Heart failure is a serious cause of morbidity and mortality with many patients ultimately requiri... more Heart failure is a serious cause of morbidity and mortality with many patients ultimately requiring heart transplantation. As the rate of heart failure continues to increase and surpass the number of available donor hearts, the need for cardiac assist devices is rapidly rising. The total artificial heart has emerged as an effective therapeutic option in patients with end-stage biventricular heart failure who are awaiting orthotopic heart transplantation. The TAH replaces the patient’s native ventricle and valves and has one of the highest bridge to transplant rates. Many complications have been associated with the TAH including infections, bleeding, thrombosis, device malfunction, neurological complications among others. CT is the imaging modality of choice that aids in early recognition of TAH complications. The aim of this review is to illustrate the TAH components and CT based imaging of TAH complications. Recognition of TAH complications can help to plan for early intervention a...
Pathology of the pulmonary vasculature involves an impressive array of both congenital and acquir... more Pathology of the pulmonary vasculature involves an impressive array of both congenital and acquired conditions. While some of these disorders are benign, disruption of the pulmonary vasculature is often incompatible with life, making these conditions critical to identify on imaging. Many reviews of pulmonary vascular pathology approach the pulmonary arteries, pulmonary veins and bronchial arteries as individual topics. The goal of this review is to provide an integrated overview of the high-yield features of all major disorders of the pulmonary vasculature. This approach provides a more cohesive and comprehensive conceptualisation of respiratory pathology. In this review, we present both the salient clinical and imaging features of congenital and acquired disorders of the pulmonary vasculature, to assist the radiologist in identifying pathology and forming a robust differential diagnosis tailored to the presenting patient. Teaching Points • Abnormalities of the pulmonary vasculature are both congenital and acquired. • Pathology of a single pulmonary vascular territory often affects the entire pulmonary vasculature. • Anomalous pulmonary venous flow is named as a function of its location and severity. • Bronchial arteries often undergo dilatation secondary to cardio-respiratory pathology.
Non-malignant oesophageal diseases are critical to recognize, but can be easily overlooked or mis... more Non-malignant oesophageal diseases are critical to recognize, but can be easily overlooked or misdiagnosed radiologically. In this paper, we cover the salient clinical features and imaging findings of non-malignant pathology of the oesophagus. We organize the many non-malignant diseases of the oesophagus into two major categories: luminal disorders and wall disorders. Luminal disorders include dilatation/narrowing (e.g. achalasia, scleroderma, and stricture) and foreign body impaction. Wall disorders include wall thickening (e.g. oesophagitis, benign neoplasms, oesophageal varices, and intramural hematoma), wall thinning/outpouching (e.g. epiphrenic diverticulum, Zenker diverticulum, and Killian-Jamieson diverticulum), wall rupture (e.g. iatrogenic perforation, Boerhaave Syndrome, and Mallory-Weiss Syndrome), and fistula formation (e.g. pericardioesophageal fistula, tracheoesophageal fistula, and aortoesophageal fistula). It is the role of the radiologist to recognize the classic imaging patterns of these nonmalignant oesophageal diseases to facilitate the delivery of appropriate and prompt medical treatment. Teaching Points • Nonmalignant oesophageal disease can be categorised by the imaging appearance of wall and lumen. • Scleroderma and achalasia both cause lumen dilatation via different pathophysiologic pathways. • Oesophageal wall thickening can be inflammatory, neoplastic, traumatic, or vascular in aetiology.
The purpose of this study is to identify early computed tomography findings around the driveline ... more The purpose of this study is to identify early computed tomography findings around the driveline which would predict mediastinal or left ventricular assist device (LVAD) pocket abscess formation. A retrospective analysis was performed on 128 LVAD recipients between January 2007 and December 2011. Infectious complications were subdivided into those affecting the driveline and those resulting in abscess formation either around the LVAD pump or mediastinum. The size and location of infiltrative changes surrounding the driveline were used to predict infection propagation resulting in abscess. Of the 128 patients, 49 (38.3%) patients developed driveline infections and 24 (18.8%) patients developed abscess. 87.5% patients who developed abscess had a preceding driveline infection. The mean time from driveline infection to the development of pump pocket abscess was approximately 7 months. In addition, patients with abscess in the pump pocket or mediastinum had preceding infiltrative changes...
Anomalies of the bronchus can be both congenital and acquired. Several different congenital aberr... more Anomalies of the bronchus can be both congenital and acquired. Several different congenital aberrations of the bronchial anatomy are commonly encountered including tracheal bronchus, accessory cardiac bronchus, and bronchial agenesis/aplasia/hypoplasia. In addition, Williams-Campbell syndrome and cystic fibrosis are two other congenital conditions that result in bronchial pathology. Acquired pathology affecting the bronchi can typically be divided into three broad categories of bronchial disease: bronchial wall thickening, dilatation/bronchiectasis, and obstruction/stenosis. Bronchial wall thickening is the common final response of the airways to irritants, which cause the bronchi to become swollen and inflamed. Bronchiectasis/bronchial dilatation can develop in response to many aetiologies, including acquired conditions such as infection, pulmonary fibrosis, recurrent or chronic aspiration, as well as because of congenital conditions such as cystic fibrosis. The causes of obstructi...
