Halved contrast medium dose coronary dual-layer CT-angiography - phantom study of tube current and patient characteristics.

Virtual mono-energetic images (VMI) using dual-layer computed tomography (DLCT) enable substantial contrast medium (CM) reductions. However, the combined impact of patient size, tube voltage, and heart rate (HR) on VMI of coronary CT angiography (CCTA) remains unknown. This phantom study aimed to assess VMI levels achieving comparable contrast-to-noise ratio (CNR) in CCTA at 50% CM dose across varying tube voltages, patient sizes, and HR, compared to the reference protocol (100% CM dose, conventional at 120 kVp). A 5 mm artificial coronary artery with 100% (400 HU) and 50% (200 HU) iodine CM-dose was positioned centrally in an anthropomorphic thorax phantom. Horizontal coronary movement was matched to HR (at 0, < 60, 60-75, > 75 bpm), with varying patient sizes simulated using phantom extension rings. Raw data was acquired using a clinical CCTA protocol at 120 and 140 kVp (five repetitions). VMI images (40-70 keV, 5 keV steps) were then reconstructed; non-overlapping 95% CNR confidence intervals indicated significant differences from the reference. Higher CM-dose, reduced VMI, slower HR, higher tube voltage, and smaller patient sizes demonstrated a trend of higher CNR. Regardless of HR, patient size, and tube voltage, no significant CNR differences were found compared to the reference, with 100% CM dose at 60 keV, or 50% CM dose at 40 keV. DLCT reconstructions at 40 keV from 120 to 140 kVp acquisitions facilitate 50% CM dose reduction for various patient sizes and HR with equivalent CNR to conventional CCTA at 100% CM dose, although clinical validation is needed.

The sub-millisievert era in CTCA: the technical basis of the new radiation dose approach.

Computed tomography coronary angiography (CTCA) has become a cornerstone in the diagnostic process of the heart disease. Although the cardiac imaging with interventional procedures is responsible for approximately 40% of the cumulative effective dose in medical imaging, a relevant radiation dose reduction over the last decade was obtained, with the beginning of the sub-mSv era in CTCA. The main technical basis to obtain a radiation dose reduction in CTCA is the use of a low tube voltage, the adoption of a prospective electrocardiogram-triggering spiral protocol and the application of the tube current modulation with the iterative reconstruction technique. Nevertheless, CTCA examinations are characterized by a wide range of radiation doses between different radiology departments. Moreover, the dose exposure in CTCA is extremely important because the benefit-risk calculus in comparison with other modalities also depends on it. Finally, because anatomical evaluation not adequately predicts the hemodynamic relevance of coronary stenosis, a low radiation dose in routine CTCA would allow the greatest use of the myocardial CT perfusion, fractional flow reserve-CT, dual-energy CT and artificial intelligence, to shift focus from morphological assessment to a comprehensive morphological and functional evaluation of the stenosis. Therefore, the aim of this work is to summarize the correct use of the technical basis in order that CTCA becomes an established examination for assessment of the coronary artery disease with low radiation dose.

Assessment of Semi-automated Computed Tomographic Measures of Segmental Perfusion Defects in a Swine Model (Sus scrofa) of Intermediate Coronary Lesions.

Computed tomographic myocardial perfusion (CTP) imaging is a tool that shows promise in emergent settings for defining the hemodynamic significance of coronary artery disease. In this study, we examined the accuracy with which the transmural perfusion ratio (TPR) derived through semiautomated CTP analysis reflected segmental perfusion defects associated with intermediate coronary artery lesions in swine. Lesions (diameter stenosis, 65% ± 11%) of the left anterior descending coronary artery (LAD) were created in 10 anesthetized female swine (weight, 47.5 ± 1.9 kg) by using a pneumatic occlusion device implanted on the LAD. Occluder inflation pressures were adjusted to maintain fractional flow reserve (FFR, 74.3 ± 1.7) during adenosine infusion (140ug/kg/min). Static CTP imaging using a stress-rest protocol and segmental TPR derived from semiautomated CT perfusion software was compared with microsphere-derived TPR (mTPR) by using a 16-segment model and polar mapping. Intermediate LAD stenosis was verified through multiplanar coronary CT angiography. Receiver operating characteristic analysis identified an optimal threshold for segmental perfusion defects for intermediate lesions (TPR threshold, ≤0.80); however, the area under the receiver operating characteristic curve was 0.58, and the overall accuracy was 63%. At this threshold, the sensitivity and specificity were 65% and 61%, and the positive and negative predictive values were 61% and 65%, respectively. Although CTP-TPR illustrated segmental perfusion defects with intermediate lesions, the disparity between CTP-TPR and mTPR measures of segmental perfusion suggests that further advances in analysis software may be necessary to improve the localization of segmental defects for intermediated lesions.

