Stefanie Mangold

Dual-Energy Computed Tomography Angiography of the Lower Extremity Runoff: Impact of Noise-Optimized Virtual Monochromatic Imaging on Image Quality and Diagnostic Accuracy.

ObjectiveThe aim of this study was to evaluate the impact of a noise-optimized virtual monochromatic imaging algorithm (VMI+) on image quality and diagnostic accuracy at dual-energy computed tomography angiography (CTA) of the lower extremity runoff. Materials and MethodsThis retrospective Health Insurance Portability and Accountability Act–compliant study was approved by the local institutional review board. We evaluated dual-energy CTA studies of the lower extremity runoff in 48 patients (16 women; mean age, 63.3 ± 13.8 years) performed on a third-generation dual-source CT system. Images were reconstructed with standard linear blending (F_0.5), VMI+, and traditional monochromatic (VMI) algorithms at 40 to 120 keV in 10-keV intervals. Vascular attenuation and image noise in 18 artery segments were measured; signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Five-point scales were used to subjectively evaluate vascular attenuation and image noise. In a subgroup of 21 patients who underwent additional invasive catheter angiography, diagnostic accuracy for the detection of significant stenosis (≥50% lumen restriction) of F_0.5, 50-keV VMI+, and 60-keV VMI data sets were assessed. ResultsObjective image quality metrics were highest in the 40- and 50-keV VMI+ series (SNR: 20.2 ± 10.7 and 19.0 ± 9.5, respectively; CNR: 18.5 ± 10.3 and 16.8 ± 9.1, respectively) and were significantly (all P < 0.001) higher than in the corresponding VMI data sets (SNR: 8.7 ± 4.1 and 10.8 ± 5.0; CNR: 8.0 ± 4.0 and 9.6 ± 4.9) and F_0.5 series (SNR: 10.7 ± 4.4; CNR: 8.3 ± 4.1). Subjective assessment of attenuation was highest in the 40- and 50-keV VMI and VMI+ image series (range, 4.84–4.91), superior to F_0.5 (4.07; P < 0.001). Corresponding subjective noise assessment was superior for 50-keV VMI+ (4.71; all P < 0.001) compared with VMI (2.60) and F_0.5 (4.11). Sensitivity and specificity for detection of 50% or greater stenoses were highest in VMI+ reconstructions (92% and 95%, respectively), significantly higher compared with standard F_0.5 (87% and 90%; both P ⩽ 0.02). ConclusionsImage reconstruction using low-kiloelectron volt VMI+ improves image quality and diagnostic accuracy compared with traditional VMI technique and standard linear blending for evaluation of the lower extremity runoff using dual-energy CTA.

Single- and dual-energy CT of the abdomen: comparison of radiation dose and image quality of 2nd and 3rd generation dual-source CT.

AbstractObjectivesTo compare single-energy (SECT) and dual-energy (DECT) abdominal CT examinations in matched patient cohorts regarding differences in radiation dose and image quality performed with second- and third-generation dual-source CT (DSCT).MethodsWe retrospectively analysed 200 patients (100 male, 100 female; mean age 61.2u2009±u200913.5xa0years, mean body mass index 27.5u2009±u20093.8xa0kg/m2) equally divided into four groups matched by gender and body mass index, who had undergone portal venous phase abdominal CT with second-generation (group A, 120-kV-SECT; group B, 80/140-kV-DECT) and third-generation DSCT (group C, 100-kV-SECT; group D, 90/150-kV-DECT). The radiation dose was normalised for 40-cm scan length. Dose-independent figure-of-merit (FOM) contrast-to-noise ratios (CNRs) were calculated for various organs and vessels. Subjective overall image quality and reader confidence were assessed.ResultsThe effective normalised radiation dose was significantly lower (Pu2009<u20090.001) in groups C (6.2u2009±u20092.0xa0mSv) and D (5.3u2009±u20091.9xa0mSv, Pu2009=u20090.103) compared to groups A (8.8u2009±u20092.3xa0mSv) and B (9.7u2009±u20092.4xa0mSv, Pu2009=u20090.102). Dose-independent FOM-CNR peaked for liver, kidney, and portal vein measurements (all Pu2009≤u20090.0285) in group D. Subjective image quality and reader confidence were consistently rated as excellent in all groups (all ≥1.53 out of 5).ConclusionsWith both DSCT generations, abdominal DECT can be routinely performed without radiation dose penalty compared to SECT, while third-generation DSCT shows improved dose efficiency.Key Points• Dual-source CT (DSCT) allows for single- and dual-energy image acquisition.n • Dual-energy acquisition does not increase the radiation dose in abdominal DSCT.n • Third-generation DSCT shows improved dose efficiency compared to second-generation DSCT.n • Dose-independent figure-of-merit image contrast was highest with third-generation dual-energy DSCT.n • Third-generation DSCT shows improved dose efficiency for SECT and DECT.

