May i know Sir from your experience, what are the most effective strategies for managing intrafraction motion during SBRT, particularly in spine and lung cases?
From our experience at UZ Brussel, intrafraction motion management in SBRT is highly site-specific, and spine and lung should really be approached differently.
For spine SBRT, the priority is maintaining very small PTV–PRV margins, so precision is key. This can be achieved either through more rigid immobilization (e.g. vacuum cushions/body casts) combined with CBCT and mid-treatment verification, or through a less rigid setup with strong image guidance. In our practice, we favor stereoscopic X-ray–based positioning (e.g. ExacTrac Dynamic), optionally combined with CBCT, and continuous intrafraction monitoring. SGRT can be helpful to assess patient behavior, but IGRT remains essential for the required level of accuracy.
For lung SBRT, the strategy is primarily driven by respiratory motion amplitude. For smaller motion (<1 cm), an ITV-based approach with CBCT verification is generally sufficient. For larger amplitudes, motion management becomes necessary, such as gating or breath-hold techniques. We have good experience with DIBH, as it stabilizes the target and improves reproducibility. We are also exploring the use of surrogate DRRs in combination with stereoscopic X-rays for positioning, together with DIBH CBCT for verification. Ultimately, intrafraction monitoring remains key to manage possible drifts: upcoming ETD developments will allow this with X-rays in near real-time, while currently mid-treatment CBCT or kV imaging during delivery can already be used.
Across both indications, the key aspect is intrafraction monitoring to detect and manage drift, using approaches such as mid-treatment imaging or, increasingly, real-time X-ray–based monitoring.
Thank you for your expert guidance Sir. Your insights were extremely valuable and will directly help me refine my clinical approach. Grateful for your time and support.
From our experience at UZ Brussel, intrafraction motion management in SBRT is highly site-specific, and spine and lung should really be approached differently.
For spine SBRT, the priority is maintaining very small PTV–PRV margins, so precision is key. This can be achieved either through more rigid immobilization (e.g. vacuum cushions/body casts) combined with CBCT and mid-treatment verification, or through a less rigid setup with strong image guidance. In our practice, we favor stereoscopic X-ray–based positioning (e.g. ExacTrac Dynamic), optionally combined with CBCT, and continuous intrafraction monitoring. SGRT can be helpful to assess patient behavior, but IGRT remains essential for the required level of accuracy.
For lung SBRT, the strategy is primarily driven by respiratory motion amplitude. For smaller motion (<1 cm), an ITV-based approach with CBCT verification is generally sufficient. For larger amplitudes, motion management becomes necessary, such as gating or breath-hold techniques. We have good experience with DIBH, as it stabilizes the target and improves reproducibility. We are also exploring the use of surrogate DRRs in combination with stereoscopic X-rays for positioning, together with DIBH CBCT for verification. Ultimately, intrafraction monitoring remains key to manage possible drifts: upcoming ETD developments will allow this with X-rays in near real-time, while currently mid-treatment CBCT or kV imaging during delivery can already be used.
Across both indications, the key aspect is intrafraction monitoring to detect and manage drift, using approaches such as mid-treatment imaging or, increasingly, real-time X-ray–based monitoring.
Thank you for your expert guidance Sir. Your insights were extremely valuable and will directly help me refine my clinical approach. Grateful for your time and support.