Practical dose delivery verification of craniospinal IMRT
Bibliographic record
Abstract
Craniospinal irradiation (CSI) using IMRT allows dose sparing to organs-at-risk (OAR) whilst conforming the dose to the target volume. Due to the complexity of treatment involving several isocenters, the dose distribution created by the inverse-planned segmented fields must be verified prior to treatment. We propose and test methods to verify dose delivery using commonly available dosimetry equipment for commissioning and routine patient-specific dose verification of craniospinal IMRT. Ten patients treated with conventional CSI were retrospectively planned with a 3-isocenter (cranial, upper spine, and lower spine) IMRT technique. The isocenters were placed 25-27 cm away from each other in the longitudinal direction but in the same lateral and anterioposterior positions. The planning target volume (PTV) was defined as the brain with a 0.5 cm margin and spinal canal with a 1.0 cm margin. The plans were prescribed to 36 Gy in 20 fractions to the PTV mean dose. Eleven beams (five cranial, three upper spine, and three lower spine) were optimized simultaneously. The dose delivered by the IMRT plans was then recalculated on several different phantoms and measured using the following methods: 1) ionization chamber inserted in a cylindrical phantom, positioned in the junction regions between cranial/upper-spine isocenters and upper-/lower-spine isocenters; 2) MapCHECK centered in the overlap regions; and 3) ArcCHECK measurement with beams from each isocenter. For 1) ± 3% dose difference and for 2) and 3) ≥ 95% of measured points with a γ-index < 1 for 3% dose difference and 3 mm distance-to-agreement were deemed clinically acceptable. The median (range) planned to measured dose differences for the ionization chamber is 0.4% (-1.5% to 3.0%) for the cranial/upper-spine field and 1.8% (-0.8% to 2.6%) for the upper-/lower-spine field overlap region. The median (range) percentage of MapCHECK diodes with a γ index < 1 for 3%/3 mm criterion is 98.0% (95.3% to 99.7%) for the cranial/upper-spine and 97.3% (95.0% to 99.6%) for the upper-/lower-spine field overlap regions. The median (range) percentage of ArcCHECK diodes with a γ index < 1 for 3%/3 mm criterion is 99.7% (97.1% to 100%). Three different methods of verifying craniospinal IMRT were compared and tested. All techniques offer different benefits and together can be used for 1) commissioning the treatment technique and, separately, for 2) patient-specific pretreatment verification measurements.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".