Acquisition time, radiation dose, subjective and objective image quality of dual-source CT scanners in acute pulmonary embolism: a comparative study.

OBJECTIVES: To compare the scan acquisition time, radiation dose, subjective and objective image quality of two dual-source CT scanners (DSCT) for detection of acute pulmonary embolism. METHODS: Two hundred twenty-one scans performed on the 2nd-generation DSCT and 354 scans on the 3rd-generation DSCT were included in this large retrospective study. In a randomized blinded design, two radiologists independently reviewed the scans using a 5-point Likert scale. Radiation dose and objective image quality parameters were calculated. RESULTS: Mean acquisition time was significantly lower in the 3rd-generation DSCT (2.81 s ± 0.1 in comparison with 9.7 s ± 0.15 [mean ± SD] respectively; p < 0.0001) with the 3rd generation 3.4 times faster. The mean subjective image quality score was 4.33/5 and 4/5 for the 3rd- and 2nd-generation DSCT respectively (p < 0.0001) with strong interobserver reliability agreement. DLP, CTDIvol, and ED were significantly lower in the 3rd than the 2nd generation (175.6 ± 63.7 mGy cm; 5.3 ± 1.9 mGy and 2.8 ± 1.2 mSv in comparison with 266 ± 255 mGy.cm; 7.8 ± 2.2 mGy and 3.8 ± 4.3 mSv). Noise was significantly lower in the 3rd generation (p < 0.01). Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and figure of merit (FOM), a dose-insensitive index for CNR, were significantly higher in the 3rd-generation DSCT (33.5 ± 23.4; 29.0 ± 21.3 and 543.7 ± 1037 in comparison with 23.4 ± 17.7; 19.4 ± 16.0 and 170.5 ± 284.3). CONCLUSION: Objective and subjective image quality are significantly higher on the 3rd-generation DSCT with significantly lower mean acquisition time and radiation dose. KEY POINTS: • The 3rd-generation DSCT scanner provides an improved image quality, less perceived artifacts, and lower radiation dose in comparison with the 2nd-generation DSCT, when operating in dual-energy (DE) mode. • The 3.4-times-faster 3rd-generation DSCT scanner can be of particular value in patients with chronic lung diseases or breathing difficulties that prevent adequate breathhold.

Catheter-Directed Computed Tomography Hepatic Angiography for Yttrium-90 Selective Internal Radiotherapy of Hepatocellular Carcinoma Reduces Prophylactic Embolization of Extrahepatic Vessels.

OBJECTIVES: To determine the rate of prophylactic embolization of extrahepatic vessels in patients undergoing yttrium-90 selective internal radiotherapy (90Y SIRT) for hepatocellular carcinoma (HCC) with the use of catheter-directed computed tomography hepatic angiography (CD-CTHA). MATERIALS AND METHODS: This retrospective study included 186 HCC patients who received 90Y SIRT from May 2010 to June 2015 in a single institution. All procedures were performed in a hybrid angiography-CT suite equipped with digital subtraction angiography (DSA) and CD-CTHA capabilities. CD-CTHA was performed during pre-treatment hepatic angiography. 90Y SIRT was administered approximately 2 weeks later. Selective prophylactic embolization of extrahepatic vessels was performed if extrahepatic enhancement was seen on CD-CTHA or if an extrahepatic vessel opacified on DSA/CD-CTHA despite the final microcatheter position for 90Y microsphere delivery being beyond the origin of this vessel. RESULTS: Thirty-five patients (18.8%) required selective embolization of extrahepatic vessels. Technical success of 90Y SIRT was 99.5%. Two patients (1.1%) developed radiation-induced gastrointestinal ulceration, and one (0.54%) developed radiation-induced pneumonitis. Extrahepatic uptake of 90Y microspheres was seen in the gallbladder of one patient without significant complications. CONCLUSION: The use of CD-CTHA in 90Y SIRT of HCC was associated with a low rate of prophylactic embolization of extrahepatic vessels while maintaining a high technical success rate of treatment and low rate of complications. LEVEL OF EVIDENCE: Level 4, case series.

