迭代重建算法识别儿童低剂量CT肺内坏死病灶的优势

目的评价两种迭代重建算法与传统的滤波反射投影算法(filtered back-projection,FBP)对儿童低剂量CT肺内坏死病灶识别的能力。方法选取73例儿童胸部CT(年龄2月~12岁,中位年龄4岁)增强检查,使用低剂量扫描方案,所得到的原始数据重建为基于模型的迭代重建算法(model-based iterative reconstruction,MBIR)、自适应迭代重建算法(adaptive statistical iterative reconstruction,ASIR)的0.625mm图像,与重建为0.625mm的FBP图像比较图像主观、客观质量。图像主观质量由两位医师应用1~4分制评价(2分合格,4分最好),内容包括对图像整体的质量评分及坏死病灶显示能力评分。客观质量测量坏死病变、以及周围实变的肺组织、正常肺野的噪声,并计算坏死病变与实变、肺野的对比噪声比(contrast noise ratio,CNR)。结果主观图像质量方面MBIR图像整体质量评分3.71±0.45,病灶显示能力4.00±0.00;明显优于ASIR图像及FBP图像。客观噪声方面,病变区域噪声MBIR、ASIR、FBP图像分别为14.71±3.85,25.68±6.33,35.78±8.87,与周围实变的CNR三组图像分别为4.03±0.98,2.38±0.75,1.57±0.41,与肺野的CNR分别为41.94±10.03,29.32±8.14,20.47±4.69。结论低剂量图像结合迭代重建算法可以提高儿童肺内坏死灶的识别能力,其中MBIR图像效果最好。     

不同重建算法对常规剂量CT腹部脏器图像质量的影响

目的 :探讨滤波反投影法(FBP)、自适应统计迭代重建(ASIR)与基于模型迭代重建(MBIR)3种重建算法对常规剂量CT腹部脏器图像质量的影响。方法:收集腹部扫描患者50例,行常规剂量CT腹部扫描,扫描后分别采用FBP、40%ASIR、MBIR重建0.625 mm图像,分别测量肝脏、脾脏、胰腺、双肾及同层面皮下脂肪CT值及标准差(SD)值,计算SNR、对比噪声比(CNR)和40%ASIR、MBIR的SD降低率和SNR、CNR增加率,并对图像进行双盲法主观评分。结果 :FBP、40%ASIR、MBIR 3组图像主观评分之间差异均有统计学意义(均P0.05)。MBIR图像肝脏、脾脏、胰腺、双肾实质的SD值均低于40%ASIR组和FBP组(均P0.05),MBIR图像肝脏、脾脏、胰腺、双肾SNR和CNR均较40%ASIR组和FBP组提高(均P0.05),且SD值、SNR、CNR在3组图像间差异均有统计学意义(均P0.05)。结论:与FBP重建方法相比,40%ASIR和MBIR不仅可有效降低图像噪声,还可提高图像质量,其中MBIR在降低图像噪声及提高图像质量方面效果最佳,有助于临床实现上腹部低辐射剂量CT检查。     

