Quality-evaluation scheme for cerebral time-resolved 3D contrast-enhanced MR angiography techniques.

BACKGROUND AND PURPOSE: No practical tool has been reported in the literature to evaluate the quality of cerebral TR-3D-CE-MRA techniques. Our study assessed a large list of parameters used to propose a quality-evaluation scheme for TR-3D-CE-MRA. MATERIALS AND METHODS: A large list of visual and quantitative parameters used to study the quality of images was collected from the literature and evaluated in 19 healthy patients and 11 patients with arteriovenous shunts who had undergone both CENTRA keyhole TR-3D-CE-MRA at 3T and CCA. Several observers evaluated the visual parameters, such as the diagnostic confidence index, artifacts, maximum vascular signal intensity, arterial-to-venous separation, and visibility of 17 arteries and 7 veins; and quantitative parameters, such as maximum arterial SI, arteriovenous transit time, arteriovenous contrast curve, and ADW. A statistical analysis was used to determine interobserver reproducibility of the visual parameters, to calculate the sensitivity of TR-3D-CE-MRA for detecting each vessel (with CCA as standard of reference), and to compare the results of the visual and quantitative evaluations. RESULTS: Diagnostic confidence index, artifacts, arterial-to-venous separation, and 4 vessels-the PICA, ophthalmic and occipital arteries, and the ISS-demonstrated high reproducibility and sensitivity. The ADW was the most reliable dynamic quantitative parameter and was correlated with arterial-to-venous separation. CONCLUSIONS: The image quality of TR-3D-CE-MRA can be effectively evaluated with a scheme of 1 quantitative and 7 visual parameters.

[Why should vascular patients have a dietary assessment?]. / Pourquoi devons-nous évaluer l'alimentation des sujets à risque vasculaire ?

Vascular diseases are a major health problem in Western countries. Coronary heart disease (CHD), stroke, and peripheral arterial disease (PAD) share many common risk factors such as age, smoking, dyslipidemia, and diabetes. Although the dietary pattern is considered as a risk factor for CHD, the impact of dietary pattern on stroke and PAD is debated. However, new studies showed that dietary pattern could also be considered as a risk factor in stroke and PAD. Dietary pattern should be evaluated in vascular patients and new tools of dietary assessment must be developed for a better prevention of vascular disease.

[Imaging of subarachnoid hemorrhage]. / Imagerie de l'hémorragie sous-arachnoïdienne.

Even if acute subarachnoid hemorrhage (SAH) accounts for only 5% of strokes, its diagnosis is very important because its clinical consequences can be tragic. Recent technological advances in medical imaging have improved diagnostic and therapeutic management of patients with SAH. Nonenhanced CT of the head is the initial imaging modality in suspected SAH for the detection of ruptured intracranial aneurysms. Digital subtraction angiography (DSA) remains the reference exam. Multidetector row CT angiography may potentially replace DSA in the emergency setting, as it provides image data that allows evaluating aneurysmal morphology, the neck size or the visualization of vessels in the vicinity of the aneurysm. For SAH unrelated to aneurysm rupture (15% of cases), MRI and MRA can be added to the diagnostic work-up in order to exclude other differential diagnoses such as venous thrombosis or angiitis. Finally, transcranial color-coded duplex sonography, CT, or MRI are used in clinical practice in order to detect aggravating factors of SAH like hydrocephalus or vasospasm.

MR imaging features of idiopathic thoracic spinal cord herniations using combined 3D-fiesta and 2D-PC Cine techniques.

Idiopathic thoracic spinal cord herniation (TISCH) is a rare cause of surgically treatable progressive myelopathy. The authors report 3 cases of TISCH diagnosed based on conventional T1- and T2-weighted Spin-Echo (SE) MR images in one case, and T1- and T2-weighted SE images combined with 3D-FIESTA (Fast Imaging Employing Steady state Acquisition) and 2D-Phase-Contrast Cine MR imaging in 2 cases. Conventional MRI findings usually provided the diagnosis. 3D-FIESTA images confirmed it, showing the herniated cord in the ventral epidural space. Moreover, in combination with 2D-Phase Contrast cine technique, it was a sensitive method to for the detection of associated pre- or postoperative cerebrospinal fluid spaces abnormalities.

