The combination of active catheter tracking and passive real-time visualization in CMR-guided electrophysiologic (EP) studies using advanced interventional hardware and software was safe and enabled efficient navigation, mapping, and ablation. These cases demonstrate significant progress in the development of MR-guided EP procedures.

Study Design: Retrospective, case series. Objectives: To evaluate the use of M mode ultrasonography in the evaluation of diaphragmatic paralysis in adults. Setting: Radiology department, Princess Alexandra Hospital, Brisbane, Australia. Methods: Ten patients who were referred for evaluation of suspected diaphragmatic paralysis were evaluated using M mode ultrasound. Results: Three of the patients who were scanned demonstrated normal diaphragmatic movement. The M mode trace demonstrated normal movement of the diaphragm bilaterally with quiet respiration and a sharp upstroke on the sniff test (indicating normal caudal movement of the diaphragm). Six patients were found to have a unilateral diaphragmatic paralysis. Four of these patients were noted to have a raised hemi-diaphragm on chest radiography. Of the two who did not have a raised hemi-diaphragm on chest radiography, one was permanently ventilated. The M mode trace of the paralyzed side showed no active caudal movement of the diaphragm with inspiration and abnormal paradoxical movement (ie cranial movement on inspiration) particularly with the sniff test. Conclusion: M mode ultrasonography is a relatively simple and accurate test for diagnosing paralysis of the diaphragm, in the adult population. It can be performed, if necessary, at the bedside and can be easily repeated if paralysis is not thought to be permanent. Equipment: Philips ATL Sono CT 5000 using a 2-5 MHz curved linear transducer.

The radio frequency (RF) electromagnetic field of magnetic resonance (MR) scanners can result in significant tissue heating due to the RF coupling with the conducting parts of medical implants. The objective of this article is to evaluate the advantages and shortcomings of a new four-tier approach based on a combined numerical and experimental procedure, designed to demonstrate safety of implants during MR scans. To the authors' best knowledge, this is the first study analyzing this technique. The evaluation is performed for 1.5 T MR scanners using a generic model of a deep brain stimulator (DBS) with a straight lead and a helical lead. The results show that the approach is technically feasible and provides sound and conservative information about the potential heating of implants. We demonstrate that (1) applying optimized tools results in reasonable uncertainties for the overall evaluation; (2) each tier reduces the overestimation by several dB at the cost of more demanding evaluation steps; (3) the implant with the straight lead would cause local temperature increases larger than 18 °C at the RF exposure limit for the normal operating mode; (4) Tier 3 is not sufficient for the helical implant; and (5) Tier 4 might be too demanding to be performed for complex implants. We conclude with a suggestion for a procedure that follows the same concept but is between Tier 3 and 4. In addition, the evaluation of Tier 3 has shown consistency with current scan practice, namely, the resulting heat at the lead tip is less than 3.5 °C for the straight lead and 0.7 °C for the helix lead for scans at the current applied MR scan restrictions for deep brain stimulation at a head average SAR of 0.1 W/kg.

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