Generation Dual-source CT Research Articles

The evolution of radiation dose over time: Measurement of a patient cohort undergoing whole-body examinations on three computer tomography generations

ObjectivesTo evaluate and compare the radiation dose and image quality of whole-body-CT (WBCT) performed on the 3rd-generation dual-source-CT (DSCT) with 2nd-generation DSCT and 64-slices-Single-Source-CT (SSCT) in a large patient cohort. Material and methodsUsing a monitoring and tracking software 1451, 747 and 1861 patients scanned with a one-spiral-thorax-abdomen-pelvis-CT-examination on a 3rd-, 2nd-generation DSCT and SSCT, respectively, were extracted from the PACS server. For the intra-individual analysis, 203 patients on the 3rd-generation DSCT were identified. Out of those 203 patients, 155 had the same examination on the 2nd-generation DSCT, 91 patients had the same examination on the SSCT and 43 patients had an examination on all three CT-generations. Automatic tube current modulation was active on all three CT-generations, whereas automatic tube voltage selection was only available on both DSCT-generations. Dose was recorded by the size-specific-dose-estimate-method (SSDE); signal-to-noise-ratio (SNR) and contrast-to-noise-ratio (CNR) were calculated placing a ROI on the ascending aorta/liver and the subcutaneous adipose tissue at comparable level. Image quality of axillary and mediastinal lymph nodes and adrenal glands was assessed by two experienced radiologists. ResultsSubjective image quality was excellent throughout all three CT-generations (p=0.38–0.98). Quantitative image quality in both DSCT generations was superior to SSCT (p<0.001). SNR and CNR in the liver parenchyma were superior in the 3rd-generation DSCT compared to the 2nd generation DSCT (p<0.001), whereas there was no difference in the aorta. In the inter-individual analysis, CTDIvol was lower by 26.9% and 44.3% in the 3rd-generation DSCT, when compared to the 2nd-generation DSCT and SSCT, respectively; SSDE was lower by 31.5% and 51% in the 3rd-generation DSCT, when compared to the 2nd-generation DSCT and SSCT, respectively. In the intra-individual comparison CTDIVol in the 3rd-generation DSCT was lower by 33% and 45%, when compared to the 2nd-gneration DSCT and the SSCT, respectively. Consequently, SSDE in the 3rd-generation DSCT was lower by 29% and by 43% when compared to the 2nd-generation DSCT and SSCT, respectively. ConclusionState-of-the-art CT-equipment substantially reduce radiation dose without affecting image quality.

Cost-effectiveness analysis of new generation coronary CT scanners for difficult-to-image patients.

New generation dual-source coronary CT (NGCCT) scanners with more than 64 slices were evaluated for patients with (known) or suspected of coronary artery disease (CAD) who are difficult to image: obese, coronary calcium score >400, arrhythmias, previous revascularization, heart rate >65 beats per minute, and intolerance of betablocker. A cost-effectiveness analysis of NGCCT compared with invasive coronary angiography (ICA) was performed for these difficult-to-image patients for England and Wales. Five models (diagnostic decision model, four Markov models for CAD progression, stroke, radiation and general population) were integrated to estimate the cost-effectiveness of NGCCT for both suspected and known CAD populations. The lifetime costs and effects from the National Health Service perspective were estimated for three strategies: (1) patients diagnosed using ICA, (2) using NGCCT, and (3) patients diagnosed using a combination of NGCCT and, if positive, followed by ICA. In the suspected population, the strategy where patients only undergo a NGCCT is a cost-effective option at accepted cost-effectiveness thresholds. The strategy of using NGCCT in combination with ICA is the most favourable strategy for patients with known CAD. The most influential factors behind these results are the percentage of patients being misclassified (a function of both diagnostic accuracy and the prior likelihood), the complication rates of the procedures, and the cost price of a NGCCT scan. The use of NGCCT might be considered cost-effective in both populations since it is cost-saving compared to ICA and generates similar effects.

Impact of iterative metal artifact reduction on diagnostic image quality in patients with dental hardware.

