Evaluation of the Position Error of Wearing Surgical Masks During Radiotherapy in Head and Neck Cancer Patients

Figures & data

Table 1 Patient Characteristics

Characteristics	With Mask	Without Mask
	n=38, n (%)	n=43, n (%)
Age (mean, SD)	60.5 (13.1)	53.7 (12.8)
Gender
Male	22 (57.8)	24 (55.8)
Female	16 (42.1)	19 (44.1)
Thermoplastic mask type
HN	20 (52.6)	39 (90.7)
HNS	18 (47.4)	4 (9.3)
Headrest type
Type B	27 (71.0)	38 (88.4)
Type C	11 (28.9)	5 (11.6)
Treatment fraction (mean, SD)	28.6 (6.6)	29.3 (5.3)
Treatment dose (Gy) (mean, SD)	58.3 (10.4)	57.6 (10.5)
Diagnosis
Oropharynx	7(18.4)	4(9.3)
Hypopharynx	2(5.3)	1(2.3)
Oral cavity	4(10.5)	6(14.0)
Brain	21(55.3)	26(60.5)
Nasopharynx	2(5.3)	1(2.3)
Other	2(5.3)	5(11.6)

Abbreviation: SD, standard deviation.

Figure 1 Patient Immobilization: (A) Head and neck (HN) mask and type B headrests. (B) Head-neck-shoulder (HNS) mask and type C headrest.

Figure 2 The box plots of the position error for each axis. (A) Translational errors in the X, Y, and Z directions (B) Rotational errors in the Yaw, Pitch, and 3D vector.

Note: *p<0.05.

Table 2 Position Errors and Independent t-Test Results of 59 Cases of the HN Mask

	HN/type B Headrest			HN/type C Headrest
	With Mask	Without Mask	p-value	With Mask	Without Mask	p-value
Axes	Mean ± SD	Mean ± SD		Mean ± SD	Mean ± SD
X (cm)	−0.03±0.12	−0.01±0.16	0.41	−0.07±0.17	−0.12±0.08	0.74
Y (cm)	−0.02±0.13	−0.04±0.14	0.77	−0.17±0.02	−0.01±0.10	0.11
Z (cm)	−0.01±0.10	−0.10±0.64	0.93	−0.14±0.06	−0.01±0.36	0.71
3D (vector)	0.28±0.07	0.31±0.11	0.35	0.35±0.09	0.41±0.11	0.59
Yaw(°)	0.18±0.58	0.30±0.11	0.10	−0.63±0.60	−0.11±0.62	0.45
Pitch(°)	0.19±0.70	0.50±0.50	0.09	0.26±0.69	0.44±0.87	0.81

Note: The P value calculated from independent t-test.

Abbreviations: SD, standard deviation; X, right-left direction; Y, superior-inferior direction; Z, anterior-posterior direction; 3D, three-dimensional.

Table 3 Position Errors and Independent t-Test Results of 22 Cases of the HNS Mask

	HNS/type B Headrest			HNS/type C Headrest
	With Mask	Without Mask	p-value	With Mask	Without Mask	p-value
Axes	Mean ± SD	Mean ± SD		Mean ± SD	Mean ± SD
X (cm)	−0.02±0.07	0.01±0.09	0.74	−0.05±0.07	−0.11±0.01	0.04*
Y (cm)	−0.06±0.13	0.06±0.02	0.63	−0.05±0.11	−0.11±0.15	0.72
Z (cm)	0.01±0.18	−0.02±0.09	0.76	−0.04±0.14	0.05±0.32	0.77
3D vector	0.32±0.07	0.31±0.09	0.95	0.29±0.14	0.40±0.08	0.22
Yaw(°)	−0.04±0.40	−0.05±0.09	0.96	−0.19±0.39	0.18±0.50	0.51
Pitch(°)	−0.34±0.59	0.17±0.14	0.07	0.34±0.29	0.83±0.08	0.01*

Notes: The P value calculated from independent t-test. *p<0.05.

Abbreviations: SD, standard deviation; X, right-left direction; Y, superior-inferior direction; Z, anterior-posterior direction; 3D, three-dimensional.

Table 4 Systematic Errors, Random Errors and Estimated Margins Between the Two Groups

	HN/HNS
Axes	With Mask			Without Mask
	Σ	σ	MPTV	Σ	σ	MPTV
X (cm)	0.10	0.15	0.36	0.09	0.15	0.33
Y (cm)	0.13	0.17	0.44	0.14	0.17	0.47
Z (cm)	0.13	0.14	0.42	0.14	0.16	0.46

Abbreviations: X, right-left direction; Y, superior-inferior; Z, anterior-posterior direction; Σ, systematic errors; σ, random errors; M_PTV, estimated margins.