Radiographics : a review publication of the Radiological Society of North America, Inc, Jan 10, 2017
The ribs are frequently affected by blunt or penetrating injury to the thorax. In the emergency d... more The ribs are frequently affected by blunt or penetrating injury to the thorax. In the emergency department setting, it is vital for the interpreting radiologist to not only identify the presence of rib injuries but also alert the clinician about organ-specific injury, specific traumatic patterns, and acute rib trauma complications that require emergent attention. Rib injuries can be separated into specific morphologic fracture patterns that include stress, buckle, nondisplaced, displaced, segmental, and pathologic fractures. Specific attention is also required for flail chest and for fractures due to pediatric nonaccidental trauma. Rib fractures are associated with significant morbidity and mortality, both of which increase as the number of fractured ribs increases. Key complications associated with rib fracture include pain, hemothorax, pneumothorax, extrapleural hematoma, pulmonary contusion, pulmonary laceration, acute vascular injury, and abdominal solid-organ injury. Congenital...
Transcatheter Aortic Valve Implantation (TAVI) is increasingly being used in patients with severe... more Transcatheter Aortic Valve Implantation (TAVI) is increasingly being used in patients with severe aortic stenosis who are not candidates for surgery. ECG-gated CT angiography (CTA) plays an important role in the preoperative planning for these devices. As the number of patients undergoing these procedures increases, a subset of patients is being recognized who have contraindications to iodinated contrast medium, either due to a prior severe allergic type reaction or poor renal function. Another subgroup of patients with low flow and low gradient aortic stenosis is being recognized that are usually assessed for severity of aortic stenosis by stress echocardiography. There are contraindications to stress echocardiography and some of these patients may not be able to undergo this test. Non-contrast MRI can be a useful emerging modality for evaluating these patients. In this article, we discuss the emerging indications of noncontrast MRI in preoperative assessment for TAVI and describe the commonly used MRI sequences. A comparison of the most important measurements obtained for TAVI assessment on CTA and MRI from same subjects is included.
Phase contrast X-ray computed tomography (PCI-CT) has recently emerged as a novel imaging techniq... more Phase contrast X-ray computed tomography (PCI-CT) has recently emerged as a novel imaging technique that allows visualization of cartilage soft tissue, subsequent examination of chondrocyte patterns, and their correlation to osteoarthritis. Previous studies have shown that 2D texture features are effective at distinguishing between healthy and osteoarthritic regions of interest annotated in the radial zone of cartilage matrix on PCI-CT images. In this study, we further extend the texture analysis to 3D and investigate the ability of volumetric texture features at characterizing chondrocyte patterns in the cartilage matrix for purposes of classification. Here, we extracted volumetric texture features derived from Minkowski Functionals and gray-level cooccurrence matrices (GLCM) from 496 volumes of interest (VOI) annotated on PCI-CT images of human patellar cartilage specimens. The extracted features were then used in a machine-learning task involving support vector regression to classify ROIs as healthy or osteoarthritic. Classification performance was evaluated using the area under the receiver operating characteristic (ROC) curve (AUC). The best classification performance was observed with GLCM features correlation (AUC = 0.83 ± 0.06) and homogeneity (AUC = 0.82 ± 0.07), which significantly outperformed all Minkowski Functionals (p < 0.05). These results suggest that such quantitative analysis of chondrocyte patterns in human patellar cartilage matrix involving GLCM-derived statistical features can distinguish between healthy and osteoarthritic tissue with high accuracy.
Functional MRI (fMRI) is currently used to investigate structural and functional connectivity in ... more Functional MRI (fMRI) is currently used to investigate structural and functional connectivity in human brain networks. To this end, previous studies have proposed computational methods that involve assumptions that can induce information loss, such as assumed linear coupling of the fMRI signals or requiring dimension reduction. This study presents a new computational framework for investigating the functional connectivity in the brain and recovering network structure while reducing the information loss inherent in previous methods. For this purpose, pairwise mutual information (MI) was extracted from all pixel time series within the brain on restingstate fMRI data. Non-metric topographic mapping of proximity (TMP) data was subsequently applied to recover network structure from the pair-wise MI analysis. Our computational framework is demonstrated in the task of identifying regions of the primary motor cortex network on resting state fMRI data. For ground truth comparison, we also localized regions of the primary motor cortex associated with hand movement in a task-based fMRI sequence with a finger-tapping stimulus function. The similarity between our pair-wise MI clustering results and the ground truth is evaluated using the dice coefficient. Our results show that non-metric clustering with the TMP algorithm, as performed on pair-wise MI analysis, was able to detect the primary motor cortex network and achieved a dice coefficient of 0.53 in terms of overlap with the ground truth. Thus, we conclude that our computational framework can extract and visualize valuable information concerning the underlying network structure between different regions of the brain in resting state fMRI.
