVp, 11 mAs) dose scans after approval by the ethics committee. HR images were reconstructed with 1024 matrix, 300 mm field of view and 0.25 mm slice thickness using a filtered-back projection (FBP) and two levels of iterative reconstruction (iDose 5 and 9). The conspicuity and sharpness of various lung structures (distal airways, vessels, fissures and proximal bronchial wall), image noise, and overall image quality were independently analyzed by three radiologists and compared to a previous HR lung CT examination of the same volunteer performed with a conventional CT equipped with energy integrating detectors (120 kVp, 10 mAs, FBP).ResultsTen percent MTF was measured at 22.3 lp/cm with a cut-off at 31 lp/cm. Up to 28 lp/cm were depicted. While mixed and solid nodules were easily depicted on standard and low-dose phantom images, higher iDose levels and slice thicknesses (1 mm) were needed to visualize ground-glass components on ultra-low-dose images. Standard dose SPCCT images of in vivo lung structures were of greater conspicuity and sharpness, with greater overall image quality, and similar image noise (despite a flux reduction of 23%) to conventional CT images. Low-dose SPCCT images were of greater or similar conspicuity and sharpness, similar overall image quality, and lower but acceptable image noise (despite a flux reduction of 89%).ConclusionsA large field-of-view SPCCT prototype demonstrates HR technical capabilities and high image quality for high resolution lung CT in human.     

多排螺旋CT非螺旋低剂量扫描筛查肺结节

目的探讨4排螺旋CT非螺旋低剂量扫描方式在肺结节诊断中的价值。方法对30例胸片可疑肺结节患者分别行螺旋低剂量和非螺旋低剂量扫描。采用Toshiba 4排多层螺旋CT（Asteion 4）扫描机。螺旋扫描采用预设35.5 mAs,床进20 mm/圈（即螺距1）,0.75 s/圈,非螺旋扫描预设24 mAs,床进20 mm/圈（层厚=层距）,0.48 s/圈,其他扫描参数相同：120 kV,准直0.5×4,DFOV 300 mm,重建层厚5mm。根据出现伪影程度及是否分辨出肺结节来评价CT图像质量,对肺结节进行简单计数。比较两者发现肺结节的差异及有效放射剂量的差异。结果两种扫描方式检查30例患者均为阳性,发现各种肺结节都是108个。非螺旋扫描的有效放射剂量低于螺旋扫描方式（P〈0.001）。结论非螺旋方式扫描与螺旋方式扫描在胸部低剂量检查中对于肺内病灶的发现及诊断无统计学差异,扫描剂量相对更低的非螺旋方式扫描应用于胸部疾病的诊断及筛查是可行的。     

Which dose for what image? Iterative reconstruction for CT scan

PurposeTo evaluate the potential of iterative reconstruction for reducing the dose given to the patient during abdominal CT scanning.Materials and methodsA double abdominal CT scan acquisition (Somatom Definition AS+ Siemens) performed without contrast administration at –30% and at –70% of the doses (mAs) was compared to the standard acquisition in 10 patients. The raw data were reconstructed by filtered back projection (FBP) and using the SAFIRE iterative reconstruction method (five levels of iteration). The signal, noise, signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) were compared for three regions of interest, including the kidney, psoas and abdominal fat.ResultsThe signal in each region of interest was not modified based on the type of reconstruction. The noise level decreased significantly during the passage from the FBP to SAFIRE, as well as with the increase in the SAFIRE level. The SNR and CNR therefore increased with the use of iterative reconstructions. The increase in noise observed between the acquisition at –30% and that at –70% was compensated by the use of higher SAFIRE levels.ConclusionIterative reconstructions can be used to improve the SNR and CNR at a constant dose or to reduce the dose by keeping the same SNR and CNR on abdominal CT images.     

CT pulmonary angiogram with 60% dose reduction: Influence of iterative reconstructions on image quality

GoalsTo compare the quality of low-dose CT images with sinogram affirmed iterative reconstruction (SAFIRE), and full-dose CT with filtered back projection reconstructions (FBP).Materials and methodsFifty pulmonary CT performed by a dual-source technique (120 kVp; 110 mAs) with (a) the same energy in both tubes, and (b) the distribution of reference mAs with 40% in tube A (44 mAs) and 60% in tube B (66 mAs). Each acquisition allowed reconstruction of: (a) full-dose images (with both tubes) with FBP reconstructions (group 1); and (b) low-dose images (from tube A) reconstructed with SAFIRE (group 2).ResultsGroup 2 images presented: (a) a significant objective reduction in noise measured in the trachea on mediastinal (16.04 ± 5.66 vs 17.66 ± 5.84) (P = 0.0284) and pulmonary (29.77 ± 6.79 vs 37.96 ± 9.03) (P < 0.0001) images; (b) a similar subjective perception of noise and overall image quality (P = 1), which was considered to be excellent in 66% (33/50) of the cases, with no influence on the detection of elementary pulmonary lesions of infiltration (98.4%; 95% CI = [96.9%–99.9%]).ConclusionDespite a 60% reduction in radiation dose, the image quality with iterative reconstruction is objectively better and subjectively similar to full-dose FBP images.     

Dose reduction with iterative reconstruction: Optimization of CT protocols in clinical practice

ObjectivesTo create an adaptable and global approach for optimizing MDCT protocols by evaluating the influence of acquisition parameters and Iterative Reconstruction (IR) on dose reduction and image quality.Materials and methodsMDCT acquisitions were performed on quality image phantom by varying kVp, mAs, and pitch for the same collimation. The raw data were reconstructed by FBP and Sinogram Affirmed Iterative Reconstruction (SAFIRE) with different reconstruction kernel and thickness. A total of 4032 combinations of parameters were obtained. Indices of quality image (image noise, NCT, CNR, SNR, NPS and MTF) were analyzed. We developed a software in order to facilitate the optimization between dose reduction and image quality. Its outcomes were verified on an adult anthropomorphic phantom.ResultsDose reduction resulted in the increase of image noise and the decrease of SNR and CNR. The use of IR improved these indices for the same dose without affecting NCT and MTF. The image validation was performed by the anthropomorphic phantom. The software proposed combinations of parameters to reduce doses while keeping indices of the image quality adequate. We observed a CTDIvol reduction between −44% and −83% as compared to the French diagnostic reference levels (DRL) for different anatomical localization.ConclusionThe software developed in this study may help radiologists in selecting adequate combinations of parameters that allows to obtain an appropriate image with dose reduction.