Ultra Structurally Based Impedance Model for Oral Cancer Detection

abstract: This research investigated using impedance as a minimally invasive oral cancer-screening tool by modeling healthy and diseased tissue. This research developed an ultra-structurally based tissue model for oral mucosa that is versatile enough to be easily modified to mimic the passive electrical impedance responses of multiple benign and cancerous tissue types. This new model provides answers to biologically meaningful questions related to the impedance response of healthy and diseased tissues. This model breaks away from the old empirical top down "black box" Thèvinin equivalent model. The new tissue model developed here was created from a bottom up perspective resulting in a model that is analogous to having a "Transparent Box" where each network element relating to a specific structural component is known. This new model was developed starting with sub cellular ultra-structural components such as membranes, proteins and electrolytes. These components formed the basic network elements and topology of the organelles. The organelle networks combine to form the cell networks. The cell networks combine to make networks of cell layers and the cell layers were combined into tissue networks. This produced the complete "Transparent Box" model for normal tissue. This normal tissue model was modified for disease based on the ultra-structural pathology of each disease. The diseased tissues evaluated include cancers type one through type three; necrotic-inflammation, hyperkeratosis and the compound condition of hyperkeratosis over cancer type two. The impedance responses for each of the disease were compared side by side with the response of normal healthy tissue. Comparative evidence from the models showed the structural changes in cancer produce a unique identifiable impedance "finger print." The evaluation of the "Transparent Box" model for normal tissues and diseased tissues show clear support for using comparative impedance measurements as a clinical tool for oral cancer screening.Dissertation/Thesisnormal oral mucosal tissue modelcancer type 1 oral mucosal tissue modelcancer type 2 oral mucosal tissue modelcancer type 3 oral mucosal tissue modelhyperkeratosis oral mucosal tissue modelhyperkeratosis over cancer type 2 oral mucosal tissuenecrotic inflammation oral tissue modelPh.D. Electrical Engineering 201

Myocardial electrical impedance as a metric of completeness for radiofrequency ablation lesions

Radiofrequency (RF) ablation has emerged as a promising curative therapy for atrial fibrillation and other supraventricular tachyarrhythmias. Most RF ablation procedures create a pattern of linear lesions that either isolate ectopic focal triggers or divide the atria into functional regions too small to sustain macroreentry. It is thought that these linear lesions must be complete (i.e. both continuous and transmural) in order to block arrhythmic conduction and to avoid creation of a more proarrhythmic substrate. Currently, most ablation endpoints employ pacing-based metrics of lesion completeness that rely upon active tissue properties and are therefore limited by transient or delayed effects of RF on conduction. Myocardial electrical impedance is a passive tissue property that may provide an alternative intraoperative metric that overcomes certain limitations of pacing-based endpoints. Because RF ablation markedly alters the tissue, it was hypothesized that linear ablation lesions change myocardial impedance. Custom instrumentation and data acquisition software were developed to measure impedance using the four-electrode method. Computer simulations were performed to determine the effect of electrode size on four-electrode impedance measurement. Receiver operating characteristic analysis was used to assess the diagnostic accuracy of both resistivity and translesion stimulus-excitation delay to predict completeness of individual lesions. Lesions (n=50) were created in the ventricles of 18 Langendorff-perfused rabbit hearts using a linear epicardial ablation probe. Lesions were either continuous and transmural (n=25), noncontinuous (n=18), or nontransmural (n=7), which was verified histologically after staining with 2,3,5-triphenyltetrazolium chloride. Subthreshold AC current (10 μA, 1 kHz) and four electrodes in a linear array across the lesion were used to measure magnitude and phase of the tissue impedance. When a continuous and transmural lesion was produced, the resistivity increased 26-58 Ωcm (p<0.02). When a noncontinuous or nontransmural lesion was produced, changes in resistivity were markedly smaller and did not reach statistical significance. No changes in phase shift were found. The resistive component of myocardial impedance may provide a useful intraoperative metric of lesion completeness for RF ablation procedures

