The quality correction in the air kerma dosimetry for Ir-192 using farmer type ionization chambers calibrated by Co-60 quality is required. In this study we determined quality factor (kappa u) of two ionization chambers of PTW-N30001 and N23333 for Ir-192 source using dosimetric method. The quality factors for energy spectrum of microSelectron were determined as kappa u=1.016 and 1.017 for PTW-N30001 and N23333 ionization chambers respectively. We applied quality factors in air kerma dosimetry for microSelectron source and compared with reference values. As a results we found that the differences between reference air kerma rate and measured it with and without quality correction were about -0.5% and -2.0% respectively.
Gamma Rays ; Reference Values

OBJECTIVE: The purpose of this work is to build a well-plate holder for in vitro gamma knife irradiation to cell lines and to verify its validity. METHODS: A well-plate holder for gamma ray irradiation to cell lines using gamma knife was made of acrylonitrile. Inside the holder, a hexahedral space was excavated to hold well plates. The actual radiation dose to cell lines was obtained by comparing the relative dose of the holder with the gamma knife quality assurance standard phantom. All parameters necessary for cell line irradiation were calculated using the commercial software, Leksell Gamma Plan(R) v5.32. Dose distribution was drawn to six and ninety-six wells to search for optimal parameters for cell line irradiation. RESULTS: The dose rate at the center of the well-plate holder was 94+/-4% of the standard phantom and resulting absolute dose at the central area was 2.1+/-0.1Gy/min. The dose distributions of our phantom was the same as that of the standard phantom in qualitative comparison using an image analyzing software. Appropriate isodose lines which fit with the practical situation were obtained with the 18mm collimator of the Gamma knife. CONCLUSION: Our results show that a well-plate holder for gamma knife irradiation is confident and accurate. It can be used for the study of in vitro cellular effects by gamma knife irradiation in the future.
Acrylonitrile ; Cell Line* ; Gamma Rays

The skin sparing effect associated with high energy x-ray or gamma ray beams may be reduce or lost under certain conditions of treatment. Current trends in using large fields. Shield carrying trays, compensating filters, and isocentric methods of treatment have posed problems of increased skin dose which sometimes become a limiting factor in giving adquate tumor doses. We used the shallow ion chamber to measure the phantom surface dose and the physical treatment variables for Co-60 gamma ray, 4MV and 10 MV x-ray beam. The dependence of percent surface dose on field sizes, atomic number of the shielding tray materials and its distance from the surface for 4, 10MV x-rays and Co-60 gamma ray is qualitatively similar. The use of 2 mm thick tin filter is recommended for situations where a low atomic number tray is introduced into the beam at distances less than 15 cm from the surface and with the large field sized for 4 MV x-ray beam. In case of Co-50 gamma ray, the lead glass tray is suitable for enhancement of skin sparing. Also, the filter distance should be as large as possible to achieve substantial skin sparing.
Gamma Rays ; Glass ; Skin* ; Tin

LYODURA(R) is commercial name of a cleaned, desantigenized, desenzymatised, rendered free of pyogenics, sterilized by gamma rays, and lyophilized dura. Frontalis suspension with LYODURA(R) was performed to a total of 16 patients(21 lids) of congenital ptosis with levator muscle function of 3mm or less in the ptbtic lid. The follow-up period ranged from 2 to 39 weeks with a mean of 19.6 weeks. Postoperative lid levels were judged good, fair, and poor. Good results occurred in 12 of 21 procedures(57.1 %) and fair results in 6 of 21 prqcedures(28.6%). The summation of these two indicates an overall satisfactory result of 18 of 21 cases(85.7%).
Follow-Up Studies ; Gamma Rays

LYODURA(R) is commercial name of a cleaned, desantigenized, desenzymatised, rendered free of pyogenics, sterilized by gamma rays, and lyophilized dura. Frontalis suspension with LYODURA(R) was performed to a total of 16 patients(21 lids) of congenital ptosis with levator muscle function of 3mm or less in the ptbtic lid. The follow-up period ranged from 2 to 39 weeks with a mean of 19.6 weeks. Postoperative lid levels were judged good, fair, and poor. Good results occurred in 12 of 21 procedures(57.1 %) and fair results in 6 of 21 prqcedures(28.6%). The summation of these two indicates an overall satisfactory result of 18 of 21 cases(85.7%).
Follow-Up Studies ; Gamma Rays

