Optimized energy of spectral coronary CT angiography for coronary plaque detection and quantification

BackgroundTo optimize spectral coronary computed tomography angiography (CTA) for quantification of coronary artery plaque components.Materials and methodsFifty-one subjects were prospectively enrolled (88.2% male) (NCT02740699). Dual energy coronary CTA was performed at 90/Sn150 kVp using a 3rd generation dual-source CT scanner (SOMATOM Force, Siemens Healthcare). Dual energy images were reconstructed with a) linear mixed blending of 90 and Sn150 kVp data, b) virtual monoenergetic algorithm from 40 to 150 keV (at 10- keV intervals), and c) noise-optimized virtual monoenergetic algorithm from 40 to 150 keV. Image noise, iodine signal-to-noise-ratio (SNR), and contrast-to-noise ratio (CNR) for calcified and non-calcified plaque were measured. Qualitative readings of image quality were performed. Semi-automated software (QAngioCT, Medis) was used to quantify coronary plaque. Linear mixed-models that account for within-subject correlation of plaques were used to compare the results.Results100–150 keV noise-optimized virtual monoenergetic images had lower image noise than linear mixed images (all P < 0.05). The highest iodine SNR was achieved in 40 keV noise-optimized virtual monoenergetic images (33.3 ± 0.6 vs 23.3 ± 0.7 for linear mixed images, P < 0.001). 40–70 keV noise-optimized virtual monoenergetic images and 70 keV virtual monoenergetic images had superior coronary plaque CNR versus linear mixed images (all P < 0.01) with a maximum improvement of 20.1% and 22.7% for calcified plaque and non-calcified plaque (38.8 ± 2.2 vs 32.3 ± 2.3 and 17.3 ± 1.3 vs 14.1 ± 1.4, respectively). Using 90/Sn150 kVp linear mixed images as a reference, the plaque quantity was similar for 70 keV noise-optimized virtual monoenergetic images whereas low keV images (e.g. 40 keV) yielded significantly higher coronary plaque volumes (all P < 0.001).ConclusionSpectral coronary CTA with low energy (40–70 keV) post-processing can improve the CNR of coronary plaque components. However, low energies (such as 40 keV) resulted in different absolute volumes of coronary plaque compared to “conventional” mixed 90/Sn150 kVp images.     

Noise-optimized virtual monoenergetic reconstructions of dual-energy CT angiographies improve assessability of the lower leg arterial segments in peripheral arterial occlusive disease

IntroductionThe aim of this study was to evaluate the influence of a noise optimized virtual monoenergetic reconstruction algorithm (VMI+) on the image quality and assessability of dual energy (DE) computed tomography angiography (CTA) of the lower extremity runoff.MethodsA total of 118 lower extremity runoff CTA performed on a 3rd generation DE-CT scanner in 109 patients (54 females; 75.6 ± 9.5 years) were included in this retrospective study. Axial image stacks were reconstructed with a standard 120 kV setting and VMI+ of different keV levels. Objective image quality criteria (contrast attenuation, signal-to-noise [SNR] and contrast-to-noise ratio [CNR]) were measured. Two radiologists evaluated subjective image quality regarding intraluminal attenuation and image noise using a 5-point Likert scale. Diagnostic accuracy for significant stenosis (>75%) and vessel occlusion was assessed for 120 kV and 50 keV VMI+ images rated by two radiologists. In all patients, a digital subtraction angiography (DSA) rated by on board-certified radiologist served as the standard of reference.ResultsIntraluminal attenuation was highest in 40/50 keV VMI+ while SNR were similar to 120 kV images. In subjective assessment, intraluminal contrast of 50 keV images was deemed superior compared to 120 kV despite higher image noise. Sensitivity, specificity, and accuracy for detection of a vessel occlusion were similar in 50 keV VMI+ compared to 120 kV (70%/92%/84%; 70%/91%/83%; p < 0.001) but 13 of 118 (11%) lower leg runoffs were only assessable with 50 keV VMI+.ConclusionVMI+ reconstructions improve assessability of DE-CTA by increased luminal attenuation with consistent image noise, also allowing the evaluation of lower leg arterial segments inassessable with standard reconstructions.Implications for practiceProviding higher intraluminal attenuation and similar image noise compared with conventional reconstructions, 50 keV VMI+ may be appropriate for routine evaluation of DE-CTA.     

