Feasibility study of low tube voltage and low contrast medium combined with IMR technology in 3DCTA of vertebral artery V3 segment / 重庆医学

Objective To investigate the feasibility of low-voltage,automatic tube current adjustment(ATCM)and low contrast agent concentration,dose and injection rate combined with full-model iterative re-construction(IMR)in vertebral artery V3-segment three-dimensional CT angiography(3DCTA).Methods A total of 60 patients with suspected upper cervical spine,craniocervical junction lesions undergoing cervical vertebral artery V3 segment 3DCTA in this hospital from November 2019 to May 2020 were selected and divided into the group A and B by adopting the random number table method,30 cases in each group.The group A adopted the ATCM technology of 80 kV,average tube current of 50 mAs,25 mL of contrast agent io-hexol(iodine content 300 mg/mL)combined IMR technology with an injection rate of 3 mL/s,while the group B adopted 120 kV,150 mAs fixed tube current,50 mL injection rate of 5 mL/s contrast agent iopamidol(iodine content 370 mg/mL)combined filter back projection(FBP)reconstruction technology.CT value,noise,signal-to-noise ratio(SNR),contrast noise ratio(CNR)and image sensitivity(FOM)were measured and compared between the two groups and the quality of the resulting images was evaluated.The CT volumet-ric dose index(CTDIvol)and dose-length product(DLP)were recorded,and the effective dose(ED)was cal-culated.Results There was no statistically significant difference in the vertebral arterial CT value between the two groups(P＞0.05),but the noise of the group A was lower than that of the group B(P＜0.05),SNR,CNR and FOM of the group A were greater than those of the group B(P＜0.05).The image quality of the two groups met the requirements of clinical diagnosis[(4.78±0.41)points vs.(4.85±0.35)points],and there was no statistically significant difference in the subjective evaluation of image quality(P＞0.05).The CTDIvol,DLP and ED levels in the group A were lower than those in the group B(P＜0.05).The iodine in-takes of contrast medium in the group A and group B were 7.5 g and 18.5 g,respectively,and the iodine flow rates of contrast agent were 0.9 and 1.85 mg/s,respectively,and compared with group B,the iodine intake and iodine flow rate of the group A were decreased by 59.5％and 51.4％,respectively.Conclusion Low tube voltage ATCM and low contrast concentration,dose and injection rate combined with IMR technology can not only ensure the 3DCTA image quality of vertebral artery V3 segment,but also reduce the radiation dose re-ceived by the patients,and reduce the iodine intake and iodine flow rate of contrast agent.

Application of deep learning image reconstruction combined with computer-aided diagnosis in CT screening of pulmonary nodules / 实用放射学杂志

Objective To analyze the effects of deep learning image reconstruction(DLIR)and adaptive statistical iterative recon-struction V(ASIR-V)on the imaging quality of chest CT in patient with pulmonary nodules,and to evaluate the differences based on different image reconstruction techniques in the detection of efficiency of computer-aided diagnosis(CAD)for pulmonary nodules.Methods The image data of pulmonary nodules of eighty patients with chest CT screening were reconstructed with ASIR-V 80％,DLIR-low(DLIR-L),DLIR-medium(DLIR-M)and DLIR-high(DLIR-H)images,respectively.The objective image quality and sub-jective image quality of the four groups were compared and analyzed.Objective image quality includes CT value of region of interest(ROI),noise,signal-to-noise ratio(SNR),contrast-to-noise ratio(CNR)and image average gradient.The diagnostic efficacy of CAD in detecting pulmonary nodules of reconstructed images among four groups were further evaluated.Results There were no signifi-cant difference in CT value of ROI of reconstructed images among the four groups(P＞0.05).The noise,SNR and CNR of DLIR-H images were similar to those of ASIR-V 80％(P＞0.05),but significantly better than those of DLIR-L and DLIR-M(P＜0.05).The average gradient of DLIR-L,DLIR-M and DLIR-H images were significantly higher than those of ASIR-V 80％(P＜0.05).The subjective image quality scores of DLIR-L,DLIR-M and DLIR-H images were significantly higher than those of ASIR-V 80％(P＜0.05),and the subjective image quality score of DLIR-H image was the highest.CAD showed the highest true positive rate in DLIR-H images for detecting pulmonary nodules(P＜0.05),and CAD showed the highest false positives per capita in ASIR-V 80％images for detecting pulmonary nodules(P＜0.05).Conclusion The noise,SNR and CNR of DLIR-H images are similar to those of ASIR-V 80％,with the significantly higher image clarity and subjective image quality scores.DLIR-H has advantages in CAD detection of pulmonary nodules,which is an ideal image reconstruction technology for chest CT pulmonary nodule screening.

