A radiomics model based on aortic computed tomography angiography: the impact on predicting the prognosis of patients with aortic intramural hematoma (IMH).

Background: The prognosis of aortic intramural hematoma (IMH) is unpredictable, but computed tomography angiography (CTA) plays an important role of high diagnostic performance in the initial diagnosis and during follow-up of patients. In this study, we investigated the value of a radiomics model based on aortic CTA for predicting the prognosis of patients with medically treated IMH. Method: A total of 120 patients with IMH were enrolled in this study. The follow-up duration ranged from 32 to 1,346 days (median 232 days). Progression of these patients was classified as follows: destabilization, which refers to deterioration in the aortic condition, including significant increases in the thickness of the IMH, the progression of IMH to a penetrating aortic ulcer (PAU), aortic dissection (AD), or rupture; or stabilization, which refers to an unchanged appearance or a decrease in the size or disappearance of the IMH. The patients were divided into a training cohort (n=84) and a validation cohort (n=36). Six different machine learning classifiers were applied: random forest (RF), K-nearest neighbor (KNN), Gaussian Naive Bayes, decision tree, logistic regression, and support vector machine (SVM). The clinical-radiomics combined nomogram model was established by multivariate logistic regression. The area under the receiver operating characteristic (ROC) curve (AUC) was implemented to evaluate the discrimination performance of the models. The calibration curves and Hosmer-Lemeshow test were used for evaluating model calibration. DeLong's test was performed to compare the AUC performance of models. Results: Among all of the patients, 60 patients showed destabilization and 60 patients remained stable. A total of 12 radiomic features were retained after application of the least absolute shrinkage and selection operator (LASSO). These features were used for the machine learning model construction. The SVM-radial basis function (SVM-RBF) model obtained the best performance with an AUC of 0.765 (95% CI, 0.593-0.906). In the validation cohort, the combined clinical-radiomics model [AUC =0.787; 95% confidence interval (CI), 0.619-0.923] showed a significantly higher performance than did the clinical model (AUC =0.596; 95% CI, 0.413-0.796; P=0.021) and had a similar performance to the radiomics model (AUC =0.765; 95% CI, 0.589-0.906; P=0.672). Conclusions: A quantitative nomogram based on radiomic features of CTA images can be used to predict disease progression in patients with IMH and may help improve clinical decision-making.

Novel Multi-Parametric Mitral Annular Calcification Score Predicts Outcomes in Mitral Valve Dysfunction.

The objective of the study was to construct a multi-parametric mitral annular calcification (MAC) score using computed tomography (CT) features for prediction of outcomes in patients undergoing mitral valve surgery. We constructed a multi-parametric MAC score, which ranges between 2 and 12, and consists of Agatston calcium score (1 point: <1000 Agatston units (AU); 2 points: 1000-<3000 AU; 3 points: 3000-5000 AU; 4 points: >5000 AU), quantitative MAC circumferential angle (1 point: <90°; 2 points: 90-<180°; 3 points: 180-<270°; 4 points: 270-360°), involvement of trigones (1 point: 1 trigone; 2 points: both trigones), and 1 point each for myocardial infiltration and left ventricular outflow tract extension/involvement of aorto-mitral curtain. The association between MAC score and clinical outcomes was evaluated. The study cohort consisted of 334 patients undergoing mitral valve surgery (128 mitral valve repairs, 206 mitral valve replacements) between January 2011 and September 2019, who had both non-contrast gated CT scan and evidence of MAC. The mean age was 72 ± 11 years, with 58% of subjects being female. MAC score was a statistically significant predictor of total operation time (P<0.001), cross-clamp time (P = 0.001) and in-hospital complications (P = 0.003). Additionally, MAC score was a significant predictor of time to all-cause death (P = 0.046). A novel multi-parametric score based on CT features allowed systematic assessment of MAC, and predicted clinical outcomes in patients with mitral valve dysfunction undergoing mitral valve surgery.

Standardizing Methods of Reading CT Maximum Aortic Diameters Amongst Experts Reduces Variations and Discordance, Improving Accuracy.

