Figure 8.

Peripheral dose profile in CTDI body phantom for measured beam width of 34.1 mm, pitch 0.87, pitch 0.74, and pitch 0.9 helical scans. Pitch 0.87 is the desired pitch value predicted to produce the most uniform dose profile. Knowledge of the FWHM of the actual beam width is required to determine this value, as in Eq. 2. Pitch 0.74 is the calculated pitch value to smooth peripheral dose variations when the measured beam width is not taken into account [i.e., the pitch calculated from Eq. 1]. Pitch 0.9 is the pitch value available on this scanner that is closest to the desired pitch value.