迭代重建技术对低剂量CT图像质量和肺磨玻璃密度结节体积测量准确性的影响

目的 应用胸部模型评价3种CT迭代重建技术对低剂量CT图像质量及肺磨玻璃密度(GGO)结节体积测量准确性的影响.方法 应用2台多层螺旋CT(HDCT和iCT)扫描含有GGO结节的胸部模型,应用30％自适应统计迭代重建算法(ASIR)、基于模型的迭代重建(MBIR)算法和iDose4 L3、L6算法进行重建,由2名放射科医师测量重建图像上ROI的CT值,计算平均噪声和对比噪声比(CNR).并应用肺结节评估软件测量GGO结节的体积,计算CT测量结节体积的绝对百分误差(APE).不同重建方法下平均噪声值及对比噪声值之间的差异应用重复测量方差分析,比较不同重建方法对结节体积测量的差异时应用Kruskal-WallisH秩和检验.结果 HDCT在有效剂量(ED)为0.36 mSv时,标准的滤波反投影(FBP)、30％ ASIR和MBIR算法重建图像的平均噪声值分别为40.38±4.49、30.06±20.17和10.55±1.56,CNR值分别为5.00±2.36、8.43±3.89和20.27±7.35,MBIR与FBP、30％ ASIR算法图像比较,图像噪声值分别下降了73.9％和64.9％,CNR值分别提高了75.3％和58.4％,差异有统计学意义(F值分别为13.053、9.459,P值均＜0.01);iCT在ED为0.64 mSv时,iDose L6与FBP算法比较,图像噪声值降低了36.5％,CNR值提高了78.4％.不同重建算法、不同NI和管电流在肺结节体积测量的APE上差异均无统计学意义(P值均＞0.05).结论 3种迭代重建算法均能够降低较低剂量图像的平均噪声,提高图像质量.     

迭代重建算法在80kV低剂量儿童脊柱CT的应用

【摘要】目的：评价基于模型的迭代重建算法（MBIR）及自适应迭代重建算法（ASIR）是否可以在80 kV低剂量儿童脊柱CT扫描中获得符合诊断标准的图像,以减少放射线对患儿的损伤。方法：连续选取36例因脊柱病变需要复查脊柱CT的患儿行80kV,50mA低剂量扫描作为观察组,将所得的原始数据分别重建为0.625mm的MBIR图像、ASIR图像、FBP图像。所有患儿治疗前的脊柱CT检查为对照组,扫描管电压120kV,余扫描参数不变,图像重建为0.625mm的FBP图像。四组图像质量主观评价由2名医师分别采用1~4分制（3分合格,4分最好）评价图像主观噪声及椎体结构显示能力;图像质量客观评价为测量L1椎体以及同层面背侧肌肉的CT值及噪声值,并计算椎体的SNR及CNR。同时并记录两次检查剂量报告表中的CT容积剂量指数(CTDIvol)、剂量长度乘积（DLP）。结果：图像的主观评分结果显示：对照组图像以及观察组的MBIR图像可以满足诊断要求;客观噪声结果：观察组MBIR、ASIR、FBP以及对照组FBP图像分别为17.35±2.70、50.89±4.24、76.68±7.11、28.49±3.25,信噪比分别为5.75±1.05、2.74±0.41、1.90±0.28、4.19±0.43;对比噪声比分别为8.14±0.91、2.74±0.38、1.892±0.33、4.46±0.86;观察组放射剂量CTDIvol、DLP分别为（0.77±0.02）mGy,（51.28±11.67）mGy·cm,较对照组分别降低65.47%,64.76%。结论：应用80kV低剂量儿童脊柱CT结合MBIR可以得到满足诊断要求的图像,达到减少患儿放射损伤的目的。     

新一代基于模型的迭代算法在胸部低剂量CT筛查中的应用

【摘要】目的：探讨新一代基于模型的迭代重建（MBIRn）中肺特异性设置（MBIR NR40和MBIR RP20）在低剂量胸部CT图像质量的临床应用价值。方法：前瞻性搜集胸部CT低剂量筛查患者30例,采用肺和标准算法ASIR40%、MBIRn中的肺特异性设置（MBIR NR40和MBIR RP20）3种算法重建图像,比较3组图像的客观质量(感兴趣区CT值、信噪比)以及MBIR NR40和MBIR RP20相对于标准算法ASIR40%的噪声降低率和SNR提高率。在肺算法ASIR40%、MBIR NR40和MBIR RP20评价肺内结构,在标准算法ASIR40%、MBIR NR40和MBIR RP20评价纵隔结构,由两名放射科医师采用双盲法阅片对图像质量进行主观评价。结果：与标准算法ASIR40%相比,MBIR NR40和MBIR RP20两种算法的图像肌肉噪声分别较ASIR40%降低80.78%、37.27%,脂肪噪声分别较ASIR40%降低69.27%、23.69%,差异具有统计学意义（P＜0.05）。MBIR NR40和MBIR RP20两种算法图像肌肉SNR分别较ASIR40%组提高81.80%、37.64%,脂肪SNR分别较ASIR40%组提高72.98%、24.95%,差异具有统计学意义（P＜0.05）。三种算法图像在主观噪声、肺内血管及支气管清晰度、纵隔内血管及淋巴结中评分均有统计学差异,其中MBIR NR40主观噪声最低,纵隔内结构显示最清晰,MBIR RP20肺内血管及支气管显示最清晰。结论：在低剂量胸部CT条件下,与ASIR40%相比,MBIR组能明显提高图像质量,其中MBIR RP20显示肺部结构最优。MBIR NR40可明显降低图像噪声,提高纵隔内结构显示清晰度。     