Background Metal artifacts often impair diagnostic accuracy in computed tomography (CT) imaging. Therefore, effective and workflow implemented metal artifact reduction algorithms are crucial to gain higher diagnostic image quality in patients with metallic hardware. Purpose To assess the clinical performance of a novel iterative metal artifact reduction (iMAR) algorithm for CT in patients with dental fillings. Material and Methods Thirty consecutive patients scheduled for CT imaging and dental fillings were included in the analysis. All patients underwent CT imaging using a second generation dual-source CT scanner (120 kV single-energy; 100/Sn140 kV in dual-energy, 219 mAs, gantry rotation time 0.28-1/s, collimation 0.6 mm) as part of their clinical work-up. Post-processing included standard kernel (B49) and an iterative MAR algorithm. Image quality and diagnostic value were assessed qualitatively (Likert scale) and quantitatively (HU ± SD) by two reviewers independently. Results All 30 patients were included in the analysis, with equal reconstruction times for iMAR and standard reconstruction (17 s ± 0.5 vs. 19 s ± 0.5; P > 0.05). Visual image quality was significantly higher for iMAR as compared with standard reconstruction (3.8 ± 0.5 vs. 2.6 ± 0.5; P < 0.0001, respectively) and showed improved evaluation of adjacent anatomical structures. Similarly, HU-based measurements of degree of artifacts were significantly lower in the iMAR reconstructions as compared with the standard reconstruction (0.9 ± 1.6 vs. -20 ± 47; P < 0.05, respectively). Conclusion The tested iterative, raw-data based reconstruction MAR algorithm allows for a significant reduction of metal artifacts and improved evaluation of adjacent anatomical structures in the head and neck area in patients with dental hardware.

Improved visual delineation of the intimal flap in Stanford type A and B dissections at 3rd generation dual-source high-pitch CT angiography.

Evaluation of the intimal flap visibility comparing 2nd and 3rd generation dual-source high-pitch CT. Twenty-five consecutive patients with aortic dissection underwent CT angiography on a second and third generation dual-source CT scanner using prospective ECG-gated high-pitch dual-source CT acquisition mode. Contrast material, saline flush and flow rate were kept equal for optimum comparability. The visibility of the intimal flap as well as the delineation of the different vascular structures was evaluated. In 3rd generation dual-source high-pitch CT we could show a significant improvement of intimal flap visibility in aortic dissection. Especially, the far end of the dissection membrane could be better evaluated in 3rd generation high-pitch CT, reaching statistical significance (P<0.01). 3rd Generation high-pitch CT angiography shows a better delineation of the aortic intimal flap in a small patient cohort, especially in the far ends of the dissection membrane. This might be due to higher tube power in this CT generation. However, to generalise these findings larger trials are needed.

High pitch third generation dual-source CT: Coronary and cardiac visualization on routine chest CT

BackgroundChest CT scans are frequently performed in radiology departments but have not previously contained detailed depiction of cardiac structures. ObjectivesTo evaluate myocardial and coronary visualization on high-pitch non-gated CT of the chest using 3rd generation dual-source computed tomography (CT). MethodsCardiac anatomy of patients who had 3rd generation, non-gated high pitch contrast enhanced chest CT and who also had prior conventional (low pitch) chest CT as part of a chest abdomen pelvis exam was evaluated. Cardiac image features were scored by reviewers blinded to diagnosis and pitch. Paired analysis was performed. Results3862 coronary segments and 2220 cardiac structures were evaluated by two readers in 222 CT scans. Most patients (97.2%) had chest CT for oncologic evaluation. The median pitch was 2.34 (IQR 2.05, 2.65) in high pitch and 0.8 (IQR 0.8, 0.8) in low pitch scans (p < 0.001). High pitch CT showed higher image visualization scores for all cardiovascular structures compared with conventional pitch scans (p < 0.0001). Coronary arteries were visualized in 9 coronary segments per exam in high pitch scans versus 2 segments for conventional pitch (p < 0.0001). Radiation exposure was lower in the high pitch group compared with the conventional pitch group (median CTDIvol 10.83 vs. 12.36 mGy and DLP 790 vs. 827 mGycm respectively, p < 0.01 for both) with comparable image noise (p = 0.43). ConclusionMyocardial structure and coronary arteries are frequently visualized on non-gated 3rd generation chest CT. These results raise the question of whether the heart and coronary arteries should be routinely interpreted on routine chest CT that is otherwise obtained for non-cardiac indications.

--LAA Occluder View for post-implantation Evaluation (LOVE)--standardized imaging proposal evaluating implanted left atrial appendage occlusion devices by cardiac computed tomography.

