Inter-observer variability of expert-derived morphologic risk predictors in aortic dissection.

OBJECTIVES: Establishing the reproducibility of expert-derived measurements on CTA exams of aortic dissection is clinically important and paramount for ground-truth determination for machine learning. METHODS: Four independent observers retrospectively evaluated CTA exams of 72 patients with uncomplicated Stanford type B aortic dissection and assessed the reproducibility of a recently proposed combination of four morphologic risk predictors (maximum aortic diameter, false lumen circumferential angle, false lumen outflow, and intercostal arteries). For the first inter-observer variability assessment, 47 CTA scans from one aortic center were evaluated by expert-observer 1 in an unconstrained clinical assessment without a standardized workflow and compared to a composite of three expert-observers (observers 2-4) using a standardized workflow. A second inter-observer variability assessment on 30 out of the 47 CTA scans compared observers 3 and 4 with a constrained, standardized workflow. A third inter-observer variability assessment was done after specialized training and tested between observers 3 and 4 in an external population of 25 CTA scans. Inter-observer agreement was assessed with intraclass correlation coefficients (ICCs) and Bland-Altman plots. RESULTS: Pre-training ICCs of the four morphologic features ranged from 0.04 (-0.05 to 0.13) to 0.68 (0.49-0.81) between observer 1 and observers 2-4 and from 0.50 (0.32-0.69) to 0.89 (0.78-0.95) between observers 3 and 4. ICCs improved after training ranging from 0.69 (0.52-0.87) to 0.97 (0.94-0.99), and Bland-Altman analysis showed decreased bias and limits of agreement. CONCLUSIONS: Manual morphologic feature measurements on CTA images can be optimized resulting in improved inter-observer reliability. This is essential for robust ground-truth determination for machine learning models. KEY POINTS: • Clinical fashion manual measurements of aortic CTA imaging features showed poor inter-observer reproducibility. • A standardized workflow with standardized training resulted in substantial improvements with excellent inter-observer reproducibility. • Robust ground truth labels obtained manually with excellent inter-observer reproducibility are key to develop reliable machine learning models.

Effectiveness of late gadolinium enhancement to improve outcomes prediction in patients referred for cardiovascular magnetic resonance after echocardiography.

BACKGROUND: Echocardiography (echo) is a first line test to assess cardiac structure and function. It is not known if cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE) ordered during routine clinical practice in selected patients can add additional prognostic information after routine echo. We assessed whether CMR improves outcomes prediction after contemporaneous echo, which may have implications for efforts to optimize processes of care, assess effectiveness, and allocate limited health care resources. METHODS AND RESULTS: We prospectively enrolled 1044 consecutive patients referred for CMR. There were 38 deaths and 3 cardiac transplants over a median follow-up of 1.0 years (IQR 0.4-1.5). We first reproduced previous survival curve strata (presence of LGE and ejection fraction (EF) < 50%) for transplant free survival, to support generalizability of any findings. Then, in a subset (n = 444) with contemporaneous echo (median 3 days apart, IQR 1-9), EF by echo (assessed visually) or CMR were modestly correlated (R(2) = 0.66, p < 0.001), and 30 deaths and 3 transplants occurred over a median follow-up of 0.83 years (IQR 0.29-1.40). CMR EF predicted mortality better than echo EF in univariable Cox models (Integrated Discrimination Improvement (IDI) 0.018, 95% CI 0.008-0.034; Net Reclassification Improvement (NRI) 0.51, 95% CI 0.11-0.85). Finally, LGE further improved prediction beyond EF as determined by hazard ratios, NRI, and IDI in all Cox models predicting mortality or transplant free survival, adjusting for age, gender, wall motion, and EF. CONCLUSIONS: Among those referred for CMR after echocardiography, CMR with LGE further improves risk stratification of individuals at risk for death or death/cardiac transplant.

Registry of Aortic Diseases to Model Adverse Events and Progression (ROADMAP) in Uncomplicated Type B Aortic Dissection: Study Design and Rationale.

