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R Nord

Publications and source records attributed to R Nord.

5 recordsLinked to original sources
PubMed2000

Axial and total-body bone densitometry using a narrow-angle fan-beam.

We assessed a new dual-energy bone densitometer, the PRODIGY, that uses a narrow-angle fan-beam (4.5 degrees) oriented parallel to the longitudinal axis of the body (i.e., perpendicular to the usual orientation). High-resolution scans across the body can be stepped at 17 mm intervals. The energy-sensitive array detector uses cadmium zinc telluride, which allowed rapid photon counting. Spine and femur scans required 30 s, and total-body scans required 4-5 min; the dose was only 3.7 mrem and 0.04 mrem respectively, or about 5 to 10 times lower than conventional fan-beam densitometry. We found only a small influence of soft-tissue thickness on bone mineral density (BMD) results. There was also a small (+/- 1%) influence of height above the tabletop on BMD results. A software correction for object height allowed a first-order correction for the large magnification effects of position on bone mineral content (BMC) and area. Consequently, the results for BMC and area, as well as BMD, with PRODIGY corresponded closely to those obtained using the predecessor DPX densitometer, both in vitro and in vivo; there was a generally high correlation (r = 0.98-0.99) for BMD values. Spine and femur values for BMC, area and BMD averaged within 0.5% in vivo (n = 122), as did total-body BMC and BMD (n = 46). PRODIGY values for total-body lean tissue and fat also corresponded within 1% to DPX values. Regional and total-body BMD were measured with 0.5% precision in vitro and 1% precision in vivo. The new PRODIGY densitometer appears to combine the low dose and high accuracy of pencil-beam densitometry with the speed of fan-beam densitometers.

Absorptiometry, Photon↗
PubMed2000

Bilateral measurement of femoral bone mineral density.

Both femora were measured on 61 normal adults using dual X-ray absorptiometry (DXA). In a subset of 31 subjects, each femur was scanned once using the conventional leg-positioning device supplied with the densitometer, and once using a new positioning device and software that allowed both legs to be measured simultaneously. In another subgroup (n = 30), subjects were measured three times using the new dual-femur approach to better assess precision error. The data were analyzed for differences owing to the different positioning devices and for differences between right and left sides. The correlation between results with the old and new positioners was high (r > 0.99, standard error of the estimate [SEE] = 0.01-0.02 g/cm(2)). There was no significant difference in the average bone mineral density (BMD) values between the old and new positioner. The precision errors for each femur alone with the dual-femur approach were similar to those reported for the single-femur scans (1 to 2%), but the precision errors for the combined femora were reduced by 30% as expected. The correlation between right and left sides was high (r = 0.94-0.96), and the SEE in predicting one side from the other was moderate for total, trochanteric, and femoral neck BMD (0.05, 0. 05, and 0.06 g/cm(2), respectively). These SEE equate to about 0.5 standard deviation in terms of T-score. Differences in many individual cases between the right and left sides were significantly greater than the precision error. The new dual-femur software and leg positioner allows rapid measurement and analysis of both femora, thereby eliminating the uncertainty between sides.

Absorptiometry, Photon↗
PubMed1993

Prone split leg and flank roll positioning: simultaneous antegrade and retrograde access to the upper urinary tract.

The simultaneous endoscopic approach to upper urinary tract pathology in both an antegrade and retrograde fashion can be cumbersome. The prone split leg and flank roll positions allow such simultaneous access. Of 111 patients in whom the prone split leg position was employed, 41% were treated with simultaneous antegrade and retrograde endoscopy in a two-team approach. Treating large staghorn calculi in this manner, one team debulked the stone burden accessible through the flank nephroscopically, while another team approached the remainder of the stone burden using the pulsed-dye laser ureteroscopically in a retrograde manner. The flank roll position was employed in 15 patients who presented with percutaneous nephrostomies and were deemed treatable preoperatively in a retrograde manner. They were positioned in this manner to allow intraoperative access to the percutaneous nephrostomy tract. Nine of these patients required antegrade treatment. The application of these two positions and the concept of the two-team approach added to the efficiency of treating not only staghorn calculi, but other upper tract pathology. Simultaneous procedures require at least two skilled endoscopists as well as dual light sources, various lithotrites, and several rigid and flexible endoscopes.

Combined Modality Therapy↗