MR imaging features of spinal schwannomas and meningiomas.

Spinal schwannomas and meningiomas are mostly benign, intra-dural extramedullary tumours. We retrospectively reviewed the Magnetic Resonance Imaging (MRI) examinations of 52 spinal schwannomas and meningiomas operated on at our institution since 1998. The series included 28 schwannomas and 24 meningiomas. We compared MRI features of schwannomas and meningiomas and evaluated statistical features that would allow differentiation. Tumours with extraspinal extension were excluded. Concerning the cranio-caudal distribution, half of the cervical tumours were schwannomas, 72% of thoracic lesions were meningiomas and all lumbar tumours were schwannomas. Meningiomas were significantly located at the upper and mid thoracic levels and schwannomas in the lumbar area. On T1-weighted images, MRI signal intensity and heterogeneity were not statistically different between meningiomas and schwannomas. On T2-weighted images, the signal intensity appeared significantly hyperintense and heterogeneous for schwannomas. After Gd-DTPA, we observed a significant difference between meningiomas and schwannomas, the enhancement being intense and heterogeneous in cases of schwannomas, and moderate and homogeneous in cases of meningiomas. The last significant qualitative item was the "dural tail sign", a dural enhancement or thickening near the tumour. It was found in only 16 cases of meningiomas. A simple diagnostic test was built for schwannomas by processing a multiple agreement analysis with the 6 significant items: cranio-caudal location, T2 signal intensity, T2 signal heterogeneity, Gd-DTPA enhancement intensity and heterogeneity, and the "dural tail sign". This test allowed diagnosis of schwannomas with a sensitivity of 96.4%, a specificity of 83.3%, a positive predictive value of 87.1%, and a negative predictive value of 95.7%. In conclusion, we consider that a diagnosis of schwannoma should be made when a spinal intradural extramedullary tumour shows hyperintensity on T2W images or intense enhancement without dural tail sign; otherwise meningioma is more probable.

[Renal arteriovenous fistula associated with fibromuscular dysplasia of the renal arteries]. / Fistule artérioveineuse rénale associée a une dysplasie fibromusculaire des artères rénales.

Three to 5% of hypertensive diseases have a renovascular origin. Atherosclerosis and fibromuscular dysplasia are the two major causes of renovascular hypertension. Association of renal arteriovenous fistula and fibromuscular dysplasia is uncommon. The authors propose to illustrate the usefulness of Doppler ultrasonography and digital subtraction angiography in the diagnostic and therapeutic management of a renal arteriovenous fistula associated with fibromuscular dysplasia discovered after severe preeclampsia in a 30 year-old woman.

Magnetoencephalography in stroke: a 1-year follow-up study.

Recovery after stroke is closely linked to cerebral plasticity. Magnetoencephalography (MEG) is a non-invasive technique, which allows location of cerebral cells activities. In the present work, a cohort of patients has been studied with MEG. Twelve patients with a recent ischemic or hemorragic stroke were included as soon as possible after onset of stroke. Neurologic assessment, including standard neurologic examination, functional independence measure (FIM) and Orgogozo's scale was performed for 1 year in addition to a study of the somatosensory evoked field (SEF) using a 37-channel Biomagnetometer system. No response could be recorded in five patients at the first SEF exploration. In three cases, no response was ever recorded during the study. All these patients had a bad recovery. The location of the SEF sources was always in the normal non-infarcted cortex of the postcentral gyrus. Sensory recovery seemed to be linked to the reorganization of the persistent functional cortex, which was a limiting factor for recovery. These observations confirm the experimental results obtained in animal models. After stroke it can be assumed that in the case of incomplete lesion, an intensive sensory peripheral stimulation could maximize the use of residual sensory function and then contribute to improve the sensory deficit. In case of total sensory loss other techniques have to be used, such as visual monitoring of hand activity in order to improve hand function.

