计算机X线摄影图像的静止滤线栅伪影分析

目的通过分析计算机X线摄影（CR）系统的采样频率和栅密度频率，提出尽可能有效避免滤线栅伪影出现的抑制方法。方法实际测试不同栅密度的滤线栅与不同规格的成像板（IP）匹配使用，得到不同效果的图像；模拟2种信号频率（即2种栅密度的滤线栅），采用3种采样频率[6、8、10图像空间分辨率（pixels／mm）]，得到不同的模拟图像效果。结果通过对比分析模拟图和实际图像，发现在采样频率正好等于信号频率的2倍时，可以得到正确的信号频率，图像清晰，无混淆现象。栅密度〈4LP／mm时，可较好地与14in×14in、10in×12in（1in=2．54cm）IP匹配使用。结论CR系统与普通IP匹配使用合适的采样频率和栅密度频率，可以有效避免滤线栅伪影出现。     

薄层扫描法测定血浆中盐酸氟桂利嗪浓度及药物动力学

血浆中盐酸氟桂利嗪经硼酸缓冲液酸化后，正戊烷－异丙醇（９８：２）提取其原型，加酸使成盐溶于无机相中，再加碱后用二氯甲烷提取，样品点于硅胶ＧＦ２５４薄层板上，以环己烷－丙酮－氯仿（９：３：５）为展开剂。氟桂利嗪在２５４ｎｍ紫外灯下呈紫色斑点，Ｒｆ＝０．５４，于ＣＳ－９３０薄层扫描仪上测定，λｓ＝２１５ｎｍ、λｇ＝３１０ｎｍ，线性范围０．３￣８μｇ，平均回收率９０．０２％。用此法测定了氟桂利嗪血药浓度     

Influence of Bone Quality on Precision of Calcaneal Ultrasonometry

This study was designed to determine the changes in precision of the ultrasound parameters speed of sound (SOS), broadband ultrasound attenuation (BUA), and stiffness index (SI) as a function of bone quality. The instrument used in this investigation was the LUNAR Achilles. Of the 608 female patients who had paired measurements with repositioning, 200 had t scores ≥−1 and 408 had t scores ≤−2.5, thus rendering a normal and a grossly abnormal group for comparison of precision results. It was found that the median precision error (CV%) for BUA was 1.99% for normal bone and 1.44% for abnormal bone (P= 0.02). No significant difference was obtained between median precision errors in normal and abnormal bone for the parameters SOS and SI, which were 0.23% and 0.19%, and 2.15% and 2.02%, respectively. In the interquartile range, the mean precision errors for SOS and BUA were significantly different in normal and abnormal bone: SOS was 0.25% and 0.21%, respectively, and BUA was 2.31% and 1.85%, respectively. No significant change was registered for SI. Precision error appears to decrease slightly at lower values for calcaneal variables. Received: 21 August 1996 / Accepted: 5 March 1997     

Ex vivo estimation of thoracolumbar vertebral body compressive strength: The relative contributions of bone densitometry and vertebral morphometry

The estimation of vertebral fracture risk in individuals with suspected osteopenia is commonly based on measurements of lumbar spine bone density. The efficacy of vertebral size and deformity, as assessed by vertebral morphometry, in the prediction of fractures has been less studied. In an ex vivo investigation the regional relationships between vertebral size, vertebral deformity, bone density and compressive strength throughout the thoracolumbar spine were examined. In 16 vertebral columns (T1–L5) the bone mineral content (BMC) and bone mineral density (BMD) of each segment were measured using lateral projection dual-energy X-ray absorptiometry, and the vertebral cancellous density (VCD) and mid-vertebral cross-sectional area (CSA) measured using quantitative computed tomography. Vertebral body heights were determined from mid-sagittal CT scans, and vertical height ratios calculated for each segment. The failure load and failure stress of the isolated vertebral bodies were determined using a material testing device. Separate analyses were performed for the upper (T1–4), middle (T5–8) and lower (T9–12) thoracic, and lumbar (L1–5) segments. In all regions, failure load was strongly correlated with BMD (r=0.82–0.86), moderately correlated with VCD (r=0.60–0.71) and vertebral height (r=0.22–0.49), and poorly correlated with the height ratios (r=0.04–0.33). Failure stress was best predicted by BMD (r=0.73–0.78) and VCD (r=0.70–0.78) but was poorly correlated with all morphometric variables (r=0.01–0.33). The segmental correlations between BMD and VCD ranged fromr=0.49 tor=0.79. For all regions, BMD and VCD were included in the stepwise regression models for predicting failure load and failure stress. Either the mid-vertebral height or CSA were included in all the failure load models, while mid-vertebral height was included in only one of the failure stress models. The results suggest that vertebral deformity and size (as assessed by vertebral morphometry) make only a minor contribution to the prediction of vertebral strength additional to that provided by bone densitometry alone. The consistent regional relationships between variables appear to support the practice of global fracture risk assessment based on lumbar spine densitometry.     

