Magnetic resonance imaging-derived arterial peak flow in peripheral arterial disease: towards a standardized measurement.

OBJECTIVE: To determine the best location to measure the arterial peak flow (APF) in patients with peripheral arterial disease in order to facilitate clinical standardization. METHODS: Two hundred and fifty-nine patients with varying degrees of peripheral artery disease (PAD) and 48 patients without PAD were included. All patients underwent magnetic resonance phase-contrast imaging of the common femoral artery (CFA), superficial femoral artery (SFA), and popliteal artery (PA). APF values of patients with PAD were compared with patients with no PAD. The discriminative ability to identify PAD was evaluated by means of receiver-operator characteristic curves and the corresponding areas under the curve (AUC). RESULTS: Mean APF values in patients with PAD were reduced by 42%, 55% and 59% compared with non-PAD patients for the CFA, SFA, and PA, respectively (p < .01). The AUC's were 0.84, 0.92, and 0.93 for the CFA, SFA, and PA, respectively. CONCLUSION: The APF measured at the level of the PA shows the largest differences between patients with PAD and patients with no PAD and the best discriminative ability compared with the APF acquired in the CFA or SFA. The PA seems to be the most suitable level for standardized flow measurements in patients with PAD in order to obtain relevant functional information about the vascular status.

Cardiac cine MRI: comparison of 1.5 T, non-enhanced 3.0 T and blood pool enhanced 3.0 T imaging.

INTRODUCTION: Cardiac cine imaging using balanced steady state free precession sequences (bSSFP) suffers from artefacts at 3.0 T. We compared bSSFP cardiac cine imaging at 1.5 T with gradient echo imaging at 3.0 T with and without a blood pool contrast agent. MATERIALS AND METHODS: Eleven patients referred for cardiac cine imaging underwent imaging at 1.5 T and 3.0 T. At 3.0 T images were acquired before and after administration of 0.03 mmol/kg gadofosveset. Blood pool signal-to-noise ratio (SNR), temporal variations in SNR, ejection fraction and myocardial mass were compared. Subjective image quality was scored on a four-point scale. RESULTS: Blood pool SNR increased with more than 75% at 3.0 T compared to 1.5 T (p<0.001); after contrast administration at 3.0 T SNR increased with 139% (p<0.001). However, variations in blood pool SNR at 3.0 T were nearly three times as high versus those at 1.5 T in the absence of contrast medium (p<0.001); after contrast administration this was reduced to approximately a factor 1.4 (p=0.21). Saturation artefacts led to significant overestimation of ejection fraction in the absence of contrast administration (1.5 T: 44.7+/-3.1 vs. 3.0 T: 50.7+/-4.2 [p=0.04] vs. 3.0 T post contrast: 43.4+/-2.9 [p=0.55]). Subjective image quality was highest for 1.5 T (2.8+/-0.3), and lowest for non-enhanced 3.0 T (1.7+/-0.6; p=0.006). CONCLUSIONS: GRE cardiac cine imaging at 3.0 T after injection of the blood pool agent gadofosveset leads to improved objective and subjective cardiac cine image quality at 3.0 T and to the same conclusions regarding cardiac ejection fraction compared to bSSFP imaging at 1.5 T.

Effects of chronic injection of sphingomyelin-containing liposomes on lymphoid and non-lymphoid cells in the spleen. Transient suppression of marginal zone macrophages.

Mice were injected with sphingomyelin/cholesterol or phosphatidylcholine/cholesterol (PC/C) liposomes, from twice up to 10 times, on alternate days. Administration of sphingomyelin/cholesterol (SM/C) liposomes gave rise to hepato and splenomegaly, microgranulomatous infections and changes in macrophage numbers and activity in spleen and liver. Enzyme and immuno-cytochemical methods were used, to demonstrate the effect of liposomes on the lymphoid and non-lymphoid cell populations, on cryostat sections of the spleen. Routine histological staining, of sphingomyelin/cholesterol treated animals, showed no drastic changes in morphology or compartmentalization of the spleen, apart from a small enlargement (with some microgranulomas) of the red pulp. No significant differences were found in the presence or localization of T-helper, T-cytotoxic/suppressor, T-total-lymphocytes, B-total-lymphocytes, red pulp macrophages, marginal metallophils, or non-lymphoid dendritic cells. However, a transient suppression of cells expressing marginal zone macrophage surface marker ERTR-9, was observed between the second and eighth (intravenous) administration of sphingomyelin/cholesterol liposomes. Immunization of these animals with trinitrophenyl (TNP)-ficoll, a thymus-independent type-2 antigen which is specifically processed by marginal zone macrophages (MZM), showed that these cells were not suppressed with regard to their immunological function. We conclude that chronic administration of sphingomyelin liposomes influences macrophages, probably through a general phagocytic-system overload, but not permanent or damaging changes in splenic cell populations or immunological functions occur.