Generation Dual-source CT System Research Articles

Deep learning-based virtual noncalcium imaging in multiple myeloma using dual-energy CT.

Dual-energy CT with virtual noncalcium (VNCa) images allows the evaluation of focal intramedullary bone marrow involvement in patients with multiple myeloma. However, current commercial VNCa techniques suffer from excessive image noise and artifacts due to material decomposition used in synthesizing VNCa images. In this work, we aim to improve VNCa image quality for the assessment of focal multiple myeloma, using an Artificial intelligence based Generalizable Algorithm for mulTi-Energy CT (AGATE) method. AGATE method used a custom dual-task convolutional neural network (CNN) that concurrently carries out material classification and quantification. The material classification task provided an auxiliary regularization to the material quantification task. CNN parameters were optimized using custom loss functions that involved cross-entropy, physics-informed constraints, structural redundancy in spectral and material images, and texture information in spectral images. For training data, CT phantoms (diameters 30 to 45cm)withtissue-mimicking inserts were scanned on a third generation dual-source CT system. Scans were performed at routine dose and half of the routine dose. Small image patches (i.e., 40 × 40 pixels) of tissue-mimicking inserts with known basis material densities were extracted for training samples. Numerically simulated insert materials with various shapes increased diversity of training samples. Generalizability of AGATE was evaluated using CT images from phantoms and patients. In phantoms, material decomposition accuracy was estimated using mean-absolute-percent-error (MAPE), using physical inserts that were not used during the training. Noise power spectrum (NPS) and modulation transfer function (MTF) were compared across phantom sizes and radiation dose levels. Five patients with multiple myeloma underwent dual-energy CT, with VNCa images generated using a commercial method and AGATE. Two fellowship-trained musculoskeletal radiologists reviewed the VNCa images (commercial and AGATE) side-by-side using a dual-monitor display, blinded to VNCa type, rating the image quality for focal multiple myeloma lesion visualization using a 5-level Likert comparison scale (-2=worse visualization and diagnostic confidence, -1=worse visualization but equivalent diagnostic confidence, 0=equivalent visualization and diagnostic confidence, 1=improved visualization but equivalent diagnostic confidence, 2=improved visualization and diagnostic confidence). A post hoc assignment of comparison ratings was performed to rank AGATE images in comparison to commercial ones. AGATE demonstrated consistent material quantification accuracy across phantom sizes and radiation dose levels, with MAPE ranging from 0.7% to 4.4% across all testing materials. Compared to commercial VNCa images, the AGATE-synthesized VNCa images yielded considerably lower image noise (50-77% noise reduction) without compromising noise texture or spatial resolution across different phantom sizes and two radiation doses. AGATE VNCa images had markedly reduced area under NPS curves and maintained NPS peak frequency (0.7 lp/cm to 1.0 lp/cm), with similar MTF curves (50% MTF at 3.0 lp/cm). In patients, AGATE demonstrated reduced image noise and artifacts with improved delineation of focal multiple myeloma lesions (all readers comparison scores indicating improved overall diagnostic image quality [scores 1 or 2]). AGATE demonstrated reduced noise and artifacts in VNCa images and ability to improve visualization of bone marrow lesions for assessing multiple myeloma.

Photon-Counting Computed Tomography for Coronary Stent Imaging: In Vitro Evaluation of 28 Coronary Stents.

