[Brain MRI associated with chronic hepatic failure and hypermanganism]. / Hypersignal T1 bipallidal dans le cadre d'une cirrhose avec hypermanganésémie.

INTRODUCTION: Hypermanganism is primarily linked to inhalation exposure. Several observations of exogenous manganese poisoning have been reported associating neuropsychiatric symptoms, parkinsonian syndrome and hyperintensities of the two pallida on T1 weighted sequences on brain MRI. Recently, similar neurological and radiological signs have been described without exogenous exposure to manganese but in the framework of endogenous poisoning particularly in chronic hepatic failure. CASE REPORT: We report the case of a 41-year-old HIV-positive and HVC-positive man who presented psychomotor impairment associated with bipallidal T1 hyperintensities on the brain MRI. The diagnosis of a hypermanganesemia was made on blood samples. We present a literature review on exogenous and endogenous hypermanganesemia and discuss differential diagnosis in the radiological setting of bipallidal T1 hyperintensities. CONCLUSION: Bipallidal T1 hyperintensities on brain MRI may suggest hypermanganism even in the clinical setting of a non-specific neurological disorder such as psychomotor impairment.

[Value of relative cerebral blood volume measurement using perfusion MRI in glioma management]. / Intérêt de la mesure du volume sanguin régional cérébral relatif par IRM de perfusion dans la prise en charge des gliomes.

INTRODUCTION: Neoangiogenesis is a critical feature that can differentiate high-grade from low-grade glioma. Conventional MR imaging does not assess this histological feature accurately. The goal of this study was to evaluate the gain in relative cerebral blood volume measurement using perfusion MRI in the management of cerebral gliomas. MATERIALS AND METHODS: Between 1998 and 2001, 32 histologically proven glial tumors were assessed by perfusion MRI using echoplanar imaging (EPI) and gradient-echo techniques. Relative cerebral blood volume (rCBV) was measured in all patients and compared to histological data. RESULTS: rCBV values were significantly correlated to histological grading in all 32 patients (P<0.001). Mean rCBV values were 8.74 (+/-3.79) for glioblastomas, 7.37 (+/-2.83) for anaplastic gliomas and 0.84 (+/-0.61) for low-grade gliomas. Mean rCBV values were significantly different between low- and high-grade gliomas, making it possible to determine a threshold (2.5-3) that can separate these two types of lesion. In determining the histological grading, rCBV was shown to be significantly more accurate than conventional MRI (P<0.005). CONCLUSION: Perfusion MRI using the EPI technique reliably assesses tumoral neoangiogenesis in gliomas preoperatively. The specificity and sensitivity of this technique make this radiological modality a valuable tool in the assessment of cerebral gliomas.

[Functional MR imaging and oligodendrogliomas]. / IRM fonctionnelle et oligodendrogliomes.

The localization of functional areas obtained from functional MRI (fMRI) is useful for patients suffering from tumors contiguous to eloquent brain areas. fRMI is an efficient tool in the strategy of treatment of low grade oligodendroglioamas in the rolandic area in intact or slightly impaired patients. It can be used preoperatively to assess motor functional areas. Indeed there is a good correlation for motor cortex lesions when using comparison between fMRI and intraoperative findings. Direct integration of fMRI data into neuronavigation enables to better visualize and preserve eloquent brain areas. One must be aware of fMRI limits. It is still often used with the control of direct cortical stimulations.

[Risk from prenatal exposure to ionizing radiation]. / Risques liés à l'exposition d'une grossesse aux rayonnements ionisants.

Exposure to ionizing radiation during pregnancy always is a worrisome event. Knowledge of teratogenic and carcinogenic mechanisms based on reliable scientific data (ICRP 84) allows appropriate management of patients following exposure to ionizing radiation. Radiation exposure in the setting of diagnostic imaging studies is not associated with an increased risk of fetal malformation; however, the risk of childhood malignancy is minimally increased. This information must be provided to parents so they may reach an informed decision with regards to the outcome of the pregnancy. The analysis of the quality and quantity of exposure should be limited to imaging examinations where the abdomen was exposed. Management will be based on the type of exposure. Guidelines are provided for various exposure situations and all radiologists must be able to manage such situations.

Merkel cell tumor: report of two cases and review of the literature.

The "Merkel cell carcinoma" is a rare tumor usually occuring in the sun-exposed skin. Its poor prognosis is explained by a high rate of metastasis (one third of the patients at the initial presentation) and a high post-operative recurrence rate. Descriptions of the imaging features of this type of tumor are rare. We present two cases of Merkel cell carcinoma localized to the head region. In the first patient, the lesion involved the soft tissues of the scalp with secondary invasion of the skull and meninges. The second patient had a metastasis to the parietal lobe.

[Dose reduction at abdominal CT imaging: reduced tension (kV) or reduced intensity (mAs)?]. / Diminuer la dose en tomodensitométrie abdominale: baisser la tension (kV) ou la charge (mAs)?

