High-pitch CT Research Articles

Simultaneous high-pitch multi-energy CT pulmonary angiography using a dual-source photon-counting-detector CT: A phantom experiment.

A dual-source CT system can be operated in a high-pitch helical mode to provide a temporal resolution of 66ms, which reduces motion artifacts in CT pulmonary angiography (CTPA). It can also be operated in a multi-energy (ME) mode to provide iodine maps, beneficial in the evaluation of pulmonary embolism (PE). No energy-integrating detector (EID) CT can perform simultaneous ME and high-pitch acquisition. This phantom study aimed to evaluate the ability of a photon-counting-detector (PCD) CT to perform simultaneous high-pitch and ME imaging for CTPA. A motion phantom was used to mimic the respiratory motion. Two tubes filled with iodine with intravascular thrombus mimicked by injecting glue within the tubes were placed along with 5, 10, and 15mg/mL iodine samples, on a motion phantom at 20 and 30 revolutions per minute. Separate high-pitch and ME EID-CT scans and a single high-pitch ME PCD scan were acquired and virtual monoenergetic images and iodine maps reconstructed. Percent thrombus occlusion was measured and compared between static and moving images. When there was motion, EID-CT ME suffered from significant motion artifacts. The measured iodine concentrations with PCD-CT in high-pitch ME were more stable when there was a motion, with a lower standard deviation than EID-CT in ME mode. The estimated percent thrombus occlusion dropped significantly with applied motion on EID-CT, while PCD-CT high-pitch ME mode showed good agreement between measurements on static or moving images. PCD-CT with combined ME and high-pitch mode facilitates simultaneous accurate iodine quantification and assessment of intravascular occlusion.

Improved Pulmonary Artery Evaluation Using High-Pitch Photon-Counting CT Compared to High-Pitch Conventional or Routine-Pitch Conventional Dual-Energy CT.

Pulmonary CT angiography (CTA) to detect pulmonary emboli can be performed using conventional dual-source CT with single-energy acquisition at high-pitch (high-pitch conventional CT), which minimizes motion artifacts, or routine-pitch, dual-energy acquisitions (routine-pitch conventional DECT), which maximize iodine signal. We compared iodine signal, radiation dose, and motion artifacts of pulmonary CTA between these conventional CT modalities and dual-source photon-counting detector CT with high-pitch, multienergy acquisitions (high-pitch photon-counting CT). Consecutive clinically indicated pulmonary CTA exams were collected. CT number/noise was measured from the main to right lower lobe segmental pulmonary arteries using 120 kV threshold low, 120 kV, and mixed kV (0.6 linear blend) images. Three radiologists reviewed anonymized, randomized exams, rating them using a 4- or 5-point Likert scale (1 = worst, and 4/5 = best) for contrast enhancement in pulmonary arteries, motion artifacts in aortic root to subsegmental pulmonary arteries, lung image quality; pulmonary blood volume (PBV) map image quality (for multienergy or dual-energy exams), and contribution to reader confidence. One hundred fifty patients underwent high-pitch photon-counting CT (n = 50), high-pitch conventional CT (n = 50), and routine-pitch conventional DECT (n = 50). High-pitch photon-counting CT had lower radiation dose (CTDIvol: 8.1 ± 2.5 vs 9.6 ± 6.8 and 16.2 ± 8.5 mGy, respectively; P < 0.001), and routine-pitch conventional DECT had significantly less contrast (P < 0.009). CT number and CNR measurements were significantly greater at high-pitch photon-counting CT (P < 0.001). Across readers, high-pitch photon-counting CT demonstrated significantly higher subjective contrast enhancement in the pulmonary arteries compared to the other modalities (4.7 ± 0.6 vs 4.4 ± 0.7 vs 4.3 ± 0.7; P = 0.011) and lung image quality (3.4 ± 0.5 vs 3.1 ± 0.5 vs 3.1 ± 0.5; P = 0.013). High-pitch photon-counting CT and high-pitch conventional CT had fewer motion artifacts at all levels compared to DECT (P < 0.001). High-pitch photon-counting CT PBV maps had superior image quality (P < 0.001) and contribution to reader confidence (P < 0.001) compared to routine-pitch conventional DECT. High-pitch photon-counting pulmonary CTA demonstrated higher contrast in pulmonary arteries at lower radiation doses with improved lung image quality and fewer motion artifacts compared to high-pitch conventional CT and routine-pitch conventional dual-energy CT.

