Studies of immediate skin reactions are important to understand the underlying biological mechanisms involved in traumatic or chemical damage to the skin. In this study the spatial and spectral information provided by hyperspectral images was used to identify and characterize non-penetrating skin injuries in a porcine model. A hyperspectral imaging system (Hyspex, Norsk Elektro Optikk AS) was used to monitor the temporal development of minor skin injuries in an anesthetized Norwegian domestic pig. Hyperspectral data were collected in the wavelength range 400-1000 nm (VNIR), with a spectral sampling interval of 3.7 nm. The measurements were initiated immediately after inflicting the injury, and were repeated at least five times at each site with irregular frequency. The last measurement was performed 4 hours after injury. Punch biopsies (5 mm), were collected from adjacent normal skin, and at the center and the margin of each injury. The study was approved by the national animal research authority. The hyperspectral data were analyzed with respect to oxy- and deoxyhemoglobin, and erythema index. The skin biopsies were examined to determine the extent of skin damage in the bruised zones. Preliminary results show that hyperspectral imaging allows discrimination between traumatized skin and normal skin in an early phase. The extent and location of the hemorrhages can be determined from hyperspectral images. These findings might contribute to a better understanding of immediate skin reactions to minor trauma, and thereby the development of a better diagnostic modality for non-penetrating skin injuries in forensic medicine.
Determining the cause of an injury and the force behind the impact may be of crucial importance in a court case.
For non-penetrating soft tissue injuries there is a lack of information available in the literature. In this study
controlled bruises were inflicted on an anesthetized pig by high speed, low-weight paintball projectiles (diameter
17.1 mm, weight 3.15 g). The speed of the object and the impact itself were monitored using a high speed
camera. Punch biopsies (5 mm) were collected from the injury sites. A red and purple ring with a diameter of
1.5 cm appeared on the skin within 30 seconds after the paintball impact. The ring was visually fully established
after 5-10 minutes. Numerical finite element simulations performed with ABAQUS\Explicit showed a build up of
shear stresses in the skin where the ring formed. Biopsies demonstrated severe dermal vessel damage in the same
area. It is concluded that considerable shear stresses during the impact will create dermal vessel damage and
thereby cause a visible bruise. Larger forces are required for compressive stresses to inflict equivalent vascular
An objective method for dating of soft tissue injuries is highly desired in forensic medicine. To achieve this, obtaining a fundamental understanding of extravascular blood behavior is necessary. Porcine blood mixed with fluorescein was inserted subcutaneously on an anaesthetized pig. The fluorescence build-up was measured as a function of time, using a fiber probe setup. Fluorescence measurements proved to be a suitable tool for
monitoring the temporal distribution of fluid in a subcutaneous hemorrhage. Reasonable values for the fluid velocity was obtained by monitoring the fluorescein distribution around the infusion point. Further theoretical work and development of the experimental technique is necessary to obtain a good understanding of subcutaneous transport of blood.
A reliable theoretical model is essential to reveal information from measured reflectance spectra. Currently, Monte Carlo simulation (MC) is the most popular technique to retrieve optical tissue parameters. However, optical diffusion theory provides an analytic approach that might supersede MC methods due to faster, more efficient algorithms. Diffuse skin reflectance in the 400-800 nm wavelength range was simulated by Monte Carlo and diffusion theory. The impact of detection geometry and source distribution was investigated, and experimental data from bruised and normal skin were fitted using a three layer diffusion model. Spectra from diffusion theory were within 5% of the MC results, and the fit between the two methods was further improved by scaling the dermal absorption parameters with a constant factor. The measurement geometry was found to be of minor impact. Diffusion theory was found to have wide applicability due to fast, efficient algorithms that allow efficient evaluation of experimental data.
Determining the age of injuries is an important aspect of forensic medicine. Currently, visual inspection and colorimetric measurements are the most common techniques used to assess the age of bruises on a victim's body. Bruises are caused by trauma to the skin and
vasculature, and the color will depend on the age, depth, and anatomic site of the hemorrhage. Breakdown products of hemoglobin e.g. biliverdin and bilirubin possess various colors, which can be determined spectrometrically. This study presents
reflection spectra collected from bruises in otherwise healthy subjects. A total of 73 spectra of 25 bruises were measured on 13 individuals in the 400-850 nm wavelength region. All injuries were caused by sports activities such as judo and soccer. The bruises were classified according to visual appearance, bilirubin content, oxygenation, and age of the injury. Only bruises with known age and cause were included in the study. Spectral changes of each hematoma were recorded over several days. Preliminary results show large variation in the spectra, caused by differences in age and depth of the bruises. This data may provide a basis for developing an algorithm to determine the age of injuries in e.g. child abuse cases.