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Modification of a Three-Dimensional Treatment Planning System for the Use of Multi-Leaf Collimators in Conformation Radiotherapy
88
Medical Dosimetry
average weight was reduced by 3 kilos and the performance status decreased by 20%. Compared to pretreatment, the patients evaluated their physical condition to be reduced during treatment and at the first follow-up visit. At 1 year post treatment the patients had regained their physical fitness. This study demonstrates that infra-diaphragmatic radiotherapy leads to significant but reversible acute/subacute side effects lasting for an average of 9 weeks.
PRECISIONRADIATIONTHERAPY FOR OPTIC NERVE
SHEATHMENINGIOMAS Tony Y. Eng, M.D., N. W. Albright, Ph.D., G. Kuwahara, R.T.T., C. N. Akazawa, R.T.T., D. Dea, R.T.T., G. L. Chu, Ph.D., W. R. Hoyt, M.D., W. M. Wara, M.D., and D. A. Larson, M.D., Ph.D. University of California, School of Medicine, San Francisco, CA International Journal of Radiation Oncology, Biology, and Physics, Vol. 22, No. 5, 1992, pp. 1093-1098 This article presents a more precise radiation therapy technique for treatment of unilateral optic nerve sheath meningioma. An immobilization device is used to align the ipsilatera1 optic nerve with a vertical axis and three small halfbeam blocked fields. The new technique irradiates a smaller volume of tissue to high dose levels, but reduces the dose to the optic chiasm and the contralateral optic nerve.
RADIOTHERAPYFOR PLEOMORPHICADENOMAOF THE PAROTIDGLAND J. Barton, FRCR, N.J. Slevin, FRCR, and E.N. Gleave, FRCS Christie Hospital, Manchaster M209Bx, U.K. International Journal of Radiation Oncology, Biology, and Physics, Vol. 22, No. 5, 1992, pp. 925-928 Plemorphic adenoma of the parotid gland is a benign tumor occurring from childhood to old age; it has a malignant potential. It is more common in women. A study was made of 187 patients who were treated with radiotherapy after surgery but with incomplete removal or spillage. Among 115 patients who received radiotherapy immediately after their surgery there was a recurrence rate of 0.9%. Seventytwo patients had therapy delayed until one or more recurrences had been surgically removed. Recurrences after radiotherapy continued beyond 20 years of followup. Patients having unsatisfactory surgery due to spill at operation or residual tumor left behind should have radiotherapy immediately, due to the increased morbidity and the higher incidence of yet further recurrence.
RE-TREATMENTOF NASOPHARYNGEAL CARCINOMA IN 53 PATIENTS Rodger M. Pryzant, M.D., Charles D. Wendt, M.D., Luis Delclos, M.D., and Lester J. Peters, M.D.
Volume 18,Number 2, 1993 Department of Radiotherapy, The University of Texas, M. D. Anderson Cancer Center, 15 15 Holcombe Blvd., Houston, TX 77030 International Journal of Radiation Oncology, Biology, and Physics, Vol. 22, No. 5, 1992, pp. 941-947 From 1954 to 1989, M. D. Anderson Cancer Center retreated, with megavoltage radiation, 53 patients with local recurrent or persistent nasopharyngeal carcinoma. The time of initial treatment to retreatment was an average of 33 months. Retreatment doses ranged from 27.5 Gy to 99 Gy and total cumulative dose range from 80 Gy to 160 Gy. Eight patients developed severe complications from retreatment, of which five were fatal. The severe complications were related to the total cumulative dose of external beam irradiation. In 1977, a combination of external beam therapy (20 Gy to 30 Gy) and intracavitary cesuim (40 Gy to 50 Gy surface dose) was used in nine selected cases. Seven of these cases achieved local control with a follow up of 7 to 102 months, and none sustained severe complications.
