Third-generation Dual-source CT Scanner Research Articles

Feasibility of Ultra-Low Volume Contrast-Saline Mixture Injection With Dual-Flow Technique in a Pre-TAVI Computed Tomography Angiography.

To explore the feasibility and image quality of ultra-low volume contrast-saline mixture injection with dual-flow injection technique in a computed tomography angiography (CTA) protocol in patients scheduled for transcatheter aortic valve implantation (TAVI). Forty (40) TAVI candidates underwent investigation with CTA using a third-generation dual-source CT scanner between September and November 2020. Different volumes of a monophasic contrast-saline mixture at an 80:20 ratio were administered at an infusion rate of 3 mL/s in 20 patients (group A). The injected volume was based on patient body mass index (BMI): 50 mL if BMI <29 kg/m2 and 63 mL if BMI >29 kg/m2. The other 20 patients (group B)-the control cases-received a total of 65 mL of contrast medium (CM), in multiphasic injections at different flow rates, followed by 10 mL of saline. The images that were obtained were prospectively evaluated for image quality, vessel attenuation (HU), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and estimated radiation dose. Image quality of the aortic root and ilio-femoral vessels was diagnostic in all patients. Vascular attenuation was >200 HU and CNR >3 at any vessel level. Data from this study suggest that a monophasic ultra-low volume contrast-saline mixture injection with a dual-flow technique can provide clear visualisation of the aortic root and ilio-femoral vessels in pre-TAVI CTA, which is comparable with a standard multiphasic volume injection protocol.

Ultrahigh-resolution computed tomography of the cervical spine without dose penalty employing a cadmium-telluride photon-counting detector

PurposeThis cadaveric study compared image quality between a third-generation dual-source CT scanner with energy-integrating detector technology (EID) and a first-generation CT system employing a photon-counting detector (PCD) for the cervical spine in ultrahigh-resolution mode. MethodsThe cervical spine of eight formalin-fixed full-body cadaveric specimens was scanned with both CT systems using 140 kVp scan protocols matched for CTDIvol (full-dose; low-dose; ultralow-dose; 10 mGy; 3 mGy; 1 mGy). Images were reconstructed with 1 mm slice thickness and 0.5 mm increment. Three radiologists rated overall subjective image quality based on an equidistant five-point scale with the intraclass correlation coefficient (ICC) calculated for assessment of interobserver reliability. Contrast-to-noise ratios were calculated individually for bone (CNRbone) and muscle tissue (CNRmuscle) to provide objective criteria of image analysis. ResultsSubjective image quality, as well as CNRbone, and CNRmuscle were each superior for PCD-CT compared to EID-CT among dose-matched scan protocol pairs (all p < 0.05). Between full-dose EID-CT and low-dose PCD-CT, subjective image quality was equal (p = 0.903), while superior quantitative results regarding the latter were ascertained (both p < 0.001). Similarly, objective analysis determined higher CNRbone, and CNRmuscle in ultralow-dose PCD-CT compared to low-dose EID-CT (both p < 0.001), while readers considered the image quality of the respective studies comparable (p > 0.99). Interobserver reliability was good, denoted by an ICC of 0.861 (95 % confidence interval: 0.788 – 0.914; p < 0.001). ConclusionsIn cervical spine examinations, both subjective and objective image quality of PCD-CT were superior to EID-CT in comparison of scan protocols with corresponding dose levels, suggesting potential for significantly reducing the radiation exposure without compromising image quality.

Clinical Question Influence on Radiation Dose of Cardiac CT Scan in Children.

Background: To assess the impact of different clinical questions on radiation doses acquired during cardiac computed tomography in children. Methods: A total of 116 children who underwent cardiac CT on a third-generation dual-source CT scanner were included. The clinical questions were divided into three main categories: the extent of scanning in the z-axis, coronary artery assessment and cardiac function assessment. Radiation dose values represented as a dose-length product (DLP) in mGy*cm were recorded from the CT scanner protocols. Results: There were significantly higher doses in cases with cardiac function assessment (median DLP 348 versus 59 mGy*cm, p < 0.01) and in cases with coronary artery assessment (median DLP 133 versus 71 mGy*cm, p < 0.01). Conclusion: The most important factor was the assessment of cardiac function, where the median radiation dose was 4.3× higher in patients with a request for cardiac function assessment. We strongly recommend that clinical requests for cardiac CT should be carefully considered in the paediatric population.

