Search PubMed⌕ Search

Biomedical subjects

W K Chu

Publications and source records attributed to W K Chu.

10 recordsLinked to original sources
PubMed1992

Estimation of the mean effective organ doses for total body irradiation from Rando phantom measurements.

For the total body irradiation (TBI) procedure, it is necessary to compare the mean dose obtained from the tissue or organs and the estimated dose equivalent value from the computer program. Due to the easy-access of the Rando phantom and repeatability of TLDs and its output, the results from the experiment are quite encouraging for the verification of the dose distributions from total body irradiation at the given prescribed monitor units. The estimation of effective dose equivalent particularly across the lung sections was studied by combinations of using arms as the scatter volume to compensate for the inhomogeneity across the breast portion, as well as using the spoiler for skin-sparing purposes. The results were based upon various beam quality such as 4 MV, 6 MV, and 10 MV X rays. One series of experiments performed for this survey to ascertain the dose equivalent of the tissues was conducted. This paper describes the method and procedure for comparison between the measured data and computed data as a reference in the dosimetry of total body irradiation. Comparison of the measured and computed data for the largest collimated field shows that the calculated dose rates do not differ by more than 2% from the measured data. Because uncertainty is inherent in non-patient-like phantoms, the calculated data may be served as a reference for the dosimetry. For the total body irradiation setup, considering the radiation field size and treatment distances commonly employed, we conclude that the best combination of the patient setup will be (1) laying both arms down as compensation for lung inhomogeneity, and (2) the spoiler, which is made of acrylic about 8 mm thick and functions like a bolus, is needed to reduce the skin sparing effects and contribute the uniform dose distribution. The beam spoiler with the frame stands near the patient during the treatment.

Humans↗
PubMed1992

Hypertrophic response to unilateral concentric isokinetic resistance training.

The purposes of this study were to 1) determine the effect of concentric isokinetic training on strength and cross-sectional area (CSA) of selected extensor and flexor muscles of the forearm and leg, 2) examine the potential for preferential hypertrophy of individual muscles within a muscle group, 3) identify the location (proximal, middle, or distal level) of hypertrophy within an individual muscle, and 4) determine the effect of unilateral concentric isokinetic training on strength and hypertrophy of the contralateral limbs. Thirteen untrained male college students [mean age 25.1 +/- 6.1 (SD) yr] volunteered to perform six sets of 10 repetitions of extension and flexion of the nondominant limbs three times per week for 8 wk, using a Cybex II isokinetic dynamometer. Pretraining and posttraining peak torque and muscle CSA measurements for both the dominant and nondominant limbs were determined utilizing a Cybex II isokinetic dynamometer and magnetic resonance imaging scanner, respectively. The results indicated significant (P less than 0.0008) hypertrophy in all trained muscle groups as well as preferential hypertrophy of individual muscles and at specific levels. None of the muscles of the contralateral limbs increased significantly in CSA. In addition, significant (P less than 0.0008) increases in peak torque occurred for trained forearm extension and flexion as well as trained leg flexion. There were no significant increases in peak torque, however, for trained leg extension or for any movement in the contralateral limbs. These data suggest that concentric isokinetic training results in significant strength and hypertrophic responses in the trained limbs.

Adult↗
PubMed1991

Brachytherapy: a viable alternative in the management of basal meningiomas.

Thirteen patients with intracranial meningiomas of the skull base were treated with one or more high-activity iodine-125 seeds. In 11 patients, the seeds were implanted stereotactically under local anesthesia. A minimum dose of 100 to 500 Gy was delivered to the tumor at a dose rate of 5 to 25 cGy/h. Indications for this procedure included recurrence after initial surgery or as the primary modality of treatment in patients who were not candidates for surgery. All 13 patients are alive at a median follow-up of 15 months. Nine of 11 patients (82%) without calcification in their meningiomas achieved complete response. The remaining 4 patients-2 with calcification and 2 without--achieved partial response. No early or late complications were observed. We conclude from our experience that both recurrent and primary meningiomas of the skull base can be treated effectively with permanent iodine-125 brachytherapy.

Adult↗
PubMed1991

An image analysis on MR imaging of the brain for hepatic encephalopathy.

