Semi-automated volumetry of pulmonary nodules: Intra-individual comparison of standard dose and chest X-ray equivalent ultralow dose chest CT scans.

PURPOSE: To assess the performance of semi-automated volumetry of solid pulmonary nodules on single-energy tin-filtered ultralow dose (ULD) chest CT scans at a radiation dose equivalent to chest X-ray relative to standard dose (SD) chest CT scans and assess the impact of kernel and iterative reconstruction selection. METHODS: Ninety-four consecutive patients from a prospective single-center study were included and underwent clinically indicated SD chest CT (1.9 ± 0.8 mSv) and additional ULD chest CT (0.13 ± 0.01 mSv) in the same session. All scans were reconstructed with a soft tissue (Br40) and lung (Bl64) kernel as well as with Filtered Back Projection (FBP) and Iterative Reconstruction (ADMIRE-3 and ADMIRE-5). One hundred and forty-eight solid pulmonary nodules were identified and analysed by semi-automated volumetry on all reconstructions. Nodule volumes were compared amongst all reconstructions thereby focusing on the agreement between SD and ULD scans. RESULTS: Nodule volumes ranged from 58.5 (28.8-126) mm3 for ADMIRE-5 Br40 ULD reconstructions to 72.5 (39-134) mm3 for FBP Bl64 SD reconstructions with significant differences between reconstructions (p < 0.001). Interscan agreement of volumes between two given reconstructions ranged from ICC = 0.605 to ICC = 0.999. Between SD and ULD scans, agreement of nodule volumes was highest for FBP Br40 (ICC = 0.995), FBP Bl64 (ICC = 0.939) and ADMIRE-5 Bl64 (ICC = 0.994) reconstructions. ADMIRE-3 reconstructions exhibited reduced interscan agreement of nodule volumes (ICCs from 0.788 - 0.882). CONCLUSIONS: The interscan agreement of node volumes between SD and ULD is high depending on the choice of kernel and reconstruction algorithm. However, caution should be exercised when comparing two image series that were not identically reconstructed.

Comparison of virtual non-contrast dual-energy CT and a true non-contrast CT for contouring in radiotherapy of 3D printed lung tumour models in motion: a phantom study.

OBJECTIVES: This work aims to investigate whether virtual non-contrast (VNC) dual-energy CT(DECT) of contrasted lung tumours can be used as an alternative for true non-contrast (TNC) images in radiotherapy. Two DECT techniques and a TNC CT were compared and influences on gross tumour volume (GTV) volume and CT number from motion artefacts in three-dimensional printed lung tumour models (LTM) in amotion phantom were examined. METHODS: Two spherical LTMs (diameter 3.0 cm) with different inner shapes were created in a three-dimensional printer. The inner shapes contained water or iodine (concentration 5 mg ml-1) and were scanned with a dual-source DECT (ds-DECT), single-source sequential DECT (ss-DECT) and TNC CT in a respiratory motion phantom (15 breaths/min, amplitude 1.5 cm). CT number and volume of LTMs were measured. Therefore, two GTVs were contoured. RESULTS: Deviations in GTV volume (outer shape) of LTMs in motion for contrast-enhanced ss-DECT and ds-DECT VNC images compared to TNC images are not significant (p > 0.05). Relative GTV volume and CT number deviations (inner shapes) of LTMs in motion were 6.6 ± 0.6% and 104.4 ± 71.2 HU between ss-DECT and TNC CT and -8.4 ± 10.6% and 25.5 ± 58.5 HU between ds-DECT and TNC, respectively. CONCLUSION: ss-DECT VNC images could not sufficiently subtract iodine from water in LTMs inmotion, whereas ds-DECT VNC images might be a valid alternative to a TNC CT. ADVANCES IN KNOWLEDGE: ds-DECT provides a contrasted image for contouring and a non-contrasted image for radiotherapy treatment planning for LTM in motion.

Influence of contrast material density and kV setting on detectability of calcified plaques on coronary CT angiography.

