Comparison of conventional inserts and an add-on electron MLC for chest wall irradiation of left-sided breast cancer

Figures & data

Figure 1.  Schematic view of the lower part of the Varian 2100 C/D linac treatment head for the insert (left side) and eMLC geometries (right side). Also the applied treatment distance for both collimators is shown for reference.

Figure 2.  Beams eye-view of the chest wall irradiation with adjacent electron beams E1 and E2 together with a matched photon beam (P). The central axis is marked with (+) and the operation scar crossing the electron fields is shown with an X-ray positive wire.

Figure 3.  Electron beam dose distributions for one of the patients with 6 and 9 MeV electrons and 6 MV photons, (a) insert plan and (b) eMLC plan. The PTV is marked with a white line.

Figure 4.  Dose-volume histograms for the insert (--) and eMLC (-) plans for the patient of Figure 3.

Table I.  Dose and volume differences of the DVH calculations between the eMLC and insert-based treatment plans (N=10)

	eMLC mean±SD	Insert mean±SD	Mean diff.±SD	p-value1
PTV D5% (Gy)	60.88±1.53	59.06±1.41	1.82±1.02	<0.001
PTV D10% (Gy)	58.11±1.53	56.74±1.16	1.37±0.87	<0.001
PTV D50% (Gy)	51.99±1.17	50.82±0.97	1.17±0.68	<0.001
PTV mean dose (Gy)	50.68±0.90	49.47±1.01	1.21±0.66	<0.001
left lung V20 Gy (%)	34.51±8.31	34.02±8.37	0.48±0.21	<0.001
left lung V30 Gy (%)	28.66±7.25	28.16±7.26	0.51±0.18	<0.001
heart V20 Gy (%)	3.43±3.42	3.28±3.22	0.14±0.11	<0.01
heart V30 Gy (%)	1.53±1.92	1.42±1.91	0.11±0.11	<0.01

1for the paired differences