Wide-detector CT Research Articles

A Review of Factors Affecting Radiation Dose and Image Quality in Coronary CTA Performed with Wide-Detector CT

Compared with traditional invasive coronary angiography (ICA), coronary CT angiography (CCTA) has the advantages of being rapid, economical, and minimally invasive. The wide-detector CT, with its superior temporal resolution and robust three-dimensional reconstruction technology, thus enables CCTA in patients with high heart rates and arrhythmias, leading to a high potential for clinical application. This paper systematically summarizes wide-detector CT hardware configurations of various vendors routinely used for CCTA examinations and reviews the effects of patient heart rate and heart rate variability, scanning modality, reconstruction algorithms, tube voltage, and scanning field of view on image quality and radiation dose. In addition, novel technologies in the field of CT applied to CCTA examinations are also presented. Since this examination has a diagnostic accuracy that is highly consistent with ICA, it can be further used as a routine examination tool for coronary artery disease in clinical practice.

Motion correction of wide-detector 4DCT images for cardiac resynchronization therapy planning

BackgroundLead placement at the latest mechanically activated left ventricle (LV) segments is strongly correlated with response to cardiac resynchronization therapy (CRT). We demonstrate the feasibility of a cardiac 4DCT motion correction algorithm (ResyncCT) in estimating LV mechanical activation for guiding lead placement in CRT. MethodsSubjects with full cardiac cycle 4DCT images acquired using a wide-detector CT scanner for CRT planning/upgrade were included. 4DCT images exhibited motion artifact-induced false-dyssynchrony, hindering LV mechanical activation time estimation. Motion-corrupted images were processed with ResyncCT to yield motion-corrected images. Time to onset of shortening (TOS) was estimated in each of 72 endocardial segments. A false-dyssynchrony index (FDI) was used to quantify the extent of motion artifacts in the uncorrected and the ResyncCT images. After motion correction, the change in classification of LV free-wall segments as optimal target sites for lead placement was investigated. ResultsTwenty subjects (70.7 ​± ​13.9 years, 6 female) were analyzed. Motion artifacts in the ResyncCT-processed images were significantly reduced (FDI: 28.9 ​± ​9.3 ​% vs 47.0 ​± ​6.0 ​%, p ​< ​0.001). In 10 (50 ​%) subjects, ResyncCT motion correction yielded statistically different TOS estimates (p ​< ​0.05). Additionally, 43 ​% of LV free-wall segments were reclassified as optimal target sites for lead placement after motion correction. ConclusionsResyncCT significantly reduced motion artifacts in wide-detector cardiac 4DCT images, yielded statistically different time to onset of shortening estimates, and changed the location of optimal target sites for lead placement. These results highlight the potential utility of ResyncCT motion correction in CRT planning when using wide-detector 4DCT imaging.

CT annulus sizing prior to transcatheter aortic valve replacement (TAVR): evaluation of free-breathing versus breath-holding acquisition.

To assess feasibility and accuracy of aortic annulus measurements using cardiac computed tomography angiography (CTA) performed during free-breathing prior to transcatheter aortic valve replacement (TAVR). Sixty consecutive TAVR candidates underwent free-breathing wide-detector cardiac CTA, followed by a percutaneous valve replacement. For each, a theoretical valve size was suggested through CT measurements of the annulus, then compared to the size of the actual implanted transcatheter heart valve (THV). The procedural success and the 30-day outcomes were collected. Image quality of the annulus was also studied according to subjective and objective criteria. Data of a control group of 60 patients previously evaluated on breath-holding were also evaluated. A total of 120 patients (mean age, 83years ± 7, 60 men) were evaluated. All CT acquisitions provided sufficient image quality allowing precise annulus measurements. Mean attenuation (p < 0.001) and image noise (p = 0.01) were higher in the free-breathing group, while image quality was comparable (p = 0.36). The agreement rate between CT-suggested valve size and THV implanted size was comparable, estimated at 87% (κ = 0.79, 95%CI 0.566, 0.908) on free-breathing vs. 82% (κ = 0.78, 95%CI 0.634, 0.904) on breath-holding. The procedure was successful for all patients without increase in 30-day mortality or adverse events. Free-breathing cardiac CTA allows accurate aortic annulus measurements without compromising image quality or patients' outcome after TAVR. Elderly patients experiencing dyspnea, discomfort, or hearing loss that could prevent proper breath-holding should not be excluded from CT prior to TAVR. To decrease elderly patients' discomfort, MDCT evaluation prior to transcatheter aortic valve replacement (TAVR) may be performed on quiet breathing with no significant impact on the outcome. • Adhering to CT breathing commands can be challenging for patients with dyspnea, hearing impairment, agitation, or pulmonary diseases. • Free-breathing cardiac CT may be an alternative to breath-holding for patients unable to follow the breathing commands. • Wide-detector CT acquisition on free-breathing does not impair annulus measurements and prosthesis sizing in patients scheduled for TAVR.