PURPOSE: To analyze the impact of tube potential and iodine concentration on the visibility of calcified plaques in coronary computed tomography angiography (cCTA). METHODS & MATERIALS: 164 consecutive patients (65.9 % men and a mean age of 57.1 ±â€¯11.3 years) with suspected coronary artery disease underwent calcium scoring (CaSc) scan followed by cCTA with topogram-based automated tube voltage selection (70 kV, 80 kV, 90 kV, 100 kV or 120 kV). In 127 Patients (HC), we injected 50 mL of contrast material (CM) with a concentration of 400 mg iodine per ml and in 37 patients (LC) 50 mL iodine concentration of 280 mg/mL. Sensitivity of cCTA for detecting calcified plaques was calculated with CaSc serving as gold standard. Density of CM enhanced coronary vessels and calcified plaques were quantified by region-of-interest (ROI) measurements in unenhanced and cCTA image series. RESULTS: Overall sensitivity of cCTA to detect calcified plaques was significantly higher using LC compared to HC (79 % vs. 73 %; p = 0.0035). The impact of LC was impressive at 70 kV with an improved sensitivity of 70 % vs. 57.1 % in HC (p = 0.0082). Furthermore, density values of HC enhanced coronary vessels exceeded those of calcified plaques, especially at low kV levels. In LC, except for the 70 kV setting, higher density values were shown for calculi than enhanced vessels. CONCLUSION: Low kV cCTA in routine using highly concentrated CM leads to reduced calcified plaque perceptibility and hence potentially underestimation of stenosis. Thus, low kV cCTA using CM with lower iodine concentration is necessary. In addition, a dose reduction up to 77.7 % can also be benefited.

Chest X-ray Dose Equivalent Low-dose CT with Tin Filtration: Potential Role for the Assessment of Pectus Excavatum.

RATIONALE AND OBJECTIVES: To determine the value of chest CT with tin filtration applying a dose equivalent to chest x-ray for the assessment of the Haller index for evaluation of pectus excavatum. MATERIALS AND METHODS: Two hundred seventy-two patients from a prospective single center study were included and underwent a clinical standard dose chest CT (effective dose 1.8 ± 0.7 mSv) followed by a low-dose CT (0.13 ± 0.01 mSv) in the same session. Two blinded readers independently evaluated all data sets. Image quality for bony chest wall assessment was noted. Radiologists further assessed (a) transverse thoracic diameter, (b) anteroposterior thoracic diameter, and calculated (c) Haller index by dividing transverse diameter by anteroposterior diameter. The agreement of both readers in standard dose and low-dose CT was assessed using Lin's concordance correlation coefficient (pc). RESULTS: Subjective image quality was lower for low dose compared to standard dose CT images by both readers (p < 0.001). In total, 99% (n = 540) of low-dose CT scans were rated as diagnostic for bony chest wall assessment by both readers. There was a high agreement for assessment of transverse diameter, anteroposterior diameter and Haller index comparing both readers in standard dose and low-dose CT with pc values indicating substantial agreement (i.e., 0.95> and ≤0.99) in 12/18 (67%) and almost perfect agreement (i.e., >0.99) in 6/18 (33%). CONCLUSION: Our study suggests that low-dose CT with tin filtration applying a radiation dose equivalent to a plain chest X-ray is excellent for assessing the Haller index.

Lung cancer screening with submillisievert chest CT: Potential pitfalls of pulmonary findings in different readers with various experience levels.

PURPOSE: To assess the interreader variability of submillisievert CT for lung cancer screening in radiologists with various experience levels. METHOD: Six radiologists with different degrees of clinical experience in radiology (range, 1-15 years), rated 100 submillisievert CT chest studies as either negative screening finding (no nodules, benign nodules, nodules <5 mm), indeterminate finding (nodules 5-10 mm), positive finding (nodules >10 mm). Each radiologist interpreted scans randomly ordered and reading time was recorded. Interobserver agreement was assessed with ak statistic. Reasons for differences in nodule classification were analysed on a case-by-case basis. Reading time was correlated with reader experience using Pearson correlation (r). RESULTS: The overall interobserver agreement between all readers was moderate (k = 0.454; p < 0.001). In 57 patients, all radiologists agreed on the differentiation of negative and indeterminate/positive finding. In 64 cases disagreement between readers led to different nodule classification. In 8 cases some readers rated the nodule as benign, whereas others scored the case as positive. Overall, disagreement in nodule classification was mostly due to failure in identification of target lesion (n = 40), different lesion measurement (n = 44) or different classification (n = 26). Mean overall reading time per scan was of 2 min 2 s (range: 7s-7 min 45 s) and correlated with reader-experience (r = -0.824). CONCLUSIONS: Our study showed substantial interobserver variability for the detection and classification of pulmonary nodules in submillisievert CT. This highlights the importance for careful standardisation of screening programs with the objective of harmonizing efforts of involved radiologists across different institutions by defining and assuring quality standards.

