MRI imaging of burn dressings has a silver lining

Amanda D. Francoeur, amanda.francoeur@laurin.com

Researchers have determined that, contrary to current recommendations, the silver-containing dressings commonly used for minor to severe burn wounds do not have to be removed before a series of MRIs can be performed. Leaving the bandages on will help to reduce patient pain, stress and the threat of infection from excess changing, and will lower the cost of supplies.

Gauzes with silver additives that promote sterility and faster healing contain inserts in their packaging advising that dressings should be taken off before MRI procedures, warning of potential safety risks and distorted imaging associated with exposing the bandaged skin to MRI.

An MRI of an exposed burn wound on a pig limb (left) is shown in comparison with an MRI of the same appendage to which a silver-based burn dressing has been applied (right). The visibility of the tissue in the second view demonstrates that bandages do not have to be removed before MRI sequencing to produce clear and functional images.

Researchers at Ohio State University Medical Center’s burn center in Columbus conducted a study to determine whether the claim that leaving dressings on during the procedure increases skin temperature and interferes with image clarity is valid.

The researchers suggested that this claim was made because prior studies involving dental metals and implants, which can contain silver alloys, significantly hindered clear MR imaging. However, according to Dr. Steffen Sammet, a research scientist in the university’s department of radiology, the silver metals used for dental applications have a different composition than that of the silver additives in burn dressings.

The investigators took six standard sequences of MRI scans of pig limbs with three types of silver-based dressings – silver sulfadiazine, silver thiosulfate and silver zirconium phosphate. The bandages chosen contain the silver-based additives most commonly used in dressings on the market, Sammet said.

Each of the dressings was first applied dry to the animal tissue and then applied wet. Luxtron 790 Fluoroptic thermometers were attached between the dressings and the skin surface to track temperature variations before and during scanning. An ultrahigh-field 7-T MRI took the images.

The results verified that all dressings produced only small increases in heat during both wet and dry applications and throughout MRI sequencing. Although 3-T and 1.5-T scanners are more commonly used in clinical practice, the researchers asserted that, because these devices have lower absorption rates compared with the 7-T scanner, they would produce even lower temperature increases. In addition, the images taken with the 7-T MRI had few distortions that would render them unusable. Therefore, the researchers established that removal of any of the three silver-based topical dressings before MRI scanning is unnecessary for all burn wounds, regardless of severity.

Although animal models were used for the study, the investigators are expecting the procedure to be followed in clinical practice.

To be published in the Journal of Burn Care & Research.