Impact of dual energy cardiac CT for metal artefact reduction post aortic valve replacement.

PURPOSE: Assess image quality of dual-energy (DE) and single-energy (SE) cardiac multi-detector computed tomographic (MDCT) post aortic valve replacement (AVR) on a dual source MDCT scanner. METHODS: Eighty patients with cardiac MDCT acquisitions (ECG gated, dual-source) post-surgical and transcatheter AVR were retrospectively identified. Forty DE (cohort 1) and 40 SE acquisitions (cohort 2; 100 or 120 kVp) were reviewed. Metal artefact at valve coaptation (VC) and valve insertion site (VIS), and contrast enhancement were assessed. Valve leaflet edge definition was graded on a 4-point scale by three radiologists. RESULTS: The mean percentage valve area obscured by metal artifact differed between the cohorts; cohort 1 DE blended, high keV and low keV: 14.8 %, 11.1 % and 17.8 % at VC and 16.4 %, 13 %, 20.4 % at VIS respectively. Cohort 2: 25.8 % and 33.6 % (VC and VIS); each DE reconstruction vs SE: P < 0.0001. Average contrast opacification and coefficient of variance for cohort 1: 562.9 ± 144.7, 281.1 ± 60.3 and 1132.7 ± 300.8 Hounsfield Units (HU) and 9.6 %, 10 % and 8.9 %. For cohort 2: 437.2 ± 119.2 HU and 10.8 % (P < 0.01). Average leaflet edge definition cohort 1: 2.3 ± 0.4, 2.7 ± 0.2 and 2.3 ± 0.2, and cohort 2: 2.9 ± 0.2. CONCLUSION: DE high keV renderings can result in up to 17.2 % less metal artefact compared to standard SE acquisition for cardiac CT. Contrast opacification and homogeneity is higher for DE blended and low keV renderings compared to SE acquisition with leaflet visibility preferred for low keV and blended DE renderings.

Evaluation of Intraindividual Contrast Enhancement Variability for Determining the Maximum Achievable Consistency in CT.

OBJECTIVE. The purpose of this study was to quantify temporal variability in vascular and parenchymal enhancement within the same patient and to determine technique-related factors contributing to this variability. MATERIALS AND METHODS. We identified 100 patients who underwent four CT scans within 12 months with identical acquisition and contrast injection parameters. Enhancement was recorded in the abdominal aorta, main portal vein, liver parenchyma, and subcutaneous fat. Patient demographic and body habitus data were recorded. Injection-related factors were recorded including delay time from contrast injection to image acquisition. All pairwise differences in enhancement within each patient were evaluated for absolute and percentage change. RESULTS. Based on predetermined thresholds, we observed clinically relevant variability in 34% of patients for the abdominal aorta, 38% for the portal vein, and 33% for the liver parenchyma. A highly significant association was observed between higher variability in delay time and variability in the abdominal aorta (p = 0.009) and between female sex and variability in liver parenchyma (p = 0.008). A marginally significant association was seen between increasing age (p = 0.025) and female sex (p = 0.039) with variability in the abdominal aorta. No statistically significant association was found between all recorded variables and variability in the portal vein. CONCLUSION. Approximately one-third of patients may show clinically relevant variability in enhancement of the abdominal aorta, portal vein, and liver parenchyma even when using identical scanning and injection parameters. Delay time was the only controllable factor associated with variability in enhancement of the abdominal aorta; no other controllable factor is associated with variability in the portal vein or liver parenchyma.

ACR Appropriateness Criteria® Chronic Chest Pain-Noncardiac Etiology Unlikely-Low to Intermediate Probability of Coronary Artery Disease.

Chronic chest pain (CCP) of a cardiac etiology is a common clinical problem. The diagnosis and classification of the case of chest pain has rapidly evolved providing the clinician with multiple cardiac imaging strategies. Though scintigraphy and rest echocardiography remain as appropriate imaging tools in the diagnostic evaluation, new technology is available. Current evidence supports the use of alternative imaging tests such as coronary computed tomography angiography (CCTA), cardiac MRI (CMRI), or Rb-82 PET/CT. Since multiple imaging modalities are available to the clinician, the most appropriate noninvasive imaging strategy will be based upon the patient's clinical presentation and clinical status. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

ACR Appropriateness Criteria® Suspected New-Onset and Known Nonacute Heart Failure.