Coronary CT angiography derived morphological and functional quantitative plaque markers correlated with invasive fractional flow reserve for detecting hemodynamically significant stenosis.

OBJECTIVEnCompare morphological and functional coronary plaque markers derived from coronary CT angiography (CCTA) for their ability to detect lesion-specific ischemia.nnnMATERIALS AND METHODSnData of patients who had undergone both dual-source CCTA and invasive fractional flow reserve (FFR) measurement within 3 months were retrospectively analyzed. Various quantitative stenosis markers were derived from CCTA: Corrected coronary opacification (CCO), transluminal attenuation gradient (TAG), remodeling index (RI), computational FFR (cFFR), lesion length (LL), vessel volume (VV), total plaque volume (TPV), and calcified and non-calcified plaque volume (CPV and NCPV). Discriminatory power of these markers for flow-limiting versus non-significant coronary stenosis was assessed against invasive FFR as the reference standard.nnnRESULTSnThe cohort included 37 patients (61xa0±xa012xa0years, 68% male). Among 37 lesions, 11 were hemodynamically significant by FFR. On a per-lesion level, sensitivity and specificity of TPV, CPV, and NCPV for hemodynamically significant stenosis detection were 88% and 74%, 67% and 53%, and 92% and 81%, respectively. For CCO, TAG, RI, and cFFR these were 64% and 86%, 35% and 56%, 82% and 54%, and 100% and 90%, respectively. At ROC analysis, only TPV (0.78, pxa0=xa00.013), NCPV (0.79, pxa0=xa00.009), cFFR (0.85, pxa0=xa00.003), and CCO (0.82, pxa0=xa00.0003) showed discriminatory power for detecting hemodynamically significant stenosis.nnnCONCLUSIONnTPV, NCPV, CCO, and cFFR derived from CCTA can aid detecting hemodynamically significant coronary lesions with cFFR showing the greatest discriminatory ability.

Automated tube voltage selection for radiation dose and contrast medium reduction at coronary CT angiography using 3(rd) generation dual-source CT.

