Radiation Dose–Volume Effects in the Brain

Relationship between volume receiving high-dose irradiation and incidence of radiation necrosis in single-fraction stereotactic radiosurgery. Studies differed in their completeness of follow-up, definition of volume, and definition of radiation necrosis. Graph based on data presented in Table 1. Volume plotted as a point, representing mid-point of volume range. V₁₀ = volume receiving 10 Gy; V₁₂ = volume receiving 12 Gy; RxV = treatment volume. Flickinger data is shown for patients with either radiologic or symptomatic evidence of necrosis (marked as "All"), or only those with symptomatic necrosis (Symp). The other authors' data refers to symptomatic necrosis.

Relationship between biologically effective dose (BED) and radiation necrosis after fractionated radiotherapy. Fit was done using nonlinear least-squares algorithm using Matlab software (The MathWorks, Natick, MA). Nonlinear function chosen was probit model (similar functional form to Lyman model). Dotted lines represent 95% confidence levels; each dot represents data from specific study (Table 2), n = patient numbers as shown. (a) Fraction size <2.5 Gy; (b) fraction size ≥2.5 Gy (data too scattered to allow plotting of “best-fit” line); and (c) twice-daily radiotherapy.