While there is no single diagnostic test for heart failure (HF), imaging plays a supportive role beginning with confirmation of HF, especially by detecting ventricular dysfunction (Variant 1). Ejection fraction (EF) is important in HF classification, and imaging plays a subsequent role in differentiation between HF with reduced EF (HFrEF) versus preserved EF (HFpEF) (Variant 2). Once HFrEF is identified, distinction between ischemic and nonischemic etiologies with imaging support (Variant 3) facilitates further planning. Imaging approaches which are usually appropriate include: both resting transthoracic echocardiography (TTE) and chest radiography for Variant 1; resting TTE and/or MRI (including functional, without absolute need for contrast) for Variant 2; and for Variant 3, a. Coronary CTA or coronary arteriography (if high pretest probability/symptoms for ischemic disease) for coronary assessment; b. Rest/vasodilator stress SPECT/CT, PET/CT, or MRI for myocardial perfusion assessment; c. Rest/exercise or inotropic stress TTE for myocardial contraction assessment; or d. MRI (including morphologic with contrast) for myocardial characterization. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

ACR Appropriateness Criteria® Imaging for Transcatheter Aortic Valve Replacement.

Aortic stenosis is a common valvular condition with increasing prevalence in aging populations. When severe and symptomatic, the downstream prognosis is poor without surgical or transcatheter aortic valve replacement. Transcatheter aortic valve replacement is now considered a viable alternative to surgical aortic valve replacement in patients considered high and intermediate risk for surgery. Pre-intervention imaging with echocardiography and CT are essential for procedure planning and device selection to help optimize clinical outcomes with MR angiography playing largely a complementary role. Modern 3-D cross-sectional imaging has consistently shown to help reduce procedural complications from vascular access injury to paravalvular regurgitation and coronary obstruction. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Whole-Body High-Pitch CT Angiography: Strategies to Reduce Radiation Dose and Contrast Volume.

OBJECTIVE: The purpose of this study was to assess the noninferiority of dual-source high-pitch CT angiography (CTA) performed with high-concentration (iopamidol 370) low-volume (60 mL) iodinated contrast material at low voltage (100 kVp) in comparison with dual-source high-pitch CTA with standard-of-care low-concentration (iopamidol 300) standard-volume (75 mL) iodinated contrast material at high voltage (120 kVp) to determine whether use of the high-concentration low-volume method would afford a reduction in radiation dose and contrast volume without negatively affecting vascular opacification. SUBJECTS AND METHODS: This study had three arms. A phantom was used to assess vascular contrast enhancement at different iodine and saline solution dilutions with iopamidol 300 or 370 to compare lower-iodination (iopamidol 300) high-voltage (120 kVp) high-pitch (120 kVp, 250 mAs) imaging with higher-iodination (iopamidol 370) low-voltage (100 kVp) high-pitch (100 kVp, 100-240 mAs) acquisition. Metal-oxide-semiconductor field-effect transistors were placed in an anthropomorphic phantom to extract organ-based radiation profiles, and ANOVA was performed. The study prospectively enrolled 150 patients: 50 patients received 75 mL iopamidol 300, and image acquisition was performed at 120 kVp and 250 mAs; 50 patients received 75 mL iopamidol 370, and acquisition was performed at 100 kVp and 240 mAs; and 50 patients received 60 mL iopamidol, and acquisition was performed at 370 at 100 kVp and 240 mAs. Vascular signal-to-noise ratio was evaluated at 18 anatomic locations. Longitudinal signal-to-noise ratio was used to assess homogeneity of contrast enhancement. Size-specific dose estimates were calculated. Statistical analyses were performed by ANOVA. RESULTS: Noninferiority of high-concentration (iopamidol 370) low-voltage (100 kVp) high-pitch acquisitions compared with low-concentration (iopamidol 300) high-voltage (120 kVp) high-pitch acquisition was achieved at 170 mAs in vitro. Radiation assessment showed significant decreases in radiation dose for the 100-kVp 240-mAs protocol (p < 0.0001). Noninferior vascular contrast (p > 0.280) and luminal homogeneity (p > 0.191) were found for all high-pitch protocols. Significantly decreased radiation dose was observed for the two groups that received 60 and 75 mL of iopamidol 370 at 100 kVp and 240 mAs (p < 0.0001). CONCLUSION: Dual-source high-pitch CTA with high-concentration (iopamidol 370) low-volume (60 mL) iodinated contrast medium and low-voltage acquisition (100 kVp) is noninferior to dual-source high-pitch CTA with low-concentration (iopamidol 300) standard-volume (75 mL) iodinated contrast material at high voltage (120 kVp) and affords simultaneous reduction in radiation dose and contrast volume without negatively affecting vascular contrast enhancement.

