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 (∼ 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 < 0.0001; T₂: r = 0.75; P < 0.0001). Both PTB and FTB resulted in significant elevations of T₁, T₂, and TWC 3 hr after injury (P > 0.001). At 48 hr postburn the T₁, T₂, and TWC of the PTB group had decreased to control values (P > 0.05), while all FTB parameters remained significantly elevated as compared to both the control and the 48-hr PTB parameters (P < 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.