J Karsh

Bio: J Karsh is an academic researcher from University of Ottawa. The author has contributed to research in topics: Osteoporosis & Bone density. The author has an hindex of 1, co-authored 1 publications receiving 6 citations.

Diagnostic challenges in osteoporosis. Indications for bone densitometry and establishing secondary causes.

Abstract: OBJECTIVE: To review indications for assessing bone mineral density (BMD) and to review patient characteristics and diseases associated with osteoporosis. QUALITY OF EVIDENCE: This paper is based on data from longitudinal observational studies of how BMD and other risk factors affect development of fragility fractures and on several peer-reviewed publications describing pathophysiology of bone turnover and pathogenesis of osteoporosis. Indications for obtaining BMD and monitoring treatment are based on the recommendations of the Osteoporosis Society of Canada derived from the consensus opinion of a panel of experts in osteoporosis and based on their review of the primary literature. MAIN MESSAGE: Measurement of BMD provides the best single objective predictor of the relative risk of fracture at sites such as the vertebrae, hip, and wrist, predicting the likelihood of fracture with as much accuracy as measurement of elevated blood pressure predicts stroke. In addition to making the diagnosis of osteoporosis, BMD measurements are used to monitor progression of osteoporosis and effects of therapy. At this date, dual energy x-ray absorptiometry is preferred for measuring BMD. The most likely causes of osteoporosis in any patient are age, hormone withdrawal (in both men and women), and drugs (particularly corticosteroids). Secondary causes, particularly hyperparathyroidism and multiple myeloma, should be excluded by performing appropriate laboratory tests. CONCLUSION: A BMD measurement should be obtained for patients at high risk of osteoporosis and fragility fractures to guide initiation and monitor success of therapy.

Breast imaging flow models.

Abstract: Economically efficient and clinically effective breast imaging can be achieved through combinations and permutations of four fundamental breast imaging flow models: (1) the traditional flow model, (2) the online flow model, (3) the women’s imaging flow model, and (4) the combination-care flow model. The structure, strengths, and weaknesses of these four individual breast imaging flow models are described and compared.

Establishing a method to measure bone structure using spectral CT

Abstract: Combining bone structure and density measurement in 3D is required to assess site-specific fracture risk. Spectral molecular imaging can measure bone structure in relation to bone density by measuring macro and microstructure of bone in 3D. This study aimed to optimize spectral CT methodology to measure bone structure in excised bone samples. MARS CT with CdTe Medipix3RX detector was used in multiple energy bins to calibrate bone structure measurements. To calibrate thickness measurement, eight different thicknesses of Aluminium (Al) sheets were scanned one in air and the other around a falcon tube and then analysed. To test if trabecular thickness measurements differed depending on scan plane, a bone sample from sheep proximal tibia was scanned in two orthogonal directions. To assess the effect of air on thickness measurement, two parts of the same human femoral head were scanned in two conditions (in the air and in PBS). The results showed that the MARS scanner (with 90μm voxel size) is able to accurately measure the Al (in air) thicknesses over 200μm but it underestimates the thicknesses below 200μm because of partial volume effect in Al-air interface. The Al thickness measured in the highest energy bin is overestimated at Al-falcon tube interface. Bone scanning in two orthogonal directions gives the same trabecular thickness and air in the bone structure reduced measurement accuracy. We have established a bone structure assessment protocol on MARS scanner. The next step is to combine this with bone densitometry to assess bone strength.

Lectin receptor sites during postnatal osteogenesis in guinea pigs.

Abstract: BACKGROUND Osteoporosis and its complications have become widespread, affecting large portions of the world's population. More advanced information is needed on these pathologies to expand the possibilities for pathogenetic therapy. OBJECTIVES Lectin histochemistry methods offer new insights into the structure of tissue carbohydrates and their rearrangement under physiological and pathological conditions. The aim of the present investigation was to use a set of lectins with different carbohydrate affinities to study postnatal remodelling of cartilage and bone in relation to the age and sex of experimental animals. MATERIAL AND METHODS A panel of five conventional lectins--Con A, PNA, RCA, WGA, SNA, supplemented with an original fucose-specific lectin from Laburnum anagyroides bark (LABA)--was used to investigate the femoral bones of female and male guinea pigs aged 3 months, 1 year and 3 years. Tissue samples were fixed in 4% formaline, decalcified in 7% HNO3 and embedded in paraplast. The sections were subjected to a routine lectin-peroxidase-diaminobenzidine visualization technique. RESULTS A pronounced labeling of growth plate chondromucoid was found with Con A, PNA and SNA. Articular cartilage showed much fainter labeling with these same lectins. Capsules of isogenic groups of chondrocytes expressed a strong affinity for SNA and WGA, encompassing a predominance of Neu5Ac/2-6Gal, DGlcNAc and NeuNAc determinants. Osseomucoid showed faint reactivity with all the lectins used, while SNA distinctly marked the line of ossification. Glycoconjugates within lacunas and osseous canaliculi, as well as cytoplasmic glycoconjugates of bone and cartilage cellular elements, expressed strong labeling with RCA and SNA. Osteoclasts reacted selectively with PNA. A comparison of lectin labeling between the experimental groups indicated that the tissue reactivity of males exceeded that of females, and that aging caused a decrease in the lectin reactivity of both genders. CONCLUSIONS The data extend current knowledge regarding the selective lectin labeling of osseous tissue constituents, and demonstrate the applicability of lectin histochemistry methods in osteoporosis studies.