Erratum: “A simplified approach to characterizing a kilovoltage source spectrum for accurate dose computation” [Med. Phys. 39(6), 3041–3050 (2012)]
Bibliographic record
Abstract
We would like to draw your attention to a small error that we recently discovered in our published paper1 describing the validation of a kV spectral characterization method. Equation (2) in the paper was used to convert dose-to-water to dose-to-medium in bone and lung-equivalent materials at a depth of 4–6 cm. However, this equation, taken from the AAPM's TG-61 (Ref. 2) report outlining dosimetry protocols in the kV energy range, was meant only for surface dose conversions. At a depth of 4 cm, the conversion of dose-to-water to dose-to-bone should consist simply of the ratio of mass-energy absorption coefficients , and not include the bone-to-water backscatter factor ratio (Bmed/Bw). This error affects the measured point in bone-equivalent material depicted in Fig. 9 below by decreasing the agreement in local dose from ≤3% to ≤6%. The measured points in lung-equivalent materials were unaffected because the backscatter factor ratio was used only for the bone slab comparison. While the agreement of ≤6% is larger than previously reported, it remains within experimental uncertainty. As the uncertainty in the position of the ionization chamber is within half of an in-slice side length of a voxel (±0.4 mm), and the local dose gradient is ≥7%/mm at the measurement point, there is a ∼5% uncertainty in local dose due solely to the position of ionization chamber. Furthermore, additional uncertainties arise from ionization chamber response (2.4%, Sec. II.D) and the proposed beam characterization method (1%, Sec. III.A). If we add these in quadrature, we obtain an experimental uncertainty of 5.5%, placing all corrected measurements within experimental uncertainty of the computed doses. It should be noted that the corrected results for the bone slab do not detract from the conclusions of the paper, as they still provide validation of the computed doses within experimental uncertainty. Percent depth dose for the heterogeneous phantom at (a) the center of the 125 kVp beam. The dose was normalized to a depth of 2 cm. Computed dose (line) is compared to the measured relative dose (circles).
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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 | 0.020 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.002 | 0.002 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.003 | 0.002 |
| Research integrity | 0.004 | 0.007 |
| Insufficient payload (model declined to judge) | 0.035 | 0.037 |
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".