EANM guideline for ventilation/perfusion single-photon emission computed tomography (SPECT) for diagnosis of pulmonary embolism and beyond.

These guidelines update the previous EANM 2009 guidelines on the diagnosis of pulmonary embolism (PE). Relevant new aspects are related to (a) quantification of PE and other ventilation/perfusion defects; (b) follow-up of patients with PE; (c) chronic PE; and (d) description of additional pulmonary physiological changes leading to diagnoses of left ventricular heart failure (HF), chronic obstructive pulmonary disease (COPD) and pneumonia. The diagnosis of PE should be reported when a mismatch of one segment or two subsegments is found. For ventilation, Technegas or krypton gas is preferred over diethylene triamine pentaacetic acid (DTPA) in patients with COPD. Tomographic imaging with V/PSPECT has higher sensitivity and specificity for PE compared with planar imaging. Absence of contraindications makes V/PSPECT an essential method for the diagnosis of PE. When V/PSPECT is combined with a low-dose CT, the specificity of the test can be further improved, especially in patients with other lung diseases. Pitfalls in V/PSPECT interpretation are discussed. In conclusion, V/PSPECT is strongly recommended as it accurately establishes the diagnosis of PE even in the presence of diseases like COPD, HF and pneumonia and has no contraindications.

Enhanced radiation exposure associated with anterior-posterior x-ray tube position in young women undergoing cardiac computed tomography.

Given the current increase in the incidence of coronary artery disease in younger women as well as the high lifetime risk of developing an x-ray-induced malignancy in this population, we aimed at assessing chest radiation in 206 women ≤55 years old undergoing coronary calcium scoring (CACS) by using a Monte Carlo simulation tool. Our data indicate that the simulated radiation dose of the female breast during CACS depends substantially on the starting position of the x-ray tube, with an almost 2 times excess of breast radiation exposure being measured during anterior-posterior tube positioning. Thus, an additional technical feature taking into account the position of the x-ray tube when acquisition is triggered might be an important tool to reduce radiation exposure of the female breast during CACS.

Dynamic 4D-CT Angiography for Guiding Transarterial Chemoembolization: Impact on the Reduction of Contrast Material, Operator Radiation Exposure, Catheter Consumption, and Diagnostic Confidence.

PURPOSE: This study was carried out to investigate the impact of abdominal dynamic four-dimensional CT angiography (4D-CTA) for guiding transarterial chemoembolization (TACE) on the amount of contrast material used, operator radiation exposure, catheter consumption, and diagnostic confidence. MATERIALS AND METHODS: Written consent was waived for this IRB-approved retrospective study. 29 patients (20 men; mean age: 65.7 ±â€Š11.5 years) with malignant liver lesions underwent 4D-CTA, prior to initial TACE. Time-resolved volume-rendering technique (VRT), maximum-intensity projection (MIP), and multiplanar reconstruction (MPR) series were reconstructed, enabling a direct selective catheterization of the tumor-supplying artery without prior conventional digital subtraction angiography (DSA). 29 patients (16 men; mean age: 69.4 ±â€Š13.9) who underwent traditional TACE served as the control group. The amount of administered contrast media, operator radiation exposure, and catheter consumption during TACE were compared. Two radiologists assessed diagnostic confidence in the exclusion of portal vein thrombosis. RESULTS: 4D-CTA TACE resulted in a significant reduction in the amount of contrast media used, compared to traditional TACE (-61.0 ml/ -66.3 % intra-arterial, -12.8 ml/ -13.8 % overall; P < 0.001). The dose-area product indicating operator radiation exposure during intervention was reduced by 50.5 % (P < 0.001), and 0.7 fewer catheters on average were used (P = 0.063), while 4D-CTA data was available to guide TACE. Diagnostic confidence in the exclusion of portal vein thrombosis was significantly enhanced by 4D-CTA, compared to traditional DSA images (scores, 3.9 and 2.4, respectively; P < 0.001). CONCLUSION: Dynamic 4D-CTA enables TACE with a substantially reduced amount of contrast material, decreases operator radiation exposure, and increases diagnostic confidence in the exclusion of portal vein thrombosis. KEY POINTS: · 4D-CTA prior to TACE decreases the amount of utilized contrast material.. · The intra-arterial fraction of contrast media can be reduced by two-thirds.. · The risk of CIN may be decreased by means of 4D-CTA TACE.. · Operator radiation exposure is lower using 4D-CTA for guiding TACE.. · 4D-CTA portography allows for a higher diagnostic confidence than conventional DSA images.. CITATION FORMAT: · Albrecht MH, Vogl TJ, Wichmann JL et al. Dynamic 4D-CT Angiography for Guiding Transarterial Chemoembolization: Impact on the Reduction of Contrast Material, Operator Radiation Exposure, Catheter Consumption, and Diagnostic Confidence. Fortschr Röntgenstr 2018; 190: 513 - 520.

