Positron emission tomography-guided radiation therapy: An overview of the RefleXion SCINTIX biology-guided platform

To present an introduction and overview of the RefleXion™ X1 system using SCINTIX, a radiation therapy platform guided by positron emission tomography (PET) designed for biology-guided radiation therapy (BgRT).

The RefleXion X1 system integrates a 6 MV flattening-filter-free linear accelerator, onboard kilovoltage computed tomography (kVCT), and dual PET arcs. The system enables both conventional kVCT-based image-guided radiation therapy (IGRT) and PET-guided treatment with SCINTIX. Compared to the conventional IGRT radiation treatment, the SCINTIX workflow includes a planning PET session prior to treatment planning and a PET pre-scan before each fraction. Fluorodeoxyglucose (FDG) was used as the PET tracer. An activity concentration (AC) ≥5 kBq/ml) and normalized target signal (NTS) ≥2.7 for planning PET session and an NTS ≥2.0 for treatment) are evaluated to decide whether the patient is eligible to treat with the SCINTIX.

The RefleXion X1 with SCINTIX treatment system was successfully installed for PET-guided radiation therapy. Detailed SCINTIX and SBRT/IGRT treatment workflows are described. SCINTIX-related shielding design, including uptake room specifications, is presented. Representative clinical cases include lung and rib lesions treated with SCINTIX, and a liver case treated with SBRT.

SCINTIX enables PET-guided radiation therapy, offering a novel approach for BgRT. The integration of high-resolution kVCT further supports conventional IGRT workflows. Initial clinical experience demonstrates feasibility, accuracy, and potential for expanded adoption in personalized radiation therapy.