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Biomedical subjects

A Y Cheung

Publications and source records attributed to A Y Cheung.

50 records · Page 3Linked to original sources
PubMed1984

Delayed effect of radiation therapy with or without chemotherapy on ovarian function in women with Hodgkin's disease.

In this retrospective investigation of 51 female patients with Hodgkin's disease, the age of the patient at the time of primary treatment and the extent of radiation therapy were the two most important factors determining post-therapy ovarian function. Favourable indicators of ovarian preservation included young age, especially premenarchal , at the time of primary therapy, and irradiation confined to above the pelvic brim, whereas, age over 40 and irradiation below the pelvic brim predicted high probability of ovarian failure. Overall, 55 per cent of female patients under the age of 50 treated with chemotherapy alone or with radiation therapy above the pelvic brim retained normal ovarian function. The stage of disease at presentation and the post-therapy status of disease had no apparent effect on subsequent menstrual function.

Adolescent↗
PubMed1984

Deep local hyperthermia for cancer therapy: external electromagnetic and ultrasound techniques.

External heating techniques for delivery of localized hyperthermia in patients are reviewed. This paper covers microwaves, radiofrequency, and ultrasound methods. Fundamental principles governing tissue absorption, guidelines for applicator selection and design, and restrictions of each heating approach are discussed. Innovative techniques utilizing multiple applicators to achieve better heating uniformity are also presented. The advantages and disadvantages of electromagnetic versus ultrasound heating techniques are compared as a conclusion to this review.

Electromagnetic Phenomena↗
PubMed1982

Thin-layer liquid crystal thermometry of cells in vitro during hyperthermal microwave irradiation.

A nonperturbing technique of thin-layer liquid crystal thermometry was developed to quantitate heating of Chinese hamster ovary cells and the bacterium Serratia marcescens when exposed to 2450-MHz microwave fields at 0.2-0.5 W/cm2. Cells suspended in culture medium were injected into 5-cm glass microcapillary tubes coated on the inside with a thin layer of liquid crystal. The tubes were sealed and placed parallel to the electric field in a watertight waveguide exposure chamber where they were heated by circulating temperature-controlled water. Even at high circulation rates, liquid crystal color changes indicated local microwave capillary tube heating of 0.1-0.25 degrees C. Precision of measurement was 0.02 degrees C. Observations during microwave heating were significantly different from observations without microwaves at the 1% level, and heating increased as circulating water flow was reduced from 300 ml/s to 100 ml/s. The results of a cell survival assay following hyperthermal treatment were in good agreement with expectations based on the observations of microwave heating using liquid crystals.

Animals↗
PubMed1982

Clinical local heating by microwaves.

The advantages and limitations of microwave heating in clinical thermotherapy are reviewed on the basis of the clinical experiences of various investigators who used microwave-induced hyperthermia. Also discussed are the clinical engineering system requirements necessary for conducting controlled clinical trials, as well as appropriate thermal treatment planning. Lastly, we present the future prospects for complex antennas and treatment control systems.

Clinical Trials as Topic↗
PubMed1982

Microwave and radiofrequency techniques for clinical hyperthermia.

Biological and practical constraints on the use of clinical hyperthermia for the management of cancer are discussed. Commonly used electromagnetic techniques for producing clinical hyperthermia are reviewed and compared. Innovative engineering designs leading to the realization of an integrated, safe and reliable clinical hyperthermia system are also presented.

Hot Temperature↗
PubMed1981

Prognostic significance of negative hysterectomy specimen following intracavitary irradiation in stage I endometrial carcinoma.

Clinical stage I endometrial carcinoma in 353 women was treated by pre-operative intracavitary irradiation with radium and total abdominal hysterectomy with bilateral salpingo-oophorectomy. No residual tumour was found in 36 per cent of uterine specimens obtained from hysterectomies performed within two weeks compared to 59 per cent of those removed later than eight weeks after the intracavitary irradiation. A negative hysterectomy specimen was a favourable prognostic index. Patients with no residual tumour in the hysterectomy specimens had a significantly lower five-years relapse rate (3.8 per cent) than those with residual tumour (19.2 per cent).

Adult↗
PubMedDate not supplied

Correction of microwave-induced thermistor sensor errors.

Accurate and reliable thermometry is essential in the development of microwave-induced hyperthermal cancer therapy. While temperature measurements in strong electromagnetic fields usually require special sensors, this does not hold true for interstitial radiator/sensor systems. Miniature thermistors (with metallic leads) bonded to invasive microwave applicators exhibit a sensor error linearly related to the radiator's transmitted power. This relationship permits thermistor sensor error correction and temperature measurements to within +/- 0.1 degrees C or better. The instrumental methods and empirical validation are presented.

Animals↗
PubMedDate not supplied

A new look at the sequential development of elbow-ossification centers in children.

The pattern and sequence of ossification of the six secondary ossification centers around the elbow in the child were mainly derived from studies done >30 years ago. This series reexamined the sequence and pattern based on a cross-sectional study of the elbow radiographs of 1,577 Chinese children with elbow injuries; age range, from newborn to 17 years. The ratio of girls to boys was 1:2. Each child had a radiograph of the normal and the injured elbow giving a total of 3,154 radiographs. A percentile chart of ossification was constructed for each of the ossification centers in both sexes for easy reference. No differences in the timing and ossification pattern were found between the right and left elbow or between the normal and injured elbow in this study. The sequence of ossification in both boys and girls was found to be the same (i.e., the capitulum first, followed by the radial head, medial epicondyle, olecranon, trochlea, and last, the lateral epicondyle). The ages at which 50% of the girls were found to have positive radiologic ossification for each of these centers were ages 1, 5, 5, 9, 9, and 10 years, respectively. In boys, with the exception of the capitulum, an average delay of 2 years was found in each of the ossification centers, although the sequence remained similar.

Adolescent↗