Theoretical analysis of the dose dependence of the oxygen enhancement ratio and its relevance for clinical applications

Table 2 Summary of references to published mammalian cell survival data measured in experiments at high LET

Ref.	Cells	Rad. type	LET (keV/μm)	α_a/α_h	(β_a/β_h)^1/2	OER(D)
[26]	V79	argon	94	1.5	3.4	↗
[45]*	V79	carbon	102	2.7	1.1	↘
	V79	neon	110	2.0	1.3	↘
	HSG	carbon	88	2.2	1.3	↘
	HSG	neon	84	2.9	1.6	↘
[38]	R1	α-particles	110			→
[39]	R1	carbon	95			→
[46]	R1	carbon	90	2.0	1.6	↘
	R1	carbon	95	1.8	1.7	→
	R1	neon	90	1.4	1.9	↗
	R1	neon	120	1.7	1.5	→
	R1	argon	95	2.1	1.3	↘
[41]	T1	carbon	85	2.7	1.4	↘
	T1	neon	100	1.8	2.9	↗
	T1	argon	81	2.3	2.4	→
	T1	argon	91	2.0	2.5	↗
	T1	argon	117	1.7	1.7	→
[44]	U251	8 keV x-rays	> 50	1.3	> 2.9	↗

*Because of the large amount of the data in this reference for the LET range between 80 and 120 keV/μm, only a few representative cases are listed here to demonstrate the OER behavior.
For each reference the cell line, the ion beam type, the LET, the ratios of the radiosensitivity parameters (if provided) under aerobic (a) and hypoxic (h) conditions and the OER behavior as a function of dose (↗ increases, ↘ decreases or → remains nearly constant with increasing single dose) are given. The high-LET range was chosen between 80 and 120 keV/μm.