Prospective ECG-gated High-Pitch Photon-Counting CT Angiography: Evaluation of measurement accuracy for aortic annulus sizing in TAVR planning

PurposeIn planning transcatheter aortic valve replacement (TAVR), retrospective cardiac spiral-CT is recommended to measure aortic annulus with subsequent CT-angiography (CTA) to evaluate access routes. Photon-counting detector (PCD)-CT enables to assess the aortic annulus in desired cardiac phases, using prospective ECG-gated high-pitch CTA. The aim of this study was to evaluate the measurement accuracy of aortic annulus using prospective ECG-gated high-pitch CTA against retrospective spiral-CT reference. MethodThirty patients underwent cardiac spiral-CT and prospective ECG-gated (30% R-R on aortic valve level) high-pitch CTA. Using propensity score matching, another 30 patients were identified whose CTA was performed using high-pitch mode without ECG-synchronization. Two investigators measured annular diameter, perimeter, and area on cardiac spiral-CT and high-pitch CTA. ResultsThe aortic valve was imaged in systole in 90 % of prospective ECG-gated CTA cases but only 50 % of non-ECG-gated CTA cases (p = 0.002). There was a strong correlation (r ≥ 0.94) without significant differences (p ≥ 0.09) between cardiac spiral-CT and prospective ECG-gated high-pitch CTA for all annulus measurements. In contrast, significant differences were found in annular short-axis diameter and area between cardiac spiral-CT and non-ECG-gated high-pitch CTA (p ≤ 0.03). Furthermore, prospective ECG-gated high-pitch CTA showed significantly reduced radiation exposure compared with cardiac spiral-CT (CTDI 4.52 vs. 24.10 mGy; p < 0.001). ConclusionPCD-CT-based prospective ECG-gated high-pitch scans with targeted systolic acquisition at the level of the aortic valve can simultaneously visualize TAVR access routes and accurately measure systolic annulus size. This approach could aid in optimizing protocols to achieve lower radiation doses in the growing population of younger, low-risk TAVR patients.

Highly accelerated, Dixon-based non-contrast MR angiography versus high-pitch CT angiography

ObjectivesTo compare a novel, non-contrast, flow-independent, 3D isotropic magnetic resonance angiography (MRA) sequence that combines respiration compensation, electrocardiogram (ECG)-triggering, undersampling, and Dixon water-fat separation with an ECG-triggered aortic high-pitch computed tomography angiography (CTA) of the aorta.Materials and methodsTwenty-five patients with recent CTA were scheduled for non-contrast MRA on a 3 T MRI. Aortic diameters and cross-sectional areas were measured on MRA and CTA using semiautomatic measurement tools at 11 aortic levels. Image quality was assessed independently by two radiologists on predefined aortic levels, including myocardium, proximal aortic branches, pulmonary veins and arteries, and the inferior (IVC) and superior vena cava (SVC). Image quality was assessed on a 5-point Likert scale.ResultsAll datasets showed diagnostic image quality. Visual grading was similar for MRA and CTA regarding overall image quality (0.71), systemic arterial image quality (p = 0.07–0.91) and pulmonary artery image quality (p = 0.05). Both readers favored MRA for SVC and IVC, while CTA was preferred for pulmonary veins (all p < 0.05). No significant difference was observed in aortic diameters or cross-sectional areas between native MRA and contrast-enhanced CTA (p = 0.08–0.94).ConclusionThe proposed non-contrast MRA enables robust imaging of the aorta, its proximal branches and the pulmonary arteries and great veins with image quality and aortic diameters and cross-sectional areas comparable to that of CTA. Moreover, this technique represents a suitable free-breathing alternative, without the use of contrast agents or ionizing radiation. Therefore, it is especially suitable for patients requiring repetitive imaging.

High-pitch CT pulmonary angiography (CTPA) with ultra-low contrast medium volume for the detection of pulmonary embolism: a comparison with standard CTPA

