Comparison of image quality, diagnostic accuracy, and LV parameters in filtered backprojection versus iterative SPECT Reconstruction in Myocardial Perfusion Scintigraphy

Background@#Myocardial perfusion scintigraphy images with iterative reconstruction showed higher qualitative and quantitative estimates. @*Objective@#This study was conducted to compare image quality, diagnostic accuracy, and LV parameters with standard FBP versus OSEM as baseline quality assurance for the choice of reconstruction algorithm most applicable in the local setting. @*Methods@#This was a retrospective cross-sectional study of 55 Thallium-201 (Tl-201) scans and 14 Techentium-99m sestamibi (Tc-99m) images that were reprocessed with filtered backprojection (FBP) and with ordered subset expectation maximization (OSEM). The image quality, diagnostic accuracy, and LV parameters of both SPECT reconstructions were compared.@*Results@#OSEM reconstruction resulted in a significantly smooth background tracer activity as opposed to the standard FBP in both Tl-201 (p<0.01) and Tc-99m (p=0.01) scans. Distinct LV border was superiorly seen in OSEM. There was no significant difference in the diagnostic accuracy between the two reconstruction parameters despite 2 cases of interpretation discrepancies. End-diastolic volume generated by OSEM was significantly higher (117.60+55.14 vs 118.51+55.11, p<0.01 in Tl-201 and 101.07+75.58 vs 104.29+80.39, p =0.01 in Tc-99m). With Tc-99m scans the end-systolic volume and ejection fraction in OSEM were likewise significantly different from FBP (p=0.04 and p<0.01, respectively).@*Conclusion@#OSEM reconstruction offers smooth background tracer activity with comparable diagnostic accuracy to FBP. All the LV parameters in OSEM were significantly different from FBP in Tc-99m scans and only the EDV in thallium images.

Free trajectory cone beam computed tomography reconstruction method for synchronous scanning of geometric calibration phantom and imaging object / 生物医学工程学杂志

In order to suppress the geometrical artifacts caused by random jitter in ray source scanning, and to achieve flexible ray source scanning trajectory and meet the requirements of task-driven scanning imaging, a method of free trajectory cone-beam computed tomography (CBCT) reconstruction is proposed in this paper. This method proposed a geometric calibration method of two-dimensional plane. Based on this method, the geometric calibration phantom and the imaging object could be simultaneously imaged. Then, the geometric parameters could be obtained by online calibration method, and then combined with the geometric parameters, the alternating direction multiplier method (ADMM) was used for image iterative reconstruction. Experimental results showed that this method obtained high quality reconstruction image with high contrast and clear feature edge. The root mean square errors (RMSE) of the simulation results were rather small, and the structural similarity (SSIM) values were all above 0.99. The experimental results showed that it had lower image information entropy (IE) and higher contrast noise ratio (CNR). This method provides some practical value for CBCT to realize trajectory freedom and obtain high quality reconstructed image.

Ultra-low-dose chest computed tomography without anesthesia in the assessment of pediatric pulmonary diseases / Tomografia computadorizada de tórax de ultrabaixa dosagem sem anestesia naavaliação de doenças pulmonares pediátricas

Abstract Objective To evaluate the feasibility of using ultra-low-dose computed tomography of the chest with iterative reconstruction without anesthesia for assessment of pulmonary diseases in children. Methods This prospective study enrolled 86 consecutive pediatric patients (ranging from 1 month to 18 years) that underwent ultra-low-dose computed tomography due to suspicion of pulmonary diseases, without anesthesia and contrast. Parameters used were: 80 kVp; 15-30 mA; acquisition time, 0.5 s; and pitch, 1.375. The adaptive statistical iterative reconstruction technique was used. Subjective visual evaluation and quantitative assessment of image quality were done using a 5-point scale in 12 different structures of the chest. Results Mean age was 66 months (interquartile range, 16-147). Final diagnosis was performed in all exams, and 44 (51.2%) were diagnosed with cystic fibrosis, 27 (31.4%) with bronchiolitis obliterans, and 15 (17.4%) with congenital pulmonary airways malformations. Diagnostic quality was achieved in 98.9%, of which 82.6% were considered excellent and 16.3% were slightly blurred but did not interfere with image evaluation. Only one case (1.2%) presented moderate blurring that slightly compromised the image, and previous examinations demonstrated findings compatible with bronchiolitis obliterans. Mean effective radiation dose was 0.39 ± 0.15 mSv. Percentages of images with motion artifacts were 0.3% for cystic fibrosis, 1.3% for bronchiolitis obliterans, and 1.1% for congenital pulmonary airways malformations. Conclusion Chest ultra-low-dose computed tomography without sedation or anesthesia delivering a sub-millisievert dose can provide image quality to allow identification of common pulmonary anatomy and diseases.

