Computational evaluation of changes in ionizing radiation dose distribution in tissues caused by EM applicators when external radiation and hyperthermia act simultaneously

Figures & data

Figure 1. A cross-section scheme of a micro-strip CFMA-like applicator.

Table I.  Ionizing radiation intensity absorption produced by each element and of the micro-strip CFMA-SRH applicator prototype as a whole.

	μx	μγ		Iat/I0
	80 keV (1 cm^−1)	1.25 MeV (1 cm^−1)	10 MeV (1 cm^−1)	d thickness (cm)	X-rays*	1.25 MeV	10 MeV
Copper films	6.17	0.492	0.143	70 × 10^−4	0.958	0.996	0.999
Fluoroplast	0.2	0.05	0.02	0.1	0.980	0.995	0.998
Silicon rubber frame and bolus	0.241	0.073	0.036	0.22	0.95	0.985	0.992
		0.067	0.031
Water layer	0.175	0.062	0.024	0.5	0.916	0.969	0.988
				1.0	0.839	0.939	0.976
				1.5	0.769	0.911	0.967
				2.0	0.704	0.883	0.953
Silicon oil layer	0.466	0.131	0.059	0.5	0.792	0.936	0.971
Total	—	—	—	0.5**	0.807	0.945	0.977
				1.0**	0.748	0.917	0.974
				1.5**	0.685	0.892	0956
				2.0**	0.627	0.865	0.951

I_at: attenuated radiation intensity, I₀: primary radiation intensity. *E_max = 150 keV, E_av = 80 keV; **water layer thickness.

Figure 2. Calculated photon energy spectrum Clinac 2100C accelerator (Varian) 6 MV. - - - Data from Bagheri and Rogers [21].

Figure 3. Depth radiation dose distribution (DRDD) in a water phantom, z_m = 2 cm. Bremsstrahlung. Accelerating voltage 6 MV. - - - DRDD with a micro-strip applicator on the phantom surface; —— DRDD with a ‘naked’ phantom surface.

Figure 4. Depth radiation dose distribution (DRDD) in a water phantom, z_m = 0.5 cm. Monoenergetic beam 1.25 MeV. - - - DRDD with a micro-strip applicator on the phantom surface; —— DRDD with a ‘naked’ phantom surface.

Table II. Dose distributions in a water phantom for different irradiation combinations; field size 10 × 10 cm²; SSD = 85 cm (E = 1.25 MeV) and 100 cm (V = 6 MV); 10⁻¹⁴ (Gy cm²).

	E0 = 1.25 MeV			V0 = 6 MV
Depth (cm)	(a)	(b)	(c)	(a)	(b)	(c)
0.15	4.09	8.01	7.94	2.53	6.96	6.93
0.40	7.67	7.87	7.85	4.72	6.90	6.83
0.65	8.01	7.76	7.77	5.93	6.83	6.72
1.15	7.86	7.54	7.55	6.71	6.72	6.61
2.15	7.74	7.24	7.24	6.71	6.44	6.52
3.15	7.45	6.84	6.83	6.42	6.17	6.22
4.15	7.18	6.41	6.43	6.14	5.87	5.89
7.15	6.06	5.61	5.61	5.51	5.22	5.24
10.15	4.76	4.40	4.35	4.55	4.28	4.31
15.15	3.36	3.10	3.09	3.43	3.23	3.23
20.15	2.37	2.17	2.16	2.61	2.44	2.45

(a) without any coating; (b) with a MA coating; (c) with a MA-model coating; V₀: accelerating voltage.

Table III.  Dose distributions in a water phantom for different irradiation combinations; field size 10 × 10 cm², SSD = 100 cm and V₀ = 18 MV, 10⁻¹⁴ (Gy cm²).

Depth (cm)	(a)	(b)	(c)
0.15	1.94	10.57	10.51
0.40	4.29	10.88	10.81
0.65	6.25	11.22	11.15
1.15	8.67	11.62	11.50
2.15	10.60	11.77	11.84
3.15	11.34	11.66	11.73
4.15	11.49	11.40	11.44
7.15	10.83	10.47	10.47
10.15	9.32	8.99	8.97
20.15	6.18	5.92	5.93

(a) without any coating; (b) with a MA coating; (c) with a MA-model coating; V₀: accelerating voltage.

Bagheri D, Rogers DWO. Monte-Carlo calculation of nine megavoltage beam spectra using beam code. Med Phys 2002; 29: 391–401

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