It seems not so long ago it was normal to know someone that needed "exploratory surgery." This type of procedure was a "search-and-destroy" method used to diagnose diseases with unknown etiology. With advancements in medicine, it is no longer necessary to resort to such drastic measures.

Radiologic procedures, specifically MRI, play a major role in early diagnosis and treatment. 2011 has proved to be a memorable year with significant advancements in MR enterography (MRE) and safety.

MR enterography

In years past, MR has been a modality almost exclusively dedicated to neurological studies of the brain and spine. Advancements in technology today lend to quality MR imaging of the abdomen and bowel as well. Ultrafast imaging and improved gating and triggering minimize motion challenges that were previously roadblocks for a successful exam.

MRE is a study focused on the small bowel using a non-invasive method for diagnosing and monitoring inflammatory bowel diseases. Crohn's disease, a common inflammatory bowel disease, is often diagnosed in young adults.

CT has been the modality used for the non-invasive assessment in Crohn's patients; however, MR is gaining ground for several reasons. First and foremost, MR does not use ionizing radiation. Eliminating concerns with radiation, especially high doses used in CT, is critical, as patients with bowel diseases have multiple diagnostic evaluations over their lifespan. This leads to unusually high levels of radiation exposure.

MR also provides a high degree of specificity in the bowel, showing high contrast differences in soft tissues. In overcoming artifacts with advanced technology, MR image quality shows no significant clinical difference in the information provided when comparing MR and CT.

Coronal T2 Haste image. image/courtesy Kristan Harrington

Children's Healthcare of Atlanta performs MRE exams commonly on young adults to diagnosis, assess extent, and review for complications for various inflammatory bowel diseases. The preparation for the study involves 24 hours of fluids, laxatives, and fasting prior to the study. Upon arrival at the MR department, the patient drinks a negative contrast agent allowing better visualization of the bowel. Once the agent is ingested, the patient receives an injection of scopolamine to slow peristalsis and is positioned prone.

Images are acquired on the 3T system, allowing greater flexibility in protocol optimization with the inherent increase in available signal. A series of breathhold sequences (HASTE) and respiratory triggered scans are acquired. A dynamic series (VIBE) with a gadolinium contrast agent is performed. The study takes just under an hour and is well-tolerated by most patients.

MR safety

February 2011 proved to be an important time for MR. The Food and Drug Administration approved the first MR conditional pacemaker for clinical imaging. Seventeen years of research and design finally came to fruition making it possible to provide more accurate and timely diagnosis for the aging population. This pacemaker, Revo™ by Medtronic, is part of the MR SureScan^® Pacing System. If all conditions are met, the patient may have the MR study.

Prior to this approval, patients with pacemakers only could be scanned under extreme risk-versus-benefit circumstances. Pacemakers created serious hazards in the MR environment: heating, torque, and device malfunction could occur with a pacemaker not designed for MR.

Why is this approval so important? People over age 65 are twice as likely to present with a clinical need for an MR scan. Approximately 1.5 million individuals have implanted pacemakers, and of those, more than 85 percent are over 65.

MR provides an edge over other modalities for several reasons in diagnosing diseases. MR does not use ionizing radiation and provides excellent tissue contrast. This high contrast resolution is especially helpful in imaging of soft tissues. The option to have an MR in many cases allows for faster diagnosis, better determination of the extent of disease, and enhanced treatment plans along with a more accurate prognosis of many diseases.

Several conditions must be met prior to scanning the patient. The patient should arrive with an ID card that clearly states the implant date, Revo pacemaker, 5086 leads, and SureScan software. The pacemaker has unique radiopaque markings in the extreme case requiring an X-ray. Once this criteria is verified, the pacemaker is programmed for the MR study.

The patient must be scanned on a 1.5T cylindrical bore MR system that maintains a normal SAR mode (less than 2W/kg) and does not exceed 200 T/m/s slew rates. These requirements are easily met with almost all clinically relevant sequences. The patient centering may not be between C1 and T12. Scanning in this area is not prohibited, only placing the isocenter.

The FDA approval of this pacemaker will change the approach for safety. Now if a patient checks "yes" for a pacemaker, there will be additional questions instead of the historical "no." MR is changed forever.

Kristan Harrington, MBA, RT(R)(MR), is an associate on faculty at the School of Medicine, Emory University, Atlanta.