Table 2 Details of hydrogel spacer shrinkage and its effects on external-beam radiation therapy planning
Days after hydrogel injection | Hydrogel spacer | PTV dose (Gy) | Irradiated rectum volume (cc)a | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Distance (mm) | Volume (cc) | Mean | Maximum | Minimum | V100 | V90 | V80 | V70 | V60 | |||
Case 1 | Baseline | 1 | 22.1 | 15.0 | ||||||||
Planning of EBRT | 28 | 19.9 | 14.4 | 45.2 | 48.2 | 32.2 | 0 | 1.0 | 1.5 | 2.0 | 3.2 | |
Evaluation during EBRT | 76 | 20.7 | 11.4 | 45.2 | 48.2 | 32.2 | 0.2 | 1.5 | 2.6 | 3.5 | 4.6 | |
Case 2 | Baseline | 1 | 11.4 | 17.4 | ||||||||
Planning of EBRT | 47 | 6.5 | 12.9 | 45.2 | 47.9 | 36.1 | 0.1 | 3.0 | 5.5 | 7.0 | 8.7 | |
Evaluation during EBRT | 93 | 0.6 | 2.0 | 45.1 | 47.9 | 36.1 | 3.6 | 7.1 | 8.8 | 10.1 | 11.7 | |
Case 3 | Baseline | 1 | 14.5 | 10.9 | ||||||||
Planning of EBRT | 41 | 13.6 | 9.4 | 45.1 | 47.5 | 37.7 | 0 | 1.1 | 2.5 | 4.1 | 6.0 | |
Evaluation during EBRT | 74 | 11.8 | 7.1 | 45.2 | 47.5 | 37.7 | 0.4 | 3.1 | 4.6 | 5.7 | 7.1 | |
Case 4 | Baseline | 1 | 15.0 | 17.7 | ||||||||
Planning of EBRT | 47 | 15.0 | 15.8 | 45.0 | 47.5 | 39.6 | 0 | 0 | 0.1 | 0.3 | 0.6 | |
Evaluation during EBRT | 83 | 10.5 | 11.4 | 45.0 | 47.5 | 39.6 | 0 | 0 | 0.4 | 2.2 | 3.6 | |
Second evaluation during EBRT | 99 | 4.1 | 4.5 | 45.0 | 47.5 | 39.6 | 0.9 | 2.3 | 3.2 | 4.1 | 5.0 | |