Metal artefact reduction in low-dose computed tomography: Benefits of tin prefiltration versus postprocessing of dual-energy datasets over conventional CT imaging

IntroductionThe purpose of this study was to determine the potential for metal artefact reduction in low-dose multidetector CT as these pose a frequent challenge in clinical routine. Investigations focused on whether spectral shaping via tin prefiltration, virtual monoenergetic imaging or virtual blend imaging (VBI) offers superior image quality in comparison with conventional CT imaging. MethodsUsing a third-generation dual-source CT scanner, two cadaveric specimens with different metal implants (dental, cervical spine, hip, knee) were examined with acquisition protocols matched for radiation dose with regards to tube voltage and current. In order to allow for precise comparison, and due to the relatively short scan lengths, automatic tube current modulation was disabled. Specifically, the following scan protocals were examined: conventional CT protocols (100/120 kVp), tin prefiltration (Sn 100/Sn 150 kVp), VBI and virtual monoenergetic imaging (VME 100/120/150 keV). Mean attenuation and image noise were measured in hyperdense and hypodense artefacts, in artefact-impaired and artefact-free soft tissue. Subjective image quality was rated independently by three radiologists. ResultsObjectively, Sn 150 kVp allowed for the best reduction of hyperdense streak artefacts (p < 0.001), while VME 150 keV and Sn 150 kVp protocols facilitated equally good reduction of hypodense artefacts (p = 0.173). Artefact-impaired soft tissue attenuation was lowest in Sn 150 kVp protocols (p ≤ 0.011), whereas all VME showed significantly less image noise compared to conventional or tin-filtered protocols (p ≤ 0.001). Subjective assessment favoured Sn 150 kVp regarding hyperdense streak artefacts and delineation of cortical bone (p ≤ 0.005). The intraclass correlation coefficient was 0.776 (95% confidence interval: 0.712–0.831; p < 0.001) indicating good interrater reliability. ConclusionIn the presence of metal implants in our cadaveric study, tin prefiltration with 150 kVp offers superior artefact reduction for low-dose CT imaging of osseous tissue compared with virtual monoenergetic images of dual-energy datasets. The delineation of cortical boundaries seems to benefit particularly from spectral shaping. Implications for practiceLow-dose CT imaging of osseous tissue in combination with tin prefiltration allows for superior metal artefact reduction when compared to virtual monoenergetic images of dual-energy datasets. Employing this technique ought to be considered in daily routine when metal implants are present within the scan volume as findings suggest it allows for radiation dose reduction and facilitates diagnosis relevant to further treatment.

Quantifying Myocardial Strain of the Left Ventricle in Normal People Using Feature-Tracking Based on Computed Tomography Imaging.

Objective: The objective was to evaluate the normal value of left ventricular myocardial strain using the computed tomography feature-tracking technique and to explore the correlation between myocardial strains and cardiac function parameters. Methods: Participants suspected of coronary heart disease were selected from 17 August 2020 to 5 November 2020 to undergo coronary computed tomography angiography using a third-generation dual-source CT scanner. Data were imported into a commercial software (Medis) after multiphase reconstruction. The cardiac function parameters, radial (Err), circumferential (Ecc), and longitudinal strain (Ell) of the left ventricle were recorded. Results: A total of 87 normal subjects were enrolled, including 41 males and 46 females. For healthy subjects, the global radial strain (GRS), circumferential strain (GCS), and longitudinal strain (GLS) of the left ventricle were 74.5 ± 15.2%, −22.7 ± 3.0%, and −26.6 ± 3.2%, respectively. The Err and Ecc absolute values (|Ecc|) were the largest at the apex, and the |Ell| gradually increased from the base to the apex. The Err and |Ecc| were the largest in the lateral and inferior wall, respectively. |Ell| showed a clockwise decrease from the lateral wall in the short axis. Meanwhile, the GRS and |GLS| in females were higher than that in males. Multiple linear regression analysis showed that both SV and LVEF were the independent determinants of GRS, GCS, and GLS. BMI and CO were the independent determined factors of GCS. Conclusions: At a reasonable radiation dose, CT feature-tracking is a feasible and reproducible method to analyze left ventricular myocardial strain. Left ventricular myocardial strain in normal subjects varies in gender, segments, levels, and regions.