Virtual Monoenergetic Spectral Detector CT for Preoperative CT Angiography in Liver Donors

ObjectiveThe purpose of this study was to evaluate the use of virtual monoenergetic images (VMI) in pre-operative CT angiography of potential donors for living donor adult liver transplantation (LDALT), and to determine the optimal energy level to maximize vascular signal-to-noise and contrast-to-noise ratios (SNR and CNR, respectively).Materials and methodsWe retrospectively evaluated 29 CT angiography studies performed preoperatively in potential liver donors on a spectral detector CT scanner. All studies included arterial, early venous, and delayed venous phase imaging. Conventional polyenergetic images were generated for each patient, as well as virtual monoenergetic images in 10 keV increments from 40 –100 keV. Arteries (aorta and celiac, superior mesenteric, common hepatic, right and left hepatic arteries) were assessed on arterial phase images; portal venous system branches (splenic, superior mesenteric, main, right, and left portal veins) on early venous phase images; and hepatic veins on late venous phase images. Vascular attenuation, background parenchymal attenuation, and noise were measured on each set of virtual monoenergetic and conventional images.ResultsBackground hepatic and vascular noise decreased with increasing keV, with the lowest noise at 100 keV. Vascular SNR and CNR increased with decreasing keV and were highest at 40 keV, with statistical significance compared with conventional ( P < 0.05).ConclusionsIn preoperative CT angiography for potential liver donors, the optimal keV for assessing the vasculature to improve SNR and CNR is 40 keV. Use of low keV VMI in LDALT CT protocols may facilitate detection of vascular anatomical variants that can impact surgical planning.     

Endoleaks after endovascular aortic aneurysm repair: Improved detection with noise-optimized virtual monoenergetic dual-energy CT

PurposeTo assess image quality and diagnostic performance of a noise-optimized algorithm to reconstruct virtual monoenergetic images (VMI+) for the detection of endoleaks after endovascular abdominal aortic aneurysm repair (EVAR) using dual-energy CT angiography (DE-CTA).Materials and methodsSeventy-five patients (42 men; 66.2 ± 11.7 years) underwent DE-CTA following EVAR. Arterial phase images were acquired in dual-energy mode for the reconstruction of standard linearly-blended M_0.5, VMI+ and traditional monoenergetic images (VMI) at 40–100 keV in 10-keV intervals. Contrast-to-noise ratios (CNR) were calculated for the area of leakage in patients with endoleaks. Diagnostic accuracy for endoleak detection was evaluated by three blinded radiologists using the objectively best series for each reconstruction technique.ResultsThirty-four out of 75 patients showed endoleaks. Quantitative image parameters were highest at 40-keV VMI+ (CNR, 21.3 ± 11.1), compared to M_0.5 (CNR, 10.9 ± 5.5) and all VMI series that showed highest values at 70 keV (CNR, 13.5 ± 6.6; all P < 0.001). ROC analysis for endoleak detection revealed an area under the curve (AUC) of 0.992 for 40-keV VMI+ series, which was significantly higher (P ≤ 0.039) compared to 70-keV VMI (0.914) and M_0.5 series (0.916).ConclusionsNoise-optimized VMI+ series at 40 keV improve diagnostic accuracy for the detection and rule-out of endoleaks after EVAR.     