Dual-Energy Computed Tomography-Based Display of Bone Marrow Edema in Incidental Vertebral Compression Fractures: Diagnostic Accuracy and Characterization in Oncological Patients Undergoing Routine Staging Computed Tomography.

PURPOSE: The aim of this study was to evaluate the diagnostic performance of virtual noncalcium (VNCa) dual-energy computed tomography (DECT) reconstructions enabling visualization of bone marrow edema for characterization of incidental thoracolumbar compression fractures in routine thoracoabdominal staging computed tomography (CT). MATERIALS AND METHODS: We retrospectively analyzed 51 oncological patients without suspected fracture or indicative complaints presenting at least 1 thoracolumbar compression fracture on routine thoracoabdominal staging DECT who had been examined between October 2015 and June 2017 using third-generation dual-source CT, had a previous CT within 3 months before, and also had undergone additional magnetic resonance imaging within 14 days, which served as the standard of reference. Three independent and blinded radiologists initially evaluated all vertebrae on conventional grayscale DECT series; after at least 8 weeks, observers reevaluated all cases using grayscale and color-coded VNCa DECT images. The age of each fracture was determined as either acute, chronic, or inconclusive. Specificity, sensitivity, and intraobserver and interobserver agreements were calculated taking into account clustering. RESULTS: A total of 98 vertebral compression fractures were detected in 51 patients (20 women, 31 men; median of 1 fracture per patient). The reference standard defined 45 as acute and 53 as chronic. For identification of only acute fractures (cutoff 1), the combination of grayscale and VNCa image series showed a higher sensitivity (91% vs 47%; P < 0.001) but equal specificity (both 100%) compared with analysis of grayscale images alone. When defining a positive finding as a fracture considered either acute or inconclusive (cutoff 2), combined analysis of grayscale and VNCa images showed similar sensitivity (96% vs 93%; P = 0.28) but significantly higher specificity (96% vs 75%; P < 0.001) compared with evaluation of grayscale images alone. Area under the curve analysis for detection of vertebral compression fractures showed superior results for reading of grayscale and VNCa image series (0.98) compared with analysis of grayscale images alone (0.89; P < 0.001). CONCLUSION: Dual-energy CT-derived color-coded VNCa reconstructions substantially improve the characterization of incidental thoracolumbar compression fractures seen on routine thoracoabdominal staging DECT by allowing for visualization of bone marrow edema.

Using coronary CT angiography for guiding invasive coronary angiography: potential role to reduce intraprocedural radiation exposure.

OBJECTIVES: We investigated the potential reduction of patient exposure during invasive coronary angiography (ICA) if the procedure had only been directed to the vessel with at least one ≥ 50% stenosis as described in the CT report. METHODS: Dose reports of 61 patients referred to ICA because of at least one ≥ 50% stenosis on coronary CT angiography (CCTA) were included. Dose-area product (DAP) was documented separately for left (LCA) and right coronary arteries (RCA) by summing up the single DAP for each angiographic projection. The study population was subdivided as follows: coronary intervention of LCA (group 1) or RCA (group 2) only, or of both vessels (group 3), or further bypass grafting (group 4), or no further intervention (group 5). RESULTS: 57.4% of the study population could have benefitted from reduced exposure if catheterization had been directly guided to the vessel of interest as described on CCTA. Mean relative DAP reductions were as follows: group 1 (n = 18), 11.2%; group 2 (n = 2), 40.3%; group 3 (n = 10), 0%; group 4 (n = 3), 0%; group 5 (n = 28), 28.8%. CONCLUSIONS: Directing ICA to the vessel with stenosis as described on CCTA would reduce intraprocedural patient exposure substantially, especially for patients with single-vessel stenosis. KEY POINTS: • Patients with CAD can benefit from decreased radiation exposure during coronary angiography. • ICA should be directed solely to significant stenoses as described on CCTA. • Severely calcified plaques remain a limitation of CCTA leading to unnecessary ICA referrals.

Evaluation of an adaptive detector collimation for prospectively ECG-triggered coronary CT angiography with third-generation dual-source CT.

