Radial cortical and trabecular bone densities of men and women standardized with the European forearm phantom

We previously showed that it is possible to cross-calibrate peripheral bone densitometers using the European Spine Phantom (ESP). We have now performed a multinational study of cross-calibrated radius bone density based on normal subjects of both sexes in eight European centers. Six centers were equipped with machines made by Scanco or Stratec for determining distal radial trabecular bone density by quantitative computed tomography (QCT) and two were equipped with Lunar SP2 single photon absorptiometry (SPA) equipment for measuring midshaft cortical bone density. Subjects recruited ranged from 20 to over 80 years of age. Over one hundred and fifteen men were studied by QCT and a different cohort of 104 men were studied with SPA; the equivalent figures for women were 235 and 123. Reference ranges were derived for bone density against age for each of the four groups, and their applicability is discussed in relation to between-center differences in the results obtained. There were insignificant differences (P>0.05 with Bonferroni correction) between centers in the values obtained by QCT in the different populations. However, there were considerably larger and highly statistically significant differences between midshaft cortical bone density values of about 10% of overall means between subjects from eastern Finland and central Belgium (P<0.001), with higher Finnish values. Women had considerably lower radial trabecular bone density values than men at all ages, a result that differentiates the radius from the spine. This sex difference widened after menopause. These results have important implications for understanding the contribution of bone density to the differential risk of Colles' fracture in the two sexes and suggest that further work is needed to establish young normal reference ranges for radial bone density in Europe.     

Design and Characterisation of a Tissue Phantom System for Optical Diagnostics

We present an optical phantom system especially suited to investigating the generation and transport of laser-induced fluorescence in biological tissues. The phantom system consists of micrometre-sized particles of aluminium oxide, iron and coloured resin dispersed in a solid, transparent host (polyorganosiloxane), from which mechanically stable samples can be made. Mie theory is applied to predict the radiation transport parameters from the optical properties of the isolated components. The predictions are in good agreement with the results of integrating sphere measurements. The radiation transport parameters of the samples are reproducible and temporally stable. Received for publication 4 June 1997; accepted following revision 8 November 1997.     

Phantom design method for high-field MRI human systems.

A phantom design method suitable for high-field MRI based on the RF field wave characteristics of sample and experimental validations at 7.0 T and 3.0 T are presented. The RF field distribution in a phantom with a given RF coil system is primarily determined by the sample size relative to the wavelength inside the sample, and the ratio between the displacement and conduction currents. Experimental results demonstrate that the MR image intensity patterns associated with wave behavior in human samples at a given field strength can be reproduced with a phantom at the same or different field strengths once the dimension and penetration constant are scaled by the corresponding wavelength in the sample medium.     

参考体模和孤立性肺结节CT诊断的初步研究

孤立性肺结节（ＳＰＮ）是放射学常见的诊断难题，笔者应用生物医学工程技术，对参考体模和ＳＰＮＣＴ初步研究结果作报告。我们设计并制成参考体模和参考ＳＰＮ，能对任何密度的ＳＰＮ作为比较标准，评价所有的ＳＰＮ，参考体模用组织等效材料，仿真模拟胸部的解剖并组成四或五层的横断面。参考ＳＰＮ为各种大小的园柱形和不同的密度，应用ＣＴ能获得其生物物理参数（形态、大小、密度、三维座标等）这有利于ＣＴ诊断的质量保证（ＱＡ）和质量控制（ＱＣ）。     

A clinical application of an automated phantom-film QA procedure for validation of IMRT treatment planning and delivery

To quantify the correlation between planned and delivered intensity-modulated radiation therapy (IMRT) dose distributions, IMRT plans for 37 prostate carcinoma patients were analyzed. IMRT treatment plans were converted into hybrid phantom plans using a commercially available treatment planning system and delivered to a specialized film phantom via a static-tomotherapy technique. The films were analyzed using a commercial film dosimetry system. Hybrid phantom axial dose maps and film images were normalized, registered to one another, and subtracted to calculate the overall relative dose difference throughout the entire film area on a pixel-by-pixel basis. The average percentage of pixels with dose-difference values greater than ± 3% among analyzed hybrid patient plans was 8.6% ± 3%. The average percentage of pixels with dose differences greater than ± 5% was 1.7% ± 1.0%. The number of pixels with more than ± 10% dose differences was negligible. An initial subset of hybrid plans was used to develop a quantitative criterion to verify for positional accuracy based on dosimetric verification of intensity map of IMRT plans for prostate patients in our institution. Plans with less than 5% of the pixels outside the ± 5% dose-difference range were accepted. This method could be implemented for other anatomical sites or treatment planning and delivery systems. © 2003 American Association of Medical Dosimetrists.     

A new flood phantom to measure homogeneity of gamma cameras and to correct SPECT studies

A new flood phantom is presented. It combines patient like emission spectra, homogeneous activity distribution, and mechanical stability.Its properties and easy handling makes it the flood phantom of choice for measuring the homogeneity of a gamma camera or for correcting SPECT studies.     

A systematic approach towards the objective evaluation of low-contrast performance in MDCT: Combination of a full-reference image fidelity metric and a software phantom

Objectives

To assess the feasibility of an objective approach for the evaluation of low-contrast detectability in multidetector computed-tomography (MDCT) by combining a virtual phantom containing simulated lesions with an image quality metric.

Materials and methods

A low-contrast phantom containing hypodense spheric lesions (−20 HU) was scanned on a 64-slice MDCT scanner at 4 different dose levels (25, 50, 100, 200 mAs). In addition, virtual round hypodense low-contrast lesions (20 HU object contrast) based on real CT data were inserted into the lesion-free section of the datasets. The sliding-thin-slab algorithm was applied to the image data with an increasing slice-thickness from 1 to 15 slices. For each dataset containing simulated lesions a lesion-free counterpart was reconstructed and post-processed in the same manner. The low-contrast performance of all datasets containing virtual lesions was determined using a full-reference image quality metric (modified multiscale structural similarity index, MS-SSIM*). The results were validated against a reader-study of the real lesions.

Results

For all dose levels and lesion sizes there was no statistically significant difference between the low-contrast performance as determined by the image quality metric when compared to the reader study (p < 0.05). The intraclass correlation coefficient was 0.72, 0.82, 0.90 and 0.84 for lesion diameters of 4 mm, 5 mm, 8 mm and 10 mm, respectively. The use of the sliding-thin-slab algorithm improves lesion detectability by a factor ranging from 1.15 to 2.69 when compared with the original axial slice (0.625 mm).

Conclusion

The combination of a virtual phantom and a full-reference image quality metric enables a systematic, automated and objective evaluation of low-contrast detectability in MDCT datasets and correlates well with the judgment of human readers.