The aim of this study was to assess in-stent lumen visibility and quantitative image characteristics of different coronary stents using a novel photon-counting detector (PCD) computed tomography (CT) system in comparison to a state-of-the-art energy-integrating detector (EID) CT scanner. In this in vitro phantom study, 28 different coronary stents ranging from 2.25 to 4.5 mm lumen diameter were expanded into plastic tubes filled with contrast agent. Stent-containing plastic tubes were positioned in a custom-made emulsion-filled phantom, which was inserted into an anthropomorphic phantom simulating a medium-sized patient. Computed tomography scans were acquired parallel to the scanners' z axis using a novel cadmium telluride-based PCD CT system (SOMATOM CountPlus; Siemens Healthcare GmbH, Forchheim Germany), operating in 2 different modes (standard-resolution mode [SR] and ultra-high-resolution [UHR] mode), and a latest generation dual-source EID CT system (SOMATOM Force; Siemens Healthcare GmbH, Forchheim). CTDIvol-matched images were reconstructed with comparable convolution kernels and using the same reconstruction parameters. In-stent lumen visibility (in %), increase in in-stent attenuation (expressed as Δ in-stent CT attenuation), and image noise (in Hounsfield unit) were manually measured. Parts of the image analysis (in-stent lumen visibility) were additionally performed in an automated way. Differences were tested using Wilcoxon signed rank test. The best in-stent lumen visibility was achieved with the PCD-UHR mode and the lowest noise levels with the PCD-SR mode. The median in-stent lumen visibility was significantly higher (P < 0.001) with PCD (SR, 66.7%; interquartile range [IQR], 63.3-72.3; UHR, 68.9%; IQR, 64.4-74.4) compared with EID (65.4%; IQR, 62.2-70.4). The Δ in-stent CT attenuation was significantly lower for PCD in both SR (78 HU; IQR, 46-108; P = 0.024) and UHR (85 HU; IQR, 59-113; P = 0.006) compared with EID (108 HU; IQR, 85-126). Image noise was significantly lower (P < 0.001) for PCD-SR (21 HU; IQR, 21-21) compared with EID images (25 HU; IQR, 24-25.0). The PCD provides superior in-stent lumen visibility and quantitative image characteristics when compared with conventional EID.

Potential for dose reduction in CT emphysema densitometry with post-scan noise reduction: a phantom study.

The aim of this phantom study was to investigate the effect of scan parameters and noise suppression techniques on the minimum radiation dose for acceptable image quality for CT emphysema densitometry. The COPDGene phantom was scanned on a third generation dual-source CT system with 16 scan setups (CTDIvol 0.035-10.680 mGy). Images were reconstructed at 1.0/0.7 mm slice thickness/increment, with three kernels (one soft, two hard), filtered backprojection and three grades of third-generation iterative reconstruction (IR). Additionally, deep learning-based noise suppression software was applied. Main outcomes: overlap in area of the normalized histograms of CT density for the emphysema insert and lung material, and the radiation dose required for a maximum of 4.3% overlap (defined as acceptable image quality). In total, 384 scan reconstructions were analyzed. Decreasing radiation dose resulted in an exponential increase of the overlap in normalized histograms of CT density. The overlap was 11-91% for the lowest dose setting (CTDIvol 0.035mGy). The soft kernel reconstruction showed less histogram overlap than hard filter kernels. IR and noise suppression also reduced overlap. Using intermediate grade IR plus noise suppression software allowed for 85% radiation dose reduction while maintaining acceptable image quality. CT density histogram overlap can quantify the degree of discernibility of emphysema and healthy lung tissue. Noise suppression software, IR, and soft reconstruction kernels substantially decrease the dose required for acceptable image quality. Noise suppression software, IR, and soft reconstruction kernels allow radiation dose reduction by 85% while still allowing differentiation between emphysema and normal lung tissue.

Relation of left atrial appendage closure devices to topographic neighboring structures using standardized imaging by cardiac computed tomography angiography.