We explore a computational framework for functional connectivity analysis in resting-state functi... more We explore a computational framework for functional connectivity analysis in resting-state functional MRI (fMRI) data acquired from the human brain for recovering the underlying network structure and understanding causality between network components. Termed mutual connectivity analysis (MCA), this framework involves two steps, the first of which is to evaluate the pair-wise cross-prediction performance between fMRI pixel time series within the brain. In a second step, the underlying network structure is subsequently recovered from the affinity matrix using nonmetric network clustering approaches, such as the so-called Louvain method. Finally, we use convergent cross-mapping (CCM) to study causality between different network components. We demonstrate our MCA framework in the problem of recovering the motor cortex network associated with hand movement from resting state fMRI data. Results are compared with a ground truth of active motor cortex regions as identified by a task-based fMRI sequence involving a finger-tapping stimulation experiment. Our results regarding causation between regions of the motor cortex revealed a significant directional variability and were not readily interpretable in a consistent manner across subjects. However, our results on whole-slice fMRI analysis demonstrate that MCA-based model-free recovery of regions associated with the primary motor cortex and supplementary motor area are in close agreement with localization of similar regions achieved with a task-based fMRI acquisition. Thus, we conclude that our MCA methodology can extract and visualize valuable information concerning the underlying network structure between different regions of the brain in resting state fMRI.
While the proximal femur is preferred for measuring bone mineral density (BMD) in fracture risk e... more While the proximal femur is preferred for measuring bone mineral density (BMD) in fracture risk estimation, the introduction of volumetric quantitative computed tomography has revealed stronger associations between BMD and spinal fracture status. In this study, we propose to capture properties of trabecular bone structure in spinal vertebrae with advanced second-order statistical features for purposes of fracture risk assessment. For this purpose, axial multi-detector CT (MDCT) images were acquired from 28 spinal vertebrae specimens using a whole-body 256-row CT scanner with a dedicated calibration phantom. A semi-automated method was used to annotate the trabecular compartment in the central vertebral slice with a circular region of interest (ROI) to exclude cortical bone; pixels within were converted to values indicative of BMD. Six second-order statistical features derived from gray-level co-occurrence matrices (GLCM) and the mean BMD within the ROI were then extracted and used in conjunction with a generalized radial basis functions (GRBF) neural network to predict the failure load of the specimens; true failure load was measured through biomechanical testing. Prediction performance was evaluated with a root-meansquare error (RMSE) metric. The best prediction performance was observed with GLCM feature 'correlation' (RMSE = 1.02 ± 0.18), which significantly outperformed all other GLCM features (p < 0.01). GLCM feature correlation also significantly outperformed MDCT-measured mean BMD (RMSE = 1.11 ± 0.17) (p < 10 −4). These results suggest that biomechanical strength prediction in spinal vertebrae can be significantly improved through characterization of trabecular bone structure with GLCM-derived texture features.
Background Pulmonary arteries are not just affected by thrombus. Congenital and acquired conditio... more Background Pulmonary arteries are not just affected by thrombus. Congenital and acquired conditions can also involve the pulmonary arteries. An awareness of these conditions is important for the radiologist interpreting chest computed tomography (CT). Methods The anatomy of the pulmonary arteries was reviewed. CT and magnetic resonance (MR) acquisition protocols for imaging the pulmonary arteries were discussed. The imaging appearances of congenital and acquired anomalies involving the pulmonary arteries, using CT and other modalities, were presented. Results Imaging features of congenital anomalies presented include pulmonary agenesis, partial pulmonary artery agenesis, patent ductus arteriosus, pulmonary artery sling, congenital pulmonary artery stenosis and coronary to pulmonary artery fistula. Acquired pulmonary artery anomalies discussed include arteritis, infected aneurysm and sarcoma. Pulmonary artery filling defects besides thromboembolism are also discussed, including foreign body emboli. Imaging features of bronchogenic carcinoma and mediastinal fibrosis demonstrating compression of the pulmonary arteries are presented, followed by a brief discussion of post repair appearance of the pulmonary arteries for congenital heart disease. Conclusions Congenital and acquired pulmonary artery anomalies have a characteristic appearance on a variety of imaging modalities. An acquaintance with the imaging features of these anomalies is needed to avoid misinterpretation and reach the correct diagnosis. Teaching Points • Discuss a variety of congenital and acquired anomalies of the pulmonary arteries. • Discuss the imaging appearance of the presented congenital or acquired pulmonary artery anomalies. • Describe CT and MR acquisition protocols for imaging the pulmonary arteries. • Review the anatomy of the pulmonary arteries.