Influence of a new motion correction algorithm (CardioCapture) on the correlation between heart rate and optimal reconstruction phase

PurposeTo investigate the effect of a new motion correction algorithm (CardioCapture) on the correlation between heart rate and optimal reconstruction phase by evaluating the impact of wide detector CT combined with CardioCapture on CCTA image quality. Materials and methodsAll cases were examined from April 2021 to September 2021. Two experienced radiologists scored these images on a four-point Likert scale. First, all images were divided into eight groups according to HR (at an interval of 5 bpm). The subjective score of images, the frequency of used CardioCapture, and the proportion of the diastolic reconstruction phase were compared in each group. Then, all cases were divided into two groups, one group was reconstructed using the automatic temporal reconstruction algorithm (Ephase) only, and the other group was reconstructed using the Ephase with the CardioCapture. The relationship between HR and the diastolic reconstruction phase was analyzed by the receiver operator characteristic curve (ROC). ResultThe data of 515 patients were studied. With the increase in HR, the subjective image score decreased, the frequency of CardioCapture increased, and the phase ratio of diastolic reconstruction decreased. When the HR was less than 70 bpm, the percentage of excellence image in each group surpassed 94.90%. The highest utilization rate of CardioCapture was 65.22%, and the lowest proportion of diastolic reconstruction was 72.46%. When 70 bpm < HR ≤ 75 bpm, the image excellence rate was 90.43%, the CardioCapture utilization rate was 82.05%, and the diastolic reconstruction rate was 56.41%.When 75 bpm < HR ≤ 80 bpm, the image excellence rate was 87.91%, the CardioCapture utilization rate was 80.65%, and the diastolic reconstruction was 6.45%.When the HR > 80 bpm, the image excellence rate was 80.00%, the CardioCapture utilization rate was 75.00%, and the diastolic reconstruction rate was 22.50%. The best cut-off point between HR and the diastolic reconstruction ROC curve in the groups without CardioCapture was 65 bpm, while that in groups with CardioCapture was 68 bpm. ConclusionThe CardioCapture can effectively improve the image quality of CCTA with high HR. By maintaining the HR below 68 bpm and utilizing the prospective ECG-gated narrow phase axial scan, it is possible to ensure optimal image quality and concurrently reduce radiation dose.

One-stop combined CT angiography of coronary and craniocervical arteries: recommended as the first examination for patients suspected of coronary or craniocervical artery disease.

To investigate the potential diagnostic value of one-stop combined CT angiography (CTA) as the first examination for patients suspected of coronary artery disease (CAD) or craniocervical artery disease (CCAD), and compare its clinical performance with two consecutive CTA scans. Patients with suspected but unconfirmed CAD or CCAD were prospectively enrolled and grouped randomly to undergo coronary and craniocervical CTA using the combined protocol (group 1) or the consecutive protocol (group 2). Diagnostic findings were evaluated for both the targeted and non-targeted regions. The objective image quality, overall scan time, radiation dose, and contrast medium dosage were compared between the two groups. Each group enrolled 65 patients. A substantial number of lesions were found in non-targeted regions, which was 44/65 (67.7%) by patients for group 1 and 41/65 (63.1%) for group 2, reiterating the necessity of extending the scan coverage. Specifically, lesions in non-targeted regions were detected more often for patients suspected of CCAD than for those suspected of CAD (71.4% vs 61.7%). With 21.5% (~51.1s) reduction of scan time and 21.8% (~20.8mL) less contrast medium as compared to the consecutive protocol, high-quality images were obtained by the combined protocol. One-stop combined CTA enables effective detection of lesions in non-targeted regions at a lower cost of scan time and contrast medium than two separate examinations and is thus worth taking as the first examination for patients suspected of CAD or CCAD. • Extending the scan range for coronary or craniocervical CTA has the potential to reveal lesions in non-targeted regions. • One-stop combined CTA as enabled on high-speed wide-detector CT delivers high-quality images at a lower cost of contrast medium and operational time than two consecutive CTA scans. • Patients with suspected but unconfirmed CAD or CCAD may benefit from the one-stop combined CTA in the first examination.