The RETAIN project: DICOM teleradiology over an ATM-based network. Radiological Examinations Transfer on an ATM Integrated Network.

The RETAIN project (Radiological Examinations Transfer on an ATM Integrated Network) has aimed at testing videoconferencing and DICOM image transfers to get advice about difficult radiological cases over an asynchronous transfer mode (ATM)-based network, which affords a more comfortable interface than narrow-band networks and allows exchange of complete image series using the DICOM format of studies. For this purpose, an experimental ATM network was applied between six university hospitals in four different countries. An assessment of the functionalities of the system was performed by means of log-file analysis, video recording of the sessions and forms filled out by the participants at the end of each session. Questionnaires were answered by the users at the end of the project to bring out perspectives of utilisation and added value. We discussed 43 cases during 20 sessions. For technical or organisational problems, only 20 of the 36 planned sessions took place. The throughput over ATM (10.5 Mbit/s, 20 times faster than six ISDN B-channels) was adequate. Despite the experimental configuration of the network, the system was considered as satisfactory by all the physicians. In 72 % of the sessions, the expected result (answer to the question) was gained. By common consent, videoconferencing was unanimously regarded as a prominent tool in improving the interaction quality. Asynchronous transfer mode is an efficient method for fast transferring of radiologic examinations in DICOM format and for discussing them through high-quality videoconferencing.

[Spontaneous disappearance of a thoracic disc hernia]. / Disparition spontanée d'une hernie discale thoracique.

We report a case of a 55-year-old man who experienced spontaneous resolution of a large herniated disc at T8-9. Spontaneous resolution of disc herniation is well known at the lumbar level. This case is a rare example of a large thoracic disc herniation diagnosed by CT and MRI which completely regressed six months after a medical treatment with complete disappearance of symptoms. The mechanism of resolution of a disc herniation is unclear and we discuss theoretical considerations. We emphasize the interest of conservative therapy in patients with thoracic disc herniation without neurological deficit.

Influence of the teleradiology technology (N-ISDN and ATM) on the inter-hospital management of neurosurgical patients.

We set out to assess the influence of a teleradiology network on the relations between a general hospital and a 100 km distant university hospital in the context of neurosurgical emergencies, and compared a commercially available technology, N-ISDN (Narrowband Integrated Service/Digital Network), to an emerging technology, ATM (Asynchronous Transfer Mode). The evaluation was conducted using records of advice request calls and patient transfers. Three phases were considered: without teleradiology, with transfer of digitized images over N-ISDN at 64 kbps, and with an experimental ATM network at 10.5 Mbps with DICOM image transfers and videoconferencing. Additionally, staff meetings over ATM videoconferencing were set up. To assess the ATM service, we used log files and questionnaires, 108 advice requests were studied over a 18 month period. The average transmission time for one examination was 38 s with full DICOM image resolution over ATM, versus 150 s with 10:1 JPEG (Joint Photographic Expert Group) compression over N-ISDN. Up to 50% unnecessary patient transfers were avoided. Advice requests increased fourfold, and non-urgent advice requests increased from 0 to 21%. Despite the experimental configuration of the ATM network, the service gave satisfaction to all the physicians. Videoconferencing was unanimously regarded as a prominent tool to improve the quality of interaction. It was particularly useful for non-urgent cases and distant staff meetings. Teleradiology can improve the relations between hospitals through an increase of urgent and non-urgent advice requests. Asynchronous transfer mode is an efficient way for fast transfer of radiological examinations in DICOM format and for discussing them through high-quality videoconferencing.

Analysis of cerebrovascular diseases by a new 3-dimensional computerised X-ray angiography system.

