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

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

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.

Low contrast media volume in pre-TAVI CT examinations.

PURPOSE: To evaluate image quality using reduced contrast media (CM) volume in pre-TAVI assessment. METHODS: Forty-seven consecutive patients referred for pre-TAVI examination were evaluated. Patients were divided into two groups: group 1 BMI < 28 kg/m(2) (n = 29); and group 2 BMI > 28 kg/m(2) (n = 18). Patients received a combined scan protocol: retrospective ECG-gated helical CTA of the aortic root (80kVp) followed by a high-pitch spiral CTA (group 1: 70 kV; group 2: 80 kVp) from aortic arch to femoral arteries. All patients received one bolus of CM (300 mgI/ml): group 1: volume = 40 ml; flow rate = 3 ml/s, group 2: volume = 53 ml; flow rate = 4 ml/s. Attenuation values (HU) and contrast-to-noise ratio (CNR) were measured at the levels of the aortic root (helical) and peripheral arteries (high-pitch). Diagnostic image quality was considered sufficient at attenuation values > 250HU and CNR > 10. RESULTS: Diagnostic image quality for TAVI measurements was obtained in 46 patients. Mean attenuation values and CNR (HU ± SD) at the aortic root (helical) were: group 1: 381 ± 65HU and 13 ± 8; group 2: 442 ± 68HU and 10 ± 5. At the peripheral arteries (high-pitch), mean values were: group 1: 430 ± 117HU and 11 ± 6; group 2: 389 ± 102HU and 13 ± 6. CONCLUSION: CM volume can be substantially reduced using low kVp protocols, while maintaining sufficient image quality for the evaluation of aortic root and peripheral access sites. KEY POINTS: • Image quality could be maintained using low kVp scan protocols. • Low kVp protocols reduce contrast media volume by 34-67 %. • Less contrast media volume lowers the risk of contrast-induced nephropathy.

Clinically Relevant Extracardiac Findings at Cardiac Imaging: Insights from the European MR/CT Registry.

Purpose To determine the prevalence of clinically relevant extracardiac findings at cardiac CT and MRI examinations from a multicenter, multinational MR/CT registry and the relationship of prevalence with examination indications and patient characteristics. Materials and Methods This was a retrospective analysis of data from the European Society of Cardiovascular Radiology MR/CT Registry. Data from 208 506 cardiac CT examinations (median patient age, 66 years [IQR, 55-77]; 121 617 [58.33%] male patients) and 228 462 cardiac MRI examinations (median patient age, 57 years [IQR, 42-69]; 145 792 [63.81%] male patients) entered into the registry between January 2011 and November 2023 were analyzed. Clinically relevant extracardiac findings were defined as findings requiring follow-up examinations or influencing clinical management. The association of examination indication and patient characteristics, including age, with prevalence of extracardiac findings was evaluated using incidence rate ratios (IRRs) derived from multivariable Poisson regression models. Results The prevalence of clinically relevant extracardiac findings was 3.28% (6832 of 208 506) at cardiac CT and 1.50% (3421 of 228 462) at cardiac MRI examinations. Extracardiac findings were more common at CT examinations performed for transcatheter aortic valve replacement (IRR, 2.07; P < .001) and structural heart disease (IRR, 1.44; P < .001) compared with CT performed for coronary artery disease (IRR, 1; reference). Extracardiac findings were more common at MRI examinations performed for myocarditis (IRR, 1.36; P < .001) and structural heart disease (IRR, 1.16; P < .001) than for coronary artery disease. Older patient age was also significantly associated with higher prevalence of extracardiac findings, with an IRR for both CT and MRI examinations of 1.02 (P < .001). Conclusion Data from the multicenter, multinational MR/CT registry indicate that clinically relevant extracardiac findings are present at cardiovascular CT and MRI examinations, and the prevalence of these findings is associated with examination indication and patient age. Keywords: Cardiac Imaging Techniques, Incidental Findings, MRI, CT Angiography, CT, Heart Disease Supplemental material is available for this article. © RSNA, 2024.

Interrater Variability of ML-Based CT-FFR in Patients without Obstructive CAD before TAVR: Influence of Image Quality, Coronary Artery Calcifications, and Location of Measurement.

