Magnetic resonance imaging of aneurysms and chronic dissections of the thoracic aorta.

Magnetic resonance imaging (MRI) was performed in 30 patients having an aneurysm or chronic dissection of the thoracic aorta. Using a magnetic field of 0.5 Tesla, multislice image acquisition was obtained by the ECG gated spin-echo imaging technique with dual-echoes. These results were retrospectively compared with those obtained in the same patients by angiography and computerized tomography (CT). In 10 cases of aneurysm, MRI measured their diameters and residual lumina and assessed the extension of the aneurysm with the same precision as CT scan and angiography. In 17 other cases, the diagnosis of chronic dissection was made by documenting an intimal flap and double channel filling of the aorta, and MRI compared favorably with CT scan. In three dissections in which the false lumen was thrombosed, MRI was unable to distinguish between dissection and partially thrombosed aneurysm. We believe MRI constitutes a useful noninvasive method for the study of aneurysms and chronic dissections of the thoracic aorta.

MR evaluation of chronic aortic dissection.

Thirty patients with suspected or known chronic aortic dissection were imaged with magnetic resonance (MR), CT, and angiography. Five of these patients had previously undergone surgical repair of the ascending aorta for a type A dissection. Magnetic resonance demonstrated an intimal flap and a double lumen in 25 cases. In four cases with a thrombosed false lumen, proved angiographically, an intimal flap and double channel were not seen. In two of four aortic dissections with a thrombosed false lumen, CT made the diagnosis by showing displaced intimal calcifications not visualized on MR. In one case the aortic dissection was made on CT and angiography but was not supported by MR which showed an aortic aneurysm, subsequently confirmed at surgery. Magnetic resonance, CT, and aortography differentiated between type A (nine patients) or B (20 patients) dissection in all cases and demonstrated extension into the abdominal aorta. Extension into the iliac arteries was seen on MR in three patients but missed in nine patients. Magnetic resonance differentiated the true and false lumen in all but one case. Thrombosis of the false channel was identified in four cases by a decrease in signal intensity on the second echo image. Cardiac gating and longitudinal contiguous sections seemed to be more suitable for appreciation of the relationships with arch vessels. Transverse contiguous slices allowed determination of the origin of celiac, mesenteric, and renal arteries from either the true or the false lumen. This study confirms that MR is an accurate and noninvasive method for the evaluation and follow-up of chronic aortic dissection, obviating the need for iodinated contrast media.

Anatomy of the thoracic aorta: magnetic resonance imaging and interpretation of flow phenomena.

The authors present the results of magnetic resonance imaging (MRI) in the investigation of the anatomy of the thoracic aorta in a group of eight volunteers and in one patient with presumptive Takayasu's disease but with normal aorta. Transaxial, coronal, sagittal and oblique slices were made and the morphologic results are presented. Major flow phenomena are also discussed and some examples given.

[Magnetic resonance imaging of aortic aneurysm]. / L'imagerie par résonance magnétique des anévrysmes de l'aorte.

Magnetic resonance (MR) imaging in 16 patients with aortic aneurysm used a field of 5,000 Gauss and spin echo multisection imaging with two echos. Results were compared retrospectively with those of echotomography, computed tomography and angiography. Surgical exploration allowed correlation with histopathology in 13 patients. The external diameter of aneurysm and of its residual lumen and length of aneurysm were in each case evaluated precisely by MR. In patients with abdominal aneurysm, MR images identified the limits of the aneurysm in relation to renal and iliac arteries. In aneurysms of thoracic aorta, synchronization of signal with an ECG and longitudinal imaging provided data on relations of aneurysm with supraaortic trunks. In 2 patients with extensive, partially thrombosed thoracic and abdominal aorta aneurysm, MR imaging could not eliminate a diagnosis of aortic dissection with thrombosed false lumen. Finally, aortic wall calcifications were never apparent on MR images.

Primary lung cancer staging: prospective comparative study of MR imaging with CT.

Forty-four patients with bronchogenic carcinoma were studied prospectively by both computed tomography (CT) and magnetic resonance (MR) imaging of the thorax during the week preceding thoracotomy. Transaxial MR imaging sequences included T1- and T2-weighted sequences. Coronal and sagittal T1-weighted sequences were added according to tumor location. CT and MR studies were reviewed separately, and the results were compared with surgical and pathologic findings on the basis of TNM classification. No statistically significant differences were found between the two imaging methods for the evaluation of tumor extent or node involvement. T2-weighted sequences did not yield further information on tumor extent or node involvement. Additional imaging planes (coronal or sagittal) appeared useful to study chest wall invasion. Analysis of concordances and discordances did not indicate whether one modality could be substituted for the other, or which diagnostic strategy might be more useful.

[Magnetic resonance imaging in the study of pulmonary hilar involvement]. / L'imagerie par résonance magnétique dans l'étude des atteintes hilaires pulmonaires.

