Effects of Articular Cartilage Constituents on Phosphotungstic Acid Enhanced Micro-Computed Tomography

Contrast-enhanced micro-computed tomography (CE mu CT) with phosphotungstic acid (PTA) has shown potential for detecting collagen distribution of articular cartilage. However, the selectivity of the PTA staining to articular cartilage constituents remains to be elucidated. The aim of this study was to investigate the dependence of PTA for the collagen content in bovine articular cartilage. Adjacent bovine articular cartilage samples were treated with chondroitinase ABC and collagenase to degrade the proteoglycan and the collagen constituents in articular cartilage, respectively. Enzymatically degraded samples were compared to the untreated samples using CE mu CT and reference methods, such as Fourier-transform infrared imaging. Decrease in the X-ray attenuation of PTA in articular cartilage and collagen content was observed in cartilage depth of 0-13% and deeper in tissue after collagen degradation. Increase in the X-ray attenuation of PTA was observed in the cartilage depth of 13- 39% after proteoglycan degradation. The X-ray attenuation of PTA-labelled articular cartilage in CE mu CT is associated mainly with collagen content but the proteoglycans have a minor effect on the X-ray attenuation of the PTA-labelled articular cartilage. In conclusion, the PTA labeling provides a feasible CE mu CT method for 3D characterization of articular cartilage.Peer reviewe

An Automatic Regularization Method : An Application for 3-D X-Ray Micro-CT Reconstruction Using Sparse Data

X-ray tomography is a reliable tool for determining the inner structure of 3-D object with penetrating X-rays. However, traditional reconstruction methods, such as Feldkamp-Davis-Kress (FDK), require dense angular sampling in the data acquisition phase leading to long measurement times, especially in X-ray micro-tomography to obtain high-resolution scans. Acquiring less data using greater angular steps is an obvious way for speeding up the process and avoiding the need to save huge data sets. However, computing 3-D reconstruction from such a sparsely sampled data set is difficult because the measurement data are usually contaminated by errors, and linear measurement models do not contain sufficient information to solve the problem in practice. An automatic regularization method is proposed for robust reconstruction, based on enforcing sparsity in the 3-D shearlet transform domain. The inputs of the algorithm are the projection data and a priori known expected degree of sparsity, denoted as 0 <C-prPeer reviewe

3D morphometric analysis of calcified cartilage properties using micro-computed tomography

OBJECTIVE: Our aim is to establish methods for quantifying morphometric properties of calcified cartilage (CC) from micro-computed tomography (muCT). Furthermore, we evaluated the feasibility of these methods in investigating relationships between osteoarthritis (OA), tidemark surface morphology and open subchondral channels (OSCCs). METHOD: Samples (n = 15) used in this study were harvested from human lateral tibial plateau (n = 8). Conventional roughness and parameters assessing local 3-dimensional (3D) surface variations were used to quantify the surface morphology of the CC. Subchondral channel properties (percentage, density, size) were also calculated. As a reference, histological sections were evaluated using Histopathological osteoarthritis grading (OARSI) and thickness of CC and subchondral bone (SCB) was quantified. RESULTS: OARSI grade correlated with a decrease in local 3D variations of the tidemark surface (amount of different surface patterns (rs = -0.600, P = 0.018), entropy of patterns (EP) (rs = -0.648, P = 0.018), homogeneity index (HI) (rs = 0.555, P = 0.032)) and tidemark roughness (TMR) (rs = -0.579, P = 0.024). Amount of different patterns (ADP) and EP associated with channel area fraction (CAF) (rp = 0.876, P < 0.0001; rp = 0.665, P = 0.007, respectively) and channel density (CD) (rp = 0.680, P = 0.011; rp = 0.582, P = 0.023, respectively). TMR was associated with CAF (rp = 0.926, P < 0.0001) and average channel size (rp = 0.574, P = 0.025). CC topography differed statistically significantly in early OA vs healthy samples. CONCLUSION: We introduced a mu-CT image method to quantify 3D CC topography and perforations through CC. CC topography was associated with OARSI grade and OSCC properties; this suggests that the established methods can detect topographical changes in tidemark and CC perforations associated with OA