ASIR技术对MSCT增强门脉成像质量的影响

【摘要】目的：探讨自适应统计迭代重建（ASIR）技术对成人肝脏CT增强扫描的门静脉成像质量的影响。方法：2015年3月-2015年12月的68例受试者在64排128层螺旋CT上行肝脏CT增强检查。图像重建分别采用FBP和100%ASIR两种方法。由2名高年资影像诊断医师采用双盲法分别对FBP和ASIR重建出的肝脏门静脉期VR图像进行主观评价。分别手工记录肝实质、门静脉的CT值。计算门静脉对比噪声比（CNR）。对于图像质量的主观分析采用非参数Wilcoxon符号秩和检验方法,对于分析所需时间及CNR的比较采用配对t检验方法。结果：对肝脏增强CT门静脉期VR图像的主观评分,FBP为1.81±0.64,ASIR为2.50±0.83（P<0.05）。两种方法的门静脉CT值及肝实质CT值间差异没有统计学意义（P>0.05）。两种方法背景噪声间差异具有统计学意义（FBP为18.4±2.5,ASIR为6.9±2.3,P<0.05）。ASIR重建的图像的CNR高于FBP重建的图像（分别为5.56±1.91、1.99±0.51）（P<0.05）。结论：ASIR技术可以有效提高肝脏增强CT检查门静脉成像的CNR及图像质量。     

迭代重建在前列腺CT成像中的应用研究

目的:探讨迭代重建在前列腺CT检查中的临床应用价值。方法:接受腹部CT增强扫描的男性患者4例入组,对增强图像进行滤波反投影重建(FBP)、30%、50%、80%及100%自适应统计迭代重建(ASIR)和基于模型的迭代重建(MBIR),对这6种图像的噪声、图像质量、前列腺对比噪声比(CNR),使用方差分析进行统计学分析。结果:MBIR图像的噪声最低,主观评分最高,且前列腺外周带的CNR最高,与其它图像相比差异有统计学意义(P<0.05)。结论:MBIR有提高前列腺图像质量、进一步显示更多解剖细节的潜在价值。     

