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Important Prognostic Factors Influencing Outcome of Combined Radiation and Hyperthermia
Literature Reviews
when the currents in the magnets which form the electron beam transport system were changed. The modulation transfer functions of the linear accelerators were also studied. It was found that the MTFs were similar for the 6-MV and 1%MV accelerators. The deduction was made that the differences in the quality of images seen clinically between the 6-MV and IS-MV beams were not due to resolution changes caused by the x-ray sources or detectors since the MTFs were the same for both beams.
61
LEAKAGERADIATIONFROM ELECTRONAPPLICATORS ON A MEDICALACCELERATOR Edward C. Pennington, Shirish K. Jani, and B-Chen Wen
Division of Radiation Oncology, Department of Radiology, The University
of Iowa Hospitals and Clinics
Med. Phys., Vol. 15, No. 5, Sep/Oct 1988, pp. 763-765
VIRTUALSOURCEDISTANCESFOR ELECTRON BEAMS BETWEEN5 AND 20 MEV
S. J. Thomas Medical Physics Department, Addenbrooke’s Cambridge CB2 2QQ, UK
Hospital,
Phys. Med. Biol., Vol. 33, No. 11, 1988, pp. 1325-l 328 The virtual source-to-skin distances of a modem linear accelerator, a Brown-Boveri CH 16, were presented. This linac employs a double scattering foil and collimates the beam above the applicator with the X-ray jaws to reduce the scatter from the applicator walls. This scatter reduction from the applicator walls should produce less variation in the virtual source position with energy and field size. Also the pre-collimation of the beam in the CH 16 allows the applicators to be much lighter because they are made of fiberglass and aluminum. The virtual source-to-skin distances were measured according to Almond’s (1976) method on applicator sizes from 6 X 6 cm to 25 X 25 cm between 5 and 20 MeV energies. Measurements were made at several distances from the applicator with an ionization chamber in air. A graph of the reciprocal of the square root of the ion chamber readings versus distances from the applicator produces a straight line. This line intersects the distance axis at the virtual source position. The results observed indicated that the virtual source position varies greatly with field size and energy even with the improvements in linear accelerator designs. This necessitates that virtual source position measurements be made over a full range of energies and applicators that are available to insure accurate dosimetry for electron therapy.
AN EXPLANATIONOF THE DOSE INHOM~GENEITY CAUSEDBY Bonus IN AN ELXTRON PORTAL Lloyd W. Asp
Med. Phys., Vol. 15, No. 6, Nov/Dec
A Varian Clinac 2500 linear accelerator was checked for radiation leakage from the electron cone assembly. Applicators ranging from 6 cm x 6 cm to 25 cm X 25 cm were measured for each energy from 6 to 22 MeV. The location of the leakage radiation was found along the sides of the applicator by attaching ready pack X-ray film to the cone and turning on the beam. The processed film highlighted the areas of significant leakage. All of the cones showed the same general location for surface leakage of radiation. The maximum surface dose leakage was 39% for a 6 cm X 6 cm cone with I2 MeV electrons. Possibilities for alleviating this problem were investigated. Lining the inside surface of the 6 cm X 6 cm cone with 1 mm of lead reduced the leakage by a factor of four. The option of reducing the collimator setting was beneficial in only some instances as it also effected beam flatness and symmetry. Institutions were encouraged to identify this problem and take steps to reduce excessive electron leakage.
MARCIA
PRICE
IMIPORTANT PROGNOSTIC FACTORS INFLUENCING OUTC~MEOF COMBINED RADIATION AND HYPERTHERMIA Riccardo VaIdagni, M.D., Fei-Fei Lui, M.D., F.R.C.P.(C), and Daniel S. Kapp, Ph.D., M.D.
Department of Therapeutic Radiology, Stanford University Medical Center, Stanford, California 94305 Int. J. of Radiation Oncology, Biology, Physics, Vol. 15, Oct. 1988, pp. 959-972 This article discussed several factors which will influence the final outcome of the patients that are treated with combined local regional hyperthermia and radiation therapy. The pretreatment factors include: tumor dimension, tumor histology, and tumor site. The actual treatment factors wliich should be considered are the radiation therapy dose and the hyperthermia parameters. An evaluation of response and complications are also discussed.
1988, pp. 922-923
This is a technical note describing an electron beam isodose distribution that occurs when a bolus with a square edge is placed in the portal. The explanation utilizes figures depicting a single electron dose distribution incident on a flat surface which appears to have a step created by the bolus. The resulting isodose distributions showing a blurry penumbra due to the bolused portion in comparison to the unbolused portion are presented.