A new option using adjunctive microsheath angiography to increase the safety during percutaneous endovascular aortic aneurysm repair.

BACKGROUND: Percutaneous endovascular aortic repair (PEVAR) is widespread for the treatment of abdominal aortic aneurysm (AAA). The purpose of this study was to present outcomes of PEVAR using simultaneous angiography via microsheath. METHODS: There were 100 punctures in 50 patients undergoing PEVAR for AAA. All cases used the ProGlide closure device (Abbot Vascular, Santa Clara, CA, USA) for PEVAR, and another puncture with microsheath placed on the common femoral artery for a second insertion point of the ProGlide. Basically, a single ProGlide was used for each puncture in the PEVAR. Hemostasis, stenosis, dissection, and distal embolization were confirmed in angiography via the adjunctive microsheath after removal of the delivery system. Since the PEVAR for AAA requires at least two punctures, this procedure was applied to both sites. Primary outcome was technical success and occurrence rates of access-related complications in PEVAR. Technical success was defined as complete hemostasis without surgical intervention and the need for conversion to general anesthesia. RESULTS: Technical success was achieved in 98% (98/100) of the cases. Access-related complications on perioperative periods were identified in two cases. One case involved a tip of the microsheath being transected by the ProGlide that led to a distal embolization, which is why a cut down was required to retrieve the tip of the sheath. Another case required a cut down due to persistent hemorrhage from the puncture site of the microsheath. Although persistent hemorrhage was identified in five punctures (5.0%) via the adjunctive microsheath angiography, additional manual compression or ProGlide achieved complete hemostasis. Both stenosis and dissection following PEVAR were not identified in any case. CONCLUSIONS: A supporting angiography via microsheath in confirming the absence of hemorrhage, stenosis, dissection, and distal embolization may be worthwhile to selectively use for cases of PEVAR.

Microcatheter shaping using three-dimensional printed models for intracranial aneurysm coiling.

BACKGROUND AND PURPOSE: Microcatheterization is an important, but also difficult, technique used for the embolization of intracranial aneurysms. The purpose of this study was to investigate the application of three-dimensional (3D) printing technology in microcatheter shaping. METHODS: Nine cases of internal carotid artery posterior communicating artery aneurysm diagnosed by CT angiography were selected, and 3D printing technology was used to build a 3D model including the aneurysm and the parent artery. The hollow and translucent model had certain flexibility; it was immersed in water and the microcatheter was introduced into the water to the target position in the aneurysm, followed by heating the water temperature to 50°C. After soaking for 5 min, the microcatheter was taken out and the shaping was completed. After sterilization, the shaped microcatheter was used for arterial aneurysm embolization and evaluation was conducted. RESULTS: Nine cases of microcatheter shaping were satisfactory and shaping the needle was not necessary; no rebound was observed. The microcatheter was placed in an ideal position, and the stent-assisted method was used in three cases of wide-neck aneurysm. There were no complications related to surgery. CONCLUSION: A new microcatheter shaping method using 3D printing technology makes intracranial artery aneurysm embolization more stable and efficient.

Interpretability of coronary CT angiography performed with a novel whole-heart coverage high-definition CT scanner in 300 consecutive patients with coronary artery bypass grafts.