BACKGROUND: There is no consensus on the method of obtaining abdominal aortic aneurysm (AAA) maximum diameters based on computed tomographic angiography, and the reproducibility and accuracy of different methods have recently been debated due to advancements in imaging. This study compared the two most common methods based on orthogonal planes and centerline of flow to determine the discordances and accuracy amongst experiences readers. METHODS: The computed tomographic angiography max diameters of 148 AAAs were measured by three experienced observers, including a vascular surgeon, a radiologist and an imaging cardiologist. Observers used two different methods with standardized protocols: multiplanar reformations based on orthogonal planes, and a software using 3D aortic reconstructions to create centerline flow lumen providing diameters based on cross sections perpendicular to this lumen. Agreements and reliability of measurement methods were assessed by intra-class correlation coefficient and Bland - Altman analysis. Discordances between measurements of the methods and the original reported measurement, as well as outside hospitals were compared. RESULTS: The average age of the cohort was 75 years and aortic diameters ranged from 3.8 to 9.6 cm. For orthogonal readings, there were agreements within 3 mm between 86% and 92% of the time, while centerline - reading agreement was between 88% and 94%, which was not statistically significant. The intra-class correlation coefficient was high between method type and between readers. Within methods, agreement was between 0.96 and 0.97, while within - reader agreement measures was between 0.96 and 0.98. In comparison to the original and the outside hospital reports, 10% ≥ of the original and 20% ≥ of the outside hospital reported measurements were discordant between the readers. CONCLUSION: Maximal AAA measurements can have substantial variability leading to clinical significance and change in patient management and outcomes. Based on the results, orthogonal and centerline measurement methods have equally high agreements and concordance within 3 mm and low variations at a high volume center. However, when compared to the official read reports, there is high discordance rates that can significantly alter patient outcomes. A standardized method of measurement maximum diameter can reduce variations and discordances among different methods.

Outcomes of contemporary imaging-guided management of sinus of Valsalva aneurysms.

BACKGROUND: Sinus of Valsalva aneurysms (SVAs) are rare. We assessed the role of multimodality imaging in guiding the contemporary management. METHODS: A single-center retrospective cohort study over a 20-year period was performed. RESULTS: Between January 1997 and June 2017, 103 patients were diagnosed with SVAs (median age: 58 years). Eighty patients presented with non-ruptured SVAs, and 23 with ruptured SVAs. Seventy-six patients underwent surgery, and 27 were conservatively managed. The median durations of follow-up were: 48 months (surgical group) vs. 37.5 months (conservative group). There was no mortality directly attributable to SVA surgery. There were no late complications in the conservative group. Transthoracic echocardiography (TTE) was the first-line imaging investigation (100.0% in surgical group vs. 92.6% in conservative group, P=0.019). Additional imaging studies included: (I) transesophageal echocardiography (TEE): 93.4% in surgical group vs. 22.2% in conservative group, P<0.001; (II) multi-detector cardiac computed tomography (MDCT): 61.8% in surgical group vs. 37.0% in conservative group, P=0.041; (III) cardiac magnetic resonance (CMR): 22.4% in surgical group vs. 14.8% in conservative group, P=0.579. At diagnosis, SVA diameters were: TTE: 4.80 cm (range, 3.30 cm); TEE: 5.40 cm (range, 4.00 cm); MDCT: 5.20 cm (range, 3.90 cm); CMR: 4.80 cm (range, 3.70 cm). CONCLUSIONS: In a 20-year cohort, proper selection for surgery and conservative management resulted in excellent outcomes for SVAs. TTE was the first-line imaging investigation for assessment of SVAs, although many patients underwent an additional imaging investigation. The contemporary outcomes of imaging-guided SVA management were excellent.

Tricuspid annular dimensions in patients with severe mitral regurgitation without severe tricuspid regurgitation.