The potential of iodinated contrast reduction in dual-energy CT thoracic angiography; an evaluation of image quality

IntroductionThe purpose of this study was to compare a dual energy CT (DECT) protocol with 50% reduction of iodinated contrast to a single energy CT (SECT) protocol using standard contrast dose in imaging of the thoracic aorta.MethodsDECT with a 50% reduction in iodinated contrast was compared with SECT. For DECT, monoenergetic images at 50, 55, 60, 65, 68, 70, and 74 keV were reconstructed with adaptive statistical iterative reconstruction (ASiR-V) of 50% and 80%. Objective image quality parameters included intravascular attenuation (HU), image noise (SD), contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR). Two independent radiologists subjectively assessed the image quality for the 55 and 68 keV DECT reconstructions and SECT on a five-point Likert scale.ResultsAcross 14 patients, the intravascular attenuation at 50–55 keV was comparable to SECT (p > 0.05). The CNRs were significantly lower for DECT with ASIR-V 50% compared to SECT for all keV-values (p < 0.05 for all). For ASIR-V 80%, CNR was comparable to SECT at energies below 60 keV (p > 0.05). The subjective image quality was comparable between DECT and SECT independent of keV level.ConclusionThis study indicates that a 50% reduction in iodinated contrast may result in adequate image quality using DECT with monoenergetic reconstructions at lower energy levels for the imaging of the thoracic aorta. The best image quality was obtained for ASiR-V 80% image reconstructions at 55 keV.Implications of practiceDual energy CT with a reduction in iodinated contrast may result in adequate image quality in imaging of the thoracic aorta. However, increased radiation dose may limit the use to patients in which a reduction in fluid and iodinated contrast volume may outweigh this risk.     

光谱CT头部虚拟平扫图像:不同单能量图像质量的对比

目的:探讨双层探测器光谱CT不同单能量图像在头部影像诊断中的临床应用效能。方法:回顾性分析2019年6-12月因头晕、晕厥和头痛等临床症状而在本院行光谱CT(IQon Spectral CT)头部CT平扫检查的38例患者的影像资料。从光谱CT扫描中可获取常规混合能量图像和40~120 keV的光谱成像数据,以5 keV为间隔增量将光谱数据重建为17组单能级图像。分别测量每组图像上幕上灰质和白质的CT值和噪声值(SD),并计算信号噪声比(SNR)和对比信噪比(CNR)。同时对常规图像与120 keV单能级图像的伪影区域的脑组织结构(灰、白质)的对比及后颅窝伪影情况进行主、客观评分和比较。采用Bonferroni法进行统计学分析。结果:各组单能图像之间脑灰质CT值(P<0.001)、噪声(P=0.012)和CNR(P<0.001)的差异均有统计学意义,而脑白质CT值的差异无统计学意义(P=0.107)。其中65 keV图像的脑灰质CT值,脑灰、白质的噪声和SNR均高于其它单能级和常规混合能量图像(P<0.05),CNR亦高于其它单能级图像和常规图像(P<0.05)。与常规图像比较,120keV单能级图像上颅底层面伪影区域的脑灰、白质CT值(P=0.046)、噪声(P<0.01)、SNR(P<0.001)和CNR(P<0.001)的差异均具有统计学意义,且图像质量评分(P<0.001)和伪影评分(P<0.001)的差异亦有统计学意义。结论:和常规图像相比,从双层探测器光谱CT重建的单能图像在65 keV灰、白质对比度好,图像噪声降低、软组织分别率提高。120 keV单能级图像在由颅骨引起的X线束硬化伪影方面,能有效还原周围组织结构,提升图像质量。     

应用80kV管电压降低主动脉CT造影射线剂量初探

目的 探讨80kV管电压256层螺旋CT主动脉造影降低射线剂量的可行性。方法 对62例疑似主动脉疾病的患者进行主动脉CT造影成像,分为常规管电压扫描组(120kV扫描组)和低管电压扫描组(80kV扫描组),每组31例。然后对两组图像信号噪声比、对比度噪声比和有效剂量进行评估。结果 120与80kV2个扫描组的图像信号噪声比分别为(35.92±5.04)和(33.95±8.30),对比度噪声比分别为(30.32±4.78)和(28.71±7.96),差异均无统计学意义(t =1.131、0.964, P >0.05)。而二组的有效剂量分别为(14.28±0.96)和(9.72±0.81)mSv,差异有统计学意义 (t =20.12, P <0.001)。 结论 同120kV管电压比较,80kV管电压主动脉CT造影在没有降低图像质量的情况下,射线剂量降低约31.9%,同时降低造影剂剂量50%。     