BackgroundAlthough left atrial appendage (LAA) anatomy and topographic relations are well understood, little is known about the impairment of neighboring structures (NBS) by an implanted left atrial appendage closure (LAAC) device. This prospective longitudinal observational study for the first time describes distances of implanted LAA closure (LAAC) devices to NBS using a standardized imaging protocol of cardiac computed tomography angiography (cCTA).HypothesiscCTA imaging is an eligible tool for post‐implantation evaluation of LAAC devices and their relation to neighboring structures.MethodscCTA data sets of consecutive patients 6 months after successful LAAC were acquired on a third generation dual‐source CT system and reconstructed with a slice thickness of 0.5 mm. The standardized multi‐planar reconstruction LAA occluder view for post‐implantation evaluation (LOVE) algorithm was used to measure the distances to NBS in relation to LAA morphology and implanted LAAC devices.ResultsA total of 48 patients (median age 80 years, 25% female) were included. Left upper pulmonary vein and circumflex artery were generally closest to occlusion devices (median 2.9 and 2.8 mm, respectively). AMPLATZER AMULET devices were closer to the mitral valve annulus than WATCHMAN devices (6.6 mm (inter quartile range [IQR] 4.9‐8.6) vs 10.9 mm (IQR 7.4‐14.0), P = 0.001). Distances to the left upper pulmonary vein were affected by LAA morphology, with cauliflower type having the closest proximity (1.7 mm [IQR 1.0‐3.4], P = 0.048).ConclusionA standardized cCTA imaging protocol is an eligible tool to accurately measure distances to NBS. Left upper pulmonary vein and circumflex artery are closest to LAAC devices and could thus be most prone to impairment.

Assessment of peri-device leaks after interventional left atrial appendage closure using standardized imaging by cardiac computed tomography angiography.

Cardiac computed tomography angiography(cCTA) has recently been proposed for evaluation of successful interventional left atrial appendage closure(LAA/LAAC). This prospective longitudinal observational study aims to assess this proposal by applying a standardized imaging protocol to detect and quantify peri-device leaks (PDL) after LAAC. cCTAdatasets of consecutive patients 6months after successful LAAC were acquired on a third generation dual-source computed tomography system and reconstructed with a slice thickness of 0.5mm. The standardized multi-planar reconstruction LAA occluder view for post-implantation evaluation (LOVE) algorithm was used to assess PDL in relation to LAA morphology and implanted LAAC devices. A total of 49patients (median age 80years, 24% female) were included consecutively. Overall PDL rate was 31%. Leak rates among different left atrial appendage morphologies varied largely. Windsock type had the highest incidence of PDL (47%). AMPLATZER™ AMULET™ device type revealed slightly higher PDL rates than WATCHMAN™ type and showed larger leaks. However, no statistical differences were found. PDL can be sized best in LOVE sagittal views, whereas a synopsis of LOVE sagittal, axial and coronal views allows further examination and detection of small leaks. PDL are common after successful interventional LAAC, which can be accurately detected and sized by standardized cCTA imaging protocols.

Effect of reduced z-axis scan coverage on diagnostic performance and radiation dose of neck computed tomography in patients with suspected cervical abscess.

PurposeTo evaluate the effect of reduced z-axis scan coverage on diagnostic performance and radiation dose of neck CT in patients with suspected cervical abscess.MethodsFifty-one patients with suspected cervical abscess were included and underwent contrast-enhanced neck CT on a 2nd or 3rd generation dual-source CT system. Image acquisition ranged from the aortic arch to the upper roof of the frontal sinuses (CTstd). Subsequently, series with reduced z-axis coverage (CTred) were reconstructed starting at the aortic arch up to the orbital floor. CTstd and CTred were independently assessed by two radiologists for the presence/absence of cervical abscesses and for incidental and alternative findings. In addition, diagnostic accuracy for the depiction of the cervical abscesses was calculated for both readers. Furthermore, DLP (dose-length-product), effective dose (ED) and organ doses were calculated and compared for CTred and CTstd, using a commercially available dose management platform.ResultsA total of 41 abscesses and 3 incidental/alternative findings were identified in CTstd. All abscesses and incidental/alternative findings could also be detected on CTred resulting in a sensitivity and specificity of 1.0 for both readers. DLP, ED and organ doses of the brain, the eye lenses, the red bone marrow and the salivary glands of CTred were significantly lower than for CTstd (p<0.001).ConclusionsReducing z-axis coverage of neck CT allows for a significant reduction of effective dose and organ doses at similar diagnostic performance as compared to CTstd.