Purpose: To describe the design and methodological approach of a multicenter, retrospective study to externally validate a clinical and imaging-based model for predicting the risk of late adverse events in patients with initially uncomplicated type B aortic dissection (uTBAD). Materials and Methods: The Registry of Aortic Diseases to Model Adverse Events and Progression (ROADMAP) is a collaboration between 10 academic aortic centers in North America and Europe. Two centers have previously developed and internally validated a recently developed risk prediction model. Clinical and imaging data from eight ROADMAP centers will be used for external validation. Patients with uTBAD who survived the initial hospitalization between January 1, 2001, and December 31, 2013, with follow-up until 2020, will be retrospectively identified. Clinical and imaging data from the index hospitalization and all follow-up encounters will be collected at each center and transferred to the coordinating center for analysis. Baseline and follow-up CT scans will be evaluated by cardiovascular imaging experts using a standardized technique. Results: The primary end point is the occurrence of late adverse events, defined as aneurysm formation (≥6 cm), rapid expansion of the aorta (≥1 cm/y), fatal or nonfatal aortic rupture, new refractory pain, uncontrollable hypertension, and organ or limb malperfusion. The previously derived multivariable model will be externally validated by using Cox proportional hazards regression modeling. Conclusion: This study will show whether a recent clinical and imaging-based risk prediction model for patients with uTBAD can be generalized to a larger population, which is an important step toward individualized risk stratification and therapy.Keywords: CT Angiography, Vascular, Aorta, Dissection, Outcomes Analysis, Aortic Dissection, MRI, TEVAR© RSNA, 2022See also the commentary by Rajiah in this issue.

Compare display schemes for lung nodule CT screening.

This study investigated the relative efficiencies of a stereographic display and two monoscopic display schemes for detecting lung nodules in chest computed tomography (CT). The ultimate goal was to determine whether stereoscopic display provides advantages for visualization and interpretation of three-dimensional (3D) medical image datasets. A retrospective study that compared lung nodule detection performances achieved using three different schemes for displaying 3D CT data was conducted. The display modes included slice-by-slice, orthogonal maximum intensity projection (MIP), and stereoscopic display. One hundred lung-cancer screening CT examinations containing 647 nodules were interpreted by eight radiologists, in each of the display modes. Reading times and displayed slab thickness versus time were recorded, as well as the probability, location, and size for each detected nodule. Nodule detection performance was analyzed using the receiver operating characteristic method. The stereo display mode provided higher detection performance with a shorter interpretation time, as compared to the other display modes tested in the study, although the difference was not statistically significant. The analysis also showed that there was no difference in the patterns of displayed slab thickness versus time between the stereo and MIP display modes. Most radiologists preferred reading the 3D data at a slab thickness that corresponded to five CT slices. Our results indicate that stereo display has the potential to improve radiologists' performance for detecting lung nodules in CT datasets. The experience gained in conducting the study also strongly suggests that further benefits can be achieved through providing readers with additional functionality.

Characterization of radiologists' search strategies for lung nodule detection: slice-based versus volumetric displays.

The goal of this study was to assess whether radiologists' search paths for lung nodule detection in chest computed tomography (CT) between different rendering and display schemes have reliable properties that can be exploited as an indicator of ergonomic efficiency for the purpose of comparing different display paradigms. Eight radiologists retrospectively viewed 30 lung cancer screening CT exams, containing a total of 91 nodules, in each of three display modes [i.e., slice-by-slice, orthogonal maximum intensity projection (MIP) and stereoscopic] for the purpose of detecting and classifying lung nodules. Radiologists' search patterns in the axial direction were recorded and analyzed along with the location, size, and shape for each detected feature, and the likelihood that the feature is an actual nodule. Nodule detection performance was analyzed by employing free-response receiver operating characteristic methods. Search paths were clearly different between slice-by-slice displays and volumetric displays but, aside from training and novelty effects, not between MIP and stereographic displays. Novelty and training effects were associated with the stereographic display mode, as evidenced by differences between the beginning and end of the study. The stereo display provided higher detection and classification performance with less interpretation time compared to other display modes tested in the study; however, the differences were not statistically significant. Our preliminary results indicate a potential role for the use of radiologists' search paths in evaluating the relative ergonomic efficiencies of different display paradigms, but systematic training and practice is necessary to eliminate training curve and novelty effects before search strategies can be meaningfully compared.