Reduced iodine load with CT coronary angiography using dual-energy imaging: A prospective randomized trial compared with standard coronary CT angiography

BackgroundThere is concern regarding the administration of iodinated contrast to patients with impaired renal function because of the increased risk of contrast-induced nephropathy.ObjectiveEvaluate image quality and feasibility of a protocol with a reduced volume of iodinated contrast and utilization of dual-energy coronary CT angiography (DECT) vs a standard iodinated contrast volume coronary CT angiography protocol (SCCTA).MethodsA total of 102 consecutive patients were randomized to SCCTA (n = 53) or DECT with rapid kVp switching (n = 49). Eighty milliliters and 35 mL of iodinated contrast were administered in the SCCTA and DECT cohorts, respectively. Two readers measured signal and noise in the coronary arteries; signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. A 5-point signal/noise Likert scale was used to evaluate image quality; scores of <3 were nondiagnostic. Agreement was assessed through kappa analyses.ResultsDemographics and radiation dose were not significantly different; there was no difference in CNR between both cohorts (P = .95). A significant difference in SNR between the groups (P = .02) lost significance (P = .13) when adjusted for body mass index. The median Likert score was inferior for DECT for reader 1 (3.6 ± 0.6 vs 4.3 ± 0.6; P < .001) but not reader 2 (4.1 ± 0.6 vs 4.3 ± 0.5; P = .06). Agreement in diagnostic interpretability in the DECT and SCCTA groups was 91% (95% confidence interval, 86%–100%) and 96% (95% confidence interval, 90%–100%), respectively.ConclusionDECT resulted in inferior image quality scores but demonstrated comparable SNR, CNR, and rate of diagnostic interpretability without a radiation dose penalty while allowing for >50% reduction in contrast volume compared with SCCTA.     

Dual-energy computed tomography in patients with cutaneous malignant melanoma: Comparison of noise-optimized and traditional virtual monoenergetic imaging

ObjectiveThe aim of this study was to investigate the impact of noise-optimized virtual monoenergetic imaging (VMI+) reconstructions on quantitative and qualitative image parameters in patients with cutaneous malignant melanoma at thoracoabdominal dual-energy computed tomography (DECT).Materials and methodsSeventy-six patients (48 men; 66.6 ± 13.8 years) with metastatic cutaneous malignant melanoma underwent DECT of the thorax and abdomen. Images were post-processed with standard linear blending (M_0.6), traditional virtual monoenergetic (VMI), and VMI+ technique. VMI and VMI+ images were reconstructed in 10-keV intervals from 40 to 100 keV. Attenuation measurements were performed in cutaneous melanoma lesions, as well as in regional lymph node, subcutaneous and in-transit metastases to calculate objective signal-to-noise (SNR) and contrast-to-noise (CNR) ratios. Five-point scales were used to evaluate overall image quality and lesion delineation by three radiologists with different levels of experience.ResultsObjective indices SNR and CNR were highest at 40-keV VMI+ series (5.6 ± 2.6 and 12.4 ± 3.4), significantly superior to all other reconstructions (all P < 0.001). Qualitative image parameters showed highest values for 50-keV and 60-keV VMI+ reconstructions (median 5, respectively; P ≤ 0.019) regarding overall image quality. Moreover, qualitative assessment of lesion delineation peaked in 40-keV VMI+ (median 5) and 50-keV VMI+ (median 4; P = 0.055), significantly superior to all other reconstructions (all P < 0.001).ConclusionLow-keV noise-optimized VMI+ reconstructions substantially increase quantitative and qualitative image parameters, as well as subjective lesion delineation compared to standard image reconstruction and traditional VMI in patients with cutaneous malignant melanoma at thoracoabdominal DECT.     