AIMS: Coronary CT angiography (CCTA) is an accurate non-invasive tool for the evaluation of coronary artery bypass graft (CABG). However, inability to sustain a long breath-hold, high heart rate (HR) and atrial fibrillation may affect image quality. Moreover, radiation exposure is still a matter of some concern. A scanner combining 0.23-mm spatial resolution, new iterative reconstruction and fast gantry rotation time has been recently introduced in the clinical field. The aims of our study were to evaluate interpretability, radiation exposure and diagnostic accuracy of CCTA performed with the latest generation of cardiac-CT scanners compared to invasive coronary angiography (ICA) in the assessment of bypass grafts, and non-grafted and post-anastomotic native coronary arteries. METHODS AND RESULTS: We prospectively enrolled 300 patients undergoing clinically indicated CCTA with a 16-cm z-axis coverage, 256-detector rows, and 0.28-sec gantry rotation time scanner. Coronary artery and graft interpretability, image quality and effective dose (ED) were assessed in all patients and diagnostic accuracy was evaluated in a subgroup of 100 patients who underwent ICA. Mean HR during the scan was 69.6 ±â€¯10.8. Sinus rhythm was present in 118 patients with HR < 75 bpm and in 112 patients with HR ≥ 75 bpm, while 70 patients had atrial fibrillation. CABG interpretability was 100%. Compared to ICA, CCTA was able to correctly detecting occlusions or significant stenoses of all CABG segments. Overall interpretability of native coronary segments was 95.6%. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy of coronary arteries were 98.3%, 97.4%, 93.1%, 99.3% and 96.5%, respectively. The diagnostic accuracy in a patient based analysis was 95.2%. Mean ED was 3.14 ±â€¯1.7 mSv. CONCLUSIONS: The novel whole-heart coverage CT scanner allows to evaluating CABG and native coronary arteries with excellent interpretability and low radiation exposure even in the presence of unfavorable heart rhythm.

A comparative study of radiation doses between phantom and patients via CT angiography of the intra-/extra-cranial, pulmonary, and abdominal/pelvic arteries.

This study aimed to evaluate effective dose and size-specific dose estimate (SSDE) of computed tomography angiography (CTA) examination using an anthropomorphic phantom. We included three CTA examination protocols to evaluate the intra- and extra-cranial arteries, pulmonary artery (CTPA), and abdominal vessels. Patient SSDEs were measured retrospectively to estimate patient dose, relative to the bodyweight of the patient and volume CT dose index (CTDIvol). Our findings revealed that the highest dose was absorbed by the left lobe of the thyroid gland during intra-/extra-cranial CTA and CTPA, that is, 14.11 ± 0.24 mGy and 16.20 ± 3.95 mGy, respectively. However, the highest absorbed dose in abdominal/pelvic CTA was the gonads (8.98 ± 0.30 mGy), while other radiosensitive organs in intra- and extra-cranial CTA, CTPA, and abdominal/pelvic CTA did not demonstrate significant differences between organs/structures with p value 0.88, 0.11, and 0.54, respectively. The estimated effective dose in intra-/extra-cranial CTA was lower in patients (0.80 ± 0.60 mSv) than in the phantom (0.83 mSv), but it was the opposite for CTPA, with the effective dose being higher in patients (7.54 ± 3.09 mSv) than in the phantom (6.68 mSv). Similar to the effective dose, only CTPA SSDEs were significantly higher in men than in women (19.74 ± 4.79 mGy versus 7.9 mGy). Effective dose and SSDE are clinically relevant parameters that can help estimate a more accurate patient dose based on a patient's size.

Radiation exposure related to cardiovascular CT examination: comparison between conventional 64-MDCT and third-generation dual-source MDCT.