Accuracy and image quality of wide-detector revolution CT angiography combined with prospective ECG-triggered CT angiography in the diagnosis of congenital aortic arch anomalies in Chinese children.

To explore the accuracy and image quality of wide-detector revolution CT angiography combined with prospective ECG-triggered CT angiography in the diagnosis of congenital aortic arch anomalies in Chinese children. From January 2020 to July 2022, the clinical data of 57 children with congenital aortic arch anomalies confirmed by surgery were collected. All patients underwent CT angiography (CTA) with Revolution CT and transthoracic echocardiography (TTE) before the operation. The accuracy of CTA and TTE in the diagnosis of aortic arch anomalies was compared with the surgical results. The diagnostic sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of CTA and TTE for congenital aortic arch anomalies (including intracardiac and extracardiac structural abnormalities) were 92.2% and 85.5%, 99.4%, and 99.1%, 97.4% and 95.6%, 98.1% and 96.9%, and 97.2% and 95.2%, respectively. Regarding extracardiac structural malformations, the sensitivity of CTA was 100%, whereas that of TTE was 78.6% (P < 0.001). Regarding intracardiac structural malformations, the sensitivity of CTA was 84.5%, whereas that of TTE was 92.5% (P < 0.001). Regarding satisfaction with the images in aortic arch anomalies, surgeons noted that the CTA images were more useful for diagnosis and operation planning compared with TTE. Wide-detector revolution CT angiography combined with prospective ECG triggering can be routinely used to assess congenital aortic arch anomalies, providing adequate image quality and high diagnostic accuracy. However, limitations in the identification of intracardiac structural abnormalities are noted.

Intraindividual evaluation of effects of image filter function on image quality in coronary computed tomography angiography.

ObjectivesTo evaluate whether applying image filters (smooth 3D+ and edge-2) improves image quality in coronary CT angiography (CCTA).MethodsNinety patients (routine group) with suspected coronary artery diseases based on 16-cm wide coverage detector CT findings were retrospectively enrolled at a chest pain center from December 2019 to September 2021. Two image filters, smooth 3D+ and edge-2 available on the Advantage Workstation (AW) were subsequently applied to the images to generate the research group (SE group). Quantitative parameters, including CT value, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), image sharpness and image quality score, and diagnostic accuracy were compared between the two groups.ResultsA total of 900 segments from 270 coronary arteries in 90 patients were analyzed. SNR, CNR, and image sharpness for vessels and image quality scores in the SE group were significantly better than those in the routine group (all p < 0.001). The SE group showed a slightly higher negative predictive value (NPV) on the left anterior descending artery and right coronary artery (RCA) stenosis evaluations, as well as total NPV. The SE group also showed slightly higher sensitivity and accuracy than the routine group on RCA stenosis evaluation.ConclusionThe use of an image filter combining smooth 3D+ and edge-2 on an AW could improve the image quality of CCTA and increase radiologists' diagnostic confidence.

Imaging pediatric acute head trauma using 100-kVp low dose CT with adaptive statistical iterative reconstruction (ASIR-V) in single rotation on a 16 cm wide-detector CT.

