Emily Ward

Peripheral arterial disease in a symptomatic diabetic population: prospective comparison of rapid unenhanced MR angiography (MRA) with contrast-enhanced MRA.

OBJECTIVE The joint guidelines of the American College of Cardiology and American Heart Association support the use of contrast-enhanced MR angiography (CEMRA) to diagnose the location and degree of stenosis in patients with known or suspected peripheral arterial disease (PAD). The high prevalence of chronic renal impairment in diabetic patients with PAD and the need for high doses of gadolinium-based contrast agents place them at risk for nephrogenic systemic fibrosis. The purpose of our study was to evaluate the accuracy of the rapid technique of quiescent-interval single-shot (QISS) unenhanced MR angiography (MRA) compared with CEMRA for the diagnosis in diabetic patients referred with symptomatic chronic PAD. SUBJECTS AND METHODS This prospective two-center study evaluated 25 consecutive diabetic patients with documented or suspected symptomatic PAD. Both centers used identical imaging protocols. Images were independently analyzed by two radiologists. A subgroup analysis was performed of patients who were also assessed with digital subtraction angiography (DSA) as part of the standard-of-care protocol before revascularization. RESULTS For this study, 775 segments were analyzed. On a per-segment basis, the mean values of the diagnostic accuracy of unenhanced MRA compared with reference CEMRA for two reviewers, reviewers 1 and 2, were as follows: sensitivity, 87.4% and 92.1%; specificity, 96.8% and 96.0%; positive predictive value, 90.8% and 94.0%; and negative predictive value, 95.5% and 94.6%. Substantial agreement was found when overall DSA results were compared with QISS unenhanced MRA (κ = 0.68) and CEMRA (κ = 0.63) in the subgroup of patients who also underwent DSA. There was almost perfect agreement between the two readers for stenosis scores, with Cohens kappa values being greater than 0.80 for both MRA techniques. CONCLUSION The results of our study indicate that QISS unenhanced MRA is an accurate noncontrast alternative to CEMRA for showing clinically significant arterial disease in patients with diabetes with symptomatic PAD.

Improved characterization of popliteal aneurysms using gadofosveset-enhanced equilibrium phase magnetic resonance angiography

Although standard magnetic resonance angiography (MRA) has many advantages in the evaluation of peripheral artery disease, it has poorer spatial resolution compared with computed tomographic angiography and digital subtraction angiography. The MRA blood pool contrast agents have an extended half-life. By allowing longer imaging times, MRA enables the acquisition of high-resolution images as well as providing simultaneous visualization of both arteries and veins. Two cases of popliteal artery aneurysm are presented, in which MRA with a blood pool contrast agent provided critical clues to the correct diagnosis: a traumatic pseudoaneurysm of the popliteal artery caused by a femoral osteochondroma and a large fusiform popliteal aneurysm compressing the adjacent popliteal vein, causing venous congestion and leg pain.

Inline directionally independent peak velocity evaluation reduces error in peak antegrade velocity estimation in patients referred for cardiac valvular assessment.

OBJECTIVE The purpose of this article is to evaluate the utility of a tool in quantifying the peak antegrade velocity when assessing patients with cardiac valvular pathology. MATERIALS AND METHODS Directionally independent peak velocity evaluation (MaxVelocity, Siemens Healthcare) phase-contrast cardiac MRI was performed for 44 patients referred to our institution with a diagnosis or concern for aortic valvular disease or undergoing imaging for thoracic aortic aneurysm. In addition, standard through-plane phase-contrast MR angiography at the level of the aortic valve was performed. The MaxVelocity technique provides a simple tool to extract the magnitude of the peak velocity, independently of its direction, from phase-contrast imaging with velocity encoding. Recent echocardiography (within 1 month) and assessment of peak forward velocity at the level of the aortic valve were required for inclusion in the study. RESULTS The MaxVelocity technique shows significantly lower error in estimating peak antegrade velocity at the level of the aortic valve than does standard unidirectional through-plane phase-contrast MRI, using transthoracic echocardiography as the reference noninvasive imaging method. CONCLUSION Relative to standard through-plane imaging, MaxVelocity more closely approximates echocardiography for noninvasive assessment of peak antegrade velocity. Improved accuracy is critical for surgical decision making in patients with aortic valvular disease. Therefore, MaxVelocity provides an easy approach to quantify peak velocity as part of a routine clinical MRI protocol.

Answer to Case of the Month #149: Alveolar Soft-Part Sarcoma

A 39-year-old man presented to the emergency department with a 2-week history of a dry cough that was unresponsive to a course of antibiotics. He also suffered from fatigue and believed he had lost some weight over the past 3 months. He had no other specific symptoms and had no significant past medical or surgical history. He was on no medications and was a nonsmoker. On examination, he was apyrexial and his general physical examination was normal apart from the presence of a soft-tissue mass behind his left knee. A full blood count as well as routine serum biochemical analysis was normal. A chest radiograph was performed that showed multiple lung metastases (Figure 1). A magnetic resonance image (MRI) of the left knee was performed. Figure 2A is a sagittal T1-weighted MRI image showing a 5 7 cm soft-tissue mass lying posterior to the knee. The mass involved the posterior muscle compartment. There was no osseous involvement and the femoral artery and vein were separate from it. An unusual feature of the mass was the presence of multiple large vessels present throughout the mass. Figure 2B is a transverse T1-weighted image again showing the mass involving the posterior muscle compartment. Figure 2C is a transverse gadolinium-enhanced image showing marked enhancement of the mass as well as again showing the presence of multiple vessels within the mass. Figure 2D is a T2-weighted image of the mass. The differential diagnosis at this stage included both a large arteriovenous malformation, as well as an alveolar soft-part sarcoma (ASPS). The presence of multiple lung metastases

Answer to Case of the Month #145: Lemierre's Syndrome

A 30-year-old woman presented to the emergency department with a 4-day history of pleuritic chest pain and dyspnoea and a 1-day history of haemoptysis. She had been well until 2 weeks ago when she attended her general practitioner with headaches and a sore throat and was treated with anti-inflammatory medication and a course of antibiotics with improvement of symptoms. On examination, the patient was tachypnoeic with a respiratory rate of 22 breaths per minute and had a pyrexia with a temperature of 38.3 C. Physical examination was otherwise unremarkable. Laboratory investigation showed a leucocytosis with a white cell count of 14 10/L and an increased C-reactive protein of 109 mg/L. The patient went on to have a contrast-enhanced computed tomography of her neck and thorax (Figures 1e3).