Assessment of the α/ß ratios for arteriovenous malformations, meningiomas, acoustic neuromas, and the optic chiasma
Purpose: To determine alpha/beta (α/ß) values of arteriovenous malformations (AVM), meningiomas, acoustic neuromas (AN), and the optic chiasma using clinical data. Methods and materials:Data of dose/fractionation schedules form the literature, iso-effective for a specific clinical outcome, were analysed using the Fraction Equivalent plot (FE) method and the Tucker method. Established safe dose/fractionation schedules for the optic chiasma were used to determine its α/ß value. Results:With the FE plot method, an alpha/beta value of 3.76 Gray (Gy) (95 confidence level [CL]: 2.84.6 Gy) for meningiomas, 2.4 Gy (95 CL: 0.83.9 Gy) for acoustic neuroma, and 14.7 Gy (95 CL: 3.825.7 Gy) for arteriovenous malformations were determined. The respective alpha/beta values using the Tucker method were 3.3 Gy (95CL: 2.26.8 Gy), 1.77 Gy (95CL: 1.33.0 Gy) and-57 Gy (95CL:-79.6 to 35.2 Gy). No meaningful α/ß values could be determined for the optic chiasma. Conclusion:Acoustic neuromas with a low α/ß value would show no lesion intrinsic benefit from fractionation. Meningiomas probably benefit from a hypofractionated schedule. The high α/ß value for AVM can be explained but needs further research. Fractionation versus radiosurgery can be considered when the primary objective is to avoid normal tissue damage. © 2010 Informa UK Ltd.