Non-dysbaric arterial gas embolism associated with chronic necrotizing pneumonia, bullae and coughing: a case report.

Arterial gas embolism (AGE) can be clinically devastating, and is most often associated with exposure to changes in ambient pressure, medical procedure or congenital malformation. Here we report a case of AGE in a 78-year-old male without these traditional risk factors. Rather, the patient's history included chronic obstructive pulmonary disease, necrotizing pneumonia, bullous disease and coughing. He was safely treated with hyperbaric oxygen (HBO2) therapy for AGE, with initial clinical improvement, but ultimately died from his underlying condition. Pathophysiology is discussed. This case illustrates the possibility that AGE can occur due to rupture of lung tissue in the absence of traditional risk factors. HBO2 therapy should be considered in the management of such patients.

MR Venography of the Central Veins of the Thorax.

While imaging of the central venous system has traditionally been performed with conventional venography, MR venography (MRV) has emerged as an important modality as techniques and validation studies have evolved over time. While magnetic resonance angiography has a very robust representation in the literature, the proportion representing MRV is relatively sparse. The purpose of this article is to review the indications, techniques, and dedicated studies validating MRV of the central veins of the thorax.

MRI of the Central Lymphatic System: Indications, Imaging Technique, and Pre-Procedural Planning.

Magnetic resonance imaging is increasingly being used to evaluate the lymphatic system. Advances in magnetic resonance (MR) software and hardware allow improved visualization of lymph nodes and lymphatic vessels. We describe how MR lymphangiography can be used to diagnose central lymphatic system anatomy and pathology, which can be used for diagnostic purposes or for pre-procedural planning.

ACR Appropriateness Criteria® Dyspnea-Suspected Cardiac Origin.

This article discusses imaging guidelines for five dyspnea variants: (1) dyspnea due to heart failure, ischemia not excluded; (2) dyspnea due to suspected nonischemic heart failure, ischemia excluded; (3) dyspnea due to suspected valvular heart disease, ischemia excluded; (4) dyspnea due to suspected cardiac arrhythmia, ischemia excluded; and (5) dyspnea due to suspected pericardial disease, ischemia excluded. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Use of Preprocedural MDCT for Cardiac Implantable Electric Device Lead Extraction: Frequency of Findings That Change Management.

OBJECTIVE: Five percent of cardiac implantable electric devices (CIEDs) are removed each year. Percutaneous extraction is preferred but can be complicated if the leads adhere to the vasculature or perforate. The goal of this study is to assess the frequency of findings on dedicated MDCT that alter preprocedural planning for percutaneous CIED extraction. MATERIALS AND METHODS: One hundred patients with CIEDs who underwent MDCT before percutaneous lead extraction were analyzed. Major findings that could preclude percutaneous removal, including lead course and termination, were distinguished from moderately significant findings that could alter but not preclude percutaneous removal, including endofibrosis of leads to the vasculature, lead termination abnormalities, central vein stenosis, or thrombus. Incidental findings were characterized separately. Findings were correlated with preprocedural decisions, the extraction procedure performed, and procedural outcomes. RESULTS: Twenty-six women and 74 men with 125 right ventricular leads, 84 right atrial leads, and 26 coronary venous leads were evaluated. Major findings were present in 7% of patients, including six patients with lead perforation and one with a lead coursing outside a tricuspid annuloplasty ring. Moderately significant findings of endothelial fibrosis were found in 78% of patients. The central veins were narrowed or occluded in 42% of patients, and thrombus was present in 2% of patients. Thirty-six percent of patients had incidental findings, and 4% of patients had unexpected findings requiring immediate inpatient attention. CONCLUSION: MDCT performed before CIED lead extraction is able to identify major and moderately significant findings that can alter either percutaneous extraction or preprocedural planning. The use of dedicated preprocedural MDCT can help to stratify patient risk, guide decision making by the proceduralist, and identify non-catheter-related findings that affect patient management.

Resolution of severe hemolysis and paravalvular aortic regurgitation employing an Amplatzer Vascular Plug 4: the importance of detailed pre-procedural planning using CT angiography.

A 76-year-old woman presented with progressive heart failure and transfusion-dependent hemolytic anemia due to severe paravalvular aortic regurgitation 4 years after bioprosthetic aortic valve replacement. She was deemed not to be a candidate for redo cardiac surgery due to a porcelain aorta and multiple comorbid medical conditions. We describe the role of pre-procedure contrast-enhanced, ECG-gated computed tomographic angiography to characterize the anatomy of the paravalvular leak connection for appropriate occluder device selection leading to successful percutaneous closure and resolution of the paravalvular regurgitation and hemolytic anemia.

