TABLE 2.
Dosimetric Data
| Variable | Mean, SD (range) |
|---|---|
| Target volume (mL) | 0.9 ± 1.3 (0.005-7.8) |
| Prescription isodose volume (mL) | 1.1 ± 1.4 (0.015-8.5) |
| Physical dose (marginal dose, Gy) | 12 Gy in 210 (97.7%) cases; 11 Gy in 5 (2.3%) cases |
| Coverage (%) | 98.5 ± 1.3 (93.8-100) |
| Paddick index | 0.74 ± 0.1 (0.28-1.42) |
| Gradient index (units) | 3.1 ± 0.7 (2.2-7.9) |
| RDR (Gy/min) | 2.8 ± 0.6 (1.7-3.8) |
| No. of isocenters (units) | |
| Corresponding to the tumor | 8.9 ± 7.1 (1-32) |
| Corresponding to the internal acoustic meatus | Mean 2.5, median 2 (1-9) |
| Time (min) | |
| Beam-on time | 36.3 ± 18.1 (7.3-101.8) |
| Treatment time | 38.8 ± 18.5 (9-106) |
| Treatment time minus couch-in and couch-out | 37.9 ± 18 (8.9-102.8) |
| Couch-in and couch-out (together) | 0.9 ± 0.7 (0.1-3.2) |
| Beam-on time corresponding to isocenters in the IAM | 16.9 ± 8.9 (2.44-56.2) |
| Mean dose to the cochlea | 2.9 ± 0.8 (0.6-6.6) |
| BED corresponding to the mean dose to the cochlea (Gy2.47) | 5.8 ± 2.5 (0.71-21.27) |
| Maximal dose to the cochlea | 4.2 ± 1.4 (1.5-10.4) |
| BED corresponding to the maximal dose to the cochlea (Gy2.47) | 10.6 ± 6 (2.2-46.9) |
| Integral dose | |
| VS (tumor) | 14.7 ± 21 (0.1-116.7) |
| IAM (all volume) | 2 ± 1 (0.6-6.3) |
BED, biologically effective dose; IAM, internal auditory meatus; RDR, radiation dose rate; VS, vestibular schwannoma.