Biomedical subjects

Peter P Antich

Publications and source records attributed to Peter P Antich.

5 recordsLinked to original sources

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↗

PubMed2004

Validating bioluminescence imaging as a high-throughput, quantitative modality for assessing tumor burden.

Bioluminescence imaging (BLI) is a highly sensitive tool for visualizing tumors, neoplastic development, metastatic spread, and response to therapy. Although BLI has engendered much excitement due to its apparent simplicity and ease of implementation, few rigorous studies have been presented to validate the measurements. Here, we characterize the nature of bioluminescence output from mice bearing subcutaneous luciferase-expressing tumors over a 4-week period. Following intraperitoneal or direct intratumoral administration of luciferin substrate, there was a highly dynamic kinetic profile of light emission. Although bioluminescence was subject to variability, strong correlations (r >.8, p <.001) between caliper measured tumor volumes and peak light signal, area under light signal curve and light emission at specific time points were determined. Moreover, the profile of tumor growth, as monitored with bioluminescence, closely resembled that for caliper measurements. The study shows that despite the dynamic and variable nature of bioluminescence, where appropriate experimental precautions are taken, single time point BLI may be useful for noninvasive, high-throughput, quantitative assessment of tumor burden.

Animals↗

PubMed2003

Molecular imaging in prostate cancer.

Prostate cancer (PCa) is the most common non-cutaneous malignancy in men. New ways to diagnose this cancer in its early stages are needed. Unique genetic and biochemical changes in the cell pave the way for tumors to grow and metastasize. Novel imaging approaches attempt to detect pathological processes in cancer cells at the molecular level. This has led to the establishment and development of the field of molecular imaging. Positron emission tomography (PET), magnetic resonance spectroscopic imaging (MRSI), magnetic resonance imaging (MRI), and radiolabeled antibodies are a few of the modalities that can detect abnormal tumor metabolic processes in the clinical setting. Other imaging techniques are still in their early phase of development but hold promise for the future, including bioluminescence imaging (BLI), measurement of tumor oxygenation, and measurement of uptake of iodine by tumors. These techniques are non-invasive and can spare the patient undue morbidity, while potentially providing early diagnosis, accurate follow-up and, finally, valuable prognostic information.

Animals↗

PubMed2003

Tumor oximetry: comparison of 19F MR EPI and electrodes.

We recently described a novel approach to measuring regional tumor oxygen tension. This approach is based on 19F pulse burst saturation recovery NMR echo planar imaging relaxometry of hexafluorobenzene or "FREDOM" (Fluorocarbon Relaxometry using Echo planar imaging for Dynamic Oxygen Mapping). We have now compared oxygen tension measurements using FREDOM with a traditional polarographic method (the Eppendorf Histograph) in a group of size matched Dunning prostate rat tumors R3327-AT1. We also compare MR and electrode approaches to monitoring dynamic changes with respect to interventions and demonstrate extension of the MR technique to rat breast tumors.

Adenocarcinoma↗