Tomotherapy-based stereotactic radiosurgery and stereotactic body radiation therapy

Tomotherapy is an advanced form of intensity modulated radiation therapy that integrates helical radiation delivery and image-guided radiation therapy into a single platform. Utilizing a rotating linear accelerator combined with megavoltage computed tomography imaging, tomotherapy delivers highly conformal radiation doses to tumors while minimizing exposure to surrounding healthy tissue. This article reviews the technical principles and recent developments in helical tomotherapy (HT) and explores its clinical implementations in stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT). For brain SRS, HT shows similar target conformality as dedicated SRS platforms like Gamma Knife (GK) or CyberKnife (CK), but HT has slightly larger low isodose volumes. These factors should be considered depending on patient and disease characteristics, especially for SRS and SBRT treatments. For spine, lung, and prostate SBRT, HT demonstrates comparable performance to other modalities such as CK and volumetric modulated arc therapy, especially when enhanced with new features such as dynamic jaw technology (TomoEDGE) and real-time motion tracking (Synchrony). Although HT provides excellent tumor coverage and precise dose delivery, it is limited by treatment time and restricted beam angle flexibility due to the absence of couch rotation. Recent advancements in the latest HT system (Radixact), including higher dose rates, kilovoltage CT imaging, real-time motion tracking and correction, have significantly enhanced treatment efficiency and accuracy. These innovations establish tomotherapy as a competitive modality in the field of high precision radiotherapy such as SRS and SBRT.