Quantification of osteochondral tissue modifications during osteoarthritis using micro-computed tomography

Abstract Osteoarthritis (OA) is a heterogenic joint disease significantly affecting the quality of life of a patient, causing pain and disability. OA causes degenerative changes to the structure and composition of articular cartilage and subchondral bone. Currently, effective treatments for OA are limited, partly due to limitations in defining the imaging biomarkers of early OA. Improvement of imaging modalities in OA research and clinical setup is a requirement for quantitating early OA-related tissue features. In the clinical and preclinical setup, computed tomography (CT) enables imaging of bone and, using specific contrast agents, articular cartilage. The aim of this study is to create and validate novel micro-computed tomography (&#956;CT) methods to quantify OA-related features and modifications in articular cartilage and subchondral bone. Contrast-enhanced &#956;CT methods for imaging the collagen (phosphotungstic acid (PTA) and phosphomolybdic acid (PMA)) and GAG (CA4+) content of the articular cartilage in vitro were validated against various reference methods measuring the biochemical composition of articular cartilage. To improve the &#956;CT imaging of subchondral bone, grey-level co-occurrence matrix (GLCM) based analysis of sub-resolution features of subchondral bone was introduced. In addition, to test the translatability of the GLCM-based analysis to clinical resolution, sub-resolution features extracted from clinical cone-beam CT were validated against the subchondral bone morphometrics from the &#956;CT. PTA showed stronger association with the collagen content of the articular cartilage compared to PMA. PTA was also associated with collagen content even in degraded articular cartilage. CA4+ distribution was found to accumulate in chondrons and surrounding areas, suggesting that it is a prominent contrast agent for high-resolution &#956;CT studies of chondrocytes. The GLCM-based analysis of subchondral bone provided information on cellular structure from &#956;CT images and trabecular bone micro-structures from clinical CT images. In conclusion, &#956;CT imaging can provide quantitative information on the collagen content and chondrons of articular cartilage, as well as on osteocytes in subchondral bone. The methods presented here extend the tools for researchers to quantify osteochondral tissue modifications in OA. Furthermore, the developed image processing tools could be translatable to the clinical CT.Tiivistelmä Nivelrikko on heterogeeninen niveltauti, joka huonontaa yksilön elämän laatua aiheuttaen kipua ja liikuntakyvyttömyyttä. Nivelrikko aiheuttaa nivelkudosten rappeumaa vaikuttaen mm. ruston ja rustonalaisen luun rakenteeseen ja koostumukseen. Nivelrikon kudosmuutosten kuvantamisen kehittäminen ja määrällinen tutkiminen taudin alkuvaiheissa tukisivat nykyisten nivelrikon hoitomenetelmien kehittämistä. Kliinisessä käytössä ja perustutkimuksessa, tietokonetomografia (TT) mahdollistaa luukuvantamisen ja varjoaineita käytettäessä myös rustokuvantamisen. Tämän väitöskirjan tavoitteena on esitellä ja validoida uusia mikrotietokonetomografia-menetelmiä (&#956;TT) nivelrikon rusto- ja luumuutosten määrälliseen tutkimukseen. Varjoaineavusteisia &#956;TT in vitro menetelmiä ruston kollageenin (fosfovolframihappoa (PTA) ja fosfomolybdeenihappoa (PMA)) ja GAG (CA4+) jakauman määrälliseen tutkimukseen validoitiin useilla eri ruston biokemiallista koostumusta mittaavilla vertailumenetelmillä. Rustonalaisen luun kuvantamista kehitettiin soveltamalla harmaasävyjen tekstuurianalyysiä, jolla pyrittiin tunnistamaan kuva-alkiota pienempiä luurakenteita. Rustonalaisen luun &#956;TT-kuvien analyysien tulokset validoitiin synkrotronisäteilyyn perustuvan &#956;TT:n avulla. Lisäksi tekstuurianalyysin soveltuvuutta testattiin kliinisen resoluution kartiokeilan TT-kuville. Kuvista analysoituja tekstuuriparametrejä verrattiin &#956;TT:lla mitattuun todelliseen rustonalaisen luun rakenteeseen. Väitöskirjan tulokset osoittavat, että PTA on spesifimpi kollageenille testatuista varjoaineista ja sen jakauma on verrannollinen kollageenijakaumaan jopa rappeutuneessa nivelrustossa. GAG-spesifisen varjoaineen CA4+:n todettiin kerääntyvän myös kondroneihin, mikä viittaa siihen, että kyseinen varjoaine soveltuisi potentiaalisesti rustosolujen korkean resoluution &#956;TT-tutkimuksiin. Rustonalaisen luun &#956;TT-kuvista analysoitujen tekstuuriparametrien havaittiin olevan verrannollisia osteosyyttien tilavuusfraktion kanssa. Väitöskirjassa esitettyjen tulosten perusteella &#956;TT-kuvantaminen tarjoaa kvantitatiivisen menetelmän nivelruston kollageenijakauman ja rustosolujen sekä rustonalaisen luun osteosyyttien tutkimuksiin. Väitöskirjassa esitetyt menetelmät laajentavat jo olemassa olevaa tutkimusmenetelmien kirjoa nivelrikon aiheuttamien nivelrusto- ja luumuutosten tutkimuksessa. Lisäksi kehitetyt kuva-analyysimenetelmät voivat tarjota tarkempaa tietoa kliinisestä TT:sta

