Acta radiologica. Supplementum最新文献

The human vestibular aqueducts are classified into 3 types and into the types hyper-, normo- and hypoplastic. The types correspond with each other up to over 85%. For a better understanding of the radioanatomy and for the proper interpretation of radiograms, we describe the presence of a flat recess-like widening of the peripheral portion of the aqueduct, as well as other findings.

Patient safety should be in focus when using contrast media (CM) in diagnostic and interventional cardiac procedures. Side-effects that occur during cardioangiography due to hemodynamic effects of CM include direct effects on the heart, effects on the systemic and pulmonary circulation, and effects on the blood volume. Although not a totally inert solution, iodixanol (Visipaque) has less pronounced direct inotropic effects on the heart than have other CM; its vasodilatory effects on peripheral arteries are smaller, and the increase in blood volume is smaller after administering iodixanol than after other CM. Thus, iodixanol represents a further step forward in terms of reducing side-effects during contrast-enhanced diagnostic and interventional cardiac procedures.

This study was designed to compare the cardiac electrophysiology and mechanical effects of iodixanol to those of iotrolan, iopromide, ioxaglate and diatrizoate. Two consecutive injections of contrast media (CM) (0.3 g I/kg and 0.9 g I/kg b.w.) were given to spontaneously beating, Langendorff-perfused rat hearts. CM were given as a single, short-lasting bolus injection (i.e. over 2 and 5 s). Changes in aortic pressure, left ventricular pressures and ECG were continuously recorded during constant volume perfusion. The nonionic CM had less pronounced effects on aortic pressure than had the ionic media. The peak rate of isovolumetric contraction (LV dP/dt(max)) was slightly decreased by iodixanol and iotrolan, slightly more decreased by iopromide and markedly decreased by ioxaglate and diatrizoate. Similarly, the peak rate of pressure decline (LV dP/dt (min)) was only slightly decreased by iodixanol and iotrolan. Also, the 2 nonionic dimers had the smallest effects on the left ventricular end diastolic pressure (LVEDP) and heart rate. Ioxaglate lengthened the PQ-interval, but less so than diatrizoate. THe QT-interval was only slightly lengthened by iodixanol and iotrolan, as compared to the lenghthening caused by iopromide, ioxaglate and diatrizoate. Single ventricular extrasystoles were seen in all groups. Extrasystoles up to 3 coupled beats were registered after ioxaglate and diatrizoate. No episodes of ventricular fibrillation occurred with any CM. In conclusion, the nonionic dimers, and in particular iodixanol, induce only minor changes in cardiac function, whereas the ionic dimer ioxaglate and the ionic monomer diatrizoate induce pronounced effects.

Contrast media (CM) affect normal cardiac electrophysiology when injected into the coronary arteries. High-osmolality CM cause more pronounced electrophysiological effects than do low-osmolality CM. Further, both high- and low-osmolality ionic CM have more pronounced effects than the nonionic CM. The CM-induced electrophysiological effects involve regional disturbances of depolarization and repolarization, thereby causing disturbances of impulse conduction as well as dispersion of refractoriness. Recent experimental studies have demonstrated that the addition of sodium or a balanced electrolyte supplement to nonionic CM reduces the risk of ventricular fibrillation (VF), particularly when the CM is injected in a wedged catheter situation. The reduced risk of VF may be due to the small and transient lengthening of repolarization seen in the CM-perfused area of the myocardium. Iodixanol, which is an isotonic nonionic dimer supplemented with NaCl and CaCl(2), is as well tolerated as iohexol during free coronary flow. However, when flow is restricted, such as when CM is injected through a wedged catheter, the risk of VF is less with iodixanol than with iopamidol, iohexol and ioxaglate.

A review of the literature on the effects of adding electrolytes to ionic as well as nonionic contrast media (CM) in the isolated heart model reveals that both ionic and nonionic CM favor from such addtion, if the added electrolytes are balanced with respect to each other. By enriching nonionic monomeric as well as dimeric CM with such a balanced electrolyte solution, the risk of ventricular fibrillation is reduced and myocardial contractibility is improved compared to nonionic CM without such enrichment. The new nonionic dimer iodixanol is slightly hypotonic to plasma in concentrations suitable for coronary arteriography. The water solution of iodixanol therefore contains an osmotic space in which electrolytes can be added, therby making it isotonic with plasma.