BackgroundA standardized imaging proposal evaluating implanted left atrial appendage (LAA) occlusion devices by cardiac computed tomography angiography (cCTA) has never been investigated.MethodscCTA datasets were acquired on a 3rd generation dual-source CT system and reconstructed with a slice thickness of 0.5 mm. An interdisciplinary evaluation was performed by two interventional cardiologists and one radiologist on a 3D multi-planar workstation. A standardized multi-planar reconstruction algorithm was developed in order to assess relevant clinical aspects of implanted LAA occlusion devices being outlined within a pictorial essay.ResultsThe following clinical aspects of implanted LAA occlusion devices were evaluated within the most appropriate cCTA multi-planar reconstruction: (1) topography to neighboring structures, (2) peri-device leaks, (3) coverage of LAA lobes, (4) indirect signs of neo-endothelialization. These are illustrated within concise CT imaging examples emphasizing the potential value of the proposed cCTA imaging algorithm: Starting from anatomical cCTA planes and stepwise angulation planes perpendicular to the base of the LAA devices generates an optimal LAA Occluder View for post-implantation Evaluation (LOVE). Aligned true axial, sagittal and coronal LOVE planes offer a standardized and detailed evaluation of LAA occlusion devices after percutaneous implantation.ConclusionsThis pictorial essay presents a standardized imaging proposal by cCTA using multi-planar reconstructions that enables systematical follow-up and comparison of patients after LAA occlusion device implantation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12880-016-0127-y) contains supplementary material, which is available to authorized users.

Effect of automated tube voltage selection, integrated circuit detector and advanced iterative reconstruction on radiation dose and image quality of 3rd generation dual-source aortic CT angiography: An intra-individual comparison

PurposeTo compare, on an intra-individual basis, the effect of automated tube voltage selection (ATVS), integrated circuit detector and advanced iterative reconstruction on radiation dose and image quality of aortic CTA studies using 2nd and 3rd generation dual-source CT (DSCT). Material and methodsWe retrospectively evaluated 32 patients who had undergone CTA of the entire aorta with both 2nd generation DSCT at 120kV using filtered back projection (FBP) (protocol 1) and 3rd generation DSCT using ATVS, an integrated circuit detector and advanced iterative reconstruction (protocol 2). Contrast-to-noise ratio (CNR) was calculated. Image quality was subjectively evaluated using a five-point scale. Radiation dose parameters were recorded. ResultsAll studies were considered of diagnostic image quality. CNR was significantly higher with protocol 2 (15.0±5.2 vs 11.0±4.2; p<.0001). Subjective image quality analysis revealed no significant differences for evaluation of attenuation (p=0.08501) but image noise was rated significantly lower with protocol 2 (p=0.0005). Mean tube voltage and effective dose were 94.7±14.1kV and 6.7±3.9mSv with protocol 2; 120±0kV and 11.5±5.2mSv with protocol 1 (p<0.0001, respectively). ConclusionAortic CTA performed with 3rd generation DSCT, ATVS, integrated circuit detector, and advanced iterative reconstruction allow a substantial reduction of radiation exposure while improving image quality in comparison to 120kV imaging with FBP.

High-Pitch CT Pulmonary Angiography in Third Generation Dual-Source CT: Image Quality in an Unselected Patient Population.

ObjectivesTo investigate the feasibility of high-pitch CT pulmonary angiography (CTPA) in 3rd generation dual-source CT (DSCT) in unselected patients.MethodsForty-seven patients with suspected pulmonary embolism underwent high-pitch CTPA on a 3rd generation dual-source CT scanner. CT dose index (CTDIvol) and dose length product (DLP) were obtained. Objective image quality was analyzed by calculating signal-to-noise-ratio (SNR) and contrast-to-noise ratio (CNR). Subjective image quality on the central, lobar, segmental and subsegmental level was rated by two experienced radiologists.ResultsMedian CTDI was 8.1 mGy and median DLP was 274 mGy*cm. Median SNR was 32.9 in the central and 31.9 in the segmental pulmonary arteries. CNR was 29.2 in the central and 28.2 in the segmental pulmonary arteries. Median image quality was “excellent” in central and lobar arteries and “good” in subsegmental arteries according to both readers. Segmental arteries varied between “excellent” and “good”. Image quality was non-diagnostic in one case (2%), beginning in the lobar arteries. Thirteen patients (28%) showed minor motion artifacts.ConclusionsIn third-generation dual-source CT, high-pitch CTPA is feasible for unselected patients. It yields excellent image quality with minimal motion artifacts. However, compared to standard-pitch cohorts, no distinct decrease in radiation dose was observed.

