Predictive value of SAR based quality indicators for head and neck hyperthermia treatment quality

Figures & data

Figure 1. Schematic work-flow of the adopted methodology.

Table 1. Electromagnetic and thermal tissue parameters at 434 MHz accordingly to Verhaart et al. [22].

	${ϵ}_r$	$\sigma \mathrm{ }\left[\frac{S}{m}\right]$	$\rho \mathrm{ }\left[\frac{\mathit{kg}}{m^3}\right]$	$c\mathrm{ }\left[\frac{J}{\mathit{kg}}°C\right]$	$k\mathrm{ }\left[\frac{W}{m^{-1}}°C\right]$	$Q\mathrm{ }\left[\frac{W}{\mathit{kg}}\right]$	$\omega \mathrm{ }[\mathit{ml}/\mathit{minkg}]$
Internal Air	1.0	0.0	1.2	–	–	–	–
Lung	23.6	0.38	284	–	–	–	–
Muscle	56.9	0.81	1090	3421	0.4	0.96	442.8
Fat	11.6	0.08	911	2348	0.5	0.51	255
Bone	13.1	0.09	1908	1313	0.32	15	10
Cerebrum	56.8	0.75	1045	3696	0.55	15.5	763.3
Cerebellum	55.1	1.05	1045	3653	0.51	15.7	770
Brain Stem	41.7	0.45	1046	3630	0.51	11.4	5586
Myelum	35	0.46	1075	3630	0.51	2.48	160.3
Sclera	57.4	1.01	1032	4200	0.58	5.89	380
Lens	37.3	0.38	1076	3133	0.43	–	–
Vitreous Humor	69	1.53	1005	4047	0.59	–	–
Optical Nerve	35	0.46	1075	3613	0.49	2.48	160.3
Cartilage	45.1	0.6	1100	3568	0.49	0.54	35
Thyroid	61.3	0.89	1050	3609	0.52	87.1	5624.3
HTV	59	0.89	1050	3950	1.5	–	848

Table 2. Correlation coefficient (R²) with the median temperature T50 on a per-patient basis.

ID	TV [cm^3]	R^2TC25	R^2TC50	R^2TC75	R^2THQ
A*	129.1	0.60	0.60	0.48	0.61
B*	412.4	0.28	0.35	0.32	0.40
C*	291.8	0.25	0.26	0.27	0.33
D*	105.0	0.76	0.82	0.64	0.94
E*	57.4	0.81	0.71	0.61	0.83
F	34.4	0.90	0.86	0.61	0.95
G	36.7	0.75	0.78	0.69	0.77
H*	135.7	0.77	0.56	0.27	0.42
I	18.3	0.76	0.86	0.84	0.94
L	38.1	0.91	0.78	0.43	0.91
M	28.7	0.87	0.88	0.75	0.96
N	45.8	0.82	0.90	0.74	0.94
O	39.1	0.46	0.86	0.78	0.02
P	24.1	0.84	0.78	0.52	0.93
Q*	242.6	0.93	0.85	0.61	0.87
mean		0.71	0.72	0.57	0.72
meanHTV<50cm^3		0.79	0.84	0.67	0.80
meanHTV>50cm^3		0.63	0.59	0.46	0.63

Note: Indicates if HTV > 50 cm³.

Table 3. Correlation coefficient (R²) with the median temperature T90 on a per-patient basis.

ID	TV [cm^3]	R^2TC25	R^2TC50	R^2TC75	R^2THQ
A*	129.1	0.52	0.55	0.47	0.65
B*	412.4	0.34	0.37	0.36	0.20
C*	291.8	0.05	0.07	0.12	0.28
D*	105.0	0.80	0.81	0.60	0.92
E*	57.4	0.73	0.49	0.40	0.74
F	34.4	0.70	0.47	0.25	0.56
G	36.7	0.69	0.53	0.40	0.77
H*	135.7	0.63	0.61	0.45	0.28
I	18.3	0.74	0.85	0.81	0.91
L	38.1	0.86	0.88	0.59	0.94
M	28.7	0.82	0.87	0.75	0.93
N	45.8	0.83	0.82	0.53	0.91
O	39.1	0.50	0.83	0.62	0.02
P	24.1	0.82	0.73	0.52	0.91
Q*	242.6	0.91	0.80	0.57	0.87
mean		0.66	0.65	0.50	0.66
meanHTV<50cm^3		0.75	0.75	0.56	0.74
meanHTV>50cm^3		0.57	0.53	0.42	0.56

Note: Indicates if HTV > 50 cm³.

Figure 2. Inter-patient correlation of all indicators with T50. Each indicator is individually plotted. On each subfigure, the SAR indicator name is displayed and the correlation coefficients (R²) are reported.

Figure 3. Inter-patient correlation of all indicators with T90. Each indicator is individually plotted. On each subfigure, the SAR indicator name is displayed and the correlation coefficients (R²) are reported.

Table 4. Inter-patient correlation coefficient (R2) with T50 and T90 for all patients and separately for the large and small cases.

	T50			T90
	Overall	HTV < 50cm^3	HTV > 50cm^3	Overall	HTV < 50cm^3	HTV > 50cm^3
$R_{\mathit{TC}25}^2$	0.76	0.76	0.73	0.54	0.47	0.56
$R_{\mathit{TC}50}^2$	0.74	0.74	0.68	0.56	0.54	0.48
$R_{\mathit{TC}75}^2$	0.49	0.48	0.51	0.38	0.36	0.35
$R_{\mathit{THQ}}^2$	0.37	0.46	0.37	0.11	0.15	0.01

Figure 4. Normalized SAR distribution (left column) and corresponding temperature distribution (right column) for patients ID E, D and F (1st, 2nd and 3rd row respectively). Undesired heating in the proximity of the skin is mitigated by the effect of the water bolus.

Verhaart RF, Verduijn GM, Fortunati V, et al. Accurate 3D temperature dosimetry during hyperthermia therapy by combining invasive measurements and patient-specific simulations. Int J Hyperthermia. 2015;31:686–692.

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