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The effects of shielding damage of Ir192 wires in aesthetical failures of implanted skin cancers
1376
Radiation
Oncology
0
Biology
0
Physics
October
1980, Volume
6, Number
10
data; 2) measured phantom densities of 0.11, 0.41, 0.56. 0.66, 0.72. and 1.0 g/cm3; and 3) computer optimization to determine rads per degree to accomPatient contours and internal structure plish uniform dose distribution. information are obtained by using the treatment machine range finder, compuCT is used to determine lung density and terized tomography and ultrasound. to illustrate areas where su erficial bolus is needed to compensate for lack of tissue thickness. By utl.P. lzing least squares fitting, the relationship between Varian CT numbers and experimentally measured densities (range 0.11 to 1.0 g/cm3) was determined. axis
A Rando phantom and a polystyrene phantom using multiple "lung phantom" Seven inserts with densities from 0.11 to 0.72 g/cm3 have been irradiated. patients with breast cancer have been treated with electron beam moving arc therapy. Seven were treated after radical surgery proved that they were at Two patients initially treated high risk for local and regional recurrences. Decreased mobility of the shoulder with surgery received this therapy solely, No major complications have excluded one patient from this treatment mode. Patient setup techniques and comparison of dose uniformity occurred to date. and lung dose for arc technique versus standard chest wall technique will be presented, as well as follow-up on these patients. This project supported Cancer Society.
(59)
in part by a grant from the Utah Division American
192 WIRES THE EFFECTS OF SHIELDING DAMAGE OF Ir IN AESTHETICAL FAILURES OF IMPLANTED SKIN CANCERS J. Bello and C. Oyarzun' F. Abrath and J. Purdy2 1
Chilean Nuclear Enerqy Comission P. 0. Box 188b Santiago, Chile
2 Mallinckrodt Institute of Radiology Washington University School of Medicine Physics Section 510 S. Kingshighway St. Louis, Missouri 63110 Thirty seven patients with basal-cell carcinoma (78%) and squamous-cell carinoma (28%) of the skin were treated with iridium-192 wires. The implants were performed according to the Paris System convention and the doses were calculated from a computer program allowing for greater accuracy than reading the "escargot" curves. Aesthetical results have been good in 86% of the patients. However, the aesthetical failures are of particular concern for skin cancer patients and especially for facial cancers. The dosimetry of all the patients was reviewed and found to be comparable indicating the failures were not a function of the implant system or the dosimetry. It was found that the aesthetical failures had been treated with iridium-192 wires which had previously been used more than 2 or 3 times in other patients. An attempt was made to study the physical properties of the iridium wire in an effort to correlate these properties to the regions of high dose observed in the patients with poor aesthetical results. Non active iridium wire provided by an American and a European company and were studied to determine their structure, physical composition and the effect of clinical handling on the platinum shielding. An x-ray microanalyzer was used to perform a quantitative analyses of the shielding and core. An agreement within 5% of the manufacturers specifications were found for the core and 1": for the shielding. Pictures were taken of the secondary electronic images observed with a
Proceedings of the 22nd Annual ASTR Meeting SEM. Multiple pores 2 2 rrn were observed in the shielding of the wire provided by one supplier. The effects of the shielding when the wire is handled with tweezers, cut, inserted inside a plastic ribbon were thoroughly studied. A partial loss of the shielding zone (pure Pt) was observed (2/3 of it in some cases) when the A loss of the shielding allows for a higher degree of the wire was handled. This was verified. emission of beta radiation. The unesthetic results could be explained by the beta radiation emitted The clinical effects of this damaged shielding through the damaged shielding. is discussed and advice is given on the care needed to handle and cut the iridium at the clinic.
A METHOD OF PRODUCING A HOMOGENEOUS RADIATION FIELD AN EDGE MATCHING COMPENSATOR OF "INFINITE" LENGTH. FOR ABUTTING FIELDS TO SIMPLIFY WHOLE AND HEMIBODY RADIATION THERAPY Berry Stewart, M.S. Fred Abrath. Ph.D. Bruce J. Walz. M.D. Division of Radiation Oncology Mallinckrodt Institute of Radiology Washington University School of Medicine St. Louis. Missouri 63110 Whole and hemibody radiation therapy requires very large fields, often unattainable nn backstop-limited radiation therapy machines. We have designed a tapered compensator to be placed along the edge of a radiation therapy beam to facilitate applying large homogeneous radiation fields without a "gap". A brass compensator is introduced at the edges of the abutting radiation beams and attenuates the primary S-J beams may be jnined at their optical edges on the surface of the patient. Parallel A family of compensators opposed technique is required for homogeneity. is needed for areas of differing thickness. The overlap reqion of abutting beams was measured with a "wide open" 31 cm field on a Clinac 6X. A 70: "hot spot" about 3 cm wide resulted at a depth of 10 cm. A stepped brass filter or compensator was designed to subtract radiation from both beam edqes. With the compensators in place, the overlap area is homogeneous within lo-15%, depending on depth. A comparable non-moving gap technique results in "hot" or "cold" spots of up to 50?,, depending on depth. By directly abutting beam after beam, this technique permits assembling essentially a field of infinite length without major homogeneities. This paper presents the method of compensator design and the dosimetric results of single and double edge compensated beams. including parallel-opposed technique, Though designed for a 6 MeV linac, the method is widely applicable. A simplified method of achieving homogeneous whole and hemibody radiation with multiple fields will be described in detail. This technique should simplify whole and hemibody radiation therapy to make it more widely available.