Electron contamination due to the interaction between radiation beam and material was analyzed for the factors such as source-skin distance(SSD), field size, tray characteristics and position of filter, which can affect the surface dose in Cobalt teletherapy. Surface dose in open beam was more influenced by SSD with increasing field size. Relative surface charge(RSC) increased with the use of tray(solid, circular hole, slotted), compared with open beam, which is thought to be doe to increased electron contamination of the tray. To reduce the surface dose, 0.4mm thick Lipowitz metal filter was used. Compared with open beam, RSC decreased by 8.8%, 11.3%, 13.3%, 16.6%, 19.3% and 21.7% for the field size of 5x5, 10x10, 15x15, 20x20, 25x25 and 30x30 cm2, respectively. On the contrary, use of Lipowitz metal filter increased RSC at 60cm or less SSD. Suface dose was effectively reduced with Lpowitz metal filter placed right below solid tray in Cobalt teletherapy.
Cobalt ; Gamma Rays* ; Silver Sulfadiazine

New measurement method for Sp factors (Phantom Scatter Factors) is presented. The theoretical development of the approach is disscused showing that Sp factors can be obtained from three measurements of ionnization in a blocked, reference field and open field. This method has been tested using 60Co gamma rays. The results were within 1% deviation between the theory and the experiment for the Sp facter. The new method does not need air measurement, and we could determine the Sp p factors with a small piece of block.
Gamma Rays ; Hepatocyte Growth Factor*

In this study the dosimetric evaluation for a biological sample irradiated by gamma rays from Cs-137 irradiator (Gamma Irradiator, Chiyoda Technol Co., Japan) was performed for radiobiological experiment. A spherical water with a diameter of 3 cm was assumed as a biological sample. The absorbed dose were determined by the air kerma based dosimetric calculation system. The theoretical and Monte Carlo calculations (MCNPX) were performed and compared to evaluate measured air kerma and determined absorbed dose respectively. As a result of comparison with theoretical calculation, the measured air kerma was in good agreement within 3.1% at the distance of 100 and 200 cm from the source. In comparison with Monte Carlo results the determined absorbed dose along the central axis was in good agreement within 1.9% and 3.7% at 100 cm and 200 cm respectively. Although the preliminary results were obtained in this study these results were used as a basis of dosimetric evaluation for radiobiological experiment. Extended study will be performed to evaluate the dose in various conditions of biological samples.
Axis, Cervical Vertebra ; Gamma Rays ; Water

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.
Animals ; Gamma Rays ; Head Protective Devices ; Rats

For prompt gamma ray imaging for biomedical applications and environmental radiation monitoring, we propose herein a multiple-scattering Compton camera (MSCC). MSCC consists of three or more semiconductor layers with good energy resolution, and has potential for simultaneous detection and differentiation of multiple radio-isotopes based on the measured energies, as well as three-dimensional (3D) imaging of the radio-isotope distribution. In this study, we developed an analytic simulator and a 3D image generator for a MSCC, including the physical models of the radiation source emission and detection processes that can be utilized for geometry and performance prediction prior to the construction of a real system. The analytic simulator for a MSCC records coincidence detections of successive interactions in multiple detector layers. In the successive interaction processes, the emission direction of the incident gamma ray, the scattering angle, and the changed traveling path after the Compton scattering interaction in each detector, were determined by a conical surface uniform random number generator (RNG), and by a Klein-Nishina RNG. The 3D image generator has two functions: the recovery of the initial source energy spectrum and the 3D spatial distribution of the source. We evaluated the analytic simulator and image generator with two different energetic point radiation sources (Cs-137 and Co-60) and with an MSCC comprising three detector layers. The recovered initial energies of the incident radiations were well differentiated from the generated MSCC events. Correspondingly, we could obtain a multi-tracer image that combined the two differentiated images. The developed analytic simulator in this study emulated the randomness of the detection process of a multiple-scattering Compton camera, including the inherent degradation factors of the detectors, such as the limited spatial and energy resolutions. The Doppler-broadening effect owing to the momentum distribution of electrons in Compton scattering was not considered in the detection process because most interested isotopes for biomedical and environmental applications have high energies that are less sensitive to Doppler broadening. The analytic simulator and image generator for MSCC can be utilized to determine the optimal geometrical parameters, such as the distances between detectors and detector size, thus affecting the imaging performance of the Compton camera prior to the development of a real system.
Clothing ; Gamma Rays* ; Isotopes ; Radiation Monitoring ; Semiconductors