Gary H. Danton

Thromboembolic Events Predispose the Brain to Widespread Cerebral Infarction After Delayed Transient Global Ischemia in Rats

BACKGROUND AND PURPOSE Transient distal platelet accumulation after common carotid artery thrombosis (CCAT) leads to hemodynamic, metabolic, and molecular events that may influence the response of the postthrombotic brain to secondary insults. We investigated how a thromboembolic insult would affect histopathological outcome when combined with an ischemic insult induced 24 hours later. METHODS Three groups of rats underwent either (1) CCAT+10 minutes of normothermic 2-vessel occlusion (n=6), (2) CCAT+sham ischemia procedures (n=6), or (3) sham CCAT procedures+10 minutes of 2-vessel occlusion (n=6). At 7 days, rats were perfused for quantitative histopathological and immunocytochemical analysis. RESULTS Rats undergoing combined insults (group 1) had significantly larger areas of ischemic injury (P<0.05) within the cerebral cortex, striatum, and thalamus compared with the other, single-injury groups. Increased ischemic damage included selective neuronal necrosis, infarction, and focal hemorrhage. By means of glial fibrillary acidic protein immunocytochemistry and lectin histochemistry, reactive astrocytes and microglia were found to be associated with widespread tissue necrosis. In contrast, infrequent infarction or CA1 hippocampal neuronal necrosis was observed in groups 2 and 3, respectively. CONCLUSIONS A prior thromboembolic event is a risk factor for widespread cerebral infarction and hemorrhage when combined with a delayed ischemic insult. The understanding of what factors enhance the susceptibility of the postthrombotic brain to secondary insults may aid in the development of neuroprotective strategies to be applied after transient ischemic attacks to prevent the initiation of stroke.

Characterization of a thromboembolic photochemical model of repeated stroke in mice.

Many stroke research groups utilize the model of middle cerebral artery occlusion induced by insertion of an intraluminal thread, owing to its pragmatism and reliability of cerebral infarct generation. However, 75% of stroke cases result from a thromboembolic event and 10% from occlusive atherothrombosis in situ. Here, we characterize a mouse model of repeated thromboembolic stroke, which closely mimics the intravascular pathophysiology of arterial thrombus generation from an atherosclerotic plaque, and subsequent release of a thrombus into the cerebral circulation as an embolus. Common carotid artery thrombosis (CCAT) was induced photochemically leading to non-occlusive platelet aggregation in C57/BL6 male mice (n=35), and was followed by mechanical assistance to facilitate release of the thrombus (MRT) and thus promote embolism. Six experimental groups, differing by changes in the surgical protocol, were used for the purpose of determining which such procedure yielded the most reliable and consistent brain infarct volumes with the lowest mortality at 3 days after surgery. The group which best satisfied these conditions was a double insult group which consisted of animals that underwent CCAT for 2 min by means of argon laser irradiation (514.5 nm) at an intensity of ca. 130 W/cm(2), with concomitant injection of erythrosin B (EB) (35 mg/kg infused over those same 2 min), followed by MRT 1 min later; the entire procedure was repeated 24h later. This group showed a percent of brain lesion volume of 15+/-4% (mean+/-S.D.) with no associated 3-day mortality. Compared to a single insult group which sustained a percent brain lesion volume of 7+/-3%, there was a statistically significant (p<0.05) increase in the volume of infarction in the double-insult group.

Endothelial Nitric Oxide Synthase Pathophysiology after Nonocclusive Common Carotid Artery Thrombosis in Rats

Although vascular dysregulation has been documented in patients with extracranial vascular disease, transient ischemic attacks, and stroke, the pathomechanisms are poorly understood. To model thromboembolic stroke in rats, photochemically induced nonocclusive common carotid artery thrombosis (CCAT) was used to generate a platelet thrombus in the carotid artery of anesthetized rats. After CCAT, platelet aggregates break off the thrombus, travel to the distal cerebral vasculature, damage blood vessels, and cause small infarctions. The authors hypothesized that deficits in the endothelial nitric oxide synthase (eNOS) pathway may be responsible for vascular dysfunction after embolic stroke. To examine the functional status of the eNOS system, they measured eNOS-dependent dilation after CCAT by applying acetylcholine through a cranial window over the middle cerebral artery. The authors also measured eNOS mRNA and protein in the middle cerebral artery to determine whether functional changes were caused by alterations in expression. eNOS-dependent dilation was reduced at 6 hours, elevated at 24 hours, and returned to baseline 72 hours after CCAT. Endothelial nitric oxide synthase mRNA increased at 2 hours and was followed by a rise in protein 24 hours after CCAT. Changes in the eNOS system may account for some of the observed vascular deficits in patients with cerebrovascular disease.

