Effects of Photodynamic Therapy on the Structural Integrity of Vertebral Bone
Bibliographic record
Abstract
STUDY DESIGN: This study investigates the effects of photodynamic therapy (PDT) on the structural integrity of vertebral bone in healthy rats. OBJECTIVE: To determine the short-term (1 week) and intermediate term (6 weeks) effects of a single PDT treatment on the mechanical and structural properties of vertebral bone. SUMMARY OF BACKGROUND DATA: Spinal metastasis develops in up to one-third of all cancer patients, compromising the mechanical integrity of the spine and thereby increasing the risk of pathologic fractures and spinal cord damage. PDT has recently been adapted to ablate metastatic tumors in the spine in preclinical animal models. However, little is known about the effects of PDT on the structural integrity of vertebral bone. METHODS: A single PDT treatment was administered to healthy Wistar rats at photosensitizer and light doses known to be effective in athymic rats bearing human breast cancer metastases. At both 1 and 6 weeks posttreatment, changes in trabecular architecture, global stiffness and strength of vertebrae were quantified using micro-CT stereological analysis and axial compression testing. RESULTS: At 6 weeks, there was a significant increase in bone volume fraction (to 55.7 +/- 11.1% vs. 38.5 +/- 6.4%, P < 0.001) and decrease in bone surface area-to-volume ratio (16.9 +/- 5.0/mm vs. 22.8 +/- 4.5/mm, P = 0.001), attributed to trabecular thickening (130 +/- 40 microm vs. 90 +/- 20 microm, P < 0.001). Similar trends were found at 1 week after PDT. There was a significant increase in stiffness from control (306 +/- 123 N/mm) at 1 week (399 +/- 150 N/mm, P = 0.04) and 6 weeks (410 +/- 113 N/mm, P = 0.05) post PDT. There was a positive trend toward increased ultimate stress at 1 week, which became statistically significant at 6 weeks compared with control (39.3 +/- 11.3 MPa vs. 27.5 +/- 9.5 MPa control, P = 0.002). CONCLUSION: Not only may PDT be successful in ablating metastatic tumor tissue in the spine, but the positive effects of PDT on bone found in this study suggest that PDT may also improve vertebral mechanical stability.
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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 | 0.000 | 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 | 0.001 |
| 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".