Intracavitary brachytherapy combined hypertermin for utero-cervical cancer seems to be a promising method for salvage treatments in persistent tumors and inoperable or previously irradiated cervical recurrences. In order to heat the vaginal apex and uterus, powerfull conical antennas which are suitable for afterloading cervical applicator have been designed for use in conjuction with intracavitary radition therapy. The antennas were constructed with conical conductive material to feed line and the effective length were designed proportional to microwave length, Power deposition profiles of 2450 MHz of conical antennas were studied in both phantom models and muscle tissue and compared to those of commonly used dipole antenna. Improvement of the heating pattern was found in both phantom and muscle tissue. The heating pattern produced by the conical antenna resembles an ellipsoid and then the temperature distribution in depth was extended to 2~3cm from the effective antenna axis.
Axis, Cervical Vertebra ; Brachytherapy ; Heating ; Hot Temperature ; Microwaves* ; Recurrence ; Uterus

Dosimetry based on electron spin resonance(ESR) analysis of radiation induced free radicals in amino acids is relevant to biological dosimetry applications. Alanine detectors are without walls and are tissue equivalent. Therefore, alanine ESR dosimetry looks promising for use in the therapy level. The dose range of the alanine/ESR dosimetry system can be extended down to l Gy. In a water phantom the absorbed dose of electrons generated by a medical linear accelerator of different initial energies (6~21 MeV) and therapeutic dose levels(1~60 Gy) was measured. Furthermore, depth dose measurements carried out with alanine dosimeters were compared with ionization chamber measurements. As the results, the measured absorbed doses for shallow depth of initial electron energies above 15 MeV were higher by 2~ 5% than those calculated by nominal energy CE factors. This seems to be caused by low energy scattered beams generated from the scattering foil and electron cones of beam projecting device in medical linear accelerator.
Alanine ; Amino Acids ; Free Radicals ; Particle Accelerators ; Spectrum Analysis* ; Water

No abstrac available

PURPOSE: This study was performed for adequate irradating tumor area when 6 MV linear accerelator photon was used to treat the head and neck tumor. The skin surface dose and maximum build-up ragion was measured by using a spoiler which was located between skin surface and collimator. METHODS: A spoiler was made of tissue equivalent materials and the skin surface dose and maximum build-up region was measured varing with field size, thickness of spoiler and interval between skin and collimator. The results of skin surface dose and maximum build-up dose was represented as a build-up ratio and it was compared with dose distribution by using a bolus. RESULTS: The skin surface dose was increased with appling spoiler and decreased by distance of the skin-spoiler separation. The maxium build-up region was 1.5 cm below the skin surface and it was markedly decreased near the skin surface. By using a 1.0-cm thickness spoiler, Dmax moved to 5, 10.2, 12.3, 13.9 and 14.8 mm from the skin surface by separation of the spoiler from the skin 0, 5, 10, 15, 20 cm, respectively. CONCLUSION: The skin surface dose was increased and maximum build-up region was moved to the surface by using a spoiler. Therefore spoiler was useful in treating by high energy photon in the head and neck tumor.
Head* ; Neck* ; Skin*

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

The use of high dose rate remote afterloading system for the treatment of intraluminal lesions necessitates the need for a more accurate of dose distributions around the high intensity brachytherapy sources, doses are often prescribed to a distance of few centimeters from the linear source, and in this range the dose distribution is very difficult to assess. Accurated and optimized dose calculation with stable numerical algorithms by PC level computer was required to treatment intraluminal lesions by high dose rate brachytherapy system. The exposure rate from sources was calculated with Sievert integral and dose rate in tissue was calculated with Meisberger equation. An algorithm for generating a treatment plan with optimized dose distribution was developed for high dose rate intraluminal radiotherapy. The treatment volume becomes the locus of the constrained target surface points that is the specified radial distance from the source dwelling positions. The treatment target volume may be alternately outlined on a x-ray film of the implant dummy sources. The routine used a linear programming formulism to compute which dwell time at each position to irradiate the constrained dose rate at the target surface points whiles minimizing the total volume integrated dose to the patient. The exposure rate and the dose distribution to be confirmed the result of calculation with algorithm were measured with film dosimetry, TLD and small size ion chambers.
Brachytherapy ; Film Dosimetry ; Humans ; Programming, Linear ; Radiotherapy ; X-Ray Film