ObjectiveTo investigate the feasibility and image quality of high-pitch CT pulmonary angiography (CTPA) with reduced iodine volume in normal weight patients.MethodsIn total, 81 normal weight patients undergoing CTPA for suspected pulmonary arterial embolism were retrospectively included: 41 in high-pitch mode with 20 mL of contrast medium (CM); and 40 with normal pitch and 50 mL of CM. Subjective image quality was assessed and rated on a 3-point scale. For objective image quality, attenuation and noise values were measured in all pulmonary arteries from the trunk to segmental level. Contrast-to-noise ratio (CNR) was calculated. Radiation dose estimations were recorded.ResultsThere were no statistically significant differences in patient and scan demographics between high-pitch and standard CTPA. Subjective image quality was rated good to excellent in over 90% of all exams with no significant group differences (p = 0.32). Median contrast opacification was lower in high-pitch CTPA (283.18 [216.06–368.67] HU, 386.81 [320.57–526.12] HU; p = 0.0001). CNR reached a minimum of eight in all segmented arteries, but was lower in high-pitch CTPA (8.79 [5.82–12.42], 11.01 [9.19–17.90]; p = 0.005). Median effective dose of high-pitch CTPA was lower (1.04 [0.72–1.27] mSv/mGy·cm; 1.49 [1.07–2.05] mSv/mGy·cm; p < 0.0001).ConclusionHigh-pitch CTPA using ultra-low contrast volume (20 mL) rendered diagnostic images for the detection of pulmonary arterial embolism in most instances. Compared to standard CTPA, the high-pitch CTPA exams with drastically reduced contrast medium volume had also concomitantly reduced radiation exposure. However, objective image quality of high-pitch CTPA was worse, though likely still within acceptable limits for confident diagnosis.Clinical relevanceThis study provides valuable insights on the performance of a high-pitch dual-source CTPA protocol, offering potential benefits in reducing contrast medium and radiation dose while maintaining sufficient image quality for accurate diagnosis in patients suspected of pulmonary embolism.Key Points• High-pitch CT pulmonary angiography (CTPA) with ultra-low volume of contrast medium and reduced radiation dose renders diagnostic examinations with comparable subjective image quality to standard CTPA in most patients.• Objective image quality of high-pitch CTPA is reduced compared to standard CTPA, but contrast opacification and contrast-to-noise ratio remain above diagnostic thresholds.• Challenges of high-pitch CTPA may potentially be encountered in patients with severe heart failure or when performing a Valsalva maneuver during the examination.

Simultaneous assessment of heart and lungs with gated high-pitch ultra-low dose chest CT using artificial intelligence-based calcium scoring

PurposeThe combined testing for coronary artery and pulmonary diseases is of clinical interest as risk factors are shared. In this study, a novel ECG-gated tin-filtered ultra-low dose chest CT protocol (GCCT) for integrated heart and lung acquisition and the applicability of artificial intelligence (AI)-based coronary artery calcium scoring were assessed. MethodsIn a clinical registry of 10481 patients undergoing heart and lung CT, GCCT was applied in 44 patients on a dual-source CT. Coronary calcium scans (CCS) with 120 kVp, 100 kVp, and tin-filtered 100 kVp (Sn100) of controls, matched with regard to age, sex, and body-mass index, were retrieved from the registry (ntotal=176, 66.5 (59.4–74.0) years, 52 men). Automatic tube current modulation was used in all scans. In 20 patients undergoing GCCT and Sn100 CCS, Agatston scores were measured both semi-automatically by experts and by AI, and classified into six groups (0, <10, <100, <400, <1000, ≥1000). ResultsEffective dose decreased significantly from 120 kVp CCS (0.50 (0.41–0.61) mSv) to 100 kVp CCS (0.34 (0.26–0.37) mSv) to Sn100 CCS (0.14 (0.11–0.17) mSv). GCCT showed higher values (0.28 (0.21–0.32) mSv) than Sn100 CCS but lower than 120 kVp and 100 kVp CCS (all p < 0.05) despite greater scan length. Agatston scores correlated strongly between GCCT and Sn100 CCS in semi-automatic and AI-based measurements (both ρ = 0.98, p < 0.001) resulting in high agreement in Agatston score classification (κ = 0.97, 95% CI 0.92–1.00; κ = 0.89, 95% CI 0.79–0.99). Regarding chest findings, further diagnostic steps were recommended in 28 patients. ConclusionsGCCT allows for reliable coronary artery disease and lung cancer screening with ultra-low radiation exposure. GCCT-derived Agatston score shows excellent agreement with standard CCS, resulting in equivalent risk stratification.

Evaluation of non-breath-hold, ultra-fast, low-dose high-pitch (flash) CT scan as a practical alternative to standard spiral scan for pre-TAVI patients: a real-world single-center experience