Resumo Objetivo Avaliar a viabilidade do uso de tomografia computadorizada com ultrabaixa dose com reconstrução iterativa sem anestesia para avaliação de doenças pulmonares em crianças. Métodos Este estudo prospectivo envolveu 86 pacientes pediátricos consecutivos (um mês a 18 anos) submetidos à tomografia computadorizada com ultrabaixa dose por suspeita de doenças pulmonares, sem anestesia e contraste. Os parâmetros utilizados foram: 80 kVp; 15-30 mA; tempo de aquisição, 0,5 s; e pitch de 1,375. Foi utilizada a técnica de reconstrução estatística adaptativa iterativa. A avaliação visual subjetiva e a avaliação quantitativa da qualidade da imagem foram feitas com uma escala de 5 pontos em 12 estruturas do tórax. Resultados A média de idade foi de 66 meses (intervalo interquartil, 16-147). O diagnóstico final foi feito em todos os exames e 44 (51,2%) foram diagnosticados com fibrose cística, 27 (31,4%) com bronquiolite obliterante e 15 (17,4%) com malformação congênita pulmonar das vias aéreas. A qualidade diagnóstica foi alcançada em 98,9% dos casos, dos quais 82,6% foram considerados excelentes e 16,3% alteração leve na definição, mas isso não interferiu na avaliação da imagem. Apenas um caso (1,2%) apresentou alteração moderada na definição, comprometeu discretamente a imagem, e exames prévios demonstraram achados compatíveis com bronquiolite obliterante. A dose de radiação média efetiva foi de 0,39 ± 0,15 mSv. As porcentagens de imagens com artefatos de movimento foram de 0,3% para fibrose cística, 1,3% para bronquiolite obliterante e 1,1% para malformação congênita pulmonar das vias aéreas. Conclusão É possível realizar a tomografia computadorizada com ultrabaixa dose torácica sem sedação ou anestesia, administrando uma dose de submilisievert, com qualidade de imagem suficiente para a identificação pulmonar anatômica e de doenças pulmonares comuns.

Low-Dose Abdominal CT Using a Deep Learning-Based Denoising Algorithm: A Comparison with CT Reconstructed with Filtered Back Projection or Iterative Reconstruction Algorithm

OBJECTIVE: To compare the image quality of low-dose (LD) computed tomography (CT) obtained using a deep learning-based denoising algorithm (DLA) with LD CT images reconstructed with a filtered back projection (FBP) and advanced modeled iterative reconstruction (ADMIRE).MATERIALS AND METHODS: One hundred routine-dose (RD) abdominal CT studies reconstructed using FBP were used to train the DLA. Simulated CT images were made at dose levels of 13%, 25%, and 50% of the RD (DLA-1, -2, and -3) and reconstructed using FBP. We trained DLAs using the simulated CT images as input data and the RD CT images as ground truth. To test the DLA, the American College of Radiology CT phantom was used together with 18 patients who underwent abdominal LD CT. LD CT images of the phantom and patients were processed using FBP, ADMIRE, and DLAs (LD-FBP, LD-ADMIRE, and LD-DLA images, respectively). To compare the image quality, we measured the noise power spectrum and modulation transfer function (MTF) of phantom images. For patient data, we measured the mean image noise and performed qualitative image analysis. We evaluated the presence of additional artifacts in the LD-DLA images.RESULTS: LD-DLAs achieved lower noise levels than LD-FBP and LD-ADMIRE for both phantom and patient data (all p < 0.001). LD-DLAs trained with a lower radiation dose showed less image noise. However, the MTFs of the LD-DLAs were lower than those of LD-ADMIRE and LD-FBP (all p < 0.001) and decreased with decreasing training image dose. In the qualitative image analysis, the overall image quality of LD-DLAs was best for DLA-3 (50% simulated radiation dose) and not significantly different from LD-ADMIRE. There were no additional artifacts in LD-DLA images.CONCLUSION: DLAs achieved less noise than FBP and ADMIRE in LD CT images, but did not maintain spatial resolution. The DLA trained with 50% simulated radiation dose showed the best overall image quality.

Utilization of sinogram affirmed iterative reconstruction on 128 multi slice computed tomography scan to reduce radiation dose and improve image quality on thorax multi slice computed tomography scan: chest phantom study

Background: Thorax MSCT examination is a diagnostic imaging that is capable of displaying both normal and pathological lung and respiratory organs. MSCT examination also has a better level of sensitivity and specificity compared to other modalities, but the radiation exposure given is very high, so the radiation dose given to patients is high. The reduction in radiation dose is very important because of the direct exposure to sensitive tissue. One method of reducing radiation dose is by reducing the tube voltage. However, the decrease in tube voltage causes a decrease in image quality as indicated by increased noise and decreased CNR. To maintain the quality of the image at low tube voltage setting, an IR reconstruction of SAFIRE was used. The purpose of this research is to know the impact of using SAFIRE on dose radiation and image quality of thorax MSCT.Methods: This study was an experimental study with a quasi-experimental study design. The object used was the N-1 Lungman chest phantom in which an artificial tumor was attached. Radiation dose assessment used CTDI value, while image quality assessment used noise and CNR. Data processing was conducted using linear regression test.Results: There was an effect of tube voltage setting and SAFIRE setting on radiation dose and image quality.Conclusions: Tube voltage ssetting and SAFIRE setting had an effect on radiation dose and image quality. Tube voltage setting and SAFIRE strength level setting that were able to provide optimal radiation dose and image quality were tube voltage of 80 kVp and SAFIRE strength levels 3 and 4 (S3 and S4).

