Figure 4. (a) Deviations of measured from calculated point dose as a function of distance between inhomogeneity and point of measurement (ionization chamber) for field sizes 5 cm x 5 cm, 10 cm x 10 cm, 15 cm x 15 cm and 20 cm x 20 cm. (b) Deviations of measured from calculated point dose as a function of field sizes for the four distances between inhomogeneity and point of measurement (ionization chamber).