A retrospective analysis of results of magnetic resonance imaging (MRI) was conducted in 28 patients with uni- or bilateral pulmonary hilum lesions and findings compared with those of computed tomography (CT). All abnormal hilar masses examined were between 1 and 5 cm in diameter and were easily detected by transverse axial imaging. Contrast of their images was very high in relation to hilar bronchovascular elements in the two types of spin echo sequence with a short TR (0.5-0.7 s) and a long TR (1.5-2 s). Differentiation between tumoral or adenopathies and vessels was simpler than with CT with intravenous contrast. For screening of possible extension of hilar tumors. MRI appears to be superior to CT for providing data on vascular relations of lesions but inferior to CT for determining bronchial relations. Mediastinal extension of hilar tumors is easily defined by the short TR sequence but MRI supplies data of greater value than CT only in a low proportion of cases and then partly as a result of complementary coronal and sagittal imaging.

[Tomodensitometry and cerebral scintigraphy. Respective indications]. / Tomodensitométrie et scintigraphie cérébrales. Indications respectives.

The comparative values of computerized tomography and radionuclide scan for the diagnosis of brain lesions were assessed on a series of 550 patients. A number of indications for each of these two methods have emerged from our results and from those found in the literature. The biases encountered in this type of study are discussed, and a "decision-making flow-chart" is proposed. The procedure of choice is computerized tomography in patients with suspected tumour or intracerebral haematoma, and radionuclide scan in those with suspected subdural haematoma or superficial cerebrovascular disease. The usefulness of clinical examination to determine precisely which of these two methods should be used cannot be overstressed.

[Magnetic resonance imaging in the exploration of hepatic masses]. / L'imagerie par résonance magnétique (IRM) dans l'exploration des masses hépatiques.

Exploration was conducted by magnetic resonance imaging (MRI) at 0.15 T in 33 patients with hepatic masses, including 18 with malignant tumors, 11 with benign tumors and 4 with non-tumoral masses. All tumors appeared hyperintensive in relation to liver on images acquired by long TR spin echos (SE) and all, except for one fatty tumor, appeared hypointense in relation to liver on images acquired in inversion-recuperation (IR). The study seemed to provide data demonstrating that MRI at 0.15 T enables visualization of hepatic masses with a degree of precision that approaches that of other imaging methods. Tumors of the small size of the order of a centimetre can be detected. Tumor outlines and vascular relations are clearly demonstrated without use of contrast. Characterization of masses is still insufficient since the simple play of contrasts between tumor, parenchyma and vessels does not allow differentiation of malignant from benign tumors, nor the identification of a given histologic type.

[Transformation of cerebral infarction into hemorrhage during x-ray computed tomography in a patient under anticoagulant treatment]. / Transformation d'un infarctus cérébral en hémorragie, au cours d'un examen tomodensitométrique, chez un patient sous traitement anticoagulant.

Repeated CT scans provide the only means of confirming the initial ischemic nature of a cerebrovascular accident and its eventual course towards a hemorrhage. Precise data can be obtained as to the frequency of this complication as a function of factors such as the embolic origin of the infarct or associated anticoagulant therapy. The present case shows that contrast medium, at least in patients receiving anticoagulant treatment, may constitute a risk factor by increasing the possibility of transformation of a pale infarct into a hemorrhagic one. Possible relevant properties of iodized contrast media with respect to this type of complication are considered.

[Computer tomography changes in multiple sclerosis (author's transl)]. / Aspects tomodensitométriques évolutifs de la sclérose en plaques.

An attempt is made to evaluate the semiological data supplied by computer tomography, following its use on several occasions in 4 patients with multiple sclerosis. Three known signs in the encephalic forms are defined: cerebral atrophy, low density plates of sclerosis that do not take up the contrast medium, and those that do. These localized lesions are distinguished by their frequent multiplicity, often periventricular location, and absence of a mass effect. The semiological value of these signs involves discussion on the poor results of statistical evaluation, the significance of histology examination results, which are still being studied, and more particularly the variability, the best evidence of which seems to be the beginning and/or the changes occurring in contrast medium uptake. To this major diagnostic argument can be added the discovery of multilocular lesions which are sometimes present without clinical manifestations. Computer tomography is an essential procedure for establishing the differential diagnosis of multiple sclerosis, avoiding numerous valueless arteriographies, is a fundamental method for early positive diagnosis, and perhaps an element for establishing prognosis.

[Radiological appearances in postoperative obstructions (author's transl)]. / Aspects radiologiques des occlusions post-opératoires.

In the light of 9 cases, the authors study the varioud radiological appearances of postoperative obstructions. These may be early, before the restoration of intestinal transit, or secondary, during the days following the restoration of transit. The authors eliminate late postoperative obstructions from this study. There are various mechanisms of postoperative obstruction: organic obstructions may be due to an adhesion but also to agglutination or incarceration of intestinal loops. Functional obstructions most often accompany a localised area of inflammation. Mixed obstructions are a special feature of the postoperative period: agglutination of loops in contact with an area of inflammation. The authors emphasize the difficulty of radiological interpretation and the frequent disagreement between radiological and surgical findings.