Assessment of demineralized tooth lesions using optical coherence tomography and other state-of-the-art technologies: a review.

Tooth demineralization is one of the most common intraoral diseases, encompassing (1) caries caused by acid-producing bacteria and (2) erosion induced by acid of non-bacterial origin from intrinsic sources (e.g. stomach acid reflux) and extrinsic sources (e.g. carbonated drinks). Current clinical assessment based on visual-tactile examination and standardized scoring systems is insufficient for early detection. A combination of clinical examination and technology is therefore increasingly adapted. This paper reviews various procedures and technologies that have been invented to diagnose and assess the severity of tooth demineralization, with focus on optical coherence tomography (OCT). As a micron-resolution non-invasive 3D imaging modality, variants of OCT are now available, offering many advantages under different working principles for detailed analytical assessment of tooth demineralization. The roles, capabilities and impact of OCT against other state-of-the-art technologies in both clinical and research settings are described. (139 words).

Assessment of infarct-specific cardiac motion dysfunction using modeling and multimodal magnetic resonance merging.

PURPOSE: To propose a cardiac motion tracking model that evaluates wall motion abnormality in postmyocardial infarction patients. Correlation between the motion parameter of the model and left ventricle (LV) function was also determined. MATERIALS AND METHODS: Twelve male patients with post-ST elevation myocardial infarction (post-STEMI) and 10 healthy controls of the same gender were recruited to undergo cardiac magnetic resonance imaging (MRI) using a 1.5T scanner. Using an infarct-specific LV division approach, the late gadolinium enhancement (LGE) MRI images were used to divide the LV on the tagged MRI images into infarct, adjacent, and remote sectors. Motion tracking was performed using the infarct-specific two-parameter empirical deformable model (TPEDM). The match quality was defined as the position error computed using root-mean-square (RMS) distance between the estimated and expert-verified tag intersections. The position errors were compared with the ones from our previously published fixed-sector TPEDM. Cine MRI images were used to calculate regional ejection fraction (REF). Correlation between the end-systolic contraction parameter (αES ) with REF was determined. RESULTS: The position errors in the proposed model were significantly lower than the fixed-sector model (P < 0.01). The median position errors were 0.82 mm versus 1.23 mm. The αES correlates significantly with REF (r = 0.91, P < 0.01). CONCLUSION: The infarct-specific TPEDM combines the morphological and functional information from LGE and tagged MRI images. It was shown to outperform the fixed-sector model in assessing regional LV dysfunction. The significant correlation between αES and REF added prognostic value because it indicated an impairment of cardiac function with the increase of infarct transmurality. LEVEL OF EVIDENCE: 3 J. Magn. Reson. Imaging 2017;45:525-534.

Regional assessment of LV wall in infarcted heart using tagged MRI and cardiac modelling.

A segmental two-parameter empirical deformable model is proposed for evaluating regional motion abnormality of the left ventricle. Short-axis tagged MRI scans were acquired from 10 healthy subjects and 10 postinfarct patients. Two motion parameters, contraction and rotation, were quantified for each cardiac segment by fitting the proposed model using a non-rigid registration algorithm. The accuracy in motion estimation was compared to a global model approach. Motion parameters extracted from patients were correlated to infarct transmurality assessed with delayed-contrast-enhanced MRI. The proposed segmental model allows markedly improved accuracy in regional motion analysis as compared to the global model for both subject groups (1.22-1.40 mm versus 2.31-2.55 mm error). By end-systole, all healthy segments experienced radial displacement by ~25-35% of the epicardial radius, whereas the 3 short-axis planes rotated differently (basal: 3.3°; mid: -1° and apical: -4.6°) to create a twisting motion. While systolic contraction showed clear correspondence to infarct transmurality, rotation was nonspecific to either infarct location or transmurality but could indicate the presence of functional abnormality. Regional contraction and rotation derived using this model could potentially aid in the assessment of severity of regional dysfunction of infarcted myocardium.

Imaging of skin birefringence for human scar assessment using polarization-sensitive optical coherence tomography aided by vascular masking.