To demonstrate the ability of achieving low dose and high-quality head CT images for children with acute head trauma using 100 kVp and adaptive statistical iterative reconstruction (ASIR-V) algorithm in single rotation on a 16 cm wide-detector system. We retrospectively analyzed the CT dose index (CTDI) and image quality of 104 children aged 0-6 years with acute head trauma (1 hour -3 days) in two groups: Group 1(n = 50) on a 256-row CT with single rotation at a reduced-dose of 100 kVp/240 mA and reconstructed using ASIR-V at 70%level; Group 2(n = 54) on a 64-row CT with multiple rotations at a standard dose of 120 kVp/ 180mA and reconstructed using a conventional filtered back-projection (FBP). Both groups used the 0.5 s/r axial scan mode. CT dose index (CTDI) and quantitative image quality measurements were compared using the Student t test; qualitative image quality comparison was carried out using Mann-Whitney rank test and the inter-reviewer agreement was evaluated using Kappa test. The exposure time was 0.5 s for Group 1 and 3.27±0.29 s for Group 2. The CTDI in Group 1 was 9.74±0.86mGy, 36.38%lower than the 15.31mGy in Group 2 (p < 0.001). Group 1 and Group 2 had similar artifact index (2.06±1.06 vs. 2.37±1.18) in the cerebellar hemispheres, and similar contrast-to-noise ratio (2.32±0.83 vs. 1.69±0.68), (1.47±0.72 vs. 1.10±0.43) respectively for cerebellum and thalamus (p > 0.05). Image quality was acceptable for diagnosis, and motion artifacts were reduced in Group 1 (p < 0.001). Single rotation CT with 100 kVp and 70%ASIR-V on 16 cm wide-detector CT reduces radiation dose and motion artifacts for children with acute head trauma without compromising diagnostic quality as compared with standard dose protocol. Thus, it provides a novel imaging method in management of pediatric acute head trauma.

The application value of multi-material artifact reduction technique in maxillofacial CT images of patients with metallic dental implants

Objective: To investigate the effect of multi-material artifact reduction (MMAR) technique on the maxillofacial CT images of patients with metallic dental implants. Methods: The data of 30 patients with metal denture implants who underwent maxillofacial wide-detector CT scans in the Department of Radiology of the First Affiliated Hospital of Zhengzhou University from March 2019 to February 2020 were retrospectively collected. The images of the lesion sites of patients were all affected by the metal implants artifacts. The 120 kV-like, virtual monoenergetic images (VMI) (70, 90, 110 keV), VMI (70, 90, 110 keV)+MMAR images were reconstructed at venous phase by energy spectrum scanning. A total of 7 image sequences were obtained for each patient. The CT value and noise value of the lesion and the longus capitis muscle on the same plane were measured, and the artifact index (AI) of lesion was calculated.Friedman test and Wilcoxon test were used to evaluate image quality objectively and subjectively. Results: There were significant differences in SD and AI among the 7 groups (χ2=133.800,P<0.001;χ2=92.147,P<0.001). The SD[10 (8, 12)] and AI [6 (5, 9)]of VMI 110 keV+M images were the lowest, but there were no significant differences in AI between VMI 110 keV+M and VMI 90 keV+M image (P= 0.271). The SD and AI of VMI+M group were lower than those in VMI group (all P<0.05). There was significant difference in image score among the 7 groups (χ 2 = 151.199, P<0.001). The image scores of VMI (70, 90, 110 keV)+M group were higher than those of VMI group (Z=-4.583, P = 0.000; Z=-3.742, P = 0.000; Z =-2.449, P = 0.014). The subjective score of VMI 90 keV+M [4 (3, 4)] was the highest, higher than those of other 6 groups (all P<0.05), in 26 out of 30 cases, lesions displayed clear contrast, and the artifacts eliminated completely. Conclusion: The MMAR technique of wide-detector CT might effectively remove the metallic dental implants artifacts and improve the image quality. VMI 90 keV+MMAR images could achieve the best artifact removal effect and good tissue contrast.

Feasibility of using a non-sedation protocol for evaluation of neonatal congenital heart disease by using a 16-cm wide-detector computed tomography with a low radiation dose: preliminary experience from a single pediatric medical center.