Application value of 100 kVp low tube voltage combined with ASIR-V in Adamkiewicz artery imaging of spinal cord / 实用放射学杂志

Objective To investigate the effect of 100 kVp low tube voltage combined with adaptive statistical iterative reconstruc-tion-Veo(ASIR-V)on the imaging display,image quality and radiation dose of Adamkiewicz artery(AKA).Methods Ninety patients with computed tomography angiography(CTA)of aorta were randomly divided into two groups.In group A,the tube voltage was 100 kVp,and ASIR-V was 80%reconstructed.The tube voltage in group B was 120 kVp,and adaptive statistical iterative recon-struction(ASIR)was 40%reconstructed.The CT value and the standard deviation(SD)value of descending aorta were measured at the 12th thoracic vertebra level,and the CT value and the SD value of the spinal cord were measured at the same level to calculate the signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR)of AKA.According to the continuity between AKA and intercostal artery or lumbar artery,the visualization of AKA was evaluated by two doctors with a double-blinded method and a five-point method,and the radiation doses of group A and group B were compared.Results Compared with group B,the CT value of aorta in group A was sig-nificantly increased by about 22.83%(P<0.001).The background noise of AKA in group A was significantly lower than that in group B(P<0.001),and the SNR and CNR were significantly higher than those in group B(P<0.001).The visualization score of AKA in group A was higher than that in group B(P<0.05).The effective dose(ED)in group A was significantly lower than that in group B by about 41.28%(P<0.001).Conclusion 100 kVp combined with ASIR-V technique for spinal cord AKA imaging can obtain better image quality,improve the sensitivity of AKA display and reduce the radiation dose.

Application of Forward Projected Model-Based Iterative Reconstruction Solution in Improving Image Quality of Head and Neck CT Angiography / 中国医学影像学杂志

Purpose To explore the application value of forward projected model-based iterative reconstruction solution(FIRST)algorithm improving image quality of 100 kV low-dose head and neck CT angiography(CTA).Materials and Methods A total of 32 patients who underwent head and neck CTA examinations in the Beijing Hospital from September to October 2021 were retrospectively recruited.All patients were divided into three groups based on different reconstruction,including the filtered back projection(FBP)group,the adaptive iterative dose reduction 3D(AIDR 3D)group,and the FIRST group.The average CT value,image noise,signal-to-noise ratio,contrast to noise ratio and other objective indicators of the main blood vessels images(including common carotid artery,vertebral artery,internal carotid artery C1,C4,middle cerebral artery M1,M3 and anterior cerebral artery A1,A3)and background(including muscle,brain tissue)in the head and neck of the three groups were recorded and analyzed,respectively.The subjective imaging evaluation was scored and analyzed.Digital subtraction angiography(DSA)was used as the gold standard to evaluate the detection of vascular stenosis in the head and neck by each reconstruction algorithm.Results Compared with the AIDR 3D group and the FBP group,the FIRST group significantly reduced the image noise of the blood vessels and the background(muscle,brain tissue)(t=-13.19--7.28,all P<0.001).The signal-to-noise ratio and contrast to noise ratio of the FIRST group were significantly higher than those of the FBP group,AIDR 3D group(t=2.17-9.67,all P<0.001).The CT values of FIRST group were significantly higher than those of AIDR 3D group in the common carotid artery,internal carotid artery C1 and C4,middle cerebral artery M1,and anterior cerebral artery A1 segment(t=1.28-3.60,all P<0.05).The CT value of background(muscle,brain tissue)in FIRST group was significantly lower than those in the FBP group and the AIDR 3D group,with statistically significant difference(t=-7.63--4.03,all P<0.001).The images of FIRST group and AIDR 3D group met the diagnostic requirements,and the subjective scores of the two groups were significantly higher than those of the FBP group images(all P<0.05).The imaging scores of FIRST group were significantly higher than those of AIDR 3D group(P<0.05).Compared with DSA,FBP was ineffective for mild and moderate stenosis;FIRST and AIDR 3D algorithms were consistent with DSA.Conclusion Compared with traditional FBP and AIDR 3D reconstruction algorithms,FIRST algorithm can effectively improve the image quality of low-dose head and neck CTA and obtain better image quality and meet the diagnostic performance of head and neck vascular diseases.