Proceedings of the National Academy of Sciences, 1998
Novel anti-neoplastic agents such as gene targeting vectors and encapsulated carriers are quite l... more Novel anti-neoplastic agents such as gene targeting vectors and encapsulated carriers are quite large (approximately 100–300 nm in diameter). An understanding of the functional size and physiological regulation of transvascular pathways is necessary to optimize delivery of these agents. Here we analyze the functional limits of transvascular transport and its modulation by the microenvironment. One human and five murine tumors including mammary and colorectal carcinomas, hepatoma, glioma, and sarcoma were implanted in the dorsal skin-fold chamber or cranial window, and the pore cutoff size, a functional measure of transvascular gap size, was determined. The microenvironment was modulated: ( i ) spatially, by growing tumors in subcutaneous or cranial locations and ( ii ) temporally, by inducing vascular regression in hormone-dependent tumors. Tumors grown subcutaneously exhibited a characteristic pore cutoff size ranging from 200 nm to 1.2 μm. This pore cutoff size was reduced in tumo...
found no microorganisms. In the absence of a fistula or empyema, it was concluded that the drop i... more found no microorganisms. In the absence of a fistula or empyema, it was concluded that the drop in air-fluid level was most likely due to severe dehydration. After rehydration and suspension of diuretics, the left postpneumonectomy space fluid began to reaccumulate, and the patient improved clinically. He has had no recurrence of this problem during follow-up of 8 months. Comment A literature review using the search terms "postpneumonectomy space," "emptying," and "fluid," identified 19 cases, none of which could be attributed to dehydration. Although we believe that thoracic surgeons are aware of spontaneous emptying of the postpneumonectomy space, it is rarely reported in the literature. Suggested causes include a small valvelike bronchopleural fistula that heals spontaneously [3] and escape of pleural fluid into the chest wall or through diaphragmatic defects [4]. Confirmation of a small BPF, too small to see on computed tomography, is usually made by bronchoscopy. It may be helpful to do this with general anesthesia so that positive pressure can be easily applied so as to distend the bronchus and demonstrate a leak. Other methods that have been or are still used include contrast bronchography, intrapleural methylene blue, and ventilation scintigraphy [5]. The key clinical feature in our patient, which led us to believe that there may not be a fistula, was the absence of a productive cough. Return of the fluid level with rehydration gave evidence in favor of this hypothesis. Such fluid shifts between compartments can be explained in simple physiological terms with homeostatic mechanisms preserving intravascular volume. The clinical importance of recognizing the syndrome of benign emptying of the postpneumonectomy space [4] relates to avoidance of the complications that might arise from unnecessary instrumentation of the postpneumonectomy space. When postpneumonectomy BPF is suspected, early drainage is generally encouraged. However, we would advise that, in appropriate circumstances, confirmation of a fistula or infection be obtained; otherwise, a sterile postpneumonectomy space may become contaminated, with the undesirable consequences that this would entail.
Va s c u l a r a n d I nt e r ve nt io n a l R a d io l og y • R ev iew CME/SAM This article is a... more Va s c u l a r a n d I nt e r ve nt io n a l R a d io l og y • R ev iew CME/SAM This article is available for CME/SAM credit. See www.arrs.org for more information.
The large airways can be affected by a wide spectrum of acquired benign and malignant diseases. T... more The large airways can be affected by a wide spectrum of acquired benign and malignant diseases. These lesions may present as focal or diffuse processes and with narrowing or widening of the airway. Some of these may be asymptomatic for quite some time and may be incidentally detected on imaging, while others may be symptomatic, causing airway compromise. There may be a characteristic radiograph and computed tomography (CT) appearance, suggesting a narrow differential. When the imaging findings are not definitive, tissue may be obtained for pathological analysis. It behooves the radiologist to be familiar with the pathologic findings that correlate with the radiographic or CT appearance of the most frequently seen large airway lesions. In this way, we may improve our diagnostic accuracy. This paper will present the imaging findings of the most prevalent tracheobronchial lesions along with any associated pathology. Teaching Points • The large airways can be affected by many acquired benign and malignant diseases. • Large airway lesions may present as focal or diffuse processes, with narrowing or widening. • There may or may not be characteristic imaging appearance of large airway disease. • If imaging findings are not definitive, tissue may be obtained for pathological analysis.
Ambulatory cancer patients at high-risk for venous thromboembolism (VTE) can be identified using ... more Ambulatory cancer patients at high-risk for venous thromboembolism (VTE) can be identified using a validated risk score (Khorana score). We evaluated the benefit of outpatient thromboprophylaxis with dalteparin in high-risk patients in a multicenter randomized study. Cancer patients with Khorana score≥3 starting a new systemic regimen were screened for VTE and if negative randomized to dalteparin 5000units daily or observation for 12weeks. Subjects were screened with lower extremity ultrasounds every 4weeks on study and with chest CT at 12weeks. The primary efficacy endpoint was all VTE over 12weeks and primary safety endpoint was clinically relevant bleeding events over 13weeks. The study was terminated early due to low accrual. Of 117 enrolled patients, 10 (8.5%) had VTE on baseline screening and were not randomized. Of 98 randomized patients, VTE occurred in 12% (N=6/50) of patients on dalteparin and 21% (N=10/48) on observation (hazard ratio, HR 0.69, 95% CI 0.23-1.89). Major bl...