Objectives: CT-derived fractional flow reserve (CT-FFR) can improve the specificity of coronary CT-angiography (cCTA) for ruling out relevant coronary artery disease (CAD) prior to transcatheter aortic valve replacement (TAVR). However, little is known about the reproducibility of CT-FFR and the influence of diffuse coronary artery calcifications or segment location. The objective was to assess the reliability of machine-learning (ML)-based CT-FFR prior to TAVR in patients without obstructive CAD and to assess the influence of image quality, coronary artery calcium score (CAC), and the location of measurement within the coronary tree. Methods: Patients assessed for TAVR, without obstructive CAD on cCTA were evaluated with ML-based CT-FFR by two observers with differing experience. Differences in absolute values and categorization into hemodynamically relevant CAD (CT-FFR ≤ 0.80) were compared. Results in regard to CAD were also compared against invasive coronary angiography. The influence of segment location, image quality, and CAC was evaluated. Results: Of the screened patients, 109/388 patients did not have obstructive CAD on cCTA and were included. The median (interquartile range) difference of CT-FFR values was -0.005 (-0.09 to 0.04) (p = 0.47). Differences were smaller with high values. Recategorizations were more frequent in distal segments. Diagnostic accuracy of CT-FFR between both observers was comparable (proximal: Δ0.2%; distal: Δ0.5%) but was lower in distal segments (proximal: 98.9%/99.1%; distal: 81.1%/81.6%). Image quality and CAC had no clinically relevant influence on CT-FFR. Conclusions: ML-based CT-FFR evaluation of proximal segments was more reliable. Distal segments with CT-FFR values close to the given threshold were prone to recategorization, even if absolute differences between observers were minimal and independent of image quality or CAC.

CT-derived coronary artery calcium density is affected by regional lesion distribution and image reconstruction parameters.

PURPOSE: The prognostic relevance of coronary artery calcium (CAC) density, assessed from cardiac CT scans, is established. However, the influence of CAC distribution, volume, image reconstruction, and clinical factors on CAC density warrants further examination. METHODS: In this study, 120 patients underwent non-contrast ECG-gated cardiac CT scans using a prospectively defined CAC scoring protocol with 1-, 3-, and 5-mm thick image reconstructions, both with and without a 20% image overlap. We segmented CAC in all reconstructions and assessed the relationship between CAC density, volume, and number of detected calcifications/patient. RESULTS: Overall, 75/120 (63%) patients (66% men, mean age 63 ± 11 years) presented CAC across 342 segments. CAC density, CAC volume, and the number of detected calcifications decreased with increasing slice thickness (p < 0.001 for all); these effects were slightly reduced by image overlap (p < 0.001 for all). Higher CAC density correlated with greater CAC volume (ρ = 0.62; p < 0.001) and more calcified segments per person (ρ = 0.32; p = 0.006). Higher CAC density was also associated with lower patient weight (beta: -0.6, 95%CI: -1.1--0.1, p = 0.022) and increased high-density lipoprotein (HDL) levels (beta: 0.7, 95%CI: 0.0-1.4, p = 0.046). In a multivariable analysis adjusted for clinical covariates, lower CAC density was associated with broader CAC distribution (i.e., a higher number of calcified segments at a given CAC volume; beta-coefficient: -58.9; 95%CI: -84.7 to -33.1; p < 0.001). CONCLUSION: CAC density is significantly impacted by regional CAC distribution and image reconstruction, potentially confounding its prognostic value. Accounting for these factors may improve patient risk assessment, management, and cardiovascular health outcomes.

Early Intraluminal Frozen Elephant Trunk Stent Graft Thrombosis After Aortic Arch Surgery.