POTENTIALIMPROVEMENTOF THREE DIMENSION TREATMENTPLANNINGAND PROTONTHERAPY IN THE OUTCOMEOF MAXILLARYSINUS CANCER Raymond Miralbell, M.D., Candace Crowell, M.S. and Herman D. Suit, M.D., D. Phil. Department of Radiation Medicine, Massachusetts General Hospital and Harvard Cyclotron Laboratory, Harvard University, Boston, MA 02 114 International Journal of Radiation Oncology, Biology, and Physics, Vol. 22, No. 2, 1992, pp. 305-310 This study shows that an improvement in the dose distributions for carcinomas of the maxillary sinus can be achieved with the use of three dimensional treatment planning and a combination of x-ray and proton beam arrangements. Even though the tumor coverage was identical when comparing dose distributions of X-rays alone to X-rays plus proton beam boost, the critical structures (eyes, optic nerve, optic chiasm, and brain stem) received lower doses in the X-rays plus proton beam dose distribution. There should be an improved local control and reduced morbidity.
LOUISE FARRADAY MODIFICATIONOF A THREE-DIMENSIONALTREATMENT PLANNINGSYSTEMFOR THE USE OF MULTI-LEAF CoLr_rMATons IN CONFOR~WTIONRADIOTHERAPY R. Boesecke, G. Becker, K. Alandt, 0. Pastyr, J. Doll, W. Schlegel, and W. J. Lorenz Deutsches Krebsforschungezentrum, Im Neuenhelmer Feld, Heidelberg, F.R.G. Radiotherapy and Oncology Journal of the European Societyfor Therapeutic Radiology and Oncology, Vol. 21, No. 4, 1991, pp. 261-267
Literature Reviews This paper describes the development of a small, lightweight, add-on, multipurpose collimator that can be used for a variety of linear accelerators. The Heidelberg multileaf collimator has been developed at the Institute of Radiology and Pathophysiology at the German Cancer Research Centre. It consists of tungsten absorbers with double focused edges to keep penumbra to a minimum. The required thickness of the absorber depends on the photon energy. Treatment planning of conformation therapy (the intent to confine the therapeutic dose to the target volume) must be fully three-dimensional. The Heidelberg multi-leafcollimator will allow the routine use of more complicated techniques in the clinical environment. It is easy to use and can generate single irregular fields much faster than the usual methods such as foam cutting and casting blocks.
ACCURACYOFPATIENTPOSITIONING IN MANTLE FIELDIRRADIATION C. L. Creutzberg,’A. G. Visser,’P. M. Z. R. DePorre,‘**
J. H. Meerwaldt,‘~* V. G. M. Althor’,’ and P. C. Levendag Departments of ‘Radiation Oncology and *Clinical Physics, Dr. Daniel den Hood Cancer Center, Rotterdam, The Netherlands Radiation and OncologyJournal ofthe European Societyfor Therapeutic Radiology and Oncology, Vol. 23, No. 23, 1992, pp. 257-264 The use of individualized shielding blocks that ensure the adequate treatment of lymphoid tissue whilst sparing criti-
89
cal organs and tissue is an important
feature of the mantle field technique. The complex shape of the extended fields makes precision in radiotherapy setup difficult to achieve. Discrepancies in daily treatment positioning and differences between localization setupand treatmentsetupcould result in either in an underdosage in the field margins or an overdosage to normal tissues. This paper monitors the accuracy of the treatment setup and block positioning in 13 patients treated with the mantle field technique.
INFLUENCE OFSHIELDING BLOCKSON THEOUTPUT OFPHOTONBEAMSASA FUNCTION OFENERGY ANDTYPE OF TREATMENTUNIT
J. Van Darn,,, A. Bridier,b C. Lasselin, N. Blanckaert” and A. Dutreixa “U.Z. St. Rafael, Leuven, Belgium, and bInstitut Gustave Roussy, Villejuif, France Radiotherapy and Oncology Journal of the European Society for Therapeutic Radiology and Oncology, Vol. 24, No. 1, 1992, pp. 55-59 One G. E. Cobalt unit, four GE-CGR Linacs, two Siemens and one Philips linac have been used in a study to determine the influence of field-defining shielding blocks. The loss in output due to these shielding blocks has been calculated taking into account loss in phantom scatter only. Results showed that in higher energies, in fields in which blocks are close to the central beam axis, an overestimation of the output by the algorithm was found.
