[Study on evaluation method of patient dose in diagnostic radiology required for introducing the guidance level: investigation of entrance surface dose of patient using direct measurement by TLD].

Using direct measurement, we investigated entrance surface doses of patients for routine radiographs in attempt to develop evaluation methods of patient dose in order to establish the guidance level in Japan. To date, patient doses have been evaluated by calculations based on radiographic conditions, or model experiments using phantoms. Their patient doses are then evaluated based on several assumptions. Direct measurement of patient dose is difficult to perform in many patients due to its time requirement, level of expertise required and difficulty in providing an explanation of the procedure to the patient. However, such direct measurement is essential since it incorporates all aspects of radiography from the radiographic equipment used, to the actual conditions of each patient without assumption. In this study, we examined the (1) need for introducing the guidance level, (2) controversial points in the calculation method for patient dose evaluation, (3) evaluation accuracy required for introducing the guidance level, and (4) necessity for a standardized method.