PURPOSE: To compare radiation exposure associated with daily practice cardiovascular (CV) examinations performed on two different multidetector computed tomography (MDCT) scanners, a conventional 64-MDCT and a third-generation dual-source (DS) MDCT. MATERIALS AND METHODS: In this retrospective study, 1458 patients who underwent CV examinations between January 2017 and August 2018 were enrolled. A single-source 64-MDCT (Lightspeed VCT, GE) scan was performed in 705 patients from January to August 2017 (207 coronary examinations and 498 vascular examinations) and 753 patients underwent third-generation 192 × 2-DSCT (Somatom FORCE, Siemens) scan from January to August 2018 (302 coronary examinations and 451 vascular examinations). Volume CT dose index (CTDIvol), dose length product (DLP), effective dose (ED), tube voltage (TV) and exposure time (ET), pitch factor (PF) were registered for each patient. Student's t test was used to compare mean values between each corresponding group of MDCT and DSCT. RESULTS: In coronary examinations with DSCT, CTDIvol was 24.4% lower (23.1 mGy vs 30.6 mGy, p < 0.0001) and DLP and ED reductions were 35.6% than with MDCT (465.0 mGy * cm vs 732.3 mGy * cm and 6.5 mSv and 10.3 mSv; vs p < 0.0001). Concerning scan parameters, kVp and ET reductions were 12.7% and 69.4%, respectively (p < 0.0001); PF increase was 73.8% (p < 0.0001). In all vascular studies, DSCT, compared with MDCT, permitted to reduce CTDIvol from 43.5 to 70.6%; DLP and ED reductions were from 50.3 to 73.1%; kVp and ET decreases were from 10.7 to 32.5% and from 26.3 to 68.7%. PF increase was from 16.7 to 58.1% (all differences with p < 0.0001). CONCLUSIONS: In daily practice, CV examinations CTDI, DLP, ED, ET and TV were lower and PF was higher with 192 × 2-DSCT compared to 64-MDCT.

A comparison study of radiation effective dose in ECG-Gated Coronary CT Angiography and calcium scoring examinations performed with a dual-source CT scanner.

In this report we have evaluated radiation effective dose received by patients during ECG-gated CCTA examinations based on gender, heart rate, tube voltage protocol and body mass index (BMI). A total of 1,824 patients were retrospectively recruited (1,139 men and 685 women) and they were divided into Group 1 (CCTA with calcium scoring), Group 2 (CCTA without calcium scoring) and Group 3 (only calcium scoring), where the association between gender, heart rate, tube voltage protocol and body mass index (BMI) were analysed. Examinations were performed using a retrospective ECG-gated CCTA protocol and the effective doses were calculated from the dose length product with a conversion coefficient of 0.026 mSv.mGy-1cm-1. No significant differences were observed in the mean effective dose between gender in all groups. The mean estimated dose was significantly higher when the heart rate was lower in Group 1 (p < 0.001) and Group 2 (p = 0.002). There were also significant differences between the mean effective dose in tube voltage protocol and BMI among the three groups. The mean effective dose was positively correlated with BMI (p < 0.001), but inversely related to the heart rate. This study supported the theory that a high heart rate, low tube voltage and low BMI could significantly reduce radiation dose exposure.

Advanced CT Techniques for Decreasing Radiation Dose, Reducing Sedation Requirements, and Optimizing Image Quality in Children.

CT is an invaluable diagnostic tool for pediatric patients; however, concerns have arisen about the potential risks of ionizing radiation associated with diagnostic imaging in young patients, particularly for pediatric populations that may require serial CT examinations. Recent attention has also been focused on the immediate and long-term risks of administration of anesthetic medications to infants and young children who require sedation to undergo imaging examinations. These concerns can be mitigated with use of advanced CT techniques that can decrease scan time and radiation dose while preserving image quality. In this article, current state-of-the-art CT acquisition techniques are reviewed as part of a comprehensive strategy to reduce radiation dose, decrease sedation needs, and optimize image quality in infants and young children. Three imaging strategies are discussed, including (a) dual-energy CT (DECT), (b) imaging with a low tube potential, and (c) rapid scanning. Consolidating multiphase imaging protocols into a single phase with virtual nonenhanced imaging on DECT scanners, as well as use of low tube voltage, can reduce the radiation dose while increasing the conspicuity of contrast material-enhanced structures with a reduced volume of iodinated contrast material and a reduced rate of injection. Rapid scanning techniques with either ultrahigh pitch at dual-source CT or with wide-area detector single-source CT facilitate scanning without the need for sedation in many children. ©RSNA, 2019 See discussion on this article by Szczykutowicz .

Single- and dual-energy CT pulmonary angiography using second- and third-generation dual-source CT systems: comparison of radiation dose and image quality.