--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.

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.

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.

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.

Initial results of a new generation dual source CT system using only an in-plane comb filter for ultra-high resolution temporal bone imaging.

To prospectively evaluate radiation dose and image quality of a third generation dual-source CT (DSCT) without z-axis filter behind the patient for temporal bone CT. Forty-five patients were either examined on a first, second, or third generation DSCT in an ultra-high-resolution (UHR) temporal bone-imaging mode. On the third generation DSCT system, the tighter focal spot of 0.2 mm(2) removes the necessity for an additional z-axis-filter, leading to an improved z-axis radiation dose efficiency. Images of 0.4 mm were reconstructed using standard filtered-back-projection or iterative reconstruction (IR) technique for previous generations of DSCT and a novel IR algorithm for the third generation DSCT. Radiation dose and image quality were compared between the three DSCT systems. The statistically significantly highest subjective and objective image quality was evaluated for the third generation DSCT when compared to the first or second generation DSCT systems (all p < 0.05). Total effective dose was 63%/39% lower for the third generation examination as compared to the first and second generation DSCT. Temporal bone imaging without z-axis-UHR-filter and a novel third generation IR algorithm allows for significantly higher image quality while lowering effective dose when compared to the first two generations of DSCTs. • Omitting the z-axis-filter allows a reduction in radiation dose of 50% • A smaller focal spot of 0.2 mm (2) significantly improves spatial resolution • Ultra-high-resolution temporal-bone-CT helps to gain diagnostic information of the middle/inner ear.

TH‐C‐18A‐12: Evaluation of the Impact of Body Size and Tube Output Limits in the Optimization of Fast Scanning with High‐Pitch Dual Source CT

Purpose:To evaluate the impact of body size and tube power limits in the optimization of fast scanning with high‐pitch dual source CT (DSCT).Methods:A previously validated MERCURY phantom, made of polyethylene, with circular cross‐section of diameters 16, 23, 30 and 37cm, and connected through tapered sections, was scanned using a second generation DSCT system. The DSCT operates with two independently controlled x‐ray tube generators offering up to 200 kW power reserve (100 kW per tube). The entire lenght of the phantom (42cm) was scanned with two protocols using: A)Standard single‐source CT (SSCT) protocol with pitch of 0.8, and B) DSCT protocol with high‐pitch values ranging from 1.6 to 3.2 (0.2 steps). All scans used 120 kVp with 150 quality reference mAs using automatic exposure control. Scanner radiation output (CTDIvol) and effective mAs values were extracted retrospectively from DICOM files for each slice. Image noise was recorded. All variables were assessed relative to phantom diameter.Results:With standard‐pitch SSCT, the scanner radiation output (and tube‐current) were progressively adapted with increasing size, from 6 mGy (120 mAs) up to 15 mGy (270 mAs) from the thinnest (16cm) to the thickest diameter (37 cm), respectively. By comparison, using high‐pitch (3.2), the scanner output was bounded at about 8 mGy (140 mAs), independent of phantom diameter. Although relative to standard‐pitch, the high‐pitch led to lower radiation output for the same scan, the image noise was higher, particularly for larger diameters. To match the radiation output adaptation of standard‐pitch, a high‐pitch mode of 1.6 was needed, with the advantage of scanning twice as fast.Conclusion:To maximize the benefits of fast scanning with high‐pitch DSCT, the body size and tube power limits of the system need to be considered such that a good balance between speed of acquisition and image quality are warranted.JCRG is an employee of Siemens Medical Solutions USA Inc.