The aim of this study is to explore the feasibility of using a non-sedation protocol for the evaluation of neonatal congenital heart disease by using 16-cm wide-detector CT with a low radiation dose. Thirty-four neonates (group 1) were enrolled to undergo cardiac CT without sedation between August 2018 and March 2019. The control group (group 2) comprising 20 inpatient neonates was sedated. Cardiac CT was performed using 16-cm area detector 320-row CT with free breathing and prospective ECG-triggering scan mode. The examination completion time, radiation dose, and image quality were compared between the groups. The results of cardiac CT for patients in group 1 who underwent surgery were compared with surgical findings. Intergroup differences in body weight, age, examination completion time, radiation dose, and image quality evaluation were not significant. There was no significant difference in oxygen saturation before and after the examination in group 1. In all, 98 separate cardiovascular abnormalities in 27 group 1 patients were confirmed using surgical reports. The overall sensitivity, specificity, positive predictive value, and negative predictive value of cardiac CT were 94.90%, 100.0%, 100.0%, and 98.53%. The non-sedation protocol can be applied in neonates with congenital heart disease by using 16-cm wide-detector CT with a low radiation dose. Based on the image quality obtained, non-sedative examination did not extend the examination completion time and helped avoid the possible side effects of sedative drugs.

Comparison of axial scanning mode and traditional spiral scanning mode of 16 cm wide-detector CT in wrist, elbow, knee and ankle examination.

article: Comparison of axial scanning mode and traditional spiral scanning mode of 16 cm wide-detector CT in wrist, elbow, knee and ankle examination - Minerva Medica 2022 June;113(3):588-9 - Minerva Medica - Journals

Feasibility study of contrast injection scheme based on body mass and iodine flow rate in coronary computed tomography angiography with wide detector CT

Objective: To investigate the feasibility of coronary computed tomography angiography (CCTA) with the individualized contrast medium injection scheme based on body mass and iodine flow rate by using wide detector CT at 100 kV. Methods: From May 2018 to July 2018,270 patients with clinically suspected coronary artery disease underwent CCTA in TEDA International Cardiovascular Hospital. They were randomly divided into three groups, 90 cases in each group: group A was 0.5 ml/kg, group B was 0.6 ml/kg, the flow rate of contrast medium injection in group A and group B was (body mass×25 mg)/the concentration of contrast medium,group C was 0.8 ml/kg and the flow rate of contrast medium was 5 ml/s. Iohexol (iodine concentration 350 mgI/ml) was used in all three groups. The CT values of the aorta root in the three groups, the CT value of the middle segment of LAD and RCA, SNR、CNR、SD of the aortic root, subjective score of coronary artery and effective dose (ED) were compared. Results: There was no significant difference in CT value of aortic root, CT value of middle LAD and RCA, SNR、CNR、SD of the aortic root, subjective score of coronary artery among group A, group B and group C (all P>0.05). The flow rates of the three groups of contrast agents were statistically different (4.5±0.5 vs 4.5±0.5 vs 5, P=0.015), and there was no statistical difference between group A and group B (P>0.05) but lower than group C (P=0.015); the amount of contrast agent in the three groups was statistically different (32±3 vs 38±4 vs 53±7, P<0.001), group A<B Group<C group; there was no significant difference in ED between the three groups (1.5±0.5 vs 1.5±0.6 vs 1.3±0.6, P=0.613). Conclusions: CCTA imaging with a wide body detector based on a 0.5 ml/kg contrast agent dosage and a flow rate of ((body mass × 25)/350) ml/s individualized injection scheme can ensure the image quality while reducing the total amount of contrast agent and realizing individualized iodine flow rate.

Feasibility of wide detector CT perfusion imaging performed during routine staging and restaging of pancreatic ductal adenocarcinoma

To evaluate the feasibility of CT perfusion performed during routine multiphasecontrast-enhancedCTon a160mm wide-coverage256-slice scanner in patients with pancreatic ductal adenocarcinoma (PDAC). Fifty-seven patients had aCT perfusion acquisitionduringtheirroutine multiphase CT.Perfusion was performed 5 to 42.5s (15 passes at 2.5s intervals)after intravenous contrastadministration (4.2-5ml/s), followed by pancreatic parenchymal and portal venous phases for clinical interpretation. Perfusion maps were generated andblood flow (BF), blood volume (BV), and permeability surface area product (PS) for tumor and uninvolved pancreas were calculated using deconvolution algorithms and compared to existing similar publications. Radiationdose informationwas recorded and size-specific dose estimate (SSDE)was calculatedusing body dimensions. Diagnostic quality of standard images was unaffected by performing the perfusion acquisition. Average tumor center BF was 20.8 ± 12.1ml/100g/min, BV 2.5 ± 2.1ml/100g and PS 15.5 ± 39.4ml/100g/min. Average pancreas BF was 90.8 ± 50.2ml/100g/min, BV 11.9 ± 4.3ml/100g and PS 33.6 ± 27.7ml/100g/min. For the perfusion acquisition, meanSSDE was 57 ± 11mGy,CTDIvol43 ± 6mGyandDLP 685 ± 100mGy-cm. Adding a perfusion CT acquisition to standard pancreatic CTprotocol is feasible using a wide-detector 256-slice CT scanner and adds quantitative information while maintaining diagnostic quality of the standard of care examination.This novel protocol adds no time or cost to the examination and yields perfusion parameters that are comparable to existing literature using a separate dedicated perfusion protocol.

