Interfractional set-up errors evaluation by daily electronic portal imaging of IMRT in head and neck cancer patients

Figures & data

Table I.  Characteristics of 20 head and neck cancer patients.

Age	Gender	Primary site	Stage	Histology
58	M	Oropharynx	T3N2a	Epidermoid
75	M	Oropharynx	T1N0	Epidermoid
40	M	Oropharynx	T2N1	Epidermoid
82	M	Oropharynx	T3N2	Epidermoid
61	M	Oropharynx	T2N1	Epidermoid
51	M	Oropharynx	T3N0	Epidermoid
45	F	Oropharynx	T2N1	Epidermoid
55	M	Oropharynx	T1N2b	Epidermoid
58	M	Oropharynx	T2N2b	Epidermoid
46	M	Oropharynx	T1N3	UC
51	M	Nasopharynx	T3N0	Epidermoid
37	M	Nasopharynx	T3N2c	Epidermoid
51	F	Nasopharynx	T3N2c	UC
61	M	Nasopharynx	T2N1	UC
31	F	Nasopharynx	T1N0	UC
48	F	Nasopharynx	T1N0	UC
17	M	Paranasal sinus	T4N0	Rhabdomyosarcom
49	F	Paranasal sinus	T4N0	Adenoid kystic
41	M	Hard palate	T2N0	Adenoid kystic carcinoma
16	F	Hypopharynx	T4N2b	Rhabdomyosarcoma

SCC: squamous cell carcinoma (instead of epidermoid)

UC: undifferenciated carcinoma instead of lymphoepithelial or “indifferencie”

Figure 1.  Distribution of displacements in each direction for the first portal images and after last portal images: (a) cranio-caudal, (b) medio-lateral, (c) anterior-posterior.

Table II.  Set-up errors in CC, ML and AP directions and PTV margins for three models [18–20] and in the three spatial directions

	Overall mean=M (mm)	Systematic SD=Σ (mm)	Random SD=σ (mm)	PTV-margins ICRU (mm)	PTV-margins Stroom (mm)	PTV-margins Van Herk (mm)
Cranio-caudal
1st portal	−2.34	1.20	2.26	5.02	3.98	4.58
After last portal	−1.75	0.95	1.93	4.22	3.25	3.73
Medio-lateral
1st portal	2.00	0.89	1.93	4.17	3.13	3.58
After last portal	1.17	0.80	1.97	4.17	2.98	3.38
Anterior-posterior
1st portal	−1.37	0.93	1.78	3.94	3.11	3.57
After last portal	−1.23	0.84	1.63	3.59	2.82	3.24

Table III.  Overall SDs of the measurements for 5 scenarios: daily portal, every 2, 3, 4 or 5 days. P-values for Levene test for homogeneity of SDs

N=567	Daily	2 days	3 days	4 days	5 days
Cranio-caudal (mm)	2.12	2.32 (p=0.10)	2.42 (p=0.016)	2.43 (p=0.01)	2.46 (p=0.007)
Medio-lateral (mm)	2.18	2.24 (p=0.67)	2.21 (p=0.83)	2.23 (p=0.73)	2.26 (p=0.61)
Anterior-posterior (mm)	1.78	1.88 (p=0.40)	1.91 (p=0.30)	1.92 (p=0.24)	1.92 (p=0.24)