3 years ago

Comparison between CT- and MRI-derived head and neck cancer target volumes using an integrated MRI-tri- 60 Co teletherapy device

Ali R. Sepahdari, Minsong Cao, Argin G. Mikaielian, Allen M. Chen, Govind Raghavan

Abstract

Purpose

Radiation treatment planning is typically based on the identification of a gross tumor volume (GTV) using computed tomography (CT). The clinical implementation of an integrated MRI-radiation therapy delivery unit allows for a strict comparison of CT- and MRI-derived GTVs for head and neck cancer.

Materials and methods

Twenty-six consecutive patients with squamous cell carcinoma of the head and neck were selected and planned for intensity-modulated radiotherapy (IMRT) on a novel tri-60Co teletherapy system equipped with a 0.35 T MRI (ViewRay Incorporated, Oakwood Village, OH). All patients had measurable disease. Pre-treatment MRIs were imported into a contouring interface where the primary GTV were assessed and compared to those obtained from a registered CT with the patient in the identical position and immobilization apparatus.

Results

The median GTV as derived from the CT and MRI was 27.2 cm3 (range 3.8 to 155.0 cm3) and 34.9 cm3 (range, 5.0 to 189.5 cm3), respectively (p = 0.01). The MRI-derived GTV was larger than the CT-derived GTV in 21 of the 26 cases and was smaller in the remaining 5 cases. Among the 21 cases where the MRI-derived GTV was larger, the median difference in absolute GTV per individual patient was 6.9 cm3 (range 2.1 to 33.4 cm3), representing a 25% difference on average. The median concordance index for patients with de novo versus recurrent disease was 0.83 and 0.66, respectively (p = 0.03).

Conclusion

Significant differences in GTV extent were noted between MRI- and CT-derived ViewRay images. The implications for treatment planning are discussed.

Publisher URL: https://link.springer.com/article/10.1007/s13566-017-0337-0

DOI: 10.1007/s13566-017-0337-0

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