Evaluation of conventional imaging performance in a research whole-body CT system with a photon-counting detector array

This study evaluated the conventional imaging performance of a research whole-body photon-counting CT system and investigated its feasibility for imaging using clinically realistic levels of x-ray photon flux. This research system was built on the platform of a 2nd generation dual-source CT system: one source coupled to an energy integrating detector (EID) and the other coupled to a photon-counting detector (PCD). Phantom studies were conducted to measure CT number accuracy and uniformity for water, CT number energy dependency for high-Z materials, spatial resolution, noise, and contrast-to-noise ratio. The results from the EID and PCD subsystems were compared. The impact of high photon flux, such as pulse pile-up, was assessed by studying the noise-to-tube-current relationship using a neonate water phantom and high x-ray photon flux. Finally, clinical feasibility of the PCD subsystem was investigated using anthropomorphic phantoms, a cadaveric head, and a whole-body cadaver, which were scanned at dose levels equivalent to or higher than those used clinically. Phantom measurements demonstrated that the PCD subsystem provided comparable image quality to the EID subsystem, except that the PCD subsystem provided slightly better longitudinal spatial resolution and about 25% improvement in contrast-to-noise ratio for iodine. The impact of high photon flux was found to be negligible for the PCD subsystem: only subtle high-flux effects were noticed for tube currents higher than 300 mA in images of the neonate water phantom. Results of the anthropomorphic phantom and cadaver scans demonstrated comparable image quality between the EID and PCD subsystems. There were no noticeable ring, streaking, or cupping/capping artifacts in the PCD images. In addition, the PCD subsystem provided spectral information. Our experiments demonstrated that the research whole-body photon-counting CT system is capable of providing clinical image quality at clinically realistic levels of x-ray photon flux.

Evaluation of individually body weight adapted contrast media injection in coronary CT-angiography

ObjectivesContrast media (CM) injection protocols should be customized to the individual patient. Aim of this study was to determine if software tailored CM injections result in diagnostic enhancement of the coronary arteries in computed tomography angiography (CTA) and if attenuation values were comparable between different weight categories. Materials and methods265 consecutive patients referred for routine coronary CTA were scanned on a 2nd generation dual-source CT. Group 1 (n=141) received an individual CM bolus based on weight categories (39–59kg; 60–74kg; 75–94kg; 95–109kg) and scan duration (‘high-pitch: 1s; “dual-step prospective triggering”: 7s), as determined by contrast injection software (Certegra™ P3T, Bayer, Berlin, Germany). Group 2 (n=124) received a standard fixed CM bolus; Iopromide 300mgI/ml; volume: 75ml; flow rate: 7.2ml/s. Contrast enhancement was measured in all proximal and distal coronary segments. Subjective and objective image quality was evaluated. Statistical analysis was performed using SPSS (IBM, version 20.0). ResultsFor group 1, mean attenuation values of all segments were diagnostic (>325HU) without statistical significant differences between different weight categories (p>0.17), proximal vs. distal: 449±65–373±58HU (39–59kg); 443±69–367±81HU (60–74kg); 427±59–370±61HU (75–94kg); 427±73–347±61HU (95–109kg). Mean CM volumes were: 55±6ml (39–59kg); 61±7ml (60–74kg); 71±8ml (75–94kg); 84±9ml (95–109kg). For group 2, mean attenuation values were not all diagnostic with differences between weight categories (p<0.01), proximal vs. distal: 611±142–408±69HU (39–59kg); 562±135–389±98HU (60–74kg); 481±83–329±81HU (75–94kg); 420±73–305±35HU (95–109kg). Comparable image noise and image quality were found between groups (p≥0.330). ConclusionsIndividually tailored CM injection protocols yield diagnostic attenuation and a more homogeneous enhancement pattern between different weight groups. CM volumes could be reduced for the majority of patients utilizing individualized CM bolus application.