BACKGROUND: Partial intraluminal thrombosis of the frozen elephant trunk (FET) stent graft is a poorly described but not infrequent complication after aortic arch surgery. This study aims to describe and analyze the occurrence of early FET stent graft thrombosis. METHODS: Retrospective single-center analysis including patients who underwent aortic arch replacement with FET technique between 2006 and 2020. Stent graft thrombosis was diagnosed through computed tomography scan. Several computed tomography scan parameters and clinical variables were analyzed as predictors of this event. RESULTS: A total of 125 patients were included for analysis. Among these, 21 (16.8%) patients developed early postoperative FET stent graft thrombosis. Mean volumetric size of the aorta was 12.2 ± 2.0 mL in patients with FET stent graft thrombosis and 10.1 ± 2.8 mL in patients without thrombosis (P < .01). Thrombosis occurred more frequently among patients requiring thoracic endovascular aortic repair completion (15 of 21 [71.4%] patients) than in patients with completely excluded aneurysms (6 of 21 [28.6%] patients) (P = .01). Mean stent-to-aneurysm diameter ratio was 0.8 ± 0.2 among patients with thrombosis and 1.0 ± 0.2 among patients without thrombosis (P < .01). Thrombosis was more frequently observed among patients with conservative management of postoperative bleeding (P = .04). Patients with early FET thrombosis had a nonsignificantly higher in-hospital all-cause mortality than patients without thrombosis (19.0% vs 8.7%; P = .3). CONCLUSIONS: Early postoperative intraluminal thrombosis is a frequent complication post FET surgery. Smaller stent graft sizes, larger or partially covered aneurysms, and major bleeding are associated with early thrombosis. Slight FET oversizing, prompt thoracic endovascular aortic repair completion, and early reintervention for major bleeding may prevent early thrombosis.

Comparison of aortic blood flow rotational direction in healthy volunteers and patients with bicuspid aortic valves using volumetric velocity-sensitive cardiovascular magnetic resonance imaging.

Background: The rotational direction (RD) of helical blood flow can be classified as either a clockwise (RD+) or counter-clockwise (RD-) flow. We hypothesized that this simple classification might not be sufficient for analysis in vivo and a simultaneous existence of RD+/- may occur. We utilized volumetric velocity-sensitive cardiovascular magnetic resonance imaging (4D flow MRI) to analyze rotational blood flow in the thoracic aorta. Methods: Forty volunteers (22 females; mean age, 41±16 years) and seventeen patients with bicuspid aortic valves (BAVs) (9 females; mean age, 42±14 years) were prospectively included. The RDs and the calculation of the rotating blood volumes (RBVs) in the thoracic aorta were performed using a pathline-projection strategy. Results: We could confirm a mainly clockwise RD in the ascending, descending aorta and in the aortic arch. Furthermore, we found a simultaneous existence of RD+/RD-. The RD+/--volume in the ascending aorta was significantly higher in BAV patients, the mean RD+/RD- percentage was approximately 80%/20% vs. 60%/40% in volunteers (P<0.01). The maximum RBV always occurred during systole. There was significantly more clockwise than counter-clockwise rotational flow in the ascending aorta (P<0.01) and the aortic arch (P<0.01), but no significant differences in the descending aorta (P=0.48). Conclusions: A simultaneous occurrence of RD+/RD- indicates that a simple categorization in either of both is insufficient to describe blood flow in vivo. Rotational flow in the ascending aorta and in the aortic arch differs significantly from flow in the descending aorta. BAV patients show significantly more clockwise rotating volume in the ascending aorta compared to healthy volunteers.

Interrater variability of ML-based CT-FFR during TAVR-planning: influence of image quality and coronary artery calcifications.

Objective: To compare machine learning (ML)-based CT-derived fractional flow reserve (CT-FFR) in patients before transcatheter aortic valve replacement (TAVR) by observers with differing training and to assess influencing factors. Background: Coronary computed tomography angiography (cCTA) can effectively exclude CAD, e.g. prior to TAVR, but remains limited by its specificity. CT-FFR may mitigate this limitation also in patients prior to TAVR. While a high reliability of CT-FFR is presumed, little is known about the reproducibility of ML-based CT-FFR. Methods: Consecutive patients with obstructive CAD on cCTA were evaluated with ML-based CT-FFR by two observers. Categorization into hemodynamically significant CAD was compared against invasive coronary angiography. The influence of image quality and coronary artery calcium score (CAC) was examined. Results: CT-FFR was successfully performed on 214/272 examinations by both observers. The median difference of CT-FFR between both observers was -0.05(-0.12-0.02) (p < 0.001). Differences showed an inverse correlation to the absolute CT-FFR values. Categorization into CAD was different in 37/214 examinations, resulting in net recategorization of Δ13 (13/214) examinations and a difference in accuracy of Δ6.1%. On patient level, correlation of absolute and categorized values was substantial (0.567 and 0.570, p < 0.001). Categorization into CAD showed no correlation to image quality or CAC (p > 0.13). Conclusion: Differences between CT-FFR values increased in values below the cut-off, having little clinical impact. Categorization into CAD differed in several patients, but ultimately only had a moderate influence on diagnostic accuracy. This was independent of image quality or CAC.