PURPOSE: To compare low-dose protocols using either reduction of the tension (kV) or reduction of the intensity (mAs) at abdominal CT imaging, with reference to image quality. MATERIALS AND METHODS: Fifty adult patients, weighing less than 55 kg, were prospectively included among patients referred for abdominal CT examination when the protocol required a noncontrast study. The images obtained with the standard protocol (120 kV, 200 mAs) were compared to 4 additional test images, two obtained with low intensity (120 kV, 100 mAs) and two obtained with low tension (100 kV, 200 mAs). Two senior radiologists blindly reviewed all images using both subjective (itemized list) and objective criteria (measure of standard deviation for density measurements obtained of the liver parenchyma). RESULTS: The image quality of the low kV protocol was better than the image quality of the low mAs protocol for both subjective and objective criteria. CONCLUSION: For abdominal CT imaging of standard to thin adult patients or children, dose reduction using a low kV protocol may be an alternative to a protocol using a low intensity. This can easily be implemented and can be used in conjunction with a dose reducing software.

[Intradiploic parietal meningoencephalocele]. / Méningoencéphalocèle intradiploïque pariétale.

Intradiploic meningoencephalocele is rarely found in adulthood. It is thought to be postraumatic and must be differenciated from congenital encephalocele. Imaging findings, particularly with Magnetic Resonance Imaging, are useful in determining the various linings and contents of this intradiploic defect.

[Diagnosis of periventricular ependymal enhancement in MRI in adults]. / Diagnostic d'un rehaussement épendymaire et périventriculaire en irm chez l'adulte.

Periventricular enhancement in adults at MRI is a significant finding since it often indicates the presence of an underlying disease requiring prompt medical attention. From a review of patients with periventricular enhancement, the main imaging features based on the underlying infectious or tumoral etiology will be described. The presented differential diagnosis is based on the immune status of the patient, type of enhancement, and response to a trial therapy. In immunocompromised patients, the main considerations are lymphoma and viral ependymitis. The pattern of enhancement is important. The presence of thin linear enhancement suggests a viral etiology (cytomegalovirus or varicella-zoster virus) that can be confirmed at CSF evaluation whereas the presence of nodular enhancement suggests a diagnosis of primary CNS lymphoma that can be confirmed by the presence of lymphomatous cells in the CSF or, more frequently, at stereotactic surgical biopsy performed after failure of response to anti-toxoplasmosis treatment. The presence of band enhancement is less specific and can be seen with viral, lymphomatous and even tuberculous involvement. In immunocompetent patients, a clinical context of infection will suggest bacterial or tuberculous ventriculitis and the presence of cystic lesions will suggest cysticercosis; in the absence of constitutional symptoms, the presence of nodular enhancement will suggest a tumoral process (lymphoma, ependymoma, germ cell tumor, or metastases). Rarely, linear enhancement will be due to sarcoidosis or Whipple's disease.

Functional MR imaging in assessment of language dominance in epileptic patients.

The value of functional MR Imaging (fMRI) in assessing language lateralization in epileptic patients candidate for surgical treatment is increasingly recognized. However few data are available for left-handed patients. Moreover determining factors for atypical dominance in patients investigated with contemporary imaging have not been reported. We studied 20 patients (14 males, 6 females; 9 right handed, 11 left handed) aged from 9 to 48 years, investigated for intractable partial epilepsy. Epileptic focus location was temporal in 14 cases, extratemporal in 6, and lateralized in the left hemisphere in 11/20. Hemispheric dominance for language was evaluated by both Wada test and fMRI using a silent word generation paradigm in all patients. Furthermore, a postictal speech test was performed in 15 patients. An fMRI language lateralization index was calculated from the number of activated pixels (Student's t test, P < 0.0001) in the right and left hemispheres. The Wada test showed a right hemispheric dominance in 8 patients (6 were left handed and 2 right handed) and a left hemispheric dominance in 12 patients (5 were left handed and 7 right handed). These results were concordant with clinical postictal examination in 11/15 patients (73%). Clinical status did not allow a conclusion about hemispheric dominance for the remaining 4 patients. FMRI was concordant with the Wada test in 19/20 cases. For one left-handed patient, fMRI showed bilateral activation, whereas the Wada test demonstrated a right hemispheric dominance. Right language lateralization was significantly correlated with left lateralized epilepsy (P < 0.05) but was not correlated with age at epilepsy onset, early brain injury (before 6 years), and lobar localization of epileptogenic focus. However the lack of a significant relationship between these factors and atypical language lateralization may be related to the small sample size.

[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.

Sensorimotor cortical activity in patients with complete spinal cord injury: a functional magnetic resonance imaging study.

Residual activation of the cortex was investigated in nine patients with complete spinal cord injury between T6 and L1 by functional magnetic resonance imaging (fMRI). Brain activations were recorded under four conditions: (1) a patient attempting to move his toes with flexion-extension, (2) a patient imagining the same movement, (3) passive proprio-somesthesic stimulation of the big toes without visual control, and (4) passive proprio-somesthesic stimulation of the big toes with visual control by the patient. Passive proprio-somesthesic stimulation of the toes generated activation posterior to the central sulcus in the three patients who also showed a somesthesic evoked potential response to somesthesic stimulation. When performed under visual control, activations were observed in two more patients. In all patients, activations were found in the cortical areas involved in motor control (i.e., primary sensorimotor cortex, premotor regions and supplementary motor area [SMA]) during attempts to move or mental imagery of these tasks. It is concluded that even several years after injury with some local cortical reorganization, activation of lower limb cortical networks can be generated either by the attempt to move, the mental evocation of the action, or the visual feedback of a passive proprio-somesthesic stimulation.