Development of a Stereotactic Device for Gamma Knife Irradiation of Small Animals

OBJECTIVE: The authors developed a stereotactic device for irradiation of small animals with Leksell Gamma Knife(R) Model C. Development and verification procedures were described in this article. METHODS: The device was designed to satisfy three requirements. The mechanical accuracy in positioning was to be managed within 0.5 mm. The strength of the device and structure were to be compromised to provide enough strength to hold a small animal during irradiation and to interfere the gamma ray beam as little as possible. The device was to be used in combination with the Leksell G-frame(R) and KOPF(R) rat adaptor. The irradiation point was determined by separate imaging sequences such as plain X-ray images. RESULTS: The absolute dose rate with the device in a Leksell Gamma Knife was 3.7% less than the value calculated from Leksell Gamma Plan(R). The dose distributions measured with GAFCHROMIC(R) MD-55 film corresponded to those of Leksell Gamma Plan(R) within acceptable range. The device was used in a series of rat experiments with a 4 mm helmet of Leksell Gamma Knife. CONCLUSION: A stereotactic device for irradiation of small animals with Leksell Gamma Knife Model C has been developed so that it fulfilled above requirements. Absorbed dose and dose distribution at the center of a Gamma Knife helmet are in acceptable ranges. The device provides enough accuracy for stereotactic irradiation with acceptable practicality.

Clinical Evaluation of Acne by Cross Polarizing Photography / 대한피부과학회지

BACKGROUND: Photography is one of the most objective methods in the clinical evaluation of acne. To standardize the quality of photographs, it is essential to standardize variables including focus distance, exposure time, posture and removal of flash glare but this is still insufficient. Cross polarizing photography (CPP) with a stereotactic device (STD) is a possible solution. OBJECTIVE: This study was conducted to determine the feasibility of photographic assessment using CPP with STD instead of direct inspection in Korean acne patients. METHODS: Sixty patients with acne (mean age=23.4, M=29, F=31) were enrolled in this study. Pictures using CPP with STD were taken three times during a 4-week period. Inflamed acne lesions that were counted at each visit were compared to the photographic assessment in a double-blind manner. To assess the quality of the picture, conventional photographs using a digital camera were also taken. RESULTS: The coefficient of correlation between direct lesional counting and photographic counting was 0.80. Photographic counting showed slightly higher results than direct counting. There was also a high coefficient of correlation (ranging from 0.78 to 0.85) among the inter-rater correlation which was 0.92. Photographs taken by CPP with STD showed an excellent quality in evaluating inflamed lesions of acne. Reduced glare and exact posture allowed for the detection of subtle lesions, that could not be seen in conventional pictures. CONCLUSION: Photography using CPP with STD is an objective, convenient and reproducible method for Korean acne patients. This method can be applied in evaluation of therapeutic response in clinics and clinical studies.