应用高级迭低重建改善低剂量冠状动脉CT血管成像图像质量的研究

目的评价不同强度高级迭低重建(advanced modeled iterative reconstruction,ADMIRE)改善低剂量冠状动脉CT血管成像(coronary CT angiography,CCTA)图像质量的效果,筛选最适迭代重建强度。方法对39例疑似冠状动脉粥样硬化患者应用西门子FORCECT行低剂量CCTA,同时采用滤过反投影法(filtered back projection,FBP)和高级迭低重建算法(advanced modeled iterative reconstruction,ADMIRE)(强度1~5)进行图像重建,评价客观及主观图像质量。客观图像质量指标包括平均CT值、图像噪声、信噪比(SNR)、对比度噪声比(CNR),主观图像质量评价由两名具有10年以上诊断经验的影像医师对冠状动脉15段分支血管进行双盲评分。结果不同强度ADMIRE及FBP组间比较,感兴趣区的CT值无统计学差异,不同迭代强度各组图像噪声均显著低于FBP组,噪声水平随迭代强度的增高而降低(P0.05)。迭代重建各组的SNR、CNR均显著高于FBP组,SNR与CNR均随迭代强度的增高而增高(P0.05)。ADMIRE 4组主观图像质量评分及可判读性最高(P0.05),其他组评分从高到低依次为ADMIRE 5,3,2,1及FBP。结论:在相同辐射剂量条件下,CCTA成像运用ADMIRE较FBP可明显提高主观及客观图像质量;本实验条件下CCTA扫描推荐的ADMIRE强度为4。(modeled iterative reconstruction,ADMIRE)(强度1~5)进行图像重建,评价客观及主观图像质量。客观图像质量指标包括平均CT值、图像噪声、信噪比(SNR)、对比度噪声比(CNR),主观图像质量评价由两名具有10年以上诊断经验的影像医师对冠状动脉15段分支血管进行双盲评分。结果:不同强度ADMIRE及FBP组间比较,感兴趣区的CT值无统计学差异,不同迭代强度各组图像噪声均显著低于FBP组,噪声水平随迭代强度的增高而降低(P0.05)。迭代重建各组的SNR、CNR均显著高于FBP组,SNR与CNR均随迭代强度的增高而增高(P0.05)。ADMIRE 4组主观图像质量评分及可判读性最高(P0.05),其他组评分从高到低依次为ADMIRE 5,3,2,1及FBP。结论在相同辐射剂量条件下,CCTA成像运用ADMIRE较FBP可明显提高主观及客观图像质量;本实验条件下CCTA扫描推荐的ADMIRE强度为4。     

迭代算法在100kVp分次团注双期CTU检查中的应用研究

目的:探讨不同比例自适应统计迭代重建(ASIR)、基于模型的迭代重建(MBIR)在100kVp分次团注双期CTU检查中的应用价值。方法:30例血尿待查患者分为两组,100kVp组15例,行全泌尿系平扫及分两次团注对比剂后行肾实质-肾盂期CT扫描;120kVp组15例,行全泌尿系CT平扫及单次团注对比剂后行实质期和肾盂期双期增强扫描。100kVp组的肾实质-肾盂期图像在100kVp条件下采集,其他所有期相的图像均在120kVp条件下采集。重建图像包括:100kVp组肾实质-肾盂期FBP、50%ASIR、100%ASIR、MBIR四组图像;120kVp组肾盂期FBP图像。两名阅片者对100kVp组和120kVp组CTU重建图像进行独立阅片,对图像质量进行主观评分,测量图像背景噪声、集合系统各段CT值,计算对比噪声比(CNR)。记录所有病例有效剂量(ED)和体型特异性剂量评估值(SSDE),并进行统计学分析。结果:100kVp组MBIR、50%ASIR与120kVp组图像质量主观评分差异无统计学意义(P>0.05),100kVp组FBP、100%ASIR图像质量评分低于120kVp组(P<0.05);100kVp组MBIR、100%ASIR图像噪声低于120kVp组(P<0.05),100kVp组50%ASIR与120kVp组图像噪声差异无统计学意义(P>0.05),100kVp组FBP图像噪声高于120kVp组(P<0.05);100kVp组MBIR图像各段尿路CNR高于120kVp组(P<0.05),100kVp组50%ASIR、100%ASIR与120kVp组图像各段尿路CNR差异无统计学意义(P>0.05),100kVp组FBP图像各段尿路CNR低于120kVp组(P<0.05)。100kVp组ED及SSDE均低于120kVp组(P<0.05)。结论:ASIR及MBIR技术可提高图像质量、增加图像对比,使常规剂量对比剂100kVp分次团注双期CTU达到或超过常规管电压单次团注三期CTU成像效果,从而明显降低X线辐射剂量。     

