Magnetic resonance angiography imaging of pulmonary embolism using agents with blood pool properties as an alternative to computed tomography to avoid radiation exposure.

PURPOSE: To evaluate the feasibility and accuracy of a combined magnetic resonance angiography (MRA) - magnetic resonance venography (MRV) protocol using contrast agents with blood pool properties, gadofosveset trisodium and gadobenate dimeglumine, in the evaluation of pulmonary embolus (PE) and deep venous thrombosis (DVT) as compared to the standard clinical reference imaging modalities; computed tomography pulmonary angiography (CTPA) and color-coded Duplex ultrasound (DUS). MATERIALS AND METHODS: This prospective clinical study recruited patients presenting to the emergency department with clinical suspicion for PE and scheduled for a clinically indicated CTPA. We performed both MRA of the chest for the evaluation of PE as well as MRV of the pelvis and thighs to evaluate for DVT using a single contrast injection. MRA-MRV data was compared to the clinical reference standard CTPA and DUS, respectively. RESULTS: A total of 40 patients were recruited. The results on a per-patient basis comparing MRA to CTPA for pulmonary embolus yielded 100% sensitivity and 97% specificity. There was a small subset of patients that underwent clinical DUS to evaluate for DVT, which demonstrated a sensitivity and specificity of 100% for MRV. CONCLUSIONS: This single-center, preliminary study using contrast agents with blood pool properties to perform a relatively rapid combined MRA-MRV exam to image for PE and above knee DVT shows potential as an alternative imaging choice to CTPA. Further large-scale, multicentre studies are warranted.

Subclinical myocardial disease by cardiac magnetic resonance imaging and spectroscopy in healthy HIV/Hepatitis C virus-coinfected persons.

Objective The contribution of hepatitis C virus (HCV) infection to the risk of heart failure in human immunodeficiency virus (HIV)-coinfected persons is unknown. The objective was to characterize cardiac function and morphology in HIV-treated coinfected persons. Methods In a cross-sectional study, HIV-infected patients virologically suppressed on antiretroviral therapy without known cardiovascular disease or diabetes mellitus underwent cardiac magnetic resonance imaging and spectroscopy for measures of cardiac function, myocardial fibrosis, and steatosis. Results The study included 18 male patients with a median age of 44 years. Of these, 10 had untreated HCV coinfection and eight had HIV monoinfection. Global systolic and diastolic function in the cohort were normal, and median myocardial fat content was 0.48% (interquartile range 0.35-1.54). Left ventricular (LV) mass index and LV mass/volume ratio were significantly greater in the HIV/HCV-coinfected group compared with the HIV-monoinfected group. In the HIV-monoinfected group, there was more myocardial fibrosis as measured by extracellular volume fraction. Conclusions There were differences between HIV/HCV-coinfected and HIV-monoinfected patients in cardiac structure and morphology. Larger studies are needed to examine whether HIV and HCV independently contribute to mechanisms of heart failure.

The dependence of radiofrequency induced pacemaker lead tip heating on the electrical conductivity of the medium at the lead tip.

Radiofrequency induced pacemaker lead tip heating is one of the main reasons magnetic resonance imaging (MRI) is contraindicated for patients with pacemakers. The objective of this work was to evaluate the dependence of pacemaker lead tip heating during MRI scanning on the electrical conductivity of the medium surrounding the pacemaker lead tip. The effect of conductivity was measured using hydroxyethyl cellulose, polyacrylic acid, and saline with conductivities ranging from 0 to 3 S/m which spans the range of human tissue conductivity. The maximum lead tip heating observed in polyacrylic acid was 50.4 °C at 0.28 S/m, in hydroxyethyl cellulose the maximum was 36.8 °C at 0.52 S/m, and in saline the maximum was 12.5 °C at 0.51 S/m. The maximum power transfer theorem was used to calculate the relative power deposited in the solution based on the characteristic impedance of the pacemaker lead and test solution impedance. The results demonstrate a strong correlation between the relative power deposited and pacemaker lead tip heating for hydroxyethyl cellulose and saline solutions. Maximum power deposition occurred when the impedance of the solution matched the pacemaker lead impedance. Pacemaker lead tip heating is dependent upon the electrical conductivity of the solution at the lead tip and should be considered when planning in vitro gel or saline experiments.