AbstractObjectivesTo investigate the relationship between automated tube voltage selection (ATVS) and body mass index (BMI) and its effect on image quality and radiation dose of coronary CT angiography (CCTA).MethodsWe evaluated 272 patients who underwent CCTA with 3rd generation dual-source CT (DSCT). Prospectively ECG-triggered spiral acquisition was performed with automated tube current selection and advanced iterative reconstruction. Tube voltages were selected by ATVS (70-120xa0kV). BMI, effective dose (ED), and vascular attenuation in the coronary arteries were recorded. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Five-point scales were used for subjective image quality analysis.ResultsImage quality was rated good to excellent in 98.9xa0% of examinations without significant differences for proximal and distal attenuation (all pu2009≥u2009.0516), whereas image noise was rated significantly higher at 70xa0kV compared to ≥100xa0kV (all pu2009<u2009.0266). However, no significant differences were observed in SNR or CNR at 70–120xa0kV (all pu2009≥u2009.0829). Mean ED at 70-120xa0kV was 1.5u2009±u20091.2xa0mSv, 2.4u2009±u20091.5xa0mSv, 3.6u2009±u20092.7xa0mSv, 5.9u2009±u20094.0xa0mSv, 7.9u2009±u20094.2xa0mSv, and 10.7u2009±u20094.1xa0mSv, respectively (all pu2009≤u2009.0414). Correlation analysis showed a moderate association between tube voltage and BMI (ru2009=u2009.639).ConclusionATVS allows individual tube voltage adaptation for CCTA performed with 3rd generation DSCT, resulting in significantly decreased radiation exposure while maintaining image quality.Key Points• Automated tube voltage selection allows an individual tube voltage adaption in CCTA.n • A tube voltage-based reduction of contrast medium volume is feasible.n • Image quality was maintained while radiation exposure was significantly decreased.n • A moderate association between tube voltage and body mass index was found.

Impact of an advanced image-based monoenergetic reconstruction algorithm on coronary stent visualization using third generation dual-source dual-energy CT: a phantom study.

AbstractPurposeTo evaluate the impact of an advanced monoenergetic (ME) reconstruction algorithm on CT coronary stent imaging in a phantom model.Materials and methodsThree stents with lumen diameters of 2.25, 3.0 and 3.5xa0mm were examined with a third-generation dual-source dual-energy CT (DECT). Tube potential was set at 90/Sn150xa0kV for DE and 70, 90 or 120xa0kV for single-energy (SE) acquisitions and advanced modelled iterative reconstruction was used. Overall, 23 reconstructions were evaluated for each stent including three SE acquisitions and ten advanced and standard ME images with virtual photon energies from 40 to 130xa0keV, respectively. In-stent luminal diameter was measured and compared to nominal lumen diameter to determine stent lumen visibility. Contrast-to-noise ratio was calculated.ResultsAdvanced ME reconstructions substantially increased lumen visibility in comparison to SE for stents ≤3xa0mm. 130xa0keV images produced the best mean lumen visibility: 86xa0% for the 2.25xa0mm stent (82xa0% for standard ME and 64xa0% for SE) and 82xa0% for the 3.0xa0mm stent (77xa0% for standard ME and 69xa0% for SE). Mean DLP for SE 120xa0kV and DE acquisitions were 114.4u2009±u20099.8 and 58.9u2009±u20092.2xa0mGyu2009×u2009cm, respectively.ConclusionDECT with advanced ME reconstructions improves the in-lumen visibility of small stents in comparison with standard ME and SE imaging.Key Points• An advanced image-based monoenergetic reconstruction algorithm improves lumen visualization in stents ≤3.0xa0mm.n • Application of high keV reconstructions significantly improves in-stent lumen visualization.n • DECT acquisition resulted inxa049 % radiation dose reduction compared with 120xa0kV SE.

Clinical feasibility of a myocardial signal intensity threshold-based semi-automated cardiac magnetic resonance segmentation method

AbstractObjectivesTo assess the accuracy and efficiency of a threshold-based, semi-automated cardiac MRI segmentation algorithm in comparison with conventional contour-based segmentation and aortic flow measurements.MethodsShort-axis cine images of 148 patients (55u2009±u200918xa0years, 81 men) were used to evaluate left ventricular (LV) volumes and mass (LVM) using conventional and threshold-based segmentations. Phase-contrast images were used to independently measure stroke volume (SV). LV parameters were evaluated by two independent readers.ResultsEvaluation times using the conventional and threshold-based methods were 8.4u2009±u20091.9 and 4.2u2009±u20091.3xa0min, respectively (Pu2009<u20090.0001). LV parameters measured by the conventional and threshold-based methods, respectively, were end-diastolic volume (EDV) 146u2009±u200959 and 134u2009±u200953xa0ml; end-systolic volume (ESV) 64u2009±u200947 and 59u2009±u200946xa0ml; SV 82u2009±u200929 and 74u2009±u200928xa0ml (flow-based 74u2009±u200930xa0ml); ejection fraction (EF) 59u2009±u200916 and 58u2009±u200917xa0%; and LVM 141u2009±u200955 and 159u2009±u200958xa0g. Significant differences between the conventional and threshold-based methodsxa0were observed in EDV, ESV, and LVM mesurements; SV from threshold-based and flow-based measurements were in agreement (Pu2009>u20090.05) but were significantly different from conventional analysis (Pu2009<u20090.05). Excellent inter-observer agreement was observed.ConclusionsThreshold-based LV segmentation provides improved accuracy and faster assessment compared to conventional contour-based methods.Key Points• Threshold-based left ventricular segmentation provides time-efficient assessment of left ventricular parametersn • The threshold-based method can discriminate between blood and papillary musclesn • This method provides improved accuracy compared to aortic flow measurements as a reference