OBJECTIVES: To evaluate radiation exposure and image quality in matched patient cohorts for CT pulmonary angiography (CTPA) acquired in single- and dual-energy mode using second- and third-generation dual-source CT (DSCT) systems. METHODS: We retrospectively included 200 patients (mean age, 65.5 years ± 15.7 years) with suspected pulmonary embolism-equally divided into four study groups (n = 50) and matched by gender and body mass index. CTPA was performed with vendor-predefined second-generation (group A, 100-kV single-energy computed tomography (SECT); group B, 80/Sn140-kV dual-energy computed tomography (DECT)) or third-generation DSCT (group C, 100-kV SECT; group D, 90/Sn150-kV DECT) devices. Radiation metrics were assessed using a normalized scan range of 27.5 cm. For objective image quality evaluation, dose-independent figure-of-merit (FOM) contrast-to-noise ratios (CNRs) were calculated. Subjective image analysis included ratings for overall image quality, reader confidence, and image artifacts using five-point Likert scales. RESULTS: Calculations of the effective dose (ED) of radiation for a normalized scan range of 27.5 cm showed nonsignificant differences between SECT and DECT acquisitions for each scanner generation (p ≥ 0.253). The mean effective radiation dose was lower for third-generation groups C (1.5 mSv ± 0.8 mSv) and D (1.4 mSv ± 0.7 mSv) compared to second-generation groups A (2.5 mSv ± 0.9 mSv) and B (2.3 mSv ± 0.6 mSv) (both p ≤ 0.013). FOM-CNR measurements were highest for group D. Qualitative image parameters of overall image quality, reader confidence, and image artifacts showed nonsignificant differences among the four groups (p ≥ 0.162). CONCLUSIONS: Third-generation DSCT systems show lower radiation dose parameters for CTPA compared to second-generation DSCT. DECT can be performed with both scanner generations without radiation dose penalty or detrimental effects on image quality compared to SECT. KEY POINTS: • Radiation exposure showed nonsignificant differences between SECT and DECT for both DSCT scanner devices. • Dual-energy CTPA provides equivalent image quality compared to standard image acquisition. • Subjective image quality assessment was similar among the four study groups.

Comparison of Whole Heart Computed Tomography Scanners for Image Quality Lower Radiation Dosing in Coronary Computed Tomography Angiography: The CONVERGE Registry.

RATIONALE AND OBJECTIVES: Novel technology in coronary computed tomographic angiography allows assessment of coronary artery disease with high image quality (IQ). There are currently two wide detector "whole heart" coverage scanners available, which avoid misregistration artifacts. However, there are no data directly comparing IQ between the two scanners. The aim of the current study is to investigate if IQ is different between the most scanners of GE and Toshiba broad detector scanners. MATERIALS AND METHODS: Prospective, observational, multicenter international cohort study comparing 236 consecutive patients who underwent coronary computed tomographic angiography using whole-heart scanners; 126 patients on scanner S1 ( Aquilion ONE Vision, Toshiba), and 110 patients on scanner S2 (Revolution CT, GE Healthcare). Hounsfield units were measured using regions of interest in the descending aorta at 6 points (cranial slice, level of the visualized first, second, third, and fourth spines, and the caudal slice). We also compared the coverage length (z-axis) of the full width field of view between a single rotation of the two scanners. RESULTS: Evaluating mean CT attenuation values Hounsfield units through the scan range, are progressively reduced across the descending aorta in the S1 group, resulting in the larger difference of contrast brightness between the cranial and caudal slices compared to the S2 group (absolute difference: S2 13.0 ± 4.4 vs S1 141.9 ± 16.4, p < 0.0001; Percent difference: 19.3 ± 2.1 vs -3.4 ± 1.2, <0.0001). The standard deviation (SD) is similar at the cranial slice between the two scanners, however, the S1 group demonstrated higher SD-differential from cranial to caudal than S2 group. Median radiation exposure was significantly lower for the S2 scanner 1.50 ± 0.75 mSv vs the S1 system 1.9 mSv (IQR 1.7-2.7 mSv) (p = 0.01). Z-axis coverage was larger for the S2 scanner 152.5 mm (244 slices × 0.625 mm/slice) than 133 mm for S1 (266 slices × 0.5 mm/slice). CONCLUSION: Although both "volume" scanners cover the whole heart z-axis with one beat, scans using the S1 scanner have a larger variability in attenuation values throughout the scan range, resulting in 20% increase in nonuniformity from cranial to caudal slice. Additionally, SD variation across the field of view, a metric of noise, is larger when using the S1 scanner vs the S2 scanner. These results indicate that the GE Revolution CT has more uniform contrast enhancement and more coverage, lower radiation and lower image noise compared to the Toshiba Aquilion ONE Vision system.