OBJECTIVES: To investigate the impact of an adaptive detector collimation on the dose parameters and accurateness of scan length adaption at prospectively ECG-triggered sequential cardiac CT with a wide-detector third-generation dual-source CT. METHODS: Ideal scan lengths for human hearts were retrospectively derived from 103 triple-rule-out examinations. These measures were entered into the new scanner operated in prospectively ECG-triggered sequential cardiac scan mode with three different detector settings: (1) adaptive collimation, (2) fixed 64 × 0.6-mm collimation, and (3) fixed 96 × 0.6-mm collimation. Differences in effective scan length and deviation from the ideal scan length and dose parameters (CTDIvol, DLP) were documented. RESULTS: The ideal cardiac scan length could be matched by the adaptive collimation in every case while the mean scanned length was longer by 15.4% with the 64 × 0.6 mm and by 27.2% with the fixed 96 × 0.6-mm collimation. While the DLP was almost identical between the adaptive and the 64 × 0.6-mm collimation (83 vs. 89 mGycm at 120 kV), it was 62.7% higher with the 96 × 0.6-mm collimation (135 mGycm), p < 0.001. CONCLUSION: The adaptive detector collimation for prospectively ECG-triggered sequential acquisition allows for adjusting the scan length as accurate as this can only be achieved with a spiral acquisition. This technique allows keeping patient exposure low where patient dose would significantly increase with the traditional step-and-shoot mode. KEY POINTS: • Adaptive detector collimation allows keeping patient exposure low in cardiac CT. • With novel detectors the desired scan length can be accurately matched. • Differences in detector settings may cause 62.7% of excessive dose.

High-pitch dual-source paranasal sinus CT in agitated patients with maxillofacial trauma: analysis of image quality, motion artifacts, and dose aspects.

Background Image quality benefits from high-pitch scanning in agitated patients by reducing acquisition time. Purpose To compare image quality and exposure parameters in patients with maxillofacial trauma on second- and third-generation dual-source computed tomography (DSCT). Material and Methods Four groups were compared. Group 1 was examined on second-generation DSCT (120 kV/50 mAs, pitch 3.0). The other three groups were examined on third-generation DSCT. Group 2 was scanned with 120 kV/50 mAs, pitch 2.2. Automated exposure control (AEC) was used in group 3 and group 4 with pitch factors of 2.2 and 3.0, respectively. Images of third-generation DSCT were reconstructed with iterative reconstruction (IR), of second-generation DSCT with filtered back-projection. CTDIvol, acquisition time, and image quality were compared. Results Thirty patients were included in each group. Average CTDIvol (2.76 ± 0.00 mGy, 2.66 ± 0.00 mGy, 0.74 ± 0.23 mGy, and 0.75 ± 0.17 mGy) was significantly lower on third-generation DSCT with AEC ( P < 0.001). Subjective image quality was rated worst in group 4 due to strong high-pitch artifacts, while in the remaining three groups it was rated good or very good with good inter-observer agreement (k > 0.64). Average acquisition time was significantly shorter with third-generation DSCT (0.47 s, 0.36 s, 0.38 s, 0.30 s; P < 0.001). Conclusion Third-generation DSCT yields faster acquisition times and substantial dose reduction with AEC. A pitch of 2.2 should be preferred, as it results in fewer artifacts. If AEC is used, latest IR ensures that diagnostic image quality is guaranteed.

Coronary risk assessment at X-ray dose equivalent ungated chest CT: Results of a multi-reader study.

OBJECTIVES: To determine the value of ultra-low dose chest CT with tin filtration for ordinal coronary artery calcium (CAC) risk scoring. METHODS: 50 patients were prospectively included and underwent clinical standard dose chest CT (1.8±0.7mSv) and ultra-low dose CT (0.13±0.01mSv). Four radiologists estimated presence and extent of CAC. RESULTS: Weighted kappa values for CAC were 0.76-0.97 in standard dose and 0.75-0.95 in ultra-low dose CT (p<0.001). Good to excellent agreement was observed for CAC ordinal risk assessment, with readers reporting identical risk in 81% of cases. CONCLUSION: CAC risk can be qualitatively assessed from X-ray dose equivalent ungated chest CT.

Diagnostic accuracy of chest X-ray dose-equivalent CT for assessing calcified atherosclerotic burden of the thoracic aorta.