Virtual monochromatic images in low tube current dual-energy spectral imaging combined with adaptive statistical iterative reconstruction V in head CT angiography:phantom and clinical study / 中华放射学杂志

Objective@#To analyze the value of combining the virtual monochromatic spectral (VMS) image and adaptive statistical iterative reconstruction V (ASiR-V) in low tube current dual-energy spectral imaging in head CTA, and to explore the optimal VMS and ASiR-V level while reducing the radiation dose.@*Method@#(1) Phantom study: an Anthropomorphic PBU-60 angiographic head phantom was examined on a Revolution CT with spectral imaging mode at two different tube current. Images of different energy levels (at 40, 45, 50, 55, 60, 65 and 70 keV) in A group [the low tube current group (with 280 mA)] were reconstructed with the combination of filtered back projection (FBP), 20%, 40%, 60% and 80% ASiR-V. VMS images at 70 keV in B group [the routine tube current group (with 445 mA)] were reconstructed with FBP only. The standard deviation (SD), signal to noise ratio (SNR) and contrast to noise ratio (CNR) of phantom study were measured and examined by ANOVA variance analysis.(2) Clinical study: to prospectively select 40 patients (randomly divided into A and B groups with 20 patients in each group), the subjective scores of patients were assessed with a 5-point scale system and compared by the Mann-Whitney U test. The radiation dose was recorded and analyzed by t test.@*Results@#(1) Phantom study: there were significant differences in the image noise, CNR of the simulated cerebral vessels at different energy levels of VMS image (P<0.05). VMS images at 40 to 55 keV yielded a higher CNR compared with 70 keV (P<0.05). The SNR and CNR in the low tube current group with ASiR-V 60% and ASiR-V 80% were higher than that of the FBP, ASiR-V 20% and ASiR-V 40% images in the same group (P<0.05). (2) Clinical study: the subjective scores at 55 keV and 60 keV were higher than others (P<0.05). The subject scores of 40,50 and 55 keV were increased as the proportion of ASiR-V increased. (3) The SNR and CNR of the simulated cerebral vessels and subjective scores in of the 55 keV VMS images with ASiR-V 60% and ASiR-V 80% in the low tube current patient group was higher than that of the 70 keV FBP images in the routine tube current group (P<0.05). The radiation dose of A group was lower than B group (t=23.974, P<0.05).@*Conclusions@#VMS images in low tube current spectral imaging combined with ASiR-V can significantly reduce radiation dose and ensure image quality in head CTA. The 55 keV VMS images with ASiR-V60% and 80% provide higher image quality.

The application of adaptive statistical iterative reconstruction Veo in detection of pulmonary nodule by ultralow dose chest CT / 实用放射学杂志

Objective To explore the best percentage of adaptive statistical iterative reconstruction Veo (ASiR-V)in detection of pulmonary nodule by chest ultralow dose CT (ULDCT).Methods 81 patients with pulmonary nodule detected by chest low dose CT (LDCT)underwent a local ULDCT scan at the center of the nodule with a range of 3 cm scan length.LDCT was performed with the mode of the Assist kV (120/100 kV)/Smart mA with noise indices of 14.1 HU and reconstructed with ASiR-V 50% algorithm.ULDCT was acquired at a tube potential of 120 kV and tube current-time product of 2.8 mAs and reconstructed with ASiR-V 50%,70% and 90%algorithms.Subjective and obj ective image qualities,sensitivities of detection and diameter of nodule among all ULDCT images were compared.Results Compared with the radiation dose of LDCT [(0.9 9±0.3 6)mSv],a 90.2% decrease was seen with the ULDCT, for which the calculated mean effective radiation dose was (0.097±0.007)mSv.The noise values of fat and paravertebral muscle for ULDCT reconstructed with ASiR-V 90% were 12.33±1.86 and 14.82±2.6,which were significantly lower than those in the group of ASiR-V 50% (1 9.73±1.98, 21.19±2.46)and the group of ASiR-V 70% (15.79±1.82,17.71±2.50)(P＜0.05).The subjective scores of images reconstructed with ASiR-V 70% (4.13±0.47)were the highest,which were slightly higher than those in 90%groups (4.03±0.38)(P＜0.05).No significant differences for overall sensitivity of nodule detection were observed among the ULDCT reconstructed with ASiR-V 50%(86.42%),ASiR-V 70%(87.04%)and ASiR-V 90% (88.89%)(P＞0.05).The mean nodule diameter measurements were (6.4±2.0)mm,(5.9±2.2)mm,(6.0±2.2)mm and (6.1 ±2.2)mm for LDCT and ULDCT (ASiR-V 50%,70% and 90%),respectively with P＞0.05.Conclusion At extremely low exposure levels,ASiR-V can obviously improve the image qualities of ULDCT,and 90% is the best percentage for lung algorithm reconstruction with a high sensitivity of pulmonary nodule detection.