Medical Dosimetry
average weight was reduced by 3 kilos and the performance status decreased by 20%. Compared to pretreatment, the patients evaluated their physical condition to be reduced during treatment and at the first follow-up visit. At 1 year post treatment the patients had regained their physical fitness. This study demonstrates that infra-diaphragmatic radiotherapy leads to significant but reversible acute/subacute side effects lasting for an average of 9 weeks.
PRECISIONRADIATIONTHERAPY FOR OPTIC NERVE
SHEATHMENINGIOMAS Tony Y. Eng, M.D., N. W. Albright, Ph.D., G. Kuwahara, R.T.T., C. N. Akazawa, R.T.T., D. Dea, R.T.T., G. L. Chu, Ph.D., W. R. Hoyt, M.D., W. M. Wara, M.D., and D. A. Larson, M.D., Ph.D. University of California, School of Medicine, San Francisco, CA International Journal of Radiation Oncology, Biology, and Physics, Vol. 22, No. 5, 1992, pp. 1093-1098 This article presents a more precise radiation therapy technique for treatment of unilateral optic nerve sheath meningioma. An immobilization device is used to align the ipsilatera1 optic nerve with a vertical axis and three small halfbeam blocked fields. The new technique irradiates a smaller volume of tissue to high dose levels, but reduces the dose to the optic chiasm and the contralateral optic nerve.
RADIOTHERAPYFOR PLEOMORPHICADENOMAOF THE PAROTIDGLAND J. Barton, FRCR, N.J. Slevin, FRCR, and E.N. Gleave, FRCS Christie Hospital, Manchaster M209Bx, U.K. International Journal of Radiation Oncology, Biology, and Physics, Vol. 22, No. 5, 1992, pp. 925-928 Plemorphic adenoma of the parotid gland is a benign tumor occurring from childhood to old age; it has a malignant potential. It is more common in women. A study was made of 187 patients who were treated with radiotherapy after surgery but with incomplete removal or spillage. Among 115 patients who received radiotherapy immediately after their surgery there was a recurrence rate of 0.9%. Seventytwo patients had therapy delayed until one or more recurrences had been surgically removed. Recurrences after radiotherapy continued beyond 20 years of followup. Patients having unsatisfactory surgery due to spill at operation or residual tumor left behind should have radiotherapy immediately, due to the increased morbidity and the higher incidence of yet further recurrence.
RE-TREATMENTOF NASOPHARYNGEAL CARCINOMA IN 53 PATIENTS Rodger M. Pryzant, M.D., Charles D. Wendt, M.D., Luis Delclos, M.D., and Lester J. Peters, M.D.
Volume 18,Number 2, 1993 Department of Radiotherapy, The University of Texas, M. D. Anderson Cancer Center, 15 15 Holcombe Blvd., Houston, TX 77030 International Journal of Radiation Oncology, Biology, and Physics, Vol. 22, No. 5, 1992, pp. 941-947 From 1954 to 1989, M. D. Anderson Cancer Center retreated, with megavoltage radiation, 53 patients with local recurrent or persistent nasopharyngeal carcinoma. The time of initial treatment to retreatment was an average of 33 months. Retreatment doses ranged from 27.5 Gy to 99 Gy and total cumulative dose range from 80 Gy to 160 Gy. Eight patients developed severe complications from retreatment, of which five were fatal. The severe complications were related to the total cumulative dose of external beam irradiation. In 1977, a combination of external beam therapy (20 Gy to 30 Gy) and intracavitary cesuim (40 Gy to 50 Gy surface dose) was used in nine selected cases. Seven of these cases achieved local control with a follow up of 7 to 102 months, and none sustained severe complications.