Computed Tomography Aortic Valve Calcium Scoring in Patients With Aortic Stenosis.

BACKGROUND: Computed tomography aortic valve calcium scoring (CT-AVC) holds promise for the assessment of patients with aortic stenosis (AS). We sought to establish the clinical utility of CT-AVC in an international multicenter cohort of patients. METHODS AND RESULTS: Patients with AS who underwent ECG-gated CT-AVC within 3 months of echocardiography were entered into an international, multicenter, observational registry. Optimal CT-AVC thresholds for diagnosing severe AS were determined in patients with concordant echocardiographic assessments, before being used to arbitrate disease severity in those with discordant measurements. In patients with long-term follow-up, we assessed whether CT-AVC thresholds predicted aortic valve replacement and death. In 918 patients from 8 centers (age, 77±10 years; 60% men; peak velocity, 3.88±0.90 m/s), 708 (77%) patients had concordant echocardiographic assessments, in whom CT-AVC provided excellent discrimination for severe AS (C statistic: women 0.92, men 0.89). Our optimal sex-specific CT-AVC thresholds (women 1377 Agatston unit and men 2062 Agatston unit) were nearly identical to those previously reported (women 1274 Agatston unit and men 2065 Agatston unit). Clinical outcomes were available in 215 patients (follow-up 1029 [126-2251] days). Sex-specific CT-AVC thresholds independently predicted aortic valve replacement and death (hazard ratio, 3.90 [95% confidence interval, 2.19-6.78]; P<0.001) after adjustment for age, sex, peak velocity, and aortic valve area. Among 210 (23%) patients with discordant echocardiographic assessments, there was considerable heterogeneity in CT-AVC scores, which again were an independent predictor of clinical outcomes (hazard ratio, 3.67 [95% confidence interval, 1.39-9.73]; P=0.010). CONCLUSIONS: Sex-specific CT-AVC thresholds accurately identify severe AS and provide powerful prognostic information. These findings support their integration into routine clinical practice. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifiers: NCT01358513, NCT02132026, NCT00338676, NCT00647088, NCT01679431.

On the accuracy of CartoMerge for guiding posterior left atrial ablation in man.

BACKGROUND: Recent reports suggest that the CartoMerge system is useful for guiding human posterior left atrial (PLA) endocardial ablation. OBJECTIVE: To assess the accuracy of the CartoMerge system during PLA ablation. METHODS: Sixteen patients undergoing PLA catheter ablation were studied. In each patient, registration of preoperative computed tomographic (CT) and intraoperative electroanatomic left atrial images was performed to create CartoMerge images. Encircling of right and left pulmonary venous vestibules with ablation points was then performed guided solely by intracardiac echocardiography, with point locations saved on a CartoMerge image to which the operator was blinded. The accuracy of the CartoMerge image was then assessed by measuring the distance from the location of each ablation point on the image to its actual anatomic location. In five patients, accuracy of registration of each of three left atrial CT images (just prior to mitral valve opening, at end-diastasis, at end-atrial contraction) with the electroanatomic image was compared. In two patients, accuracy of registration using left atrial image data alone was compared with that which used both left atrial and thoracic aorta image data. RESULTS: In each patient, inaccuracy of the CartoMerge image was apparent, the magnitude of which was similar for right- and left-vestibule ablation points. Accuracy was significantly improved when the end-atrial contraction CT image was used for registration. The inclusion of thoracic aorta image data did not improve accuracy. CONCLUSIONS: The CartoMerge system is inaccurate. Inaccuracy may be reduced by using CT and electroanatomic images obtained at the same point in the atrial mechanical cycle.

Dynamic multidimensional imaging of the human left atrial appendage.