Submillisievert CT angiography for carotid arteries using wide array CT scanner and latest iterative reconstruction algorithm in comparison with previous generations technologies: Feasibility and diagnostic accuracy.

OBJECTIVES: To assess evaluability and diagnostic accuracy of a low dose CT angiography (CTA) protocol for carotid arteries using latest Iterative Reconstruction (IR) algorithm in comparison with standard 100 kVp protocol using previous generation CT and IR. MATERIALS AND METHODS: 105 patients, referred for CTA of the carotid arteries were prospectively enrolled in our study and underwent CTA with 80 kVp and latest IR algorithm (group 1). Data were retrospectively compared with 100 consecutive patients with similar examination indications that had previously undergone CTA of carotid arteries with a standard 100 kVp protocol and a first generation IR algorithm (group 2). Image quality was evaluated with a 4-point Likert-scale. For each exam CT number, image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) at level of common carotid artery (CCA), internal carotid artery (ICA) and at level of Circle of Willis and Effective Dose (ED) were evaluated. 62 Group 1 patients underwent a clinically indicated DSA and results were compared with CTA. RESULTS: No exams reported as not diagnostic. The overall mean CT number value of all arterial segments was above 450 HU in both groups. Significant lower noise, and higher SNR and CNR values were found in group 1 in comparison with group 2 despite the use of 80 kVp. In 62-group 1 patients studied by DSA, CTA showed in a segment-based analysis a sensitivity, negative predictive value and accuracy of 100%, 100% and 99% respectively. Mean ED in group 1 was 0.54 ±â€¯0.1 mSv with a dose reduction up to 86%. CONCLUSIONS: CTA for carotid arteries using latest IR algorithm allows to perform exams with submillisievert radiation exposure maintaining good image quality, overall evaluability and diagnostic accuracy.

Coronary artery calcium scoring with photon-counting CT: first in vivo human experience.

To evaluate the performance of photon-counting detector (PCD) computed tomography (CT) for coronary artery calcium (CAC) score imaging at standard and reduced radiation doses compared to conventional energy-integrating detector (EID) CT. A dedicated cardiac CT phantom, ten ex vivo human hearts, and ten asymptomatic volunteers underwent matched EID and PCD CT scans at different dose settings without ECG gating. CAC score, contrast, and contrast-to-noise ratio (CNR) were calculated in the cardiac CT phantom. CAC score accuracy and reproducibility was assessed in the ex vivo hearts. Standard radiation dose (120 kVp, reference mAs = 80) in vivo CAC scans were compared against dose-reduced CAC scans (75% dose reduction; reference mAs = 20) for image quality and CAC score reproducibility. Interstudy agreement was assessed by using intraclass correlation (ICC), linear regression, and Bland-Altman analysis with 95% confidence interval limits of agreement (LOA). Calcium-soft tissue contrast and CNR were significantly higher for the PCD CAC scans in the cardiac CT phantom (all P < 0.01). Ex vivo hearts: CAC score reproducibility was significantly higher for the PCD scans at the lowest dose setting (50 mAs) (P = 0.002); score accuracy was similar for both detector systems at all dose settings. In vivo scans: the agreement between standard dose and low dose CAC score was significantly better for the PCD than for the EID with narrower LOA in Bland-Altman analysis, linear regression slopes closer to 1 (0.96 vs. 0.84), and higher ICC values (0.98 vs. 0.93, respectively). Phantom and in vivo human studies showed PCD may significantly improve CAC score image quality and/or reduce CAC score radiation dose while maintaining diagnostic image quality.

The use of 80 kV versus 100 kV in pulmonary CT angiography: An evaluation of the impact on radiation dose and image quality on two CT scanners.

