Figure 4. Comparison of peripheral dose distributions measured on a helical tomotherapy system and various conventional 6‐MV beams. The tomotherapy and 21‐EX measurements were taken with a $1\times 40\hspace{0.17em}{\text{cm}}^2$ field size. Mutic et al. ⁽⁹⁾ data measured at $d_{max}$ with the MLC set to $15\times 15\hspace{0.17em}{\text{cm}}^2$. Stern ⁽¹⁰⁾ data measured at a depth of 5 cm with the MLC set to $10\times 10\hspace{0.17em}{\text{cm}}^2$. Giessen ⁽¹¹⁾ averaged measurements for 4‐ to 25‐MV linear accelerators with a $5\times 5\hspace{0.17em}{\text{cm}}^2$ field size. TG‐36 values were measured at $d_{max}$ for a field size of $15\times 15\hspace{0.17em}{\text{cm}}^2$.