Cellulose nanofiber aerogels impregnated with bio-based epoxy using vacuum infusion:structure, orientation and mechanical properties

Abstract Cellulose nanofiber aerogels were used as preforms that were impregnated with a bio-epoxy resin via a widely used vacuum infusion process. The simple and straightforward nanocomposite processing approach resulted in an almost 70% improvement in the storage modulus of the polymer with only an 11.7 wt% cellulose nanofiber content. The nanofibers were well dispersed in the polymer matrix and the fiber structures were anisotropically aligned. The impregnation time of the aerogels was also significantly lower than that of the more commonly used nanopapers. It was thus shown that environmentally friendly and mechanically robust nanocomposites could be produced by impregnating cellulose nanofiber aerogels with a thermosetting resin using a processing approach that has potential to be scaled up for commercial use

Cerebral haemodynamic effects in the human brain during radiation therapy for brain cancer

Abstract Radiotherapy is already well-established and an effective form of treatment for many cancers, especially for brain tumors. Currently, the clinical efficacy of a treatment, however, can only be established based on clinical or radiological responses observed after a significant period of time following the single irradiations during radiotherapy course. On the other hand, the radiotherapy dose is limited by its toxicity to surrounding healthy tissues. Particularly, radiation to brain tumors may sub-acutely or chronically affect cognition and cause fatigue even with conventional doses. However, there is currently no on-line and safe method to monitor the effects of radiation to the brain during the irradiation. In our project, we aim to develop an on-line method to monitor effects in brain tissue that correlate with the radiation dose in radiotherapy. In this case study, we use functional near-infrared spectroscopy (fNIRS) and study possible temporal effects in cerebral haemodynamics during irradiations of whole-brain radiotherapy (WBRT). fNIRS is safe for the patient, it can be used noninvasively and also in demanding environments, such as in radiotherapy treatment rooms during irradiation, and thus could be in future potential technique to be utilized for monitoring tailored radiotherapy

Load-dependent NMR low-field profiling and relaxation dispersion study of osteoarthritic articular cartilage

