Table I.

Neutron source strength (Q) values for various linac model and energy combinations.

Manufacturer	Model	Nominal MV	Q values ($\times {10}^{12}$ neutrons per Gy)	Std. Deviation ($\times {10}^{12}$)	No. of Linac s	Published Q values ($\times {10}^{12}$)
Varian	1800	10				0.06
Varian	1800	15				0.76
Varian	1800	18				1.22
Varian	2100C	18	0.96	0.11	17
Varian	2100C b	18	0.87		1
Varian	2300CD	18	0.95	0.03	2
Varian	2500	24	0.77		1
Siemens	MD2	10	0.08		1
Siemens	MD	15	0.20	0.02	2
Siemens	KD	18	0.88	0.10	2
Siemens	KD	20				0.92
Siemens	Primus a	10	0.02		1
Siemens	Primus a	15	0.12		1
Siemens	Primus b	15	0.21		1
Siemens	Primus	15			1	0.20
Elekta	SL‐20	17				0.69
Elekta	SL‐20	18	0.46		1
Elekta	SL‐25	18	0.46		1
Elekta	SL‐25	22				2.37
Elekta	SL‐25	25	1.44	0.31	3
GE	Saturne 41	12				0.24
GE	Saturne 41	15				0.47
GE	Saturne 43	18	1.32		1	1.50
GE	Saturne 43	25				2.40

^aWith MiMIC device in place.

^bWith the multileaf collimator set to a $3.8-{\text{cm}}^2\times 3.8-{\text{cm}}^2$ field.