Heart failure is a serious cause of morbidity and mortality with many patients ultimately requiri... more Heart failure is a serious cause of morbidity and mortality with many patients ultimately requiring heart transplantation. As the rate of heart failure continues to increase and surpass the number of available donor hearts, the need for cardiac assist devices is rapidly rising. The total artificial heart has emerged as an effective therapeutic option in patients with end-stage biventricular heart failure who are awaiting orthotopic heart transplantation. The TAH replaces the patient’s native ventricle and valves and has one of the highest bridge to transplant rates. Many complications have been associated with the TAH including infections, bleeding, thrombosis, device malfunction, neurological complications among others. CT is the imaging modality of choice that aids in early recognition of TAH complications. The aim of this review is to illustrate the TAH components and CT based imaging of TAH complications. Recognition of TAH complications can help to plan for early intervention a...
Pathology of the pulmonary vasculature involves an impressive array of both congenital and acquir... more Pathology of the pulmonary vasculature involves an impressive array of both congenital and acquired conditions. While some of these disorders are benign, disruption of the pulmonary vasculature is often incompatible with life, making these conditions critical to identify on imaging. Many reviews of pulmonary vascular pathology approach the pulmonary arteries, pulmonary veins and bronchial arteries as individual topics. The goal of this review is to provide an integrated overview of the high-yield features of all major disorders of the pulmonary vasculature. This approach provides a more cohesive and comprehensive conceptualisation of respiratory pathology. In this review, we present both the salient clinical and imaging features of congenital and acquired disorders of the pulmonary vasculature, to assist the radiologist in identifying pathology and forming a robust differential diagnosis tailored to the presenting patient. Teaching Points • Abnormalities of the pulmonary vasculature are both congenital and acquired. • Pathology of a single pulmonary vascular territory often affects the entire pulmonary vasculature. • Anomalous pulmonary venous flow is named as a function of its location and severity. • Bronchial arteries often undergo dilatation secondary to cardio-respiratory pathology.
Non-malignant oesophageal diseases are critical to recognize, but can be easily overlooked or mis... more Non-malignant oesophageal diseases are critical to recognize, but can be easily overlooked or misdiagnosed radiologically. In this paper, we cover the salient clinical features and imaging findings of non-malignant pathology of the oesophagus. We organize the many non-malignant diseases of the oesophagus into two major categories: luminal disorders and wall disorders. Luminal disorders include dilatation/narrowing (e.g. achalasia, scleroderma, and stricture) and foreign body impaction. Wall disorders include wall thickening (e.g. oesophagitis, benign neoplasms, oesophageal varices, and intramural hematoma), wall thinning/outpouching (e.g. epiphrenic diverticulum, Zenker diverticulum, and Killian-Jamieson diverticulum), wall rupture (e.g. iatrogenic perforation, Boerhaave Syndrome, and Mallory-Weiss Syndrome), and fistula formation (e.g. pericardioesophageal fistula, tracheoesophageal fistula, and aortoesophageal fistula). It is the role of the radiologist to recognize the classic imaging patterns of these nonmalignant oesophageal diseases to facilitate the delivery of appropriate and prompt medical treatment. Teaching Points • Nonmalignant oesophageal disease can be categorised by the imaging appearance of wall and lumen. • Scleroderma and achalasia both cause lumen dilatation via different pathophysiologic pathways. • Oesophageal wall thickening can be inflammatory, neoplastic, traumatic, or vascular in aetiology.
The purpose of this study is to identify early computed tomography findings around the driveline ... more The purpose of this study is to identify early computed tomography findings around the driveline which would predict mediastinal or left ventricular assist device (LVAD) pocket abscess formation. A retrospective analysis was performed on 128 LVAD recipients between January 2007 and December 2011. Infectious complications were subdivided into those affecting the driveline and those resulting in abscess formation either around the LVAD pump or mediastinum. The size and location of infiltrative changes surrounding the driveline were used to predict infection propagation resulting in abscess. Of the 128 patients, 49 (38.3%) patients developed driveline infections and 24 (18.8%) patients developed abscess. 87.5% patients who developed abscess had a preceding driveline infection. The mean time from driveline infection to the development of pump pocket abscess was approximately 7 months. In addition, patients with abscess in the pump pocket or mediastinum had preceding infiltrative changes...
Anomalies of the bronchus can be both congenital and acquired. Several different congenital aberr... more Anomalies of the bronchus can be both congenital and acquired. Several different congenital aberrations of the bronchial anatomy are commonly encountered including tracheal bronchus, accessory cardiac bronchus, and bronchial agenesis/aplasia/hypoplasia. In addition, Williams-Campbell syndrome and cystic fibrosis are two other congenital conditions that result in bronchial pathology. Acquired pathology affecting the bronchi can typically be divided into three broad categories of bronchial disease: bronchial wall thickening, dilatation/bronchiectasis, and obstruction/stenosis. Bronchial wall thickening is the common final response of the airways to irritants, which cause the bronchi to become swollen and inflamed. Bronchiectasis/bronchial dilatation can develop in response to many aetiologies, including acquired conditions such as infection, pulmonary fibrosis, recurrent or chronic aspiration, as well as because of congenital conditions such as cystic fibrosis. The causes of obstructi...
