Feasibility of external beam radiation therapy to deep‐seated targets with kilovoltage x‐rays
Bibliographic record
Abstract
Purpose Radiation therapy to deep‐seated targets is typically delivered with megavoltage x‐ray beams generated by medical linear accelerators or 60 Co sources. Here, we used computer simulations to design and optimize a lower energy kilovoltage x‐ray source generating acceptable dose distributions to a deep‐seated target. Methods The kilovoltage arc therapy ( KVAT ) x‐ray source was designed to treat a 4‐cm diameter target located at a 10‐cm depth in a 40‐cm diameter homogeneous cylindrical phantom. These parameters were chosen as an example of a clinical scenario for testing the performance of the kilovoltage source. A Monte Carlo ( MC ) model of the source was built in the EGS nrc/ BEAM nrc code and source parameters, such as beam energy, tungsten anode thickness, beam filtration, number of collimator holes, collimator hole size and thickness, and source extent were varied. Dose to the phantom was calculated in the EGS nrc/ DOSXYZ nrc code for varying treatment parameters, such as the source‐to‐axis distance and the treatment arc angle. The quality of dose distributions was quantified by means of target‐to‐skin ratio and dose output expressed in D 50 (50% isodose line) for a 30‐min irradiation in the homogeneous phantom as well as a lung phantom. Additionally, a patient KVAT dose distribution to a left pararenal lesion (~1.6 cm in diameter) was calculated and compared to a 15 MV volumetric modulated arc therapy ( VMAT ) plan. Results In the design of the KVAT x‐ray source, the beam energy, beam filtration, collimator hole size, source‐to‐isocenter distance, and treatment arc had the largest effect on the source output and the quality of dose distributions. For the 4‐cm target at 10‐cm depth, the optimized KVAT dose distribution generated a conformal plan with target‐to‐skin ratio of 5.1 and D 50 in 30 min of 24.1 Gy in the homogeneous phantom. In the lung phantom, a target‐to‐skin ratio of 7.5 and D 50 in 30 min of 25.3 Gy were achieved. High dose conformity of the 200 kV KVAT left pararenal plan was comparable to the 15 MV VMAT plan. The volume irradiated to at least 10% (<240 cG y) of the prescription dose was 2.2 × larger in the 200 kV KVAT plan than in the 15 MV VMAT plan, but considered clinically insignificant. Conclusions This study demonstrated that conformal treatments of deep‐seated targets were achievable with kilovoltage x‐rays with dose distributions comparable to MV beams. However, due to the larger volumes irradiated to clinically tolerated low doses, KVAT x‐ray source usage for deep‐seated lesions will be further evaluated to determine optimal target size.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 teacher head, 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".