AIMS: The human left atrial appendage (LAA) is a region of increasing interest as a target for intervention. We sought to improve insight into the anatomy of this region using computed tomography (CT). METHODS AND RESULTS: Multidimensional cardiac reconstruction (whole heart and isolated left atrium) from CT images was performed in each of three groups: (i) patients without atrial fibrillation (AF, n =10); (ii) patients with intermittent (paroxysmal) AF (n = 25); (iii) patients with continuous (persistent) AF (n = 10). Indices included LAA morphology, anatomical relationships, dimensions, angulation, and motility. There was substantial interindividual variation in each index. LAA morphologic differences were associated with variations in anatomical relationships. LAA dimensions in AF patients exceeded those in patients without AF, but angulation and motility were similar. The LAA could be subdivided into proximal and distal portions, each of which had distinct morphology and anatomical relationships. Dimensions in men tended to exceed those in women. CONCLUSION: Regardless of AF history, there is broad variation in LAA morphology, anatomical relationships, dimensions, angulation, and motility. These observations may have importance for the development of technologies for therapy delivery in this region.

CT of the pulmonary veins.

Atrial fibrillation (AF) is a common cardiac rhythm disturbance and its incidence is increasing. Radiofrequency catheter ablation (RFCA) is a highly successful therapy for treating AF, and its use is becoming more widespread; however, with its increasing use and evolving technique, known complications are better understood and new complications are emerging. Computed tomography (CT) of the pulmonary veins, or more correctly, the posterior left atrium (LA), has an established role in precisely defining the complex anatomy of the LA and pulmonary veins preablation and has an expanding role in identifying the myriad of possible complications postablation. The purposes of this article are: to review AF and RFCA; to discuss CT evaluation of the LA and pulmonary veins preablation; and to review the complications of RFCA focusing on the role of CT postablation.

Direct comparison of computed tomography and magnetic resonance imaging for characterization of posterior left atrial morphology.

OBJECTIVE: Accumulating evidence points to the central importance of the posterior left atrium (PLA) for atrial fibrillation (AF). Catheter ablation intended to cure AF is increasingly practiced; performance and assessment of this procedure is enhanced by accurate imaging of PLA anatomy. Prior reports have suggested that both computed tomographic (CT) and magnetic resonance (MR) imaging techniques provide accurate PLA images. These techniques have never been compared directly. MATERIALS AND METHODS: Twenty patients referred for catheter ablation underwent preoperative imaging using both CT and MR. Each technique was used to create a multidimensional image of the PLA. RESULTS: Within patients, morphologic and dimensional PLA indices, including number of individual pulmonary venoatrial junctions, presence of ostial branches, circumference of each venoatrial junction, venoatrial junction "non-circularity", and distance between ipsilateral superior and inferior venoatrial junctions, were well correlated. CONCLUSIONS: CT and MR-based images of the PLA appear comparable. Technique selection should involve considerations of toxicity, tolerance, and local resources.

Aggressive Aortic Arch and Carotid Replacement Strategy for Type A Aortic Dissection Improves Neurologic Outcomes.

BACKGROUND: International registries for acute type A aortic dissection (TAAD) demonstrate stagnant operative mortality rates in excess of 20% and stroke rates of 9% to 25%, with little global emphasis on stroke reduction or carotid involvement. Cerebral malperfusion with TAAD has been linked to poorer outcome. We hypothesize that concomitant carotid dissection or complex dissection flaps in the arch play a major role in stroke development and that aggressive reconstruction of the arch and carotid arteries can improve neurologic outcomes in TAAD. METHODS: A standardized protocol focused on expedient care, neurocerebral protection, and common carotid and total arch reconstruction was developed for 264 consecutive TAADs. Arch and complete carotid replacement was based on arch dissection anatomy, carotid involvement, or an intraarch tear. Neurocerebral monitoring with continuous electroencephalogram/somatosensory evoked potentials was used in all cases. RESULTS: The postoperative stroke and hospital mortality rates were 3.4% and 9.1%, and stroke rates by extent of arch replacement were 4%, 3%, and 0% for hemiarch, total arch, and total arch with complete carotid replacement, respectively. An intraoperative change in the electroencephalogram/somatosensory evoked potentials was strongly predictive of stroke and had a negative predictive value of 98.2%. CONCLUSIONS: An algorithmic approach to TAAD including (1) rapid transport-to-incision-to-cardiopulmonary bypass established centrally, (2) neurocerebral monitoring, (3) liberal use of total arch replacement for clearly defined indications (and hemiarch for all others), and (4) common carotid arterial replacement for concomitant carotid dissections significantly improves outcomes.