应用MBIR优化100kV儿童胸部CTA血管的显示质量

目的评价基于模型的迭代重建算法(model-based iterative reconstruction,MBIR)对100kV儿童低剂量胸部CT血管的优化效果。方法选取接受胸部低剂量胸部增强CT扫描的儿童患者66例,使用100 kV管电压扫描,所得到的原始数据重建为0.625 mm的MBIR图像(观察组),0.625 mm的50%ASIR图像(对照组),应用4分制评价图像整体的质量、胸部大血管(体动脉、肺动脉、肺静脉)的显示能力,以及细小血管的显示能力。客观噪声测量降主动脉、肺动脉干、左心房、竖脊肌的噪声值,并计算优化信噪比及降主动脉、肺动脉干、左心房的对比噪声比。结果MBIR组对于整体图像质量、胸部大血管及小血管主观图像质量评分(2.93±0.46,3.01±0.55,2.32±0.47)明显优于ASIR组(1.76±0.43,2.27±0.43,1.46±0.50);客观噪声方面MBIR图像降主动脉、肺动脉干、左心房的客观噪声值为14.92±3.83,13.68±2.28,15.74±4.04,较ASIR图像降低了38.47%~44.12%,相应的SNR分别增高了59.71%~81.83%;CNR增高73.53%~76.59%。结论MBIR应用于儿童100 kV的胸部血管可以同时提高肺动脉及体动脉的显示能力,特别是小血管的显示能力,明显优于ASIR图像,保证了图像整体质量。     

Coronary artery plaques: cardiac CT with model-based and adaptive-statistical iterative reconstruction technique

Objectives

To compare image quality of coronary artery plaque visualization at CT angiography with images reconstructed with filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), and model based iterative reconstruction (MBIR) techniques.

Methods

The coronary arteries of three ex vivo human hearts were imaged by CT and reconstructed with FBP, ASIR and MBIR. Coronary cross-sectional images were co-registered between the different reconstruction techniques and assessed for qualitative and quantitative image quality parameters. Readers were blinded to the reconstruction algorithm.

Results

A total of 375 triplets of coronary cross-sectional images were co-registered. Using MBIR, 26% of the images were rated as having excellent overall image quality, which was significantly better as compared to ASIR and FBP (4% and 13%, respectively, all p < 0.001). Qualitative assessment of image noise demonstrated a noise reduction by using ASIR as compared to FBP (p < 0.01) and further noise reduction by using MBIR (p < 0.001). The contrast-to-noise-ratio (CNR) using MBIR was better as compared to ASIR and FBP (44 ± 19, 29 ± 15, 26 ± 9, respectively; all p < 0.001).

Conclusions

Using MBIR improved image quality, reduced image noise and increased CNR as compared to the other available reconstruction techniques. This may further improve the visualization of coronary artery plaque and allow radiation reduction.     

Comparison of the image qualities of filtered back-projection,adaptive statistical iterative reconstruction,and model-based iterative reconstruction for CT venography at 80 kVp

Purpose

To evaluate the subjective and objective qualities of computed tomography (CT) venography images at 80 kVp using model-based iterative reconstruction (MBIR) and to compare these with those of filtered back projection (FBP) and adaptive statistical iterative reconstruction (ASIR) using the same CT data sets.

Materials and methods

Forty-four patients (mean age: 56.1?±?18.1) who underwent 80 kVp CT venography (CTV) for the evaluation of deep vein thrombosis (DVT) during 4 months were enrolled in this retrospective study. The same raw data were reconstructed using FBP, ASIR, and MBIR. Objective and subjective image analysis were performed at the inferior vena cava (IVC), femoral vein, and popliteal vein.

Results

The mean CNR of MBIR was significantly greater than those of FBP and ASIR and images reconstructed using MBIR had significantly lower objective image noise (p?<?.001). Subjective image quality and confidence of detecting DVT by MBIR group were significantly greater than those of FBP and ASIR (p?<?.005), and MBIR had the lowest score for subjective image noise (p?<?.001).

Conclusion

CTV at 80 kVp with MBIR was superior to FBP and ASIR regarding subjective and objective image qualities.