We set out to validate the concept of three-dimensional (3D) angiography. We evaluated the sensitivity and the quality of morphological analysis mode possible by an experimental system for imaging cerebrovascular disease versus standard digital subtraction angiography (DSA). The system, the 3D Morphometer, is a computerised X-ray angiography unit capable of acquiring a set of two-dimensional (2D) projections during a rotation and then reconstructing a 3D volume from them. We studied 78 patients with suspected cerebrovascular disease. 3D and 2D images (standard 2D DSA performed during the same procedure), were reviewed blindly to assess detection and display of morphological characteristics of cerebrovascular diseases. We found 53 aneurysms, 22 arteriovenous malformations and two venous angiomas. On 3D angiography we detected two aneurysms we missed on 2D angiography. In 47 aneurysms on which further data were obtained during surgery or embolisation, the 3D angiography allowed more accurate analysis of the neck and surrounding vessels in cases in which the 2D angiographic findings were doubtful. Assessment of arteriovenous malformations was equivalent with both techniques. Under the conditions of our study, the technical constraints being the same for both methods, 3D angiography was superior to 2D angiography. Implementation on C-arm vascular systems is being evaluated.

[The role of 3-dimensional reconstructions in the angiographic evaluation of cerebral vascular malformations: 3D morphometry]. / Place des reconstructions tri-dimensionnelles dans le bilan angiographique des malformations vasculaires cérébrales: le morphomètre 3D.

The need for medical images which can directly contribute to therapeutic decision making has led to the development of 3D visualization techniques. With this objective, a procedure capable of producing 3D volume reconstructions using isotropic voxels from digitalized 2D films obtained by rotation around the object has been developed: 3D morphometry. The technique has been assessed from 1993 through 1996 for vascular malformations in the brain, particularly aneurysms. Recognition of collateral vessels originating at the malformation was helpful in better identifying the lesions and evaluating possible therapeutic difficulties. The morphometric sequence thus is a possibility for the future assessment of neurovascular arches.

[Test of a teleradiology network based on ATM (asynchronous transfer mode)]. / Essai d'un réseau de téléradiologie basé sur ATM (asynchronous transfer mode).

The retain project (Radiological Examination Transfer on ATM Integrated Network) consisted in teleradiology trials focused on pediatric imaging between two university hospitals. Rennes (France) and Barcelona (Spain) using an integrated broadband communication network based on ATM (asynchronous transfer mode), as part of a European research program. The network used was a full 10 Mbits/s ATM network directly connected to local PACSs (medical imaging hospital networks). One important reason to explicitly consider ATM for medical imaging is that multimedia applications on such networks allow integration of digital data and person-to-person communication. The utility of broadband communication for teleradiology has been confirmed. High quality video and sound are important for both human communication and medical video transfer. The project led to guidelines regarding technical options still open to improvement.

[Diabetes insipidus caused by metastasis to the hypothalamo-hypophyseal axis. Apropos of 4 cases]. / Diabète insipide par métastase de l'axe hypothalamo-hypophysaire. A propos de 4 cas.

This study concerns the cases of 4 patients with polyuria and polydipsia syndrome as part of a known evolutive neoplasia. MRI demonstrated an intra- and supersellar tumoral process developed from the pituitary stalk and the posterior pituitary lobe suggesting metastasis.

Hemochromatosis: diagnosis and quantification of liver iron with gradient-echo MR imaging.

PURPOSE: To assess the role of magnetic resonance (MR) imaging in detection and quantification of liver iron overload. MATERIALS AND METHODS: MR imaging at 0.5 T was prospectively performed on 77 patients (67 with liver iron overload and 10 without) who underwent a liver biopsy with biochemical determination of the liver iron concentration (LIC) (normal, < 36 mumol per gram of liver tissue [dry weight]). Ratios of signal intensities and liver T2 relaxation time were calculated from images obtained with spin-echo and breath-hold gradient-echo (GRE) sequences. RESULTS: Liver-to-tissue signal intensity ratios were better correlated with LIC than T2 relaxation time. Long-echo-time GRE sequences were the most sensitive for detection of slight overload. Thus, high sensitivity (94%) and specificity (90%) were obtained with a liver-to-fat ratio threshold of 1. The quantification of iron with MR imaging was accurate when the LIC was 80-300 mumol/g. For heavy overload, above 300 mumol/g, quantification was impossible owing to complete signal loss. Pancreatic and splenic signal intensity were unchanged in most cases. CONCLUSION: This method, which can be improved by using more sensitive sequences with a high-field-strength system, should be competitive with biopsy for the diagnosis of substantial liver iron overload.