Comparison of image quality based on deep-learning image reconstruction and iterative reconstruction algorithm for dual-energy CT: a phantom and animal-model study / 中华放射学杂志

Objective:To investigate the impact of the deep learning reconstruction algorithm TrueFidelity TM for Gemstone Spectral Imaging (TF-GSI) and the adaptive statistical iterative reconstruction algorithm (ASiR-V, hereinafter referred to as ASiR-V) based on phantom and animal models on the image quality of dual-energy CT images. Methods:GE Revolution Apex CT was used to scan the ACR 464 phantom and a mouse model of gastric cancer with lymph node metastasis ( n=16). TF-GSI and ASiR-V were separately used to reconstruct middle and high-grade images (TF-GSI-M, TF-GSI-H, ASiR-V-50%, and ASiR-V-100%) on the phantom and mouse based on virtual monoenergetic images at 70 keV. The task transfer function (TTF) of bone and acrylic, image noise power spectrum (NPS), and detectability index (d′) of the phantom images were evaluated. One-way ANOVA analysis was used to compare the image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for brain and liver on images of mice. The consistency of the two reconstruction-algorithm images (TF-GSI-H and ASiR-V100%) in the detection of small lesions by two radiologists (A and B) was evaluated using kappa test. Results:In terms of the phantom, the TF-GSI-H group had the best performance in TTF, NPS, and d′. Compared to ASiR-V-100%, the TTF50% of bone and acrylic in the TF-GSI-H group increased by 2.4% and 8.9%, respectively; the NPS peak decreased by 54.1%, compared to ASiR-V-100%; the d′ of bone and acrylic in the TF-GSI-H group relative to ASiR-V-100% increased by 52.7% and 59.5%, respectively. The TF-GSI group had reduced image noise compared to the ASiR-V group, and both SNR and CNR of the two tissues increased, but the differences between the groups were not statistically significant (all P>0.05). The two reconstruction-algorithm images showed good consistency in image evaluation by the two radiologists (A, Kappa=0.875, P<0.001; B, Kappa=0.625, P=0.012). In terms of the detection of micro-metastases in mice, the TF-GSI group outperformed the ASiR-V group (average accuracy: 83.5% vs 71.9%; average sensitivity: 77.8% vs 61.2%; average specificity: 85.7% vs 85.7%). Conclusion:Compared with iterative reconstruction algorithm, the DLIR algorithm showed improved spatial resolution, reduced image noise, and enabled detectability of micro-lesion for images from dual-energy CT.

Feasibility study on deep learning image reconstruction algorithm to improve the quality of low-dose CT images of the brain / 中华放射医学与防护杂志

Objective:To explore the effectiveness of deep learning image reconstruction (DLIR) algorithm compared to adaptive statistical iterative reconstruction (ASIR-V) algorithm in improving the quality of low-dose brain CT images.Methods:Retrospective inclusion of patients who underwent brain CT examination in the People's Liberation Army General Hospital from November 2021 to August 2022. Four different algorithms were used to reconstruct low-dose CT scans of all patients to obtain 30% intensity ASIR-V (ASIR-V-30%) images, low intensity DLIR (DLIR-L) images, medium intensity DLIR (DLIR-M) images, and high intensity DLIR (DLIR-H) images. The regions of interest were selected from four sets of images, including superficial white matter, superficial gray matter, deep white matter, and deep gray matter, and their CT values and standard deviations were measured for calculating signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR).Subjective evaluation of image quality was conducted by three neuroimaging physicians based on the Likert 5-component scale. The objective and subjective scores of the 4 groups of images were analyzed using ANOVA or Kruskal Wallis. If there are overall differences, pairwise comparisons were conducted within the group.Results:A total of 109 patients were enrolled, including 104 males and 5 females, aged 65-110 years (89.16 ± 9.53) years. The radiation exposure of brain CT low-dose scanning was (0.93 ± 0.01)mSv, significantly lower than that of conventional scanning (2.92 ± 0.01) mSv ( t = 56.15, P < 0.05). The differences in objective image quality analysis of ASIR-V-30%, DLIR-L, DLIR-M, and DLIR-H images of low-dose CT in SNR deep gray matter, SNR deep white matter, SNR superficial gray matter, SNR superficial white matter, CNR deep gray white matter, and CNR superficial gray white matter were statistically significant( F =98.23, 72.95, 68.43, 58.24, 241.13, 289.91, P < 0.05). Among them, DLIR-H images had the lowest noise in deep gray matter, deep white matter, superficial gray matter, and superficial white matter, and had statistically significant differences compared to other image groups ( t = 167.43, 275.46, 182.32, 361.54, P < 0.05). The subjective score of DLIR-H image quality was superior to ASIR-V-30%, DLIR-L, and DLIR-M, with the statistically significant difference ( t = 7.25, 8.32, 9.63, P < 0.05). Conclusions:Compared with ASIR-V, DLIR algorithm can effectively reduce image noise and artifacts in low-dose brain CT, and improve SNR and CNR. The subjective and objective image quality evaluation of DLIR-H is the best.