Comparison of lung nodule image quality using two adaptive statistical iterative reconstruction algorithms in chest CT:a phantom study / 实用放射学杂志

Objective To compare the values of the lung nodule image quality by using two adaptive statistical iterative reconstruction (ASIR)in a chest phantom CT imaging study.Methods Non-enhanced CT of chest phantom with routine dose was obtained on both GE Discovery CT and Revolution CT.The scan parameters included tube voltage of 120 kVp,a noise index of 14 HU,slice thickness of 5 mm.All scans were reconstructed with FBP and different percentages of (20%－100% ASIR)when using Discovery CT,and different percentages of ASIR-V (20%－100% ASIR-V)when using Revolution CT.The CT attenuation values and SD (the SD represented image noise)of the subcutaneous uniform tissue were measured at the level of thoracic entry,trachea carina and hepatic portal.Based on the standard FBP(FBPs )algorithm,the image noise reduction rate of reconstructed images using different iterative percentage of standard algorithms ASIR and ASIR-V(ASIRs and ASIR-Vs )were compared.The paired t test was used to compare the noise of ASIRs and ASIR-Vs images under the same iterative percentage.The subj ective image quality was independently evaluated by two experienced radiologists,Kappa test was used to evaluate consistency,Wilcoxon test was used to compare subjective scores.Results For all ASIRs and ASIR-Vs images,the objective image noise of subcutaneous uniform tissue decreased along with increasing percentage.Comparison with the average noises of CT image reconstructed with the FBPs algorithm,the image noise reconstructed with ASIRs from 20% to 1 00% were reduced by 1 1.0 6%－48.9 7%,while the image noise reconstructed with ASIR-Vs from 20% to 100% were reduced by 17.06%－79.50%.The image noise of different percentage ASIR-Vs was significantly lower than that of same percentage ASIRs between 40% and 1 00% (P＜0.05 ).In terms of subj ective image evaluation,all ASIR1 and ASIR-V1 reconstructions had good diagnostic acceptability.Two readers scored good or moderate consistency in each iterative reconstruction of each lung nodule.Nodules of smaller size and less dense were more likely to have score differences.The 60%ASIR1 showed significantly superior visibility of lung nodules when compared to other percentages (P＜0.05).60% and 80% ASIR-V1 series showed significantly superior visibility of lung nodules when compared to the 60% ASIR1 and ASIR-V1 of other percentages (P＜0.05).Conclusion In routine dose non-enhanced chest CT, ASIR-V shows greater potential in reducing image noise and improves lung nodule image quality when compared to the same level ASIR algorithm. Combining both the obj ective and subj ective evaluation of images,reconstructed with 60% and 80% ASIR-V in the non-enhanced chest CT image is recommended for the observation and evaluation of pulmonary nodules.

Feasibility of low-dose radiation CT scanning for liver 3D modeling printing / 医学研究生学报

Objective In the wide clinical practice of liver 3D printing, its related high-dose CT radiation has been somehow neglected and resulted in unnecessary radiation injury to the patients. This study was to explore the feasibility of liver 3D modeling printing with the low-dose radiation CT scanning technique.　Methods　This retrospective study included 40 patients undergoing liver 3D modeling printing from January 2016 to June 2018, who were equally randomized into a low-dose radiation group (100 kVp, by automated tube current modulation [ATCM] and adaptive statistical iterative reconstruction [ASIR]) and a normal-dose radiation group (120 kVp, 250 mA by filter back projection [FBP]), both with contrast agent Iohexol at 300 mgI/m1. We obtained the values of three-phase enhanced CT scanning of the abdominal aorta, portal vein and liver parenchyma, background noise (BN), volume CT dose index (CTDI), dose length product (DLP), contrast noise ratio (CNR) and effective radiation dose (ED). We input the CT DICOM data into the 3D printer for liver modeling printing and subjectively assessed the results. Results There were statistically significant differences between the low-dose and normal-dose radiation groups in the CTDI, DLP and ED (P 0.05). The ED was decreased about 35.8% in the low-dose group as compared with that in the normal-dose group ([2.58 ± 0.79] vs [4.02 ± 0.26] mSv, P 0.05). Conclusion Low-dose radiation CT scanning technology can meet the clinical requirement of liver 3D modeling printing and significantly reduce the patient’s exposure to CT radiation.

Feasibility study of automatic spectral imaging protocol selection combined with double low technique in CT portal vein imaging / 中华放射医学与防护杂志

