Grzegorz Tatoń

Application of thermography for the assessment of allergen-induced skin reactions

PURPOSE The allergic response is commonly identified and assessed by skin testing. The usual method to quantify skin reactions is to mark wheal and erythema regions and assess the surfaces affected by the reactions; however, subjective interpretation of the outcome may cause errors. Skin thermography supplemented by a mathematical model based on the pathophysiology of heat generation was evaluated as a novel, objective, and sensitive indicator of the skin prick test result. METHODS TH measurements were performed simultaneously with routine skin prick tests for 24 patients. Eight allergens and control (histamine) were examined. Thermographic images of both forearms were acquired every 70 s from 0 to 910 s after skin prick and analyzed with the use of dedicated software. The introduction of potential allergens and histamine at sites on the skin induces a complex sequence of events known as the local inflammatory response. The crucial steps of the process have been considered in the model. In the model, the authors assumed that the reaction takes place in the thin skin layer and that histamine is the principal mediator of the allergic reaction. Histamine penetrates the skin and binds to receptors of nearby capillaries and venules. The engorged vessels are, in turn, responsible for skin redness and an increase in skin temperature. RESULTS The model parameters were determined by fitting the analytical solutions to the spatiotemporal distributions of the differences between measured and baseline temperatures. The model reproduces experimental data very well. The coefficient of determination ranged from 0.805 to 0.995. Seven model parameters were tested to find the optimal marker of the intensity and kinetics of the allergic reaction. The parameter which quantifies a release of histamine after allergen injection has appeared to be the best indicator of the allergen-induced response. The parameter correlates with the routine assessment based on wheal and erythema areas (correlation coefficient = 0.98). CONCLUSIONS It was demonstrated that the thermographic measurements supplemented by the mathematical model offer a new approach to the quantification of allergen-induced skin reactions. Despite the applied simplifications, the proposed model reflected properly the mechanism of heat generation during skin prick test. Moreover, the continuous recording of the skin temperature represents an additional possibility to investigate the mechanism of the allergic reaction.

Combining areal DXA bone mineral density and vertebrae postero-anterior width improves the prediction of vertebral strength

ObjectiveAreal bone mineral density (aBMD) measured by dual-energy X-ray absorptiometry (DXA) is an important determinant of bone strength (BS), despite the fact that the correlation between aBMD and BS is relatively weak. Parameters that describe BS more accurately are desired. The aim of this study was to determine whether the geometrical corrections applied to aBMD would improve its ability for BS prediction. We considered new parameters, estimated from a single DXA measurement, as well as BMAD (bone mineral apparent density) reported in the literature.Materials and methodsIn vitro studies were performed with the L3 vertebrae from 20 cadavers, which were studied with DXA and quantitative computed tomography (QCT). A mechanical strength assessment was carried out. Two new parameters were introduced: vBMDmin=aBMDWPAmin

Application of geometrical measurements in the assessment of vertebral strength.

vBM{D}_{min}=\frac{ aBMD}{W_{PA}^{min}}

Automatical Syndesmophyte Contour Extraction from Lateral C Spine Radiographs

and vBMDav=aBMDWPAav

Analysis of renal calculi structure with the use of X-ray microtomography

vBM{D}_{av}=\frac{ aBMD}{W_{PA}^{av}}

Application of digital imaging for quantitative assessment of wheal formation

(WPAmin —minimal vertebral body width in postero-anterior (PA) view, WPAav — average PA vertebral body width). Volumetric BMD measured by QCT (vBMD), aBMD, BMAD, vBMDmin, and vBMDav were correlated to ultimate load and ultimate stress (Pmax) to find the best predictor of vertebrae BS.ResultsThe coefficients of correlation between Pmax and vBMDmin, vBMDav, as well as BMAD, were r = 0.626 (p = 0.005), r = 0.610 (p = 0.006) and r = 0.567 (p = 0.012), respectively. Coefficients for vBMD and aBMD are r = 0.648 (p = 0.003) and r = 0.511 (p = 0.03), respectively.ConclusionsOur results showed that aBMD normalized by vertebrae dimensions describes vertebrae BS better than aBMD alone. The considered indices vBMDav, vBMDmin, and BMAD can be measured in routine PA DXA and considerably improve BS variability prediction. vBMDmin is superior compared to vBMDav and BMAD.