[Exposure distribution and total risk in intraoral source radiography]

Exposure distribution was measured and total risk for individual was estimated in intraoral source radiography. Equipment used was a stat Oralix (Philips). Film dosimetry was employed to obtain exposure distribution in oral mucosa and skin surface of head and neck region. A thermoluminescence dosimeter and an ionizing chamber were used to measure organ doses. Total risk was estimated on the basis of these doses. Conclusions 1. Exposure distribution 1) Oral mucosa Examination of upper jaw showed that exposure in palate was distributed between 100 mR near incisive papilla at hard palate and 1800 mR at the rear part of hard palate. Isodose curves were aligned at practically equal intervals from 100 mR to 600 mR. Curve of maximum dose 1800 mR ran forward in the vicinity of both second molars. Its pattern was not symmetrical on right and left side. Exposure in buccal region was distributed between 50 mR in the front part and 600 mR in the rear part. On both the surface of tongue and the inner side of mandible, low-exposure regions existed in the vicinity of the midline. Zones of higher exposure were to be found on right and left side. Examination of low jaw showed that isodose curves between 50 mR and 1000 mR were observed in right and left side of palatal area. Exposure in buccal region was distributed between 60 mR and 600 mR. Exposure at the center of tongue was 1800 mR, but it decreased to 1000 mR at the tip of tongue. High exposure was observed on both sides of tongue and mandible. Examination of lateral jaw showed that maximum exposure 1800 mR occurred on the side of radiation objective. In all three examinations, levels of exposure in oral mucosa were higher in the rear than in the front. Furthermore, exposure distribution was not symmetrical on right and left side. These results coincided with measurements of spatial patterns of x-ray intensity. In all examinations, lead-lining of applicator reduced exposure effectively. 2) Skin surface of head and neck region Examination of upper jaw showed that isodose curve of 10 mR ran through root of nose, eyelid, earlobe and mandibular angle ultimately to reach low lip. Curve of maximum exposure 100 mR was located in cheek region. Examination of low jaw showed that isodose curve of 10 mR descended through upper lip and earlobe ultimately to reach to lower part of thyroid gland. Curve of maximum exposure 100 mR was found in cheek region.(ABSTRACT TRUNCATED AT 400 WORDS)