[Vade-mecum of helical CT scanning: estimation of doses, choice of parameters]. / Vade-mecum du scanner hélicoïdal: estimation des doses, choix des paramètres.

Implementation of EURATOM directive 97/43 requires increased scrutiny over the use CT imaging. All CT imaging centers will be required to perform routine QA procedures including measurements of exposure related to frequently performed types of CT examination. CT technologists and radiologists will be required to try and identify ways of decreasing patient exposure for CT examinations while insuring acquisition of diagnostic studies. In turn, this assumes understanding of the exposure parameters displayed on the CT images. Based on this, radiologists will be in a position to compare exposure parameters in their practice to national standards and perform necessary adjustments. Also, it should become possible to more adequately estimate patient exposure related to specific CT examinations.

[Thrombosis of the cerebral veins. X-ray computed tomography and MRI imaging. 11 cases]. / Thrombose des veines cérébrales. Imagerie TDM et IRM. 11 cas.

11 cases of cerebral venous thrombosis in adults are reported. Main clinical signs are: intracranial hypertension (headache, nausea, papilledema in 7 cases, loss of consciousness in 6 cases, neurological deficit in 6 cases, seizure in 4 cases. 1 patient is dead, who did not receive heparin treatment. Delay before diagnosis is between 2 and 20 days, and is shortened when arteriography or MRI are available and prescribed. At least one (or several) CT examination was performed in 10 patients. Direct signs of thrombosis are uneasily detected without contrast injection, seen here in 4 cases. Empty delta sign is observed in 7 patients, lately in 4 cases, and once only afterwards. Cerebral infarction is visualized in 7 cases over 10. Its features frequently seem evocative for cerebral venous thrombosis: triangularin 4 cases or nodular shape in 3 cases with hemorragic infarct in 7 cases, with bilateral topography in 6 cases, in frontal or central areas in 7 cases. 6 patients had a MRI examination. All cerebral infarctions appeared haemorragical, even at early stages. During subacute period, venous thrombosis is constantly and easily detected by the mean of methemoglobin high signal intensity on T1 weighted images. The prediagnosis delay is short, without necessity of arteriography. MRI should take the place of CT and arteriography in investigation of a clinically suspected cerebral venous thrombosis.

[Radiological aspects of acoustic neurinoma]. / Les aspects radiologiques du neurinome du VIII.

For a long time CT constituted the technique of choice for the investigation and pretreatment staging of acoustic neuroma. It is sometimes inadequate especially for defining the extra-axial site of a tumour or for identifying small lesions. Today, any case of suspected acoustic neuroma should undergo first-line MR studies. MR identifies almost all extra-axial lesions, clearly visualises small lesions and provides a satisfactory pretreatment staging in the majority of cases, acoustic neuroma presents a signal intensity identical to or lower than that of the brainstem with a high intensity signal on T2-weighted SE sequences and post-gadolinium T1-weighted SE sequences, generally with a mixed intra- and extra-meatal location and eccentric in relation to the anterior border of the porus.

[MRI techniques for the study of the temporal lobe and its environment]. / Techniques IRM d'exploration du temporal et de son environnement.

The MR study of the temporal lobe and its environment requires a good knowledge of the anatomy in order to select the views adapted to the disease investigated. The authors propose a series of protocols according to the region examined. An understanding of the principles of MR sequences is also essential to avoid the problems of investigation associated with this complex anatomical region. The principal sequences are reviewed together with their advantages and disadvantages.