Feasibility of sub-second CT angiography of the abdomen and pelvis with very low volume of contrast media, low tube voltage, and high-pitch technique, on a third-generation dual-source CT scanner

BackgroundConcerns about potential risks of using contrast media in patients with chronic renal insufficiency limit the utilization of CT angiography in this population. PurposeTo evaluate the feasibility of abdominopelvic CTA with very low volumes of contrast media. Material and methodsIn this retrospective study, 20 patients with chronic renal insufficiency underwent high-pitch abdominopelvic (AP) CTA on a third-generation dual-source CT scanner with 30 mL of nonionic iodinated contrast. The homogeneity of intravascular attenuation at the suprarenal aorta, infrarenal aorta, and the right common iliac artery was measured. Image noise, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR) were used to assess objective image quality. Subjective image quality was evaluated on a 5-point scale (1 = unacceptable; 5 = excellent). ResultsTwelve male and eight female patients underwent CTA of the abdomen and pelvis at 80 kVp. Five CTAs also included the chest (CAP). The mean scan duration was 0.78 ± 0.19 s for AP and 0.96 ± 0.06 s for CAP CTAs. The mean ± SD of attenuation at suprarenal aorta, infrarenal aorta, and right common iliac artery were 235.1 ± 68.0, 249.2 ± 61.3, and 254.4 ± 67.7 HU, respectively. The attenuation was homogeneous across vascular levels (P = 0.06). All scans had diagnostic subjective image quality with the median (IQR) of 3.5 (1.75). CNR and SNR were homogeneous across vascular levels (P = 0.08 and P = 0.14, respectively). ConclusionSub-second, high-pitch abdominopelvic CTA with a low volume of contrast in patients with chronic renal insufficiency is technically and clinically feasible with good diagnostic image quality and homogenous attenuation across vascular levels.

Impact of Coronary CT angiography in combination with CAD-RADS on the management of coronary artery disease patients

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Siemens Healthineers Introduction Coronary CT angiography (CCTA) plays an increasing role in the detection and risk stratification of patients with coronary artery disease (CAD). The Coronary Artery Disease – Reporting and Data System (CAD-RADS) allows for standardized classification of CCTA results and, thus, may improve patient management. Purpose Aim of this study was to assess the impact of CCTA in combination with CAD-RADS on patient management and to identify the impact of cardiovascular risk factors (CVRF) on CAD severity. Methods CCTA was performed on a third-generation dual-source CT scanner in patients, who were referred to a radiology centre by their attending physicians. In a total of 4801 patients, CVRF were derived from medical reports and anamnesis. Results The study population consisted of 4770 patients (62.0 (54.0-69.0) years, 2841 males) with CAD (CAD-RADS 1-5), while 31 patients showed no CAD and were excluded from further analyses. Age, male gender and the number of CVRF were associated with more severe CAD stages (all p &amp;lt; 0.001). 3040 patients (63.7 %) showed minimal or mild CAD requiring optimization of CVRF i.e. medical therapy but no further assessment at his time. A group of 266 patients (5.6 %) had a severe CAD defined as CAD-RADS 4B/5. In the multivariate regression analysis, age, male gender, history of smoking, diabetes mellitus and hyperlipidaemia were significant predictors for severe CAD, whereas arterial hypertension and family history of CAD did not reach significance. Of note, a subgroup of 28 patients (10.5 %) with a severe CAD (68.5 (65.5-70.0) years, 26 males, both p = n.s.) had no CVRF. Conclusions CCTA in combination with the CAD-RADS allowed for effective risk stratification of CAD patients. The majority of the patients showed non-obstructive CAD and, thus, could be treated conservatively without the need for further CAD assessment. CVRF out of arterial hypertension and family history had an impact on CAD severity reflected in higher CAD-RADs gradings. Of note, a relevant fraction of patients with CAD did not have any CVRF and, thus, may not be covered by risk stratification models. CAD-RADS n Age (years) Males (%) 1 1453 56.0 (50.0-62.0) 623 (42.9 %) 2 1587 62.0 (55.0-69.0) 918 (57.8 %) 3 1067 66.0 (59.0-71.0) 749 (70.2 %) 4A 397 66.0 (59.0-72.0) 317 (79.8 %) 4B 162 67.0 (61.0-74.0) 139 (85.8 %) 5 104 66.0 (58.5.0-77.0) 95 (91.3 %)

Whole Body Low Dose Computed Tomography Using Third-Generation Dual-Source Multidetector With Spectral Shaping: Protocol Optimization and Literature Review.