CT angiography for planning transcatheter aortic valve replacement using automated tube voltage selection: Image quality and radiation exposure

PurposeTo assess image quality and accuracy of CT angiography (CTA) for transcatheter aortic valve replacement (TAVR) planning performed with 3rd generation dual-source CT (DSCT).Material and methodsWe evaluated 125 patients who underwent TAVR-planning CTA on 3rd generation DSCT. A two-part protocol was performed including retrospectively ECG-gated coronary CTA (CCTA) and prospectively ECG-triggered aortoiliac CTA using 60 mL of contrast medium. Automated tube voltage selection and advanced iterative reconstruction were applied. Effective dose (ED), signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were calculated. Five-point scales were used for subjective image quality analysis. In patients who underwent TAVR, sizing parameters were obtained.ResultsImage quality was rated good to excellent in 97.6% of CCTA and 100% of aortoiliac CTAs. CTA studies at >100 kV showed decreased objective image quality compared to 70–100 kV (SNR, all p ≤ 0.0459; CNR, all p ≤ 0.0462). Mean ED increased continuously from 70 to >100 kV (CCTA: 4.5 ± 1.7 mSv–13.6 ± 2.9 mSv, all p ≤ 0.0233; aortoiliac CTA: 2.4 ± 0.9 mSv–6.8 ± 2.7 mSv, all p ≤ 0.0414). In 39 patients TAVR was performed and annulus diameter was within the recommended range in all patients. No severe cardiac or vascular complications were noted.Conclusion3rd generation DSCT provides diagnostic image quality in TAVR-planning CTA and facilitates reliable assessment of TAVR device and delivery option while reducing radiation dose.     

CT metal artifacts in patients with total hip replacements: for artifact reduction monoenergetic reconstructions and post-processing algorithms are both efficient but not similar

Objectives

This study compares metal artifact (MA) reduction in imaging of total hip replacements (THR) using virtual monoenergetic images (VMI), for MA-reduction-specialized reconstructions (MAR) and conventional CT images (CI) from detector-based dual-energy computed tomography (SDCT).

Methods

Twenty-seven SDCT-datasets of patients carrying THR were included. CI, MAR and VMI with different energy-levels (60–200 keV) were reconstructed from the same scans. MA width was measured. Attenuation (HU), noise (SD) and contrast-to-noise ratio (CNR) were determined in: extinction artifact, adjacent bone, muscle and bladder. Two radiologists assessed MA-reduction and image quality visually.

Results

In comparison to CI, VMI (200 keV) and MAR showed a strong artifact reduction (MA width: CI 29.9±6.8 mm, VMI 17.6±13.6 mm, p<0.001; MAR 16.5±14.9 mm, p<0.001; MA density: CI -412.1±204.5 HU, VMI -279.7±283.7 HU; p<0.01; MAR -116.74±105.6 HU, p<0.001). In strong artifacts reduction was superior by MAR. In moderate artifacts VMI was more effective. MAR showed best noise reduction and CNR in bladder and muscle (p<0.05), whereas VMI were superior for depiction of bone (p<0.05). Visual assessment confirmed that VMI and MAR improve artifact reduction and image quality (p<0.001).

Conclusions

MAR and VMI (200 keV) yielded significant MA reduction. Each showed distinct advantages both regarding effectiveness of artifact reduction, MAR regarding assessment of soft tissue and VMI regarding assessment of bone.

Key Points

? Spectral-detector computed tomography improves assessment of total hip replacements and surrounding tissue.? Virtual monoenergetic images and MAR reduce metal artifacts and enhance image quality.? Evaluation of bone, muscle and pelvic organs can be improved by SDCT.

     

Noise-optimized monoenergetic post-processing improves visualization of incidental pulmonary embolism in cancer patients undergoing single-pass dual-energy computed tomography

Purpose

To evaluate noise-optimized monoenergetic postprocessing of dual-energy CT (DE-CT) on image quality in patients with incidental pulmonary embolism in single-pass portal-venous phase CT (CT_pv).

Materials and methods

20 Consecutive patients with incidental pulmonary embolism in contrast-enhanced oncological follow-up DE-CT_pv examination were included in this study. Images were acquired with a 3rd generation DE-CT system in DE mode (100/Sn150 kV) and activated tube current modulation 90 s after contrast agent administration. Subsequently, virtual monoenergetic images (MEI+) were reconstructed at five different keV levels (40, 55, 70, 85, 100) and compared to the standard linearly blended (M_0.8) CT_pv images. Image quality was assessed qualitatively (vascular contrast and detectability of embolism, image noise, iodine influx artifact; two independent readers; 5-point Likert scale; 5 = excellent) and quantitatively by calculating signal-to-noise (SNR) and contrast-to-noise ratios (CNR).

