Biomedical subjects

Oleh Antonyshyn

Publications and source records attributed to Oleh Antonyshyn.

3 recordsLinked to original sources

PubMed2005

What is the microscopic tumor extent beyond clinically delineated gross tumor boundary in nonmelanoma skin cancers?

PURPOSE: To quantify the microscopic tumor extension beyond clinically delineated gross tumor boundary in nonmelanoma skin cancers. METHODS AND MATERIALS: A prospective, single arm, study. Preoperatively, a radiation oncologist outlined the boundary of a gross lesion, and drew 5-mm incremental marks in four directions from the delineated border. Under local anesthesia, the lesion was excised, and resection margins were assessed microscopically by frozen section. Once resection margins were clear, the microscopic tumor extent was calculated using the presurgical incremental markings as references. A potential relationship between the distance of microscopic tumor extension and other variables was analyzed. RESULTS: A total of 71 lesions in 64 consecutive patients, selected for surgical excision with frozen-section-assisted assessment of resection margins, were accrued. The distance of microscopic tumor extension beyond a gross lesion varied from 1 mm to 15 mm, with a mean of 5.2 mm. A margin of 10 mm was required to provide a 95% chance of obtaining clear resection margins. The microscopic tumor extent was positively correlated with the size of gross lesion, but not with other variables. CONCLUSIONS: The distance of microscopic tumor extension beyond a gross nonmelanoma skin cancer was variable, with a mean of 5.2 mm. Such information is critical for the proper radiation planning of skin cancer therapy.

Adult↗

PubMed2005

Measuring pulsatile forces on the human cranium.

The cyclic stresses in the cranium caused by pulsation of the brain play an important role in the design of materials for cranioplasty, as well as craniofacial development. However, these stresses have never been quantified. In this study, the force in the epidural space against the cranium was measured intraoperatively in 10 patients using a miniature force probe. Heart and ventilatory rates computed from the force tracing correlated closely with the corresponding measured values in the patients, confirming that the forces measured were indeed a result of brain pulsation. The mean outward systolic normal and tangential stresses were 54.2 kilo-Pascals (kPa) and 345.4 kPa, respectively. The systolic shear stress was 199.8 kPa. Through mechanotransduction, these stresses play a role in cranial development. The calculated yield stress of a cranioplasty repair was 0.4 MPa, which is within one order of magnitude of the known strength of common calcium-phosphate cements. This indicates a possible relation of these pulsatile forces and occult failure of calcium-phosphate cement cranioplasties through material fatigue.

Adult↗

PubMed2003

Multimodality imaging for precise localization of craniofacial osteomyelitis.

Functional imaging identifies areas of abnormal bone turnover, providing a useful adjunct in the treatment of osteomyelitis and bone tumors. The low resolution and lack of anatomical detail limit the application of bone scans in craniofacial surgery, however. Multimodality image registration addresses this problem by fusing functional images (single photon emission computed tomography [SPECT]) to high-resolution structural images (computed tomography [CT]) for precise anatomical delineation of bone activity. This article describes a technique for spatial registration of CT and SPECT images to provide precise anatomical delineation of abnormal bone turnover, thereby guiding the extent of resection in the management of craniofacial osteomyelitis. Standard CT and SPECT imaging protocols were used in imaging the skull from the vertex to the mentum. Image data were imported into Analyze (Biomedical Imaging Resource; Mayo Foundation, Rochester, MN) on a dedicated Windows NT (Microsoft Corporation, Redmond, WA) workstation. Using the CT data, the craniofacial skeleton, osteotomy segments, and bone grafts were interactively mapped out. Consecutive axial slices were then reconstructed to form a three-dimensional volume of interest. The CT-derived volume of interest was registered to the technetium Tc 99m-methylene diphosphonate SPECT scan using the Analyze program to provide a fused multimodality image. The imaging technique was used to localize osteomyelitis in a complex craniofacial reconstruction. The fused images guided the extent of resection during surgery, and postoperative microbiological and histological testing confirmed the diagnosis. Multimodality image registration provides a readily available method to relate facial skeletal anatomy and physiology. This technique is valuable in planning and monitoring therapeutic interventions in clinical conditions in which bone turnover is abnormal.

Adult↗