Objective To explore the application value of virtual monochromatic imaging combined with adaptive statistical iterative reconstruction (ASIR) and automatic spectral imageing mode selection(ASIS) in reducing the radiation dose and contrast dose of CT portal venography.Methods We retrospectively collected 120 cases (80 males and 40 females) who underwent upper abdominal enhancement CT from January 2017 to April 2017.Patients were divided into 3 groups (40 cases in each group) according to the scanning program.Group A used conventional 120 kVp scan,NI =10,contrast agent dosage was 450 mgI/kg of body weight,image was reconstructed with 50％ ASIR technique;Groups B and C used spectral CT mode,NI =10 (Group B),NI =13 (Group C),the amount of contrast agent was 300 mgI/kg of body weight,and the image was reconstructed with 60 keV +50％ ASIR.One-way analysis of variance was used to compare the mean CT values and their differences,image noise,SNR and CNR of portal vein and liver parenchyma in three groups of images.Subjective image quality scores were performed on three groups of images by two senior radiologists.The patient's CTDIvol,DLP were recorded and the E was calculated.Results The amount of contrast agent in group B and C was reduced by about 30％ compared with group A.The portal vein CT values of groups A,B,and C were 168.22± 17.82,209.06±20.07,and 211.03±25.60.The portal vein CT values of group B and C were significantly higher than those of group A,respectively (t =-9.625,-8.680,P ＜ 0.05).The CT value difference between portal vein and liver parenchyma was 60.01± 17.01,106.63±25.83,107.72±25.39,respectively.SNRs were 8.48±1.41,12.64±2.94,10.77±1.94,and CNR were 5.16±1.80,8.13±2.54,7.32±1.84,respectively.The image quality scores were 3.53±0.68,4.75±0.54 and 4.53±0.64,respectively.The CT value difference,SNR,CNR and image quality scores of group B and group C were significantly higher than those in group A(t=-9.536,-9.857,-8.082,-6.064,-6.050,-5.308,-8.912,-6.779,P＜0.05).The CTDIvolof groups A,B and C were (12.15±5.02) mGy,(12.34±4.18) mGy,(10.03±3.13) mGy,DLP were (348.62± 155.99) mGy· cm,(355.56± 131.07) mGy·cm,(287.10±92.25) mGy·cm,respectively,E were (5.23±2.34) mSv,(5.33±1.97) mSv,(4.31±.1.38) mSv,compared with the A and B groups,the CTDI,ol,DLP and E of the C group were significantly lower(t=2.274,2.147,2.147,2.812,2.702,2.702,P＜0.05),and CTDIvol,DLP and E were decreased by 19％.Conclusions In CT portal venography,NI =13,60 keV combined with 50％ ASIR reconstruction and ASIS can be used to personalize the contrast dose and radiation dose of the patient and provide images that meet the diagnostic requirements.

The application value of spectral scanning combined with iterative reconstruction in double-low technique scanning for severe liver cirrhosis / 中华放射医学与防护杂志

Objective To investigate the clinical feasibility of spectral monochromatic imaging combined with adaptive statistical iterative reconstruction-V (ASIR-V) in upper abdominal enhanced scanning with double-low technique for severe liver cirrhosis.Methods Totally 126 cases performed abdominal contrast-enhanced CT scanning were collected prospectively and assigned to 3 groups with 42 cases in each group with random number table method.The filtered back projection algarithm,120 kV and contrast agent dose of 420 mgI/kg were used for the cases of control group.The cases for spectral group and combined group were scanned with spectral imaging mode and contrast agent dose of 300 mgI/kg.The 60 keV monochromatic images combined with pre-0％ and post-40％ ASIR-V were selected and analyzed for spectral group.Combined group with pre-40％ ASIR-V was divided into 2 subgroups with 50 keV,post -50％ ASIR-V and 60 keV,post-40％ ASIR-V separately.One-way ANOVA test was used for analysis of radiation dose and quantitative parameters,and Rank sum test was used for image subject evaluation.Results The CT numbers and CNR had significant differences among spectral group,combined group and control group(F=4.293-13.134,P＜0.05) except for the images of liver parenchyma in PVP and that of 50 keV combined 50％ASIR-V group were higher than that of control group (q=1.825-3.736,P＜0.05).No significant differences existed for image noise and overall image quality scores of organs in four groups.The visualization of hepatic vascular branches in 50 keV combined 50％ASIR-V group was higher than that of other three groups(Z=2.793-6.328,P＜0.05).The radiation dose of combined group was lower than that of spectral and control group (q =-4.879--2.531,P ＜ 0.001).Conclusions Spectral monochromatic imaging combined with pre-and post-ASIR-V can reduce contrast agent dose and radiation dose without degrading image quality for the severe liver cirrhosis in upper abdominal enhanced scanning.

Evaluation of the Impact of Iterative Reconstruction Algorithms on Computed Tomography Texture Features of the Liver Parenchyma Using the Filtration-Histogram Method

OBJECTIVE: To evaluate whether computed tomography (CT) reconstruction algorithms affect the CT texture features of the liver parenchyma. MATERIALS AND METHODS: This retrospective study comprised 58 patients (normal liver, n = 34; chronic liver disease [CLD], n = 24) who underwent liver CT scans using a single CT scanner. All CT images were reconstructed using filtered back projection (FBP), hybrid iterative reconstruction (IR) (iDOSE4), and model-based IR (IMR). On arterial phase (AP) and portal venous phase (PVP) CT imaging, quantitative texture analysis of the liver parenchyma using a single-slice region of interest was performed at the level of the hepatic hilum using a filtration-histogram statistic-based method with different filter values. Texture features were compared among the three reconstruction methods and between normal livers and those from CLD patients. Additionally, we evaluated the inter- and intra-observer reliability of the CT texture analysis by calculating intraclass correlation coefficients (ICCs). RESULTS: IR techniques affect various CT texture features of the liver parenchyma. In particular, model-based IR frequently showed significant differences compared to FBP or hybrid IR on both AP and PVP CT imaging. Significant variation in entropy was observed between the three reconstruction algorithms on PVP imaging (p 0.75) for CT imaging without filtration. CONCLUSION: CT texture features of the liver parenchyma evaluated using the filtration-histogram method were significantly affected by the CT reconstruction algorithm used.