Penetrating Diaphragmatic Injury: Accuracy of 64-Section Multidetector CT with Trajectography

PURPOSE To (a) determine the diagnostic performance of 64-section multidetector computed tomography (CT) trajectography for penetrating diaphragmatic injury (PDI), (b) determine the diagnostic performance of classic signs of diaphragmatic injury at 64-section multidetector CT, and (c) compare the performance of these signs with that of trajectography. MATERIALS AND METHODS This HIPAA-compliant retrospective study had institutional review board approval, with a waiver of the informed consent requirement. All patients who had experienced penetrating thoracoabdominal trauma, who had undergone preoperative 64-section multidetector CT of the chest and abdomen, and who had surgical confirmation of findings during a 2.5-year period were included in this study (25 male patients, two female patients; mean age, 32.6 years). After a training session, four trauma radiologists unaware of the surgical outcome independently reviewed all CT studies and scored the probability of PDI on a six-point scale. Collar sign, dependent viscera sign, herniation, contiguous injury on both sides of the diaphragm, discontinuous diaphragm sign, and transdiaphragmatic trajectory were evaluated for sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV). Accuracies were determined and receiver operating characteristic curves were analyzed. RESULTS Sensitivities for detection of PDI by using 64-section multidetector CT with postprocessing software ranged from 73% to 100%, specificities ranged from 50% to 92%, NPVs ranged from 71% to 100%, PPVs ranged from 68% to 92%, and accuracies ranged from 70% to 89%. Discontinuous diaphragm, herniation, collar, and dependent viscera signs were highly specific (92%-100%) but nonsensitive (0%-60%). Contiguous injury was generally more sensitive (80%-93% vs 73%-100%) but less specific (50%-67% vs 83%-92%) than transdiaphragmatic trajectory when patients with multiple entry wounds were included in the analysis. Transdiaphragmatic trajectory was a much more sensitive sign of PDI than previously reported (73%-100% vs 36%), with NPVs ranging from 71% to 100% and PPVs ranging from 85% to 92%. CONCLUSION Sixty-four-section multidetector CT trajectography facilitates the identification of transdiaphragmatic trajectory, which accurately rules in PDI when identified. Contiguous injury remains a highly sensitive sign, even when patients with multiple injuries are considered, and is useful for excluding PDI.

Three-Dimensional Computed Tomographic Analysis of a Rare Left Coronary Artery to Left Ventricle Fistula

A 16-month-old child with a known large coronary fistula between the left coronary artery and left ventricle was referred for computed tomographic (CT) coronary angiography to further characterize the anatomy in anticipation of transcatheter device closure. The diagnosis of this rare coronary anomaly was made initially by echocardiography in the newborn period, and over time, the left ventricle had become dilated with evidence of diastolic dysfunction. A CT coronary angiography was performed using a dual-source CT scanner (Somatom Definition; Siemens Healthcare, Forchheim, Germany) with the child under general anesthesia. Postprocessing was performed on an Aquarius 3D Workstation (TeraRecon Inc., San Mateo, CA, USA). The maximum-intensity projection image shown in Fig. 1 demonstrates the course of the fistula (yellow arrow) as it originates from a dilated left main coronary artery and drains into the left ventricle. The straightened planar reformatted image and its accompanying graph shown in Fig. 2 provide precise measurements of the cross-sectional diameter of the fistula along its course. The yellow and green boxes show cross-sections of the fistula in exact orthogonal planes and exhibit the vessel’s circumferential irregularity. Rotation of the curved planar reformatted image, as shown in Fig. 3, demonstrates the origin of the circumflex coronary artery from the dilated left main coronary artery. Several obtuse marginal branches also are appreciated. The left anterior descending coronary artery is not seen arising from either the left main coronary artery or the fistula. This observation was subsequently confirmed at catheterization, in which atresia of the proximal left anterior descending coronary artery was demonstrated. The distal left anterior descending coronary artery was supplied via collateral vessels from the right coronary artery. The volume-rendered image shown in Fig. 4 demonstrates the fistula arising from behind the main pulmonary artery and entering the anterior aspect of the left ventricle. The hollow view shown in Fig. 5 (also seen in the accompanying video) provides the most dramatic view of the three-dimensional anatomy. Using this advanced software algorithm, unique en face views of the fistula’s origin and drainage site are displayed. The internal mural surface of the coronary fistula is also demonstrated. With the aid of information provided by the CT angiogram, the child underwent successful transcatheter closure of the large coronary artery fistula. The use of advanced imaging CT software not only depicted the course of the fistula and its surrounding anatomy from a three-dimensional perspective but also provided precise anatomic measurements for optimal sizing and positioning of the occluder device. Electronic supplementary material The online version of this article (doi:10.1007/s00246-012-0552-9) contains supplementary material, which is available to authorized users.

