Evaluation of volume vascularization index and flow index: a phantom study.

OBJECTIVES: Three-dimensional (3D) power Doppler ultrasonography provides indices to quantify moving blood within a volume of interest (e.g. ovary, endometrium, tumor or placenta). The purpose of this study was to determine the influence of ultrasound instrument settings on vascularization index (VI) and flow index (FI) at different flow velocities, using a specially built flow phantom with a small tube diameter. METHODS: Blood-mimicking fluid was pumped at 10-100 mL/h through a plastic tube with a diameter of 0.65 mm within a virtual spherical volume (content 137.12 cm(3)) of a Voluson 730 Expert 3D power Doppler ultrasound instrument. VI and FI were determined at different pulse repetition frequency (PRF) settings, with minimal and maximal wall motion filter (WMF) settings. The measured VI was compared with the actual VI. RESULTS: The ability to measure VI and FI at different flow velocities was highly dependent on the PRF and WMF settings. In our experimental set-up, using a PRF of 0.3 kHz, flow velocities of about 2 cm/s and higher could be registered. Measured VI was overestimated up to 44 times relative to actual VI. CONCLUSIONS: Our main finding in a laboratory set-up was a considerable overestimation of moving blood volume using 3D power Doppler ultrasound in a single small tube. The degree of overestimation depends on the spatial resolution and on the settings of the ultrasound instrument. When small vessels are involved in a clinical setting, interpretation of VI should take this overestimation of moving blood volume into account.

[Hypertensive encephalopathy: does not only occur at high blood pressure]. / Hypertensieve encefalopathie: niet alleen bij zeer hoge bloeddrukwaarden.

A 45-year-old man presented with severe hypertension, headache, cortical blindness, and a depressed level of consciousness. A second patient, a 33-year-old woman, was admitted with pre-eclampsia. She developed lethargy, headache, bilateral extensor plantar responses, and seizures. The third patient, a 62-year-old man, presented with acute renal failure due to necrotising vasculitis and glomerulonephritis. Five days after treatment with immunosuppressive drugs had been initiated, he developed headache, confusion, seizures, and cortical blindness. Hypertensive encephalopathy is characterised by headache, vomiting, disturbances in cognition and level of consciousness, visual abnormalities, and seizures. Imaging studies often demonstrate oedema of the white matter in the posterior parietal and occipital areas of the brain. This so-called reversible posterior leucoencephalopathy syndrome is well known in patients with severe hypertension, but it is also associated with immunosuppressive drug use and renal failure. It can be recognised by its fairly characteristic clinical features (different combinations of headache, vomiting, changes in cognition and level of consciousness, seizures, muscle weakness, and visual symptoms) and by its specific imaging findings. Treatment consists of reducing the blood pressure and reducing or discontinuing the use of immunosuppressive drugs. If the treatment is started promptly, symptoms and imaging abnormalities are usually reversible.