ABSTRACT
BACKGROUND AND PURPOSE: The necessity for and the benefit of a quality assurance program in radiation oncology are not questioned. Nevertheless, a retrospective analysis of the accumulated results of several years of quality assurance offers the possibility for further optimization. MATERIALS AND METHODS: The results of the physical quality control in radiation treatment planning and on radiation treatment units in the Institute for Radiation Oncology at the University Hospital of Basel for the years 1985, 1991 and 1994 are analyzed and compared mutually. The frequencies of the deviations from the nominal values for the different tests are stated. RESULTS: The relevance of the deviations for the different parameters is rated and the manifested influence of the type and age of the equipment on the results of the quality assurance is discussed. CONCLUSIONS: A condition for the maximum benefit gained from the quality assurance is the oncologist's understanding of the necessity for regular checks and the urgency for eliminating the established deficiencies. In that way the accuracy for the treatment planning, simulation and set-up process and for the realization of the radiation treatment can be increased and the methods can be improved.
Subject(s)
Radiation Oncology/standards , Radiotherapy/standards , Hospitals, University , Humans , Quality Control , Retrospective Studies , SwitzerlandABSTRACT
Radiation therapy of tumors is often performed with high energy electrons. In certain situations air cavities in the irradiation volume can change the dose distribution. The effects of air cavities on the dose distribution are investigated. The results calculated with a therapy planning system and measured in a phantom are described and compared with one another and with the literature.
Subject(s)
Neoplasms/radiotherapy , Radiotherapy Dosage , Radiotherapy, High-Energy , Humans , Models, Structural , Particle Accelerators , Radiotherapy Planning, Computer-AssistedABSTRACT
Described are two methods of evaluation of the uptake of 35S by chondrosarcomas, i.e. autoradiography and external monitoring of the Bremsstrahlung. A higher concentration of sulfur in the tumor area of three patients was demonstrated after the injection of aliquots of both diagnostic and therapeutic activities. Apart from the simple handling and the quickly obtained results, the external monitoring of the Bremsstrahlung permits quantitative evaluation of the degree of uptake and a simple control over the progress of therapy.
Subject(s)
Chondrosarcoma/radiotherapy , Sulfur Radioisotopes/therapeutic use , Autoradiography , Bone Neoplasms/radiotherapy , Electromagnetic Phenomena , Hip Joint , Humans , Joint Diseases/radiotherapy , Radiation Monitoring/methods , Radioactivity , Sacrum , Soft Tissue Neoplasms/radiotherapy , Spinal Neoplasms/radiotherapyABSTRACT
The dose distribution within the patient was studied with 8-MeV bremsstrahlung from a linear accelerator during mantle field irradiation using molded shielding blocks. Doses and dose distributions in the different layers of a modified Alderson phantom were measured by means of film dosimetry and related to the dose in the central ray beam at the middle of the body. Dose distribution within unshielded regions perpendicular to the central ray beam generally being relatively homogeneous, the highest relative doses, amounting to ca. 115%, are found in the region of the mandibular angle and in the supraclavicular region; the dose to superficial lymph nodes at the supraclavicular region reaches 100% of the dose in the central ray beam. As a cause for these important doses near the surface of the body are discussed the extension of mantle fields as well as the increased exit dose of the opposed field and the oblique incidence of radiation.
Subject(s)
Radiotherapy Dosage , Humans , Jaw , Mathematics , Models, Biological , Neck , Particle AcceleratorsABSTRACT
Nine inflamed knee joints out of eight patients were examined before and after intraarticular injection of yttrium-90 silicate colloid, in order to find out the effect of radiation synovectomy on the perfusion of the joints. These joints and the untreated contralateral knee joints were examined as to the clinical status and the fast component Tf of the xenon-133 clearance was determined as a means of the perfusion of the synovium. A linear correlation exists between the clinical status of the knee joint and the perfusion as determined by Tf measured three months before and after injection of yttrium-90. Also the joints without any radiation synovectomy showed this correlation. Three months after radiation synovectomy with yttrium-90 there was still no therapeutic effect apparent in the majority of the inflamed knee joints (seven out of nine). At this stage there still existed a hyperaemia. Therefore, it seems that on the whole three months are too short a period to judge the therapeutic effect.
Subject(s)
Synovectomy , Xenon/metabolism , Yttrium Radioisotopes/therapeutic use , Adult , Aged , Arthritis, Rheumatoid/complications , Arthritis, Rheumatoid/therapy , Female , Humans , Hyperemia/etiology , Knee Joint/blood supply , Knee Joint/radiation effects , Male , Middle Aged , Synovial Membrane/radiation effects , Xenon RadioisotopesABSTRACT
During the irradiation with a continuous radiation of 8 MeV by the linear accelerator LINAC SL 75/10, the dose distribution of photons and neutrons was measured outside of the irradiation field. The dose distribution of photons was mostly determined by thermoluminescence dose meters. There was a significant maximum of leak radiation on the back of the emitter head which showed a dose rate amounting to 7,5% of the dose rate of the central ray. Whereas the leak radiation on the patients' table was less than 0,1% of the dose of the central ray, the dose of scattered radiation emitted by the patient still amounts to 2% of the central ray dose in a distance of 15 cm from the field edge. The isodoses measured in the room demonstrate above all the importance of the lock for a sufficient radioprotection.--The dose rate of the neutrons formed in the shielding material by photonuclear reactions were measured mostly with uranium fission-track dosimeters. The highest equivalent dose rate was found on the back of the emitter head; it is about 17 rem/h. The maximum value of the equivalent dose rate of neutrons on the patient's table amounts to 1,4 rem/h and is almost independent of the size of the diaphragm. The isodoses in the room depend largely on the shape of the irradiation room; they confirm the existence of a sufficient radioprotection.