Through the Magnetic Resonance Imaging (MRI) sequences with T1 weighting (TR 600 msec/TE 20 msec) of the brain, the high intensity lesions due to hepatic encephalopathy have been demonstrated markedly. The data have been collected were based upon eleven patients with clinically proven hepatic encephalopathy. Three sets of normal brain MRI which were identified with no evidence of brain or liver diseases were also included in this study. After the brain MRI slices have been identified, it showed that the affected regions of interest (ROI) were around the largest third ventricle. The histogram which was generated out of that particular slice is composed of two distinguished peaks lumped together. After the decomposition and curve fitting procedures, the Gaussian distributions were identified with the mean value and the standard deviation. One was assumed to be gray index region for gray and white matter, the other with higher gray index value was the contribution of hepatic encephalopathy. Once the range of the distribution has been determined, the affected portion can be marked and highlighted. This mechanism of histogram decomposition and curve fitting techniques shows the valuable correlation with the clinical status of MR findings.

Brain↗
PubMed1990

Magnetic resonance imaging of the brain in infants and children before and after cardiac surgery. A prospective study.

We assessed the morphologic findings of the brain prospectively before and after cardiac surgery using magnetic resonance imaging. There were 12 patients with acyanotic and 6 with cyanotic heart disease. There were 2 deaths, and 1 patient did not have to undergo postoperative magnetic resonance imaging. The study group consisted of 15 patients completing both the preoperative and postoperative magnetic resonance imagings. All patients in the study group underwent moderate hypothermic cardiopulmonary bypass using a nonpulsatile membrane oxygenator. The mean (+/- SD) cardiopulmonary bypass time was 100 +/- 55 minutes. Ten of the preoperative studies were interpreted as normal. One third (5 of 15) of the patients showed ventriculomegaly and dilatation of the subarachnoid spaces on preoperative magnetic resonance images. Measurements of the preoperative and postoperative magnetic resonance images showed a postoperative increase in the bicaudate and third ventricular diameters. Four patients in the study group developed postoperative subdural hematomas. The subdural hematomas were small and caused no demonstrable mass effect on magnetic resonance imaging. One patient had a preoperative white matter infarction. There was 1 patient with a postoperative infarction.

Brain↗
PubMed1990

A microcomputer-based system for measurement of ultrasound imaging.

A microcomputer-based imaging system for acquisition and analysis of ultrasound has become available. In order to fulfill the clinical demands, the more complete and detailed examinations required, the more sophisticated ultrasound instrumentation costs. This paper demonstrates the simplicity of a personal computer to provide an inexpensive method for measurement on video images from a real-time ultrasound scanner. The process data obtained on ATL 600 and found acoustic intensity histograms to be of value in differential diagnostic purposes. It includes spatial filtering, gray scale expansion, contrast enhancement, color index shifting and histogram analysis, etc. It allows the computer graphics to be superimposed on the ultrasound video images and permits subsequent analysis. To perform the manipulations and programming one of commercially available software and hardware are outlined and encouraged.

Computer Graphics↗
PubMed1978

Fourier analysis of the echocardiogram.

Fourier analysis has been applied to the analysis of echocardiograms, with the result that anterior mitral leaflet waveforms have been classified in a manner which is unambiguous and which lends itself easily to present-day automated technology.

Echocardiography↗
PubMed1977

Toward the automation of echocardiography.

Schemes applicable to the automated classification of disease states identifiable through echocardiography are being studied. Initial success has been achieved in the classification of anterior mitral leaflet wave forms associated with mitral stenosis and mitral valve prolapse. These two categories were found to be readily distinguished from the normal state in a Fourier analysis framework.

Automation↗
PubMedDate not supplied

Echocardiogram analysis in a pattern recognition framework.

Echocardiogram analysis is treated in a pattern recognition framework. Anterior mitral leaflet waveforms are classified for the four-class problem consisting of the classes "normal," "mitral stenosis," "mitral valve prolapse," and "idiopathic hypertrophic subaortic stenosis." In addition, aortic root waveforms and left ventricular wall waveforms are classified for the two-class problem consisting of the classes "normal" and "idiopathic hypertrophic subaortic stenosis." One common method of analysis (Fourier analysis) underlies each classification scheme. Classification accuracy is sufficiently good to warrant the inference that successful automated decision-making based on the algorithms investigated is feasible.

Aortic Valve↗