Imaging Surveillance After Proximal Aortic Operations: Is it Necessary?

BACKGROUND: Current guidelines for imaging surveillance after proximal aortic repair are not evidence based. This study sought to characterize the incidence and causes of reintervention after proximal aortic operations to provide data to guide the frequency and duration of postoperative surveillance. METHODS: Data on all patients undergoing proximal aortic operations (ascending, with or without root, with or without aortic valve replacement, or with or without arch) during a 9-year period (n = 869) at a single institution were prospectively collected. Patients who required reintervention on the proximal or distal aorta were identified and causes for reintervention determined. Planned two-stage repairs and index procedures done at other hospitals were excluded. The primary end point was the time to the first reintervention, and competing-risk Cox regression was used to model reintervention risk. RESULTS: Reinterventions occurred in 4.3% of patients (n = 37), with 48.6% (n = 18) involving the proximal aorta and 51.4% (n = 19) the distal. Median time to reintervention was 2.8 years (interquartile range, 1.5 to 3.6 years). For index aneurysm cases, reintervention for aneurysm of the descending/thoracoabdominal aorta and root were most common. Of the 6 root aneurysms/pseudoaneurysms, 5 (83%) were due to degeneration of a stentless porcine aortic root. For index type A dissections, reintervention for aneurysm of the descending/thoracoabdominal aorta and arch were most common. The mean duration of follow up was 4.2 ± 2.5 years. The 9-year actuarial freedom from reintervention was 92.9%. Cox regression showed index type A dissection was a significant predictor of time to aortic reintervention (hazard ratio, 2.01; 95% confidence interval, 1.04 to 3.9; p = 0.038). CONCLUSIONS: Reinterventions after proximal aortic operations are uncommon; most occur within 3 years of the index operation and involve the proximal and distal aorta nearly equally. Patients with type A dissection or stentless porcine roots require aggressive surveillance, whereas a more liberal approach is suitable for patients without such risk factors. This strategy may reduce the lifetime radiation burden and health care costs.

Dual-Source Single-Energy Multidetector CT Used to Obtain Multiple Radiation Exposure Levels within the Same Patient: Phantom Development and Clinical Validation.

Purpose To develop, in a phantom environment, a method to obtain multidetector computed tomographic (CT) data sets at multiple radiation exposure levels within the same patient and to validate its use for potential dose reduction by using different image reconstruction algorithms for the detection of liver metastases. Materials and Methods The American College of Radiology CT accreditation phantom was scanned by using a dual-source multidetector CT platform. By adjusting the radiation output of each tube, data sets at six radiation exposure levels (100%, 75%, 50%, 37.5%, 25%, and 12.5%) were reconstructed from two consecutive dual-source single-energy (DSSE) acquisitions, as well as a conventional single-source acquisition. A prospective, HIPAA-compliant, institutional review board-approved study was performed by using the same DSSE strategy in 19 patients who underwent multidetector CT of the liver for metastatic colorectal cancer. All images were reconstructed by using conventional weighted filtered back projection (FBP) and sinogram-affirmed iterative reconstruction with strength level of 3 (SAFIRE-3). Objective image quality metrics were compared in the phantom experiment by using multiple linear regression analysis. Generalized linear mixed-effects models were used to analyze image quality metrics and diagnostic performance for lesion detection by readers. Results The phantom experiment showed comparable image quality between DSSE and conventional single-source acquisition. In the patient study, the mean size-specific dose estimates for the six radiation exposure levels were 13.0, 9.8, 5.8, 4.4, 3.2, and 1.4 mGy. For each radiation exposure level, readers' perception of image quality and lesion conspicuity was consistently ranked superior with SAFIRE-3 when compared with FBP (P ≤ .05 for all comparisons). Reduction of up to 62.5% in radiation exposure by using SAFIRE-3 yielded similar reader rankings of image quality and lesion conspicuity when compared with routine-dose FBP. Conclusion A method was developed and validated to synthesize multidetector CT data sets at multiple radiation exposure levels within the same patient. This technique may provide a foundation for future clinical trials aimed at estimating potential radiation dose reduction by using iterative reconstructions. © RSNA, 2016 Online supplemental material is available for this article.

Regional Mapping of Aortic Wall Stress by Using Deformable, Motion-coherent Modeling based on Electrocardiography-gated Multidetector CT Angiography: Feasibility Study.