We demonstrate the in vivo assessment of human scars by parametric imaging of birefringence using polarization-sensitive optical coherence tomography (PS-OCT). Such in vivo assessment is subject to artifacts in the detected birefringence caused by scattering from blood vessels. To reduce these artifacts, we preprocessed the PS-OCT data using a vascular masking technique. The birefringence of the remaining tissue regions was then automatically quantified. Results from the scars and contralateral or adjacent normal skin of 13 patients show a correspondence of birefringence with scar type: the ratio of birefringence of hypertrophic scars to corresponding normal skin is 2.2 ± 0.2 (mean ± standard deviation ), while the ratio of birefringence of normotrophic scars to normal skin is 1.1 ± 0.4 . This method represents a new clinically applicable means for objective, quantitative human scar assessment.

Assessment of human burn scars with optical coherence tomography by imaging the attenuation coefficient of tissue after vascular masking.

The formation of burn-scar tissue in human skin profoundly alters, among other things, the structure of the dermis. We present a method to characterize dermal scar tissue by the measurement of the near-infrared attenuation coefficient using optical coherence tomography (OCT). To generate accurate en face parametric images of attenuation, we found it critical to first identify (using speckle decorrelation) and mask the tissue vasculature from the three-dimensional OCT data. The resulting attenuation coefficients in the vasculature-masked regions of the dermis of human burn-scar patients are lower in hypertrophic (3.8±0.4 mm(-1)) and normotrophic (4.2±0.9 mm(-1)) scars than in contralateral or adjacent normal skin (6.3±0.5 mm(-1)). Our results suggest that the attenuation coefficient of vasculature-masked tissue could be used as an objective means to assess human burn scars.

In vivo assessment of human burn scars through automated quantification of vascularity using optical coherence tomography.

In scars arising from burns, objective assessment of vascularity is important in the early identification of pathological scarring, and in the assessment of progression and treatment response. We demonstrate the first clinical assessment and automated quantification of vascularity in cutaneous burn scars of human patients in vivo that uses optical coherence tomography (OCT). Scar microvasculature was delineated in three-dimensional OCT images using speckle decorrelation. The diameter and area density of blood vessels were automatically quantified. A substantial increase was observed in the measured density of vasculature in hypertrophic scar tissues (38%) when compared against normal, unscarred skin (22%). A proliferation of larger vessels (diameter≥100 µm) was revealed in hypertrophic scarring, which was absent from normal scars and normal skin over the investigated physical depth range of 600 µm. This study establishes the feasibility of this methodology as a means of clinical monitoring of scar progression.

Enhanced skin permeation and hydration by magnetic field array: preliminary in-vitro and in-vivo assessment.

OBJECTIVES: The aim of the study was determine the effect of magnetic film array technology on the skin permeation of urea. METHODS: A 5% urea gel was applied to human epidermal membrane in vitro and human skin in vivo. Application of gel with magnetic film array and plastic occlusive film was compared with application of gel with a plastic occlusive film and non-magnetic film. In-vitro epidermal penetration was determined using a Franz-type diffusion system. In-vivo permeation and changes in epidermal properties were visualised by optical coherence tomography. KEY FINDINGS: The mean cumulative permeation of urea over 2 h for magnetic film array application was 89.54 +/- 7.34 microg/cm(2) as compared with 20.83 +/- 2.02 microg/cm(2) for passive occluded application (mean +/- SEM, n = 9/8), representing greater than 4-fold increase over the 2-h application time period. Administration of urea with the magnetic film array resulted in the lag time being reduced from 40.58 +/- 3.98 to 21.13 +/- 6.27 min (P < 0.02), while steady state flux increased from 0.24 +/- 0.03 to 0.75 +/- 0.06 microg/cm(2) per min (P < 0.0001). Under active occlusion, the relative change in epidermal thickness as determined by optical coherence tomography increased by 16 and 11% at 30 and 60 min, respectively. CONCLUSIONS: Administration with a novel magnetic film array technology provided enhanced skin penetration of urea and increased epidermal hydration when compared with administration under an occlusive film only.