Development of an integral system test for image‐guided radiotherapy
Bibliographic record
Abstract
An integral system test was developed to determine the precision and accuracy of an image-guided radiotherapy system involving an x-ray volumetric imaging device mounted onto the gantry of a medical linear accelerator. The test was designed to interrogate the system components as a whole without deconstructing the individual sources of error. The integral system test was based on the imaging of an unambiguous stationary object in the treatment position and so took no account of patient related errors. An array of micromosfets interspersed within slices of a tissue equivalent phantom was developed as an imaging test object. It has previously been demonstrated that micromosfets have a very small active volume, are clearly visible on CT images, and produce no significant artifacts. In addition, the active volume of the micromosfets can be accurately inferred radiographically via the use of x-ray volumetric imaging. X-ray volumetric imaging was performed with the object in the treatment position, then reconstructed and transferred to a treatment planning system. With the phantom remaining undisturbed in the treatment position a series of treatment fields were designed to produce a series of fields with the leaf edge sweeping across active volume of the micromosfets. The fields were delivered with a micro-MLC to dosimetrically verify the position of the mosfets and compare with dose values produced by the treatment planning system. It was demonstrated that the systematic gantry flex could be accounted for by the imaging and delivery systems. For the delivery system small changes in leaf positions of the micro-MLC were required to account for gantry flex. The position of the micromosfets determined by the 50% dose position was on average (0.15+/-0.13) mm away from the position determined radiographically for the x and y axes, and (1.0+/-0.14) mm for the z axis. This implies that a margin of approximately 0.2 mm in the axial plane and 1.0 mm in the superior-inferior plane would be required at the delineation stage to ensure coverage of a tumor volume to account purely for imprecision in the image-guided radiotherapy system. The integral system test demonstrated that the image-guided radiotherapy system is capable, in the absence of patient motion, of imaging an object in the treatment position and delivering dose to that object with submillimeter accuracy.
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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 | 0.004 | 0.018 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.003 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".