Abstract Introduction and aim Aortic annulus dimensions change during the cardiac cycle. A retrospective ECG-gated (Spiral) scan is the default technique for pre TAVR evaluation since it includes systolic phases considered optimal for aortic annulus assessment. Ultra-fast, Low-Dose High-Pitch (FLASH) offers faster, potentially low radiation and low contrast dose scans. However, it lacks the ability to time data acquisition to the systole. Therefore, measurements derived from FLASH scan are considered suboptimal for reporting. The effect of this potential annular measurement difference on procedural success and safety was not evaluated. Therefore, we aimed to assess the feasibility and safety of FLASH vs. Spiral scan before TAVI. Methods We conducted a retrospective, single-center study. 409 patients underwent CT-TAVI scan with either FLASH or SPIRAL acquisition. Baseline characteristics, CT study, procedural and f/u data were acquired from the EMR. Outcomes defined by Valve Academic Research Consortium3 (VARC-2) endpoint definitions included in-hospital mortality, bleeding, vascular complications, acute kidney injury (AKI), conduction disorders, mechanical complications, and prosthetic aortic valve regurgitation. Composite endpoints such as device success were also examined. Results Of the 409 patients, 55.7% underwent FLASH scans. The median age was 80 years, and males accounted for 55%. The FLASH-protocol patients had higher rate of chronic kidney disease, their CT-measured aortic annulus area and diameter were smaller, and they were exposed to a smaller amount of contrast agent and radiation than the SPIRAL group. There was no statistically significant difference in primary clinical and safety endpoints between the two groups, including mechanical complications (such as annular rupture and valve malposition) and conduction disorders. Conclusions FLASH CT scan is a pragmatic and safe approach that potentially may replace spiral scan for the evaluation before TAVI procedure in the appropriate patients. Funding Acknowledgement Type of funding sources: None.

Image quality and radiation dose of dual source high pitch computed tomography in pediatric congenital heart disease

To explore the image quality and radiation dose of dual source high-pitch cardiac computed tomography with tailored contrast injection protocols for pediatric congenital heart disease patients (CHD). In total, 27 infants with CHD (median age 109 days [IQR 6–199]) were retrospectively analyzed regarding dose length product (DLP) and effective dose (ED) after undergoing cardiothoracic CT imaging. Scan parameters were adjusted on a dual source/detector CT (DSCT) to minimize radiation dose while maintaining adequate quality. Image acquisition was performed at 70% of the R–R interval. Dose reducing measures included prospective electrocardiogram gating, utilizing slow injection velocities and foregoing bolus tracking during contrast injection. Image quality was assessed for artefacts, vessel definition, and noise on a 5-point scale (1 non-diagnostic, 5 excellent). Series were scored on a 0-to-3-point scale regarding answered clinical questions (0 non-diagnostic, 3 all clinical questions could be answered). The median DLP was 5.2 mGy*cm (IQR 3.5–7.8) leading to a median ED of 0.20 mSv (IQR 0.14–0.30). On average the acquired images scored 13.3 ± 2.1 (SD) out of a maximum 15 points with an intraclass correlation coefficient (ICC) of 0.94. All acquired series were able to fully answer all clinical questions scoring maximum points (ICC 1.0). Dual source high pitch CT protocols combined with custom contrast agent injection protocols in pediatric patients with CHD delivered sufficiently high diagnostic imaging quality combined with low submilisievert radiation doses. Prospective high pitch imaging is a reliable method for depiction of cardiac anatomy even in very young pediatric CHD patients with elevated heart rates.

Systolic or diastolic CT image acquisition for transcatheter aortic valve replacement – An outcome analysis

BackgroundComputed tomography (CT) imaging is the standard of care before transcatheter aortic valve replacement (TAVR). The aortic annulus undergoes conformational changes during the heart cycle. Therefore, the image acquisition time point can impact prosthesis sizing and fit. Clinical outcome data are lacking. The aim of this study was to compare systolic and diastolic cardiac CT data acquisition with regard to procedural and clinical outcomes in patients undergoing TAVR for severe aortic stenosis (AS). MethodsPreprocedural high-pitch helical CT datasets were analyzed in 1954 patients undergoing TAVR between 2013 and 2018 ​at our center. Patients were stratified into two groups according to the acquisition heart phase (979 systolic and 975 diastolic). The study was approved by the local ethics committee. ResultsMedian age was 81.6 [interquartile range 77.5–85.8] years and 964 (49.3%) patients were male. No significant difference was found for the Valve Academic Research Consortium-3 (VARC-3) endpoints of technical failure (systolic, 5.1% vs. diastolic, 5.2%, p ​= ​0.94) or device failure (systolic, 13.7% vs. diastolic, 13.5%, p ​= ​0.92). There was no difference in paravalvular regurgitation. All-cause 30-day mortality was comparable (systolic, 3.6% [95% confidence interval, 2.4–4.7%] vs. diastolic, 3.6% [2.4–4.8%], p ​= ​1.00), while 3-year mortality rates were higher in the diastolic group (Society of Thoracic Surgeons score adjusted hazard ratio, 1.25 [1.07–1.46], p ​< ​0.01). ConclusionsWhile the 30-day technical and clinical outcomes after TAVR are comparable between systolic and diastolic CT imaging, diastolic imaging was associated with higher long-term mortality. Therefore, the data support the guideline recommendation of systolic imaging.

