Author: Muhammad Uzair Memon, Syed Ashar Amjad, Syeda Aisha Arooj, Hafsa Zameer
Affiliation: Dow University of Health Sciences
Background:
Tumor motion during radiotherapy compromises precision and normal tissue sparing. Magnetic Resonance Linear Accelerator (MR-Linac) systems combine MRI with radiation delivery, enabling real-time visualization and adaptive planning.
Objective:
To evaluate the feasibility and clinical benefits of real-time MRI-guided tumor tracking using MR-Linac in Pakistan.
Methods:
From October 2024 to May 2025, 40 patientswith lung, prostate, breast, and pelvic tumors were treated using MR-Linac at Dow University of Health Sciences Karachi. Continuous MRI monitored target motion during beam delivery. Online plan adaptation was performed when displacement exceeded defined thresholds. Setup time, motion magnitude, adaptation frequency, and acute toxicity were analyzed.
Results:
Real-time MRI provided continuous visualization in all patients. Mean intrafraction displacement was 3.2 mm, allowing accurate gating and reduced margins. Adaptive planning was applied in 35% of fractions, reducing dose to nearby organs. All treatments were completed without major interruptions, and no ≥Grade 2 acute toxicities were observed.
Conclusion:
MR-Linac enabled precise real-time tumor tracking and adaptive planning, improving treatment accuracy and safety. This represents one of the first clinical experiences of MRI-guided radiotherapy in Pakistan, demonstrating its feasibility and clinical value.