On the heating of linear conductive structures as guide wires and catheters in interventional MRI.

The interest in performing vascular interventions under magnetic resonance (MR) guidance has initiated the evaluation of the potential hazard of long conductive wires and catheters. The objective of this work is to present a simple analytical approach to address this concern and to demonstrate the agreement with experimental results. The first hypothesis is that a long conductive structure couples with the electric field of the radio frequency (RF) transmit coil. The second hypothesis is that this coupling induces high voltages near the wire ends. These voltages can cause tissue heating due to induced currents. The experimental results show an increase in coupling when moving a guide wire toward the wall of an RF transmit coil, documented with a temperature increase of a saline solution in close proximity to the tip of the guide wire. The coupling of the wire not only presents a potential hazard to the patient, but also interferes with the visualization of the wire. A safe alternative would be the use of nonconducting guide wires. J. Magn. Reson. Imaging 2001;13:105-114.

Interventional MRI-guided brain biopsies using inductively coupled surface coils.

The technical realization of inductively coupled surface coils for interventional MR-guided procedures, and the application to brain biopsies in a 0.2 T magnet is described. The advantages compared to standard coils are discussed, and the results of 26 biopsies on eight different neuropathologic diagnoses from varying locations within the brain are presented. Initial experience shows that inductively coupled coils can offer an increased number of indications for interventional procedures in the brain, easier handling of sterility, and often a better access for the surgeon, compared to the use of standard MR head coils.

Hardware considerations for MR imaging physics.

Since its commercial introduction as a diagnostic tool in 1984, MR imaging has undergone dramatic improvements in all the features that define image quality. This article discusses what a modern MR imaging scanner should look like and how the components of an MR system, especially the magnet, gradient, and RF components must be matched with one another to ensure optimal performance.

[Physical parameters in the use of MRI tomography. Limitation due to physiologic reactions and guidelines. Radiation Protection Commission]. / Physikalische Parameter bei der Anwendung der MRT. Begrenzung durch physiologische Reaktionen und Richtlinien.

PURPOSE: The standards and regulations concerning the protection of patients and operator staff within the context of MRI are compiled. Resulting consequences regarding physical parameters are evaluated. MATERIAL AND METHODS: The static magnetic field, heating effects caused by RF-fields and acoustical noise are outlined. The actual boundaries of these parameters are compared against the relevant published standards. Peripheral stimulation limits due to pulsed gradient fields have been determined in a new clinical study. RESULTS: Many parameters recommended for the normal operating mode are already exceeded during routine MRI. Referring to our clinical study, we found that limits recommended in the MRI relevant standards are unnecessarily conservative and can actually be doubled. CONCLUSIONS: The applicable national and international standards and regulations show (at least partly) that serious differences in the definition of terms and values exist. The application of these standards would be much easier if they were made uniform. The values defined in the MR-specific standards should be adapted to actual knowledge concerning patients' safety.

Comparative efficacy of azelastine nasal spray and terfenadine in seasonal and perennial rhinitis.

The efficacy and tolerability of intranasal azelastine (0.14 mg/nostril twice daily) and oral terfenadine (60 mg twice daily) were compared under double-blind conditions in two 6-week, multicenter, parallel-group studies, including 167 patients suffering from seasonal and 52 patients suffering from perennial allergic rhinitis. In both studies, patients were symptomatic on entry and showed significant improvement on both treatments within the first 8 d of therapy, showing little further improvement with continued treatment. Symptoms most pronounced on entry--nasal itching, rhinorrhea, sneezing, and nasal obstruction--responded best to treatment (response rates 80-90%). Objective signs such as mucosal swelling and conjunctivitis improved in a manner parallel to symptoms. In perennial rhinitis, azelastine showed a trend to a superior relief of rhinorrhea and nasal obstruction, whereas terfenadine showed a trend toward better control of sneezing and nasal itchiness. No clinically relevant or statistically significant differences between treatments could be identified. The incidence of adverse effects of possible causal relationship to therapy was low. The most frequent effects in azelastine-treated patients were related to application site disorders, e.g., nasal irritation. Results indicate that with the dose used azelastine nasal spray is an effective treatment for both seasonal and perennial allergic rhinitis.

Intranasal treatment of perennial allergic rhinitis. Comparison of azelastine nasal spray and budesonide nasal aerosol.

The efficacy and tolerability of azelastine (CAS 58581-89-8) nasal spray (0.14 mg/nostril b.i.d.) and budesonide (CAS 51333-22-3) nasal aerosol (0.05 mg/nostril b.i.d.) were compared in a 6-week, multicentre, parallel group study of 193 patients suffering from perennial allergic rhinitis. Total rhinitis symptoms complex (TSC) scores derived from 10 rhinitis symptoms improved during treatment by a mean of 11.4 +/- 6.8 with azelastine and 10.8 +/- 6.4 with budesonide. Response rates, defined as a decrease in TSC of at least 50% at the end of therapy, was 79% with azelastine and 73% with budesonide. There were no significant differences between the treatment groups with respect to either target variable. Objective measurements of nasal flow rate showed a return to normal values during the 6-week therapy. Signs of rhinitis identified by rhinoscopic examination improved in parallel to symptoms. Both medications were well tolerated. The incidence of adverse events of possibly causal relationship to therapy was low. The most frequent event in azelastine treated patients was the experience of an "unpleasant" taste or smell. Occasional epistaxis occurred in both treatment groups but more frequently with budesonide. Results indicate that with the dose used azelastine nasal spray is an effective treatment for perennial allergic rhinitis comparable to that of budesonide nasal aerosol.