Low dose time-resolved CT-angiography in pediatric patients with venous malformations using 3rd generation dual-source CT: Initial experience

ObjectivesTo prospectively evaluate the diagnostic value and radiation dose of time-resolved CT-Angiography (4D-CTA) in pediatric patients with venous malformations using 3rd generation dual-source CT (DSCT) at 70kVp tube voltage. MethodsBetween November 2014 and August 2015, seven children (2 male, 5 female; median age, 9 years; range 3–12 years) with suspected peripheral, non-cerebral, venous malformations were included in this feasibility study and underwent US, MRI and 4D-CTA. All three imaging modalities were analyzed and compared individually by an experienced interventional radiologist and a pediatric surgeon using a 5-point Likert scale, with regard to diagnosis of the vascular anomaly, additional information like presence of thrombophlebitis and lesion extension, flow dynamics, localization, volume and significance for treatment planning. For quantitative statistical analysis, an unifactorial analysis of variance was performed for every parameter and all three imaging modalities. Radiation dose values as expressed by the volume CT dose index (CTDIvol) and dose-length product (DLP) were recorded for of all patients. ResultsThree out of six patients had isolated type I venous malformations without peripheral venous drainage which could be demonstrated on MRI and CT. In two out of six patients a type II venous malformation with drainage into normal veins was diagnosed. In one case, 4D-CT was the only imaging modality that revealed a slow-flow venous malformation with shunting supply by a hypodynamic arterial feeder. Treatment planning4D-CTA was rated as the best imaging modality for treatment planning with agreement between radiologist and surgeon, especially with respect to the hemodynamics of the venous malformation. Conclusions4D-CTA at 70kVp is a fast imaging modality that provides comprehensive diagnostic information of venous malformations in pediatric patients and is very valuable for therapy planning. Radiation dose of 4D-CTA must be weighted against the diagnostic information as well as the potential risk for sedation and contrast administration during MRI.

Comparison of organ-specific-radiation dose levels between 70 kVp perfusion CT and standard tri-phasic liver CT in patients with hepatocellular carcinoma using a Monte-Carlo-Simulation-based analysis platform

PurposeThe aim of this study was to systematically compare organ-specific-radiation dose levels between a radiation dose optimized perfusion CT (dVPCT) protocol of the liver and a tri-phasic standard CT protocol of the liver using a Monte-Carlo-Simulation-based analysis platform. Methods and materialsThe complete CT data of 52 patients (41 males; mean age 65±12) with suspected HCC that underwent dVPCT examinations on a 3rd generation dual-source CT (Somatom Force, Siemens) with a dose optimized tube voltage of 70kVp or 80kVp were exported to an analysis platform (Radimetrics, Bayer). The dVPCT studies were matched with a reference group of 50 patients (35 males; mean age 65±14) that underwent standard tri-phasic CT (sCT) examinations of the liver with 130kVp using the calculated water-equivalent-diameter of the patients. The analysis platform was used for the calculation of the organ-specific effective dose (ED) as well as global radiation-dose parameters (ICRP103). ResultsThe organ-specific ED of the dVPCT protocol was statistically significantly lower when compared to the sCT in 14 of 21, and noninferior in a total of 18 of 21 examined items (all p<0.05). The EDs of the dVPCT examinations were especially in the dose sensitive organs such as the red marrow (17.3mSv vs 24.6mSv, p=<0.0001) and the liver (33.3mSv vs 46.9mSv, p=0.0003) lower when compared to the sCT. ConclusionOur results suggest that dVPCT performed at 70 or 80kVp compares favorably to sCT performed with 130kVp with regard to effective organ dose levels, especially in dose sensitive organs, while providing additional functional information which is of paramount importance in patients undergoing novel targeted therapies.

Intra-individual diagnostic image quality and organ-specific-radiation dose comparison between spiral cCT with iterative image reconstruction and z-axis automated tube current modulation and sequential cCT

