# Dosimetry study of 3D-printed noncoplanar template-assisted CT-guided 125I seed implantation for the treatment of recurrent and metastatic tumors in the head and neck

## TL;DR

This study shows that a 3D-printed template helps deliver consistent radiation doses to hard-to-treat head and neck tumors, improving treatment accuracy.

## Contribution

The study demonstrates the clinical feasibility and dosimetric accuracy of 3D-printed noncoplanar template-assisted iodine-125 seed implantation.

## Key findings

- Pre- and postoperative dosimetric parameters showed no significant differences, indicating accurate dose delivery.
- Bland–Altman analysis confirmed high agreement in key dosimetric metrics.
- The technique may improve local tumor control while reducing radiation exposure to nearby critical structures.

## Abstract

Recurrent and metastatic tumors of the head and neck pose significant treatment challenges due to their proximity to critical structures and prior radiation exposure. This study aimed to evaluate the consistency between preoperative and postoperative dosimetric parameters in CT-guided 3D-printed noncoplanar template (3DPNCT)-assisted radioactive iodine-125 seed implantation (RISI).

Twenty-six patients with recurrent or metastatic head and neck cancer were retrospectively analyzed. Gross tumor volume (GTV) coverage and dosimetric parameters such as D90 (dose covering 90% of the GTV), conformity index (CI), and homogeneity index (HI) were compared before and after implantation. The Shapiro-Wilk test was used to assess data normality.

There were no significant differences between pre- and postoperative D90, V100, V150, or CI values (P > 0.05). Bland–Altman analysis showed high agreement for key metrics.

3DPNCT-assisted RISI demonstrated accurate dose delivery and high reproducibility. This approach may enhance local control while minimizing radiation to organs at risk in complex head and neck anatomies. These results suggest that this technique has promising clinical applicability in complex head and neck cases; however, further validation through larger prospective studies is warranted to confirm long-term efficacy and safety.