Program Information
Assessment of Intra-/Inter-Fractional Internal Tumor and Organ Movement in Radiotherapy of Head and Neck Cancer Using On-Board Cine MRI
H Chen1*, S Dolly1 , J Victoria2 , S Ruan3 , D Low4 , M Anastasio1 , B Fischer-Valuck1 , R Kashani1 , O Green1 , V Rodriguez1 , J Dempsey2 , S Mutic1 , H Gay1 , W Thorstad1 , H Li1 , (1) Washington University School of Medicine, Saint Louis, MO, USA (2) ViewRay Incorporated, Oakwood Village, Ohio, USA (3) University of Rouen, QuantIF - EA 4108 LITIS, Rouen, France (4) University of California Los Angeles, Los Angeles, CA, USA
Presentations
SU-C-210-7 (Sunday, July 12, 2015) 1:00 PM - 1:55 PM Room: 210
Purpose:
Head and neck (H&N) internal organ motion has previously been determined with low frequency and temporary nature based on population-based pre- and post-treatment studies. Using immobilization masks and adding a 4-6 mm planning-tumor-volume margin, geometric uncertainties of patients are routinely considered clinically inconsequential in H&N radiotherapy. Using the first commercially-available MR-IGRT system, we conducted the first quantitative study on inter-patient, intra- and inter-fractional H&N internal motion patterns to evaluate the necessity of individualized asymmetric internal margins.
Methods:
Ninety cine sagittal MR image sequences were acquired during the entire treatment course (6-7 weeks) of three H&N cancer patients using the ViewRay™ MR-IGRT system. The images were 5 mm thick and acquired at 4 frames/per second. One of the patients had a tracheostomy tube. The cross-sectional H&N airway (nasopharynx, oropharynx, and laryngopharynx portions) movement was analyzed comprehensively using in-house developed motion detection software.
Results:
Large inter-patient variations of swallowing frequency (0-11 times/per fraction), swallowing duration (1-3 seconds), and pharyngeal cross-sectional area (238-2516 mm2) were observed. Extensive pharyngeal motion occurred during swallowing, while nonzero and periodic change of airway geometry was observed in resting. For patient 1 with tracheostomy tube replacement, 30.3%, 30.0%, 48.7% and 0.3% of total frames showed ≥ 4 mm displacements in the anterior, posterior, inferior, and superior airway boundaries, respectively; similarly, (5.7%, 0.0%, 0.0%, 0.3%) and (23.3%, 0.0%, 35.7%, 1.7%) occurred for patients 2 and 3. Area overlapping coefficients with respect to the first frame were 76.3+/-6.4%, 90.3+/-0.6%, and 92.3+/-1.2% for the three patients, respectively.
Conclusion:
Both the resting and swallowing motions varied in frequency and amplitude among the patients and across fractions of a patient’s treatment. Patients receiving surgery that alters their respiratory and swallowing behavior can have significant intra-fractional internal motion. Patient-specific organ/tumor motion analysis may yield individualized asymmetric internal margins and improve the therapeutic ratio.
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