INTRACAVITARY IRRADIATION OF CARCINOMAS OF THE UTERUSAND CERVIX: THE CR~TEILMETHOD Bernard Pierquin, M.D., Ginette Marinello, Ph.D., Jean Pierre Mege, Ph.D., and Juanita Crook, M.D.
fipartement de Canc&ologie du C.H.U. Henri Mondor, 5 1 Avenue De Lattre de Tassigny, Cr&eil, France 940 10
when the currents in the magnets which form the electron beam transport system were changed. The modulation transfer functions of the linear accelerators were also studied. It was found that the MTFs were similar for the 6-MV and 1%MV accelerators. The deduction was made that the differences in the quality of images seen clinically between the 6-MV and IS-MV beams were not due to resolution changes caused by the x-ray sources or detectors since the MTFs were the same for both beams.
61
LEAKAGERADIATIONFROM ELECTRONAPPLICATORS ON A MEDICALACCELERATOR Edward C. Pennington, Shirish K. Jani, and B-Chen Wen
Division of Radiation Oncology, Department of Radiology, The University
of Iowa Hospitals and Clinics
Med. Phys., Vol. 15, No. 5, Sep/Oct 1988, pp. 763-765
VIRTUALSOURCEDISTANCESFOR ELECTRON BEAMS BETWEEN5 AND 20 MEV
S. J. Thomas Medical Physics Department, Addenbrooke’s Cambridge CB2 2QQ, UK
Hospital,
Phys. Med. Biol., Vol. 33, No. 11, 1988, pp. 1325-l 328 The virtual source-to-skin distances of a modem linear accelerator, a Brown-Boveri CH 16, were presented. This linac employs a double scattering foil and collimates the beam above the applicator with the X-ray jaws to reduce the scatter from the applicator walls. This scatter reduction from the applicator walls should produce less variation in the virtual source position with energy and field size. Also the pre-collimation of the beam in the CH 16 allows the applicators to be much lighter because they are made of fiberglass and aluminum. The virtual source-to-skin distances were measured according to Almond’s (1976) method on applicator sizes from 6 X 6 cm to 25 X 25 cm between 5 and 20 MeV energies. Measurements were made at several distances from the applicator with an ionization chamber in air. A graph of the reciprocal of the square root of the ion chamber readings versus distances from the applicator produces a straight line. This line intersects the distance axis at the virtual source position. The results observed indicated that the virtual source position varies greatly with field size and energy even with the improvements in linear accelerator designs. This necessitates that virtual source position measurements be made over a full range of energies and applicators that are available to insure accurate dosimetry for electron therapy.
AN EXPLANATIONOF THE DOSE INHOM~GENEITY CAUSEDBY Bonus IN AN ELXTRON PORTAL Lloyd W. Asp
Med. Phys., Vol. 15, No. 6, Nov/Dec
A Varian Clinac 2500 linear accelerator was checked for radiation leakage from the electron cone assembly. Applicators ranging from 6 cm x 6 cm to 25 cm X 25 cm were measured for each energy from 6 to 22 MeV. The location of the leakage radiation was found along the sides of the applicator by attaching ready pack X-ray film to the cone and turning on the beam. The processed film highlighted the areas of significant leakage. All of the cones showed the same general location for surface leakage of radiation. The maximum surface dose leakage was 39% for a 6 cm X 6 cm cone with I2 MeV electrons. Possibilities for alleviating this problem were investigated. Lining the inside surface of the 6 cm X 6 cm cone with 1 mm of lead reduced the leakage by a factor of four. The option of reducing the collimator setting was beneficial in only some instances as it also effected beam flatness and symmetry. Institutions were encouraged to identify this problem and take steps to reduce excessive electron leakage.
MARCIA
PRICE
IMIPORTANT PROGNOSTIC FACTORS INFLUENCING OUTC~MEOF COMBINED RADIATION AND HYPERTHERMIA Riccardo VaIdagni, M.D., Fei-Fei Lui, M.D., F.R.C.P.(C), and Daniel S. Kapp, Ph.D., M.D.
Department of Therapeutic Radiology, Stanford University Medical Center, Stanford, California 94305 Int. J. of Radiation Oncology, Biology, Physics, Vol. 15, Oct. 1988, pp. 959-972 This article discussed several factors which will influence the final outcome of the patients that are treated with combined local regional hyperthermia and radiation therapy. The pretreatment factors include: tumor dimension, tumor histology, and tumor site. The actual treatment factors wliich should be considered are the radiation therapy dose and the hyperthermia parameters. An evaluation of response and complications are also discussed.
1988, pp. 922-923
This is a technical note describing an electron beam isodose distribution that occurs when a bolus with a square edge is placed in the portal. The explanation utilizes figures depicting a single electron dose distribution incident on a flat surface which appears to have a step created by the bolus. The resulting isodose distributions showing a blurry penumbra due to the bolused portion in comparison to the unbolused portion are presented.
INTRACAVITARY IRRADIATION OF CARCINOMAS OF THE UTERUSAND CERVIX: THE CR~TEILMETHOD Bernard Pierquin, M.D., Ginette Marinello, Ph.D., Jean Pierre Mege, Ph.D., and Juanita Crook, M.D.
fipartement de Canc&ologie du C.H.U. Henri Mondor, 5 1 Avenue De Lattre de Tassigny, Cr&eil, France 940 10