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排序方式: 共有631条查询结果,搜索用时 906 毫秒
1.
目的:根据流体动力学平衡控释原理(HBS)研制了马来酸罗列酮胃漂浮型缓释片。方法;以体外释放度和漂浮情况为筛选指标,采用单因素考察和正交试验设计相结合, 对胃漂浮缓释片的处方、制备工艺及体外释放条件进行优化筛选;采用γ闪烁照相技术对优化处方的内漂浮情况进行胃内动态观察。结果:马来酸罗格列酮胃漂浮缓释片在释放介质中迅速起漂,持漂时间超过12h,12h达最大累积释放;初步确定在胃内滞留时间达3h以上。结论:优化处方的释放过程符合Higuchi方程,释放机制为异常扩散;胃漂浮片在胃滞时间明显长于普通片。 相似文献
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Thermal cameras are used in research laboratories to measure tissue temperature during laser irradiation. This study was an evaluation of the accuracy of a 3-5 microns thermal camera and two 8-12 microns cameras in detecting the maximum temperatures of small targets. The size of the targets was within the range of laser spot diameters which are used for vessel welding, angioplasty, and dermatology. The response to a sharp thermal edge was measured and analyzed for the three cameras, which had a scanning rate of 30 frames per second. The response of the 3-5 microns camera to reference black body targets of different sizes was also studied. It was found that the detector system required an average of 2.44 microseconds to reach 90% of maximum step response for the 8-12 microns system and 5.85 microseconds for the 3-5 microns system. With a 3 x telescope and a 9.5 inch focal distance close-up lens, the 3-5 microns camera underestimated the temperature of targets smaller than 2.0 mm because of its slow detector response. Although the 8-12 microns camera provides more accurate measurements due to its faster detector response, it still underestimates the temperature of targets smaller than 900 microns, when similar magnification and focal distance are used. Methods to compensate for the inaccuracies are discussed, including empirical correction factors and the inverse filtering technique. 相似文献
5.
David Townsend Terry Spinks Terry Jones Antoine Geissbühler Michel Defrise Maria Carla Gilardi Jon Heather 《European journal of nuclear medicine and molecular imaging》1989,15(11):741-745
An important feature of multi ring positron tomographs is the inter plane septa, the purpose of which is to reduce random and scattered coincidences. In general, such septa also eliminate the coincidence lines of response between pairs of detectors more than one ring apart. The operation of a camera without septa must result in an increase not only in the true coincidence rate, but also in the singles, and therefore in the dead time and randoms rate, and in the scattered coincidences. A configuration option in the coincidence hardware of the 8 ring, 15 slice ECAT 931/08-12 enables a full set of 64 sinograms to be acquired when the septa are removed. The detector normalisation and transmission data for studies with the septa out can be obtained using a rotating pin source. To take maximum advantage of the additional signal, the emission data must be reconstructed using a fully three dimensional reconstruction algorithm. This paper presents an analysis of some phantom studies acquired without septa and reconstructed in three dimensions. The results are compared with data acquired with septa for the same phantoms imaged under similar conditions. It is found that, with the septa removed, the signal to noise for a uniform, 20 cm diameter cylinder improves by a factor of 2.8 in the centre of the field of view, whereas in regions distant from the centre in the axial direction, the signal to noise decreases due to the increase in scatter and randoms. An improvement in signal to noise is observed in 6 cm of the 10 cm axial length of the tomograph.This article was presented at the 1st EEC workshop on accuracy determination in PET, January 19–20th. 1989 Pisa, Italy (COMAC-BME Concerted Project Characterization and Standardization of PET Instrumentation) 相似文献
6.
A. N. Chalazonitis MD Ph.D D. Koumarianos RT J. Tzovara MD P. Chronopoulos MD 《Journal of digital imaging》2003,16(2):216-229
Over the past decade, the technology that permits images to be digitized and the reduction in the cost of digital equipment allows quick digital transfer of any conventional radiological film. Images then can be transferred to a personal computer, and several software programs are available that can manipulate their digital appearance. In this article, the fundamentals of digital imaging are discussed, as well as the wide variety of optional adjustments that the Adobe Photoshop 6.0 (Adobe Systems, San Jose, CA) program can offer to present radiological images with satisfactory digital imaging quality. 相似文献
7.