Abstract At low magnetic fields, T₁ variation within cartilage represents a robust parameter that is employed to quantify the layered structure in the tissue and is sensitive to factors such as enzymatic degradation, external load, and degeneration such as osteoarthritis. Variable-field relaxometry, on the other hand, provides access to the quadrupolar dips, i.e. enhanced relaxation rates of ¹H particularly at field strengths between 50 and 70 mT, that probe proton-nitrogen interaction and thus the content and local order of macromolecular constituents, namely glycosaminoglycans and collagen. At the same time, an strong overall dispersion of T₁ is observed over the whole accessible range of magnetic fields upward from 0.25 mT. In this study on 20 human cartilage samples, low-field and variable-field techniques were combined for the first time to correlate corresponding NMR parameters and the response to load with the severity of osteoarthritis. The magnitude of the quadrupolar dips, as well as cartilage thickness obtained from profile measurements, is found to correlate with the severity of osteoarthritis. At the same time, a significant correlation was identified for relaxation time variation before and after uniaxial compression at 0.6 MPa, a typical value for forces appearing in the human knee and hip joint. This finding is of importance since the spatial resolution of 50 μm obtained with the single-sided scanner is about one order of magnitude better than the one in clinical high-field or low-field scanners, thus allowing a much more detailed investigation and yet providing constraints for the interpretation of averaged values obtained with whole-body scanners

Effect of centrifugal force on the development of articular neocartilage with bovine primary chondrocytes

A lot has been invested into understanding how to assemble cartilage tissue in vitro and various designs have been developed to manufacture cartilage tissue with native-like biological properties. So far, no satisfactory design has been presented. Bovine primary chondrocytes are used to self-assemble scaffold-free constructs to investigate whether mechanical loading by centrifugal force would be useful in manufacturing cartilage tissue in vitro. Six million chondrocytes were laid on top of defatted bone disks placed inside an agarose well in 50-ml culture tubes. The constructs were centrifuged once or three times per day for 15 min at a centrifugal force of 771×g for up to 4 weeks. Control samples were cultured under the same conditions without exposure to centrifugation. The samples were analysed by (immuno)histochemistry, Fourier transform infrared imaging, micro-computed tomography, biochemical and gene expression analyses. Biomechanical testing was also performed. The centrifuged tissues had a more even surface covering a larger area of the bone disk. Fourier transform infrared imaging analysis indicated a higher concentration of collagen in the top and bottom edges in some of the centrifuged samples. Glycosaminoglycan contents increased along the culture, while collagen content remained at a rather constant level. Aggrecan and procollagen α1(II) gene expression levels had no significant differences, while procollagen α2(I) levels were increased significantly. Biomechanical analyses did not reveal remarkable changes. The centrifugation regimes lead to more uniform tissue constructs, whereas improved biological properties of the native tissue could not be obtained by centrifugation

Quantifying Complex Micro-Topography of Degenerated Articular Cartilage Surface by Contrast-Enhanced Micro-Computed Tomography and Parametric Analyses

One of the earliest changes in osteoarthritis (OA) is a surface discontinuity of the articular cartilage (AC), and these surface changes become gradually more complex with OA progression. We recently developed a contrast enhanced micro-computed tomography (mu CT) method for visualizing AC surface in detail. The present study aims to introduce a mu CT analysis technique to parameterize these complex AC surface features and to demonstrate the feasibility of using these parameters to quantify degenerated AC surface. Osteochondral plugs (n = 35) extracted from 19 patients undergoing joint surgery were stained with phosphotungstic acid and imaged using mu CT. The surface micro-topography of AC was analyzed with developed method. Standard root mean square roughness (R-q) was calculated as a reference, and the Area Under Curve (AUC) for receiver operating characteristic analysis was used to compare the acquired quantitative parameters with semi-quantitative visual grading of mu CT image stacks. The parameters quantifying the complex micro-topography of AC surface exhibited good sensitivity and specificity in identifying surface continuity (AUC: 0.93, [0.80 0.99]), fissures (AUC: 0.94, [0.83 0.99]) and fibrillation (AUC: 0.98, [0.88 1.0]). Standard R-q was significantly smaller compared with the complex roughness (CRq) already with mild surface changes with all surface reference parameters - continuity, fibrillation, and fissure sum. Furthermore, only CRq showed a significant difference when comparing the intact surface with lowest fissure sum score. These results indicate that the presented method for evaluating complex AC surfaces exhibit potential to identify early OA changes in superficial AC and is dynamic throughout OA progression. (c) 2019 The Authors. Journal of Orthopaedic Research (R) Published by Wiley Periodicals, Inc. on behalf of the Orthopaedic Research Society. Society. 9999:1-12, 2019.Peer reviewe