Iodixanol (Visipaque) is a new nonionic roentgen contrast medium intended for general use. Visipaque is a pharmaceutical formulation of iodixanol which is isotonic and iso-osmotic with blood. Two synthetic routes from 5-nitro-isophthalic acid to iodixanol are described. The chemical structure is confirmed spectroscopical data ((1)H-NMR, (13)C-NMR, FAB-MS, UV, IR and Raman). Chromotographic characteristics are related to the isomerism of iodixanol.

The neural tolerability of iodixanol has been assessed in studies in mice and dogs. The animals received up to 4 injections in the cisterna cerebellomedullaris while under light anesthesia. Iotrolan was included as a reference study in 1 study. The observations comprised assessment of clinical behavior, cerebrospinal fluid analysis, hematology, clinical chemistry and/or macroscopic and microscopic examination at necropsy. In addition, the repeated-dose dog study, urinalysis and opthalmoscopy were performed, electrocardiograms obtained, and respiratory rate, blood pressure and rectal temperature measured. Clinical signs and minor pathological changes caused by the injection procedures were seen in all studies in some animals treated with iodixanol as well as in control animals. Single (2.0 g I/kg) and repeated (0.960 g I/kg) intracisternal administration of iodixanol to mice caused no significant toxicological effects. Two dogs treated with a high dose of iodixanol (0.256 g I/kg; 0.8 ml/kg) had pathological changes (meningeal inflammation and/or necrosis) that were more severe than those observed in control dogs. Single and repeated intracisternal administration of 0.128 g I/kg (0.4 ml/kg) of iodixanol to dogs, however, caused no significant toxicological effects. Apart from the findings in the 2 dogs, the neurological and neuropathological changes elicited by iodixanol were similar to those induced by control or reference substances. The results from these intracisternal toxcity studies in mice and dogs indicate a significant margin of safety regarding the use of iodixanol in clinical intra-thecal indications.

Iodixanol, the radiopaque in Visipaque, is a new nonionic, dimeric roentgen contrast medium for intravascualr use. Compared to aqueous solutions of nonionic monomers, which have higher osmolality than blood, aqueous solutions of iodixanol have a lower osmolality due to dimeric structure of the molecule. As a consequence of this advantageous property, solutions of all clinical concentrations of iodixanol can be made isotonic by the addition of salts of the key electrolytes sodium and calcium to the formulation. The viscosity of all iodixanol (Visipaque) solutions is less than or equal to that of iohexol (Omnipaque) 350 mg I/ml. Iodixanol itself is an amorphorus and hygroscopic solid which is freely soluble in water. Partition coefficients show that iodixanol is even more hydrophilic than the nonionic monomers such as iohexol. The high hydrophilicity and the good aqueous solubility of iodixanol are due to the hydroxyl group in the dimer linkage and the hydrophilic amide side chains of the molecule.

Contrast medium- (CM) induced nephropathy may be evident from symptoms ranging from acute renal failure to minor changes in tubular function tests. While the incidence is usually low, it increases with the presence of risk factors and when arterial injections are made. The pathogenesis is not fully understood. No specific therapy exists, but in most cases it can be prevented by ensuring that the patient is well hydrated prior to injection of CM. The extended phase 1 study with iodixanol (Visipaque) included detailed investigations on its renal effects. No changes in glomerular filtration rate (GFR) were found. Even though enzymuria was less pronounced after injection of iodixanol than after various monomeric CM, a somewhat higher degree on intrarenal retention of CM was observed on CT examination of the kidneys after iodixanol. In nondiabetic patients suffering from severe renal failure, angiography with either iodixanol or iohexol caused no changes in GFR, or in urinary excretion of protein and enzymes. However, a higher degree of contrast retention than that seen in healthy volunteers was found.