Study of CT dual-low technology angiography in patients with stroke / 中国现代医生

Objective This study focused on the low voltage and low concentration contrast agent technology in vascular imaging of stroke patients.Methods Totally144 patients of ischemic stroke confirmed from January 2022 to January 2023 were enrolled.They were divided into four groups according to different imaging methods:conventional group(tube voltage 120kV,iodine concentration 370mgI/ml),low voltage group(tube voltage 80kV,iodine concentration 370mgI/ml),low concentration group(tube voltage 120kV,iodine concentration 320mgI/ml)and dual-low group(tube voltage 80kV,iodine concentration 320mgI/ml),the post-processing technology adopted ASiR algorithm for 3D reconstruction.Then to compare contrast signal-to-noise ratio(CNR)and signal-to-noise ratio(SNR)of the reconstructed image,image quality score,CT values of internal carotid artery(ICA),anterior cerebral artery(AA)A1,middle cerebral artery(MA)M1,posterior cerebral artery(PA)P1,vertebral artery(VA)and basilar artery(BA),mean iodine intake and radiation dose parameters including volume CT dose index(CTDIvol)and dose length product(DLP).Results The CNR and SNR values in dual-low group were significantly less than the other three groups(P<0.05),while image quality score and CT value of each artery were no differences among the four groups(P>0.05).What's more,CTDIvol,DLP and iodine intake volume in dual-low group were significantly less than the others(P<0.05).Conclusion The dual-low technology scanning could obtain satisfactory head and neck CT angiography for stroke patients.

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.

Deep learning reconstruction algorithm in improving portal vein CT image quality / 西安交通大学学报(医学版)

【Objective】 To explore the value of deep learning reconstruction algorithm (DLIR) in improving image quality of portal vein. 【Methods】 We retrospectively enrolled 32 patients who underwent double-phasic enhanced abdominal CT scanning. Images at the portal venous phase were reconstructed using the 50% adaptive statistical iterative reconstruction (ASIR-V), DLIR at medium (DLIR-M) and high strength (DLIR-H). The CT value and image noise (standard deviation) of the main portal vein, the right portal vein branch, the left portal vein branch, and the paravertebral muscle were measured, and the contrast-noise-ratio (CNR) for vessels were calculated. Moreover, the edge-rising-slope (ERS) of the main portal vein edge was measured to evaluate image spatial resolution. The overall image noise, image contrast, and portal vein branch display were evaluated using a 5-point grading scale and image artifacts using a 4-point grading scare by two experienced radiologists. In addition, we calculated the display rate of small branches of the portal vein in the three reconstruction algorithms. 【Results】 Image noise of the DLIR images in the main portal vein, right branch and left branch was significantly lower than that of ASIR-V 50% images, of which the DLIR-H images had the lowest noise and highest CNR. The ERS of the DLIR images in the main portal vein was significantly higher than that of the ASIR-V 50% images. For qualitative analyses, the DLIR images were significantly better than the ASIR-V 50% ones (P<0.01). In addition, the display rates of small branches of the portal vein in DLIR images were (DLIR-M: 93.75%; DLIR-H: 100%), significantly higher than that of ASIR-V 50% (68.75%). 【Conclusion】 Compared with ASIR-V 50% images, DLIR images can significantly reduce the image noise and improve the spatial resolution of the portal vein and the display rate of small branches of the portal vein.

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.

The effects of 80 kVp combined with ASiR-V on image quality of iliac artery in preoperative evaluation of kidney transplantation / 西安交通大学学报(医学版)

【Objective】 To investigate the effects of 80 kVp combined with multi-model adaptive statistical iterative reconstruction algorithm （ASiR-V） on the image quality of CT angiography （CTA） of iliac artery in kidney transplantation candidates before operation. 【Methods】 Totally 50 kidney transplantation candidates underwent “one-stop” scanning combined CTA for coronary and iliac arteries were recruited consecutively. After the scanning， images were reconstructed with different ASiR-V levels on the iliac artery from 50% to 100% at a 10% interval， and 6 groups of images were obtained. We evaluated and compared all image qualities， DLP and CTDI in the patients’ examination were recorded， and the effective dose （ED） was calculated. 【Results】 All of the image quality objective scores of different ASiR-V levels on the iliac artery were above 3 points （3.32±0.24）， and the average CT value was （344.30±74.53）HU. The ED received by the patient throughout the examination was （2.71±0.42)mSv. The image noise decreased while SNR and CNR increased monotonically as the ASiR-V levels increased， among which 80% ASiR-V image quality score was the highest with 3.41±0.26. 【Conclusion】 For patients who need to have both coronary and iliac arteries evaluated before kidney transplantation operation， low tube voltage （80 kVp） combined with 80% ASiR-V can obtain high-quality iliac artery images under the premise of reducing the ED dose， which can provide practical basis for further reducing the dose in personalized scanning scheme for such patients. It has good feasibility and clinical application value.

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).

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.

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.

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.

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.

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.

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.