Clinical validation of the Acuros XB photon dose calculation algorithm, a grid-based Boltzmann equation solver

Figures & data

Table I. Nomenclature and description of the treatment plans. For the volumetric modulated arc therapy plans the monitor units have been set to 200 MUs and 400 MUs.

Plan number	Treatment plan name	Description	Number of fields	MLC	Field size (cm^2)	Position of iso center
1	AP	G = 0°	1	No	25 × 25	Centrally in mediastinum
2	PA	G = 180°	1	No	25 × 25	Centrally in mediastinum
3	Op APPA	G = 0°, 180°	2	Yes	16 × 17	Centrally in mediastinum
4	Lat dxt	G = 270°	1	No	18 × 18	Centrally in mediastinum
5	Lat op	G = 90°, 270°	2	Yes	18 × 18	Centrally in mediastinum
6	4 field box	G = 0°, 90°, 180°, 270°	4	Yes	16 × 16	Centrally in mediastinum
7	Wedge	fields with wedges	3	Yes	10 × 18	Centrally in mediastinum
8	IMRT	intensity modulated fields	6	Yes	20 × 20	Centrally in mediastinum
9	VMAT200MU	VMAT, 2 arcs of 179°, cw and ccw	2	Yes	25 × 25	Centrally in mediastinum
10	VMAT400MU	VMAT, 2 arcs of 179°, cw and ccw	2	Yes	25 × 25	Centrally in mediastinum
11	Spine SBRT	5 fields with 30° separation	5	No	2 × 2	In the spine

AP: 1 anterio-posterior field; PA: 1 posterio-anterior field; OpAPPA: 2 opposing anterior-posterior fields; Lat dxt: 1 lateral field from the right side; Lat op: 2 lateral opposing fields; 4 field box: 4 fields at the specified gantry angles; Wedge: wedged fields; IMRT: intensity modulated fields; VMAT200MU and VMAT400MU: Volumetric modulated fields; Spine SBRT: steroetactic body radiotherapy of the spine.

Figure 1. Depth dose curve for 6 MV and 15 MV photon beam at FS 10 × 10 cm² and 40 × 40 cm².

Figure 2. A comparison of measured and calculated profiles using both Acuros XB and AAA at d = 1.5 cm, 10 cm and 300 cm for 6 MV photons. Only half of the (symmetric) profiles are shown. FS: 1 × 1 cm², 10 × 10 cm², 20 × 20 cm² and 40 × 40 cm².

Figure 3. Measured and calculated (Acuros XB and AAA) profiles for the asymmetric half beam field 20 × 10 (Y₁ = −20, Y₂ = 0) at d = 10 cm and SSD = 90 cm.

Table II. Percentage of points fulfilling the Gamma (3,3) agreement index for the treatment plans delivered with 6 MV and 15 MV photons. The mean value and standard deviation has been calculated for each energy. The treatment plans are specified in Table I.

	6 MV		15 MV
Treatment plan name	Acuros XB G (3,3) (%)	AAA G (3,3) (%)	Acuros XB G (3,3) (%)	AAA G (3,3) (%)
AP	97.8	76.5	99.5	92.5
PA	96.5	85	99.2	92.5
Op APPA	96.4	96.9	99.8	90
Lat dxt	98.1	94.7	99	98.3
Lat op	99.3	96.4	99.3	94.6
4 field box	100	97.5	99.7	96.3
Wedge	99.4	98.3	99.5	96.7
IMRT	97.8	96.7	99.4	98.6
VMAT200MU	99.1	97.2	100	100
VMAT400MU	98.2	96	99.5	97.8
Spine SBRT	98.3	100	100	100
Mean value	98.2	94.1	99.5	96.1
Standard deviation	1.1	7.0	0.3	3.3

Figure 4. Comparison of the dose measured at the films at a point centrally in the vertebral body for all 22 treatment plans, to the dose calculated at the same point for the two algorithms. The deviation in dose is given as (D_film – D_calculated)/D_film*100. The plan number is specified in Table I.

Figure 5. a) Depth dose curves evaluated at the central axis of the thorax phantom for the field “AP” delivered with 6 MV photons. b) Lateral profile for the field “Lat op” delivered with 6 MV photons. The profile is evaluated at the depth of the vertebral body. The calculation of dose to a small volume of water in the vertebral body was performed for Acuros XB for a few points for both fields.