Biomedical subjects

T M Boyce

Publications and source records attributed to T M Boyce.

21 records · Page 2Linked to original sources

PubMed1988

First-pass radionuclide angiography using a multiwire gamma camera and tantalum-178.

A portable multiwire gamma camera (MWGC) with enhanced imaging characteristics relative to conventional sodium iodide camera has been evaluated with 178Ta, a short-lived, generator-produced radioisotope (half-life 9.3 min). First-pass radionuclide angiography (FPRA) was performed and results were compared to those obtained with FPRA using a multicrystal camera (MCC) and 99mTc in 38 patients. The overall left ventricular count sensitivity (counts/mCi/sec/millisteradians [msr]) was significantly higher with MWGC/178Ta (176 +/- 132 versus 108 +/- 49, p less than 0.001) yielding images of higher statistics with higher resolution collimation (31 versus 63 msr). Left ventricular ejection fraction was 0.54 +/- 0.18 by MWGC and 0.54 +/- 0.18 by MCC with an excellent correlation between the two techniques (r = 0.94, s.e.e. = 0.06). The detection of wall motion abnormality was virtually identical with the two techniques. Intra- and interobserver reproducibility by MWGC was excellent (r = 0.99 and 0.99, respectively). Thus, this new technology provides first-pass studies of higher statistical quality and improved resolution, affording more precise assessment of left ventricular performance and likelihood of further substantial improvement by use of even higher doses of 178Ta.

Adult↗

PubMedDate not supplied

Cortical aging differences and fracture implications for the human femoral neck.

Clinical imaging techniques cannot consistently identify individuals at risk for hip fracture. Individual differences in falling likelihood partly account for these inconsistencies, but it is also thought that microscopic bone changes may play a role. In this study, subcapital, mid-neck, and trochanteric sites from eight young adult (26 +/- 7 years) and nine older (63 +/- 3 years) males were studied using backscattered electron imaging to identify age-related microscopic structural and mineral changes around the cortex. Cortical bone volume (BV(Ct)/TV), cortical void volume (Vd.V(Ct)/TV), hypermineralized bone volume (BV(H-min)/TV), the number of osteons/mm2 (N.On/B.Ar), lacunae/mm2 (N.Lc/B.Ar(Ct)) in the cortex, lacunae/mm2 (N.Lc/B.Ar(H-min)) in the hypermineralized phase, and cortical thickness (Ct.Th) were measured at subcapital, mid-neck, and trochanteric levels. Cortical void volume showed no differences (P = 0.26) between levels in the younger group, but differences (P < 0.05) were observed in the older group, indicating locational osteopenic differences. Cortical thickness differences were greater at the subcapital (27.7%) and mid-neck (25.2%) levels than at the trochanteric level (10.5%). Both age (P = 0.0022) and level-location interaction (P < 0.0001) influenced the hypermineralized bone volume present, with larger hypermineralized regions generally occurring at the thinner superior locations. Significant (P < 0.05) lacunar differences with aging in the hypermineralized phase suggest a necrotic origin. Artifactual cracks occurred preferentially within the hypermineralized phase, indicating localized reductions in fracture toughness, which may provide a site for crack initiation following an impact.

Adult↗

PubMedDate not supplied

Aging changes in osteon mineralization in the human femoral neck.

Age-related mineral changes are associated with material property changes in cortical bone, which may affect its ability to transmit loads and resist fracture from falling. Aging changes in the mineral content of the femoral neck cortical bone are partly determined by osteonal remodeling events. The objective of this study was to measure mineral differences within the osteonal unit in the human femoral neck. In this study, cadaveric femora from male caucasians of two age groups (25 +/- 7, n = 6; 64 +/- 4, n = 6) were sectioned at the midfemoral neck. Using backscattered electron imaging, osteons from each of eight circumferential cortical regions were analyzed to determine osteonal mineral differences between regions, between the two age groups, and due to radial location within the osteons. Graylevel values from the backscattered electron imaging method were calibrated in equivalent ash content (wt%) units to provide a better understanding of the magnitude of differences observed. A pattern (p < 0.05) of decreasing osteonal mineralization was observed with distance from the central Haversian canal. Additionally, osteonal mineralization was highest in the superior (most lateral) regions of the femoral neck from both age groups, indicating that circumferential location is an influencing factor. The average overall equivalent ash content of osteons from the 17-35-yr group was 59.4 +/- 0.4% (mean +/- SE) by weight, while osteons of the group aged 60-71 measured 52.0 +/- 0.4% equivalent ash content, a decrease of 12.4%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