Results

Highest vessel contrast and highest detectability of embolism were observed in MEI+ at 40 keV (4.7 ± 0.4) and 55 keV (4.2 ± 0.6) with significant differences as compared to CT_pv (3.6 ± 0.5) and high keV reconstructions (70, 85, 100; p ≤ 0.01). Image noise significantly increased at 40 keV MEI+ compared to all other MEI+ reconstructions and CT_pv (p < 0.001). SNR and CNR calculations were highest at 40 keV MEI+ followed by 55 keV and CT_pv with significant differences to high keV MEI+ (85–100).

Conclusions

Computed MEI+ at low keV levels allow for improved vessel contrast and visualisation of incidental pulmonary embolism in patients with portal-venous phase CT scans by substantially increasing CNR and SNR.

     

Global longitudinal strain assessment by computed tomography in severe aortic stenosis patients - Feasibility using feature tracking analysis

BackgroundGlobal longitudinal strain (GLS) detects subclinical myocardial changes in patients with aortic stenosis (AS). Although GLS is typically measured by transthoracic echocardiography (TTE), assessment by multiphasic gated computed tomography angiography (CTA) has become recently available. We sought to evaluate the feasibility of CTA-derived GLS assessment and compare its agreement with TTE using the same post-processing software in severe AS patients undergoing transcatheter aortic valve replacement (TAVR) evaluation.MethodsWe evaluated patients with severe AS, sinus rhythm and adequate image quality for GLS analysis by both CTA and TTE pre-TAVR using 2D CT-Cardiac Performance Analysis prototype software (TomTec). The 18-segment model was used for GLS analysis by averaging the three long-axis views in both CTA and TTE studies. Agreement was assessed using linear regression and Bland-Altman analysis.ResultsA total of 123 consecutive patients were included (mean age 84 ± 7 years, 45% female). The mean left ventricular ejection fraction (LVEF) by CTA and TTE were similar 53 ± 14% for both. On average, CTA-derived GLS was greater than by TTE (−20 ± 6.5% vs. −16 ± 4.9%, respectively, p < 0.001). There was a moderate correlation between GLS assessed by CTA vs. TTE (r = 0.62, p < 0.001), although variability between imaging methods existed. The correlation between GLS and LVEF was strong (r = −0.90, p < 0.001 for CTA, r = −0.88, p < 0.001 for TTE) using the same imaging modality.ConclusionCTA-derived GLS assessment is feasible in selected patients with sinus rhythm and adequate image quality. The agreement of GLS between TTE and CTA is moderate but not interchangeable suggesting a potential modality-specific GLS threshold.     

Cerebral CT angiography with iterative reconstruction at 70 kVp and 30 mL iodinated contrast agent: Initial experience

ObjectivesTo evaluate the radiation dose and image quality of cerebral CT angiography (CTA) at 70 kVp with 30 mL iodinated contrast agent.MethodsOne hundred patients were prospectively classified into two groups: Group A (n = 50), 120 kVp cerebral CTA with 60 mL iodinated contrast agent reconstructed by filtered back projection (FBP) and Group B (n = 50), 70 kVp with 30 mL iodinated contrast agent reconstructed by sinogram-affirmed iterative reconstruction (SAFIRE). CT values, noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the internal carotid artery (ICA) and middle cerebral artery (MCA) were measured. Subjective image quality was evaluated. Effective dose (ED) was calculated.ResultsThe mean CT values of the ICA and MCA of Group B were higher than those of Group A (all P < 0.001). The mean noise of Group A was lower than that of Group B (P < 0.001). SNR_ICA, SNR_MCA and CNR_ICA, CNR_MCA of Group A were higher than Group B (all P < 0.001). There was no difference in vessel sharpness, noise, and overall quality between the two groups (all P > 0.05). ED of Group B (0.2 ± 0.0 mSv) was lower than Group A (1.3 ± 0.1 mSv) (p < 0.001).ConclusionCerebral CTA with iterative reconstruction at 70 kVp and 30 mL iodinated contrast agent is feasible, allowing for substantial dose reduction compared with conventional cerebral CTA protocol.     