Non-ECG-gated high-pitch CT angiography versus hybrid ECG-gated CT angiography for aorta using 512-slice CT: comparison of image quality and radiation dose.

There have been few reports comparing image quality and radiation dose of aorta computed tomography angiography (CTA) between the high-pitch and the hybrid technique. To compare the image quality and radiation dose among non-electrocardiogram (ECG)-gated high-pitch CTA and hybrid ECG-gated CTA of the aorta using 512-slice CT. This retrospective study included 110 patients who underwent non-ECG-gated high-pitch CTA (group 1) or hybrid ECG-gated CTA (group 2) of the entire aorta. Interpretability, image noise, contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), and the mean effective radiation dose were compared. The mean image noise of the whole aorta was significantly lower (15.7 ± 1.8 HU vs. 16.5 ± 1.2 HU, P = 0.008) in group 1 than in group 2. The CNR (22.3 ± 4.7 vs. 20.0 ± 3.9, P < 0.001) and SNR (26.5 ± 4.9 vs. 23.2 ± 4.0, P < 0.001) were higher in group 2 compared with group 1. Neither group showed a significant difference in interpretability of the ascending aorta, cardiac chamber, aortic valve, right ostium, and left ostium (all P = 1). The mean effective radiation dose was significantly lower in group 1 than in group 2 (3.5 ± 0.9 mSv vs. 4.3 ± 0.8 mSv, P < 0.001). The non-ECG-gated high-pitch technique shows significantly improved CNR and SNR due to reduced noise with lower radiation exposure. The interpretability of the cardiac structure, ascending aorta, aortic valve, and both ostia did not differ significantly between the two groups.

Diagnostic Performance of a Contrast-Enhanced Ultra-Low-Dose High-Pitch CT Protocol with Reduced Scan Range for Detection of Pulmonary Embolisms

(1) Background: To evaluate the diagnostic performance of a simulated ultra-low-dose (ULD), high-pitch computed tomography pulmonary angiography (CTPA) protocol with low tube current (mAs) and reduced scan range for detection of pulmonary embolisms (PE). (2) Methods: We retrospectively included 130 consecutive patients (64 ± 16 years, 69 female) who underwent clinically indicated high-pitch CTPA examination for suspected acute PE on a 3rd generation dual-source CT scanner (SOMATOM FORCE, Siemens Healthineers, Forchheim, Germany). ULD datasets with a realistic simulation of 25% mAs, reduced scan range (aortic arch—basal pericardium), and Advanced Modeled Iterative Reconstruction (ADMIRE®, Siemens Healthineers, Forchheim, Germany) strength 5 were created. The effective radiation dose (ED) of both datasets (standard and ULD) was estimated using a dedicated dosimetry software solution. Subjective image quality and diagnostic confidence were evaluated independently by three reviewers using a 5-point Likert scale. Objective image quality was compared using noise measurements. For assessment of diagnostic accuracy, patients and pulmonary vessels were reviewed binarily for affection by PE, using standard CTPA protocol datasets as the reference standard. Percentual affection of pulmonary vessels by PE was computed for disease severity (modified Qanadli score). (3) Results: Mean ED in ULD protocol was 0.7 ± 0.3 mSv (16% of standard protocol: 4.3 ± 1.7 mSv, p < 0.001, r > 0.5). Comparing ULD to standard protocol, subjective image quality and diagnostic confidence were comparably good (p = 0.486, r > 0.5) and image noise was significantly lower in ULD (p < 0.001, r > 0.5). A total of 42 patients (32.2%) were affected by PE. ULD protocol had a segment-based false-negative rate of only 0.1%. Sensitivity for detection of any PE was 98.9% (95% CI, 97.2–99.7%), specificity was 100% (95% CI, 99.8–100%), and overall accuracy was 99.9% (95% CI, 98.6–100%). Diagnoses correlated strongly between ULD and standard protocol (Chi-square (1) = 42, p < 0.001) with a decrease in disease severity of only 0.48% (T = 1.667, p = 0.103). (4) Conclusions: Compared to a standard CTPA protocol, the proposed ULD protocol proved reliable in detecting and ruling out acute PE with good levels of image quality and diagnostic confidence, as well as significantly lower image noise, at 0.7 ± 0.3 mSv (84% dose reduction).

