USE OF EXTENDED FOCUS-TO-FILM-DISTANCE TECHNIQUE FOR DOSE REDUCTION IN THE DIAGNOSTIC EXAMINATION OF THE PELVIS
USE OF EXTENDED FOCUS-TO-FILM-DISTANCE TECHNIQUE FOR DOSE REDUCTION IN THE DIAGNOSTIC EXAMINATION OF THE PELVIS
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Date
2007-12
Authors
SIMON, MADUAKONAM NWAFOR
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Abstract
It is essential to reduce the radiation exposure in diagnostic radiology as much as possible
because of their inherent danger. This is kwon as ALARA principle. The process of
reaching the balance between dose and image quality is optimization. This work is aimed
at finding if there are reductions in dose to the pelvis due to a change in focus to film
distance (FFD) with the condition that a diagnostic image of the pelvis is obtained. The
different examinations involving the direct irradiation of the gonads were studied for the
period of six months in the Radiology Department of Ahmadu Bello University Teaching
Hospital, Zaria to determine the contributions of pelvic exposure to patient’s radiation
hazards. It was found that examinations’ involving the pelvis contributes about 24% of
the total collective detriment to the patients. Entrance skin doses were measured using
patients and a constructed pelvic phantom by thermoluminescent dosimeters (TLD). Dose
to the pelvis was measured at varied FFD from 100145cm. Optical densities were
measured at positions of the ovaries and the result showed no significant difference. The
radiographs obtained at varying FFDs were found to be of good quality after their
assessment by clinicians. The increase in FFD showed dose reduction of 8.95% and
6.30% for fixed and varying collimation settings respectively. The backscatter factor was
found to be constant and the percentage reduction in dose due to air attenuation was
shown to be significant
Description
A Thesis Submitted to the Postgraduate School, Ahmadu Bello
University, in Partial Fulfillment of the Requirement for the Award of
Degree of Master of Science in Radiation Biophysics
Department of Physics, Faculty of Science
Ahmadu Bello University, Zaria
Nigeria
DECEMBER, 2007
Keywords
USE OF EXTENDED FOCUS-, TO-FILM-DISTANCE, TECHNIQUE, DOSE REDUCTION, DIAGNOSTIC EXAMINATION, PELVIS