OBJECTIVE: To determine the value of ultralow-dose chest CT for estimating the calcified atherosclerotic burden of the thoracic aorta using tin-filter CT and compare its diagnostic accuracy with chest direct radiography. METHODS: A total of 106 patients from a prospective, IRB-approved single-centre study were included and underwent standard dose chest CT (1.7 ± 0.7 mSv) by clinical indication followed by ultralow-dose CT with 100 kV and spectral shaping by a tin filter (0.13 ± 0.01 mSv) to achieve chest X-ray equivalent dose in the same session. Two independent radiologists reviewed the CT images, rated image quality and estimated presence and extent of calcification of aortic valve, ascending aorta and aortic arch. Conventional radiographs were also reviewed for presence of aortic calcifications. RESULTS: The sensitivity of ultralow-dose CT for the detection of calcifications of the aortic valve, ascending aorta and aortic arch was 93.5, 96.2 and 96.2%, respectively, compared with standard dose CT. The sensitivity for the detection of thoracic aortic calcification was significantly lower on chest X-ray (52.3%) compared with ultralow-dose CT (p < 0.001). CONCLUSION: A reliable estimation of calcified atherosclerotic burden of the thoracic aorta can be achieved with modern tin-filter CT at dose values comparable to chest direct radiography. Advances in knowledge: Our findings suggest that ultralow-dose CT is an excellent tool for assessing the calcified atherosclerotic burden of the thoracic aorta with higher diagnostic accuracy than conventional chest radiography and importantly without the additional cost of increased radiation dose.

Emphysema quantification and lung volumetry in chest X-ray equivalent ultralow dose CT - Intra-individual comparison with standard dose CT.

OBJECTIVES: To determine whether ultralow dose chest CT with tin filtration can be used for emphysema quantification and lung volumetry and to assess differences in emphysema measurements and lung volume between standard dose and ultralow dose CT scans using advanced modeled iterative reconstruction (ADMIRE). METHODS: 84 consecutive patients from a prospective, IRB-approved single-center study were included and underwent clinically indicated standard dose chest CT (1.7±0.6mSv) and additional single-energy ultralow dose CT (0.14±0.01mSv) at 100kV and fixed tube current at 70mAs with tin filtration in the same session. Forty of the 84 patients (48%) had no emphysema, 44 (52%) had emphysema. One radiologist performed fully automated software-based pulmonary emphysema quantification and lung volumetry of standard and ultralow dose CT with different levels of ADMIRE. Friedman test and Wilcoxon rank sum test were used for multiple comparison of emphysema and lung volume. Lung volumes were compared using the concordance correlation coefficient. RESULTS: The median low-attenuation areas (LAA) using filtered back projection (FBP) in standard dose was 4.4% and decreased to 2.6%, 2.1% and 1.8% using ADMIRE 3, 4, and 5, respectively. The median values of LAA in ultralow dose CT were 5.7%, 4.1% and 2.4% for ADMIRE 3, 4, and 5, respectively. There was no statistically significant difference between LAA in standard dose CT using FBP and ultralow dose using ADMIRE 4 (p=0.358) as well as in standard dose CT using ADMIRE 3 and ultralow dose using ADMIRE 5 (p=0.966). In comparison with standard dose FBP the concordance correlation coefficients of lung volumetry were 1.000, 0.999, and 0.999 for ADMIRE 3, 4, and 5 in standard dose, and 0.972 for ADMIRE 3, 4 and 5 in ultralow dose CT. CONCLUSIONS: Ultralow dose CT at chest X-ray equivalent dose levels allows for lung volumetry as well as detection and quantification of emphysema. However, longitudinal emphysema analyses should be performed with the same scan protocol and reconstruction algorithms for reproducibility.

Predictive value of perfusion defects on dual energy CTA in the absence of thromboembolic clots.

BACKGROUND: To determine the predictive value of volumetrically measured lung perfusion defects (PDvol) and right ventricular dysfunction on dual-energy computed tomography angiography (DE-CTA) for predicting all cause mortality in patients suspected of pulmonary embolism (PE) but without evident thromboembolic clot on CTA. METHODS: 448 patients underwent DE-CTA on a 64-channel DSCT system between January 2007 and December 2012 for suspected PE, of which 115 were without detectable thromboembolic clot on CTA. Diagnostic performance for identifying patients at risk of dying was evaluated using ROC analysis. All-cause mortality was assessed via the hospital electronic medical records and/or consultation of the patient or the patient's primary care physician via phone call interviews. Sensitivity, specificity, positive likelihood ratio, negative likelihood ratio and area under the curve (AUC) were determined for PDvol (volume of perfusion defects/total lung volume), transverse right ventricular to left ventricular diameter ratios (RV/LV) and for the combination of both tests. RESULTS: Mortality was 38% within the investigated time period of 6 months. Patients who died had significantly higher PDvol (PDvol 28 ± 13% vs. 19 ± 12%, p < 0.001) and a non-significant difference in transverse RV/LV ratio (1.14 ± 0.37 vs. 1.06 ± 0.22, p = 0.159). The AUC was 0.71 for PDvol, 0.53 for RV/LV ratio, and 0.67 for the combination of PDvol and RV/LV ratio. PDvol remained a significant predictor after correcting for age. CONCLUSIONS: In the absence of thromboembolic clots, PDvol at DE-CTA appears to be predictive for all cause mortality.