A docking intraoperative electron beam applicator system, which is easily docking in the collimator for a linear accelerator after setting a sterilized transparent cone on the tumor bearing area in the operation room, has been designed to optimize dose distribution and to improve the efficiency of radiation treatment method with linear accelerator. This applicator system consisted of collimator holder with shielded metals and docking cone with transparent acrylic cylinder. A number of technical innovations have been used in the design of this system, this docking cone gives a improving latral dose coverage at therapeutic volume. The position of 90% isodose curve under surface of 8 cm diameter cone was extended 4~7 mm at 12 MeV electron and the isodose measurements beneath the cone wall showed hot spots as great as 106% for acrylic cone. The leakage radiation dose to tissues outside the cone wall was reduced as 3~5% of output dose. A comprehensive set of dosimetric characteristics of the intraoperative radiation therapy applicator system is presented.
Metals ; Particle Accelerators

PURPOSE: Irradiation cones by using backscatter electrons are made for the treatment of superficial small lesions of skin, oral cavity, and rectum where a significant dose gradient and maximum surface dose is desired. METHODS AND MATERIALS: Backscatter electrons are produced from the primary electron beams from the linear accelerators. The design consists of a cylindrical cone that has a thick circular plate of high atomic number medium (Pb or Cu) attached to the distal end, and the plate can be adjusted the reflected angle. Primary electrons strike the metal plate perpendicularly and produce backscatter electrons that reflect through the lateral hole for treatment. Using film and a parallel plate ion chamber, backscatter electron dose characteristics are measured. RESULTS: The depth dose characteristic of the backscatter electron is very similar to that of the hard x-ray beam that is commonly used for the intracavitary and superficial lesions. The basckscatter electron energy is nearly constant and effectively about 1.5 MeV from the clinical megavoltage beams. The backscatter electron dose rate of 35~85 cGy/min could be achieved from modern accelerators without any modification. and the depth in water of 50% depth dose from backscatter electron located at 6mm for 45degrees angled lead scatter. The beam flatness is dependent on the slit size and the depth of treatment, but is satisfactory to treat small lesions. CONCLUSIONS: The measured data for backscatter electron energy, depth dose flatness dose rate and absolute dose indicates that the backscatter electrons are suitable for clinical use.
Mouth ; Particle Accelerators ; Rectum ; Skin ; Strikes, Employee ; Water

Increasing frequency of skin cancer, mycosis fungoides, Kaposi's sarcoma etc, it need to treatment dose planning for total skin electron beam (TSEB) therapy. Appropriate treatment planning for TSEB therapy is needed to give homogeneous dose distribution throughout the entire skin surface. The energy of 6 MeV electron from the 18 MeV medical linear accelerator was adapted for superficial total skin electron beam therapy. The energy of the electron beam was reduced to 4.2 MeV by a 0.5cm x90cm x180cm acryl screen placed in a feet front of the patient. Six dual field beam was adapted for total skin irradiation to encompass the entire body surface from head to toe simultaneously. The patients were treated behind the acryl screen plate acted as a beam scatterer and contained a parallel-plate shallow ion chamber for dosimetry and beam monitoring. During treatment, the patient was placed in six different positions due to be homogeneous dose distribution for whole skin around the body. One treatment session delivered 400 cGy to the entire skin surface and patients were treated twice a week for eight consecutive weeks, which is equivalent to TDF value 57. Instrumentation and techniques developed in determining the depth dose, dose distribution and bremsstrahlung dose are discussed.
Foot ; Head ; Humans ; Mycosis Fungoides ; Particle Accelerators ; Sarcoma, Kaposi ; Skin Neoplasms* ; Skin* ; Toes

In capacitive heating device, which considered efficient for deep heating, parallel arrangement of the electrodes is a serious limiting factor in heating for eccentrically located lesions because it causes overheating of the exposed ipsilateral skin surface, the heating pattern is also frequently inappropriate, arid the arrangement tends to be unstable due to the patient's gravity. Therefore we attempted an angular arrangement of the electordes to achieve more homogenous and efficient heating for such lesions. In phantom study, both the thermal profile and thermogram established the heating pattern in this unusual angular arrangement of the electrodes at 60degree, 90degree and 120degree angles, respectively. An angular arrangement was also clinically applied to 3 patients. The patients' tolerance was good without significant complication and the thermal distribution was satisfactory. In conclusion, this unusual arrangement of electrodes appears to be promising in the clinical application to the eccentrically located lesions.
Electrodes* ; Gravitation ; Heating* ; Hot Temperature* ; Humans ; Skin