Composition corporelle du chien par bioimpédancemétrie : validation d'équations prédictives

Objectives—To develop equations for prediction of total body water (TBW) content in unsedated dogs by combining impedance and morphological variables, and to compare the results of those equations with TBW content determined by deuterium dilution (TBWd). Then to investigate whether these equations were predictive of TBW in various canine breeds.Animals—26 healthy laboratory adult Beagles and 13 healthy adult pet dogs of various breeds.Procedures—TBW content was determined directly by deuterium dilution and indirectly with equations developed from measurements obtained by use of a portable bioelectric impedance device and morphological variables.Results—Impedance and morphological data from 16 of the 26 Beagle dogs were used to determine coefficients for the following 2 equations: TBW1 = –0.019(BL2/R) + –0.199(RC + AC) + 0.996W + 0.081H + 12.31; and TBW2 = 0.048(BL2/R) + –0.144(RC +AC) + 0.777W + 0.066H + 0.031X + 7.47, where AC is abdominal circumference, H is height, BL is body length, R is resistance, RC is rib cage circumference, W is body weight; and X is reactance. Results for TBW1 (R21 = 0.843) and TBW2 (R22 = 0.816) were highly correlated with the TBWd. When the equations were validated with data from the remaining 10 dogs, the respective mean differences between TBWd and TBW1 and TBW2 were 0.17 and 0.11 L, which equated to a nonsignificant underestimation of TBW content by 2.4% and 1.6%, respectively. Applying the two equations to dogs of various breeds showed they are inaccurate to estimate TBW content.Conclusions and Clinical Relevance—Results indicated that impedance and morphological data can be used to accurately estimate TBW content in adult Beagles. This method of estimating TBW content is less expensive and easier to perform than is measurement of TBWd, making it appealing for daily use in veterinary practice. However, the proposed equations need to be modified including morphological parameters such as body size and shape in a first approach. As in humans, morphological-specific equations have to be developed and validated.Objectifs : valider des équations prédictives de la teneur en eau totale (TBW) chez le chien vigile de race beagle par bioimpédancemétrie monofréquence à 50 kHz, en comparaison avec la méthode de référence de dilution au deutérium. Ces équations seront ensuite appliquées à différentes races de chiens afin de vérifier leur validité chez tous les formats de chiens.Animaux : 26 chiens de laboratoire de race beagle et 13 chiens de propriétaires de diverses races. Méthodes : TBW est déterminée par la méthode de référence de dilution à l’eau deutérée et indirectement par l’utilisation d’équations prédictives établies à partir de mesures morphologiques et des mesures électriques (résistance et réactance) obtenues au moyen d’un bioimpédancemètre. Résultats : Les données obtenues chez 16 des 26 beagle a permis d’établir, par régression linéaire, deux équations prédictives de la teneur en eau totale suivantes : TBW1 = –0.019(BL2/R) + –0.199(RC + AC) + 0.996W + 0.081H + 12.31; et TBW2 = 0.048(BL2/R) + –0.144(RC +AC) + 0.777W + 0.066H + 0.031X + 7.47, où AC est le périmètre abdominal, H la hauteur au garrot, BL la longueur du corps, R la résistance, RC le périmètre thoracique , W le poids; and X la réactance. Chez les 10 beagles restants, TBW calculée par les équations TBW1 et TBW2 et celle obtenue par la méthode de dilution sont fortement corrélées (R21 = 0.843 ; R22 = 0.816). La 1ère et la 2ème équations sous-estiment de façon non significative la TBW de respectivement 2.4% and 1.6%. Cependant, l’application de ces formules à des chiens de diverses races ne permet pas l’estimation correcte de la TBW par rapport à la méthode de référence.Conclusion : Cette étude montre qu’il est possible et facile d’utiliser la bioimpédance chez le chien vigile. Deux équations prédictives de la TBW ont été développées et validées chez le beagle mais ne sont pas applicables en l’état à d’autres races de chien. La diversité morphologique des races canines obligent à adapter ces équations en fonction de paramètres de conformation et de format