Accelerated Time-of-Flight Magnetic Resonance Angiography with Sparse Undersampling and Iterative Reconstruction for the Evaluation of Intracranial Arteries

OBJECTIVE: To compare the image quality of three-dimensional time-of-flight (TOF) magnetic resonance angiography (MRA) with sparse undersampling and iterative reconstruction (sparse TOF) with that of conventional TOF MRA. MATERIALS AND METHODS: This study included 56 patients who had undergone sparse TOF MRA for intracranial artery evaluation on a 3T MR scanner. Conventional TOF MRA scans were also acquired from 29 patients with matched acquisition times and another 27 patients with matched scanning parameters. The image quality was scored using a five-point scale based on the delineation of arterial vessel segments, artifacts, overall vessel visualization, and overall image quality by two radiologists independently, and the data were analyzed using the non-parametric Wilcoxon signed-rank test. Contrast ratios (CRs) of vessels were compared using the paired t test. Interobserver agreement was calculated using the kappa test. RESULTS: Compared with conventional TOF at the same spatial resolution, sparse TOF with an acceleration factor of 3.5 could reduce acquisition time by 40% and showed comparable image quality. In addition, when compared with conventional TOF with the same acquisition time, sparse TOF with an acceleration factor of 5 could also achieve higher spatial resolution, better delineation of vessel segments, fewer artifacts, higher image quality, and a higher CR (p < 0.05). Good-to-excellent interobserver agreement (κ: 0.65–1.00) was obtained between the two radiologists. CONCLUSION: Compared with conventional TOF, sparse TOF can achieve equivalent image quality in a reduced duration. Furthermore, using the same acquisition time, sparse TOF could improve the delineation of vessels and decrease image artifacts.

Application of Vendor-Neutral Iterative Reconstruction Technique to Pediatric Abdominal Computed Tomography

OBJECTIVE: To compare image qualities between vendor-neutral and vendor-specific hybrid iterative reconstruction (IR) techniques for abdominopelvic computed tomography (CT) in young patients. MATERIALS AND METHODS: In phantom study, we used an anthropomorphic pediatric phantom, age-equivalent to 5-year-old, and reconstructed CT data using traditional filtered back projection (FBP), vendor-specific and vendor-neutral IR techniques (ClariCT; ClariPI) in various radiation doses. Noise, low-contrast detectability and subjective spatial resolution were compared between FBP, vendor-specific (i.e., iDose1 to 5; Philips Healthcare), and vendor-neutral (i.e., ClariCT1 to 5) IR techniques in phantom. In 43 patients (median, 14 years; age range 1–19 years), noise, contrast-to-noise ratio (CNR), and qualitative image quality scores of abdominopelvic CT were compared between FBP, iDose level 4 (iDose4), and ClariCT level 2 (ClariCT2), which showed most similar image quality to clinically used vendor-specific IR images (i.e., iDose4) in phantom study. Noise, CNR, and qualitative imaging scores were compared using one-way repeated measure analysis of variance. RESULTS: In phantom study, ClariCT2 showed noise level similar to iDose4 (14.68–7.66 Hounsfield unit [HU] vs. 14.78–6.99 HU at CT dose index volume range of 0.8–3.8 mGy). Subjective low-contrast detectability and spatial resolution were similar between ClariCT2 and iDose4. In clinical study, ClariCT2 was equivalent to iDose4 for noise (14.26–17.33 vs. 16.01–18.90) and CNR (3.55–5.24 vs. 3.20–4.60) (p > 0.05). For qualitative imaging scores, the overall image quality ([reader 1, reader 2]; 2.74 vs. 2.07, 3.02 vs. 2.28) and noise (2.88 vs. 2.23, 2.93 vs. 2.33) of ClariCT2 were superior to those of FBP (p 0.05). CONCLUSION: Vendor-neutral IR technique shows image quality similar to that of clinically used vendor-specific hybrid IR technique for abdominopelvic CT in young patients.

Impact of Model-Based Iterative Reconstruction on the Correlation between Computed Tomography Quantification of a Low Lung Attenuation Area and Airway Measurements and Pulmonary Function Test Results in Normal Subjects

OBJECTIVE: To compare correlations between pulmonary function test (PFT) results and different reconstruction algorithms and to suggest the optimal reconstruction protocol for computed tomography (CT) quantification of low lung attenuation areas and airways in healthy individuals. MATERIALS AND METHODS: A total of 259 subjects with normal PFT and chest CT results were included. CT scans were reconstructed using filtered back projection, hybrid-iterative reconstruction, and model-based IR (MIR). For quantitative analysis, the emphysema index (EI) and wall area percentage (WA%) were determined. Subgroup analysis according to smoking history was also performed. RESULTS: The EIs of all the reconstruction algorithms correlated significantly with the forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) (all p < 0.001). The EI of MIR showed the strongest correlation with FEV1/FVC (r = −0.437). WA% showed a significant correlation with FEV1 in all the reconstruction algorithms (all p < 0.05) correlated significantly with FEV1/FVC for MIR only (p < 0.001). The WA% of MIR showed the strongest correlations with FEV1 (r = −0.205) and FEV1/FVC (r = −0.250). In subgroup analysis, the EI of MIR had the strongest correlation with PFT in both ever-smoker and never-smoker subgroups, although there was no significant difference in the EI between the reconstruction algorithms. WA% of MIR showed a significantly thinner airway thickness than the other algorithms (49.7 ± 7.6 in ever-smokers and 49.5 ± 7.5 in never-smokers, all p < 0.001), and also showed the strongest correlation with PFT in both ever-smoker and never-smoker subgroups. CONCLUSION: CT quantification of low lung attenuation areas and airways by means of MIR showed the strongest correlation with PFT results among the algorithms used, in normal subjects.

