Assessing burn wound depth using in vitro nuclear magnetic resonance (NMR)

There is no accurate noninvasive method for differentiating between partial-thickness and full-thickness cutaneous burn wounds. Full-thickness burns (FTB) result in slower resorption of wound edema than partial thickness burns (PTB). Since proton NMR parameters, particularly the T1 relaxation time, correlate with tissue water content (TWC), the present study determined whether proton NMR could distinguish PTB from FTB. An area of upper dorsum (approximately 15% BSA) of 35 adult rats was immersed in boiling water for either 3 sec (PTB) or 10 sec (FTB). In 10 control rats, the same area was immersed in room temperature water. Rats were sacrificed at either 3 or 48 hr after burn, and skin samples were analyzed to determine spin-lattice (T1) and spin-spin (T2) relaxation times. TWC was then measured gravimetrically by desiccation. Both T1 and T2 times significantly correlated with TWC (T1: r = 0.74, P less than 0.0001; T2: r = 0.75; P less than 0.0001). Both PTB and FTB resulted in significant elevations of T1, T2, and TWC 3 hr after injury (P less than 0.001). At 48 hr postburn the T1, T2, and TWC of the PTB group had decreased to control values (P less than 0.05), while all FTB parameters remained significantly elevated as compared to both the control and the 48-hr PTB parameters (P less than 0.001). In vitro NMR measurements distinguish PTB from FTB in this rat model within 48 hr. These data provide a basis for investigating in vitro NMR techniques for the noninvasive assessment of burn wound depth.