Introduction
Materials and methods
Per protocol | Minor deviation | Major deviation | |
---|---|---|---|
Protocol definitions | |||
Target volume | |||
CSI (distance from field edge to CTV) | |||
Cribriform plate | ≥5 mm | 3 to <5 mm | <3 mm |
All other regions | ≥10 mm | 5 to <10 mm | <5 mm |
Dose uniformity | |||
V95% | ≥95% | ≥90 to <95% | <90% |
V107% | ≤5% | >5% to <10% | ≥10% |
Additional definitions by the reference center | |||
Target volume delineation | |||
CTV/PTV | Entire subarachnoid space encompassed by PTV and CTV | Entire subarachnoid space not encompassed by CTV but by PTV | Entire subarachnoid space not encompassed by CTV and PTV |
Results
Per protocol | Acceptable deviation | Unacceptable deviation | Total | |
---|---|---|---|---|
Correct target and dose | 27 | 0 | 0 | 27 |
Correct target but deviation dose uniformity | 0 | 7 dose minor 3 dose major 4 | 1 dose minor 1 | 8 |
Deviation target but correct dose uniformity | 0 | 3 target minor 3 | 9 target minor 6 target major 3 | 12 |
Deviation target and dose uniformity | 0 | 2 target minor 2 dose major 2 | 20 target minor 12 target major 8 dose minor 5 dose major 15 | 22 |
Total | 27 | 12 | 30 | 69 |
Discussion
Observed deviations
CTV/PTV delineation
Dose uniformity and regional dose distribution
New QC criteria
Acceptable deviation | Unacceptable deviation | |
---|---|---|
Target volume delineation | ||
CTV/PTV | Entire subarachnoid spacea not encompassed by CTV but by PTV or PTV larger than necessary (≤0.5 cm areas with effect on OAR doseb ≤1.0 cm areas without effect on OAR doseb) | Entire subarachnoid spacea not encompassed by CTV and PTV or PTV substantially larger than necessary (>0.5 cm areas with effect on OAR doseb >1.0 cm areas without effect on OAR doseb) |
Circumscribed regional dose coverage at critical locations (cribriform plate, temporal lobes, skull base foramina, thecal sac) | ||
95%-isodose | Not defined | Does not encompass entire subarachnoid spacea |
Vertebral dose in children before end of pubertal acceleration phase | ||
Anterior-posterior dose gradient | Not defined | >5 Gy or 70%c |
Dose uniformity | ||
V95% | ≥95 to <98% | <95% |
V107% | >5% to <10% | ≥10% |
Final result of RT-QC | ||
Per protocol | ||
Acceptable deviation (in individual cases, when missing part of target volume is covered by dose due to radiation technique, final result can be acceptable deviation even in case of unacceptable target volume deviation) | ||
Unacceptable deviation |