Comparison of Filtered Back Projection, Hybrid Iterative Reconstruction, Model-Based Iterative Reconstruction, and Virtual Monoenergetic Reconstruction Images at Both Low- and Standard-Dose Settings in Measurement of Emphysema Volume and Airway Wall Thick

OBJECTIVE: To evaluate the accuracy of emphysema volume (EV) and airway measurements (AMs) produced by various iterative reconstruction (IR) algorithms and virtual monoenergetic images (VME) at both low- and standard-dose settings. MATERIALS AND METHODS: Computed tomography (CT) images were obtained on phantom at both low- (30 mAs at 120 kVp) and standard-doses (100 mAs at 120 kVp). Each CT scan was reconstructed using filtered back projection, hybrid IR (iDose4; Philips Healthcare), model-based IR (IMR-R1, IMR-ST1, IMR-SP1; Philips Healthcare), and VME at 70 keV (VME70). The EV of each air column and wall area percentage (WA%) of each airway tube were measured in all algorithms. Absolute percentage measurement errors of EV (APEvol) and AM (APEWA%) were then calculated. RESULTS: Emphysema volume was most accurately measured in IMR-R1 (APEvol in low-dose, 0.053 ± 0.002; APEvol in standard-dose, 0.047 ± 0.003; all p 0.05). VME70 showed a significantly higher APEvol than iDose4, IMR-R1, and IMR-ST1 (all p < 0.004). VME70 also showed a significantly higher APEWA% compared with the other algorithms (all p < 0.001). CONCLUSION: IMR was the most accurate technique for measurement of both EV and airway wall thickness. However, VME70 did not show a significantly better accuracy compared with other algorithms.

Effect of Hybrid Kernel and Iterative Reconstruction on Objective and Subjective Analysis of Lung Nodule Calcification in Low-Dose Chest CT

OBJECTIVE: To evaluate the differences in subjective calcification detection rates and objective calcium volumes in lung nodules according to different reconstruction methods using hybrid kernel (FC13-H) and iterative reconstruction (IR). MATERIALS AND METHODS: Overall, 35 patients with small (< 4 mm) calcified pulmonary nodules on chest CT were included. Raw data were reconstructed using filtered back projection (FBP) or IR algorithm (AIDR-3D; Canon Medical Systems Corporation), with three types of reconstruction kernel: conventional lung kernel (FC55), FC13-H and conventional soft tissue kernel (FC13). The calcium volumes of pulmonary nodules were quantified using the modified Agatston scoring method. Two radiologists independently interpreted the role of each nodule calcification on the six types of reconstructed images (FC55/FBP, FC55/AIDR-3D, FC13-H/FBP, FC13-H/AIDR-3D, FC13/FBP, and FC13/AIDR-3D). RESULTS: Seventy-eight calcified nodules detected on FC55/FBP images were regarded as reference standards. The calcium detection rates of FC55/AIDR-3D, FC13-H/FBP, FC13-H/AIDR-3D, FC13/FBP, and FC13/AIDR-3D protocols were 80.7%, 15.4%, 6.4%, 52.6%, and 28.2%, respectively, and FC13-H/AIDR-3D showed the smallest calcium detection rate. The calcium volume varied significantly with reconstruction protocols and FC13/AIDR-3D showed the smallest calcium volume (0.04 ± 0.22 mm³), followed by FC13-H/AIDR-3D. CONCLUSION: Hybrid kernel and IR influence subjective detection and objective measurement of calcium in lung nodules, particularly when both techniques (FC13-H/AIDR-3D) are combined.

Contrast-Enhanced CT with Knowledge-Based Iterative Model Reconstruction for the Evaluation of Parotid Gland Tumors: A Feasibility Study

OBJECTIVE: The purpose of this study was to determine the diagnostic utility of low-dose CT with knowledge-based iterative model reconstruction (IMR) for the evaluation of parotid gland tumors. MATERIALS AND METHODS: This prospective study included 42 consecutive patients who had undergone low-dose contrast-enhanced CT for the evaluation of suspected parotid gland tumors. Prior or subsequent non-low-dose CT scans within 12 months were available in 10 of the participants. Background noise (BN), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were compared between non-low-dose CT images and images generated using filtered back projection (FBP), hybrid iterative reconstruction (iDose⁴; Philips Healthcare), and knowledge-based IMR. Subjective image quality was rated by two radiologists using five-point grading scales to assess the overall image quality, delineation of lesion contour, image sharpness, and noise. RESULTS: With the IMR algorithm, background noise (IMR, 4.24 ± 3.77; iDose⁴, 8.77 ± 3.85; FBP, 11.73 ± 4.06; p = 0.037 [IMR vs. iDose⁴] and p < 0.001 [IMR vs. FBP]) was significantly lower and SNR (IMR, 23.93 ± 7.49; iDose⁴, 10.20 ± 3.29; FBP, 7.33 ± 2.03; p = 0.011 [IMR vs. iDose⁴] and p < 0.001 [IMR vs. FBP]) was significantly higher compared with the other two algorithms. The CNR was also significantly higher with the IMR compared with the FBP (25.76 ± 11.88 vs. 9.02 ± 3.18, p < 0.001). There was no significant difference in BN, SNR, and CNR between low-dose CT with the IMR algorithm and non-low-dose CT. Subjective image analysis revealed that IMR-generated low-dose CT images showed significantly better overall image quality and delineation of lesion contour with lesser noise, compared with those generated using FBP by both reviewers 1 and 2 (4 vs. 3; 4 vs. 3; and 3–4 vs. 2; p < 0.05 for all pairs), although there was no significant difference in subjective image quality scores between IMR-generated low-dose CT and non-low-dose CT images. CONCLUSION: Iterative model reconstruction-generated low-dose CT is an alternative to standard non-low-dose CT without significantly affecting image quality for the evaluation of parotid gland tumors.

