Matthew A Lewis | PubMed Health

PubMed2006

Iterative reconstruction method for light emitting sources based on the diffusion equation.

Bioluminescent imaging (BLI) of luciferase-expressing cells in live small animals is a powerful technique for investigating tumor growth, metastasis, and specific biological molecular events. Three-dimensional imaging would greatly enhance applications in biomedicine since light emitting cell populations could be unambiguously associated with specific organs or tissues. Any imaging approach must account for the main optical properties of biological tissue because light emission from a distribution of sources at depth is strongly attenuated due to optical absorption and scattering in tissue. Our image reconstruction method for interior sources is based on the deblurring expectation maximization method and takes into account both of these effects. To determine the boundary of the object we use the standard iterative algorithm-maximum likelihood reconstruction method with an external source of diffuse light. Depth-dependent corrections were included in the reconstruction procedure to obtain a quantitative measure of light intensity by using the diffusion equation for light transport in semi-infinite turbid media with extrapolated boundary conditions.

Algorithms↗

PubMed2005

Reduction in normalized bone elasticity following long-term bisphosphonate treatment as measured by ultrasound critical angle reflectometry.

Using an improved version of ultrasound critical angle reflectometry, the bone quality of cortical and trabecular bone was assessed in vivo by measuring elastic moduli (normalized for bone density) at both principal axes, referred to as the minimum and maximum normalized elasticities. The measurements were made in 30 normal premenopausal women, 30 normal postmenopausal women, 22 untreated postmenopausal women with osteoporosis, 74 postmenopausal women with osteoporosis or osteopenia on bisphosphonate treatment, and 32 patients with renal transplantation (16 women and 16 men) taking steroids. Cortical elasticity was higher than trabecular elasticity; both declined slightly and non-significantly with age in normal women. Among untreated postmenopausal women with osteoporosis, cortical maximum normalized elasticity (E(cmax)) remained within 95% prediction intervals of normal women. Among patients on bisphosphonate, E(cmax) was low in the majority of patients. E(cmax) was significantly more depressed among those taking the drug > or =3 years than <3 years (22.1% below normal premenopausal women versus 17.2%, P =0.001), and among those with incident non-spinal fractures than without (75.9 vs. 81.5%, P =0.008). E(cmax) was independent of bone mineral density at the calcaneus. Most patients with renal transplantation had low E(cmax), with a mean 20.8% below the normal premenopausal mean. Qualitatively similar findings were found with cortical minimum elasticity and with trabecular minimum and maximum elasticities. Thus, the material bone quality of cortical and trabecular bone may be impaired following bisphosphonate treatment, as in renal transplantation on steroids.

Adult↗