Reproducibility of lateral spine scans using dual energy X-ray absorptiometry

Summary Reproducibility of lateral spine dual energy X-ray absorptiometry (LAT DEXA) scans using a Lunar DPX-L scanner was assessed in a cadaveric phantom and in patients. One hundred phantom measurements over 7 months demonstrated a longitudinal stability of 1.7% (coefficient of variation, CV). Additional scans were performed with the phantom rotated by up to 20° in each of the three orthogonal planes to assess the effects of variable patient positioning. Horizontal and vertical rotation of the spine had little effect on the estimated bone mineral density (BMD), however, axial rotation of greater than 8° led to errors in the BMD measurement. One hundred consecutive patients had two lateral scans performed within 1 month. BMD (range 0.10–1.6 g/cm²) was determined for each scan by one operator. Significant overlap from ribs and pelvis was often seen with L2 and L4 vertebrae but one vertebra (L3) could be measured in every case. Intraoperator and interoperator variability was assessed by three experienced operators, each analyzing 10 patients' scans on five separate occasions, and was found to be less than 1.1% for a single vertebra. BMD estimation of vertebral bodies and midslices by lateral DEXA scans (CV% of 3.8% and 4.6%) have a 95% confidence interval of 0.074 g/cm² and 0.096 g/cm², respectively for two vertebrae. This variability is due mainly to axial rotation, with operator variability, horizontal rotation, and vertical rotation having little effect on BMD estimation.     

Relative body fat and anthropometric prediction of body density of female athletes

Summary Ninety-one percent (n=182) of the female members of South Australian representative squads in 14 sports volunteered to act as subjects. Twenty-seven percent of them had represented Australia. The underwater weighing method together with the measurement of residual volume (RV) by helium dilution were used to determine body density (BD); the percent body fat (% BF) was then computed according to Siri.A stepwise multiple regression analysis yielded a correlation coefficient (R) of 0.863 between the criterion (BD) and the best weighted sum of predictors (anthropometric variables): BD (g·cm^–3)=1.14075–0.04959 (log₁₀ triceps, subscapular, supraspinale and calf skinfolds in mm)+0.00044 (age in decimal years)–0.000612 (waist girth in cm)+0.000284 (height in cm)–0.000505 (gluteal girth in cm)+0.000331 (breast girth in cm).Only those predictors which resulted in a statistically significant increase inR (p0.05) were included. The standard error of estimate of 0.00597 g · cm^–3 was equivalent to 2.7% BF at the mean. This equation was shown to be largely population specific. There was a range of 7.6–35.8% of BF and the overall mean of 18.5% was significantly lower (p<0.001) than that of 23.4% obtained on a moderately active reference sample of similar age (n=135). If group sizes of only one or two are regarded as too small for meaningful comparison, then the lowest mean of 13.5% was achieved by the long-distance runners (n=14). The highest averages were registered by the heavyweight rowers (24.2%;n=7) and soccer players (22.0%;n=11). The overall average for games players (n=107) was 19.4%.This study was supported by a grant from the National Health and Medical Research Council of Australia     

An atlas of glycine- and GABA-like immunoreactivity and colocalization in the cochlear nuclear complex of the guinea pig