Revised curriculum on cardiothoracic radiology for diagnostic radiology residency with goals and objectives related to general competencies.

This document is a revision of a previously published cardiothoracic curriculum for diagnostic radiology residency, and reflects interval changes in the clinical practice of cardiothoracic radiology and changes in the Accreditation Council for Graduate Medical Education (ACGME) requirements for diagnostic radiology training programs. The revised ACGME Program Requirements for Residency Education in Diagnostic Radiology went into effect December 2003.

3D-multidetector CT angiography in the evaluation of potential donors for living donor lung transplantation.

INTRODUCTION: In living donor lung transplant, donor lobectomies from 2 donors provide right and left lower lobes for transplantation. In the past, routine evaluation of pulmonary anatomy was not performed preoperatively. Intraoperatively, surgeons were often forced to sacrifice the lingular artery or right middle lobe segmental artery to obtain an adequate arterial cuff for safe reimplantation. This study was performed to evaluate the utility of preoperative 3D-multidetector CT angiography (3D-MDCTA) as a noninvasive method of assessing pulmonary arteries to improve donor selection and surgical planning for living lung donors. SUBJECTS AND METHODS: Five potential lung donors for 2 recipients were included in the study. CT scanning with 4 channel multidetector-row CT was performed, using a modified pulmonary embolism protocol. Post-processing was performed using volume rendering techniques on a commercially available workstation. RESULTS: 3D-MDCT demonstrated that there are a number of variations in pulmonary arterial anatomy and that ideal anatomy was seldom encountered. Comparison of different donors determined which lower lobes were most favorable for transplantation. Surgery confirmed the accuracy of 3D-MDCTA. There were no pulmonary arterial complications, and no vessels were sacrificed. CONCLUSION: Safely explanting lower lobes from living donors for lung transplantation poses challenges not encountered in harvesting cadaveric donors or performing lobectomies for malignancy. 3D-MDCTA of pulmonary arteries can noninvasively delineate the often-complex pulmonary anatomy, which may assist in donor selection as well as reduce donor intraoperative and postoperative vascular complications.

Diagnosis of pulmonary embolism by acute right heart morphologic and hemodynamic changes observed during exercise stress echocardiography.

In addition to the conventional means of diagnosing pulmonary embolism, resting echocardiography has sometimes been useful. We describe the case of a patient with a normal resting transthoracic echocardiogram, but with a markedly abnormal posttreadmill exercise echocardiogram revealing acute right ventricular dilatation, marked ventricular septal shift, and acute pulmonary hypertension. Pulmonary embolism was suspected and subsequently confirmed by chest computed tomographic angiography.

Multi-detector row CT of the left atrium and pulmonary veins before radio-frequency catheter ablation for atrial fibrillation.

Radio-frequency catheter ablation (RFCA) of the distal pulmonary veins and posterior left atrium is increasingly being used to treat recurrent or refractory atrial fibrillation that resists pharmacologic therapy or cardioversion. Successful RFCA of atrial fibrillation requires resolution of abnormal rhythms while minimizing complications and can be achieved with precise, preprocedural, three-dimensional (3D) anatomic delineation of the target, the atriopulmonary venous junction. Three-dimensional multi-detector row computed tomography (CT) of the pulmonary veins and left atrium provides the necessary anatomic information for successful RFCA, including (a) the number, location, and angulation of pulmonary veins and their ostial branches unobscured by adjacent cardiac and vascular anatomy, and (b) left atrial volume. The 3D multi-detector row CT scanning and postprocessing techniques used for pre-RFCA planning are straightforward. Radiologists must not only understand these techniques but must also be familiar with atrial fibrillation and the technical considerations and complications associated with RFCA of this condition. In addition, radiologists must be familiar with anatomic variants of the left atrium and distal pulmonary veins and understand the importance of these variants to the referring cardiac interventional electrophysiologist.

The role of aortic wall CT attenuation measurements for the diagnosis of acute aortic syndromes.

