Table 3.

Interfraction motion in cervix cancer radiotherapy

Ref	Target measured	No of Pts	Imaging modality and Frequency	Method of measurement/ registration	Statistic used	Motion (mm)			Suggested Margins (mm)			Volume change	Bladder/ rectum correlation
						AP	LR	SI	AP	LR	SI
31	Cervix	16	Weekly CT	Cervix COM Cervix contour	Mean max Range Mean max	16 5.1–25 A = 17 p = 18	8.2 4.4–14 L = 9.4 R = 7.6	21 12–33 S = 23 I = 13				Cervix volume reduced by mean 62.3% after 45 Gy	Bladder volume affects AP and SI but not lateral margins
32	Cervix Uterus	20	MR at baseline and weekly x5	Cervical os Uterine canal Uterine fundus Cervical os Uterine canal Uterine fund us	Grand mean Mean range	2.4 4.8 4.6 11.2 13.1 14.5		1.5 5.7 7.8 11.3 15.7 24.4	Isotropic internal margin to encompass 90% of motion was 40 mm at the fundus and 15 mm at the cervix			Significant reduction in bladder volume during RT. No systematic change in rectosigmoid volume.	Bladder volume associated with SI motion of fundus and AP motion of cervical os. Rectal volume associated with SI motion of uterine canal and cervical os.
33	Cervix Uterus Upper vagina	33	MR on 2 days 24 h apart	Post cervix Uterine body Upper vagina	Mean (SD) CTV–PTV margins	2.7 (2.8) 7 (9) 2.6 (3)	0.3 (0.8) 0.8 (1.3) 0.3 (1)	4.1 (4.4) 7.1 (6.8)	15 30 11	7 8	13 25 7		SI uterine motion correlated to bladder filling. AP cervix and vaginal motion related to rectal filling
34	GTV CTV	20	MR at baseline and weekly	GTV CTV	Margin to encompass 95% cases (internal motion)				A = 12 p = 14 A = 24 p = 17	R = 12 L = 11 R = 12 L = 16	S = 4 I = 8 S = 11 I = 8	Significant regression GTV p ≤ 0.001 Mean GTV 57cc week 0, 43.3cc, 32cc and 23cc at weeks 2, 3 and 4	AP shift in GTV and CTV weakly correlated with rectal vol. Significant difference in margins required if pre-treat rectum volume >70 cc.
27	CTV	10	Daily CBCT	COM	Mean SD Range	3 5 −9.4–18.9	−0.28 1.3 +3.3–3.5	−4.6 3.9 −15.3–3.8	Mean margin to encompass CTV motion = 15 mm, but fails in 32% Margins up to 30 mm could be required to ensure coverage in ≥95% fractions.			Mean reduction in CTV of 20% (586.4 to 469cc) Mean bladder volume relative to the planning CT −48.5 cc	Increased rectal and bladder volume associated with significant superior shifts (p < 0.001)
35	Cervix	10	Daily EPID	Cervix fiducials	Mean of mean Random error Internal motion	3.5 3.9	3.7 2.2	4.1 3.7	9.7	10.8	8.9
36	Cervix	15	Portal films weekly	Radiopaque ring	Median Max	16 23	10 24	8 36				50% reduction in tumour size at 30 Gy (21 days)
37	Cervix	10	Daily 2D KVI	Cervix fiducials	Mean SD Max	4.2 3.5 18	1.9 1.9 14	4.1 3.2 18
38	Cervix	10	MVCT daily	Cervix contour Uterus contour 95% margin for internal motion and setup	Mean SD Mean SD	A = 0.4 P=-3 A = 10.1 p = 6.9 A = 3.3 p = 0.3 A = 11.9 p = 11.7	L = −3.5 R = 0.2 L = 4.9 R = 4.5 L = 0.7 R = −0.6 L = 8.1 R = 7.5	S = 2.2 I = 0.5 S = 8 I = 5 S = 6.1 I = 5 S = 11.6 I = 11.2	A = 17 p = 12 A = 19 p = 19	R = 8 L = 9 R = 13 L = 13	S = 15 I = 9 S = 20 I = 19	Significant reduction in mean cervix volume (106 cc pre-treatment to 74 cc last week of treatment)	Average bladder volume reduced from 156 cc in wk1 to 88 cc in the last week (p < 0.01).
39	Cervix	20	MRI baseline and weekly x5	GTV Cervix Uterus Upper vagina	Euclidean vector displacement	1.2 ± 0.4 (0.5–3) 1.1 ± 0.3 (0.5–2.8) 1.7 ± 0.2 (0.5–4.5) 0.7 ± 0.3 (0.3–1.3)			15 mm GTV to PTV margin covered the GTV to >98% of prescription dose			The relative reduction in the GTV from baseline to the end treatment was 48–96%.	Individually, the planned dose was not the same as the simulated delivered dose

COM, centre of mass; CTV, clinical target volume; 2D, two-dimensional; EPID, electronic portal imaging device; GTV, gross tumour volume; KVI, kilovoltage imaging; MVCT, megavoltage CT; PTV, planning target volume; RTP, radiotherapy planning; SD, standard deviation.