ObjectivesTo prospectively evaluate image quality and organ-specific-radiation dose of spiral cranial CT (cCT) combined with automated tube current modulation (ATCM) and iterative image reconstruction (IR) in comparison to sequential tilted cCT reconstructed with filtered back projection (FBP) without ATCM. Methods31 patients with a previous performed tilted non-contrast enhanced sequential cCT aquisition on a 4-slice CT system with only FBP reconstruction and no ATCM were prospectively enrolled in this study for a clinical indicated cCT scan. All spiral cCT examinations were performed on a 3rd generation dual-source CT system using ATCM in z-axis direction. Images were reconstructed using both, FBP and IR (level 1–5). A Monte-Carlo-simulation-based analysis was used to compare organ-specific-radiation dose. Subjective image quality for various anatomic structures was evaluated using a 4-point Likert-scale and objective image quality was evaluated by comparing signal-to-noise ratios (SNR). ResultsSpiral cCT led to a significantly lower (p<0.05) organ-specific-radiation dose in all targets including eye lense. Subjective image quality of spiral cCT datasets with an IR reconstruction level 5 was rated significantly higher compared to the sequential cCT acquisitions (p<0.0001). Consecutive mean SNR was significantly higher in all spiral datasets (FBP, IR 1–5) when compared to sequential cCT with a mean SNR improvement of 44.77% (p<0.0001). ConclusionsSpiral cCT combined with ATCM and IR allows for significant-radiation dose reduction including a reduce eye lens organ-dose when compared to a tilted sequential cCT while improving subjective and objective image quality.

Leukocyte DNA damage after reduced and conventional absorbed radiation doses using 3rd generation dual-source CT technology

PurposeComputed tomography (CT) scans are an important source of ionizing irradiation (IR) in medicine that can induce a variety of DNA damage in human tissues. With technological improvements CT scans at reduced absorbed doses became feasible presumably lowering genotoxic side effects. Materials and methodsFor measuring DNA damage we performed γH2AX foci microscopy in peripheral blood mononuclear cells (PBMC) after exposure to reduced and conventional absorbed radiation doses using 3rd generation dual-source CT (DSCT) technology. ResultsCT scans performed at reduced absorbed doses of 3mGy induced significant lower levels (p<0.0001) of DNA damage (0.05 focus per cell±0.01 [mean±standard error of mean]) at 5min after IR compared to conventional absorbed doses of 15mGy (0.30 focus per cell±0.03). With ongoing DNA repair background γH2AX foci levels (0.05 focus per cell) were approached at 24h after CT with both protocols. ConclusionOur results provide evidence that reduced absorbed doses mediated by adjusted tube current in 3rd generation DSCT induce lower levels of DNA damage in PBMC compared to conventional absorbed doses suggesting a lower genotoxic risk for state-of-the-art tube current reduced CT protocols.

Coronary CT angiography in obese patients using 3(rd) generation dual-source CT: effect of body mass index on image quality.

To evaluate the image quality of coronary CT angiography (CCTA) in obese patients using a 3(rd) generation, dual-source CT scanner. We retrospectively evaluated 102 overweight and obese patients who had undergone CCTA. Studies were performed with 3(rd) generation dual-source CT, prospectively ECG-triggered acquisition at 120kV, and automated tube current modulation. Advanced modeled iterative reconstruction was used. Patients were divided into three BMI groups: 1)25-29.9kg/m(2); 2)30-39.9kg/m(2); 3) ≥ 40kg/m(2). Vascular attenuation in the coronary arteries was measured. Contrast-to-noise ratio (CNR) was calculated. Image quality was subjectively evaluated using five-point scales. Image quality was considered diagnostic in 97.6% of examinations. CNR was consistently adequate in all groups but decreased for groups 2 and 3 in comparison to group 1 as well as for group 3 compared to group 2 (p = 0.001, respectively). Subjective image quality was significantly higher in group 1 compared to group 3 (attenuation proximal: 4.8 ± 0.4 vs. 4.4 ± 0.6, p = 0.011; attenuation distal: 4.5 ± 0.7 vs. 4.0 ± 0.8, p = 0.019; noise: 4.7 ± 0.6 vs. 3.8 ± 0.7, p < 0.001). The mean effective dose was 9.5 ± 3.9mSv for group 1, 11.4 ± 4.7mSv for group 2 and 14.0 ± 6.4mSv for group 3. Diagnostic image quality can be routinely obtained at CCTA in obese patients with 3(rd) generation DSCT at 120kV. • Diagnostic CCTA can be routinely performed in obese patients with 3 (rd) generation DSCT. • 120-kV tube voltage allows diagnostic image quality in patients with BMI > 40kg/m (2) . • 80-ml contrast medium can be administered without significant decline in vascular attenuation.