BACKGROUND: Concomitant TV repair during mitral valve (MV) surgery based on tricuspid valve annulus (TVA) dilation, rather than the degree of tricuspid regurgitation (TR), is beneficial and supported by the valve guidelines. We sought to determine TVA geometry and dimensions in controls and assess the changes that occur in patients with severe primary (PMR) and secondary (SMR) mitral regurgitation without TR. METHODS: We analyzed cardiac computed tomographic angiography (CCTA) of 125 consecutive subjects: 50 controls with normal coronary CCTA and no valvular dysfunction, 50 PMR patients referred for robotic repair, and 25 SMR patients referred for transcatheter therapy. Patients with >2+ TR on echocardiography were excluded. Annular measurements were performed using dedicated software and compared. Correlations and determinants of TVA dimensions were analyzed. RESULTS: Patients with SMR were older and had significantly more comorbidities. In controls, the TVA was larger and more planar and eccentric compared to the MV annulus (all P<0.01). Dimensions of both annuli correlated significantly (r≥0.5; P<0.001 for all dimensions) in controls and patients with severe MR. In both PMR and SMR, the TVA enlarged in all dimensions (P<0.01) with a trend towards becoming more circular. On multivariable regression, the MV annular area was the primary determinant of the TVA area (adjusted ß=0.430, P<0.001). CONCLUSIONS: Substantial changes in TVA dimensions are encountered in patients with severe MR even in the absence of severe TR such that TVA and MVA dimensions remain correlated. Close attention to the TVA in patients with severe MR is warranted.

Analysis of cardiac motion without respiratory motion for cardiac stereotactic body radiation therapy.

PURPOSE/OBJECTIVE(S): To study the heart motion using cardiac gated computed tomographies (CGCT) to provide guidance on treatment planning margins during cardiac stereotactic body radiation therapy (SBRT). MATERIALS/METHODS: Ten patients were selected for this study, who received CGCT scans that were acquired with intravenous contrast under a voluntary breath-hold using a dual source CT scanner. For each patient, CGCT images were reconstructed in multiple phases (10%-90%) of the cardiac cycle and the left ventricle (LV), right ventricle (RV), ascending aorta (AAo), ostia of the right coronary artery (O-RCA), left coronary artery (O-LCA), and left anterior descending artery (LAD) were contoured at each phase. For these contours, the centroid displacements from their corresponding average positions were measured at each phase in the superior-inferior (SI), medial-lateral (ML), and anterior-posterior (AP). The average volumes as well as the maximum to minimum ratios were analyzed for the LV and RV. RESULTS: For the six contoured substructures, more than 90% of the measured displacements were <5 mm. For these patients, the average volumes ranged from 191.25 to 429.51 cc for LV and from 91.76 to 286.88 cc for RV. For each patient, the ratios of maximum to minimum volumes within a cardiac cycle ranged from 1.15 to 1.54 for LV and from 1.34 to 1.84 for RV. CONCLUSION: Based on this study, cardiac motion is variable depending on the specific substructure of the heart but is mostly within 5 mm. Depending on the location (central or peripheral) of the treatment target and treatment purposes, the treatment planning margins for targets and risk volumes should be adjusted accordingly. In the future, we will further assess heart motion and its dosimetric impact.

Subthreshold Aortic Valve Calcium Scores in Severe Aortic Stenosis and Transthyretin Cardiac Amyloidosis.

We have clinically observed that some patients with transthyretin cardiac amyloidosis and severe aortic stenosis may have lesser degrees of calcification than one might expect. We report a case series of 3 patients with transthyretin cardiac amyloidosis and severe aortic stenosis despite discordant aortic valve calcium scores. (Level of Difficulty: Intermediate.).

Lead Location as Assessed on Cardiac Computed Tomography and Difficulty of Percutaneous Transvenous Extraction.

