Erratum: "AAPM protocol for 40-300 kV x-ray beam dosimetry in radiotherapy and radiobiology": AAPM protocol for 40-300 kV x-ray beam dosimetry in radiotherapy and radiobiology (Medical Physics, (2001), 28, 6, (868-893), 10.1118/1.1374247)

In Ma et al.,¹ two typographic errors were found in the printed version of the report. A division symbol was missing in Eq. (2), which shows the relation between the air-kerma calibration factor, N_K, and the frequently used exposure calibration factor, N_X. The correct equation should be 2 (Figure presented.) where (W/e)_air is the average energy expended per unit charge of ionization produced in dry air, having the value 33.97 J/C, and (1 − g) corrects for the effect of radiative losses (mainly due to bremsstrahlung emission) by the secondary charged particles, and g is less than 0.1% for photons below 300 keV in air. Eq. (7) was recommended for deriving the end effect, δt, as described by Attix.² The correct equation for calculating δt should be 7 (Figure presented.) where M₁ and M₂ are the chamber readings for exposure time Δt₁ and Δt₂, respectively. Note that δt can either be positive or negative. To ensure the accuracy of the measured end effect, the graphical method shall be used during the machine commissioning and annual QA. The mathematical method may be used for the monthly QA measurement.