Ultra-high pitch chest computed tomography at 70 kVp tube voltage in an anthropomorphic pediatric phantom and non-sedated pediatric patients: Initial experience with 3rd generation dual-source CT

PurposeMinimizing radiation dose while at the same time preserving image quality is of particular importance in pediatric chest CT. Very recently, CT imaging with a tube voltage of 70 kVp has become clinically available. However, image noise is inversely proportional to the tube voltage. We aimed to investigate radiation dose and image quality of pediatric chest CT performed at 70 kVp in an anthropomorphic pediatric phantom as well as in clinical patients. Methods and MaterialsAn anthropomorphic pediatric phantom, which resembles a one-year-old child in physiognomy, was scanned on the 3rd generation dual-source CT (DSCT) system at 70 kVp and 80 kVp and a fixed ultra low tube-current of 8 mAs to solely evaluate the impact of lowering tube voltage. After the phantom measurements, 18 pediatric patients (mean 29.5 months; range 1-91 months; 21 examinations) underwent 3.2 high-pitch chest CT on the same DSCT system at 70 kVp tube voltage without any sedation. Radiation dose and presence of motion artifacts was compared to a retrospectively identified patient cohort examined at 80 kVp on a 16-slice single-source-CT (SSCT; n=15; 14/15 with sedation; mean 30.7 months; range 0-96 months; pitch=1.5) or on a 2nd generation DSCT without any sedation (n=6; mean 32.8 months; range 4-61 months; pitch=3.2). ResultsRadiation dose in the phantom scans was reduced by approximately 40% when using a tube voltage of 70 kVp instead of 80 kVp. In the pediatric patient group examined at 70 kVp age-specific effective dose (ED; mean 0.5±0.2 mSv) was significantly lower when compared to the retrospective cohort scanned at 80 kVp on the 16-slice-SSCT (mean ED: 1.0±0.3 mSv; p<0.0001) and also considerably lower when compared to the cohort scanned at 80 kVp on the 2nd generation DSCT (mean ED: 0.9±0.5 mSv). None of the prospective, sedation-free CT examinations showed any motion artifacts whereas 13/15 examinations of the retrospective patient cohort scanned at 80 kVp with a pitch of 1.5 showed motion artifacts. Conclusion3.2 high-pitch chest CT performed with 70 kVp significantly reduces radiation dose when compared to 80 kVp while at the same time provides good image quality without any motion artifacts even without sedation.

Size dependence of inherent image quality of a 2nd generation dual source CT scanner

The fast developing CT technologies have complicated the protocol optimization process. Since there are increasing numbers of free parameters that can be adjusted, it is imperative to know exactly how these parameters affect the image quality. This paper examines the effect of varying dose level, tube voltage, reconstruction methods and the AEC function on the CT image quality across different sizes. A size varying phantom, consisting of five cylindrical tiers, was used. To assess the image quality, task transfer function (TTF), noise power spectra (NPS), contrast, and detectability index was computed and compared across sizes. It was found that from small to large size, detectability increased more as the dose increased. When the CTDIvol increased from 0.7 to 22.6 mGy, the detectability for the smallest size section increased by four fold but increased by eight fold for the largest section. Low tube voltage exhibited superior detectability and contrast for all sections, especially for the small size sections, where detectability doubled for the smallest section when tube voltage decreased from 120 kV to 80 kV. TTF curves showed considerable dependence on size, but more pronounced dependence on reconstruction techniques. In conclusion, small size phantoms were affected very differently from large size phantoms by dose levels, reconstruction methods, and tube voltage selection. Low tube voltage and iterative reconstruction technique can deliver superior image quality for small patients. Due to beam hardening and substantially increased noise at low tube voltage for large patients, high tube voltage is still recommended for large patients to retain image quality.

Approaches to ultra-low radiation dose coronary artery calcium scoring based on 3rd generation dual-source CT: A phantom study