Radiographics : a review publication of the Radiological Society of North America, Inc, Jan 10, 2017
The ribs are frequently affected by blunt or penetrating injury to the thorax. In the emergency d... more The ribs are frequently affected by blunt or penetrating injury to the thorax. In the emergency department setting, it is vital for the interpreting radiologist to not only identify the presence of rib injuries but also alert the clinician about organ-specific injury, specific traumatic patterns, and acute rib trauma complications that require emergent attention. Rib injuries can be separated into specific morphologic fracture patterns that include stress, buckle, nondisplaced, displaced, segmental, and pathologic fractures. Specific attention is also required for flail chest and for fractures due to pediatric nonaccidental trauma. Rib fractures are associated with significant morbidity and mortality, both of which increase as the number of fractured ribs increases. Key complications associated with rib fracture include pain, hemothorax, pneumothorax, extrapleural hematoma, pulmonary contusion, pulmonary laceration, acute vascular injury, and abdominal solid-organ injury. Congenital...
Transcatheter Aortic Valve Implantation (TAVI) is increasingly being used in patients with severe... more Transcatheter Aortic Valve Implantation (TAVI) is increasingly being used in patients with severe aortic stenosis who are not candidates for surgery. ECG-gated CT angiography (CTA) plays an important role in the preoperative planning for these devices. As the number of patients undergoing these procedures increases, a subset of patients is being recognized who have contraindications to iodinated contrast medium, either due to a prior severe allergic type reaction or poor renal function. Another subgroup of patients with low flow and low gradient aortic stenosis is being recognized that are usually assessed for severity of aortic stenosis by stress echocardiography. There are contraindications to stress echocardiography and some of these patients may not be able to undergo this test. Non-contrast MRI can be a useful emerging modality for evaluating these patients. In this article, we discuss the emerging indications of noncontrast MRI in preoperative assessment for TAVI and describe the commonly used MRI sequences. A comparison of the most important measurements obtained for TAVI assessment on CTA and MRI from same subjects is included.
Phase contrast X-ray computed tomography (PCI-CT) has recently emerged as a novel imaging techniq... more Phase contrast X-ray computed tomography (PCI-CT) has recently emerged as a novel imaging technique that allows visualization of cartilage soft tissue, subsequent examination of chondrocyte patterns, and their correlation to osteoarthritis. Previous studies have shown that 2D texture features are effective at distinguishing between healthy and osteoarthritic regions of interest annotated in the radial zone of cartilage matrix on PCI-CT images. In this study, we further extend the texture analysis to 3D and investigate the ability of volumetric texture features at characterizing chondrocyte patterns in the cartilage matrix for purposes of classification. Here, we extracted volumetric texture features derived from Minkowski Functionals and gray-level cooccurrence matrices (GLCM) from 496 volumes of interest (VOI) annotated on PCI-CT images of human patellar cartilage specimens. The extracted features were then used in a machine-learning task involving support vector regression to classify ROIs as healthy or osteoarthritic. Classification performance was evaluated using the area under the receiver operating characteristic (ROC) curve (AUC). The best classification performance was observed with GLCM features correlation (AUC = 0.83 ± 0.06) and homogeneity (AUC = 0.82 ± 0.07), which significantly outperformed all Minkowski Functionals (p < 0.05). These results suggest that such quantitative analysis of chondrocyte patterns in human patellar cartilage matrix involving GLCM-derived statistical features can distinguish between healthy and osteoarthritic tissue with high accuracy.
Functional MRI (fMRI) is currently used to investigate structural and functional connectivity in ... more Functional MRI (fMRI) is currently used to investigate structural and functional connectivity in human brain networks. To this end, previous studies have proposed computational methods that involve assumptions that can induce information loss, such as assumed linear coupling of the fMRI signals or requiring dimension reduction. This study presents a new computational framework for investigating the functional connectivity in the brain and recovering network structure while reducing the information loss inherent in previous methods. For this purpose, pairwise mutual information (MI) was extracted from all pixel time series within the brain on restingstate fMRI data. Non-metric topographic mapping of proximity (TMP) data was subsequently applied to recover network structure from the pair-wise MI analysis. Our computational framework is demonstrated in the task of identifying regions of the primary motor cortex network on resting state fMRI data. For ground truth comparison, we also localized regions of the primary motor cortex associated with hand movement in a task-based fMRI sequence with a finger-tapping stimulus function. The similarity between our pair-wise MI clustering results and the ground truth is evaluated using the dice coefficient. Our results show that non-metric clustering with the TMP algorithm, as performed on pair-wise MI analysis, was able to detect the primary motor cortex network and achieved a dice coefficient of 0.53 in terms of overlap with the ground truth. Thus, we conclude that our computational framework can extract and visualize valuable information concerning the underlying network structure between different regions of the brain in resting state fMRI.