OBJECTIVES: This study sought to retrospectively investigate outcomes of lead extraction by using pre-operative computed tomography (CT) scans to identify risk of complicated lead extraction to aid in pre-procedural planning. BACKGROUND: Transvenous lead extractions remain high-risk procedures requiring specialized operators, equipment, and surgical backup. Data are lacking for how to identify difficult lead extractions. CT scans, which can illustrate the proximity of the lead to adherent venous structures can potentially aid in identifying difficult lead extractions. METHODS: All cases of patients who were undergoing transvenous lead extractions at the authors' institution between 2015 and 2018, who had a pre-operative CT scan prior to lead extraction, were reviewed. The images were retrospectively reviewed to examine adherence of leads to the surrounding vein and obtained procedural outcomes. RESULTS: A total of 203 cases were reviewed of patients undergoing transvenous lead extraction who had a pre-operative CT scan, and scans were separated based on lead location in the superior vena cava, as assessed by CT imaging. Scans were divided into 3 groups: those in a central location or <1 cm adherence (n = 28); those that had at least 1 lead with tip adherent >1 cm (n = 137); or those that had at least 1 lead outside the vein contour (n = 38). Although there was only 1 serious complication requiring vascular surgery intervention, patients with at least 1 lead outside the vein contour required significantly longer procedural time (190.8 ± 86.6 min vs. 158.1 ± 73.7 min vs. 142.8 ± 52.2 min; p = 0.019) and fluoroscopy time (33.1 ± 24.2 min vs. 19.6 ± 18.4 min vs. 18.3 ± 16.4 min; p = 0.0006) than those with leads adhering >1 cm and centrally located leads, respectively. CONCLUSIONS: Pre-operative CT scanning can identify difficult lead extractions prior to performing the procedure. This information may aid electrophysiologists in the planning of extraction procedures. Future prospective studies are needed to confirm these findings.

ACC/AATS/AHA/ASE/ASNC/HRS/SCAI/SCCT/SCMR/STS 2019 Appropriate Use Criteria for Multimodality Imaging in the Assessment of Cardiac Structure and Function in Nonvalvular Heart Disease : A Report of the American College of Cardiology Appropriate Use Criteria Task Force, American Association for Thoracic Surgery, American Heart Association, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, and the Society of Thoracic Surgeons.

This document is the second of 2 companion appropriate use criteria (AUC) documents developed by the American College of Cardiology, American Association for Thoracic Surgery, American Heart Association, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, and Society of Thoracic Surgeons. The first document (J Am Coll Cardiol 2017;70:1647-1672) addresses the evaluation and use of multimodality imaging in the diagnosis and management of valvular heart disease, whereas this document addresses this topic with regard to structural (nonvalvular) heart disease. While dealing with different subjects, the 2 documents do share a common structure and feature some clinical overlap. The goal of the companion AUC documents is to provide a comprehensive resource for multimodality imaging in the context of structural and valvular heart disease, encompassing multiple imaging modalities.Using standardized methodology, the clinical scenarios (indications) were developed by a diverse writing group to represent patient presentations encountered in everyday practice and included common applications and anticipated uses. Where appropriate, the scenarios were developed on the basis of the most current American College of Cardiology/American Heart Association Clinical Practice Guidelines.A separate, independent rating panel scored the 102 clinical scenarios in this document on a scale of 1 to 9. Scores of 7 to 9 indicate that a modality is considered appropriate for the clinical scenario presented. Midrange scores of 4 to 6 indicate that a modality may be appropriate for the clinical scenario, and scores of 1 to 3 indicate that a modality is considered rarely appropriate for the clinical scenario.The primary objective of the AUC is to provide a framework for the assessment of these scenarios by practices that will improve and standardize physician decision making. AUC publications reflect an ongoing effort by the American College of Cardiology to critically and systematically create, review, and categorize clinical situations in which diagnostic tests and procedures are utilized by physicians caring for patients with cardiovascular diseases. The process is based on the current understanding of the technical capabilities of the imaging modalities examined.

ACC/AATS/AHA/ASE/ASNC/HRS/SCAI/SCCT/SCMR/STS 2019 Appropriate Use Criteria for Multimodality Imaging in the Assessment of Cardiac Structure and Function in Nonvalvular Heart Disease: A Report of the American College of Cardiology Appropriate Use Criteria Task Force, American Association for Thoracic Surgery, American Heart Association, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, and the Society of Thoracic Surgeons.