For decades, the main imaging tool for multiple myeloma (MM) patient’s management has been the conventional skeleton survey. In 2014 international myeloma working group defined the advantages of the whole-body low dose computed tomography (WBLDCT) as a gold standard, among imaging modalities, for bone disease assessment and subsequently implemented this technique in the MM diagnostic workflow. The aim of this study is to investigate, in a group of 30 patients with a new diagnosis of MM, the radiation dose (CT dose index, dose-length product, effective dose), the subjective image quality score and osseous/extra-osseous findings rate with a modified WBLDCT protocol. Spectral shaping and third-generation dual-source multidetector CT scanner was used for the assessment of osteolytic lesions due to MM, and the dose exposure was compared with the literature findings reported until 2020. Mean radiation dose parameters were reported as follows: CT dose index 0.3 ± 0.1 mGy, Dose-Length Product 52.0 ± 22.5 mGy*cm, effective dose 0.44 ± 0.19 mSv. Subjective image quality was good/excellent in all subjects. 11/30 patients showed osteolytic lesions, with a percentage of extra-osseous findings detected in 9/30 patients. Our data confirmed the advantages of WBLDCT in the diagnosis of patients with MM, reporting an effective dose for our protocol as the lowest among previous literature findings.

Systolic High-Pitch Coronary CT Angiography for Evaluation of the Coronary Arteries in Heart Transplant Recipients.

OBJECTIVE. The purpose of this study was to evaluate the feasibility, image quality, and radiation dose of high-pitch coronary CT angiography (CCTA) in orthotopic heart transplant (OHT) recipients. SUBJECTS AND METHODS. Twenty-two consecutive OHT recipients (16 men, six women; median age, 66.5 years [interquartile range, 51.3-70.3 years]; median heart rate, 91 beats/min [interquartile range, 79.3-97.3 beats/min]) underwent CCTA with a third-generation dual-source CT scanner in high-pitch mode to rule out coronary allograft vasculopathy. Data acquisition was triggered at 30% of the R-R interval. Two independent observers blindly assessed image quality on a per-segment, per-vessel, and per-patient basis using a 4-point scale (4, excellent; 1, not evaluative). Scores 2-4 indicated diagnostic quality. Studies were compared with previously performed retrospective ECG-gated examinations, when available. Interobserver agreement on the image quality was assessed with kappa statistics. Radiation dose was recorded. RESULTS. A total of 322 coronary segments were evaluated. Diagnostic image quality was observed in 97.5% of the segments. Interobserver agreement for image quality assessment was very good on a per-patient (κ = 0.82), per-vessel (κ = 0.83), and per-segment basis (κ = 0.89). The median per-patient image quality score was 4.0 (3.0-4.0) for the entire coronary tree. A comparison of image quality scores between high-pitch and retrospective ECG-gated CCTA examinations showed no significant differences, but the estimated mean radiation dose was significantly lower for the high-pitch mode (median dose-length product, 31.6 mGy × cm [interquartile range, 23.1-38.8 mGy × cm] vs 736.5 mGy × cm [interquartile range, 655.5-845.7 mGy × cm], p < 0.001). CONCLUSION. Performing single-heartbeat high-pitch CCTA during the systolic phase of the cardiac cycle in OHT recipients results in diagnostic image quality in coronary angiograms at very low radiation dose.

Establishment of Submillisievert Abdominal CT Protocols With an In Vivo Swine Model and an Anthropomorphic Phantom

OBJECTIVE. The purpose of this study was to evaluate radiation dose, effective dose, and image quality of different low-dose abdominal CT protocols in a swine model and an anthropomorphic phantom using a third-generation dual-source CT scanner. MATERIALS AND METHODS. Four different abdominal low-dose protocols were established using a swine model and were regarded as diagnostic by two experienced radiologists on the basis of clarity and sharpness of anatomic structures. General image conditions such as noise and spatial resolution as well as diagnostic acceptability and artifacts were evaluated. Objective image quality was determined by measuring signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in different anatomic locations. To evaluate the effective dose, thermoluminescent dosimeter (TLD) measurements were repeated in a phantom. RESULTS. Diagnostic acceptability, spatial resolution, and noise were rated as optimal in all four protocols, which were therefore regarded as diagnostic. We found no statistically significant differences in SNR or CNR for the four low-dose protocols. Effective dose determined from the phantom measurements did not exceed 0.33 mSv for any protocol. Overall evaluation of the 86 TLD measurements for the four low-dose protocols revealed a statistically significant difference in radiation dose (p < 0.0001), showing that the dual-source protocol had the lowest radiation dose. CONCLUSION. Submillisievert abdominal CT is feasible with good image quality and doses even lower than conventional abdominal radiography. Our dual-source protocol achieved the lowest dose, which further shows that dual-source imaging is possible in the submillisievert range without additional dose.

