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Biomedical subjects

P Xue

Publications and source records attributed to P Xue.

33 records · Page 2Linked to original sources
PubMed1994

Perception of fluoroscopy last-image hold.

Last-image hold (LIH) is used in x-ray fluoroscopy systems as a convenience and dose savings feature. In the case of an image sequence, temporal filtering in the human visual system (HVS) reduces perceived noise. In the case of a constant, single image frame, this phenomenon is not present: the image looks noisier, and low-contrast objects disappear. Using low-contrast, stationary cylinder and disk phantoms in noise, perception of single frames are compared with that of conventional 30 acq/s continuous fluoroscopy (continuous). The dose of continuous is fixed at Q/acq, and the dose of single-frame presentations is varied in order to determine an "equivalent-perception dose" for a paired-comparison task. The equivalent-perception dose depends upon the shape and size of an object. As cylinder diameter increases from 1 to 21 pixels, the equivalent-perception dose decreases from 4.6 to 2.8 Q/acq. At equal equivalent-perception dose values, the relationship between cylinder and disk diameters are determined; a cylinder diameter of 10 pixels is roughly equivalent to a disk diameter of 20 pixels. For interventional angiography, an average equivalent-perception dose of approximately 3.5 Q/acq for a single-frame presentation is predicted. Thus processing by the HVS effectively reduces noise variance by a factor of 3.5, corresponding to an effective averaging time of 3.5 frames or 120 ms. Several variance reduction techniques are suggested to create an LIH frame having perception equal to the fluoroscopy sequence.

Biophysical Phenomena↗
PubMed1994

Perceptual comparison of pulsed and continuous fluoroscopy.

Pulsed fluoroscopy (hereafter called pulsed) at reduced acquisition rates, typically 15 acq/s (pulsed-15), is proposed to reduce x-ray dose in interventional procedures. However, since the human visual system (HVS) acts as a temporal low-pass filter that interacts with such acquisitions, the proper dose for pulsed must be obtained in perception experiments. We determine the dose for low-frame-rate pulsed that gives visualization equivalent to that of conventional 30 acq/s fluoroscopy, hereafter called continuous. Computer-generated phantoms are used. They consist of stationary, low-contrast disks on a flat background containing Poisson noise that mimics quantum noise in fluoroscopy. Image sequences are displayed on the video tachistoscope, a device with considerable display flexibility. Three experimental paradigms are used. (1) In a paired-comparison study, pulsed and continuous are displayed side-by-side on the same monitor, and the visibility of a contrast detail phantom is compared. (2) Using this same display, subjects record the minimally detectable disk contrast (the min-contrast measurement). (3) In a four-alternative forced-choice experiment, a disk is placed in one of four positions, and the subject determines the position of the disk. The methods are complementary--the forced-choice experiment properly eliminates the subjectivity of the observer threshold while the paired-comparison study is much more time efficient. With regard to pulsed and continuous comparisons, remarkable similarity is found between the supra-threshold experiments (1 and 2) and the detectability experiment (3); i.e., the average absolute differences in the equivalent-perception dose as determined by the three measures is approximately 3%. No difference is found between interlaced and noninterlaced display. A relatively small dependence of dose savings on disk size is found with larger disks giving increased dose savings. Average dose savings of 22%, 38%, and 49% are found for pulsed-15, pulsed-10, and pulsed-7.5, respectively.

Fluoroscopy↗
PubMed1994

Model for perception of pulsed fluoroscopy image sequences.

Pulsed fluoroscopy at reduced frame rates can be used to lower x-ray dose with equivalent detection (hereafter called equivalent perception) of low-contrast, stationary objects. Experimentally average dose savings of 22%, 38%, and 49%, for pulsed fluoroscopy at 15, 10, and 7.5 acquisitions per second, respectively, are documented. Dose savings depend on object size, with fewer savings for smaller objects. To explain these data, we extend the framework of an ideal observer with three models for the spatiotemporal response of the human visual system (HVS). They are model 1, separable; model 2, nonseparable; and model 3, nonseparable with internal observer noise. With no free parameters, model 1 predicts the average dose savings within a 3% difference but does not describe the effect of object size. Models 2 and 3 explain the influence of size, and model 3, with a single free parameter, fits the measurements best. Perception of pulsed fluoroscopy is thus well described in terms of spatiotemporal processing by the HVS.

Fluoroscopy↗
PubMed1993

Antisense oligonucleotide blocks progesterone-induced lordosis behavior in ovariectomized rats.

Antisense oligonucleotides were utilized to interfere with the synthesis of progesterone receptor. A specific aODN was shown to decrease significantly the levels of PR in the T47D cell line known to express the PR gene. The molecule described was proved to be effective in hindering the effect of progesterone on target gene expression in T47D cells. The aODN was then utilized in an in vivo study to test its efficacy on the female rat sex behavior. Its injection in the ventromedial hypothalamus significantly inhibited the estrous responsiveness induced by progesterone. This study provides a clear demonstration of the full involvement of PR in the manifestation of lordosis behavior and demonstrates the activity of an aODN as antiprogestative.

Animals↗
PubMed1993

[Impact on lymphocyte transformation with BCG different strains vaccination].

The authors compared the influence of BCG produced strains D1 and D2 vaccination on lymphocyte transformation of spleen lymphocytes from guinea pigs. The guinea pigs were divided into D1 strain vaccinated group, D2 strain vaccinated group and nonvaccinated group. The response of lymphocyte transformation of spleen lymphocytes from the three groups to the stimulation of PHA, ConA and PPD were compared at 3, 4, and 5 weeks following vaccination. It was shown that the lymphocyte proliferation of D2 strain vaccinated guinea pigs to the stimulation of PHA, ConA and PPD was higher than that of D1 strain vaccinated. The most sensitivity of immunized lymphocytes to PHA and ConA was at 4 weeks following vaccination. Lymphocytes proliferation to PPD at 5 weeks following vaccination was higher than that at 4 weeks. This study showed that the ability of D2 strain to elicit the CMI was more than that of D1 strain.

Animals↗
PubMed1990

A stability study of an opacity standard.

Three procedures were adopted to increase the stability of the Chinese National Opacity Standard so that the change in opacity was within a range of +/- 5%.

Bacterial Vaccines↗
PubMed1989

Microsurgical reversal of female sterilization. Long-term follow-up of 117 cases.

A prospective study of 117 consecutive microsurgical reversals of female sterilization from April 1981 to December 1984 was carried out to determine which factors affected the pregnancy outcome. Nylon sutures, 8-0, were placed through the muscularis and mucosal layers. A short abdominal incision was made. The patients were followed for 3.5 to 7.0 years. The term delivery, intra-uterine pregnancy, spontaneous abortion and ectopic pregnancy rates were 81.2%, 83.8%, 1.7% and 1.7%, respectively; two ectopic pregnancies occurred 14 and 24 months after the reversal procedures. We found that the time interval between sterilization and reversal and the methods of sterilization affected the pregnancy outcome. The success rate with intervals of less than five years was much higher than with intervals of more than five years; Pomeroy cases were more reversible than Uchida cases. We did not observe any influence of the anastomosis site on the pregnancy results. The term delivery rates for isthmus-isthmus, isthmus-ampulla and ampulla-ampulla anastomoses were 78.8%, 80.0% and 84.6%, respectively. Patients should be followed for two years at least to determine the pregnancy outcome as well as the occurrence of ectopic pregnancy.

Anastomosis, Surgical↗