Radiation
Oncology
0
Biology
0
Physics
October
1980, Volume
6, Number
10
data; 2) measured phantom densities of 0.11, 0.41, 0.56. 0.66, 0.72. and 1.0 g/cm3; and 3) computer optimization to determine rads per degree to accomPatient contours and internal structure plish uniform dose distribution. information are obtained by using the treatment machine range finder, compuCT is used to determine lung density and terized tomography and ultrasound. to illustrate areas where su erficial bolus is needed to compensate for lack of tissue thickness. By utl.P. lzing least squares fitting, the relationship between Varian CT numbers and experimentally measured densities (range 0.11 to 1.0 g/cm3) was determined. axis
A Rando phantom and a polystyrene phantom using multiple "lung phantom" Seven inserts with densities from 0.11 to 0.72 g/cm3 have been irradiated. patients with breast cancer have been treated with electron beam moving arc therapy. Seven were treated after radical surgery proved that they were at Two patients initially treated high risk for local and regional recurrences. Decreased mobility of the shoulder with surgery received this therapy solely, No major complications have excluded one patient from this treatment mode. Patient setup techniques and comparison of dose uniformity occurred to date. and lung dose for arc technique versus standard chest wall technique will be presented, as well as follow-up on these patients. This project supported Cancer Society.
(59)
in part by a grant from the Utah Division American
192 WIRES THE EFFECTS OF SHIELDING DAMAGE OF Ir IN AESTHETICAL FAILURES OF IMPLANTED SKIN CANCERS J. Bello and C. Oyarzun' F. Abrath and J. Purdy2 1
Chilean Nuclear Enerqy Comission P. 0. Box 188b Santiago, Chile
2 Mallinckrodt Institute of Radiology Washington University School of Medicine Physics Section 510 S. Kingshighway St. Louis, Missouri 63110 Thirty seven patients with basal-cell carcinoma (78%) and squamous-cell carinoma (28%) of the skin were treated with iridium-192 wires. The implants were performed according to the Paris System convention and the doses were calculated from a computer program allowing for greater accuracy than reading the "escargot" curves. Aesthetical results have been good in 86% of the patients. However, the aesthetical failures are of particular concern for skin cancer patients and especially for facial cancers. The dosimetry of all the patients was reviewed and found to be comparable indicating the failures were not a function of the implant system or the dosimetry. It was found that the aesthetical failures had been treated with iridium-192 wires which had previously been used more than 2 or 3 times in other patients. An attempt was made to study the physical properties of the iridium wire in an effort to correlate these properties to the regions of high dose observed in the patients with poor aesthetical results. Non active iridium wire provided by an American and a European company and were studied to determine their structure, physical composition and the effect of clinical handling on the platinum shielding. An x-ray microanalyzer was used to perform a quantitative analyses of the shielding and core. An agreement within 5% of the manufacturers specifications were found for the core and 1": for the shielding. Pictures were taken of the secondary electronic images observed with a
Proceedings of the 22nd Annual ASTR Meeting SEM. Multiple pores 2 2 rrn were observed in the shielding of the wire provided by one supplier. The effects of the shielding when the wire is handled with tweezers, cut, inserted inside a plastic ribbon were thoroughly studied. A partial loss of the shielding zone (pure Pt) was observed (2/3 of it in some cases) when the A loss of the shielding allows for a higher degree of the wire was handled. This was verified. emission of beta radiation. The unesthetic results could be explained by the beta radiation emitted The clinical effects of this damaged shielding through the damaged shielding. is discussed and advice is given on the care needed to handle and cut the iridium at the clinic.
A METHOD OF PRODUCING A HOMOGENEOUS RADIATION FIELD AN EDGE MATCHING COMPENSATOR OF "INFINITE" LENGTH. FOR ABUTTING FIELDS TO SIMPLIFY WHOLE AND HEMIBODY RADIATION THERAPY Berry Stewart, M.S. Fred Abrath. Ph.D. Bruce J. Walz. M.D. Division of Radiation Oncology Mallinckrodt Institute of Radiology Washington University School of Medicine St. Louis. Missouri 63110 Whole and hemibody radiation therapy requires very large fields, often unattainable nn backstop-limited radiation therapy machines. We have designed a tapered compensator to be placed along the edge of a radiation therapy beam to facilitate applying large homogeneous radiation fields without a "gap". A brass compensator is introduced at the edges of the abutting radiation beams and attenuates the primary S-J beams may be jnined at their optical edges on the surface of the patient. Parallel A family of compensators opposed technique is required for homogeneity. is needed for areas of differing thickness. The overlap reqion of abutting beams was measured with a "wide open" 31 cm field on a Clinac 6X. A 70: "hot spot" about 3 cm wide resulted at a depth of 10 cm. A stepped brass filter or compensator was designed to subtract radiation from both beam edqes. With the compensators in place, the overlap area is homogeneous within lo-15%, depending on depth. A comparable non-moving gap technique results in "hot" or "cold" spots of up to 50?,, depending on depth. By directly abutting beam after beam, this technique permits assembling essentially a field of infinite length without major homogeneities. This paper presents the method of compensator design and the dosimetric results of single and double edge compensated beams. including parallel-opposed technique, Though designed for a 6 MeV linac, the method is widely applicable. A simplified method of achieving homogeneous whole and hemibody radiation with multiple fields will be described in detail. This technique should simplify whole and hemibody radiation therapy to make it more widely available.