Leadless Cardiac Pacemaker (LCP) without Diagnostic Relevant Artifacts in DualSource and DualEnergy-CT Examinations in First- to Third-Generation DSCT Scanner

To identify the influence and artifact burden in cardiac CT imaging of a leadless cardiac pacemaker (LCP) performed with all three generations of DualSource CT (DSCT) Scanners. The LCP was examined in DSCT scanners of the first to third generation using DualEnergy (DECT) and DSCT as well as alterations of the current-time product. For DECT examinations, virtual monoenergetic images were computed manually on a dedicated workstation. Virtual voltage was manually selected by subjective assessment of the lowest artifact burden. Systematic variations of the pacemaker angle to the gantry were assessed, too. The angle was successively increased by 10°, ranging from 0° to 90°. Artifact burden was quantified on a five-point Likert scale (1- no artifacts, 2- few artifacts, 3- moderate artifacts, 4- many artifacts, and 5- massive artifacts). Likert values of 1-3 were considered diagnostic and assessed by two board-certified radiologists in consensus. In total, 200 examinations were analyzed, a mean Likert value of 1.93 ± 0.61 was found overall. None of the images were assessed Likert value >3. The positioning evaluation showed a clear and significant reduction of artifact burden toward lower angles, (0°: 1.4 ± 0.5 vs. 90° 2.55 ± 0.51). At scanner level, second-generation DSCT performed significantly better (1.68 ± 0.47) than both other scanners. Comparison of technique (DECT vs. DSCT) revealed a significantly improved image quality in DSCT examinations. LCP can be safely examined in DSCT scanner of the first to third generation with the evaluated protocols and techniques, which are currently in use. Artifact burden can be significantly reduced by aligning or approaching the LCP's longitudinal axis toward the scanner's z-axis.

Coronary CT angiography (CCTA) using third-generation dual-source CT for ruling out in-stent restenosis

Late in-stent restenosis (ISR) has become increasingly important, in particular due to neo-atherosclerosis. CCTA is a highly sensitive method for detecting coronary plaques. Its diagnostic accuracy regarding ISR is controversial. Stent artifacts can impede image quality, but recent developments in CT-technology may help to overcome some of these problems and allow for improved diagnostic accuracy. Consecutive patients after previous coronary revascularization who had stable symptoms or signs of possible disease progression were examined using a third-generation dual-source CT scanner. After the scan, patients were followed for clinical events (MACE) over a mean of 399 days. Patients with high-grade stenoses were referred for invasive coronary angiography (ICA), unclear findings were further evaluated either by ICA or functional testing. Overall, 226 patients were included. A total of 457 stents were evaluated (2.0 ± 1.4 per patient). Mean stent diameter was 2.9 ± 0.45mm. In 61%, a high-pitch protocol was employed. Mean dose-length product (DLP) of CCTA was 159.2 mGycm, corresponding to 2.2mSv using a conversion factor of k = 0.014. Mean amount of contrast agent was 58.3 ± 12.5ml. In 145 patients (64%), CCTA was negative. In this group, one MACE occurred (acute coronary syndrome) during follow-up in a patient who had also undergone unremarkable ICA. In 23 patients (10%), CCTA detected 28 ISR which were confirmed and treated by ICA (true positive). In 27 patients (12%), ISR was suspected by CCTA but excluded by ICA (false positive), 30 patients (13%) had unclear findings and normal non-invasive tests. No MACE occurred during follow-up in these patients. One patient was misclassified in CCTA as having intermediate and not high-grade ISR who underwent revascularization within 3 months. Eleven patients (5%) were lost to follow-up. During follow-up, eight patients had myocardial infarctions due to five ISRs and three de novo lesions. No patient died. In cases with unclear or false-positive findings, the amount of stents was significantly higher, stents were smaller and patients had a higher BMI. In almost two-thirds of symptomatic patients with previous coronary stent implantation, ISR could be ruled out by CCTA. 10% of patients had definite ISR. The rate of false-negative findings was low (< 1%), whereas the rate of false positive or inconclusive findings was 25%, leading to invasive rule-out of ISR by ICA in 12%. CCTA appears valuable as a tool for safely excluding ISR. It might help to avoid invasive diagnostic procedures. Further analyses are warranted, in particular regarding the influence of stent dimensions and the total amount of stents in a patient.

