Impact of dose calculation algorithm on radiation therapy

Table 1 Calculated percent mean tumor control probability values (ranges in parentheses) for all algorithms as a function of planning target volume volume

PTV bins (cm3)	Mean PTV volume(range, cm3)	n	EPL-1D	EPL-3D	AAA	CCC	Acuros	MC
4 ≤ v < 10	7.8 (4.8-9.9)	15	100.0 (100-100)	99.9 (99.6-100)	93.1 (76.3-99.8)	91.3 (63.0-99.9)	91.8 (60.8-99.8)	90.5 (51.1-99.9)
10 ≤ v < 20	15.0 (10.4-19.8)	27	100.0 (99.8-100)	99.9 (99.5-100)	91.3 (61.7-100)	91.3 (50.4-100)	91.4 (65.4-99.9)	91.1 (53.2-100)
20 ≤ v < 30	24.3 (20.4-29.6)	29	98.5 (99.8-100)	98.9 (77.6-100)	92.7 (74.9-99.9)	90.5 (46.4-99.9)	90.9 (65.1-99.9)	91.1 (48.4-99.9)
30 ≤ v < 40	34.9 (30.2-39.8)	18	99.8 (97.4-100)	99.6 (98.2-100)	92.0 (63.4-99.9)	92.1 (69.7-99.9)	90.9 (61.6-99.8)	92.4 (56.3-99.9)
40 ≤ v < 60	47.3 (40.2-58.4)	17	99.5 (93.1-100)	99.1 (95.6-100)	92.6 (78.6-99.9)	91.4 (64.4-99.9)	93.6 (77.6-99.9)	92.3 (63.6-99.9)
60 ≤ v < 100	78.0 (60.4-95.9)	16	99.5 (95.6-100)	99.0 (95.8-100)	92.7 (70.7-99.8)	92.8 (66.2-99.9)	93.4 (70.4-99.8)	94.7 (74.6-99.9)
V ≥ 100	162.4 (100.5-360.2)	11	99.2 (96.1-99.9)	98.7 (95.0-100)	96.3 (89.9-100)	95.6 (91.6-99.8)	95.3 (83.0-99.9)	97.1 (88.8-99.9)

PTV: Planning target volume; EPL-1D: 1-D equivalent path-length (pencil beam-type); EPL-3D: 3-D equivalent-path-length (pencil beam-type); AAA: Anisotropic analytical algorithm; CCC: Collapsed cone convolution-superposition; Acuros: Acuros AXB; MC: Monte Carlo. (Cited from Chetty et al[30] 2013).

Table 2 Relative differences calculated as (without-with)/with density corrections using each algorithm

	Eclipse AAA	OTP CC	Pinnacle CC	XiO Sup	OTP PB	XiO FFT
Combined lungs
NTCPBurman	-0.29	-0.2	-0.22	-0.25	-0.36	-0.45
NTCPSeppenwoolde	-0.19	-0.13	-0.12	-0.15	-0.23	-0.3
Mean dose	-0.08	-0.05	-0.05	-0.06	-0.09	-0.13
V20	-0.06	-0.06	-0.04	-0.03	-0.05	-0.07
Heart
NTCP	-0.19	-0.15	-0.15	-0.13	-0.17	-0.21
Mean dose	-0.06	-0.05	-0.05	-0.05	-0.06	-0.09
V50	-0.11	-0.1	-0.1	-0.08	-0.08	-0.13
PTV
Mean dose	-0.06	-0.05	-0.05	-0.05	-0.13	-0.1
D01	-0.05	-0.05	-0.04	-0.04	-0.1	-0.11
D99	-0.07	-0.04	-0.05	-0.05	-0.14	-0.09
GTV
Mean dose	-0.07	-0.06	-0.06	-0.06	-0.08	-0.1
D01	-0.07	-0.07	-0.06	-0.06	-0.09	-0.11
D99	-0.07	-0.06	-0.06	-0.06	-0.07	-0.1

Negative results indicate lower values when no density corrections are included. Eclipse AAA: Eclipse Anisotropic Analytical Algorithm; OTP CC: Oncentra MasterPlan Collapsed Cone algorithm; Pinnacle CC: Pinnacle Collapsed Cone algorithm; XiO Sup: XiO Multigrid Superposition algorithm; OTP PB: Oncentra MasterPlan Pencil Beam algorithm; XiO FFT: XiO Fast Fourier Transform Convolution algorithm. (Cited from Nielsen et al[34] 2011).

Table 3 Clinical impact of dose calculation algorithms

Ref.	Tumor site/technique	Algorithms studied	Results/conclusion
Nielsen et al[34], 2011	NSCLC	Eclipse AAA OTP CC Pinnacle CC XiO Sup OTP PB XiO FFT	Differences in dose to target predicted by the different algorithms are of a magnitude. Calculated NTCP values for pneumonitis are more sensitive to the choice of algorithm than mean lung dose and V20
Chandrasekaran et al[38], 2011	Lung/3DCRT,SBRT	PBC, Eclipse AAA, Pinnacle CCC, Masterplan PBC and CCC	PBC yielded higher TCP in comparison with other algorithms. For small tumor, TCP was overestimated by 4%-13% by PBC; for large tumor, there was an increase of up to 6%-22%
Liu et al[39], 2013	Lung/SABR	EPL, MC	EPL overestimates dose by amounts that substantially decrease TCP in a large proportion. Compared with MC, prescribing based on EPL translated to a median TCP decrement of 4.3% (range, 1.2%-37%) and a > 5% decrement in 46% of tumors
Bufacchi et al[33], 2013	Prostate, HN, Lung, Breast /3DCRT	PBC, AAA	NTCP calculated with AAA was lower than the NTCP calculated with PBC, except for the breast treatments
Chetty et al[30], 2013	NSCLC/SABR	EPL-1D, EPL-3D, AAA, CCC, Acuros, MC	Average TCP decrements (5%-10%, ranging up to approximately 50%) were observed with model-based algorithms relative to the EPL-based methods

Eclipse AAA: Eclipse Anisotropic Analytical Algorithm; OTP CC: Oncentra MasterPlan Collapsed Cone algorithm; Pinnacle CC: Pinnacle Collapsed Cone algorithm; XiO Sup: XiO Multigrid Superposition algorithm; OTP PB: Oncentra MasterPlan Pencil Beam algorithm; XiO FFT: XiO Fast Fourier Transform Convolution algorithm; EPL: Equivalent path length; MC: Monte Carlo.