Dynamic CT myocardial perfusion imaging

Non-invasive cardiac imaging has rapidly evolved during the last decade due to advancements in CT based technologies. Coronary CT angiography has been shown to reliably assess coronary anatomy and detect high risk coronary artery disease. However, this technique is limited to anatomical assessment, thus non-invasive techniques for functional assessment of the heart are necessary. CT myocardial perfusion is a new CT based technique that provides functional assessment of the myocardium and allows for a comprehensive assessment of coronary artery disease with a single modality when combined with CTA. This review aims to discuss dynamic CT myocardial perfusion as a new technique in the assessment of CAD.

Coronary CT angiography in obese patients using 3 rd generation dual-source CT: effect of body mass index on image quality

ObjectivesTo evaluate the image quality of coronary CT angiography (CCTA) in obese patients using a 3rd generation, dual-source CT scanner.MethodsWe retrospectively evaluated 102 overweight and obese patients who had undergone CCTA. Studies were performed with 3rd generation dual-source CT, prospectively ECG-triggered acquisition at 120xa0kV, and automated tube current modulation. Advanced modeled iterative reconstruction was used. Patients were divided into three BMI groups: 1)25–29.9xa0kg/m2; 2)30–39.9xa0kg/m2; 3)u2009≥u200940xa0kg/m2. Vascular attenuation in the coronary arteries was measured. Contrast-to-noise ratio (CNR) was calculated. Image quality was subjectively evaluated using five-point scales.ResultsImage quality was considered diagnostic in 97.6xa0% of examinations. CNR was consistently adequate in all groups but decreased for groups 2 and 3 in comparison to group 1 as well as for group 3 compared to group 2 (pu2009=u20090.001, respectively). Subjective image quality was significantly higher in group 1 compared to group 3 (attenuation proximal: 4.8u2009±u20090.4 vs. 4.4u2009±u20090.6, pu2009=u20090.011; attenuation distal: 4.5u2009±u20090.7 vs. 4.0u2009±u20090.8, pu2009=u20090.019; noise: 4.7u2009±u20090.6 vs. 3.8u2009±u20090.7, pu2009<u20090.001). The mean effective dose was 9.5u2009±u20093.9xa0mSv for group 1, 11.4u2009±u20094.7xa0mSv for group 2 and 14.0u2009±u20096.4xa0mSv for group 3.ConclusionDiagnostic image quality can be routinely obtained at CCTA in obese patients with 3rd generation DSCT at 120xa0kV.Key Points• Diagnostic CCTA can be routinely performed in obese patients with 3rdgeneration DSCT.• 120-kV tube voltage allows diagnostic image quality in patients with BMIu2009>u200940xa0kg/m2.• 80-ml contrast medium can be administered without significant decline in vascular attenuation.

