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CT simulator: A new 3-D planning and simulating system for radiotherapy: Part 2. clinical application
240
Medical Dosimetry
couch/x-ray controls, the CT operator console, the multiimage display console, the treatment planning console with a CT image processor, and the laser beam projecting device. With the patient scanned in the treatment position, the treatment planning is done on multiple slices. Treatment fields are designed to fit the target volume on all slices to give an optimal dose distribution. The information is relayed to the laser beam projecting system, which projects the beam center and shape onto the patient’s skin. A patient can be scanned, planned, and simulated according to the plan in 30 to 40 minutes.
Volume 15, Number 4, 1990 on a microcomputer (Macintosh II) is presented that accounts for isotope decay, source anisotrophy, inhomogeneous scatter, and collimation provided by the lip of the plaque. The program can be used to optimize the plaque design and seed placement. Advantages and disadvantaged are given.
MIKE DWORZANIN MEASUREMENTOF DOSE DISTRIBUTIONSUSING FILM IN THERAPEUTICELECTRONBEAMS
CT SIMULATOR:A NEW 3-D PLANNINGAND SIMULATING SYSTEMFOR RADIOTHERAPY:PART 2. CLINICALAPPLICATION
Almon S. Shiu, Victor A. Otte, and Kenneth R. Hogstrom
Yasushi Nagata, M.D.,’ Takehiro Nishidai, Ph.D.,’ Mitsuyuki Abe, M.D.,’ Masaji Takahashi, M.D.,’ Kaoru Okajima, M.D.,’ Nobuyuki Yamaoka, M.S.,* Hiroshi Ishihara, M.S.,* Yasufumi Kubo, M.S.,3 Hiroshi Ohta, M.S.,3 Chudo Kazuas, M.S.3
Medical Physics, Vol. 16, No. 6, Nov/Dec 1989
‘Department of Radiology, Kyoto University, Kyoto 606; *Medical System Div., Shimadzu Corporation, Kyoto 604; ‘Medical System Div., NEC Corporation, Tokyo 183, Japan International Journal of Radiation Oncology, Biology, Physics, Vol. 18, No. 3, March 1990, pp. 505-5 I3 The clinical applications of the CT simulator are discussed. It is particularly useful in cases where the target volume lies adjacent to dose limiting structures, where the target volume has a complicated shape, and where the target volume is to be treated with tangential or rotational portals. In all cases, the 3-D planning with field shaping viewed on any CT slice in the target area, and accurate transfer of this data directly to the patient’s skin allows the radiotherapist to feel comfortable that all areas are adequately and safely irradiated.
AN INTERACTIVETREATMENTPLANNING SYSTEM FOR OPHTHALMICPLAQUE RADIOTHERAPY Melvin A. Astrahan, Ph.D., Gary Luxton, Ph.D., Gabor Jozsef, Ph.D., Thomas D. Kampp, Ph.D., Peter E. Liggett, M.D., Michael D. Sapozink, M.D., Ph.D., Zbigniew Petrovich, M.D. University of Southern California School of Medicine, Los Angeles, CA International Journal of Radiation Oncology, Biology, Physics, Vol. 18, No. 3, March 1990, pp. 679-687 Removable episcleral plaques containing I- 125, Ir- 192, Co60, or Ru- 106 are viable alternatives to x-ray therapy in the treatment of ophthalmic tumors. However, the long-term complications present with their use demand extremely accurate and detailed dosimetry of the plaque to determine why the complications exist. A dosimetry program written
Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX
A large number of measured electron dose distributions are necessary before a linear accelerator can be utilized clinically. Measurements are made for many field sizes at each energy. The recommended method of measurement is an ion chamber in a water phantom, but a great deal ofaccelerator machine time is needed. The obvious advantages of film dosimetry are high resolution and short beam time. Film has become desirable for measuring isodose distributions and dose profiles when a beam scanner is unavailable or machine time is limited. This basically is because ofthe new near-tissue equivalent, solid, opaque phantom material film cassettes. A quantitative study was performed evaluating the feasibility of using film dosimetry data as the input data for patient treatment planning. A comparison was made between film measurements in a solid phantom and ionchamber measurements in a water phantom for central-axis depth dose and off-axis ratios. Isodose distributions were generated from film data alone. They were also generated from a combination of ion chamber central axis depth dose measurements and film data off axis ratios. The central axis depth dose was in agreement within 1 mm at depths greater than 10 mm. It was recommended that the central-axis depth dose be measured using ionization chambers. Film dosimetry data for the off-axis ratios were in agreement within I%, and therefore were considered to represent an acceptable, machine-time-conserving, alternative means of measurement.