Pre-procedural high-pitch coronary CT angiography assessment of patients undergoing transcatheter aortic valve implantation (TAVI) without patient-specific adjustment: analysis of diagnostic performance

To evaluate the ability to assess the coronary arteries using pre-procedural computed tomography (CT; high-pitch mode) in patients referred for transcatheter aortic valve implantation (TAVI). CT and invasive coronary angiography (ICA) were performed pre-TAVI in 100 patients (46 women; 79±5.9 years). CT was performed in prospectively ECG-triggered high-pitch mode after intravenous administration of 70 ml iodinated contrast medium. Image quality was assessed using a four-point scale (graded 0-3). Significant coronary artery stenosis (≥50% diameter) was graded as either present or absent by one observer and in one-third of patients by two observers independently. ICA was the standard of reference. Results were reported per segment and per patient. Twenty-two percent of patients had known coronary artery disease (CAD). In two cases, a coronary anomaly was detected. Diagnostic image quality (grade 1-3) was achieved in 30.3% of segments. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 75%, 80.5%, 16%, and 98.5%, respectively. Significant coronary stenosis could be ruled out completely in all segments in three patients. The interrater agreement per patient was excellent (kappa=1). Relevant coronary findings can frequently be observed in high-pitch TAVI-planning CT. Despite the limitations of the technique and in patients referred to pre-TAVI evaluation (rapid heart rate, coronary calcifications, etc.), a valid evaluation of coronary arteries is possible in a considerable proportion of segments with a high NPV; however, few studies were completely free of motion artefacts to dependably exclude CAD using this technique in this challenging group of patients.

Chest CT in patients with shortness of breath: Comparing high pitch CT and conventional CT on respiratory artefacts and dose

IntroductionTo investigate chest respiratory artefact reduction using High Pitch Dual Source Computed Tomography (HPCT) compared to conventional CT (CCT) in symptomatic patients with shortness of breath. MethodsForty patients were prospectively examined on a second-generation Dual Source scanner. They were randomly divided into two groups: twenty patients underwent an experimental HPCT protocol and twenty control cases CCT protocol. Respiratory artefacts were evaluated using an ordinal score (0, 1 and 2) assigned by two readers with five and thirty years of experience. A qualitative assessment was performed using two categorical groups, group 1 = acceptable and group 2 = unacceptable. Dose Length Product (DLP) was compared. ResultsThe two groups showed a statistical difference in artefacts reduction (p < 0.0001). HPCT demonstrated no artefacts in 82% of cases, while CCT showed no artefacts in 39% of cases. DLP showed no statistical differences (p = 0.6) with mean = 266.9 for HPCT and mean = 282.65 for CCT. HPCT provides high table speed in the z-direction allowing a high temporal resolution, which reduces respiratory artefacts during free-breathing acquisition. Despite the use of two x-ray tubes, the HPCT did not increase the dose to the patient but provided the highest images quality. ConclusionsIn the emergency setting, HPCTs have been critical for achieving good image quality in uncooperative patients. Implications for practiceAcute respiratory failure is a common emergency department presentation, and the choice of high-speed acquisition CT may increase image quality.

Low-Dose High-Pitch Cardiac CT to Evaluate Abnormal Pacemaker Lead Position

Displacement of a cardiac pacemaker lead or myocardial perforation by a lead is an infrequent complication of pacemaker implantation. While standard cardiac CT is useful for diagnosing such complications when routine examinations can not, the potential risks associated with exposure to the high doses of radiation used in CT are of concern. Here, we report three cases in which pacemaker lead displacement or myocardial perforation was definitively diagnosed by low-dose cardiac CT used in the high-pitch spiral mode, when other more routine examinations failed to suggest their occurrence. The mean dose of radiation used for definitively diagnosing the three patients was relatively low (2.19 mSv).

Third-generation iterative reconstruction on a dual-source, high-pitch, low-dose chest CT protocol with tin filter for spectral shaping at 100kV: a study on a small series of COVID-19 patients.