OBJECTIVES: To determine if measurements of aortic wall attenuation can improve the CT diagnosis of acute aortic syndromes. METHODS: CT reports from a ten year period were searched for acute aortic syndromes (AAS). Studies with both an unenhanced and a contrast enhanced (CTA) series that had resulted in the diagnosis of intramural hematoma (IMH) were reviewed. Diagnoses were confirmed by medical records. The attenuation of aortic wall abnormalities was measured. The observed attenuation threshold was validated using studies from 39 new subjects with a variety of aortic conditions. RESULTS: The term "aortic dissection" was identified in 1206, and IMH in 124 patients' reports. IMH was confirmed in 31 patients, 21 of whom had both unenhanced and contrast enhanced images. All 21 had pathologic CTA findings, and no CTA with IMH was normal. Attenuation of the aortic wall was greater than 45 HUs on the CTA images in all patients with IMH. When this threshold was applied to the new group, sensitivity for diagnosing AAS was 100% (19/19), and specificity 94% (16/17). Addition of unenhanced images did not improve accuracy. CONCLUSIONS: Measurements of aortic wall attenuation in CTA have a high negative predictive value for the diagnosis of acute aortic syndromes.

Free-breathing, motion-corrected late gadolinium enhancement is robust and extends risk stratification to vulnerable patients.

BACKGROUND: Routine clinical use of novel free-breathing, motion-corrected, averaged late-gadolinium-enhancement (moco-LGE) cardiovascular MR may have advantages over conventional breath-held LGE (bh-LGE), especially in vulnerable patients. METHODS AND RESULTS: In 390 consecutive patients, we collected bh-LGE and moco-LGE with identical image matrix parameters. In 41 patients, bh-LGE was abandoned because of image quality issues, including 10 with myocardial infarction. When both were acquired, myocardial infarction detection was similar (McNemar test, P=0.4) with high agreement (κ=0.95). With artifact-free bh-LGE images, pixelwise myocardial infarction measures correlated highly (R(2)=0.96) without bias. Moco-LGE was faster, and image quality and diagnostic confidence were higher on blinded review (P<0.001 for all). During a median of 1.2 years, 20 heart failure hospitalizations and 18 deaths occurred. For bh-LGE, but not moco-LGE, inferior image quality and bh-LGE nonacquisition were linked to patient vulnerability confirmed by adverse outcomes (log-rank P<0.001). Moco-LGE significantly stratified risk in the full cohort (log-rank P<0.001), but bh-LGE did not (log-rank P=0.056) because a significant number of vulnerable patients did not receive bh-LGE (because of arrhythmia or inability to hold breath). CONCLUSIONS: Myocardial infarction detection and quantification are similar between moco-LGE and bh-LGE when bh-LGE can be acquired well, but bh-LGE quality deteriorates with patient vulnerability. Acquisition time, image quality, diagnostic confidence, and the number of successfully scanned patients are superior with moco-LGE, which extends LGE-based risk stratification to include patients with vulnerability confirmed by outcomes. Moco-LGE may be suitable for routine clinical use.

Prevalence of aortic root dilation in patients with CT angiography of the aorta.

PURPOSE: To investigate the prevalence of aortic root dilation in patients who underwent CT angiography of the thoracic aorta. MATERIALS AND METHODS: In 95 patients, 64-slice multislice computed tomography was performed for evaluation of the thoracic aorta. Measurements of the annulus, sinuses of valsalva (SOV), sinotubular junction (STJ), and maximum ascending aorta (AAo) were made by double oblique multiplanar reformation (MPR). For the AAo, STJ, and SOV, dilation was defined as greater than 40 mm; for annulus, the dilation criterion was greater than 27 mm. RESULTS: Overall, 52 patients were diagnosed with a dilated AAo. Of those patients with dilated AAo, 28 patients had a dilated annulus, 27 patients had dilated SOV, and 11 patients had STJ dilation. Forty-three patients presented with normal AAo; 12 patients had annulus dilation; 12 patients had SOV dilation; and 4 patients had STJ dilation. In patients with dilated AAo, 38% also had a dilated annulus, 52% showed SOV dilation, and 21% presented with STJ dilation, compared to 28% annulus dilation, 28% SOV dilation, and 9% STJ dilation in patients with an AAo of normal caliber. CONCLUSION: Our data indicate a higher prevalence of aortic root dilation among patients with dilated AAo.