Efficacy and Radiation Exposure of Ultra-Low-Dose Chest CT at 100 kVp with Tin Filtration in CT-Guided Percutaneous Core Needle Biopsy for Small Pulmonary Lesions Using a Third-Generation Dual-Source CT Scanner

PurposeTo prospectively investigate efficacy and radiation dose of ultra-low-dose CT–guided percutaneous core needle biopsy (PCNB) at 100 kVp with tin filtration (100Sn kVp) for small pulmonary lesions. Materials and MethodsStudy enrolled and randomly assigned 210 patients to standard-dose CT (n = 70) or ultra-low-dose CT (n = 140; 1:2 randomization scheme) protocol. Standard-dose CT settings were reference 110 kVp and 50 mAs, and ultra-low-dose CT settings were fixed at 100Sn kVp and 70 mAs. All PCNBs in patients with small pulmonary lesions (< 3 cm) were performed on a third-generation dual-source CT scanner. Diagnostic performance, complication rate, image quality, and radiation dose were compared. ResultsSensitivity, specificity, and accuracy for diagnosis of malignancy were 95.7%, 100%, and 96.9% with standard-dose CT and 93.8%, 100%, and 95.4% with ultra-low-dose CT (P > .05). Complication rate showed no significant differences between protocols (P > .05). Mean volume CT dose index) and total dose-length product were significantly lower in ultra-low-dose CT compared with standard-dose CT (0.24 mGy vs 3.3 mGy ± 1.1 and 9.84 mGy-cm ± 0.70 vs 110.5 mGy-cm ± 45.1; P < .001). Effective dose for ultra-low-dose CT was significantly lower than that for standard-dose CT (0.14 mSv ± 0.02 vs 1.78 mSv ± 0.76; −92.1%; P < .001). Image quality of ultra-low-dose CT met the requirements of PCNB. ConclusionsUltra-low-dose CT-guided PCNB at 100Sn kVp spectral shaping significantly reduced radiation dose on a third-generation dual-source CT, while maintaining high diagnostic accuracy and safety for small pulmonary lesions.

Imaging of anomalous pulmonary venous connections by multidetector CT angiography using third-generation dual source CTscanner.

Abnormal embryological development of the pulmonary veins can manifest as either partial or total anomalous drainage into the systemic venous circulation. Echocardiography does not provide adequate information in all cases as the optimal visualization of anomalous structures is limited by the availability of acoustic window; also it is highly operator dependent. However, multidetector CT angiography, with its multiplanar reformatting and volume rendering techniques, offers precise information about the three-dimensional anatomy and spatial relationships of the cardiovascular structures. With advent of dualsource CT scanners and use of advanced dose reduction techniques, this information can be obtained in a short time with minimal radiation dose. In this pictorial essay, we present the multidetectorCT imaging findings of the spectrum of total and partial anomalous pulmonary venous connections, using a third-generation dual source CT scanner.

Comprehensive morphologic and functional imaging of heart transplant patients: first experience with dynamic perfusion CT.