ObjectivesTo investigate the role of third-generation iterative reconstruction (ADMIRE) in dual-source, high-pitch chest CT protocol with spectral shaping at 100 kVp in Coronavirus disease 2019 (COVID-19).MethodsConfirmed COVID-19 inpatients undergoing to unenhanced chest CT were scanned with a dual-energy acquisition (DECT, 90/150Sn kV) and a dual-source, high-pitch acquisition with tin-filtered 100 kVp (LDCT). On the DECT with ADMIRE 3 (DECT3) were evaluated the pulmonary findings and their extension (25-point score). Two radiologists in consensus evaluated with 5-point scales the overall image quality, the anatomical structures, and the elementary findings on LDCT reconstructed with filtered backprojection (LDCT0), with ADMIRE 3 (LDCT3) and 5 (LDCT5), and on DECT3. The signal-to-noise ratio (SNR), the body mass index, the exposure times, and the radiation doses were recorded.ResultsSeventy-five patients (57 M/18F; median age: 63 y.o.) were included, with median pulmonary extension of 13/25 points. The imaging findings were detected in proportion comparable to the available literature. The ADMIRE significantly improved the SNR in LDCT (p < 0.00001) with almost no significant differences in overweight patients. The LDCT had median effective dose of 0.39 mSv and acquisition time of 0.71 s with significantly less motion artifacts than DECT (p < 0.00001). The DECT3 and LDCT3 provided the best image quality and depiction of pulmonary anatomy and imaging findings, with significant differences among all the series (p < 0.00001).ConclusionThe LDCT with spectral shaping and ADMIRE3 provided acceptable image quality in the evaluation of patients with COVID-19, with significantly reduced radiation dose and motion artifacts.

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.

High-pitch dual-source CT for coronary artery calcium scoring: A head-to-head comparison of non-triggered chest versus triggered cardiac acquisition

BackgroundTo determine the effect of low-dose, high-pitch non-electrocardiographic (ECG)-triggered chest CT on coronary artery calcium (CAC) detection, quantification and risk stratification, compared to ECG-triggered cardiac CT. MethodsWe selected 1,000 participants from the ImaLife study, 50% with coronary calcification on cardiac CT. All participants underwent non-contrast cardiac CT followed by chest CT using third-generation dual-source technology. Reconstruction settings were equal for both acquisitions. CAC scores were determined by Agatston's method, and divided dichotomously (0, >0), and into risk categories (0, 1–99, 100–399, ≥400). We investigated the influence of heart rate and body mass index (BMI) on risk reclassification. ResultsPositive CAC scores on cardiac CT ranged from 1 to 6926 (median 39). Compared to cardiac CT, chest CT had sensitivity of 0.96 (95%CI 0.94–0.98) and specificity of 0.99 (95%CI 0.97–0.99) for CAC detection (κ = 0.95). In participants with coronary calcification on cardiac CT, CAC score on chest CT was lower than on cardiac CT (median 30 versus 40, p˂0.001). Agreement in CAC-based risk strata was excellent (weighted κ = 0.95). Sixty-five cases (6.5%) were reclassified by one risk category in chest CT, with fifty-five (84.6%) shifting downward. Higher BMI resulted in higher reclassification rate (13% for BMI ≥30 versus 5.2% for BMI <30, p = 0.001), but there was no effect of heart rate. ConclusionLow-dose, high-pitch chest CT, using third-generation dual-source technology shows almost perfect agreement with cardiac CT in CAC detection and risk stratification. However, low-dose chest CT mainly underestimates the CAC score as compared to cardiac CT, and results in inaccurate risk categorization in BMI ≥30.

Retrospectively ECG-gated helical vs. non-ECG-synchronized high-pitch CTA of the aortic root for TAVI planning.

BackgroundMultidetector computed tomography (MDCT) plays a key role in patient assessment prior to transcatheter aortic valve implantation (TAVI). However, to date no consensus has been established on what is the optimal pre-procedural imaging protocol. Variability in pre-TAVI acquisition protocols may lead to discrepancies in aortic annulus measurements and may potentially influence prosthesis size selection.PurposeThe current study evaluates the magnitude of differences in aortic annulus measurements using max-systolic, end-diastolic, and non-ECG-synchronized imaging, as well as the impact of method on prosthesis size selection.Material and methodsFifty consecutive TAVI-candidates, who underwent retrospectively-ECG-gated CT angiography (CTA) of the aortic root, directly followed by non-ECG-synchronized high-pitch CT of the entire aorta, were retrospectively included. Aortic root dimensions were assessed at each 10% increment of the R-R interval (0–100%) and on the non-ECG-synchronized scan. Dimensional changes within the cardiac cycle were evaluated using a 1-way repeated ANOVA. Agreement in measurements between max-systole, end-diastole and non-ECG-synchronized scans was assessed with Bland-Altman analysis.ResultsMaximal dimensions of the aortic root structures and minimum annulus-coronary ostia distances were measured during systole. Max-systolic measurements were significantly and substantially larger than end-diastolic (p<0.001) and non-ECG-synchronized measurements (p<0.001). Due to these discrepancies, the three methods resulted in the same prosthesis size selection in only 48–62% of patients.ConclusionsThe systematic differences between max-systolic, end-diastolic and non-ECG-synchronized measurements for relevant aortic annular dimensions are both statistically significant and clinically relevant. Imaging strategy impacts prosthesis size selection in nearly half the TAVI-candidates. End-diastolic and non-ECG-synchronized imaging does not provide optimal information for prosthesis size selection. Systolic image acquisition is necessary for assessment of maximal annular dimensions and minimum annulus-coronary ostia distances.

