As the glandular tissues within the female breast carry the greatest risk of radiation damage, the high-accuracy average dose received by these tissues in X-ray examination should be estimated. Because it is difficult to measure the average glandular dose received by the breast directly, we calculated conversion factors to obtain the average glandular dose from exposure in air by the following procedures.
The method was useful in some specific applications, allowing calculation of the high-accuracy glandular dose. First, we measured X-ray energy spectra from a molybdenum target with a molybdenum filter and from a rhodium target with a rhodium filter at several tube voltages using a high-purity germanium semiconductor radiation detector. We then calculated the exposure per fluence using the X-ray energy spectrum data, and computed the average glandular dose per photon in a semi-elliptical cylindrical breast model using the Monte Carlo method. Finally, we calculated the conversion factors from these numerical data. It was possible to calculate the average glandular dose with exposure in air. We conclude that the X-ray energy spectrum is important for calculating the average glandular dose rather than the half-value layer.

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For precise evaluation of a given dose of radiation, the conversion factors for an average glandular dose per exposure in air must be calculated after determining the average size of the compressed breast. We investigated the types of breast in terms of breast size and composition. The breast was assumed to have a semi-elliptical cylindrical shape in craniocaudal view. The results obtained were as follows ; 1) the radius at the chest wall side was 7.84 cm with a standard deviation (SD) of 1.15 cm, 2) the length from the posterior nipple to the chest wall was 6.19 cm (1.62 cm SD), 3) the thickness was 3.82 cm (1.25 cm SD), and the ratio of glandular tissue to adipose tissue was 42.8% (12.2% SD).
Using these data, the conversion factor was determined using the Monte Carlo simulation and the results were compared with data in the literature.
From this study, we recognized that we must first know the correct geometry of the breast. It should be in a position at which an appropriate measurement point for air Kerma or exposure can be determined to obtain the conversion factor. Above all, calculations need to take into account the thickness of the compression paddle, since this is always used in mammography.

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We compared breast cancer cases detected by mass screening using a combination of physical examination and real-time ultrasonographic whole-breast scanning of all individuals (hereafter referred to as the mass group ; 48 cases) with self-recognized cases of breast cancer (hereafter referred to as the clinic group ; 91 cases) that were treated surgically within the same period. A significantly higher proportion of the mass group (91.7%) had cancers that were detected at stage I of the TNM classification compared with the clinic group (p<0.01), and all premenopausal women in the mass group were revealed to have stage I tumors, which was significantly better than in the clinic group (p<0.05). Moreover, a significantly higher proportion of the mass group (20.8%) had non-palpable breast cancer compared to the clinic group (p<0.05), and the five-year and ten-year survival rates of the mass group were significantly better than in the clinic group.
Cases of non-palpable breast cancer detected as only a small hypoechoic area on ultrasonography accounted for 16.7% in the mass group. Among these cases, 25.0% were noninvasive carcinoma and 75.0% were invasive carcinoma. In the mass group, repeating participants (56.3%) tended to outnumber primary participants (43.7%). Also, non-palpable breast cancers tended to be detected more often by ultrasonography alone in repeating participants (22.2%) than primary participants (9.5%). Moreover, the majority of cancers in repeating participants (3.7%) tended to stay at early stage I, whereas 14.3% of those in primary participants showed aggravation from stage II to worse. Therefore, we confirm that it is important to perform breast cancer mass screening every year by ultrasonographic bilateral whole-breast scanning of repeating participants, and of course primary participants.

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In Ishikawa Prefecture, breast cancer screening has been conducted by physicians visiting the patients' communities. During a period of 18 years between 1978 and 1995, a total of 245, 705 women underwent initial/primary screening. Of these, an average of 2.8% required more detailed examination, and 85.3% of these actually did so. The rate of breast cancer discovery was 0.06%, and the total number of patients was 144. Comparison between the number of examinees who had initial and repeated screenings showed that early stages of breast cancer were combined with Tis and Stage I. Also, comparison of cancers found through screening with those found in outpatient clinics showed that early-stage and nO cases were more frequent among women who were screened. However, no significant difference in ten-year survival was noted between the groups.

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It is well recognized that breast self examination (BSE) is important in the mass screening of breast cancer. However, it is thought that patients with obesity might hesitate to perform BSE. We therefore examined the relationship between the frequency of BSE and grade of obesity as indicated by breast cap size in patients undergoing mass screening for breast cancer. Among postmenopausal patients (over 50 years old), fewer patients with obesity (65.8%) undertook BSE than non-obese patients (72.9%). The detection ratio for breast tumors less than 3 cm in diameter by BSE was 42.9% in obese patients and 84.2% in non-obese patients. This indicates that BSE is very important for detection of breast masses in postmenopausal patients with obesity.

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We studied in detail how long T3 breast cancer patients took before seeking diagnostic procedures, why their treatment was delayed and where the responsibility lay. Our study included 70 patients with T3 breast cancer whose tumors were 5 cm in diameter or more and who underwent surgery in our deparment at the Cancer Institute Hospital between 1992 and 1993. Of these patients, 31 (44.2%) took longer than 6 months from the appearance of initial symtoms to having treatment, resulting in possible progression of their clinical condition. In 21 (67.8%) of these, the delay was due to hesitation in initially visiting the clinic for advice, and in eight (25.8%) it was due to slowness of diagnostic procedures given by physicians. Twelve (38.7%) patients were responsible for their own personal efforts, whereas physicians or medical institutions were responsible in 7 (22.6%). Seven (10%) of the T3 breast cancer patients experienced delay in their diagnostic procedures, resulting in possible progression of their cancer. Accordingly, physicians or medical institutions who offer breast cancer treatment must be aware of their responsibilities.

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