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Biomedical subjects

R Mazess

Publications and source records attributed to R Mazess.

7 recordsLinked to original sources
PubMed1992

Enhanced precision with dual-energy X-ray absorptiometry.

Repeat spine and femur measurements (5 per case) were done on 19 subjects with the DPX-L densitometer operating at 3 mA giving a radiation flux fourfold higher than the earlier DPX model. The precision for spine bone mineral density (BMD) was about 0.55% (L2-L4) and 0.48% (L1-L4) for 2-minute scans (2.4 mrem). The precision was only slightly lower (0.4-0.5%) for 4-minute scans (5 mrem) in a subset of 11 subjects. There was a slight precision advantage for the larger L1-L4 area compared with L2-L4 for 2-minute scans, but no advantage for 4-minute scans. The precision for femoral neck BMD was 1.00 and 0.85% for 2- and 4-minute scans, respectively, with proper positioning. The corresponding values for the Ward's triangle region of the femur were 2.6 and 1.5%. The precision of spine scans was influenced chiefly by variable region location. The precision of femur scans was affected by both patient positioning and location of the region. The 4-minute scans minimized the number of operator changes necessary for analysis. Precision errors can be reduced by up to 50% with utilization of the higher flux, but this does not obviate the need for care in patient positioning and scan analysis.

Absorptiometry, Photon↗
PubMed1989

Whole body and regional retention of Tc-99m-labeled diphosphonates with a whole-body counter: a study with normal males.

A collimated whole-body counter was used to measure the retention and distribution of radioactivity along the longitudinal axis of the body at several times during the 24 hours after the intravenous injection of 50 microCi of Tc-99m-diphosphonates. Whole-body retention (WBR) was measured together with regional uptakes in the following four areas: head, chest, bladder, and legs using two structurally related Tc-99m-diphosphonate skeletal imaging agents: 1-hydroxyethylidene diphosphonate (HEDP) and methylene diphosphonate (MDP). The average 24 hour WBR values in young males, reflecting skeletal uptake of these tracers, were 17.7 +/- 2.2% (n = 20) and 31.0 +/- 2.4% (n = 3), respectively. A model of skeletal clearance was developed using the sum of two exponentials. In normal volunteers the initial rapid clearance phase of both tracers had a half-time of about 1 hour, whereas the slower second phase clearance had a half-time of 22 hours with HEDP and 44 hours with MDP. The WBR is usually calculated for the entire body only at 24 hours, but with the improved spatial resolution of a collimated whole-body counter, regional measurements could potentially be done over shorter periods (6-8 hours) in order to simplify the procedure.

Bone Diseases↗
PubMed1989

Performance evaluation of a dual-energy x-ray bone densitometer.

We tested a dual-energy bone densitometer (LUNAR DPX) that uses a stable x-ray generator and a K-edge filter to achieve the two energy levels. A conventional scintillation detector in pulse-counting mode was used together with a gain stabilizer. The densitometer normally performs spine and femur scans in about 6 minutes and 3 minutes, respectively, with adequate spatial resolution (1.2 x 1.2 mm). Total body scans take either 10 minutes or 20 minutes. The long-term (6 months, n = 195) precision of repeat measurement on an 18-cm thick spine phantom was 0.6% at the medium speed. Precision error in vivo was about 0.6, 0.9 and 1.5% for spine scans (L2-L4) at slow, medium and fast speeds, while the error was 1.2 and 1.5 to 2.0%, respectively, for femur scans at slow and medium speed. The precision of total body bone density was 0.5% in vitro and in vivo. The response to increasing amounts of calcium hydroxyapatite was linear (r = 0.99). The densitometer accurately indicated (within 1%) the actual amount of hydroxyapatite after correction for physiological amounts of marrow fat. The measured area corresponded exactly (within 0.5%) to that of known annuli and to the radiographic area of spine phantoms. There was no significant effect of tissue thickness on mass, area, or areal density (BMD) between 10 and 24 cm of water. The BMD values for both spine and femur in vivo correlated highly (r = 0.98, SEE = .03 g/cm2) with those obtained using conventional 153Gd DPA. Similarly, total body BMD correlated highly (r = 0.96, SEE = .02 g/cm2) with DPA results.

Absorptiometry, Photon↗
PubMed1989

Comparison of speed of sound and ultrasound attenuation in the os calcis to bone density of the radius, femur and lumbar spine.

Broadband ultrasonic attenuation (BUA) between 0.1 and 0.6 MHz and speed of sound (SOS) were measured on the os calcis in normal women (n = 40), and women who had mild osteoporosis (n = 36). Comparisons were made between the ultrasonic properties and bone mineral densities (BMD) obtained using photon absorptiometry on the lumbar spine, proximal femur and radius shaft. In the osteoporotic women, whose spine BMD was significantly reduced, BUA and SOS were lower, to about the same degree of significance as radius BMD; ROC analysis demonstrated that for discrimination of spinal osteopenia, the area under the ROC curve was similar for radius BMD, SOS, and BUA. There was a modest correlation (r about 0.65) between either SOS or BUA on the os calcis and BMDs of the spine and radius. Correlations of the SOS and BUA with femoral neck BMD were lower (r about 0.4 to 0.5). The standard error of estimate for both spine and femoral neck BMD was too high (about 0.14 g cm-2) for os calcis measurements to be substituted clinically for densitometry at these fracture sites.

Absorptiometry, Photon↗
PubMed1986

Bone densitometry.

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Bone and Bones↗
PubMed1986

Absorption of oral diphosphonate in normal subjects.

Absorption of the diphosphonate etidronate (HEDP) was measured in 20 volunteer subjects at two centres (Glasgow and Madison) using a new method based on simultaneous administration of HEDP and intravenous 99mTc-HEDP (Osteoscan). The mean absorption of HEDP in fasting subjects in Glasgow was 3.5% (range 1-8.9%) and in Madison 1.5% (0.7-2.8%) (P less than 0.035). In four subjects studies were repeated with good agreement between results (mean 3.9 cf. 3.5%). Six subjects had studies repeated when drug was ingested with food and in all cases absorption was effectively reduced to zero. We conclude that absorption of HEDP is significantly higher in normal subjects in Glasgow than in Madison. This may be of importance with regard to the finding of histological osteomalacia and fracture associated with HEDP use in Glasgow.

Administration, Oral↗