Subject(s)
Neutrons , Nuclear Physics , Radiotherapy, High-Energy , Elementary Particles , Radiation Protection , Radiotherapy Dosage , Thermoluminescent DosimetrySubject(s)
Particle Accelerators , Radiotherapy, High-Energy , Fast Neutrons , Humans , Radiometry , Radiotherapy DosageABSTRACT
Investigations on patients and on phantoms were performed to determine the retention and the absorbed dose in radiation synovectomy with 90Y silicate colloid. The electrons of 90Y are totally absorbed within the surrounding tissue and produce bremsstrahlung with a maximum intensity at about 110 keV. After application of 6 mCi 90Y the dose rate of the bremsstrahlung was measured at a distance of 10 cm over 13 knees in a total of 10 patients and was found to range between 0.6 and 1.3 mR/h. During a period of 3 hours up to 3 days after injection practically no removal of the material from the joint was observed. According to approximative calculations the mean dose absorbed in the knee ranged between 3650 and 7300 rad, and the absorbed dose in the synovium between 5500 and 11000 rad.
Subject(s)
Synovial Membrane/radiation effects , Synovitis/radiotherapy , Yttrium Radioisotopes/therapeutic use , Body Burden , Colloids , Humans , Knee Joint , Radiation Dosage , Silicon DioxideABSTRACT
Crystalline trypsin was irradiated in oxygen-free suspension media of methanol, ethanol and n-heptane with 60Co-gamma-rays at 77 K or 273 K. Measurements with ESR and activity determinations revealed no influence of ethanol and n-heptane on the formation of free radicals and inactivation of trypsin. Especially, the results are independent on the polarity of the suspension media and correspond to an irradiation of trypsin in vacuum. On the other hand, methanol leads to a decay of radiation induced radicals and to an increased inactivation. The results are discussed in comparison to analogous experiments carried out with ultra-violet light.
Subject(s)
Trypsin/radiation effects , Alkanes , Cobalt Radioisotopes , Dose-Response Relationship, Radiation , Electron Spin Resonance Spectroscopy , Ethanol , Free Radicals , Gamma Rays , MethanolABSTRACT
The suitability of a simple method of measuring the rate of gastric emptying of solids using 99mTc-marked filter paper pieces has been evaluated. In five healthy volunteers emptying of the filter paper pieces and of 198Au-tagged liver was measured simultaneously. In every proband the filter pieces left the stomach at a faster rate than the liver, but showed a linear emptying pattern in each experiment. Based on these observations and on recent results of other authors, a new concept of the gastric emptying of solids is presented. Within the framework of this model the use of the filter pieces in clinical studies to simulate a solid meal appears to be justified.
Subject(s)
Stomach/physiology , Gastrointestinal Motility , Gold Radioisotopes , Humans , Liver , Methods , Paper , Radionuclide Imaging , TechnetiumABSTRACT
Radiation dose to the lens of the eye was estimated using thermoluminescence and film dosimetry on patients undergoing computerised axial skull tomography with the EMI scanner, and also on various phantoms. The dose decreases from the lateral margin of the right eye to the lateral margin of the left eye. During conventional three layer tomography, maximal exposure to the eye is about 0.6 R (1.55 X 10 10-4 C.kg-1), produced entirely by scatter. Direct irradiation of the plane of orbits produces maximal exposure rate of 3 R (7.7X 10-4 C.kg-1). Maximal dose to the head depends on skull size and is about 4 R (approximately 10-3 C.kg-1). The local dose dependence of the eyes was confirmed theoretically by drawing up a computer programme, and was related to the method used by the EMI scanner.
Subject(s)
Lens, Crystalline , Radiation Dosage , Radionuclide Imaging , Film Dosimetry , Head , Humans , Manikins , Thermoluminescent Dosimetry , TomographyABSTRACT
A combination of two different modifications indicated in the literature about the ferrosulfate dosimetry has been given. This permits a dose measurement which shows compared to the usual dosimetry of Fricke above all following advantages: dose specification related to water; displacement of the absorption maximum in the perceptible spectral sphere; increase of the sensibility and lower influence of pollutions. The molar coefficient of extinction of the modified solution has been determined from Co-60-gamma irradiation and is epsilonm = 1,46 - 10(4) L - Mol(-1) - cm(-1). The increase of extinction which has been measured with this method after the irradiation with 18 MeV electrons occurs linearly within the studied region to 1200 rd at least, the G-value is 15,5. The indicated method renders possible a relative simple calibration of the ionisation chambers which have been used in the practice.