Key Points

? MBIR provides superior image quality compared with FBP and ASIR ? CTV at 80kVp with MBIR improves diagnostic confidence in diagnosing DVT ? CTV at 80kVp with MBIR presents better image quality with low radiation

     

A phantom study of the performance of model-based iterative reconstruction in low-dose chest and abdominal CT: When are benefits maximized?

IntroductionThe aim of this study was to assess and compare the effects of CT image reconstruction techniques on low-dose CT image quality using phantoms.MethodsAnthropomorphic torso and spatial/contrast-resolution phantoms were scanned at decreasing tube currents between 400 and 10 mA. CT thorax and abdomen/pelvis series were reconstructed with filtered back projection (FBP) alone, combined 40% adaptive statistical iterative reconstruction & FBP (ASIR40), and model-based iterative reconstruction (MBIR) [(resolution-preference 05 (RP05) and RP20 in the thorax and RP05 and noise-reduction 05 (NR05) in the abdomen)]. Two readers rated image quality quantitatively and qualitatively.ResultsIn thoracic CT, objective image noise on MBIR RP05 data sets outperformed FBP at 200, 100, 50 and 10 mA and outperformed ASIR40 at 50 and 10 mA (p < 0.001). MBIR RP20 outperformed FBP at 50 and 10 mA and outperformed ASIR40 at 10 mA (p < 0.001). Compared with both FBP and ASIR40, MBIR RP05 demonstrated significantly better signal-to-noise ratio (SNR) at 10 mA. In abdomino-pelvic CT, MBIR RP05 and NR05 outperformed FBP and ASIR at all tube current levels for objective image noise. NR05 demonstrated greater SNR at 200, 100, 50 and 10 mA and RP05 demonstrated greater SNR at 50 and 10 mA compared with both FBP and ASIR. MBIR images demonstrated better subjective image quality scores. Spatial resolution, low-contrast detectability and contrast-to-noise ratio (CNR) were comparable between image reconstruction techniques.ConclusionCTs reconstructed with MBIR have lower image noise and improved image quality compared with FBP and ASIR. These effects increase with reduced radiation exposure confirming optimal use for low-dose CT imaging.     

自适应迭代重建技术对儿童低剂量胸部CT图像质量的优化

目的比较应用自适应迭代重建技术（adaptive statistical iterative reconstruction,ASIR）儿童低剂量胸部CT与传统的滤过反向投影（filteredbackprojection,FBP）的图像质量、噪声和放射剂量。方法回顾性分析80例应用自动管电流调节技术（ATCM）扫描的胸部CT检查作为试验组,年龄29天～16岁（中位年龄3．3岁）,检查时根据年龄分为4组,o～12月预设噪声指数11HU,1～3岁预设噪声指数13HU,4～6岁预设噪声指数15Hu,7～17岁预设噪声指数17HU,将所有图像经ASIR30％重建;对照组选取同时期80例经ATCM扫描的儿童胸部CT检查,1～7岁预设噪声指数8HU,7～17岁预设噪声指数12HU,未经ASIR技术重建图像。测量所有病例左心室及同层面图像的背部肌肉客观噪声值,由两位医师分别用5分制主观评价图像质量和噪声程度,并用kappa检验评价观察者间的一致性。同时记录CT剂量指数（CTDIv01）及剂量长度乘积（DLP）。结果试验组客观噪声平均值为10．49±1．65,对照组客观噪声9．16±1．52,无统计学差异,同时,试验组和对照组的主观图像质量接受率为3．90和3．98,所有图像合乎诊断要求,观察者间的评估具有一致性（k=0．64）;试验组和对照组间的CTDIv01分别为（1.19±0．78）mGy和（2．62±0．93）mGy,试验组CT-DIvol比对照组降低了54．6％,两者间差异明显（Pd0．001）。结论应用ASIR技术可获得稳定图像质量,满足诊断的前提下,可以能进一步有效减低射线剂量。     

Effects of pure and hybrid iterative reconstruction algorithms on high-resolution computed tomography in the evaluation of interstitial lung disease