POTENTIALIMPROVEMENTOF THREE DIMENSION TREATMENTPLANNINGAND PROTONTHERAPY IN THE OUTCOMEOF MAXILLARYSINUS CANCER Raymond Miralbell, M.D., Candace Crowell, M.S. and Herman D. Suit, M.D., D. Phil. Department of Radiation Medicine, Massachusetts General Hospital and Harvard Cyclotron Laboratory, Harvard University, Boston, MA 02 114 International Journal of Radiation Oncology, Biology, and Physics, Vol. 22, No. 2, 1992, pp. 305-310 This study shows that an improvement in the dose distributions for carcinomas of the maxillary sinus can be achieved with the use of three dimensional treatment planning and a combination of x-ray and proton beam arrangements. Even though the tumor coverage was identical when comparing dose distributions of X-rays alone to X-rays plus proton beam boost, the critical structures (eyes, optic nerve, optic chiasm, and brain stem) received lower doses in the X-rays plus proton beam dose distribution. There should be an improved local control and reduced morbidity.
LOUISE FARRADAY MODIFICATIONOF A THREE-DIMENSIONALTREATMENT PLANNINGSYSTEMFOR THE USE OF MULTI-LEAF CoLr_rMATons IN CONFOR~WTIONRADIOTHERAPY R. Boesecke, G. Becker, K. Alandt, 0. Pastyr, J. Doll, W. Schlegel, and W. J. Lorenz Deutsches Krebsforschungezentrum, Im Neuenhelmer Feld, Heidelberg, F.R.G. Radiotherapy and Oncology Journal of the European Societyfor Therapeutic Radiology and Oncology, Vol. 21, No. 4, 1991, pp. 261-267
Literature Reviews This paper describes the development of a small, lightweight, add-on, multipurpose collimator that can be used for a variety of linear accelerators. The Heidelberg multileaf collimator has been developed at the Institute of Radiology and Pathophysiology at the German Cancer Research Centre. It consists of tungsten absorbers with double focused edges to keep penumbra to a minimum. The required thickness of the absorber depends on the photon energy. Treatment planning of conformation therapy (the intent to confine the therapeutic dose to the target volume) must be fully three-dimensional. The Heidelberg multi-leafcollimator will allow the routine use of more complicated techniques in the clinical environment. It is easy to use and can generate single irregular fields much faster than the usual methods such as foam cutting and casting blocks.
ACCURACYOFPATIENTPOSITIONING IN MANTLE FIELDIRRADIATION C. L. Creutzberg,’A. G. Visser,’P. M. Z. R. DePorre,‘**
J. H. Meerwaldt,‘~* V. G. M. Althor’,’ and P. C. Levendag Departments of ‘Radiation Oncology and *Clinical Physics, Dr. Daniel den Hood Cancer Center, Rotterdam, The Netherlands Radiation and OncologyJournal ofthe European Societyfor Therapeutic Radiology and Oncology, Vol. 23, No. 23, 1992, pp. 257-264 The use of individualized shielding blocks that ensure the adequate treatment of lymphoid tissue whilst sparing criti-
89
cal organs and tissue is an important
feature of the mantle field technique. The complex shape of the extended fields makes precision in radiotherapy setup difficult to achieve. Discrepancies in daily treatment positioning and differences between localization setupand treatmentsetupcould result in either in an underdosage in the field margins or an overdosage to normal tissues. This paper monitors the accuracy of the treatment setup and block positioning in 13 patients treated with the mantle field technique.
INFLUENCE OFSHIELDING BLOCKSON THEOUTPUT OFPHOTONBEAMSASA FUNCTION OFENERGY ANDTYPE OF TREATMENTUNIT
J. Van Darn,,, A. Bridier,b C. Lasselin, N. Blanckaert” and A. Dutreixa “U.Z. St. Rafael, Leuven, Belgium, and bInstitut Gustave Roussy, Villejuif, France Radiotherapy and Oncology Journal of the European Society for Therapeutic Radiology and Oncology, Vol. 24, No. 1, 1992, pp. 55-59 One G. E. Cobalt unit, four GE-CGR Linacs, two Siemens and one Philips linac have been used in a study to determine the influence of field-defining shielding blocks. The loss in output due to these shielding blocks has been calculated taking into account loss in phantom scatter only. Results showed that in higher energies, in fields in which blocks are close to the central beam axis, an overestimation of the output by the algorithm was found.