We aimed to assess the diagnostic performance of a combined protocol with coronary computed tomography angiography (CCTA) and stress CT perfusion imaging (CTP) in heart transplant patients for comprehensive morphological and functional imaging. In this prospective study, 13 patients undergoing routine follow-up 8±6 years after heart transplantation underwent CCTA and dynamic adenosine stress CTP using a third-generation dual-source CT scanner, cardiac magnetic resonance (MR) adenosine stress perfusion imaging at 1.5 T, and catheter coronary angiography. In CCTA stenoses >50% luminal diameter narrowing were noted. Myocardial perfusion deficits were documented in CTP and MR. Quantitative myocardial blood flow (MBF) was calculated with CTP. Left ventricular ejection fraction was determined on cardiac MR cine images. Radiation doses of CT were determined. One of the 13 patients had to be excluded because of severe motion artifacts. CCTA identified three patients with stenosis >50%, which were confirmed with catheter coronary angiography. CTP showed four patients with stress-induced myocardial hypoperfusion, which were confirmed by MR stress perfusion imaging. Quantitative analysis of global MBF showed lower mean values as compared to known reference values (MBF under stress 125.5 ± 34.5 ml/100 ml/min). Average left ventricular ejection fraction was preserved (56 ± 5%). In heart transplant patients, a comprehensive CT protocol for the assessment of morphology and function including CCTA and CTP showed good concordance to results from MR perfusion imaging and catheter coronary angiography. • Stress CT perfusion imaging enables the detection of myocardial ischemia • CT myocardial perfusion imaging can be combined with coronary computed tomography angiography • Combining perfusion and coronary CT imaging is accurate in heart transplant patients • CT myocardial perfusion imaging can be performed at a reasonable radiation dose.

Implementation of Size-Dependent Local Diagnostic Reference Levels for CT Angiography.

Diagnostic reference levels (DRLs) are established for standard-sized patients; however, patient dose in CT depends on patient size. The purpose of this study was to introduce a method for setting size-dependent local diagnostic reference levels (LDRLs) and to evaluate these LDRLs in comparison with size-independent LDRLs and with respect to image quality. One hundred eighty-four aortic CT angiography (CTA) examinations performed on either a second-generation or third-generation dual-source CT scanner were included; we refer to the second-generation dual-source CT scanner as "CT1" and the third-generation dual-source CT scanner as "CT2." The volume CT dose index (CTDIvol) and patient diameter (i.e., the water-equivalent diameter) were retrieved by dose-monitoring software. Size-dependent DRLs based on a linear regression of the CTDIvol versus patient size were set by scanner type. Size-independent DRLs were set by the 5th and 95th percentiles of the CTDIvol values. Objective image quality was assessed using the signal-to-noise ratio (SNR), and subjective image quality was assessed using a 4-point Likert scale. The CTDIvol depended on patient size and scanner type (R2 = 0.72 and 0.78, respectively; slope = 0.05 and 0.02 mGy/mm; p < 0.001). Of the outliers identified by size-independent DRLs, 30% (CT1) and 67% (CT2) were adequately dosed when considering patient size. Alternatively, 30% (CT1) and 70% (CT2) of the outliers found with size-dependent DRLs were not identified using size-independent DRLs. A negative correlation was found between SNR and CTDIvol (R2 = 0.36 for CT1 and 0.45 for CT2). However, all outliers had a subjective image quality score of sufficient or better. We introduce a method for setting size-dependent LDRLs in CTA. Size-dependent LDRLs are relevant for assessing the appropriateness of the radiation dose for an individual patient on a specific CT scanner.

Beam-hardening in 70-kV Coronary CT angiography: Artifact reduction using an advanced post-processing algorithm

PurposeTo investigate the effect of an iterative beam-hardening correction algorithm (iBHC) on artifact reduction and image quality in coronary CT angiography (cCTA) with low tube voltage. Material and methodsThirty-six patients (17 male, mean age, 57.3 ± 14.5 years) were prospectively enrolled in this IRB-approved study and underwent 70-kV cCTA using a third-generation dual-source CT scanner. Images were reconstructed using a standard algorithm (Bv36) both with and without the iBHC technique. Several region-of-interest (ROI) measurements were performed in the inferior wall of the left ventricle (LV), an area prone to beam-hardening, as well as other myocardial regions. Coronary contrast-to-noise (CNR) and signal-to-noise ratios (SNR) were calculated. Two radiologists assessed subjective image quality. ResultsThe iBHC algorithm generally increased myocardial attenuation in all ROIs (P < 0.566); however, the increase was significantly more distinct in beam-hardening prone areas such as the inferior LV (increase, +13.9 HU, +18.6%, P < 0.001), compared to the remaining myocardium (increase, +4.4 HU, +4.5%, P < 0.003). While no significant difference was found for image noise (P < 0.092), greater CNR and SNR values for the left main coronary artery (increase, +20.7% and +17.3%, respectively) were found using the iBHC algorithm (both with P < 0.001). Subjective image quality was comparable between both image series (P = 0.217). ConclusionThe iBHC post-processing algorithm leads to significantly reduced beam-hardening while providing improved objective and equivalent subjective image quality in 70-kV cCTA.

