[Role of isotopic imaging in intensive care]

The real place of isotopic imaging in intensive care patients remains still unclear. This review aimed to consider the indications of isotopic imaging for improved diagnosis and therapy and to specify its place among the other techniques of exploration. Pulmonary perfusion and ventilation scintigraphies are valuable for the diagnosis of pulmonary embolism (PE). A "high probability" scintigraphy of the lungs ascertains the diagnosis of PE and allows to start a specific treatment without requiring a pulmonary angiography. This is not the case in the presence of a history of previous PE or if the arguments for a PE are only weak. A normal lung scintigraphy eliminates the diagnosis of a clinically significant PE all the more as an exploration of good quality of the lower limb veins remains negative. In the opposite a "non diagnostic" scintigraphy justifies a pulmonary angiography in intensive care patients. The diagnosis of myocardial contusion is made uneasy as the clinical symptoms, the ECG, the cardiac enzymes and the chest X-ray are only of limited value. Isotopic explorations of the heart could provide additional valuable data or be an alternative for 2 D echocardiography. The comparison of CPK-MB concentrations with a myocardial scintigraphy using thallium 201 is given as being very reliable, with positive and negative predictive values higher than 80%. An exploration restricted to the cardiac ejection fractions is only of limited value. In the future, an improvement will perhaps be obtained with tracers such as MIBI labelled with technetium 99m, which allow the simultaneous assessment of myocardial perfusion and the ventricular ejection fractions as well. The localisation of centres of infection, especially when intra-abdominal, remains difficult in intensive care patients. Isotopic imaging, especially the scintigraphies with labelled polynuclears, could allow in combination with conventional imaging techniques (computed tomography and 2 D echocardiography) to prevent from errors in diagnosis. An array of arguments is essential for ascertaining the presence of an abscess. Scintigraphies with leucocytes labelled with indium 111 or technetium 99m are qualified as having a sensitivity and a specificity greater than 90%. The conventional techniques of measurement of the cerebral blood flow (CBF) using xenon 133 require a special equipment or are invasive. Other cerebral tracers, such as cyclic amines (HMPAO) labelled with technetium 99m and administrable by i.v. route, allow the use of a standard tomo-gamma camera, and could be of help in various pathological conditions.(ABSTRACT TRUNCATED AT 400 WORDS)