Achieving Low Radiation Dose in “One-Stop” Myocardial Computed Tomography Perfusion Imaging in Coronary Artery Disease Using 16-cm Wide Detector CT

To investigate the feasibility of "one-stop" myocardial computed tomography perfusion (CTP) imaging (combined anatomy, perfusion, and function) in coronary artery disease using 16-cm wide detector CT, compared to conventional coronary CT angiography (CCTA). 442 patients with suspected coronary artery disease were randomly divided into two groups. Patients in group A underwent "one-stop" CTP, whereas group B underwent conventional CCTA. Image quality of CT images was assessed. Radiation and contrast medium doses and scan time of the two groups were recorded. Group A was further divided into four subgroups according to the degree of coronary artery stenosis, for which transmural perfusion ratio (TPR) and left ventricular ejection fraction (LVEF) were measured. Scan time was 73.1 ± 7.3 (s) longer in group A than in group B with 11.7% reduction of radiation dose (p < 0.001) and no significant difference in image quality was noted. Significant differences regarding the minimum TPR (F = 24.657, p < 0.001) and LVEF (χ2 =36.98, p < 0.001) were observed among four subgroups. A negative correlation was found between the degree of coronary artery stenosis and TPR of the corresponding myocardial segments (r = -0.55, p < 0.001). Patients with moderate to severe arterial stenosis exhibited a decreased LVEF compared to those with normal coronary arteries (48.0% vs 56.5%, p < 0.001). Compared to conventional CCTA, our new developed "one-stop" CTP may provide more comprehensive information on myocardial perfusion, coronary artery stenosis, and LV cardiac function with reduced radiation and contrast medium doses.

The SnapShot Freeze Algorithm Improves Image Quality of Coronary Computed Tomography Angiography Using High-Resolution Wide-Detector CT

Objective: The aim of this study was to investigate the effect the motion-correction reconstruction algorithm SnapShot Freeze (SSF) on the diagnostic performance of coronary computed tomography angiography (CCTA) using high-resolution, wide-detector CT. Methods: CCTA was performed using an electrocardiography-triggered auto-gating protocol in 62 patients. All images were reconstructed using both standard algorithm and motioncorrection algorithm (SSF). According to the American Heart Association (AHA) guidelines for coronary angiography, the coronary artery was divided into 15 segments. The coronary artery segments were evaluated using a 4-point Likert scale to determine the image quality. Arteries with a score greater than 1 were further evaluated by two expert radiologists blinded to conditions. The diagnostic performance of SSF was compared in the patients with high heart rate (HR ≥ 75 beats per minute) compared to low HR (&lt; 75 beats per minute). Results: At the segmental level, the Likert score for segments 1–4 and 6–14 were higher in SSF compared to standard algorithm (p &lt; 0.05). The proportion of images that was improved by SSF was greater for the high HR systolic phase imaging (66.7%) than for the low HR diastolic phase imaging (34.3%, p &lt; 0.05). Conclusion: The SSF algorithm improves coronary CTA images acquired using a 256-row wide detector CT, compared to standard algorithm, particularly in patients with high HR.

Airway quantification using adaptive statistical iterative reconstruction-V on wide-detector low-dose CT: a validation study on lung specimen.