Detecting Intracranial Hemorrhage Using Automatic Tube Current Modulation With Advanced Modeled Iterative Reconstruction in Unenhanced Head Single- and Dual-Energy Dual-Source CT.

OBJECTIVE: The purpose of our study was to determine diagnostic accuracy, image quality, and radiation dose of low-dose single- and dual-energy unenhanced third-generation dual-source head CT for detection of intracranial hemorrhage (ICH). MATERIALS AND METHODS: A total of 123 patients with suspected ICH were examined using a dual-source 192-MDCT scanner. Standard-dose 120-kVp single-energy CT (SECT; n = 36) and 80-kVp and 150-kVp dual-energy CT (DECT; n = 30) images were compared with low-dose SECT (n = 32) and DECT (n = 25) images obtained using automated tube current modulation (ATCM). Advanced modeled iterative reconstruction (ADMIRE) was used for all protocols. Detection of ICH was performed by three readers who were blinded to the image acquisition parameters of each image series. Image quality was assessed both quantitatively and qualitatively. Interobserver agreement was calculated using the Fleiss kappa. Radiation dose was measured as dose-length product (DLP). RESULTS: Detection of ICH was excellent (sensitivity, 94.9-100%; specificity, 94.7-100%) in all protocols (p = 1.00) with perfect interobserver agreement (0.83-0.96). Qualitative ratings showed significantly better ratings for both standard-dose protocols regarding gray matter-to-white matter contrast (p ≤ 0.014), whereas highest gray matter-to-white matter contrast-to-noise ratio was observed with low-dose DECT images (p ≥ 0.057). The lowest posterior fossa artifact index was measured for standard-dose DECT, which showed significantly lower values compared with low-dose protocols (p ≤ 0.034). Delineation of ventricular margins and sharpness of subarachnoidal spaces were rated excellent in all protocols (p ≥ 0.096). Low-dose techniques lowered radiation dose by 26% for SECT images (DLP, 575.0 ± 72.3 mGy · cm vs 771.5 ± 146.8 mGy · cm; p < 0.001) and by 24% in DECT images (DLP, 587.0 ± 103.2 mGy · cm vs 770.6 ± 90.2 mGy · cm; p < 0.001). No significant difference was observed between the low-dose protocols (p = 1.00). CONCLUSION: Low-dose unenhanced head SECT and DECT using ATCM and ADMIRE provide excellent diagnostic accuracy for detection of ICH with good quantitative and qualitative image quality in third-generation dual-source CT while allowing significant radiation dose reduction.

Ultralow dose CT for pulmonary nodule detection with chest x-ray equivalent dose - a prospective intra-individual comparative study.

PURPOSE: To prospectively evaluate the accuracy of ultralow radiation dose CT of the chest with tin filtration at 100 kV for pulmonary nodule detection. MATERIALS AND METHODS: 202 consecutive patients undergoing clinically indicated chest CT (standard dose, 1.8 ± 0.7 mSv) were prospectively included and additionally scanned with an ultralow dose protocol (0.13 ± 0.01 mSv). Standard dose CT was read in consensus by two board-certified radiologists to determine the presence of lung nodules and served as standard of reference (SOR). Two radiologists assessed the presence of lung nodules and their locations on ultralow dose CT. Sensitivity and specificity of the ultralow dose protocol was compared against the SOR, including subgroup analyses of different nodule sizes and types. A mixed effects logistic regression was used to test for independent predictors for sensitivity of pulmonary nodule detection. RESULTS: 425 nodules (mean diameter 3.7 ± 2.9 mm) were found on SOR. Overall sensitivity for nodule detection by ultralow dose CT was 91%. In multivariate analysis, nodule type, size and patients BMI were independent predictors for sensitivity (p < 0.001). CONCLUSIONS: Ultralow dose chest CT at 100 kV with spectral shaping enables a high sensitivity for the detection of pulmonary nodules at exposure levels comparable to plain film chest X-ray. KEYPOINTS: • 91% of all lung nodules were detected with ultralow dose CT • Sensitivity for subsolid nodule detection is lower in ultralow dose CT (77.5%) • The mean effective radiation dose in 202 patients was 0.13 mSv • Ultralow dose CT seems to be feasible for lung cancer screening.