Purpose To investigate the feasibility of deformable, motion-coherent modeling based on electrocardiography-gated multidetector computed tomographic (CT) angiography of the thoracic aorta and to evaluate whether quantifiable information on aortic wall stress as a function of patient-specific cardiovascular parameters can be gained. Materials and Methods For this institutional review board-approved, HIPAA-compliant study, thoracic electrocardiography-gated dual-source multidetector CT angiographic images were used from 250 prospectively enrolled patients (150 men, 100 women; mean age, 79 years). On reconstructed 50-phase CT angiographic images, aortic strain and deformation were determined at seven cardiac and aortic locations. One-way analysis of variance was used by assessing the magnitude for longitudinal and axial strain and axial deformation, as well as time-resolved peak and maxima count for longitudinal strain and axial deformation. Interdependencies between aortic strain and deformation with extracted hemodynamic parameters were evaluated. Results With increasing heart rates, there was a significant decrease in longitudinal strain (P = .009, R(2) = 0.95) and a decrease in the number of longitudinal strain peaks (P < .001, R(2) = 0.79); however, a significant increase in axial deformation (P < .001, R(2) = 0.31) and axial strain (P = .009, R(2) = 0.61) was observed. Increasing aortic blood velocity led to increased longitudinal strain (P = .018, R(2) = 0.42) and longitudinal strain peak counts (P = .011, R(2) = 0.48). Pronounced motion in the longitudinal direction limited motion in the axial plane (P < .019, R(2) = 0.29-0.31). Conclusion The results of this study render a clinical basis and provide proof of principle for the use of deformable, motion-coherent modeling to provide quantitative information on physiological motion of the aorta under various hemodynamic circumstances. (©) RSNA, 2016 Online supplemental material is available for this article.

Application of a Novel CT-Based Iliac Artery Calcification Scoring System for Predicting Renal Transplant Outcomes.

OBJECTIVE: The objective of our study was to assess whether the degree and distribution of iliac artery calcifications as determined by a CT-based calcium scoring system correlates with outcomes after renal transplant. MATERIALS AND METHODS: A retrospective review of renal transplant recipients who underwent CT of the pelvis within 2 years before surgery yielded 131 patients: 75 men and 56 women with a mean age of 52 years. Three radiologists assigned a separate semiquantitative score for calcification length, circumferential involvement, and morphology for the common iliac arteries and for the external iliac arteries. The operative and clinical notes were reviewed to determine which iliac arterial segment was used for anastomosis, the complexity of the operation, and whether delayed graft function (DGF) occurred. Renal allograft survival and patient survival were calculated using the Kaplan-Meier technique. RESULTS: Excellent interobserver agreement was noted for each calcification score category. The common iliac arteries showed significantly higher average calcification scores than the external iliac arteries for all categories. Advanced age and diabetes mellitus were independently predictive of higher scores in each category, whereas hypertension, cigarette smoking, hyperlipidemia, and sex were not. Based on multivariate analysis, only the calcification morphology score of the arterial segment used for anastomosis was independently predictive of a higher rate of surgical complexity and of DGF. None of the scores was predictive of graft or patient survival. However, patients with CT evidence of iliac arterial calcification had a lower 1-year survival after transplant than those who did not (92% vs 98%, respectively; p = 0.05). CONCLUSION: Only the calcification morphology score of the arterial segment used for anastomosis was significantly predictive of surgical complexity and of DGF. Routine pretransplant CT for calcification scoring in patients of advanced age or those with diabetes mellitus may enable selection of the optimal artery for anastomosis to optimize outcomes.

High-Pitch Dual-Source MDCT for Imaging of the Thoracoabdominal Aorta: Relationships Among Radiation Dose, Noise, Pitch, and Body Size in a Phantom Experiment and Clinical Study.

