Radiation skyshine from a 6 MeV medical accelerator
This study assesses the dose level from skyshine produced by a 6 MeV medical accelerator. The analysis of data collected on skyshine yields professional guidance for future investigators as they attempt to quantify and qualify radiation protection concerns in shielding therapy vaults. Survey measurements using various field sizes and at varying distances from a primary barrier have enabled us to identify unique skyshine behavior in comparison to other energies already seen in literature. In order to correctly quantify such measurements outside a shielded barrier, one must take into consideration the fact that a skyshine maximum may not be observed at the same distance for all field sizes. A physical attribute of the skyshine scatter component was shown to increase to a maximum value at 4.6 m from the barrier for the largest field size used. We recommend that the largest field sizes be used in the field for the determination of skyshine effect and that the peak value be further analyzed specifically when considering shielding designs. PACS numbers: 87.52.‐g, 87.52.Df, 87.52.Tr, 87.53.‐j, 87.53.Bn, 87.53.Dq, 87.66.‐a, 89., 89.60.+x
LETTER TO THE EDITOR
We report a case of painful, unilateral gynaecomastia following treatment with finasteride 1 mg/day for androgenetic alopecia in an otherwise well 20-year-old man on no other medication. Length of treatment was 4 months, and the breast enlargement was noted by the patient 2 months after commencement of therapy. Unilateral gynaecomastia was confirmed on clinical examination. Pain and tenderness in the breast completely resolved 4 weeks after stopping finasteride and most of the breast enlargement had resolved after 3 months. At 7 months the affected breast was noted to be slightly larger than the other breast. The patient also reported a decrease in ejaculate volume while on finasteride. Gynaecomastia has been reported as an adverse reaction to finasteride 5 mg/day used for the treatment of benign prostatic hypertrophy (mean age 69 years, incidence 0.4% after one year). Other reported adverse events at this dose include erectile dysfunction, decreased ejaculate volume and diminution of libido. In the largest trial reported on the use of finasteride 1 mg/day for men with androgenetic alopecia (mean age 33 years), disturbance of these three components of sexual function were the only significant adverse events observed for finasteride therapy at 1 mg/day. The pharmacological basis for gynaecomastia in finasteride-treated men is not presently known. Theoretically, finasteride could cause gynaecomastia by a reduction in serum dihydrotestosterone. Estradiol levels or eostrogen/ testosterone balance do not appear to be affected. A low serum testosterone level prior to treatment with finasteride 5 mg/day has been suggested as an identifiable risk factor for gynaecomastia. Finasteride-induced gynaecomastia is a benign condition which shows partial or complete resolution in 80% of cases after cessation of therapy. So far, there has been no reliable link between finasteride-induced gynaecomastia and breast cancer. Low-dose tamoxifen (10 mg/day) has been shown useful in treating painful gynaecomastia in patients receiving finasteride and allows them to continue with their anti5-areductase therapy.
On the primary barrier in diagnostic x-ray shielding.
The traditional approach to shielding design for diagnostic x-ray facilities has been to designate as primary barriers the floor and those walls on which the useful beam may impinge, and to ignore the attenuation provided by the patient, grid, cassette, cassette holder, and x-ray table in computing the required thickness of these barriers. The degree of attenuation provided by the aforementioned materials has been measured on three-phase x-ray equipment including a variety of modern x-ray tables, grids, and cassettes. The primary beam is shown to be attenuated by more than two orders of magnitude at 100 kVp by the x-ray tables tested prior to impinging on the floor (ignoring patient attenuation). If patient attenuation is included, the attenuation is more than three orders of magnitude. Transmission factors as well as lead and concrete equivalencies for the various attenuating materials have been determined and included in tabular form. Example calculations for a heavy work load show that only a modest amount of concrete is required in the floor as a primary barrier if attenuation by these materials is taken into consideration (less than 2.5 cm at 80 kVp and less than 4 cm at 100 kVp) and the required secondary barrier may be thicker than the primary barrier.(ABSTRACT TRUNCATED AT 250 WORDS)