This document is the second of 2 companion appropriate use criteria (AUC) documents developed by the American College of Cardiology, American Association for Thoracic Surgery, American Heart Association, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, and Society of Thoracic Surgeons. The first document1 addresses the evaluation and use of multimodality imaging in the diagnosis and management of valvular heart disease, whereas this document addresses this topic with regard to structural (nonvalvular) heart disease. While dealing with different subjects, the 2 documents do share a common structure and feature some clinical overlap. The goal of the companion AUC documents is to provide a comprehensive resource for multimodality imaging in the context of structural and valvular heart disease, encompassing multiple imaging modalities. Using standardized methodology, the clinical scenarios (indications) were developed by a diverse writing group to represent patient presentations encountered in everyday practice and included common applications and anticipated uses. Where appropriate, the scenarios were developed on the basis of the most current American College of Cardiology/American Heart Association Clinical Practice Guidelines. A separate, independent rating panel scored the 102 clinical scenarios in this document on a scale of 1 to 9. Scores of 7 to 9 indicate that a modality is considered appropriate for the clinical scenario presented. Midrange scores of 4 to 6 indicate that a modality may be appropriate for the clinical scenario, and scores of 1 to 3 indicate that a modality is considered rarely appropriate for the clinical scenario. The primary objective of the AUC is to provide a framework for the assessment of these scenarios by practices that will improve and standardize physician decision making. AUC publications reflect an ongoing effort by the American College of Cardiology to critically and systematically create, review, and categorize clinical situations in which diagnostic tests and procedures are utilized by physicians caring for patients with cardiovascular diseases. The process is based on the current understanding of the technical capabilities of the imaging modalities examined.

Clinical Features, Natural History, and Management of Pericardial Cysts.

With the increased use of medical imaging, there has been an increase in the numbers of pericardial cysts identified. However, there is a paucity of data regarding the clinical course for pericardial cysts. Hence, we aimed to study the clinical features and natural history of pericardial cysts. We retrospectively studied all patients with the diagnosis of pericardial cysts based on computed tomography (CT) chest or cardiac magnetic resonance imaging (CMR) between 2008 and 2014. The maximum diameter of the cyst was measured at the initial study (CT/CMR) and was compared with the most recent follow-up imaging modality of the same type if available. A change in the maximum diameter more than 10% was considered significant. We included 103 patients in the study; 89% were asymptomatic and 67% were females. Twenty-nine asymptomatic patients had repeat imaging with the same modality (CT/CMR) with a mean follow-up of 23 months. The maximum cyst diameter decreased by a mean of 25% in 34% of the patients and increased by a mean of 13% in 17% of the patients. The remaining patients (48%) had no significant change. All 29 patients remained asymptomatic. In conclusion, most pericardial cyst cases were asymptomatic. On repeat imaging, approximately 1/3 of pericardial cysts were found to decrease in size, whereas interval enlargement was infrequent and unlikely to be clinically relevant. Therefore, within the limitations of our study, serial imaging in asymptomatic patients with CT or CMR does not appear to impact management decisions.

Surgical repair of a left main coronary artery aneurysm.

We report the repair of a 6.5 × 5.3-cm left main coronary artery aneurysm by marsupialization of the aneurysm sac and coronary artery bypass grafting.

Coronary artery calcium scoring: Its practicality and clinical utility in primary care.

Coronary artery calcium scoring is useful as a risk-stratification tool in coronary artery disease, and it outperforms other risk-assessment methods. American College of Cardiology/American Heart Association guidelines give the test a IIB recommendation in clinical scenarios in which risk stratification is uncertain. However, if the test is not used in the appropriate clinical setting, misinterpretation of the results can lead to unnecessary cardiac testing. This review provides the primary care provider with basic knowledge about the test's clinical utility, interpretation, risks, and limitations.

