A practical approach to estimating optic disc dose and macula dose without treatment planning in ocular brachytherapy using 125I COMS plaques

Table 1 The comparison of central-axis dose values (in Gy) for a 16 mm COMS plaque loaded with ¹²⁵I seeds (model 6711) calculated in our in-house program with those in three commercial treatment planning systems (TPS) in Rivard et al.’s study

d (mm)	CAX points	Current Study	Data from Table II in Rivard et al. [15]			Max\( \left\|{\mathrm{D}}_{\mathrm{diff}}^{\mathrm{Rel}}\left(\%\right)\right\| \)
d (mm)	CAX points	Current Study	P³	BV	PS
−1.0	Outer sclera	336.18	341	340	339	1.41
0.0	Inner sclera	258.79	261	261	260	0.85
1.0		202.10	203	203	202	0.44
2.0		160.48	161	161	160	0.32
3.0		128.68	129	129	128	0.53
4.0		103.91	104	104	103	0.88
5.0	Rx depth	84.52	84.4	84.5	83.9	0.74
6.0		69.26	69.2	69.2	68.8	0.67
7.0		57.27	57.2	57.2	56.9	0.65
8.0		47.73	47.7	47.7	47.4	0.70
9.0		40.12	40.0	40.0	39.8	0.81
10.0		34.00	33.9	33.9	33.7	0.89
11.3	Eye center	27.73	27.6	27.6	27.5	0.83
15.0		16.45	16.3	16.3	16.3	0.95
20.0		9.02	8.87	8.89	8.84	2.04
22.6	Opposite retina	6.83	6.70	6.70	6.67	2.35

P³, BV and PS represent Pinnacle, BrachyVision and Plaque Simulator, respectively. Dose values were calculated for a prescribed dose of approximately 85 Gy to a central-axis depth of 5 mm (S_k = 4.752 U and irradiation time = 100 h) using a line source approximation of the AAPM TG-43 formalism and homogeneous water phantoms. Max\( \left|{\mathrm{D}}_{\mathrm{diff}}^{\mathrm{Rel}}\left(\%\right)\right| \) is the largest modulus of relative percent differences in dose between the two studies

ISSN: 1748-717X