Chapter 6 External Photon Beams: Physical Aspects - IRSN

196.6 RADIATION TREATMENT PARAMETERSDosimetric functions used in the whole photon energy range:• Percentage depth dose (PDD)• Relative dose factor (RDF)Dosimetric functions used at cobalt-60 and below:• Peak scatter factor (PSF)• Collimator factor (CF)• Scatter factor (SF)• Scatter function (S)• Tissue air ratio (TAR)• Scatter air ratio (SAR)Dosimetric functions used at cobalt-60 and above:• Tissue maximum ratio (TMR)• Tissue phantom ratio (TPR)• Scatter maximum ratio (SMR)IAEA Radiation Oncology Physics: A Handbook for Teachers and Students - 6.6 Slide 4 (37/170)6.6 RADIATION TREATMENT PARAMETERS6.6.1 Radiation beam field sizeFour groups of field shape are used in radiotherapy:• Square (produced with collimators installed in therapy machine).• Rectangular (produced with collimators installed in therapymachine).• Circular (produced with special collimators attached to treatmentmachine).• Irregular (produced with custom made shielding blocks or withmultileaf collimators).For any arbitrary radiation field and equivalent squarefield or equivalent circular field may be found. The equivalentfield will be characterized with similar beamparameters and functions as the arbitrary radiation field.IAEA Radiation Oncology Physics: A Handbook for Teachers and Students - 6.6.1 Slide 1 (38/170)