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Biomedical subjects

M M Chao

Publications and source records attributed to M M Chao.

4 recordsLinked to original sources
PubMed2001

Auditory abnormalities associated with unilateral renal agenesis.

OBJECTIVE: To evaluate the relationship between unilateral renal agenesis and auditory abnormality, and to determine the clinical spectrum of hearing impairment in such patients. METHODS: Seventy-five children with unilateral renal agenesis underwent auditory examinations. The subjects comprised 35 males and 40 females. Fourteen females had mullerian abnormalities. Another 75 schoolchildren with the same gender profile were selected for audiometric testing as a control group. Children with sonographically evident urogenital system abnormalities were excluded from the control group. RESULTS: The prevalence of auditory abnormalities in children with unilateral renal agenesis (4/75) (5.3%) was higher than in the control group (0%). The prevalence in children with urogenital anomalies was significantly higher in patients with renal agenesis than in the normal population (28.5%). Audiometric results showed that four of the 75 children manifested ipsilateral sensorineural hearing impairment, particularly in the high-frequency range. All were females with coexisting genital abnormalities. Two were diagnosed with mild sensorineural hearing impairment while the other two had moderate hearing loss. CONCLUSIONS: The results of our study suggest that neurosensory hearing loss was found to be associated with renal agenesis. Further audiometric follow-up of children with renal agenesis seems worthwhile.

Abnormalities, Multiple↗
PubMed2001

Image display for collision avoidance of radiation therapy: treatment planning.

Patient treatment in a medical linear accelerator is characterized by many angular and translational movements of the gantry and couch. The direction and orientation of each treatment beam is specified by a set of gantry, turntable, and collimator angles. It is possible that some selected treatment field configurations will result in gantry/couch or gantry/patient collisions that remain undetected during the treatment planning process. In this work, a digital camera has been used to record all the workable gantry/ patient set-up images, and a Windows programming language is used to edit and display these images on a personal computer for the treatment planner to screen the treatment plans. These graphical displays enable the planner to be aware of any potential collision hazards by an actual visualization of each selected gantry/turntable or gantry/patient angle configuration.

Accident Prevention↗
PubMed1996

Whole body radiation exposure with gamma unit radiosurgery.

BACKGROUND: Stereotactic radiosurgery is the use of external radiation in association with a stereotactic device to precisely locate and destroy inaccessible deep-seated lesions within the brain in a single treatment session. Very little attention has been paid to the extracranial sites of radiation exposure measurements. This study evaluates the extracranial absorbed dose due to leakage and scattered radiation of the Gamma Unit used in radiosurgery. METHODS: The absorbed doses were measured with thermoluminescent dosimetry (TLDs). Single and multiple Gamma Unit treatment with the 18mm collimator helmet was given and a Rando tissue equivalent phantom was in place to simulate a patient treatment. TLDs were placed on the phantom to measure the absorbed doses by the organs at risk. Two TLD chips were placed at each of the following organs: eye, thyroid, sternum and gonads. The irradiated TLDs were read with a Vinten TLD system 654D. The TLD factor was determined by irradiating TLDs with a cobalt-60 teletherapy unit of a known dose of radiation. RESULTS: The average maximum target absorbed dose was 30 Gy. The measured absorbed dose in selected organs from Gamma Unit radiosurgery with one or more isocenters was 21-53 cGy for the eye, 4-8 cGy for the thyroid, 3-4 cGy for the sternum and 2-3 cGy for the gonads. The dose to extracranial sites increased with the number of isocenters. The radiation dose to extracranial sites became much more substantial when multiple isocenters were used. CONCLUSIONS: The potential risk of radiation exposure is radiation induced tumors. No cases have been reported in patients treated with Gamma Unit radiosurgery. Given the benefit of Gamma Unit treatment, the clinical significance of these doses is minimal.

Brain Neoplasms↗