Andrew J. Misselt

MR Imaging of Cardiac Masses

Cardiac MR imaging is the preferred method for assessment of cardiac masses. A comprehensive cardiac MR imaging examination for a cardiac mass consists of static morphologic images using fast spin-echo sequences, including single-shot techniques, with T1 and T2 weighting and fat suppression pulses as well as dynamic imaging with cine steady-state free precession techniques. Further tissue characterization is provided with perfusion and delayed enhancement imaging. Specific cardiac tumoral characterization is possible in many cases. When specific tumor characterization is not possible, MR imaging often can demonstrate aggressive versus nonaggressive features that help in differentiating malignant from benign tumors.

MR Imaging of the Pericardium

Imaging of the pericardium requires understanding of anatomy and the normal and abnormal physiology of the pericardium. MR imaging is well-suited for answering clinical questions regarding suspected pericardial disease. Pericardial diseases that may be effectively imaged with MR imaging include pericarditis, pericardial effusion, cardiac-pericardial tamponade, constrictive pericarditis, pericardial cysts, absence of the pericardium, and pericardial masses. Although benign and malignant primary tumors of the pericardium may be occasionally encountered, the most common etiology of a pericardial mass is metastatic disease.

A Hydrophobic Gel Phantom for Study of Thermochemical Ablation: Initial Results Using a Weak Acid and Weak Base

PURPOSE To develop a model for study of exothermic chemical reactions potentially useful for tissue ablation. MATERIALS AND METHODS Seven gelatins ranging from 0.5% to 30% wt/vol with and without 15% or 30% caps and several commercial gels were evaluated. Baseline temperature measurements were taken. Acetic acid and ammonium hydroxide were sequentially injected over periods of 10-15 seconds in 1-mL aliquots, forming a discrete aqueous reaction chamber. Congo red pH indicator was included to assess the reaction. A thermocouple allowed data collection at completion of injection and every 15 seconds for 5 minutes. Injections were performed in triplicate, and average temperatures for each time point were reported. RESULTS Gelatins fractured or refluxed even at the lowest concentrations tested. Most commercial gels proved too viscous and likewise led to reflux along the needle tract. A mineral oil-based gel was selected because of its ability to form a chamber without reflux or fracture and its clear colorless character, hydrophobic nature, chemical stability, viscosity, specific gravity, and cost. Temperatures during the first 60 seconds of the neutralization reaction showed an immediate increase that correlated well with concentration. CONCLUSIONS The oil gel phantom is a safe, useful, readily available, inexpensive model to study mixing behaviors and maximum heating potentials for reactions that may prove useful in thermochemical tissue ablation for oncologic interventions. Measurable temperature changes occurred even at the lowest concentrations, and higher concentrations produced a greater release of heat energy.

Cardiac MR Imaging of Nonischemic Cardiomyopathies

Cardiomyopathies, diseases of the myocardium associated with cardiac dysfunction, include hypertrophic, restrictive, and dilated forms and rare entities, such as arrhythmogenic right ventricular dysplasia, ventricular noncompaction, and apical ballooning syndrome. Many have similar presentations, but the underlying condition determines prognoses and treatment. Cardiac MR imaging plays a role in characterizing the range of entities and is crucial for evaluation and management. In addition, delayed enhanced imaging can allow differentiation among the forms of cardiomyopathy and offer prognostic information. As the speed and technical ease of cardiac imaging improve, MR imaging will assume an increasing role in the care of patients who have cardiomyopathy.

In Vitro Thermal Profile Suitability Assessment of Acids and Bases for Thermochemical Ablation: Underlying Principles

PURPOSE To measure and compare temperature changes in a recently developed gel phantom for thermochemical ablation as a function of reagent strength and concentration with several acids and bases. MATERIALS AND METHODS Aliquots (0.5-1 mL) of hydrochloric acid or acetic acid and sodium hydroxide or aqueous ammonia were injected for 5 seconds into a hydrophobic gel phantom. Stepwise increments in concentration were used to survey the temperature changes caused by these reactions. Injections were performed in triplicate, measured with a thermocouple probe, and plotted as functions of concentration and time. RESULTS Maximum temperatures were reached almost immediately in all cases, reaching 75 degrees C-110 degrees C at the higher concentrations. The highest temperatures were seen with hydrochloric acid and either base. More concentrated solutions of sodium hydroxide tended to mix incompletely, such that experiments at 9 M and higher were difficult to perform consistently. CONCLUSIONS Higher concentrations for any reagent resulted in higher temperatures. Stronger acid and base combinations resulted in higher temperatures versus weak acid and base combinations at the same concentration. Maximum temperatures obtained are in a range known to cause tissue coagulation, and all combinations tested therefore appeared suitable for further investigation in thermochemical ablation. Because of the loss of the reaction chamber shape at higher concentrations of stronger agents, the phantom does not allow complete characterization under these circumstances. Adequate mixing of reagents to maximize heating potential and avoid systemic exposure to unreacted acid and base must be addressed if the method is to be safely employed in tissues. In addition, understanding factors that control lesion shape in a more realistic tissue model will be critical.

