External Beam External Beam Radiation Therapy Radiation Therapy Special Procedures Special Procedures Kent A. Gifford, Ph.D., Kent A. Gifford, Ph.D., Acknowledgements to : Karl L. Acknowledgements to : Karl L. Prado, Ph.D., Charles Bloch, Prado, Ph.D., Charles Bloch, Ph.D., Peter Balter, Ph.D., Ph.D., Peter Balter, Ph.D., Gurpreet Arora, B.S. Gurpreet Arora, B.S. Department of Radiation Physics Department of Radiation Physics
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External Beam Radiation Therapy Special Procedures Kent A. Gifford, Ph.D., Acknowledgements to : Karl L. Prado, Ph.D., Charles Bloch, Ph.D., Peter Balter,
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External Beam Radiation External Beam Radiation Therapy Special Therapy Special
ProceduresProcedures
Kent A. Gifford, Ph.D., Kent A. Gifford, Ph.D., Acknowledgements to : Karl L. Prado, Acknowledgements to : Karl L. Prado,
Ph.D., Charles Bloch, Ph.D., Peter Balter, Ph.D., Charles Bloch, Ph.D., Peter Balter, Ph.D., Gurpreet Arora, B.S.Ph.D., Gurpreet Arora, B.S.
Department of Radiation PhysicsDepartment of Radiation Physics
Total Body IrradiationTotal Body Irradiation
IndicationsIndications TechniquesTechniques Dosimetry DataDosimetry Data ExamplesExamples
Preparation for marrow or stem-cell Preparation for marrow or stem-cell implantationimplantation Suppress immune system to prevent Suppress immune system to prevent
rejectionrejection Rid body of tumor cells not reached by Rid body of tumor cells not reached by
MDACC TBI Techniques:MDACC TBI Techniques:Mick-Radio Nuclear StandMick-Radio Nuclear Stand
Total Skin IrradiationTotal Skin Irradiation
High Dose-Rate Total Skin Electron High Dose-Rate Total Skin Electron (HDTSE-) Treatment: Technique (HDTSE-) Treatment: Technique DescriptionDescription
feet straight ahead or pointed slightly feet straight ahead or pointed slightly outwards for better balanceoutwards for better balance
elbows at or above shoulder levelelbows at or above shoulder level arms parallel to the scatter platearms parallel to the scatter plate
QA - Patient TLD’sQA - Patient TLD’s
TLD’s are taped to the patient’s skin TLD’s are taped to the patient’s skin and irradiated for one cycle (12 and irradiated for one cycle (12 beams)beams)
reference TLD’s are irradiated using reference TLD’s are irradiated using a 10x10 cma 10x10 cm22 field of 9 MeV electrons field of 9 MeV electrons atat2.0 cm depth (100 cm SSD) in an2.0 cm depth (100 cm SSD) in anacrylic phantomacrylic phantom
TLD’s are taped to the patient’s skin TLD’s are taped to the patient’s skin and irradiated for one cycle (12 and irradiated for one cycle (12 beams)beams)
reference TLD’s are irradiated using reference TLD’s are irradiated using a 10x10 cma 10x10 cm22 field of 9 MeV electrons field of 9 MeV electrons atat2.0 cm depth (100 cm SSD) in an2.0 cm depth (100 cm SSD) in anacrylic phantomacrylic phantom
Elimination of Elimination of motion & setup motion & setup errors means errors means smaller field size smaller field size can be usedcan be used
Reduction in field Reduction in field size allows higher size allows higher dose per fraction, dose per fraction, and reduction in and reduction in number of fractions number of fractions (1 to 5)(1 to 5)
Large dose to small Large dose to small lesions with lesions with minimal dose to minimal dose to surrounding tissue.surrounding tissue.
Single fraction Single fraction ““Out-of-town” Out-of-town”
patientspatients Patients in poor Patients in poor
healthhealth Other patients who Other patients who
might be burdened might be burdened by protracted by protracted treatment.treatment.
Bloch, Ph.D.
SRS QASRS QA
TreatmentTreatment
Typically 5 arcs, about 60 degree Typically 5 arcs, about 60 degree each.each.
5-10 MU/degree 5-10 MU/degree 300 - 600 MU/arc. 300 - 600 MU/arc. 300 MU/min 300 MU/min 1-2 minutes per arc. 1-2 minutes per arc. Total treatment is 5-10 min of beam Total treatment is 5-10 min of beam
time.time. Room entries between arcs to move Room entries between arcs to move
couch and re-check patient couch and re-check patient alignment.alignment.