# Dosimetric Comparison of Deep Inspiration Breath-Hold and Free-Breathing Techniques in Stereotactic Body Radiotherapy for Localized Lung Tumors at a Tertiary Care Center

## TL;DR

This study compares deep inspiration breath-hold and free-breathing techniques in lung cancer radiotherapy, finding that breath-hold reduces radiation exposure to healthy tissue.

## Contribution

The study demonstrates that DIBH improves dosimetric outcomes in lung SBRT by reducing normal tissue exposure.

## Key findings

- DIBH significantly increased lung volume and reduced internal target volume compared to free breathing.
- DIBH reduced mean ipsilateral lung dose by 36.84% and lowered doses to critical organs like the heart and spinal cord.
- Dose conformity improved with DIBH without compromising target coverage or homogeneity.

## Abstract

Background

Respiratory motion is a major source of geometric uncertainty in lung stereotactic body radiotherapy (SBRT) and may lead to increased irradiation of normal lung tissue and adjacent organs at risk (OARs). Deep inspiration breath-hold (DIBH) is an advanced motion management technique that minimizes tumor motion by immobilizing the target during treatment delivery and increasing lung volume. This study aimed to evaluate the dosimetric advantages of DIBH compared with free breathing (FB) in SBRT for patients with localized lung tumors.

Methods

Twenty patients with localized lung tumors underwent computed tomography (CT) simulation using both four-dimensional CT (4DCT) FB and DIBH techniques. SBRT plans were generated for each dataset using 6 MV flattening filter-free (FFF) beams with two coplanar partial arcs (180°-220° offset), and dose calculation was performed using the anisotropic analytical algorithm (AAA) in the Eclipse treatment planning system. Identical dose constraints and plan normalization to the planning target volume (PTV) mean dose were applied for both techniques. Image guidance was performed using cone-beam CT (CBCT). Dosimetric parameters for lung volumes, target coverage, and OAR doses were extracted from dose-volume histograms (DVHs). Statistical comparisons were carried out using paired t-tests.

Results

DIBH significantly increased lung volumes compared with FB, with mean expansion factors of 1.41 and 1.37 for the ipsilateral and contralateral lungs, respectively, and resulted in a 1.45-fold reduction in internal target volume. The mean ipsilateral lung dose was reduced by 36.84% in DIBH plans (7.48 ± 3.57 Gy) compared with FB plans (10.23 ± 4.58 Gy). Statistically significant reductions were also observed in lung V10, V15, and V20 parameters (p < 0.05). DIBH plans demonstrated improved dose conformity (CI: 1.05 ± 0.08) without significant differences in homogeneity or target coverage indices. In addition, doses to critical OARs including the heart, spinal cord, and chest wall were significantly lower in DIBH-SBRT plans.

Conclusion

DIBH-based SBRT provides significant dosimetric advantages over FB SBRT for localized lung tumors by enhancing target immobilization, increasing lung volume, and reducing radiation exposure to the lungs and surrounding critical organs without compromising target coverage. DIBH is a feasible and effective respiratory motion management strategy in lung SBRT, although appropriate patient selection and training are essential for successful implementation.