A novel <sup>169</sup>Yb‐based dynamic‐shield intensity modulated brachytherapy delivery system for prostate cancer
Bibliographic record
Abstract
Purpose Intensity modulated brachytherapy (IMBT) is a novel high dose rate brachytherapy (HDR BT) technique which incorporates static or dynamic shielding to increase tumor coverage and/or spare healthy tissues. The purpose of this study is to present a novel delivery system (AIM‐Brachy) design that can enable dynamic‐shield IMBT for prostate cancer. Methods The AIM‐Brachy system dynamically controls the rotation of platinum shields, placed within interstitial catheters, which partially collimate the radiation emitted from an 169 Yb source. Conventional HDR BT (10 Ci 192 Ir) and IMBT (18 Ci 169 Yb) plans were generated for 12 patients using an in‐house column generation‐based optimizer, coupled to a Geant4‐based dose calculation engine, RapidBrachyMC. Treatment plans were normalized to match the same PTV D 90 coverage as the clinical plan. Intershield attenuation effects were taken into account. A sensitivity analysis was performed to evaluate the dosimetric impact of systematic longitudinal source positioning errors ( 1 mm, 2 mm, and 3 mm) and rotational errors ( 5 , 10 and 15 ) on clinically relevant parameters (PTV D 90 and urethra D 10 ). Results The platinum shield reduced the dose rate on the shielded side at 1 cm to 18.1% of the dose rate on the unshielded side. For equal PTV D 90 coverage, the urethral D 10 was reduced by 13.3% 4.7%, without change to other plan quality indices (PTV V 100 , V 150, V 200 , bladder V 75 , rectum V 75 , HI, COIN). Delivery times for HDR BT and IMBT were 9.2 ± 1.6 min and 18.6 ± 4.0 min, respectively. In general, the PTV D 90 was more sensitive to source positioning errors than rotational errors, while the urethral D 10 was more sensitive to rotational errors than source positioning errors. For a typical range of positioning errors ( 1 mm, 5 ), the overall tolerance was <2%. Conclusions The AIM‐Brachy system was proposed to deliver dynamic‐shield IMBT for prostate cancer with the potential to create a low dose tunnel within the urethra. The urethra‐sparing properties are desirable to minimize the occurrence and severity of urethral strictures or, alternatively, to provide a method for dose escalation.
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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) | 0.001 | 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) | 0.000 | 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".