Imaging of Foreign Bodies in Prisoners

Foreign body ingestion or insertion is occasionally encountered by radiologists and is associated with significant morbidity, financial burden, and potential mortality. Incarcerated individuals are a unique group where foreign body ingestion or insertion is more common than the general population. Motivations include reprieve from the confines of prison, sexual stimulation or victimization, or may be secondary to compulsions in patients with psychiatric disorders. These foreign bodies may lead to perforation, obstruction, or infection. Radiologists can help clinicians identify unexpected ingested or inserted objects as well as the sequelae of foreign body ingestion or insertion.

Cardiac Physiology for Radiologists: Review of Relevant Physiology for Interpretation of Cardiac MR Imaging and CT

Cardiac computed tomography (CT) and magnetic resonance (MR) imaging provide clinicians with important insights into cardiac physiology and pathology. However, not all radiologists understand the language and concepts of cardiac physiology that are used daily by cardiologists. This review article covers basic cardiac physiology as it relates to cardiac CT and MR imaging. Topics include a review of the cardiac cycle and left ventricular pressure-volume loops as they relate to different pathologic states, evaluation of cardiac function, and calculation of key parameters such as left ventricular volumes and the ejection fraction. The hemodynamics of cardiac shunts are covered, with an emphasis on factors important to cardiologists, including the ratio of pulmonary flow to systemic flow. Additionally, valvular physiologic function is reexamined, with a focus on understanding pressure gradients within the heart and also the changes associated with valvular pathologic conditions, including measurement of regurgitant fractions in patients with valvular insufficiency. Understanding these basic concepts will help radiologists tailor the reporting of cardiac studies to clinically relevant information.

Blunt Chest Trauma: A Radiologic Approach and Review

Blunt chest trauma, a frequent component of trauma admissions, is the second leading cause of death in motor-vehicle accidents. Additionally, it may be associated with significant morbidity in those who survive. Radiography, ultrasonography, and computed tomography (CT) have a widespread role in evaluating blunt chest trauma, importantly aiding in the diagnosis and management of injury. Herein, we discuss the most common salient injuries, imaging protocol considerations and imaging findings associated with acute blunt chest trauma.

Accessory pancreatic lobe in association with a gastric duplication cyst

Gastric duplication cysts are an extremely rare anomaly with few reported cases in association with accessory pancreatic tissue. Diagnosis can be challenging given a presentation of recurrent pancreatitis and resemblance to pancreatic pseudocysts. We report the case of a 6-year old boy with multiple episodes of pancreatitis who was discovered to have an accessory pancreatic lobe connected to a gastric duplication cyst, successfully treated with surgical excision.

Occult Lung Cancer Occluding a Pulmonary Vein with Suspected Venous Infarction, Mimicking Pneumonia and a Pulmonary Embolus

BACKGROUND Patients with lung cancer present to the emergency department (ED) in a variety of ways. Symptoms are often nonspecific and can lead to a delay in diagnosis. Here, a lung cancer mimicked two illnesses, adding to the diagnostic complexity. This case highlights diagnostic pitfalls as well as advantages and limitations of imaging utilized in the emergency setting. CASE REPORT We report a case of an occult lung cancer occluding a pulmonary vein, which at first mimicked pneumonia and later a pulmonary embolism (PE) and arterial lung infarction. The patient presented to the ED with cough and a lung opacity on chest radiograph that was treated with antibiotics. However, recurrent visits to the ED with similar complaints were further investigated with computed tomography angiogram (CTA). At first the scan was considered positive for PE. Further inspection revealed that the CTA findings were not typical for PE, but rather a slow flow state likely caused by an occult mass occluding a pulmonary vein with venous infarction. Biopsy revealed a lung adenocarcinoma. In addition to the case presentation, the typical signs of PE on CTA with correlating images and diagnostic pitfalls are discussed. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case report raises two themes that can be of interest to emergency physicians. The first is that lung cancer has many guises. Here it mimicked two distinctly different diseases, pneumonia and PE. The second is that, although CTA is highly sensitive and specific for diagnosing PE, it has limitations that may lead to false positive readings. When clinical signs and symptoms fail to correlate with the imaging diagnosis, alternative explanations should be sought.