Chapter 6 External Photon Beams: Physical Aspects - IRSN

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226.6 RADIATION TREATMENT PARAMETERS6.6.2 Collimator factorCollimator factor is defined as:• CF is normalized to 1 for thenominal field of 10x10 cm 2 at thenominal SSD for the treatmentmachine.• CF > 1 for fields A exceeding10x10 cm 2 .• CF = 1 for 10x10 cm 2 field.• CF < 1 for fields A smaller than10x10 cm 2 .( Kair( A, h))( )XAh ( , ) air DAh ( , )CF( Ah , ) = Sc ( A, h) = REF( Ah , ) = = =X(10, h) K (10, h) D (10, h)airairIAEA Radiation Oncology Physics: A Handbook for Teachers and Students - 6.6.2 Slide 3 (43/170)6.6 RADIATION TREATMENT PARAMETERS6.6.3 Peak scatter factor Dose to small mass of medium D P at point P is related todose D P at z max in phantom at point P through the peakscatter factor PSFDP( zmax, A, f, h)PSF( Ah , ) =D( A, h)• D P is measured in air with just enough material around point P toprovide electronic equilibrium• D P is measured in phantom at point P at depth z max on centralaxis.• Both D Pand D P are measured with the same field size A definedat a distance f = SSD from the source.PIAEA Radiation Oncology Physics: A Handbook for Teachers and Students - 6.6.3 Slide 1 (44/170)
236.6 RADIATION TREATMENT PARAMETERS6.6.3 Peak scatter factorPSF(A,h) = D (z ,A,f,h)P maxD P (A,h)IAEA Radiation Oncology Physics: A Handbook for Teachers and Students - 6.6.3 Slide 2 (45/170)6.6 RADIATION TREATMENT PARAMETERS6.6.3 Peak scatter factor PSF gives the factor by which the radiation dose at point Pin air is increased by scattered radiation when point P is inthe phantom at depth z max . PSF depends upon:• Field size A(the larger is the fieldsize,the larger is PSF).• <strong>Photon</strong> energy h(except at very lowphoton energies,PSF decreaseswith increasingenergy).IAEA Radiation Oncology Physics: A Handbook for Teachers and Students - 6.6.3 Slide 3 (46/170)
Page 2 and 3: 26.1 INTRODUCTIONRadiotherapy (also
Page 4 and 5: 46.2 QUANTITIES USED IN DESCRIBING
Page 10 and 11: 106.3 PHOTON SOURCES FOR EXTERNAL B
Page 12 and 13: 126.4 INVERSE SQUARE LAW We assume
Page 14 and 15: 146.5 PENETRATION OF PHOTON BEAMS I
Page 16 and 17: 166.5 PENETRATION OF PHOTON BEAMS I
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736.11 SINGLE FIELD ISODOSE DISTRIB
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756.12 CLARKSON SEGMENTAL INTEGRATI
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776.13 RELATIVE DOSE MEASUREMENTS W
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796.13 RELATIVE DOSE MEASUREMENTS W
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816.14 DELIVERY OF DOSE WITH A SING
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836.15 EXAMPLE OF DOSE CALCULATION
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856.16 SHUTTER CORRECTION TIME The
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Chapter 6 External Photon Beams: Physical Aspects - IRSN

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