Table 2.

Comparison of simulated PDDs to measured PDDs in the large snout. E_p is the proton energy at nozzle entrance, r₉₀ is the nominal range at the distal 90% dose location, and m is the nominal SOBP width of the SOBP.

Ep (MeV)	r90 (mm)	m (mm)	Δr90 (mm)	Δm (mm)	ΔDmax (%)
250	250	40	0.04	0.09	2.2
250	250	100	0.40	0.75	1.6
250	250	160	0.42	5.44	2.0
250	207	100	0.90*	7.70*	–
225	206	40	1.00	1.10	3.0
225	206	100	0.50	1.50	2.0
225	206	140	0.80	3.00	1.7
225	166	100	1.50*	7.80*	–
200	165	160	2.17	0.01	1.5
200	165	100	2.15	2.46	1.9
200	165	140	2.27	1.97	1.8
200	138	60	1.60*	2.24*	–
180	137	40	2.05	1.89	2.3
180	137	60	2.12	0.59	2.0
180	137	100	2.22	1.35	2.5
180	111	60	1.13*	6.67*	–
160	110	20	2.05	0.17	3.0
160	110	40	2.03	2.76	2.8
160	110	60	2.02	3.47	3.0
160	110	80	2.07	2.13	2.2
160	110	100	2.11	0.23	1.0
160	85	60	1.06	3.47	3.0
140	84	40	0.61	0.78	1.9
140	74	60	0.69	1.30	2.9
120	63	40	1.07	1.85	1.9
120	63	20	1.24	0.12	2.6
100	43	30	1.17	0.04	2.3
100	35	20	1.28	1.02	2.5

Δr₉₀ is the absolute difference between the simulated and the measured ranges at the distal 90% dose location, Δm is the absolute difference in SOBP width (Δr₉₀ and Δm values with an ‘*’ were compared to the nominal values), and ΔD_max is the maximum absolute dose difference relative to the dose at the center of the SOBP.