AN ISO~SE SHIFT TECHNIQUEFOR OBLIQUELY INCIDENTELECTRONBEAMS Kenneth Ulin and Edward S. Stemick Medical Physics Division, Department of Radiation Oncology, Tufts-New England Medical Center, Boston, MA Medical Physics, Vol. 16, No. 6, Nov/Dec
1989
When an electron beam is obliquely incident on a flat surface, the isodose lines remain parallel to the surface and are simply shifted toward the surface. The authors have devel-
Medical Dosimetry
couch/x-ray controls, the CT operator console, the multiimage display console, the treatment planning console with a CT image processor, and the laser beam projecting device. With the patient scanned in the treatment position, the treatment planning is done on multiple slices. Treatment fields are designed to fit the target volume on all slices to give an optimal dose distribution. The information is relayed to the laser beam projecting system, which projects the beam center and shape onto the patient’s skin. A patient can be scanned, planned, and simulated according to the plan in 30 to 40 minutes.
Volume 15, Number 4, 1990 on a microcomputer (Macintosh II) is presented that accounts for isotope decay, source anisotrophy, inhomogeneous scatter, and collimation provided by the lip of the plaque. The program can be used to optimize the plaque design and seed placement. Advantages and disadvantaged are given.
MIKE DWORZANIN MEASUREMENTOF DOSE DISTRIBUTIONSUSING FILM IN THERAPEUTICELECTRONBEAMS
CT SIMULATOR:A NEW 3-D PLANNINGAND SIMULATING SYSTEMFOR RADIOTHERAPY:PART 2. CLINICALAPPLICATION
Almon S. Shiu, Victor A. Otte, and Kenneth R. Hogstrom
Yasushi Nagata, M.D.,’ Takehiro Nishidai, Ph.D.,’ Mitsuyuki Abe, M.D.,’ Masaji Takahashi, M.D.,’ Kaoru Okajima, M.D.,’ Nobuyuki Yamaoka, M.S.,* Hiroshi Ishihara, M.S.,* Yasufumi Kubo, M.S.,3 Hiroshi Ohta, M.S.,3 Chudo Kazuas, M.S.3
Medical Physics, Vol. 16, No. 6, Nov/Dec 1989
‘Department of Radiology, Kyoto University, Kyoto 606; *Medical System Div., Shimadzu Corporation, Kyoto 604; ‘Medical System Div., NEC Corporation, Tokyo 183, Japan International Journal of Radiation Oncology, Biology, Physics, Vol. 18, No. 3, March 1990, pp. 505-5 I3 The clinical applications of the CT simulator are discussed. It is particularly useful in cases where the target volume lies adjacent to dose limiting structures, where the target volume has a complicated shape, and where the target volume is to be treated with tangential or rotational portals. In all cases, the 3-D planning with field shaping viewed on any CT slice in the target area, and accurate transfer of this data directly to the patient’s skin allows the radiotherapist to feel comfortable that all areas are adequately and safely irradiated.
AN INTERACTIVETREATMENTPLANNING SYSTEM FOR OPHTHALMICPLAQUE RADIOTHERAPY Melvin A. Astrahan, Ph.D., Gary Luxton, Ph.D., Gabor Jozsef, Ph.D., Thomas D. Kampp, Ph.D., Peter E. Liggett, M.D., Michael D. Sapozink, M.D., Ph.D., Zbigniew Petrovich, M.D. University of Southern California School of Medicine, Los Angeles, CA International Journal of Radiation Oncology, Biology, Physics, Vol. 18, No. 3, March 1990, pp. 679-687 Removable episcleral plaques containing I- 125, Ir- 192, Co60, or Ru- 106 are viable alternatives to x-ray therapy in the treatment of ophthalmic tumors. However, the long-term complications present with their use demand extremely accurate and detailed dosimetry of the plaque to determine why the complications exist. A dosimetry program written
Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX
A large number of measured electron dose distributions are necessary before a linear accelerator can be utilized clinically. Measurements are made for many field sizes at each energy. The recommended method of measurement is an ion chamber in a water phantom, but a great deal ofaccelerator machine time is needed. The obvious advantages of film dosimetry are high resolution and short beam time. Film has become desirable for measuring isodose distributions and dose profiles when a beam scanner is unavailable or machine time is limited. This basically is because ofthe new near-tissue equivalent, solid, opaque phantom material film cassettes. A quantitative study was performed evaluating the feasibility of using film dosimetry data as the input data for patient treatment planning. A comparison was made between film measurements in a solid phantom and ionchamber measurements in a water phantom for central-axis depth dose and off-axis ratios. Isodose distributions were generated from film data alone. They were also generated from a combination of ion chamber central axis depth dose measurements and film data off axis ratios. The central axis depth dose was in agreement within 1 mm at depths greater than 10 mm. It was recommended that the central-axis depth dose be measured using ionization chambers. Film dosimetry data for the off-axis ratios were in agreement within I%, and therefore were considered to represent an acceptable, machine-time-conserving, alternative means of measurement.
AN ISO~SE SHIFT TECHNIQUEFOR OBLIQUELY INCIDENTELECTRONBEAMS Kenneth Ulin and Edward S. Stemick Medical Physics Division, Department of Radiation Oncology, Tufts-New England Medical Center, Boston, MA Medical Physics, Vol. 16, No. 6, Nov/Dec
1989
When an electron beam is obliquely incident on a flat surface, the isodose lines remain parallel to the surface and are simply shifted toward the surface. The authors have devel-