A noise-optimized virtual monochromatic reconstruction algorithm improves stent visualization and diagnostic accuracy for detection of in-stent re-stenosis in lower extremity run-off CT angiography

AbstractPurposeTo evaluate the impact of noise-optimized virtual monochromatic imaging (VMI+) on stent visualization and accuracy for in-stent re-stenosis at lower extremity dual-energy CT angiography (DE-CTA).Material and methodsWe evaluated third-generation dual-source DE-CTA studies in 31 patients with prior stent placement. Images were reconstructed with linear blending (F_0.5) and VMI+ at 40–150xa0keV. In-stent luminal diameter was measured and contrast-to-noise ratio (CNR) calculated. Diagnostic confidence was determined using a five-point scale. In 21 patients with invasive catheter angiography, accuracy for significant re-stenosis (≥50xa0%) was assessed at F_0.5 and 80xa0keV-VMI+ chosen as the optimal energy level based on image-quality analysis.ResultsAt CTA, 45 stents were present. DSA was available for 28 stents whereas 12 stents showed significant re-stenosis. CNR was significantly higher with ≤80xa0keV-VMI+ (17.9u2009±u20096.4–33.7u2009±u200912.3) compared to F_0.5 (16.9u2009±u20094.8; all pu2009<u20090.0463); luminal stent diameters were increased at ≥70xa0keV (5.41u2009±u20091.8–5.92u2009±u20091.7 vs. 5.27u2009±u20091.8, all pu2009<u20090.001) and diagnostic confidence was highest at 70–80xa0keV-VMI+ (4.90u2009±u20090.48–4.88u2009±u20090.63 vs. 4.60u2009±u20090.66, pu2009=u20090.001, 0.0042). Sensitivity, negative predictive value and accuracy for re-stenosis were higher with 80xa0keV-VMI+ (100, 100, 96.4xa0%) than F_0.5 (90.9, 94.1, 89.3xa0%).Conclusion80xa0keV-VMI+ improves image quality, diagnostic confidence and accuracy for stent evaluation at lower extremity DE-CTA.Key Points• The impact of noise-optimized virtual monochromatic imaging on stent visualization was assessed.n • Virtual monochromatic imaging significantly improves stent lumen visualization and diagnostic confidence.n • At 80xa0keV diagnostic performance for detection of in-stent restenosis was increased.n • 80xa0keV virtual monochromatic images are recommended for stent evaluation of lower extremity vasculature.

Seventy-Peak Kilovoltage High-Pitch Thoracic Aortic CT Angiography without ECG Gating: Evaluation of Image Quality and Radiation Dose.

RATIONALE AND OBJECTIVESnTo assess the feasibility of 70-kVp high-pitch non-ECG-gated thoracic aortic computed tomography angiography (CTA) with 40-mL contrast agent compared to 100-kVp standard-pitch CTA with 60-mL contrast agent.nnnMATERIALS AND METHODSnSixty-seven patients (51 men and 16 women; mean age, 55 ± 14 years) received non-ECG-gated aortic CTA at 70 kVp, high pitch of 3.4, and 40-mL contrast agent (group A, n = 31) or CTA at 100-kVp, pitch of 1.2, and 60-mL contrast agent (group B, n = 36). Iterative reconstruction was used in all patients. For image quality assessment, CTA images were evaluated on a three-point scale and signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated and compared. Furthermore, computed tomography (CT) dose index was recorded.nnnRESULTSnMean CT values and noise levels were higher in group A compared to group B (all P < .001), whereas SNR and CNR were lower than those in group B (all P < .001). Furthermore, the image quality of the aorta at the level of the diaphragm was lower in group A than that in group B (P < .05). However, image quality was graded as diagnostic in all patients, and motion artifacts of the aortic arch were significantly decreased in group A (P <.05). Interreader agreement was good or excellent for image quality assessment (k = 0.625-0.835). The 70-kVp CTA protocol, which allows dose reduction of 85%, was considered diagnostic in all instances by two readers.nnnCONCLUSIONSnOur proposed thoracic aortic CTA protocol provides diagnostic information with substantial reduction of both radiation and contrast agent doses compared to standard-pitch CTA at 100 kVp.