High-pitch coronary CT angiography in dual-source CT during free breathing vs. breath holding in patients with low heart rates

BackgroundCoronary CT angiography (CCTA) is usually performed during breath holding to reduce motion artifacts caused by respiration. However, some patients are not able to follow the breathing commands adequately due to deafness, hearing impairment, agitation or pulmonary diseases. The aim of this study was to evaluate the potential of high-pitch CCTA in free breathing patients when compared to breath holding patients. MethodsIn this study we evaluated 40 patients (20 free breathing and 20 breath holding patients) with a heart rate of 60bpm or below referred for CCTA who were examined on a 2nd generation dual-source CT system. Image quality of each coronary artery segment was rated using a 4-point grading scale (1: non diagnostic–4: excellent). ResultsMean heart rate during image acquisition was 52±5bpm in both groups. There was no significant difference in mean image quality, slightly favoring image acquisition during breath holding (mean image quality score 3.76±0.32 in breath holding patients vs. 3.61±0.45 in free breathing patients; p=0.411). Due to a smaller amount of injected contrast medium, there was a trend for signal intensity to be slightly lower in free breathing patients, but this was not statistically significant (435±123HU vs. 473±117HU; p=0.648). ConclusionIn patients with a low heart rate who are not able to hold their breath adequately, CCTA can also be acquired during free breathing without substantial loss of image quality when using a high pitch scan mode in 2nd generation dual-source CT.

Novel single-source high-pitch protocol for CT angiography of the aorta: comparison to high-pitch dual-source protocol in the context of TAVI planning

Purpose Computed tomography (CT) is increasingly being used for planning purposes prior to trans-arterial valve implantation (TAVI). High-pitch protocols using a 2nd generation dual-source CT (DSCT) allow for a comprehensive assessment of the aortic valve anulus, its distance to the coronary artery ostia, the aortic bulbus and the iliofemoral arteries with very low radiation exposure and low amount of contrast agent. The aim of this study was to evaluate the image quality of a comparable high-pitch scan mode in a modern single-source CT (SSCT) system. Methods 40 patients with severe symptomatic aortic valve stenosis have been examined for planning purposes prior to TAVI. The first 20 consecutive patients were examined with a 2nd generation DSCT system using a high-pitch scan mode (pitch value 3.4) and 60 ml of contrast agent. The second group of 20 consecutive patients were examined with a 128-slice SSCT system, using a high-pitch scan mode (pitch value of 1.7) and 60 ml of contrast agent. Image quality of the aortic valve, the ascending aorta, the coronary artery ostia, the iliofemoral arteries and overall image quality were graded in a blinded fashion using a 4-point-grading-scale. Furthermore, signal intensity and image noise were derived in the ascending aorta and in the ilio-femoral arteries. Results There was a minor but significant difference in the overall image quality score with lower image quality in SSCT (3.5 ± 0.6) when compared to DSCT (3.85 ± 0.4; p = 0.037). The mean image quality score was significantly higher in patients examined in DSCT when compared to SSCT regarding the evaluability of the coronary ostia (4.0 vs. 3.5; p < 0.01) and the image quality of the ascending aorta (4.0 vs. 3.5; p < 0.01). There was no significant difference in evaluation of the aortic valve and its anulus (3.85 for DSCT and 3.65 for SSCT; p = 0.149) and image quality of the iliofemoral arteries (3.65 for DSCT and 3.85 for SSCT; p = 0.140). Signal intensity and image noise did not differ significantly between both groups. Conclusions This study presents a novel high-pitch protocol for modern SSCT scanners, which allows CT angiography for TAVI planning with a similar radiation dose and contrast agent exposition and only small compromises in image quality compared to a high-pitch protocol on a DSCT scanner.