Successful Coil Embolization of Mediastinal Bronchial Artery Aneurysm

Editor: Mediastinal bronchial artery aneurysms are uncommon, with fewer than 40 published case reports (1,2). Presentation is varied, ranging from an incidental imaging finding to hemomediastinum and shock resulting from aneurysm rupture. Rupture can occur with a bronchial artery aneurysm of any size, so prompt treatment is indicated upon diagnosis. Current treatment options include surgical resection, transarterial embolization, and stent-grafting with subsequent percutaneous embolization of feeding vessels. We report a case of an asymptomatic 53-year-old man in whom a mediastinal bronchial artery aneurysm was incidentally discovered on computed tomography (CT) of the chest. The aneurysm and its branches were successfully coil-embolized via a transarterial approach. The case description is as follows. A 53-year-old man underwent a screening CT examination of the chest in the context of a testicular mass that was ultimately deemed benign. The CT scan revealed a 12-mmdiameter aneurysm arising from a 1–2-mm neck from the aorta (Figure, a–c). A short bronchial artery trunk emanated from the superior aspect of the aneurysm sac before bifurcating into left and right bronchial arteries. The patient was asymptomatic with no history of pulmonary infection or trauma or CT evidence of atherosclerosis. Of note, the patient’s medical history was significant for non-Hodgkin lymphoma, which had been successfully treated with stem cell transplantation 10 years earlier. He received no radiation therapy. After written informed consent was obtained, the patient underwent treatment of the bronchial artery aneurysm by coil embolization. A bronchial artery angiogram was obtained from a right common femoral artery punctured with an 18-gauge, 7-cm needle (Cook, Bloomington, Indiana). A 6-F vascular sheath (Terumo, Tokyo, Japan) was inserted into the artery over a Bentsen guide wire (Cook). A 5-F Sos catheter (Angiodynamics, Queensbury, New York) was used to select the bronchial artery and an angiogram was obtained with use of Omnipaque contrast medium (Amersham, Princeton, New Jersey; Figure). A bronchial artery aneurysm arising from the trunk was identified. The spinal artery did not arise from the bronchial artery or its branches.

Clinical Outcomes After Endovascular Treatment of Superficial Femoral Disease in Patients With Disabling Claudication and Critical Limb Ischemia: Midterm Analysis

We present the midterm clinical outcomes and predictors of balloon angioplasty and stent placement in atherosclerotic femoropopliteal (FP) arterial disease. Between January 2002 and August 2006, 155 patients (men = 56%; 71.4 ± 10.5 years) underwent 171 FP angioplasty or stent for claudication (n = 82, 54%) or critical limb ischemia ([CLI] n = 70, 46%). Follow-up was obtained through September 30, 2009. The average follow-up was 3.25 ± 1.73 years. In claudicants versus CLI, the 12-month patency for TransAtlantic InterSociety Consensus II (TASC II) classification (TASC A/B) was 93% versus 80%, respectively, and TASC C/D 83% versus 80%. At 3 years, TASC A/B was 82% versus 80%, respectively, and TASC C/D was 56% versus 80%, respectively. The predictor of clinical failure in claudicants was chronic renal insufficiency (CRI) and in CLI, the predictor of amputation was hyperlipidemia.

Use of Kissing Embolic Protection Devices in the Treatment of Early Bifurcation Renal Artery Stenosis: A Case Report

Renal artery stenosis (RAS) is a progressive disease that may cause hypertension and chronic renal insufficiency. Percutaneous renal artery angioplasty with stent placement is a well-recognized treatment for atherosclerotic RAS. It can infrequently involve the bifurcation, and treatment of this stenosis has been described using bare metal and drug-eluting stents deployed simultaneously in a kissing fashion. Atheroembolism is believed to be caused by the release of microscopic plaque fragments and cholesterol crystals from the RAS or atherosclerotic aorta. Herein, the authors describe the use of a kissing embolic protection device technique during renal artery stent placement.

Dual Energy: CTA Runoff

A unique function of the SOMATOM Definition Dual Source CT system is its capacity to operate each x-ray tube at different kV and mA settings. While dual-energy CT was originally developed and evaluated 20 years ago, technical limitations of the CT scanners and post processing software at that time prevented the development of routine clinical applications.1