We explore a computational framework for functional connectivity analysis in resting-state functi... more We explore a computational framework for functional connectivity analysis in resting-state functional MRI (fMRI) data acquired from the human brain for recovering the underlying network structure and understanding causality between network components. Termed mutual connectivity analysis (MCA), this framework involves two steps, the first of which is to evaluate the pair-wise cross-prediction performance between fMRI pixel time series within the brain. In a second step, the underlying network structure is subsequently recovered from the affinity matrix using nonmetric network clustering approaches, such as the so-called Louvain method. Finally, we use convergent cross-mapping (CCM) to study causality between different network components. We demonstrate our MCA framework in the problem of recovering the motor cortex network associated with hand movement from resting state fMRI data. Results are compared with a ground truth of active motor cortex regions as identified by a task-based fMRI sequence involving a finger-tapping stimulation experiment. Our results regarding causation between regions of the motor cortex revealed a significant directional variability and were not readily interpretable in a consistent manner across subjects. However, our results on whole-slice fMRI analysis demonstrate that MCA-based model-free recovery of regions associated with the primary motor cortex and supplementary motor area are in close agreement with localization of similar regions achieved with a task-based fMRI acquisition. Thus, we conclude that our MCA methodology can extract and visualize valuable information concerning the underlying network structure between different regions of the brain in resting state fMRI.
While the proximal femur is preferred for measuring bone mineral density (BMD) in fracture risk e... more While the proximal femur is preferred for measuring bone mineral density (BMD) in fracture risk estimation, the introduction of volumetric quantitative computed tomography has revealed stronger associations between BMD and spinal fracture status. In this study, we propose to capture properties of trabecular bone structure in spinal vertebrae with advanced second-order statistical features for purposes of fracture risk assessment. For this purpose, axial multi-detector CT (MDCT) images were acquired from 28 spinal vertebrae specimens using a whole-body 256-row CT scanner with a dedicated calibration phantom. A semi-automated method was used to annotate the trabecular compartment in the central vertebral slice with a circular region of interest (ROI) to exclude cortical bone; pixels within were converted to values indicative of BMD. Six second-order statistical features derived from gray-level co-occurrence matrices (GLCM) and the mean BMD within the ROI were then extracted and used in conjunction with a generalized radial basis functions (GRBF) neural network to predict the failure load of the specimens; true failure load was measured through biomechanical testing. Prediction performance was evaluated with a root-meansquare error (RMSE) metric. The best prediction performance was observed with GLCM feature 'correlation' (RMSE = 1.02 ± 0.18), which significantly outperformed all other GLCM features (p < 0.01). GLCM feature correlation also significantly outperformed MDCT-measured mean BMD (RMSE = 1.11 ± 0.17) (p < 10 −4). These results suggest that biomechanical strength prediction in spinal vertebrae can be significantly improved through characterization of trabecular bone structure with GLCM-derived texture features.
Background Pulmonary arteries are not just affected by thrombus. Congenital and acquired conditio... more Background Pulmonary arteries are not just affected by thrombus. Congenital and acquired conditions can also involve the pulmonary arteries. An awareness of these conditions is important for the radiologist interpreting chest computed tomography (CT). Methods The anatomy of the pulmonary arteries was reviewed. CT and magnetic resonance (MR) acquisition protocols for imaging the pulmonary arteries were discussed. The imaging appearances of congenital and acquired anomalies involving the pulmonary arteries, using CT and other modalities, were presented. Results Imaging features of congenital anomalies presented include pulmonary agenesis, partial pulmonary artery agenesis, patent ductus arteriosus, pulmonary artery sling, congenital pulmonary artery stenosis and coronary to pulmonary artery fistula. Acquired pulmonary artery anomalies discussed include arteritis, infected aneurysm and sarcoma. Pulmonary artery filling defects besides thromboembolism are also discussed, including foreign body emboli. Imaging features of bronchogenic carcinoma and mediastinal fibrosis demonstrating compression of the pulmonary arteries are presented, followed by a brief discussion of post repair appearance of the pulmonary arteries for congenital heart disease. Conclusions Congenital and acquired pulmonary artery anomalies have a characteristic appearance on a variety of imaging modalities. An acquaintance with the imaging features of these anomalies is needed to avoid misinterpretation and reach the correct diagnosis. Teaching Points • Discuss a variety of congenital and acquired anomalies of the pulmonary arteries. • Discuss the imaging appearance of the presented congenital or acquired pulmonary artery anomalies. • Describe CT and MR acquisition protocols for imaging the pulmonary arteries. • Review the anatomy of the pulmonary arteries.