OBJECTIVE: The purpose of this study was to investigate, both in a phantom experiment and a within-patient clinical study the relationships among radiation dose, image noise, pitch, and body size in MDCT angiography of the thoracoabdominal aorta, with the use of high-pitch dual-source and standard-pitch single-source acquisitions. MATERIALS AND METHODS: A proprietary tapered phantom consisting of four ultrahigh-molecular-weight polyethylene cylinders was used to mimic the body size ranges (small, medium, large, and extra large) of patients in the United States. The phantom was imaged using both standard-pitch (0.8) and various high-pitch (range, 2.0-3.2 [in increments of 0.4]) settings. Standard-pitch and high-pitch acquisitions were also performed in 45 patients (27 men, 18 women; mean age, 67.6 years). RESULTS: At standard pitch, the volume CT dose index (CTDIvol) increased with phantom size, in a logistic sigmoid relationship. At high-pitch settings, the CTDIvol increased gradually in relation to phantom size, up to a threshold (denoted by tCTDI[pitch] ≈ 48.3-7.5 pitch), which linearly decreased (R(2) = 0.99) with pitch (maximum CTDIvol output at pitch [maxCTDI(pitch)] ≈ 18.9-3.9 pitch). A linear decrease in the size-specific dose estimate (SSDE) was observed beyond phantom size thresholds (tSSDE[pitch] ≈ 47.6-8.6 pitch) linearly decreasing (R(2) = 0.98) with pitch (maximum SSDE output at pitch [maxSSDE(pitch)] ≈ 15.5-1.3 pitch). Image noise was statistically significantly lower at standard pitch than at high-pitch settings (p = 0.01). In patients, statistically significant differences were noted between standard and high-pitch settings in the mean CTDIvol(10.8 ± 2.6 and 8.3 ± 0.7 mGy, respectively), SSDE (11.3 ± 2.1 and 8.8 ± 1.5 mGy, respectively), and noise (9.7 ± 2.2 and 14 ± 4.2, respectively) (p < .0001, for all comparisons). CONCLUSION: Lower radiation dose levels achieved with the use of a high-pitch technique reflect limitations in tube output occurring for medium to large body sizes, with an associated exponential increase in noise. The standard- and high-pitch techniques yield similar radiation dose levels for small body sizes.

Comparison of aortic annulus size by transesophageal echocardiography and computed tomography angiography with direct surgical measurement.

This study sought to compare the accuracy of 2-dimensional transesophageal echocardiography (TEE) and computed tomography angiography (CTA) for noninvasive aortic annular sizing as required for transcatheter aortic valve implantation (TAVI). Direct intraoperative (OR) sizing is the gold standard for aortic annular measurement in surgical aortic valve replacement. Unlike surgical aortic valve replacement, TAVI requires noninvasive assessment of aortic annular dimensions for determining the size of prosthesis to be implanted and controversy exists regarding the best imaging technique for TAVI sizing. Preoperative CTA and OR TEE images of the aortic annulus in 227 patients who underwent proximal aortic surgery with OR annular sizing at the Duke University Medical Center were reviewed. Both imaging techniques were compared with direct OR measurements of aortic annulus diameter using metric sizers as the gold standard. CTA overestimated aortic annulus diameter in 72.2% of cases, with 46.3% >1 TAVI valve-size (>3 mm) overestimations, whereas TEE underestimated aortic annulus diameter in 51.1% of cases, with 16.7% >1 valve-size underestimations. Combining both techniques improved the estimation of aortic annular size. In conclusion, there are limitations to current imaging techniques for noninvasive determination of aortic annular dimensions compared with direct OR sizing. Undersizing by TEE and oversizing by CTA are common and may be related to differences in methods for sizing an elliptical structure. Combining measurements from both techniques would decrease the false exclusion rate for TAVI eligibility because of size mismatch.

Assessment of single-bolus contrast administration technique using hybrid dual-source ECG-gated thoracic and dual-source non-ECG-gated high-pitch abdominopelvic CT acquisitions for procedural planning before transcatheter aortic valve replacement.

PURPOSE: This study aimed to assess vascular contrast opacification and homogeneity using single-bolus contrast administration with hybrid thoracic and abdominopelvic computed tomographic angiography in patients with severe aortic valve stenosis. MATERIALS AND METHODS: Combination electrocardiogram-gated thoracic and dual-source, high-pitch abdominopelvic computed tomographic angiography examinations of 50 patients with severe aortic stenosis between December 2013 and March 2014 were reviewed. Contrast administration was individualized to patient-specific physiology. Image analysis of vascular opacification was obtained and interdependencies of vascular contrast and homogeneity of contrast distribution were assessed. RESULTS: The mean volume of contrast administered was 106 ± 11.7 mL. Mean attenuation was 371 ± 90.7 Hounsfield units (HU) in the thoracic aorta and 388 ± 95.9 HU in the abdominal aorta. Homogeneous opacification was obtained throughout with coefficient of variation of 11%. CONCLUSIONS: Procedural planning for transcatheter aortic valve replacement can be achieved using a single-injection bolus contrast protocol in combination with a 2-part multidetector computed tomographic image acquisition technique with optimal opacification of major arterial structures.