Value of a noise-optimized virtual monoenergetic reconstruction technique in dual-energy CT for planning of transcatheter aortic valve replacement.

OBJECTIVES: To evaluate objective and subjective image quality of a noise-optimized virtual monoenergetic imaging (VMI+) reconstruction technique in dual-energy computed tomography (DECT) angiography prior to transcatheter aortic valve replacement (TAVR). METHODS: Datasets of 47 patients (35 men; 64.1 ± 10.9 years) who underwent DECT angiography of heart and vascular access prior to TAVR were reconstructed with standard linear blending (F_0.5), VMI+, and traditional monoenergetic (VMI) algorithms in 10-keV intervals from 40-100 keV. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of 564 arterial segments were evaluated. Subjective analysis was rated by three blinded observers using a Likert scale. RESULTS: Mean SNR and CNR were highest in 40 keV VMI+ series (SNR, 27.8 ± 13.0; CNR, 26.3 ± 12.7), significantly (all p < 0.001) superior to all VMI series, which showed highest values at 70 keV (SNR, 18.5 ± 7.6; CNR, 16.0 ± 7.4), as well as linearly-blended F_0.5 series (SNR, 16.8 ± 7.3; CNR, 13.6 ± 6.9). Highest subjective image quality scores were observed for 40, 50, and 60 keV VMI+ reconstructions (all p > 0.05), significantly superior to all VMI and standard linearly-blended images (all p < 0.01). CONCLUSIONS: Low-keV VMI+ reconstructions significantly increase CNR and SNR compared to VMI and standard linear-blending image reconstruction and improve subjective image quality in preprocedural DECT angiography in the context of TAVR planning. KEY POINTS: • VMI+ combines increased contrast with reduced image noise. • VMI+ shows substantially less image noise than traditional VMI. • 40-keV reconstructions show highest SNR/CNR of the aortic and iliofemoral access route. • Observers overall prefer 60 keV VMI+ images. • VMI+ DECT imaging helps improve image quality for TAVR planning.

Free-breathing dynamic liver examination using a radial 3D T1-weighted gradient echo sequence with moderate undersampling for patients with limited breath-holding capacity.

PURPOSE: To compare free-breathing radial VIBE with moderate undersampling (us-radial-VIBE) with a standard breathhold T1-weighted volumetric interpolated sequence (3D GRE VIBE) in patients unable to suspend respiration during dynamic liver examination. MATERIAL AND METHODS: 23 consecutive patients underwent dynamic liver MR examination using the free-breathing us-radial-VIBE sequence as part of their oncologic follow-up. All patients were eligible for the free-breathing protocol due to severe respiratory artifacts at the planning or precontrast sequences. The us-radial-VIBE acquisitions were compared to the patients last staging liver MRI including a standard breathhold 3D GRE VIBE. For an objective image evaluation, signal intensity (SI), image noise (IN), signal-to-noise ratio (SNR) and contrast-enhancement ratio (CER) were compared. Representative image quality parameters, including typical artifacts were independently, retrospectively and blindly scored by four readers. RESULTS: Us-radial-VIBE had significant lower SNR (p<0.0001) and higher IN (p<0.0001), whereas SI did not differ (p=0.62). Temporal resolution assessed with CER in the arterial phase showed higher values for us-radial-VIBE (p=0.028). Subjective image quality parameters received generally slightly higher scores for 3D GRE VIBE. In a smaller subgroup comprising patients with severe respiratory artifacts also at reference breathhold 3D GRE VIBE examination, us-radial-VIBE showed significantly higher image quality scores. Furthermore, there were generally more severe respiratory artifacts in 3D GRE VIBE, whereas streaking was characteristic in almost all us-radial-VIBE acquisitions but did not affect diagnostic validity. CONCLUSION: Free-breathing dynamic liver imaging using us-radial-VIBE delivers accurate temporal resolution, low motion artifact susceptibility and good image quality and represents a promising alternative in patients unable to suspend respiration.