First experience with monochromatic coronary computed tomography angiography from a 64-slice CT scanner with Gemstone Spectral Imaging (GSI)

BackgroundNew technology combining dual-energy CT with the latest gemstone detectors for spectral imaging (GSI) can be used to synthesize monochromatic images that mimic images as if different monochromatic x-ray sources were used.ObjectiveThe aim of the study was to evaluate the optimal combination of monochromatic image energy and adaptive statistical iterative reconstruction (ASiR) for monochromatic reconstruction of coronary CT angiography (CTA) images with the use of GSI.MethodsTwenty consecutive patients underwent coronary CTA on a GSI capable 64-slice CT scanner (Discovery CT 750 High Definition, GE Healthcare). In 7 sets of monochromatic images (60, 65, 70, 75, 80, 90, and 110 keV; each with increasing contributions of ASiR, ie, 0%, 20%, 40%, 60%, and 80%; n = 35 reconstructions per patient), signal-to-noise (aortic root) and contrast-to-noise (left main artery) ratios were assessed. Signal-to-noise ratio, contrast-to-noise ratio, and image quality (graded on a 5-point Likert scale) were assessed in all above monochromatic reconstructions and compared with the respective standard (conventional polychromatic) image.ResultsCompared with conventional polychromatic images, reconstructions with 60 keV and 80% ASiR showed the highest improvement in contrast-to-noise (144%; P < 0.001) and signal-to-noise ratio (173%; P < 0.001). Image quality reached a plateau at 65–75 keV with 40%–60% ASiR blending, yielding a maximal image quality score improvement of 50% compared with conventional imaging (P < 0.001).ConclusionIn coronary CTA with low radiation technique (mean radiation dose, 1.8 ± 0.7 mSv), GSI with monochromatic reconstructions (65–75 keV) and ASiR (40%–60%) offers significant noise reduction and image quality improvement.     

Noise-Optimized Virtual Monoenergetic Dual-Energy CT Improves Diagnostic Accuracy for the Detection of Active Arterial Bleeding of the Abdomen

Purpose

To evaluate diagnostic accuracy of a noise-optimized virtual monoenergetic imaging (VMI+) reconstruction technique for detection of active arterial abdominal bleeding on dual-energy (DE) CT angiography compared with standard image reconstruction.

Image Quality of ECG-Triggered High-Pitch,Dual-Source Computed Tomography Angiography for Cardiovascular Assessment in Children

PurposeEvaluate the feasibility and determinants of image quality of ECG-triggered High-Pitch Dual-Source Computed Tomography Angiography (CTA) for cardiovascular assessment in Children.Material and methodsAll children that underwent ECG-triggered High-Pitch Dual-Source CTA between August 2014 and September 2017 were identified. Scanner parameters and patients' information were retrieved. Objective image quality was evaluated measuring the Hounsfield units (HU) and standard deviation of regions of interests in the left ventricle, ascending and descending aorta. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Qualitative image quality was recorded independently by two pediatric radiologist blinded using a three-point scale: 1 – good image quality, 2 – mild artifacts, 3 – poor image quality. Continuous variables were presented as mean ± standard deviation. The interobserver agreement and non-parametric test were used.Results93 patients (mean age 5.6 ± 7.1 years) were selected. Average cardiovascular attenuation, SNR and CNR were 406.2 ± 146.3 HU, 24.2 ± 16.0 HU and 52.1 ± 38.6 HU, respectively. Average image quality was 1.51 ± 0.48 and the inter-observer agreement was excellent (k = 0.8). Worse subjective quality scores were associated with lower age, height, weight, BSA, lower contrast dose and slower injection rates (p < 0.05). Higher heart rate was associated with high attenuation (p < 0.05), however, SNR and CNR did not show an association with heart rate (p = 0.80).ConclusionsECG-triggered High-Pitch Dual-Source cardiac CTA is feasible and provides good or excellent image quality for the evaluation of cardiovascular diseases in children.     

