Tumor Motion Management in Radiotherapy Using 4D-MRI
Condition: Cancer
Study type: Observational

Summary: 
      The main goal of this research is to characterize patient-specific respiration-induced tumor
      and surrogate motion to evaluate the accuracy and effectiveness of the surrogate-based motion
      management strategies currently used in clinics. Specifically, the investigators hypothesize
      that dynamic MRI (Magnetic Resonance Imaging) obtained over a temporal duration consistent
      with radiotherapy treatments will provide spatio-temporal information of both the tumor and
      surrogate, and therefore can serve as a means to assess the quality of the tumor motion
      tracking with the surrogate. To test this hypothesis, the investigators specifically propose
      to 1) track and characterize the tumor and surrogate motion with 4D (4 dimensional)-MRI and
      2) evaluate surrogate-based motion tracking in a cohort of patients with thoracic tumors.

      External and internal surrogate-based strategies commonly used in clinics have not been
      appropriately validated. With the increasing adaptation of these surrogate methods for motion
      management, the proposed research addresses these urgent issues in clinical radiotherapy
      while providing a means to achieve patient-specific motion management.
    

Detailed description: 
      Respiration-induced patient motion has become a major obstacle for achieving high-precision
      radiotherapy of cancers especially in the thorax and upper abdomen. As the target is
      continuously moving, an additional margin has to be added to the clinical target volume to
      compensate for the uncertainty in the tumor and organ motion, causing toxicity to the normal
      tissue and limiting the dose delivered to the target. To account for the tumor motion,
      surrogate tracking methods are commonly used in clinics during radiotherapy. However, the
      relationship between the surrogate and tumor motion is hard to generalize as it depends on
      individual patients, tumor location, treatment fractions, and sometimes shows complex
      patterns or transient, unpredictable changes. Hence, there is an urgent need to better
      scrutinize the current surrogate-based motion management strategies. Moreover, the most
      robust motion management strategy for the given patient should be determined in the
      pre-treatment setting but the investigators currently lack a sufficient tool to provide this
      information.

      4D-CT is typically used to characterize the tumor motion over the course of the radiotherapy.
      However, 4D-CT is an oversimplified snapshot representation of a single-breathing cycle with
      low soft tissue contrast while imparting a considerable amount of radiation dose to the
      patient. Consequently, the limitations of 4D-CT prevent applicability in acquiring
      information over timescales that represent a treatment session. MRI is highly advantageous as
      it is non-ionizing and provides excellent soft tissue contrast. Although real-time 3D dynamic
      MRI is limited by low image quality and temporal resolution, 2D dynamic MRI techniques have
      high fidelity and spatio-temporal resolution requisite for real-time tracking of the moving
      target. Furthermore, a respiration-correlated 4D-MRI can be reconstructed from multi-slice 2D
      dynamic MR images, enabling volumetric image processing and analysis. Therefore, 4D-MRI is an
      attractive solution to address breathing motion and tumor tracking obstacles in radiotherapy.

      The main goal of this research is to characterize patient-specific respiration-induced tumor
      and surrogate motion to evaluate the accuracy and effectiveness of the surrogate-based motion
      management strategies currently used in clinics. Specifically, the investigators hypothesize
      that dynamic MRI obtained over a temporal duration consistent with radiotherapy treatments
      will provide spatio-temporal information of both the tumor and surrogate, and therefore can
      serve as a means to assess the quality of the tumor motion tracking with the surrogate. To
      test their hypothesis, the investigators specifically propose to 1) track and characterize
      the tumor and surrogate motion with 4D-MRI and 2) evaluate surrogate-based motion tracking in
      a cohort of patients with thoracic tumors.

      External and internal surrogate-based strategies commonly used in clinics have not been
      appropriately validated. With the increasing adaptation of these surrogate methods for motion
      management, the proposed research addresses these urgent issues in clinical radiotherapy
      while providing a means to achieve patient-specific motion management.
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Patients with cancer being treated with radiotherapy
      
Keywords: cancer; radiotherapy; 4D-MRI; 4D-CT; MRI