Summary The distribution and colocalization of -aminobutyric acid (GABA)- and glycine-like immunoreactivity in the cochlear nuclear complex of the guinea pig have been studied to produce a light microscopic atlas. The method used was based on post-embedding immunocytochemistry in pairs of 0.5-m-thick plastic sections treated with polyclonal antibodies against conjugated GABA and glycine respectively. Immunoreactive cells, presumably short axon neurones, predominated in the dorsal cochlear nucleus, with mostly single-GABA-labelled cells in the superficial layer, double-labelled in the middle, and single-glycine-labelled in the deep layers. A few large single-glycine-labelled cells, interpreted as commissural neurons, occurred in the ventral nucleus. Scattered double-labelled cells, probably Golgi cells, were seen in the granule cell domain. Immunolabelled puncta of all three staining categories occurred in large numbers throughout the complex, apposed to somata and in the neuropil, showing a differential distribution onto different types of neuron. Three immunolabelled tracts were noted: the tuberculoventral tract, the commissural acoustic stria, and the trapezoidal descending fibres. Most of the fibres in these tracts were single-labelled for glycine, although in the last mentioned tract single-GABA- and double-labelled fibres were also found. Some of the immunolabelled cell types described here are proposed as the origins of the similarly labelled puncta and fibres on the basis of known intrinsic connections.Abbreviations 1-4 DCN layers 1 to 4 - as acoustic stria - AVCN anteroventral cochlear nucleus - C caudal - cap cap area - cas commissural acoustic stria - cnr cochlear nerve root - co commissural cell - CRVCN central region of the VCN - cw cartwheel cell - CZ confluence zone - d dendrite - D dorsal - das dorsal acoustic stria - DCN dorsal cochlear nucleus - df descending fibres - ep ependyma - flocc flocculus - g glial cell - GABA -aminobutyric acid - GLY glycine - gi giant cell - gl/gla globular cell/area - Go Golgi cell - gr granule cell - ias intermediate acoustic stria - icp inferior cerebellar peduncle - lam granule cell lamina - mp/mpa multipolar cell/area - oc/oca octopus cell/area - PVCN posteroventral cochlear nucleus - py pyramidal cell - R rostral - sgl superficial granule cell layer - spcg subpeduncular corner of granule cells - sph/spha spherical cell/area - st stellate cell - tb trapezoid body - tv tuberculoventral cell - TVT tuberculoventral tract - V ventral - VCN ventral cochlear nucleus - vn vestibular nerve     

Image Resolution of the Lunar Expert-XL

The Lunar Expert-XL is an example of the latest generation of fan beam densitometers, with the X-ray source and detector array mounted on a C-arm to enable supine lateral imaging. Image resolution for anteroposterior (AP) spine, femur, hand, forearm and lateral morphometry on the Expert-XL were assessed in vitro with the 07-541 Nuclear Associates line pair test pattern. Each scan type was investigated at all available tube currents and scan speeds, and at the maximum, minimum and default bed heights. The effect of soft tissue thickness on resolution was investigated by using varying amounts of Perspex attenuator. The in vitro median lateral (x-axis) resolutions at the default bed height for the default scan types were 0.9 line pairs (lps)/mm for the 5 mA fast AP spine and femur scans, and l.0 lps/mm for 1 mA fast hand, forearm and 5 mA fast morphometry scans. This equates to a resolution of about 1 mm. The best resolution achieved was 1.2 lps/mm (0.83 mm), obtainable on all scan modes with the bed at maximum elevation, but only consistently with the forearm mode. Lower tube current did not affect resolution but did change the range of soft tissue thickness over which an image could be resolved. Turbo scan modes greatly reduced longitudinal (y-axis) resolution but had little effect on lateral resolution. This study demonstrates the importance of including an assessment of resolution when validating new equipment, especially if morphometric investigations are to be conducted. Received: 26 November 1998 / Accepted: 15 February 1999     

Evaluation of Differences Between Fan-Beam and Pencil-Beam Densitometers

We compared the bone and body composition results in vivo on two bone densitometers using fan-beam geometry (EXPERT and PRODIGY) with those using pencil-beam geometry (DPX). Measurements were made on large groups of adults ranging in weight from about 50 to 120 kg. Both spine and femur neck BMD on the fan-beam densitometers averaged within 1% of the pencil-beam results, and there was no magnitude dependence of the results by Bland-Altman analysis. Total body BMC and BMD on the PRODIGY and DPX were congruent, but on the EXPERT, BMC was about 2% lower and BMD 2% higher than corresponding values on the DPX. Soft-tissue composition was closely congruent for the PRODIGY and DPX; the comparable EXPERT-DPX differences showed greater scatter but no significant magnitude dependence. The smaller fan-angle of the PRODIGY (4°) probably contributed to its better congruence to pencil-beam results compared with the EXPERT (12°). Received: 23 February 2000 / Accepted: 14 April 2000 / Online publication: 27 July 2000