Magnetic resonance imaging in acute cerebral ischaemia.

The frequency of cerebral vascular accidents justifies a rapid evaluation of the patients to distinguish between ischaemia and haematoma. In acute cerebral ischaemia, data from the literature show that magnetic resonance imaging is sensitive early (4th to 6th hours) and anatomically efficient (posterior fossa, brain stem) although it lacks specificity, being based on water movements alone. The most difficult differential diagnosis in the acute phase is bleeding, and in that phase early computerized tomography images are easier to interpret.

[Congenital intrahepatic arterio-portal fistula: diagnostic and therapeutic aspects]. / Fistule artérioporte intrahépatique congénitale: aspects diagnostiques et thérapeutiques.

The authors report the case of a 4 month old child presenting with a congenital arteriovenous fistula of the left hepatic lobe, revealed by a melaena. Doppler ultrasonography and angiography showed a voluminous vascular malformation fed by a left hepatic artery and fistulized in the portal vein. The therapeutical approach was first palliative, by ligature of the left hepatic artery which proved unsuccessful and resulted in re-permeation of the malformation through a right hepatic artery. Two embolization procedures were then attempted, without success. A left hepatectomy was then performed to remove the malformation. The main event of outcome was the secondary occurrence of a portal cavernoma, with persistent splenic segmentary portal hypertension, and oesophageal varicosity. This case report is the occasion for a literature review on congenital arteriovenous fistulae in the portal region, and for a discussion on therapeutical modalities.

[Diffuse subcortical heterotopias of the gray matter]. / Hétérotopies sous-corticales diffuses de la substance grise.

Three cases of diffuse subcortical gray matter heterotopias in children are reported. Generalised seizures and mild mental retardation were the most frequent signs. No specific electroencephalographic pattern was recognized. Magnetic resonance imaging scans showed the thick diffuse layer of heterotopic gray matter which was surrounded by normal white matter. Gyration was normal, and no associated malformation was observed. This neuronal migrational disorder happens between the 10th and 16th gestational week. Nineteen observations (17 girls) are reported in the literature. The filiation with agyria-pachygyria and the possible genetic transmission are discussed.

Superparamagnetic iron oxide: clinical time-response study.

Superparamagnetic iron oxide (AMI 25) is a promising new contrast agent for imaging the reticuloendothelial-system. Iron oxide crystals possess a large magnetic susceptibility and enhance proton relaxation rates, especially transverse relaxation (T2). In order to guide the clinical utilization of this contrast media we analyzed 4 patients with malignant lesions of the liver before and after slow intravenous administration (20 mumol Fe/kg) of AMI 25. We performed two magnetic resonance (MR) sequences at different times using a 0.35 T magnet. MR signal-to-noise ratio (SNR) of the reticuloendothelial system (particularly the liver SNR) decrease promptly. The maximum decrease in SNR (67-72% for the liver, 46-65% for the spleen, 23-41% for the bone marrow) is observed 3 h after injection (P less than 0.01). However, except the peak of contrast enhancement in T1-weighted sequences of splenic tissue, the curve describes a plateau within 30 min and 6 h, allowing a delay between injection and imaging. T2-weighted sequences give a greater contrast-to-noise ratio (CNR) by adding the spontaneous tumor contrast to the effect yielded by AMI 25. These results suggest that images must be acquired between 1 and 6 h after intravenous administration of superparamagnetic iron oxide.

[Radiologic aspects of a case of Waldmann's disease]. / Aspects radiologiques d'un cas de maladie de Waldmann.

The Waldmann's disease or intestinal lymphangiectasia is a rare disease. We observed a case which occurred in a 14 years old boy. The disease was discovered in the screening of an intermittent diarrhea. The diagnosis was suspected on biological signs of protein-losing enteropathy and the presence of lymphangiectasias seen during endoscopy. The lymphography was conclusive showing the abnormal opacification of the mesenteric region. The other examinations were also important to assert the idiopathic origin of the disease.