Table 2.

Values of the coefficients α and β in the equation Y = αD + βD² and α/β quotients which gives the dose–response curves for each dose rate.

Dose rate	SSD (cm)	α ± SE × 10	β ± SE × 10	α/β* ± SE
1 Gy/min	171	0.47 ± 0.63	1.20 ± 0.10	0.4 ± 0.5
5 Gy/s	90	1.35 ± 0.52	0.53 ± 0.08	2.6 ± 1.1
50 Gy/s	40	1.28 ± 0.57	0.72 ± 0.09	1.8 ± 0.8
“600 Gy/s”†	20–24	1.57 ± 0.44	0.18 ± 0.07	8.7 ± 4.2

*α/β quotient is the dose at which contributions from single-track (α coefficient) and double-track (β coefficient) events are equal.

^†600 Gy/s is a rough approximation of the average dose rate. Dose was delivered as either two 1.5 Gy pulses or three 2.7 Gy pulses at a pulse duration of 130 ns and repetition rate of 180 Hz.