ObjectivesTo investigate to what extent 3rd generation dual-source computed tomography (DSCT) can reduce radiation dose in coronary artery calcium scoring. MethodsImage acquisition was performed using a stationary calcification phantom. Prospectively electrocardiogram (ECG)-triggered 120kV sequential, and 120 and Sn100kV ultra-high pitch (UHP) acquisitions were performed with different tube currents (80, 60, 40, 20mA). Images were reconstructed using filtered back projection (FBP) and 3rd generation iterative reconstruction (IR). Contrast-to-noise ratio (CNR), Agatston score, calcium volume, and radiation dose were assessed. For statistical analysis Friedman tests and Wilcoxon rank sum tests were used. ResultsEven at reduced tube currents, the three acquisition techniques did not show significant differences in Agatston score (p=0.4) or calcium volume (p=0.08) with FBP reconstruction. Calcium volumes were significantly lower for 3rd generation IR compared to FBP reconstructions (p<0.01). CTDIvol for the 120kV sequential, 120 and Sn100kV UHP acquisitions at 80 and 20mA were 1.2–0.37, 0.48–0.17, and 0.07–0.02 mGy, respectively. Conclusion3rd generation DSCT enabled a reduction of tube current in both the sequential and UHP acquisitions without significantly affecting coronary calcium scoring. Tin filtered 100kV scanning may allow accurate quantification of calcium score without correction of the HU threshold.

Impact of an advanced image-based monoenergetic reconstruction algorithm on coronary stent visualization using third generation dual-source dual-energy CT: a phantom study

To evaluate the impact of an advanced monoenergetic (ME) reconstruction algorithm on CT coronary stent imaging in a phantom model. Three stents with lumen diameters of 2.25, 3.0 and 3.5mm were examined with a third-generation dual-source dual-energy CT (DECT). Tube potential was set at 90/Sn150kV for DE and 70, 90 or 120kV for single-energy (SE) acquisitions and advanced modelled iterative reconstruction was used. Overall, 23 reconstructions were evaluated for each stent including three SE acquisitions and ten advanced and standard ME images with virtual photon energies from 40 to 130keV, respectively. In-stent luminal diameter was measured and compared to nominal lumen diameter to determine stent lumen visibility. Contrast-to-noise ratio was calculated. Advanced ME reconstructions substantially increased lumen visibility in comparison to SE for stents ≤3mm. 130keV images produced the best mean lumen visibility: 86% for the 2.25mm stent (82% for standard ME and 64% for SE) and 82% for the 3.0mm stent (77% for standard ME and 69% for SE). Mean DLP for SE 120kV and DE acquisitions were 114.4 ± 9.8 and 58.9 ± 2.2mGy × cm, respectively. DECT with advanced ME reconstructions improves the in-lumen visibility of small stents in comparison with standard ME and SE imaging. • An advanced image-based monoenergetic reconstruction algorithm improves lumen visualization in stents ≤3.0mm. • Application of high keV reconstructions significantly improves in-stent lumen visualization. • DECT acquisition resulted in49 % radiation dose reduction compared with 120kV SE.

Coronary CT angiography using low concentrated contrast media injected with high flow rates: Feasible in clinical practice

PurposeAim of this study was to test the hypothesis that peak injection pressures and image quality using low concentrated contrast media (CM) (240mg/mL) injected with high flow rates will be comparable to a standard injection protocol (CM: 300mg/mL) in coronary computed tomographic angiography (CCTA). Material and methodsOne hundred consecutive patients were scanned on a 2nd generation dual-source CT scanner. Group 1 (n=50) received prewarmed Iopromide 240mg/mL at an injection rate of 9mL/s, followed by a saline chaser. Group 2 (n=50) received the standard injection protocol: prewarmed Iopromide 300mg/mL; flow rate: 7.2mL/s. For both protocols, the iodine delivery rate (IDR, 2.16gI/s) and the total iodine load (22.5gI) were kept identical. Injection pressure (psi) was continuously monitored by a data acquisition program. Contrast enhancement was measured in the thoracic aorta and all proximal and distal coronary segments. Subjective and objective image quality was evaluated between both groups. ResultsNo significant differences in peak injection pressures were found between both CM groups (121±5.6psi vs. 120±5.3psi, p=0.54). Flow rates of 9mL/s were safely injected without any complications. No significant differences in contrast-to-noise ratio, signal-to-noise ratio and subjective image quality were found (all p>0.05). No significant differences in attenuation levels were found in the thoracic aorta and all segments of the coronary arteries (all p>0.05). ConclusionUsage of low iodine concentration CM and injection with high flow rates is feasible. High flow rates (9mL/s) of Iopromide 240 were safely injected without complications and should not be considered a drawback in clinical practice. No significant differences in peak pressure and image quality were found. This creates a doorway towards applicability of a broad variety in flow rates and IDRs and subsequently more individually tailored injection protocols.