Frontiers in European Radiology – serie

The second volume of Frontiers in European Radiology covers two very promising techniques in diagnostic radiology, namely digital radiography and nuclear mag­ netic resonance imaging. Leading experts in both fields from Europe and the Unit­ ed States were invited to give a critical overview; digital fluoroscopy is reported on mainly by American scientists since this technique has been developed primarily in the United States, while the results of nuclear magnetic resonance imaging are pre­ sented by British groups currently at the forefront of research in this field. The pa­ pers reflect the state of the art at mid-1981, when the contributors gathered for the yearly symposium on Current Topics in Diagnostic Radiology in Berne, Switzer­ land. Nuclear magnetic resonance imaging, also known as spin imaging or zeugmato­ graphy, has produced striking progress within the past few years - even within the past few months - as described in three papers of this volume. The images generally reflect the distribution of mobile protons contained within water and fats, and pro­ vide remarkable discrimination between different tissues. Malignant tissue might be identified with this technique, and a wide range of disorders associated with water concentration, diffusion, and flow would be amenable to study; the measurement of blood flow could be particularly interesting.

The quantitative analysis of blood flow within central and peripheral blood vessels has attracted more and more interest, for with the rapid developments in vascular surgery and the introduction of percutaneous transluminal angioplasty, it is becom­ ing increasingly important to be able to measure regional blood flow in man. In clinical radiology, angiography has been used predominantly from the point of view of its morphological applications. However, theoretically angiography may also be regarded as a specific application of indicator-dilution measurements of blood flow. The indicator is contrast medium (CM), the changing concentration of which is re­ corded by cinematography or video-electronic systems at sites downstream from the point of injection. The curves of density thus obtained correspond to indicator-di­ lution curves. The blood flow can be calculated from the concentration-time curves ofCM in much the same way as it is estimated from other indicator-dilution curves. In our early work with clinical application of videodensitometric measurement of blood flow in the iliac artery, we found that this method did not offer as high a degree of accuracy as one would have expected from investigations by other authors. We saw that we needed to examine the following problems: 1. We had to investigate whether our conventional X-ray equipment and video­ densitometer could be viewed as a linear measuring system. To what extent do unavoidable nonlinear changes in the measuring signals influence the blood flow values? 2.

Considerable advances have been made over the years in the study of the physiological and diseased states of the kidney, so that our present-day diagnostic capabilities permit not only morphological, but also functional inter-relations to be registeres. The first step toward function diagnostics was taken with the introduction of kymography. This was followd by serial angiography, and then came cineradiography which made simultaneous morphological and functional radiological examinations feasible. 2 Physiology of Kidney 2. 1 Hemodynamics of Renal Arteries Because of the negligible vascular elasticity of the rani arteries, the diameter variation resulting within one cardiac action is about 1 % [14]; but with these variations being lost in the accuracy of measurement, however, blood flow can be compared to the flow of liquid in rigid tubes. In a rigid tube, the velocity of the individual particles of liquid varies in relation to its distance from the tube axis. Under normal circumstances, a laminar flow prevails in the arteries, the blood flowing parallel to the vascular wall in coaxial cylindrical layers. The velocity is referred to here as v. The flow rate, I, stands for the ratio of the volume of liquid, V, flowing through a cross section of a tube to the time, t, required for this, or also for the product of flow velocity v and the cross section of the tube q: 1= Llv: Llt and I = v x q.

Congenital hip dysplasia and dislocation are common diseases of newborns and small infants, with frequently severe consequences if orthopaedic therapy is not initiated at an early stage. Therefore many clinicians have been looking for a simple method for the investigation of the hip joint in the early neonatal period. Up to 1980 the diagnosis of hip dysplasia could usually not be made before the 3rd month of life, by means of pelvic roentgenography. Only incomplete or complete unilateral dislocations were diagnosed in the neonatal age group. In 1980, however, Graf, an Austrian orthopaedic surgeon, began using ultrasound investigation ofthe hip joint in newborns and small infants in order to make an early diagnosis and to avoid radiation exposure. The intention of the present study was to compare ultrasound of the hip joint with other established diagnostic procedures and to establish whether it is suitable as a screening procedure in newborns. 2 Incidence of Congenital Hip Dysplasia and Dislocation In 1972 Barlow reported that 90 % of hips which are unstable at birth develop to normal joints spontaneously without any therapy. Visser (1984) thus suggested determining the percentage of hip dislocations after the 2nd - 3rd month of life so that children with spontaneous stabilisation would be excluded.

With contributions by numerous experts

Contents Abdominal and Thoracic Magnetic Resonance Angiography: Challenges, Technical Approaches and First Clinical Applications. H.U. Kauczor, R. Hausmann, W. Semmler Magnetic Resonance Spectroscopy of Skeletal Muscle. F. Tr{ber, W.A. Kaiser, G. Layer,C. Kuhl, M. Reiser Hepatic Tumors: Relaxometry and Quantitative Tissue Characterization with Magnetic Resonance Imaging. A. Steudel, F. Tr{ber, M. Reiser Liver-Specific Particulate Contrast Agents: An Overview I. Ivancev, A. Lunderquist Contrast Medium Induced Nephropathy:Animal Experiments H.S. Thomsen et al. Rheological Properties of Blood after Diagnostic Cardiac Catheterisation with Iopromide. R. Bach et al. Color Coded Doppler Sonography of the Male Urethra During Voiding: New Observations of Flow in an Aqueous Medium and Their Physical Foundations. P. H}bsch, F. Hager, E. Benes Development of a Model of Arterial Stenosis Analysis Using Digital Subtraction Angiography: A Parametric Study of Image Quality. C. Renaudin, I. Magnin, A. Amiel Arterial Calcifications in Thoracoabdominal Computer Tomography: Frequency and Correlation with Risk Factors and Cardiovascular Diseases. J. G|rich et al.