An advanced magnetic resonance imaging perspective on the etiology of deep tissue injury

Abstract

Early diagnosis of deep tissue injury remains problematic due to the complicated and multifactorial nature of damage induction and the many processes involved in damage development and recovery. In this paper, we present a comprehensive assessment of deep tissue injury development and remodeling in a rat model by multiparametric magnetic resonance imaging (MRI) and histopathology. The tibialis anterior muscle of rats was subjected to mechanical deformation for 2 h. Multiparametric in vivo MRI, consisting of T, T*, mean diffusivity (MD), and angiography measurements, was applied before, during, and directly after indentation as well as at several time points during a 14-day follow-up. MRI readouts were linked to histological analyses of the damaged tissue. The results showed dynamic change in various MRI parameters, reflecting the histopathological status of the tissue during damage induction and repair. Increased T corresponded with edema, muscle cell damage, and inflammation. T* was related to tissue perfusion, hemorrhage, and inflammation. MD increase and decrease was reported on the tissue's microstructural integrity and reflected muscle degeneration and edema as well as fibrosis. Angiography provided information on blockage of blood flow during deformation. Our results indicate that the effects of a single damage-causing event of only 2 h of deformation were present up to 14 days. The initial tissue response to deformation, as observed by MRI, starts at the edge of the indentation. The quantitative MRI readouts provided distinct and complementary information on the extent, temporal evolution, and microstructural basis of deep tissue injury-related muscle damage. NEW & NOTEWORTHY We have applied a multiparametric MRI approach linked to histopathology to characterize damage development and remodeling in a rat model of deep tissue injury. Our approach provided several relevant insights in deep tissue injury. Response to damage, as observed by MRI, started at some distance from the deformation. Damage after a single indentation period persisted up to 14 days. The MRI parameters provided distinct and complementary information on the microstructural basis of the damage.

Magnetic resonance elastography of skeletal muscle deep tissue injury

“…The response of skeletal muscle deep tissue injury is known to follow a well‐known pathway with multiple overlapping pathological processes . Several studies have concluded that a single MRI contrast cannot capture all of the pathological processes involved in skeletal muscle damage, which therefore warrants a multi‐parametric approach using several complementary MRI readouts to characterize different aspects of injury and recovery.…”

“…Decrease in shear stiffness values associated with diseased skeletal muscles, eg in myositis and hyperthyroid myopathy, was reported previously . With the histopathological remodeling processes of deep tissue injury in mind, as previously reported by Nelissen et al, the lower shear modulus values likely originate from the moderate to severe degeneration of the TA muscle with massive necrosis, hemorrhage, edema, and inflammation . The macroscopic MRE shear wave has shown to be highly sensitive to these changes in tissue microstructure based on the distribution and presence of microscopic scatterers .…”

“…One of the well‐established animal models of deep tissue injury involves the deformation of the rat tibialis anterior (TA) muscle with a custom loading device that can be placed in a MRI scanner for imaging during the development of the damage . Several MRI and histopathologic readouts were employed to provide a comprehensive understanding of the damage development, recovery, and regeneration in this model . It was found that the initial tissue response to deformation started at some distance from the center of indentation, affecting a relatively large area.…”

“…Diffusion‐weighted imaging is sensitive to the integrity of the tissue microstructure and reflects muscle degeneration and edema, as well as extracellular matrix remodeling during the muscle remodeling processes. Time of flight MR angiography provided information on occlusion of blood flow during the indentation period . Furthermore, the use of an animal‐specific FEA model, for which the geometry and loading conditions were derived from MRI, supplied estimations of the local tissue deformations .…”

Physiological processes of inflammation and edema initiated by sustained mechanical loading in subcutaneous tissues: A scoping review

“…Biomarkers are indicators of internal physiological processes (e.g., lactate levels indicating an anaerobe metabolism) and can be used to assess the integrity of soft tissues . Concerning pressure ulcers, two main physiological processes, described in histological studies, are inflammation and edema (or interstitial fluid accumulation) . One study has demonstrated the potential of C‐reactive protein (CRP) levels in blood samples as a chemical biomarker of inflammation associated with muscle damage in deep tissue injury .…”