Evaluation on the guidelines of lead shield application to reduce patients' gonad doses in diagnostic radiological examinations using high sensitivity thermoluminescent dosemeters

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Evaluation on the guidelines of lead shield application to reduce patients' gonad doses in diagnostic radiological examinations using high sensitivity thermoluminescent dosemeters

 

Author: Lee, Tak-kee
Title: Evaluation on the guidelines of lead shield application to reduce patients' gonad doses in diagnostic radiological examinations using high sensitivity thermoluminescent dosemeters
Degree: M.Sc.
Year: 2003
Subject: Gonads -- Radiography
Thermoluminescence dosimetry
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Optometry and Radiography
Pages: xvi, 131 leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1691104
URI: http://theses.lib.polyu.edu.hk/handle/200/725
Abstract: Of all medical procedures, diagnostic X-rays contribute most to the genetically significant dose. Strict protective measures should be taken to avoid all unnecessary gonad exposures. Despite many recommendations to this effect, the guidelines of the placement of gonad shield are still ambiguous. This study was performed to determine the effectiveness of lead shield application on gonad dose reduction when the primary beam is 5cm away from the gonad region in selected radiological examinations. Gonad dose measurements were made in simulated common radiological examinations, from general radiological examinations, computed tomography (CT), fluoroscopy and angiography, using high sensitivity LIF:Mg,Cu,P thermoluminescent dosemeters (TLD) and the Rando phantom. Gonad doses with and without lead shield application were measured. Experiments were performed in the Radiography Clinic and the Radiation Dosimetry Laboratory of the Hong Kong Polytechnic University, and also in the Prince of Wales Hospital. Results showed that there were statistically significant differences (by paired t-test) in gonad doses for all the selected general radiological examinations between the projections with and without lead shield application. In CT, the lead skirt had statistically significant effect on the testicular dose reduction on the thorax (78%) and liver scan (42%) but not on the ovarian dose reduction. However, the lead shield had statistically significant reduction on both testicular (67%) and ovarian dose (30%) in the most commonly performed head CT scan. For barium swallow fluoroscopic examination, both testicular and ovarian dose had a statistically significant reduction with the application of the lead skirt (96% and 26% respectively). Only testicular dose had a statistically significant reduction (93%) in the barium meal study but not in ovarian dose. For cerebral angiography, there was a statistically significant reduction in ovarian dose (22%) with the application of lead shield but not in the testicular dose. For other selected angiographic examinations, there were statistically insignificant differences with the application of lead shield. Overall, for procedures with statistical dose reduction, with the application of gonad shield, dose reduction ranged from 42% to 97% and 16% to 47% in the testes and ovaries respectively. The distance between the primary beam and the testes ranged from 7.5cm to 73cm while that between the primary beam and ovaries ranged from 6.5cm to 60.5cm. It might infer that the radiation safety measures are not adequate at present from current local and international guidelines. The effectiveness of the gonad shield might depend on the practices, techniques and equipment in different departments. It may be the time for radiation protection authorities to re-evaluate the present guidelines and make new recommendations on the application of lead shield in general radiological examinations when the gonad regions are 5cm beyond the primary beam. When there is a statistically significant reduction in gonad dose, gonad shield should be applied. Moreover, ovarian doses from most of the selected examinations were higher than testicular doses. Results also suggested that except for chest X-ray projection and cerebral angiography, there was in general a relatively greater percentage of dose reduction with gonad shield application in male patients for the selected radiological examinations. It might be due to the varying relative proportions of the internal scatter radiation and leakage radiation, both of which affect gonad doses. Quality laboratory technique and the high sensitivity characteristic of the LiF:Mg,Cu,P TLD enabled the very low level gonad doses to be measured.

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