Chapter 6 External Photon Beams: Physical Aspects - IRSN

426.8 CENTRAL AXIS DEPTH DOSES IN WATER: SAD SETUP6.8.2 Relationship between TAR and PDDPDD( zAfh , , , ) f+z TAR( zA ,Q, h) = PSF( Ah , ) 100 f+ zmaxSpecial case at z = z maxgives PDD(z max ,A,f, h) = 1002TAR(z max,A P,h) PSF(A,h)IAEA Radiation Oncology Physics: A Handbook for Teachers and Students - 6.8.2 Slide 2 (83/170)6.8 CENTRAL AXIS DEPTH DOSES IN WATER: SAD SETUP6.8.2 Relationship between TAR and PDDPDD( zAfh , , , ) f+z TAR( zA ,Q, h) = PSF( Ah , ) 100 f+ zmax2• Since the TAR does not depend on SSD, a single TAR tablefor a given photon beam energy may be used to cover allpossible SSDs used clinically.• Alternatively, PDDs for any arbitrary combination of z, A and f= SSD may be calculated from a single TAR table.IAEA Radiation Oncology Physics: A Handbook for Teachers and Students - 6.8.2 Slide 3 (84/170)