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In this paper, the author proposes two themes of future research: a) time is a sign of the image. It occupies a place in the triadic Peirce's systems presented here; b) time is the fourth dimension of the image even when it is not visible as a sign.

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The author demonstrates examples of symmetrical images in human pathology. He introduces the subject with arguments of the philosophical and cultural areas. He defines asymmetry and dissymmetry. The symmetrical images are linked to different planes (natural, artificial and mixed). With numerous symmetrical pathological images he demonstrates new teleonomical hypotheses: interchangeable, enantiomorphous, turned, rotated images. The concept of symmetry, asymmetry and dissymmetry leads to the concept of symmetrical thinking in clinical imaging.

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The author places the metaphoric image of "comet tail" in the semiotic structural and triadic system of Peirce. This metaphoric image utilises the iconic quality of "resemblance". The discussion of the image of "comet tail" gives the author the opportunity to distinguish three varieties. One variety is static (example: round atelectasia), the other is dynamic (example: cancer of the breast) and the third is artificial (sonographic artifact).

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OBJECTIVE: We studied the ability of MRI to predict fetal shoulder width (FSW). MATERIALS AND METHODS: In 30 patients referred for MR pelvimetry, measurement of FSW was performed and compared with caliper measurements at term. We report here the feasibility of a method using axial and coronal MR images oriented to the fetal body axes. RESULTS: Shoulder width by MRI (mean = 12.76 +/- 1.42 cm) correlated significantly with postnatal orthopedic caliper measurements (mean = 12.99 +/- 1.37 cm; r = 0.955, SEE = 4.29 mm, p = 0.00001) and with birth weight (r = 0.63, p = 0.0005). Mean paired differences showed a statistically significant 2.3 +/- 4.2 mm underestimation of FSW by MRI (p = 0.01). This reasonably quick nonionizing technique seems to have the potential for evaluating shoulder dystocia and deserves further evaluation.

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A case of supracardiac total anomalous pulmonary venous drainage (TAPVD) in an infant aged 2 1/2 months is presented. Diagnosis was established non invasively by magnetic resonance image (MRI). Not only did MRI precisely depict the anomalous venous pathway but it moreover securely excluded pulmonary venous obstruction.

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We present two cases of bilateral, symmetrical pedicular clefts associated with dural ectasia in von Recklinghausen's disease (neurofibromatosis). In one case the pedicular cleft was at the T12 level, while in the other it was at L4, and was responsible for spondylolisthesis. Two hypotheses are advanced to explain the cleft: (1) a congenital, dysplastic osseous defect and (2) bilateral stress fractures related to thinning of the pedicle caused by dural ectasia.

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Thirty-four patients with documented transmural MI were studied with gated three echo, multislice MR imaging. In 12 patients MRI MI size was compared with CK release measurement, Tl-201 SPECT defect, and with Tc-99m LVEF. Infarct was visualised in 29/34 patients on 3rd echo images (18/34 on 2nd and 6/34 on 1st echo images). Mean MR infarct size (planimetered from 3rd echo images): 33.1 +/- 9% overestimated the SPECT defect (mean value of 23.8 +/- 15%). However, the overall correlation between MRI and Tl-201 sizing was significant: r = 0.82; p less than 0.001; SEE = 5.5%. The correlation with LVEF also appeared significant: r = -0.61; p less than 0.038.

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Between February 1988 and July 1989, the authors used magnetic resonance imaging (MRI) to study 54 newborn infants aged between 2 and 35 days and suspected of congenital heart disease. All children also underwent echocardiography and 7 angiography during the neonatal period (13% of children studied). MRI was well tolerated and there were no adverse events. MRI proved to be complementary to echocardiography in several lesions affecting the great vessels of the base and the left atrial region. Agreement between angiography and MRI results was very good, with MRI being more useful in one case. MRI enables full and non-invasive postoperative follow-up. In conclusion, despite the great heterogenicity of the cardiac malformations studied and which requires a degree of caution, the authors feel that MRI is a second line investigation after echocardiography. It may limit the indications of angiography. Its own indications are the retrocardiac region, the main arteriovenous vessels of the base and postoperative follow-up in congenital heart disease. The development of techniques such as angio RM will further modify data in the future.

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As in other pathological processes of the heart, the contribution of MRI is not limited to optimal anatomical evaluation but also offers functional or etiological information (approach of tissue characterization). In this work we report on our experience in evaluating normal and pathological pericardium with MRI spin echo sequences. The results with 41 patients, including pericardial effusion, thickening, and mass are discussed and confronted with previously reported data. Contrary to classical echocardiographic notions, pericardial effusions are more frequently in the anterior than posterior location (26/30 vs. 19/30 p less than 0.03). Not only does MRI provide a precise and positive diagnosis, but also a rather clear distinction appears in spin echo sequences between hemopericardium with high signal intensity and other effusions with lower signal (high intensity found in 6/6 patients with hemopericardium versus only 8/24 in the remaining group; p less than 0.01). When constriction signs are present, MRI solves the difficult differential diagnosis between pericardial thickening and restrictive cardiomyopathy. In paracardiac primary or metastatic tumors pericardial involvement is clearly demonstrated. Distinction between paracardiac, respectively pericardial cyst or false aneurysm is possible. We conclude that MRI is a new imaging method, complementary to echocardiography and/or computed tomography in the evaluation of pericardial pathology especially when hemopericardium, constrictive pericarditis, or tumoral etiologies are suspected. Important technological improvements are needed to solve the problem of long acquisition time and to improve the possibilities of tissue discrimination.

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Until now little attention has been paid to the potential of MR imaging in congenital heart disease of the newborn. ECG-gated MRI was therefore performed at 0.5 tesla in 23 newborns (mean age 7.5 days) with suspected congenital heart disease. Two newborns were controlled after surgery (switch, Blalock-Taussig procedure). All had undergone prior evaluation by two-dimensional Doppler echocardiography (2-D DE). MR imaging was of a satisfying quality in all but one newborn. The aim of this study was to assess complementary information provided by MRI in comparison to 2-D DE. Pre-operatively MRI missed some abnormalities shown by 2-D DE: one coartaction, one ductus arteriosus and one pulmonary atresia. MRI demonstrated lesions that echocardiography had either failed to visualize or found inconclusive, including double aortic arch (one patient), muscular ventricular septum defect (two patients) and severe ductus arteriosus (one patient). In one of the two patients with a ventricular septum defect, angiography was avoided and in the other patient it merely confirmed the MRI results. Post-operatively, MRI demonstrated information complementary to that obtained from to 2-D DE: (1) clearly visualizing the reinsertion of the coronary arteries in the 'switched' transposition of the great vessels, (2) appreciating the diameter and patency of the palliative shunt in the Blalock-Taussig procedure.

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The authors describe various alterations to the cervical spinous processes and stress the importance of examining the cortical bone.

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The author describes some particularities seen in the abnormal or pathological image of the cervical spine: the osteolysis of the cortical bone in the spinous processes, the "Y" shaped course of the corporeal veins, the notch in interspinous bursitis, and the main forms of constitutional stenosis of the cervical canal.

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The authors report three cases of lumbar apophyseal joint lipoma located at the L4/L5 or L5/S1 level. CT scan makes the diagnosis easily possible; indeed erosive changes with enlargement of the upper portion of the lumbar articular joint and anterior displacement of the top of the superior facet are associated with intra-articular fatty densities. Clinical symptoms are rarely encountered and may be related to narrowing of the upper portion of the intervertebral foramen.

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