Application research of double low scanning technology combined with iterative reconstruction technique in CT angiography of pediatric complex congenital heart disease / 中华放射医学与防护杂志

Objective@#To evaluate the feasibility of CT angiography of pediatric complex congenital heart disease by using low radiation dose and low isotonic contrast agent dose combined with iDose4 iterative reconstruction technique.@*Methods@#Prospectively, a total of 57 continuous patients with suspected congenital heart disease under or equal to 2 years old in our hospital between Mar 2016 and Jan 2017 were divided into 2 groups according to the reservation number. " double low" group included 32 patients using 80 kVp, 80 mAs, Iodixanol (270 mg I/ml) and iDose4 - 4iterative reconstruction algorithm; routine group included 25 patients using 100 kVp, 100 mAs, Iopromide (370 mg I/ml) and filtered back projection algorithm. Individualized injections were taken on the weight of children and the iodine intake was calculated. CT values of left atrium, left ventricle, right atrium, right ventricle, ascending and descending aorta at the level of tracheal bifurcation, midpoint of aortic arch, pulmonary trunk, left and right pulmonary artery, pectoralis major and erector spinae on both sides as well as background noise at the level of aortic arch were measured, and signal to noise ratios (SNR) and contrast to noise ratios (CNR) were calculated. The quality of all images was evaluated subjectively. Scan length (L), volume CT dose index (CTDIvol) and dose-length-product (DLP) were recorded, and the effective dose (E) and size-specific dose estimate (SSDE) were calculated. The diagnostic coincidence rates for CTA examinations of these two groups were calculated and compared with the surgery or cardiac catheterization examination called the " gold standard" .@*Results@#The iodine intake of " double low" group and routine group was (2.53±1.09) and (3.46±1.29)g, respectively, with statistically significant difference (t=2.976, P<0.05). No statistically significant difference existed in CT value of heart cavities, large blood vessels or CT value of muscles, background noise, SNR, CNR at the level of aortic arch or subjective evaluation for image quality between the two groups (P>0.05). The consistency of subjective evaluation for image quality of the two groups was good(Kappa=0.55, 0.76). Compared with routine group, CTDIvol, SSDE, DLP, E of double low group descended by 57.19%, 56.71%, 56.74%, 53.33% respectively (t=54.107, 28.269, 15.338, 11.441, P<0.05). The diagnostic coincidence rates of the two groups were 96.6% and 97.1% respectively (P>0.05).@*Conclusions@#Using 80 kVp, 80 mAs and Iodixanol (270 mg I/ml) combined with iDose4 iterative reconstruction technique for CT angiography of pediatric complex congenital heart disease, the image quality could meet the requirements for clinical diagnosis, and the radiation dose and the iodine dose of contrast agent could be lowered.@*Trial registration@#Chinese clinical trial registry, ChiCTR1800016576.

The investigation on image quality and radiation dose of low dose wider detector array CT scanning for young children with congenital heart disease / 中华放射医学与防护杂志

Objective To investigate the image quality and radiation dose of the wider detector array CT scanner with low dose scanning mode in young children with congenital heart disease.Methods Totally 100 consecutive pediatric patients younger than 3 years with congenital heart disease were enrolled.They were divided into two groups.The low dose group with fifty patients underwent axial CT scanning with ECG gating,and the control group with fifty patients were scanned with volume helical shuttle (VHS) technique.CT number and noise of two groups images at the level of ascending aorta,main pulmonary artery,left ventricle,descending aorta and adjacent muscle were measured,and the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated.The double blind method was used to evaluate subjective image quality of the level of intra-cardiac,extra-cardiac and coronary artery.Effective dose was also calculated for both groups.Results No significant difference was found in the CT number,image noise,SNR,and CNR between the two groups in the same anatomic regions (P ＞ 0.05).No significant difference was found in subjective image quality between the two groups for the intra-cardiac and extra-cardiac structure(P ＞0.05).The subjective image quality of coronary artery was significant higher in low dose group than the control group(4.10 ± 0.90 vs.2.88 ± 0.82,Z =-5.818,P ＜ 0.05).Effective dose was (0.57 ± 0.30)mSv in group A and (2.39 ± 1.15)mSv in group B with dose savings of 76％ (t =-11.642,P ＜ 0.05).Conclusions The wider detector array CT scanner with low dose scanning mode can improve image quality with lower radiation dose.