微波人体模拟肌肉组织的介电常数的测量

本文应用置于恒温槽内的样品填充式测量头和网络分析仪在４３３￣２４５０ＭＨｚ频带内测量液态或胶状材料（人工模拟组织）的复介电常数。本方法的优点是所需样品少，装填简单方便，便于快速测量和温度控制。特别适用于液态或胶状材料的介电常数的测定。     

Bone mineral measurement by CT apparatus with simultaneous use of reference phantom: Error factors and clinical evaluation

For the purpose of non-invasive quantification of trabecular mineral content of the third lumbar vertebra, quantitative computed tomography (QCT) using reference phantom was conducted. In order to minimize the error, the lumbar spine to be measured should be brought to the center of CT gantry, the phantom should be brought into close contact with the object for measurement, scanning should be carried out on 10mm slice thickness and the ROI (region of interest) should be taken as large as possible, according to our experience. Comparison of QCT values among various CT apparatus was difficult. This method was applied to the measurement of trabecular mineral content of the third lumbar vertebra. In 151 control subjects, the trabecular mineral content of the third lumbar vertebra decreased from the 3rd decade. In the initial adult period, females showed higher trabecular mineral content than males. A rapid loss of trabecular mineral content occurred between the 5th and 6th decade in females, so that after the 7th decade, males had higher trabecular mineral content than females. 47 patients with spinal osteoporosis and 16 patients with fracture of the femoral neck gave significantly lower trabecular mineral content than subjects in the same decade group without those conditions.     

Relief of pain from a phantom limb by peripheral stimulation

Summary In the present study, 24 patients suffering pain from a phantom limb were given vibratory stimulation or placebo as a pain-relieving measure. During stimulation, a reduction in pain was reported by 75% of the patients as compared to 44% during placebo. Depending on the phantom sensation, the best pain-reducing site was found to be either the area of pain or the antagonistic muscle. In 90% of the patients the best pain-reducing effect was obtained when stimulation was applied with moderate pressure over a large area. The results of the present study suggest that vibratory stimulation may be a valuable symptomatic treatment measure in patients suffering pain from a phantom limb.     

A motion artefact in real-time ultrasound scanners

Motion observed in real-time ultrasound images may be very misleading. The speckle pattern in images of soft tissue is an artefact and it may move in a way which bears no simple relationship to the motion of the tissues. The physical origin of this anomaly is described.     

Practical problems in neutron dosimetry

The first problem discussed is the best phantom material. It is argued that tissue composition has a greater effect on dose distributions from photons than on those from neutrons. As water is normally used for photons, it should be satisfactory for neutrons, but checks are needed with high-energy neutron beams. Another serious problem is that of kerma ratios for neutrons above 20 MeV where highly discordant values have been calculated by several authors. Finally some suggestions are made about measurement of the gamma-ray component in beams of high-energy neutrons.     

Frequency independent ultrasound contrast-detail analysis

An ultrasound contrast-detail phantom has been developed to evaluate the image quality of diagnostic ultrasound imaging systems. The phantom includes eight conical targets whose B-mode images show disk lesions such that the object contrast of each lesion relative to background is independent of the imaging device or transducer frequency/spectrum. By maintaining conditions for Rayleigh scattering and Rayleigh speckle statistics in the phantom gel, the object contrast of each lesion depends only on the scatterer concentration in the lesion relative to the scatterer concentration in the background. Experimental data confirmed this frequency independence. Results of contrast-detail performance of an ultrasound imaging system are shown, and a standard technique for error analysis of contrast-detail data is described.     

Achievement of transsaccadic visual stability using presaccadic and postsaccadic visual information

While saccadic eye movements produce rapid shift of images of objects on the retina, the visual world is perceived as stationary (visual stability), but the precise mechanisms involved in such perception remain unclear. We investigated if visual stimuli existing before and/or after a saccade serve to preserve visual stability. Participants observed a vertical array of light-spots flashing consecutively at the time of horizontal saccades. When total duration of the flashing array was short (38 ms), large distortions of the array were observed. However, as duration increased up to 300 ms, distortion decreased or was completely eliminated. This demonstrated that visual images of a flashing array momentarily perceived before and/or after saccades suppressed illusory distortion of arrays observed when a 38-ms array was used, implying that the same mechanism may be used to achieve transsaccadic visual stability in daily life.     

Defining the limits of flicker defined form: effect of stimulus size, eccentricity and number of random dots

We investigated the spatio-temporal limits of flicker defined form (FDF) phase contrast thresholds generated from the phantom contour illusion. Random dots (diameter 0.25 degrees, tapered edge) were used throughout the test field. FDF was generated using circular stimuli (temporal frequency 30 Hz, mean background luminance 50 cdm(-2)), the edges being defined by illusory borders generated from the out-of-phase dots within the display. Thresholds improved with increasing stimulus size and number of random dots at all eccentricities. For a constant threshold, fewer random dots were required with increasing eccentricity. Predictive mathematical relationships between contrast threshold, stimulus size and random dot number are discussed.     

位相对比乳腺摄影与全数字化乳腺摄影影像质量的比较研究

目的 探讨和比较位相对比乳腺摄影(Phase-contrast Mammography,PCM)与全数字化乳腺摄影(Full Field Digital Mammography,FFDM)的影像质量.方法 选用ACR RMI-156模型,分别于PCM乳腺摄影机与FFDM乳腺摄影机拍摄,除自动曝光条件,其余选用的曝光条件...     

Accuracy of Real-Time Single- and Multi-Beat 3-D Speckle Tracking Echocardiography In Vitro

With little data published on the accuracy of cardiac 3-D strain measurements, we investigated the agreement between 3-D echocardiography and sonomicrometry in an in vitro model with a polyvinyl alcohol phantom. A cardiac scanner with a 3-D probe was used to acquire recordings at 15 different stroke volumes at a heart rate of 60 beats/min, and eight different stroke volumes at a heart rate of 120 beats/min. Sonomicrometry was used as a reference, monitoring longitudinal, circumferential and radial lengths. Both single- and multi-beat acquisitions were recorded. Strain values were compared with sonomicrometer strain using linear correlation coefficients and Bland–Altman analysis. Multi-beat acquisition showed good agreement, whereas real-time images showed less agreement. The best correlation was obtained for a heart rate 60 of beats/min at a volume rate 36.6 volumes/s.