Definitions_Notation

Definitions_Notation - Definitions and notations from TG51...

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Definitions and notations from TG51 % dd (10) x : the photon component of the photon beam percentage depth-dose at 10 cm depth in a 10 x 10 cm2 field on the surface of a water phantom at an SSD of 100 cm ( see Sec. VIII B ) % dd (10): the measured photon beam percentage depth-dose at 10 cm depth in a 10 x 10 cm 2 field on the surface of a water phantom at an SSD of 100 cm. % dd (10) includes the effects of electron contamination in the beam, whereas % dd (10) x does not. % dd (10) is measured in an open beam. % dd (10) Pb : same as % dd (10) except that a 1 mm lead foil is in place below the accelerator at about 50 cm from the phantom surface ( or 30 cm if 50 cm clearance is not available ) clinical reference dosimetry : determination of absorbed dose to water per MU under reference conditions in the clinic. Q w D : the absorbed dose to water for a given number of monitor units ( or minutes for 60Co) from a radiation beam of quality Q . Unit: gray, Gy. d max: the depth (cm) at which the absorbed dose to water ( not ionization ) is a max for a given beam. In photon beams it may include effects of electron contamination in the incident beam. d ref : the reference depth for electron beams given as d ref=0.6 R 50 - 0.1, where R 50 is in cm. I 50 : the depth in an electron beam at which the gradient-corrected ionization curve falls to 50% of its maximum ( see Sec. VIII C ) . Unit: cm. k Q : the quality conversion factor, which accounts for the change in the absorbed-dose to water calibration factor between the beam quality of interest, Q , and the beam quality for which the absorbed-dose calibration factor applies ( usually 60 Co) [ see Eq. ( 2 )] . k Q is a function of the beam quality Q [ specified by % dd (10) x or R 50 ] and is chamber dependent. For 60 Co beams k Q = 1.000. k R 50 : the component of k Q in an electron beam which is independent of the ionization gradient at the point of measurement ( i.e., k Q = k R 50 Q gr P (see Secs. IV and XB ) . k R 50 is a function of the electron beam quality specified by R 50 ' 50 R k , k ecal
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This note was uploaded on 03/30/2008 for the course TG 51 taught by Professor Staff during the Fall '08 term at Duke.

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Definitions_Notation - Definitions and notations from TG51...

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