The large potential for patient dose reduction in the UK became evident when a nation patient dose survey conducted by NRPB in the early 1980s, revealed wide variations in practice. NRPB then collaborated with the professional organisations of radiologists, radiographers and medical physicists to produce advisory documents on patient dose reduction and measurement in diagnostic radiology. They included guideline reference doses for common types of examination against which X-ray departments could compare their performance. Following this advice, the results of over 50,000 patient dose measurements made at 375 hospitals were sent to. NRPB's national database by the end of 1995. The mean doses for each type of examination were seen to have fallen by about 30% since the earlier survey and only about 10% of hospitals still exceed the reference dose levels, indicating a substantial saving in the collective dose to the population from medical X-rays. However, the rapid increase in the use of high-dose computed tomography (CT) over the past decade has led to an increase in the collective dose, which will more than overweigh the reduction observed for conventional X-ray examinations. Correct application of the ICRP radiation protection principles of justification and optimisation does not necessarily require a lowering of the collective dose from such a potentially beneficial use of ionising radiation as diagnostic radiology. To maximise the margin of benefit over harm may require greater provision of diagnostic radiology services in appropriate areas resulting in a higher collective dose but a higher net health benefit to the population.

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Among the various quality assurance tests carried out on X-ray machines i" a radio-diagnosis department, kVp measurement is an important one. Unfortunately, the commercially available instruments for . ' measuring kVp are very expensive and generally unaffordable by small radiodiagnostic centres. A simple kvp, penetrameter and a home made optical densitometer have been used to study a total of 15 X-ray machines. The study shows that the simple penetrameter and the optical densitometer are useful and economical tools for checking kVp in small X-ray units.

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This paper focuses on dose uniformity in a body during total body irradiation. A composition of lateral and anterior-posterior (AP/ PA) fields divided into 8 fractions during four consecutive days was used. The total dose of 12 Gy was delivered with a dose rate of 6-98 cGy / min (lateral) and 17.75 cGy / min (AP / PA). The error of the dose delivery process is estimated at 2.8% to 5%. Doses were calculated along the body midline and in chosen transverse cross-sections at the points on beam to body entry and exit. Dose in-vivo verifications have been performed with thermoluminecent, semiconductor and ionization dosimeters. The need for providing additional fields with the aim of improving dose homogeneity is discussed and examples of reduced deviations along midline as well as across transverses are given. The doses in a group of 11 patients are presented together with their deviations along the body midline and across transverse sections.

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Breast malignancy is generally managed by surgery, post operative radiotherapy and chemotherapy. In radiotherapy, physical parameters for breast, being quite varied, show a wide range of diversity, which is because of irregular contour and obliquity of the breast chest wall. All these call for a deep insight into various parameters to get familiar with them for better execution and reproducibility of the treatment.

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