To evaluate the accuracy of airway quantification of adaptive statistical iterative reconstruction (ASIR)-V on low-dose CT using a human lung specimen. A lung specimen was scanned on Revolution CT with low-dose settings (20mAs, 40mAs and 60mAs/100kV) and standard-dose setting (100mAs/120kV). CT images were reconstructed using lung kernel with eleven ASIR-V levels from 0 to 100% with 10% interval. ASIR-V level from 0 to 100% with 10% interval was reconstructed on lung kernel. Wall area percentage (%WA) and wall thickness (WT) were measured. Radiation dose of 20mAs, 40mAs and 60mAs low-dose settings reduced by 87.6%, 75.2% and 62.8% compared to that on standard dose, respectively. Low-dose settings significantly decreased image SNR (p < 0.05) and increased noise (p < 0.001). ASIR-V level exponentially improved image SNR and linearly decreased image noise (all p < 0.001). The mean airway measurement ratios of low-dose to standard-dose were within 2% variation for %WA and within 3% variation for WT. Most %WA and WT values showed no obvious correlation with ASIR-V levels. ASIR-V showed to improve image quality in low radiation dose. However, low-dose settings and ASIR-V strength did not significantly influence airway quantification values, although variation in measurements slightly increased with dose reduction.

Application of a multi-material artifact reduction algorithm in a wide-detector CT in the evaluation of the portal venous angiography of postoperative TIPS and embolization

Objective: To assess the effect of monochromatic images and metal artifact reduction (MAR) on the image quality of spectral CT portal venous angiography in patients with operation of after the performing transjugular intrahepatic portosystemic stent shunt(TIPS) and embolization. Methods: From December 2017 to April 2018, the examination data of 28 patients with portal hypertension due to cirrhosis who underwent portal vein angiography 1 month after TIPS and embolization were prospectively collected. After spectral CT scanning in revolution CT, the monochromatic energy levels(60 keV, 120 keV), 60 keV + 120 keV, 120kV-like + 120 keV fused images combined with MAR algorithm were reconstructed. Quantitative parameters such as image artifact index (AI) and qualitative visual evaluation scores were recorded and compared. Results: The 120 keV monochromatic images showed the lowest AI value(30.8±8.5, 18.2±4.3) and highest metal artifacts reduction effect. The 60 keV monochromatic images showed the highest AI value (57.3±15.7, 32.1±7.9) and the lowest metal artifacts reduction effect. The AI value of 60 keV + 120 keV fused images was lower than that of 60 keV images(26.2%, 24.7%). The difference of AI value between each group was statistically significant(all P<0.05). The interobserver agreement in the subjective image scores was moderate with kappa value of 0.824. The overall image quality score of 60 keV + 120 keV fused image and the noise score of 120 kV-like+120 keV were higher than the remaining groups. The differences of the subjective scores among each group were statistically significant(all P<0.05). Conclusion: The spectral CT with MAR algorithm can effectively improve the image quality of portal vein angiography after the TIPS and embolization therapy and the 60 keV + 120 keV fused images can eliminate artifacts and ensure a clear display of blood vessels.

Free-breathing coronary CT angiography using 16-cm wide-detector for challenging patients: comparison with invasive coronary angiography

To investigate the superiority of free-breathing coronary computed tomography angiography (CCTA) with 16-cm wide-detector CT for challenging patients who cannot hold their breath. A total of 76 patients (62% with either heart rate >75 beats/min or arrhythmia) who were unable to breath-hold underwent both free-breathing CCTA and invasive coronary angiography (ICA) were included. Two reviewers evaluated coronary arteries on a per-segment, per-vessel, and per-patient basis for image quality using a four-point scale and stenosis degree. CCTA results were compared with ICA to calculate the diagnostic accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Out of 1,368 segments, 228 (16.7%) were <1.5 mm in diameter and were excluded. Thirty-two (2.3%) with calcification and 26 (1.9%) with motion artefacts were considered positive at CT. One thousand and eighty-two segments (79.1%) were evaluated both on CCTA and ICA, and 128 (11.8%) segments had ≥50% stenosis on ICA. The diagnostic accuracy, sensitivity, specificity, PPV, and NPV of CCTA were 90.8%, 88.3%, 91.1%, 57.1%, and 98.3% on a per-segment basis; 93.4%, 90.6%, 94.2%, 80.5% and 97.4% on a per-vessel basis; and 92.1%, 100%, 85%, 85.7% and 100% on a per-patient basis. For patients with high heart rates or arrhythmia, 81% (versus 79.1%) segments were evaluable, and the accuracy, sensitivity, specificity, PPV, and NPV were statistically the same as the entire study population. Free-breathing CCTA using 16-cm wide-detector CT has high accuracy compared to ICA for detecting coronary artery stenosis for challenging patients.