Value of monoenergetic low-kV dual energy CT datasets for improved image quality of CT pulmonary angiography

Purpose

High vessel attenuation and high contrast-to-noise ratio (CNR) are prerequisites for high diagnostic confidence in CT pulmonary angiography (CTPA). This study evaluated the impact of calculated monoenergetic dual-energy (DE) CTPA datasets on vessel attenuation and CNR.

Materials and methods

50 Patients (24 men, mean age 68 ± 14 years) who underwent DE-CTPA were retrospectively included in this study. The 80 and 140-kV DE polyenergetic image data were used to calculate virtual monoenergetic image datasets in 10 kiloelectron volt (keV) increments from 40 to 120 keV. Vessel and soft tissue attenuation and image noise were measured in various regions of interest and the CNR was subsequently calculated. Differences in vessel attenuation and CNR were compared between the different monoenergetic datasets. The best monoenergetic dataset was then compared to the standard 120-kV polyenergetic dataset.

Results

Vessel attenuation and CNR of 70-keV CTPA datasets were superior to all other monoenergetic image datasets (all p < 0.05). 70-keV monoenergetic datasets provided a statistically significant 12% increase in mean vessel attenuation compared to standard 120-kV polyenergetic datasets (384 ± 117 HU vs. 342 ± 106 HU, respectively; p < 0.0001) and a statistically significant 18% increase in mean CNR (29 ± 13 vs. 24± 11 respectively; p < 0.0001).

Conclusion

Virtual 70-keV monoenergetic CTPA image datasets significantly increase vessel attenuation and CNR of DE-CTPA studies, suggesting that clinical application of low-keV monoenergetic reconstructions may allow a decrease in the amount of iodinated contrast required for adequate image quality in DE-CTPA examinations.     

双层探测器光谱CT单能量成像联合个性化注射方案在颅脑CT血管成像中的应用研究

目的:探讨双层探测器光谱CT单能量成像联合个性化对比剂注射方案在颅脑CT血管成像（CTA）中的应用价值。方法:回顾性分析2020年8月至11月在华中科技大学同济医学院附属协和医院采用双层探测器光谱CT和个性化对比剂注射方案行颅脑CTA检查的76例患者的影像资料。对基于双层探测器光谱CT数据重建生成的120 kVp混合迭...     

Image quality of ultra-low-dose dual-source CT angiography using high-pitch spiral acquisition and iterative reconstruction in young children with congenital heart disease

BackgroundObtaining diagnostic CT image quality with ultra-low radiation dose in young children with congenital heart disease remains challenging.ObjectiveWe evaluated the feasibility and image quality of prospectively electrocardiogram (ECG)-triggered high-pitch spiral acquisition with iterative reconstruction for pediatric cardiovascular CT angiography.MethodsSixty-two consecutive pediatric patients younger than 2 years with congenital heart disease underwent prospectively ECG-triggered high-pitch spiral dual-source CT acquisition. Patients were randomly assigned into 2 groups: full tube current (40–70 mAs) scans with filtered back projection reconstruction (group A) and half tube current (20–35 mAs) scans with sinogram-affirmed iterative reconstruction (group B). Attenuation, noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and subjective image quality were compared between the 2 groups. Effective radiation dose was also estimated for both groups.ResultsNo significant difference was found in the attenuation, image noise, SNR, and CNR between the 2 groups in the same evaluated anatomic regions, whereas the attenuation and image noise were slightly lower, and the SNR and CNR were slightly higher in group B. No significant difference was found in subjective image quality between the 2 groups (4.27 ± 0.73 vs. 4.34 ± 0.42; P = .813). Effective dose was 0.06 ± 0.03 mSv in group B and 0.13 ± 0.04 mSv in group A, reflecting dose savings of 53.8% by using iterative reconstruction.ConclusionsA combination of prospectively ECG-triggered high-pitch spiral acquisition, low tube current, and iterative reconstruction may offer diagnostic image quality in pediatric cardiovascular CT angiography with effective radiation dose < 0.1 mSv.