INTRODUCTION: Use of CT in the investigation of pulmonary embolism in radiosensitive patients such as pregnant and young female patients entails the need for protocol optimization. The aim of this study was to analyze the dose reduction and image quality achieved by using 80 kV instead of 100 kV in CT pulmonary angiography protocols. METHODS: 80 examinations of non-obese patients were analyzed (40 consecutive patients for each protocol, equally distributed on two CT scanners). Objective image quality was assessed by measurements of HU values (average and standard deviation) in five ROIs in pulmonary arteries and calculations of signal-to-noise (SNR) and contrast-to-noise ratios (CNR). Subjective image quality was independently evaluated by two radiologists in terms of perceived noise, sharp reproduction of pulmonary arteries and overall diagnostic quality. Radiation dose parameters (CTDIvol, DLP, SSDE and effective dose) and effective risk were compared. Differences in radiation dose and objective measures of image quality for the two protocols were assessed using the independent t test; comparison of subjective grading of image quality was performed with the Mann-Whitney U test. RESULTS: Use of 80 kV significantly increased both arterial contrast enhancement and image noise. Differences in SNR and CNR between protocols were not statistically significant. Achieved dose reduction by using 80 kV was significant on both scanners (SSDE reduction 35% and 46%, p < 0.001; effective dose reduction 40% and 53%, p < 0.001). CONCLUSION: Use of 80 kV protocols for CT examinations of pulmonary arteries in non-obese patients with bodyweight below 80 kg results in significant reduction of radiation doses without compromising image quality.

Low contrast material dose coronary computed tomographic angiography using a dual-layer spectral detector system in patients at risk for contrast-induced nephropathy.

OBJECTIVE:: To evaluate the effects of virtual monochromatic imaging (VMI) using dual-layer spectral detector CT on the image quality of coronary CT angiography (CCTA) acquired by using a low contrast material (CM) dose. METHODS:: We used a VMI 50keV protocol with a 50% CM dose (140 mgI kg-1) to scan 30 patients with renal insufficiency and a 120 kVp with the standard CM dose (280 mgI kg-1) to scan 30 controls without renal insufficiency. Quantitative parameters, including CT attenuation, image noise, and contrast-to-noise ratio (CNR), were measured. The visual image quality factors of contrast enhancement, image noise, beam-hardening artefact, vessel sharpness, and overall image quality were scored on a 4-point scale. RESULTS:: The mean CT attenuation of the ascending aorta was significantly higher for 50 keV VMI than for 120 kVp. Image noise was significantly lower under the 50 keV VMI. CNR and the mean visual score for contrast enhancement were significantly higher for 50 keV VMI. There were no significant differences in the other visual image quality parameters between the two protocols. CONCLUSION:: Dual-layer spectral detector CT using 50 keV VMI enabled reducing the CM dose by 50 % without CCAT image quality degradation in patients with renal insufficiency. ADVANCES IN KNOWLEDGE:: The VMI 50 keV protocol using dual-layer spectral detector CT and a CM dose reduced by 50 % (140 mgI kg-1) can improve the diagnostic image quality of CCTA.

Safety and accuracy of spinal instrumentation surgery in a hybrid operating room with an intraoperative cone-beam computed tomography.

Although spinal instrumentation technique has undergone revolutionary progress over the past few decades, it may still carry significant surgery-related risks. The purpose of the present study was to assess the radiological accuracy of spinal screw instrumentation using a hybrid operating room (OR) and quantify the related radiation exposure. This retrospective study included 33 cases of complex spine fusion surgeries that were conducted using a hybrid OR with a flat panel detector (FPD) angiography system. Twelve cases (36.4%) were cervical, and 21 (63.6%) were thoracolumbar. The average number of spine fusion levels was 3 and 4.8, respectively, at the cervical and thoracolumbar spine levels. A FPD angiography system was used for intraoperative cone-beam computed tomography (CBCT) to obtain multi-slice spine images. All operations were conducted under optimized radiation shielding. Entrance surface doses (ESDs) and exposure times were recorded in all cases. A total of 313 screws were placed. Satisfactory screw insertion could be achieved in all cases with safe screw placement in 97.4% and acceptable placement in 2.6%. None of the cases showed any significant anatomical violation by the screws. The radiation exposure to the patients was absolutely consistent with the desired ESD value, and that to the surgeons, under the annual dose limit. These results suggest that the hybrid OR with a FPD angiography system is helpful to achieve safe and precise spinal fusion surgery, especially in complex cases.