[Computed tomography and magnetic resonance imaging in cardiac diagnostics-how to choose the right modality : A guide based on the new guidelines of the European Society of Cardiology (ESC)]. / Computer- und Magnetresonanztomographie in der Herzdiagnostik ­ welche Modalität ist die richtige? : Eine Orientierungshilfe auf Basis der neuen Leitlinien der European Society of Cardiology (ESC).

In the guideline updates of the European Society of Cardiology (ESC), noninvasive radiological cross-sectional imaging is taking an increasingly prominent role, while at the same time invasive diagnostic approaches are becoming less important. Especially for the diagnosis and treatment of chronic and acute coronary syndromes, there are fundamental changes in clinical routine. In addition, cross-sectional imaging also offers an alternative to diagnostic algorithms for other cardiac pathologies, especially echocardiography, which is increasingly used in the differential diagnosis of cardiac diseases. The radiologist should be aware of the recommendations of the current guidelines and encourage their establishment in clinical practice. This paper summarizes the indications of cross-sectional cardiac imaging with focus on new recommendations in the ESC guidelines and addresses specific strengths and weaknesses of each modality.

CT Planning prior to Transcatheter Mitral Valve Replacement (TMVR). / CT-Planung vor kathetergestütztem Mitralklappenersatz (TMVR).

BACKGROUND: Transcatheter mitral valve replacement (TMVR) is a treatment option for patients with therapy refractory high-grade mitral valve regurgitation and a high perioperative risk.During TMVR, the mitral annulus cannot be visualized directly. Therefore, comprehensive pre-interventional planning and a precise visualization of the patient's specific mitral valve anatomy, outflow tract anatomy and projected anchoring of the device are necessary.Aim of this review-article is, to assess the role of pre-procedural computed tomography (CT) for TMVR-planning METHODS: Screening and evaluation of relevant guidelines (European Society of Cardiology [ESC], American Heart Association [AHA/ACC]), meta-analyses and original research using the search terms "TVMR" or "TMVI" and "CT". In addition to this, the authors included insight from their own clinical experience. RESULTS: CT allows for accurate measurement of the mitral annulus with high special and adequate temporal resolution in all cardiac phases. Therefore, CT represents a valuable method for accurate prosthesis-sizing.In addition to that, CT can provide information about the valvular- and outflow-tract-anatomy, mitral valve calcifications, configuration of the papillary muscles and of the left ventricle. Additionally, the interventional access-route may concomitantly be visualized. CONCLUSION: CT plays, in addition to echocardiographic imaging, a central role in pre-interventional assessment prior to TMVR. Especially the precise depiction of the left ventricular outflow tract (LVOT) provides relevant additional information, which is very difficult or not possible to be acquired in their entirety with other imaging modalities. KEY POINTS: · CT plays a central role in pre-interventional imaging for TMVR.. · CT-measurements allow for accurate prosthesis-sizing.. · CT provides valuable information about LVOT-anatomy, mitral calcifications and interventional access-route.. CITATION FORMAT: · Heiser L, Gohmann RF, Noack T et al. CT Planning prior to Transcatheter Mitral Valve Replacement (TMVR). Fortschr Röntgenstr 2022; 194: 373 - 383.

Risk Assessment of Coronary Obstruction During Transcatheter Aortic Valve Replacement: Insights From Post-BASILICA Computed Tomography.