Contrast dose reduction with shortened injection durations in coronary CT angiography on 16-cm Wide-detector CT scanner.

To investigate the use of shortened contrast injection with late triggering in coronary CT angiography (CCTA) for decreasing contrast dose and maintaining image quality. 106 patients for CCTA on a 16-cm wide-detector CT were prospectively enrolled into groups A (n = 50) and B (n = 56) randomly. Patient weight-dependent contrast medium (Iopamiro, 370 mgI ml-1) at dose rate of 25 mgI/kg/s was used with 8 s and the standard 10 s injection time in groups A and B, respectively. CT values of the aortic sinus (AS), right coronary artery, left anterior descending and left circumflex at the proximal, middle and distal segments were measured and compared. Subjective image quality was evaluated and analyzed with Fisher exact test. Contrast dose, injection rate and enhancement duration (between the start of enhancement in AS and scan finish) were also compared. There was no difference in the injection rate and enhancement duration between the two groups (p > 0.05), while the total contrast dose in group A (36.2 ± 5.7 ml) was significantly lower than in group B (46.4 ± 6.3 ml) (p < 0.001). There was no difference for CT values in all major coronary vessels between the two groups and no difference in subjective image quality scores (all p > 0.05). It is feasible to shorten contrast injection to 8 s in CCTA on wide-detector CT systems to significantly reduce contrast dosage, maintain adequate enhancement and reduce contrast-related artifacts. (1) Coronary CT angiography (CCTA) scans with shortened contrast medium injection duration and late triggering are feasible with a 16-cm wide-detector CT system (2) Compared with the conventional CCTA with 10 s contrast injection duration, the new contrast injection protocol of using shortened injection duration (to 8 s) and late triggering reduces contrast dose to 36.2 ml, while maintaining adequate enhancement in vessels and reducing contrast-related artifacts.

Abdominal CT with low radiation dose in severe obese patients: Application of wide-detector helical CT combined with adaptive statistical iterative reconstruction-V (ASIR-V)

Objective To investigate the value of wide-detector helical CT combined with adaptive statistical iterative reconstruction-V (ASIR-V) in the low radiation dose CT examination of upper abdomen in obese patients. Methods In the first phantom experiment part, the optimal percentage of pre- and post-ASIR-V of abdominal scanning (120 kVp, NI=10 HU) were explored. The second human experiment was performed based on the phantom study, and our institutional review board approved this prospective study, each participant provided written informed consent. 87 obese patients (body mass index, BMI≥30 kg/m2) underwent contrast-enhanced abdominal CT scan were randomly divided into two scan protocols [protocol A: n=43, 120 kVp, detector coverage of 80 mm, 40% pre-ASIR-V (group A1) and combined with 60% post- ASIR-V (group A2) respectively; protocol B, n=44, 120 kVp, detector coverage of 40 mm, 40% ASIR (group B)]. Quantitative parameters [image noise and contrast-to-noise ratio (CNR)] and qualitative visual parameters (overall image quality as graded on a 5-point scale) were compared. Weighted effective dose (E) were assessed. Results The optimal percentage of pre- and post-ASIR-V of abdominal scanning were 40% and 60%, respectively. The effective radiation dose in protocol A [(4.55 ± 0.95) mSv] was decreased for 53% as compared with protocol B [(9.58 ± 2.04) mSv] (t=-14.773, P 0.05), and lower overall image quality scores(Z=-3.298--3.030, P<0.05) than group B. The overall image quality scores in group A were all greater than 3 point and met the clinical diagnostic level. Conclusions Compared with stand-detector helical CT in obese patients, the wide-detector helical CT combined with 40% pre-ASIR-V could reduce the radiation dose by 53%, and improve overall image quality by combining post- ASIR-V technique. Trial registration Chinese clinical trial registry, ChiCTR-DCD-15005932 Key words: Adaptive statistical iterative reconstruction-V; Wide-detector; Radiation dosage; Image quality; Obesity