線性二次方(LQ)模式之臨床運用與不完全修復的重要

Clinical Application of the LQ Model and the Importance of Incomplete Repair Between Fractions in a Multl-Fraction-Per-Day Regimen

任益民(Yee-Min Jen)

《放射治療與腫瘤學》 1卷1期 (1994/03) Pp. 55-62

https://doi.org/10.6316/TRO/199401(1)55

並列摘要

How to compare the biological effects of different irradiation schemes and convert isoef-fectively one scheme into another is of great clinical significance. The NSD and the ensuing TDF methods are the earliest trials that had been successsfully applied to some extent in clinical settings. However, its drawbacks are many, particularly when late responding tissues are concerned. The LQ model has been shown to have a great potential in calculating biological effects using the α/β ratios and several LQ-derived equations. The basic formula for these equations is the BED (biologically effective dose) with the following form(方程式),where d=dose/fraction and D=total dose. The LQ model can be used in several ways. For example when the initial regimen using d, and DL is to be shifted to a regimen using a fraction dose of d2, the total dose. leading to the same effect, D2, can be calculated using the following(方程式) If a new fraction number n2 is chosen for some reasons, the fraction dose, d2, leading to an
isoeffect, can be calculated using the equation(方程式)However, when more than 1 fraction per day are used, incomplete repair may become significant due to a repair half time longer than 2 to 3 hours, and the LQ model must be modified to account for the increased creased biological effect caused by the incomplete repair: (方程式) incomplete repair factor. When prologned exposure is used, the repair occuring during the irradiation period must also be corrected(方程式) where g=continuous repair factor.
Yet as much related knowledge, such as repair half time, is not clearly defined in many normal tissues, the clinical use of all these LQ-based formulae should be conducted with great caution.