ACC/AATS/AHA/ASE/ASNC/HRS/SCAI/SCCT/SCMR/STS 2017 Appropriate Use Criteria for Multimodality Imaging in Valvular Heart Disease: A Report of the American College of Cardiology Appropriate Use Criteria Task Force, American Association for Thoracic Surgery, American Heart Association, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, and Society of Thoracic Surgeons.

This document is 1 of 2 companion appropriate use criteria (AUC) documents developed by the American College of Cardiology, American Association for Thoracic Surgery, American Heart Association, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, and Society of Thoracic Surgeons. This document addresses the evaluation and use of multimodality imaging in the diagnosis and management of valvular heart disease, whereas the second, companion document addresses this topic with regard to structural heart disease. Although there is clinical overlap, the documents addressing valvular and structural heart disease are published separately, albeit with a common structure. The goal of the companion AUC documents is to provide a comprehensive resource for multimodality imaging in the context of valvular and structural heart disease, encompassing multiple imaging modalities. Using standardized methodology, the clinical scenarios (indications) were developed by a diverse writing group to represent patient presentations encountered in everyday practice and included common applications and anticipated uses. Where appropriate, the scenarios were developed on the basis of the most current American College of Cardiology/American Heart Association guidelines. A separate, independent rating panel scored the 92 clinical scenarios in this document on a scale of 1 to 9. Scores of 7 to 9 indicate that a modality is considered appropriate for the clinical scenario presented. Midrange scores of 4 to 6 indicate that a modality may be appropriate for the clinical scenario, and scores of 1 to 3 indicate that a modality is considered rarely appropriate for the clinical scenario. The primary objective of the AUC is to provide a framework for the assessment of these scenarios by practices that will improve and standardize physician decision making. AUC publications reflect an ongoing effort by the American College of Cardiology to critically and systematically create, review, and categorize clinical situations where diagnostic tests and procedures are utilized by physicians caring for patients with cardiovascular diseases. The process is based on the current understanding of the technical capabilities of the imaging modalities examined.

ACC/AATS/AHA/ASE/ASNC/HRS/SCAI/SCCT/SCMR/STS 2017 Appropriate Use Criteria for Multimodality Imaging in Valvular Heart Disease : A Report of the American College of Cardiology Appropriate Use Criteria Task Force, American Association for Thoracic Surgery, American Heart Association, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, and Society of Thoracic Surgeons.

This document is 1 of 2 companion appropriate use criteria (AUC) documents developed by the American College of Cardiology, American Association for Thoracic Surgery, American Heart Association, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, and Society of Thoracic Surgeons. This document addresses the evaluation and use of multimodality imaging in the diagnosis and management of valvular heart disease, whereas the second, companion document addresses this topic with regard to structural heart disease. Although there is clinical overlap, the documents addressing valvular and structural heart disease are published separately, albeit with a common structure. The goal of the companion AUC documents is to provide a comprehensive resource for multimodality imaging in the context of valvular and structural heart disease, encompassing multiple imaging modalities.Using standardized methodology, the clinical scenarios (indications) were developed by a diverse writing group to represent patient presentations encountered in everyday practice and included common applications and anticipated uses. Where appropriate, the scenarios were developed on the basis of the most current American College of Cardiology/American Heart Association guidelines.A separate, independent rating panel scored the 92 clinical scenarios in this document on a scale of 1 to 9. Scores of 7 to 9 indicate that a modality is considered appropriate for the clinical scenario presented. Midrange scores of 4 to 6 indicate that a modality may be appropriate for the clinical scenario, and scores of 1 to 3 indicate that a modality is considered rarely appropriate for the clinical scenario.The primary objective of the AUC is to provide a framework for the assessment of these scenarios by practices that will improve and standardize physician decision making. AUC publications reflect an ongoing effort by the American College of Cardiology to critically and systematically create, review, and categorize clinical situations where diagnostic tests and procedures are utilized by physicians caring for patients with cardiovascular diseases. The process is based on the current understanding of the technical capabilities of the imaging modalities examined.