Dual-energy computed tomographic angiography of head and neck arteries with different contrast material doses in second generation dual-source computed tomography system

To explore the feasibility of a dual-energy computed tomographic angiography (DECTA) protocol using test-bolus injection with reduction of contrast material (CM) dose in second generation dual-source CT system. Totally 57 consecutive patients underwent CT angiography scan covering the cervical and cerebral arteries. CT was performed with second generation dual-source CT system. The time to peak (T) using a test-bolus injection was calculated. The patients were divided into three groups (A, B, and C) with different CM doses (40, 45, and 50 ml) and different delay time points [ (T+1) , (T+1) , and (T+2) s] . All the patients were followed by a 48 ml saline flush. Arterial enhancements were quantified by measuring attenuation values of the aortic arch, bifurcation of common carotid artery, contralateral internal jugular vein of the CM injection, superior vein cava, proximal middle cerebral artery, basilar artery, and straight sinus on source images. Visualizations of intracranial artery and ipsilateral venous effect of the CM injection were rated on a four-point grading scale on CTA images for qualitative assessment. Although the attenuation of internal jugular vein and straight sinus were significantly lower in group A than in groups B and C (P<0.05) , the attenuation of aortic arch, superior vein cava, common carotid artery, middle cerebral artery, and basilar artery vessels showed no significant differences among these three groups. The scores of the visualizations of intracranial artery and ipsilateral venous effect of the CM injection were also not significantly different among these three groups. Based on the delay time calculated by a test-bolus injection, a reduced-dose contrast material may provide an equal degree of arterial attenuation and a lower attenuation of vein for dual-energy CTA covering the craniocervical region in second generation dual-source CT system.

High-Pitch 128-Slice Dual-Source CT for the Assessment of Coronary Stents in a Phantom Model

To evaluate the quality of stent lumen delineation using dual-source computed tomography (DSCT) in the standard-pitch mode (SP) as compared to the high-pitch mode (HP) in a phantom study. Forty different coronary stents placed in plastic tubes filled with contrast agent were imaged with a second generation DSCT system in a SP (pitch 0.23) and HP (pitch 3.4) mode in orientations of 0°, 45°, and 90° relative to the z-axis. Two observers independently measured the in-stent lumen and the attenuation values in the center of the stents. The artificial lumen narrowing (ALN) was calculated using the measured in-stent lumen and the nominal diameter of the plastic tube. Interobserver correlation was excellent for in-stent lumen (0.86) and attenuation measurements (0.91). There was no significant difference neither for ALN (SP: 54.7-62.8%; HP: 55.8-64.0%) nor attenuation (SP: 356-395 Hounsfield units [HU]; HP: 352-384 HU) between SP and HP mode. For both modes, the orientation of the stent relative to the z-axis significantly affected ALN and attenuation (each P < .001). CT volume dose index was significantly lower using HP mode as compared to SP mode (P < .001). The HP mode in DSCT provides visualization of the coronary in-stent lumen comparable to that measured in SP mode while reducing applied radiation dose in a stationary phantom model.

High-Pitch Electrocardiogram-Triggered Computed Tomography of the Chest

Chest pain is one of the most frequent symptoms in the emergency department. A variety of different diseases, some of them acutely life threatening, can be the underlying cause. Electrocardiogram (ECG)-gated computed tomography angiography of the thorax has been proposed as a cost and time effective imaging technique for these patients. We describe a new high-pitch scan mode, which has been developed specifically for low-dose ECG-triggered computed tomography angiography using dual source computed tomography (CT). Twenty-four patients were examined with this technique on a second generation dual source CT system. The scan mode uses a pitch of 3.2 to acquire a spiral CT data set of the complete thorax in less than 1 second with a temporal resolution of 75 ms (scan parameters: 128 x 0.6 mm collimation, 0.28 seconds gantry rotation time, 370 mAs at 100 kV [15 patients] and 320 mAs at 120 kV [9 patients], reconstructed slice thickness 0.6 mm, increment 0.4 mm). Data acquisition was prospectively triggered at 50% to 60% of the RR interval to cover the range over the heart in diastole. A triple phase contrast injection protocol (total volume: 80 mL) was used to optimize enhancement of the pulmonary and systemic arterial vessels. Image quality was evaluated using a 4-point scale (1 = absence of motion artifacts; 2 = slight motion artifacts, fully evaluable; 3 = motion artifacts, but evaluable; 4 = unevaluable) on a per-segment basis. The patients had an average heart rate of 68 +/- 15 bpm (range: 43-111 bpm) during data acquisition. Motion artifact free visualization of the aorta and pulmonary vessels was possible in each case, of 344 coronary artery segments, 242 (70%) had an image quality score of 1, 60 segments (17%) a score of 2, 28 segments (8%) a score of 3, and 14 segments (4%) were rated as "unevaluable." In 17 patients (10 patients with a heart rate < or =60 bpm) all segments were evaluable. The average dose length product was 113 +/- 11 mGy x cm per scan (mean effective dose 1.6 +/- 0.2 mSv) at 100 kV and 229 +/- 31 mGy x cm per scan (mean effective dose 3.2 +/- 0.4 mSv) at 120 kV. Our initial results indicate that this high-pitch scan mode allows motion artifact free and accurate visualization of the thoracic vessels, and diagnostic image quality of the coronary arteries in patients with low and stable heart rates at a very low radiation exposure.

