A study of image-guided radiotherapy of bladder cancer based on lipiodol injection in the bladder wall

Figures & data

Table I. Lipiodol and bladder measures.

Patient no.	No. of Lipiodol injections	No. of Lipiodol spots visible*	Site of the tumor-bed	Bladder volume (cm^3) on planning CT	Mean bladder volume (cm^3) on CBCT (SD)	Bladder filling (cm^3)^† (SD)
1	5	4	posterior wall	158.5	88.7 (7.9)	20.4 (14.5)
2	5	1	left wall	129.9	81.8 (13.9)	33.8 (2.0)
3	6	5	left wall	76.2	100.4 (19.9)	25.4 (13.4)
4	5	3	left wall	136.3	166.5 (19.5)	12.8 (5.0)
5	7	6	right wall	176.6	154.8 (36.1)	21.3 (16.6)

*Number of Lipiodol spots visible on CT and CBCT for the entire treatment course. ^†Bladder filling was calculated from the difference between bladder volumes on post- vs. pre-treatment CBCT.

Abbreviation: SD = Standard deviation.

Figure 1. Cystoscopy image of a Lipiodol injection in the bladder mucosa. The tip of the injection needle is in the centre of the picture with the tumor to the right and a formation of an injection papule to the left (white circle).

Figure 2. The washout of the relative Lipiodol volume during the full radiotherapy course for patients 1 (closed circle), 3 (open circle), 4 (closed triangle) and 5 (open triangle). The Lipiodol volumes were defined on the daily CBCT scans by a fixed HU of 200–2500 confined to the bladder structure.

Figure 3. Difference between match on bony anatomy and the Lipiodol spots for patient 3. Left-right (closed circle), Cranial-caudal (open circle) and Anterior-posterior (open triangle). A: Inter-fractional shifts for the full course of RT. B: Intra-fractional shifts the first five fractions.

Table II. Inter-fractional translational shifts after offline CBCT match on the Lipiodol spots.

			Mean shift from bony match to off-line match on the Lipiodol spots (mm), SD				Number of shifts more than or equal to 5 mm (%)
Patient no.	CBCT	Automatch (%)	LR	CC	AP	3D, range	LR	CC	AP	3D
1	28	28 (100)	2 (1)	−4 (3)	2 (3)	6 (0–13)	2 (11)	17 (61)	6 (18)	24 (86)
2
3	27	23 (85)	2 (2)	−1 (4)	−3 (7)	7 (1–18)	1 (4)	7 (26)	12 (44)	17 (63)
4	29	29 (100)	−1 (1)	−1 (2)	−1 (2)	3 (1–8)	0	2 (7)	1 (3)	6 (21)
5	30	30 (100)	2 (2)	−3 (3)	1 (2)	5 (0–12)	4 (13)	10 (33)	2 (7)	14 (47)
All	114	110 (96)	1 (2)	−2 (3)	0 (4)	5 (0–18)	7 (6)	36 (32)	21 (18)	61 (54)

Abbreviations: CBCT = Cone-beam computer tomography, LR=Left-right, CC=Cranial-caudal, AP=Anterior-posterior, 3D=Geometric distance of Lipiodol shift SD=Standard deviation.

Table III. Intra-fractional translational shifts after offline post-RT CBCT match on the Lipiodol spots.

	Mean shift in Lipiodol spots from pre- to post-treatment CBCT (mm), SD
Patient no.	LR	CC	AP	3D, range
1	−1 (1)	−1 (3)	−3 (4)	5 (3–6)
2
3	−1 (2)	0 (2)	−1 (3)	3 (3–4)
4	0 (0.4)	−1 (1)	−1 (1)	2 (1–3)
5	0 (1)	−1 (2)	1 (2)	3 (1–4)
All	−0.3 (1)	−1 (2)	−1 (3)	3 (1–6)

Abbreviations: CBCT=Cone-beam computer tomography, LR=Left-right, CC=Cranial caudal, AP=Anterior-posterior, 3D=Geometric distance of Lipiodol shift SD=Standard deviation.