对于科学研究工作来说,时间分辨率和空间分辨率都是十分重要的,在设计相应的图像处理系统时必须两者兼顾。对于生命科学及工业等领域而言,希望图像处理系统不仅有较高的时间分辨率,还要有较高的空间分辨率。本文提出一种利用多部CCD数码相机、采用移相法获取高分辨牢和高摄录帧率的技术,此技术可应用于普通CCD数码相机组成的复合摄录系统。 相似文献
8.
Issa Loutfi Patricia M. Chisholm Debbie Bevan John P. Lavender 《European journal of nuclear medicine and molecular imaging》1990,16(2):69-76
An indium 111-labelled mouse anti-rat T cell monoclonal antibody, MRC OX-19, was injected intravenously into rats to establish the usefulness of radiolabelled anti-lymphocyte antibodies in imaging lymphoid tissues. Antibody binding in vivo, measured by immunofluorescence analysis of cell suspensions made from lymphoid tissues, was detectable on lymphocytes in blood, spleen and lymph nodes. The extent of binding was time and antibody-dose dependent. Doses of antibody above 80 g/kg body weight resulted in modulation, i.e. loss of CD 5 (T 1) molecules from the cell surface, although the cells remained in the circulation. Modulation was demonstrable within 2 h and for at least 24 h after a single injection of antibody. Intravenous injection of111In-MRC OX-19 resulted in levels of in vivo binding comparable with those seen with unlabelled antibody. Scintillation imaging showed early splenic localisation persisting over 48h, a more gradual localisation in the lymph nodes seen clearly at 24 h and a steady background. Comparison of the in vivo distribution of labelled antibody and111In-tropolone-labelled lymphocytes showed that both could be used for external imaging of lymphocytes by scintillation camera. 相似文献
9.
S. D. Bell A. M. Peters 《European journal of nuclear medicine and molecular imaging》1991,18(2):87-90
Measurement of individual kidney glomerular filtration rate (IKGFR) from the gamma-camera technetium 99m diethylene triamine penta-acetic acid (99mTc-DTPA) renogram requires a continuous measurement of arterial activity. This is usually based on a region of interest (ROI) placed over the cardiac blood pool on the posterior view, with the assumption of negligible contamination from activity in the extravascular space of the chest wall. By injecting a small dose of technetium 99m human serum albumin (HSA) before the99mTc-DTPA in 12 patients undergoing routine renography, the contribution of extravascular activity to the total signal recorded over the cardiac blood pool was calculated to be 11.0% (SE 2.1%) 1.5 min after DTPA injection, rising to 35.1% (SE 2.5%) at 15 min. Subtraction of the time-activity curve recorded from a ROI of the same size over the right lung generated a pure blood signal as shown by almost identical HSA/DTPA signal ratios recorded in blood samples taken 5 min after HSA and 15 min after DTPA and from the gamma-camera at the corresponding times. The effect of using a cardiac blood pool time-activity curve uncorrected for extravascular activity was to overestimate IKGFR by an average factor of 1.17 (SE 0.03).
Offprint requests to: A.M. Peters 相似文献
10.
Crister Ceberg Ingemar Larsson Sven-Erik Strand 《European journal of nuclear medicine and molecular imaging》1991,18(12):959-963
Characterization of the count-rate performance of scintillation cameras should include not only the specification of count losses. At high count rates, there is also an image distortion due to the mispositioning of pile-up events. In this paper a simple and clinically relevant procedure to quantify this distortion is presented. The images of a square uniform technetium-99m phantom at high and low count rates are used. The fraction of the total counts being correctly positioned is determined as the peripheral count density divided by the total average count density. This ratio, corrected for the camera non-uniformity at low count rates, is called the positioning ability. According to the National Electrical Manufacturers' Association (NEMA), the system count rate performance with scatter should be reported as the measured count rate giving 20% count losses. In this paper it is suggested that this measure be complemented by a measure of the fraction correct positioned events at this count rate. This fraction, the high count rate positioning ability', can be easily and accurately measured using our method. The method has been tested on two different scintillation cameras. For one of them the high count rate positioning ability was determined as 91% at a measured count rate of 30000 s–1 with 20% count losses. For the other camera, the corresponding figures were 88% at 59000 s–1 and close to 100% at 38000 s–1, before and after the installation of a new pile-up rejection circuit, respectively.
Offprint requests to: C. Ceberg 相似文献