Dual energy CTA of the supraaortic arteries: Technical improvements with a novel dual source CT system

Objectives Computed tomography angiography (CTA) is a well-accepted imaging modality to evaluate the supraaortic vessels. Initial reports have suggested that dual energy CTA (DE-CTA) can enhance diagnosis by creating bone-free data sets, which can be visualized in 3D, but a number of limitations of this technique have also been addressed. We sought to describe the performance of DE-CTA of the supraaortic vessels with a novel dual source CT system with special emphasis on image quality and post-processing related artifacts. Materials and methods Thirty-three patients underwent carotid CT angiography on a second generation dual source CT system. Simultaneous acquisitions of 100 and 140 kV data sets in arterial phase were performed. Two examiners evaluated overall bone suppression with a 3-point scale (1 = poor; 3 = excellent) and image quality regarding integrity of the vessel lumen of different vessel segments ( n = 26) with a 5-point scale (1 = poor; 5 = excellent), CTA source data served as the reference. Results Excellent bone suppression could be achieved in the head and neck. Only minor bone remnants occurred, mean score for bone removal was 2.9. Mean score for vessel integrity was 4.3. Eight hundred fifty-seven vessel segments could be evaluated. Six hundred thirty-five segments (74%) showed no lumen alteration, 65 segments (7.6%) lumen alterations <10%, 27 segments (3.1%) lumen alterations >10% resulting in a total luminal reduction <50%, 17 segments (2%) lumen alterations of more than 10% resulting in a total luminal reduction >50%, and 113 segments (13.2%) showed a gap in the vessel course (100% total lumen reduction). Artificial gaps of the vessel lumen occurred in 28 vessel segments due to artifacts caused by dental hardware and in all but one (65) ophthalmic arteries. Conclusions Excellent bone suppression could be achieved, DE imaging with 100 and 140 kV lead to improved image quality and vessel integrity in the shoulder region than previously reported. The ophthalmic artery still cannot be adequately visualized.

Myocardial Stress Perfusion with a Novel Dual‐Source CT Scanner – Technical Update and Initial Clinical Experience

SummaryTraditionally, myocardial perfusion imaging by CT has been hampered by limited detector size and stability of Hounsfield Units in moving cardiac acquisition modes. In the present article, we describe the technical principles of a novel, dynamic heart shuttle scan acquisition using a second generation dual source CT system (SOMATOM Definition Flash, Siemens Healthcare, Forchheim, Germany). With simultaneous injection of iodinated contrast agent, this protocol allows for sequential assessment of myocardial enhancement with reasonable radiation exposure of less than 10 mSv. We also present the case of a 69‐year‐old male patient who underwent dynamic CT‐based myocardial perfusion imaging to determine the hemodynamic relevance of a stenosis in the left anterior descending coronary artery.