OBJECTIVES: The aim of this study was to examine the predictive value of preprocedural computed tomography (CT)-based risk stratification of coronary obstruction during transcatheter aortic valve replacement (TAVR) on the basis of geometric measurements on postprocedural CT. BACKGROUND: Proper patient selection for additional procedures to prevent coronary obstruction during TAVR has not been adequately evaluated. METHODS: Pre- and postprocedural computed tomographic scans of 28 patients treated using bioprosthetic or native aortic scallop intentional laceration to prevent iatrogenic coronary artery obstruction (BASILICA) and TAVR were analyzed. Using the postprocedural computed tomographic images, threatened coronary obstruction (TCO) was defined as: 1) ostial obstruction (adherence of the transcatheter heart valve [THV] to the coronary ostium with leaflet extension above the ostium); and/or 2) sinus sequestration (THV adherence to the sinotubular junction [STJ] with leaflet extension above the STJ) and was substratified into complete and incomplete types. RESULTS: A total of 51 leaflets were evaluated (88% surgical tissue valves) after excluding leaflets not visible on CT (n = 5). On postprocedural CT, complete TCO was observed in 25.4% (13 of 51 leaflets). On preprocedural CT, leaflets were at high risk for complete TCO (incidence 53%) if the virtual THV-to-coronary distance (VTC) was <3.0 mm, or if the virtual THV-to-STJ distance (VTSTJ) was <1.0 mm with STJ height - leaflet length <0 mm (leaflet-STJ mismatch). Leaflets were at low risk (incidence 0%) if the VTC was ≥3 mm and VTSTJ was ≥3.0 mm or STJ height - leaflet length was ≥+2.0 mm. Of 28 leaflets treated using BASILICA, complete TCO was seen in 35.7% (n = 10), due to sinus sequestration (100%) with coexisting ostial obstruction (30%). Actual coronary events occurred in 7.1% (n = 2) because of leaflet prolapse, corresponding to an absolute risk reduction by BASILICA of 29% (P = 0.021). CONCLUSIONS: Risk assessment of coronary obstruction after TAVR may improve with a multiparametric approach incorporating VTC, VTSTJ, and leaflet-STJ mismatch. BASILICA appeared to reduce actual coronary events even in leaflets with anticipated coronary obstruction.

Combined cCTA and TAVR Planning for Ruling Out Significant CAD: Added Value of ML-Based CT-FFR.

OBJECTIVES: The purpose of this study was to analyze the ability of machine-learning (ML)-based computed tomography (CT)-derived fractional flow reserve (CT-FFR) to further improve the diagnostic performance of coronary CT angiography (cCTA) for ruling out significant coronary artery disease (CAD) during pre-transcatheter aortic valve replacement (TAVR) evaluation in patients with a high pre-test probability for CAD. BACKGROUND: CAD is a frequent comorbidity in patients undergoing TAVR. Current guidelines recommend its assessment before TAVR. If significant CAD can be excluded on cCTA, invasive coronary angiography (ICA) may be avoided. Although cCTA is a very sensitive test, it is limited by relatively low specificity and positive predictive value, particularly in high-risk patients. METHODS: Overall, 460 patients (age 79.6 ± 7.4 years) undergoing pre-TAVR CT were included and examined with an electrocardiogram-gated CT scan of the heart and high-pitch scan of the vascular access route. Images were evaluated for significant CAD. Patients routinely underwent ICA (388/460), which was omitted at the discretion of the local Heart Team if CAD could be effectively ruled out on cCTA (72/460). CT examinations in which CAD could not be ruled out (CAD+) (n = 272) underwent additional ML-based CT-FFR. RESULTS: ML-based CT-FFR was successfully performed in 79.4% (216/272) of all CAD+ patients and correctly reclassified 17 patients as CAD negative. CT-FFR was not feasible in 20.6% because of reduced image quality (37/56) or anatomic variants (19/56). Sensitivity, specificity, positive predictive value, and negative predictive value were 94.9%, 52.0%, 52.2%, and 94.9%, respectively. The additional evaluation with ML-based CT-FFR increased accuracy by Δ+3.4% (CAD+: Δ+6.0%) and raised the total number of examinations negative for CAD to 43.9% (202/460). CONCLUSIONS: ML-based CT-FFR may further improve the diagnostic performance of cCTA by correctly reclassifying a considerable proportion of patients with morphological signs of obstructive CAD on cCTA during pre-TAVR evaluation. Thereby, CT-FFR has the potential to further reduce the need for ICA in this challenging elderly group of patients before TAVR.