Radiation dose and image quality of high-pitch emergency abdominal CT in obese patients using third-generation dual-source CT (DSCT)

In this third-generation dual-source CT (DSCT) study, we retrospectively investigated radiation dose and image quality of portal-venous high-pitch emergency CT in 60 patients (28 female, mean age 56 years) with a body mass index (BMI) ≥ 30 kg/m2. Patients were dichotomized in groups A (median BMI 31.5 kg/m2; n = 33) and B (36.8 kg/m2; n = 27). Volumetric CT dose index (CTDIvol), size-specific dose estimate (SSDE), dose length product (DLP) and effective dose (ED) were assessed. Contrast-to-noise ratio (CNR) and dose-independent figure-of-merit (FOM) CNR were calculated. Subjective image quality was assessed using a five-point scale. Mean values of CTDIvol, SSDE as well as normalized DLP and ED were 7.6 ± 1.8 mGy, 8.0 ± 1.8 mGy, 304 ± 74 mGy * cm and 5.2 ± 1.3 mSv for group A, and 12.6 ± 3.7 mGy, 11.0 ± 2.6 mGy, 521 ± 157 mGy * cm and 8.9 ± 2.7 mSv for group B (p < 0.001). CNR of the liver and spleen as well as each calculated FOM CNR were significantly higher in group A (p < 0.001). Subjective image quality was good in both groups. In conclusion, third-generation abdominal high-pitch emergency DSCT yields good image quality in obese patients. Radiation dose increases in patients with a BMI > 36.8 kg/m2.

1336Outcome analysis of systolic or diastolic CT acquisition prior to transcatheter aortic valve replacement to estimate prothesis size

Abstract Background Computed tomography (CT) imaging is considered as standard of care for transcatheter aortic valve replacement (TAVR) prothesis sizing. ECG-triggered high-pitch helical CT data acquisition on dual-source CT systems is associated with less contrast volumes, but CT image reconstruction of the aortic valve is limited to a single time point within the cardiac cycle. Although systolic CT imaging of the aortic valve is recommended due to the changes in aortic annulus area during the cardiac cycle, this recommendation is not supported by clinical outcome data. Purpose The study aimed to assess the impact of systolic vs. diastolic CT imaging of the aortic annulus for TAVR sizing on patient outcomes in a large series of patients. Methods In the study CT images of 1346 patients undergoing TAVR at our centre from 2013–2016 were re-evaluated. Patients were stratified into two groups with 0–35% and 36–99% of the RR-interval as systolic and diastolic CT imaging. Outcomes according to VARC2-criteria at 30 days and long-term survival were analysed. Results CTs of 1135 out of 1346 patients were analysed retrospectively, 278 (24.5%) of which were acquired during systole and 859 (75.5%) during diastole. Mean age was 80.6±7.6 years and 52.2% were female. Mean follow-up, available for 83.4% of patients, was 2.1±0.8 years. No significant difference in baseline characteristics was observed across both groups. Aortic annular area measurements were significantly larger in systole (mean aortic anulus area: systole: 4.8±1.0 cm2; diastole: 4.5±1.0 cm2, p&lt;0.01), resulting in larger implanted valves. Balloon-expandable valves were used in 69.4% of patients; the need for post-dilation did not differ between both groups (systole 4.7%, and diastole 7.5%; p=0.13). There was no difference between groups concerning the combined endpoints for device success or early safety according to VARC2-criteria. Overall 30-day mortality was 3.4% (systole: 4.2% and diastole: 3.1%, p=0.35). Device failure occurred in 2.7% (systole: 2.9% and diastole: 2.7%, p=0.83). Permanent pacemaker implantation was required in 20.1% (systole: 18.7%, and diastole: 20.5%; p=0.55). Stroke rate at 30 days was 2.9%, n=33 and was similar in the two groups. The landmark analysis demonstrates the 30-day and 1-year mortality rates for both groups (Figure). Figure 1. Landmark analysis mortality Conclusion The current analysis does not suggest that systolic CT imaging for TAVR sizing is associated with improved early or late outcomes. Accordingly, full-cycle CT imaging which usually is associated with higher contrast volumes, should be avoided in this elderly population, which often presents with reduced kidney function.