ObjectivesTo compare image quality characteristics of high-resolution computed tomography (HRCT) in the evaluation of interstitial lung disease using three different reconstruction methods: model-based iterative reconstruction (MBIR), adaptive statistical iterative reconstruction (ASIR), and filtered back projection (FBP).MethodsEighty-nine consecutive patients with interstitial lung disease underwent standard-of-care chest CT with 64-row multi-detector CT. HRCT images were reconstructed in 0.625-mm contiguous axial slices using FBP, ASIR, and MBIR. Two radiologists independently assessed the images in a blinded manner for subjective image noise, streak artifacts, and visualization of normal and pathologic structures. Objective image noise was measured in the lung parenchyma. Spatial resolution was assessed by measuring the modulation transfer function (MTF).ResultsMBIR offered significantly lower objective image noise (22.24 ± 4.53, P < 0.01 among all pairs, Student's t-test) compared with ASIR (39.76 ± 7.41) and FBP (51.91 ± 9.71). MTF (spatial resolution) was increased using MBIR compared with ASIR and FBP. MBIR showed improvements in visualization of normal and pathologic structures over ASIR and FBP, while ASIR was rated quite similarly to FBP. MBIR significantly improved subjective image noise (P < 0.01 among all pairs, the sign test), and streak artifacts (P < 0.01 each for MBIR vs. the other 2 image data sets).ConclusionMBIR provides high-quality HRCT images for interstitial lung disease by reducing image noise and streak artifacts and improving spatial resolution compared with ASIR and FBP.     

Application of a full model-based iterative reconstruction (MBIR) in 80 kVp ultra-low-dose paranasal sinus CT imaging of pediatric patients

Objective

To evaluate the clinical application of a full model-based iterative reconstruction (MBIR) algorithm in the ultra-low-dose paranasal sinus CT imaging of children.

Materials and methods

In the first phase, 16 low-dose CT dacryocystography (DCG) (80 kV/64 mAs) scans were reconstructed with MBIR and filtered back-projection (FBP) to demonstrate noise reduction capability of MBIR. MBIR images were also compared with the images of 21 standard-dose paranasal sinus patients reconstructed with adaptive statistical iterative reconstruction (ASIR) algorithm. In the second phase, 14 pediatric tumors patients (images with ASIR in the initial scan) who came for follow-up paranasal sinus CT scan were prospectively enrolled with reduced radiation and MBIR algorithm. In both study phases, image noise and the contrast noise ratio (CNR) of sphenoid was measured; and subjective image quality was evaluated. CTDIvol and DLP were recorded, and effective dose calculated.

Results

The CTDIvol value for the DCG group was 63.9% lower than the standard-dose sinus group (1.09 ± 0.01 mGy vs. 3.02 ± 0.35 mGy). Compared with the ASIR reconstruction in the standard-dose sinus patient group, images with MBIR in the ultra-low-dose DCG group had 39.9% lower noise (9.5 ± 0.8HU vs. 15.8 ± 3.3HU) and 63.6% higher CNR (14.4 ± 4.7 vs. 8.8 ± 2.2), with similar subjective image quality score. For the tumor patients, 65.5% dose reduction was achieved. Subjective quality scores were similar between the initial and follow-up scans. Objective noise was significantly lower for the follow-up group.

Conclusion

MBIR provided equal or better image quality with significantly reduced radiation dose in paranasal sinus CT imaging of pediatric patients compared with standard-dose CT with ASIR algorithm.

     

Comparison of pure and hybrid iterative reconstruction techniques with conventional filtered back projection: Image quality assessment in the cervicothoracic region

Objectives

To evaluate the impact on image quality of three different image reconstruction techniques in the cervicothoracic region: model-based iterative reconstruction (MBIR), adaptive statistical iterative reconstruction (ASIR), and filtered back projection (FBP).