Advanced CT acquisition protocol with a third-generation dual-source CT scanner and iterative reconstruction technique for comprehensive prosthetic heart valve assessment

ObjectivesMultidetector CT (MDCT) is a valuable tool for functional prosthetic heart valve (PHV) assessment. However, radiation exposure remains a concern. We assessed a novel CT-acquisition protocol for comprehensive PHV evaluation at limited dose.MethodsPatients with a PHV were scanned using a third-generation dual-source CT scanner (DSCT) and iterative reconstruction technique (IR). Three acquisitions were obtained: a non-enhanced scan; a contrast-enhanced, ECG-triggered, arterial CT angiography (CTA) scan with reconstructions at each 5 % of the R-R interval; and a delayed high-pitch CTA of the entire chest. Image quality was scored on a five-point scale. Radiation dose was obtained from the reported CT dose index (CTDI) and dose length product (DLP).ResultsWe analysed 43 CT examinations. Mean image quality score was 4.1±1.4, 4.7±0.5 and 4.2±0.6 for the non-contrast-enhanced, arterial and delayed acquisitions, respectively, with a total mean image quality of 4.3±0.7. Mean image quality for leaflet motion was 3.9±1.4. Mean DLP was 28.2±17.1, 457.3±168.6 and 68.5±47.2 mGy.cm for the non-contrast-enhanced (n=40), arterial (n=43) and delayed acquisition (n=43), respectively. The mean total DLP was 569±208 mGy.cm and mean total radiation dose was 8.3±3.0 mSv (n=43).ConclusionComprehensive assessment of PHVs is possible using DSCT and IR at moderate radiation dose.Key points• Prosthetic heart valve dysfunction is a potentially life-threatening condition.• Dual-source CT can adequately assess valve leaflet motion and anatomy.• We assessed a comprehensive protocol with three acquisitions for PHV evaluation.• This protocol is associated with good image quality and limited dose.

Selection of optimal tube potential settings for dual-energy CT virtual mono-energetic imaging of iodine in the abdomen

To determine the appropriate tube potential settings for dual-source, dual-energy data acquisition across a range of phantom sizes, and to determine the optimal photon energies for virtual mono-energetic imaging. Water phantoms (15-50-cm wide) containing an iodine test object were scanned on a third-generation dual-source CT scanner using all available tube potential pairs. Virtual mono-energetic images at 40, 50, 60, and 70keV were produced using Mono-energetic Plus. To determine the practical operating parameters for the evaluated CT system, data exclusions were made based on water CT number accuracy, artifacts, and using a noise constraint. Image quality metrics were measured and compared. Excluded tube potential pairs were identified; these were generally at low tube potentials for the low-energy beam and low photon energies. For non-excluded conditions, the highest CNR was obtained using the 70/150Sn setting in phantoms≤35cm at 40keV. 70/150Sn provided optimal iodine CNR below 40cm lateral phantom width at 40keV, while 90/150Sn allowed acceptable image quality in phantoms>40-cm wide at or above 60keV.

Single-energy pediatric chest computed tomography with spectral filtration at 100 kVp: effects on radiation parameters and image quality.

Most of the applied radiation dose at CT is in the lower photon energy range, which is of limited diagnostic importance. To investigate image quality and effects on radiation parameters of 100-kVp spectral filtration single-energy chest CT using a tin-filter at third-generation dual-source CT in comparison to standard 100-kVp chest CT. Thirty-three children referred for a non-contrast chest CT performed on a third-generation dual-source CT scanner were examined at 100kVp with a dedicated tin filter with a tube current-time product resulting in standard protocol dose. We compared resulting images with images from children examined using standard single-source chest CT at 100kVp. We assessed objective and subjective image quality and compared radiation dose parameters. Radiation dose was comparable for children 5years old and younger, and it was moderately decreased for older children when using spectral filtration (P=0.006). Effective tube current increased significantly (P=0.0001) with spectral filtration, up to a factor of 10. Signal-to-noise ratio and image noise were similar for both examination techniques (P≥0.06). Subjective image quality showed no significant differences (P≥0.2). Using 100-kVp spectral filtration chest CT in children by means of a tube-based tin-filter on a third-generation dual-source CT scanner increases effective tube current up to a factor of 10 to provide similar image quality at equivalent dose compared to standard single-source CT without spectral filtration.