Segmentation and characterization of visceral and abdominal subcutaneous adipose tissue on CT with and without contrast medium: influence of 2D- and 3D-segmentation.

BACKGROUND: Adipose tissue is a valuable biomarker. Although validation and correlation to clinical data have mostly been performed on non-enhanced scans (NES), a previous study has shown conversion of values of contrast enhanced scan (CES) into those of NES to be feasible with segmentation of the entire abdomen (3D-segmentation). In this study we analyzed if density and area of abdominal adipose tissue segmented in a single slice (2D-segmentation) of CES may be converted into that of NES. Furthermore, we compared the precision of conversion between 2D- and 3D-segmentation. METHODS: Thirty-one multi-phasic abdominal CT examinations at identical scan settings were retrospectively included. Exams included NES (n=31), arterial (ART) (n=23), portal-venous (PVN) (n=10), and/or venous scan (VEN) (n=31). Density and area of visceral (VAT) and subcutaneous adipose tissue (SAT) were quantified semi-automatically with fixed thresholds. For conversion of values from CES into those of NES regression analyses were performed and tested. 2D- and 3D-segmentation were compared with respect to conversion accuracy (normalized deviations of converted NES values from original measurements). RESULTS: After the application of contrast medium 2D-segmented adipose tissue increased in density (max. +5.6±2.4 HU) and decreased in area (max. -10.91%) (10.47%), with few exceptions (P<0.05). This was more pronounced in later scans (VEN ≈ PVN > ART) and more marked in VAT than SAT. Density and area in CES correlated very well with NES, allowing for conversion with only small error. While converted density is slightly more precise applying 3D-segmentation, conversion error of quantity was occasionally smaller with 2D-segmentation. CONCLUSIONS: Contrast medium changes density and quantity of segmented adipose tissue in differing degrees between compartments, contrast phases and 2D- and 3D-segmentation. However, changes are fairly constant for a given compartment, contrast phase and mode of segmentation. Therefore, conversion of values into those of NES may be achieved with comparable precision for 2D- and 3D-segmentation.

3D-segmentation and characterization of visceral and abdominal subcutaneous adipose tissue on CT: influence of contrast medium and contrast phase.

BACKGROUND: Adipose tissue as part of body composition analysis may serve as a powerful biomarker. Validation of segmented adipose tissue and correlation to clinical data has been performed on non-enhanced scans (NES). As many patients require a contrast enhanced scan (CES) for other aspects of clinical decision making, the utility of CES for body composition analysis would be most useful. Therefore, we analyzed the influence of iodinated contrast medium (ICM) and contrast phase on the characterization and segmentation of adipose tissue. METHODS: Exams of 31 patients undergoing multi-phasic CT at identical scan settings containing an NES were retrospectively included. In addition to NES, patients received an arterial (ART) (n=23), portal-venous (PVN) (n=10), and/or venous scan (VEN) (n=31) after intravenous injection of 90 mL ICM. Density and volume of adipose tissue were quantified semi-automatically with thresholds between -190 HU and -30 HU and recorded separately for visceral (VAT) and subcutaneous adipose tissue (SAT). Density and volume of total adipose tissue (TAT) were computed. For conversion of values from CES into those of NES regression analyses were performed and tested. RESULTS: Density of adipose tissue increased after application of ICM more on later scans (VEN ≈ PVN > ART) and more markedly in VAT than SAT (VAT > TAT > SAT). Except in SAT on ART, all changes were significant (P<0.001). Measured volume of adipose tissue decreased on all CES (VEN ≈ PVN > ART) (P<0.001), but only reached statistical significance for VAT and TAT (VAT > TAT) on all CES (P<0.05). Density and volume in CES correlate extremely well with NES and may be calculated from one another [root-mean-square error (RMSE): <6 HU; <0.85 dm3]. CONCLUSIONS: Density and volume of segmented adipose tissue are altered by the injection of ICM in differing degrees between compartments and contrast phases. However, as the effect of ICM is fairly constant for a given compartment and contrast phase, values may be converted into those of NES with relative precession. This conversion allows body composition analysis to be carried out also in contrast enhanced CT examinations, e.g., for risk stratification and the comparison of the obtained results to previous studies.