Proceedings of the National Academy of Sciences, 1998
Novel anti-neoplastic agents such as gene targeting vectors and encapsulated carriers are quite l... more Novel anti-neoplastic agents such as gene targeting vectors and encapsulated carriers are quite large (approximately 100–300 nm in diameter). An understanding of the functional size and physiological regulation of transvascular pathways is necessary to optimize delivery of these agents. Here we analyze the functional limits of transvascular transport and its modulation by the microenvironment. One human and five murine tumors including mammary and colorectal carcinomas, hepatoma, glioma, and sarcoma were implanted in the dorsal skin-fold chamber or cranial window, and the pore cutoff size, a functional measure of transvascular gap size, was determined. The microenvironment was modulated: ( i ) spatially, by growing tumors in subcutaneous or cranial locations and ( ii ) temporally, by inducing vascular regression in hormone-dependent tumors. Tumors grown subcutaneously exhibited a characteristic pore cutoff size ranging from 200 nm to 1.2 μm. This pore cutoff size was reduced in tumo...
found no microorganisms. In the absence of a fistula or empyema, it was concluded that the drop i... more found no microorganisms. In the absence of a fistula or empyema, it was concluded that the drop in air-fluid level was most likely due to severe dehydration. After rehydration and suspension of diuretics, the left postpneumonectomy space fluid began to reaccumulate, and the patient improved clinically. He has had no recurrence of this problem during follow-up of 8 months. Comment A literature review using the search terms "postpneumonectomy space," "emptying," and "fluid," identified 19 cases, none of which could be attributed to dehydration. Although we believe that thoracic surgeons are aware of spontaneous emptying of the postpneumonectomy space, it is rarely reported in the literature. Suggested causes include a small valvelike bronchopleural fistula that heals spontaneously [3] and escape of pleural fluid into the chest wall or through diaphragmatic defects [4]. Confirmation of a small BPF, too small to see on computed tomography, is usually made by bronchoscopy. It may be helpful to do this with general anesthesia so that positive pressure can be easily applied so as to distend the bronchus and demonstrate a leak. Other methods that have been or are still used include contrast bronchography, intrapleural methylene blue, and ventilation scintigraphy [5]. The key clinical feature in our patient, which led us to believe that there may not be a fistula, was the absence of a productive cough. Return of the fluid level with rehydration gave evidence in favor of this hypothesis. Such fluid shifts between compartments can be explained in simple physiological terms with homeostatic mechanisms preserving intravascular volume. The clinical importance of recognizing the syndrome of benign emptying of the postpneumonectomy space [4] relates to avoidance of the complications that might arise from unnecessary instrumentation of the postpneumonectomy space. When postpneumonectomy BPF is suspected, early drainage is generally encouraged. However, we would advise that, in appropriate circumstances, confirmation of a fistula or infection be obtained; otherwise, a sterile postpneumonectomy space may become contaminated, with the undesirable consequences that this would entail.
Va s c u l a r a n d I nt e r ve nt io n a l R a d io l og y • R ev iew CME/SAM This article is a... more Va s c u l a r a n d I nt e r ve nt io n a l R a d io l og y • R ev iew CME/SAM This article is available for CME/SAM credit. See www.arrs.org for more information.
The large airways can be affected by a wide spectrum of acquired benign and malignant diseases. T... more The large airways can be affected by a wide spectrum of acquired benign and malignant diseases. These lesions may present as focal or diffuse processes and with narrowing or widening of the airway. Some of these may be asymptomatic for quite some time and may be incidentally detected on imaging, while others may be symptomatic, causing airway compromise. There may be a characteristic radiograph and computed tomography (CT) appearance, suggesting a narrow differential. When the imaging findings are not definitive, tissue may be obtained for pathological analysis. It behooves the radiologist to be familiar with the pathologic findings that correlate with the radiographic or CT appearance of the most frequently seen large airway lesions. In this way, we may improve our diagnostic accuracy. This paper will present the imaging findings of the most prevalent tracheobronchial lesions along with any associated pathology. Teaching Points • The large airways can be affected by many acquired benign and malignant diseases. • Large airway lesions may present as focal or diffuse processes, with narrowing or widening. • There may or may not be characteristic imaging appearance of large airway disease. • If imaging findings are not definitive, tissue may be obtained for pathological analysis.
Ambulatory cancer patients at high-risk for venous thromboembolism (VTE) can be identified using ... more Ambulatory cancer patients at high-risk for venous thromboembolism (VTE) can be identified using a validated risk score (Khorana score). We evaluated the benefit of outpatient thromboprophylaxis with dalteparin in high-risk patients in a multicenter randomized study. Cancer patients with Khorana score≥3 starting a new systemic regimen were screened for VTE and if negative randomized to dalteparin 5000units daily or observation for 12weeks. Subjects were screened with lower extremity ultrasounds every 4weeks on study and with chest CT at 12weeks. The primary efficacy endpoint was all VTE over 12weeks and primary safety endpoint was clinically relevant bleeding events over 13weeks. The study was terminated early due to low accrual. Of 117 enrolled patients, 10 (8.5%) had VTE on baseline screening and were not randomized. Of 98 randomized patients, VTE occurred in 12% (N=6/50) of patients on dalteparin and 21% (N=10/48) on observation (hazard ratio, HR 0.69, 95% CI 0.23-1.89). Major bl...
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Papers by Susan Hobbs