Israel Medical Association Journal

Background: Magnetic resonance imaging is a diagnostic tool of growing importance. Since its introduction, certain medical implants, e.g., pacemakers, were considered an absolute contraindication, mainly due to the presence of ferromagnetic components and the potential for electromagnetic interference. Patients with such implants were therefore prevented from entering MRI systems and not studied by this modality. These devices are now smaller and have improved electromechanical interference protection. Recently in vitro and in vivo data showed that these devices may be scanned safely in the MRI.

Objectives: To report our initial experience with three patients with pacemakers who underwent cerebral MRI studies.

Methods: The study included patients with clear clinical indications for MRI examination and who had implanted devices shown to be safe by in vitro and in vivo animal testing. In each patient the pacemaker was programmed to pacing-off. During the scan, continuous electrocardiographic telemetry, breathing rate, pulse oximetry and symptoms were monitored. Specific absorption rate was limited to 4.0 W/kg for all sequences. Device parameters were assessed before, immediately after MRI, and 1 week later.

Results: None of the patients was pacemaker dependent. During the MRI study, no device movement was felt by the patients and no episodes of inappropriate inhibition or rapid activation of pacing were observed during the scan. At device interrogation here were no significant differences in device parameters pre-, post-, and 1 week after MRI. Image quality was unremarkable in all imaging sequences used and was not influenced by the presence of the pacemaker.

Conclusion: Given appropriate precautions, MRI can be safely performed in patients with a selected permanent pacemaker. This may have significant implications for current MRI contraindications.  

Objectives: To establish the impact of breast MRI on women undergoing testing in our institution.

Methods: We analyzed 82 cases that underwent MRI between January 2001 and April 2003. Analysis appraised the clinical impact of MRI testing in cases where medical summaries were available.

Results: Studies were categorized into five indications: a) screening in high risk women (n=7), b) search for primary disease in the presence of disease (n=5), c) monitoring of chemotherapy (n=2), d) postoperative assessment of tumor bed (n=9), and e) diagnostic/characterization of primary or recurrent breast cancer (n=59). Results were defined as negative, positive or no impact on clinical management. MRI testing had a positive impact in 62 cases, affecting measurable change in 9 cases. Benefit was seen in screening, diagnosis and postoperative cases. In 15 cases, MRI stimulated investigations.

Conclusion: MRI is a valuable tool in breast imaging and affects management. Further trials are necessary to define clearly the role of MRI and to ascertain whether in cases where beneficial impact on management is noted, there is ultimate impact on outcome. 

Israel has a National Screening Program for early detection of breast cancer. The need to continue and even expand this program was recently stressed in light of the high risk in the population. However, the optimal modalities for breast cancer screening are controversial, especially for women at risk. Mammography, the established screening method, is critically examined, and molecular imaging techniques, such as magnetic resonance spectroscopy and spectroscopic imaging are explored, especially for primary breast cancer detection. MRS[1] and MRSI[2] are currently limited by their reliance on the conventional framework for data analysis in biomedical imaging, i.e., the fast Fourier transform. Recent mathematical advances in signal processing via the fast Pade transform can extract diagnostically important information, which until now has been unavailable with in vivo MRS. A clinical MRS signal illustrates the rapid and stable convergence provided by FPT[3], yielding accurate information about key metabolites and their concentrations at short acquisition times. We suggest that the next step would be to apply the FPT to in vivo MRS/MRSI signals from patients with breast cancer and to compare these to findings for normal breast tissue. The potential implications of such an optimized MRS/MRSI for breast cancer screening strategies are discussed, especially for younger women at high risk.

Gadolinium-based agents are widely used in magnetic resonance imaging as contrast agents. These agents are radio-opaque enough for diagnostic imaging of the vascular tree by using digitally subtracted images as well as for imaging of the biliary system and the urinary tract. The recommended doses for gadolinium do not impair renal function or cause adverse reactions in patients with iodine sensitivity; thus patients with such conditions can safely undergo diagnostic angiography, either by MRI angiography or by catheterization using gadolinium as contrast agent, for diagnostic and therapeutic purposes.