Combined Coronary CT-Angiography and TAVI-Planning: A Contrast-Neutral Routine Approach for Ruling-out Significant Coronary Artery Disease.

BACKGROUND: Significant coronary artery disease (CAD) is a common finding in patients undergoing transcatheter aortic valve implantation (TAVI). Assessment of CAD prior to TAVI is recommended by current guidelines and is mainly performed via invasive coronary angiography (ICA). In this study we analyzed the ability of coronary CT-angiography (cCTA) to rule out significant CAD (stenosis ≥ 50%) during routine pre-TAVI evaluation in patients with high pre-test probability for CAD. METHODS: In total, 460 consecutive patients undergoing pre-TAVI CT (mean age 79.6 ± 7.4 years) were included. All patients were examined with a retrospectively ECG-gated CT-scan of the heart, followed by a high-pitch-scan of the vascular access route utilizing a single intravenous bolus of 70 ml iodinated contrast medium. Images were evaluated for image quality, calcifications, and significant CAD; CT-examinations in which CAD could not be ruled out were defined as positive (CAD+). Routinely, patients received ICA (388/460; 84.3%; Group A), which was omitted if renal function was impaired and CAD was ruled out on cCTA (Group B). Following TAVI, clinical events were documented during the hospital stay. RESULTS: cCTA was negative for CAD in 40.2% (188/460). Sensitivity, specificity, PPV, and NPV in Group A were 97.8%, 45.2%, 49.6%, and 97.4%, respectively. Median coronary artery calcium score (CAC) was higher in CAD+-patients but did not have predictive value for correct classification of patients with cCTA. There were no significant differences in clinical events between Group A and B. CONCLUSION: cCTA can be incorporated into pre-TAVI CT-evaluation with no need for additional contrast medium. cCTA may exclude significant CAD in a relatively high percentage of these high-risk patients. Thereby, cCTA may have the potential to reduce the need for ICA and total amount of contrast medium applied, possibly making pre-procedural evaluation for TAVI safer and faster.

Leadless Cardiac Pacemaker (LCP) without Diagnostic Relevant Artifacts in DualSource and DualEnergy-CT Examinations in First- to Third-Generation DSCT Scanner.

RATIONALE AND OBJECTIVES: To identify the influence and artifact burden in cardiac CT imaging of a leadless cardiac pacemaker (LCP) performed with all three generations of DualSource CT (DSCT) Scanners. MATERIALS AND METHODS: The LCP was examined in DSCT scanners of the first to third generation using DualEnergy (DECT) and DSCT as well as alterations of the current-time product. For DECT examinations, virtual monoenergetic images were computed manually on a dedicated workstation. Virtual voltage was manually selected by subjective assessment of the lowest artifact burden. Systematic variations of the pacemaker angle to the gantry were assessed, too. The angle was successively increased by 10°, ranging from 0° to 90°. Artifact burden was quantified on a five-point Likert scale (1- no artifacts, 2- few artifacts, 3- moderate artifacts, 4- many artifacts, and 5- massive artifacts). Likert values of 1-3 were considered diagnostic and assessed by two board-certified radiologists in consensus. RESULTS: In total, 200 examinations were analyzed, a mean Likert value of 1.93 ± 0.61 was found overall. None of the images were assessed Likert value >3. The positioning evaluation showed a clear and significant reduction of artifact burden toward lower angles, (0°: 1.4 ± 0.5 vs. 90° 2.55 ± 0.51). At scanner level, second-generation DSCT performed significantly better (1.68 ± 0.47) than both other scanners. Comparison of technique (DECT vs. DSCT) revealed a significantly improved image quality in DSCT examinations. CONCLUSION: LCP can be safely examined in DSCT scanner of the first to third generation with the evaluated protocols and techniques, which are currently in use. Artifact burden can be significantly reduced by aligning or approaching the LCP's longitudinal axis toward the scanner's z-axis.