Methods

Forty-four patients underwent unenhanced standard-of-care clinical computed tomography (CT) examinations which included the cervicothoracic region with a 64-row multidetector CT scanner. Images were reconstructed with FBP, 50% ASIR-FBP blending (ASIR50), and MBIR. Two radiologists assessed the cervicothoracic region in a blinded manner for streak artifacts, pixilated blotchy appearances, critical reproduction of visually sharp anatomical structures (thyroid gland, common carotid artery, and esophagus), and overall diagnostic acceptability. Objective image noise was measured in the internal jugular vein. Data were analyzed using the sign test and pair-wise Student's t-test.

Results

MBIR images had significant lower quantitative image noise (8.88 ± 1.32) compared to ASIR images (18.63 ± 4.19, P < 0.01) and FBP images (26.52 ± 5.8, P < 0.01). Significant improvements in streak artifacts of the cervicothoracic region were observed with the use of MBIR (P < 0.001 each for MBIR vs. the other two image data sets for both readers), while no significant difference was observed between ASIR and FBP (P > 0.9 for ASIR vs. FBP for both readers). MBIR images were all diagnostically acceptable. Unique features of MBIR images included pixilated blotchy appearances, which did not adversely affect diagnostic acceptability.

Conclusions

MBIR significantly improves image noise and streak artifacts of the cervicothoracic region over ASIR and FBP. MBIR is expected to enhance the value of CT examinations for areas where image noise and streak artifacts are problematic.     

Evaluation of dose reduction and image quality in chest CT using adaptive statistical iterative reconstruction with the same group of patients

Objectives The objective of this study was to compare the image quality and radiation dose of chest CT images reconstructed with a blend of adaptive statistical iterative reconstruction (ASIR) and filtered back-projection (FBP) with images generated using conventional FBP. Methods Patients with chest CT re-examinations were alternately assigned to two scanners with different reconstruction techniques. The study groups included noise index (NI) 11 with 30% ASIR (A30), NI 13 with 40% ASIR (A40), NI 15 with 50% ASIR (A50) and NI 17 with 60% ASIR (A60), sequentially changed every 2 months. The control images were obtained using FBP and NI 11. All acquisitions were performed with automatic dose modulation. Paired t-test and non-parameter test were applied to compare the difference. Results The radiation doses were significantly lower in the examinations that used ASIR (p<0.001). The mean dose reduction rate was 27.7%, 45.2%, 57.1% and 71.8% for Groups A30, A40, A50 and A60, respectively. The image quality of Groups A30-A50 was not inferior to that of the control examinations. The image noise of Group A60 was greater and subjective image quality was inferior to that of the control. Conclusions ASIR enabled the use of a higher NI with automatic dose modulation. With 50% ASIR and a NI of 15, the effective radiation dose was reduced by 57%, without compromising image quality.     

CARE kV和SAFIRE在胸部占位增强CT检查中的应用

目的 验证管电压调节技术（CARE kV）和基于原始数据的迭代重建技术（sinoqram affivmd iterativere construction,SAFIRE）联合应用在胸部占位病变中能提高图像质量,同时减低受检者的辐射剂量.方法 90例肺部占位患者用Siemens SOMATOM Flash CT机行胸部CT增强扫描,分三组,组1：常规扫描条件,数据经传统的滤过反投影法（filtered back projetion,FBP）重建获取所需图像;组2、3 CARE kV启用的扫描条件,参考管电流分别设为90mAs、80mAs,数据经SAFIRE重建获取所需图像;图像质量由两位独立的放射科医师采用双盲法进行评估5分法（其级由5分到1分,分别代表图像质量极好到无法满足诊断）,密度及噪声由另一医师测量,计算图像的信噪比（SNR,signal to noise ratio）、对比噪声比（CNR,contrast to noise ratio）记录每例患者的基础信息.结果 所有图像均满足诊断要求.组2、3平均容积剂量指数（CTDIvol）、有效放射剂量（effective dose,ED）均低于组1,CNR较组1高;组3放射剂量低于组2,CNR略低于组2.结论 在胸部占位疾病中联合应用CARE kV和SAFIRE可满足诊断要求,减低受检者受照剂量,提高CT图像质量.