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Automatic Catheter Reconstruction of Flap Applicators in MRI-Guided HDR Surface Brachytherapy

I Buzurovic*, E Kaza, D O'Farrell, T Harris, S Friesen, P Devlin, R Cormack, Brigham and Women's Hospital, Harvard Medical School, Boston, MA

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Catheter reconstruction is crucial for the accurate delivery of radiation dose in HDR brachytherapy. The process becomes complicated and time-consuming for large superficial clinical targets with complex topology. A novel method for the automatic catheter reconstruction (ACR) using MRI-only is proposed.

Methods: We have developed an optimized clinical pointwise encoding time reduction with radial acquisition MRI sequence capable of MRI-only catheter localization in HDR brachytherapy following the ACR of flap applicators(FA). This technical solution has been incorporated to the in-house developed brachytherapy treatment planning system. The workflow for ACR is: a)an anchor point is placed in 3D or in the axial view of the first MRI at the tip of the first, last and middle points for the curved surface; b)similar points are placed on the last slice of the image set; c)the surface detection algorithm automatically registers the points to the images and applies the surface reconstruction filter; d) a structured grid surface is generated through the center of the treatment catheters placed at a distance of 5mm from the patient's skin. Then, a mesh-style plane is generated with the reconstructed catheters placed 10mm apart. To demonstrate ACR, we used MRI of forearm with flap applicator. The coordinates for each catheter were generated and compared to the control points (CP) generated during manual standard reconstruction for 16 catheters and 384 CP.

Results: The variation of catheter tip positions between the automatically and manually reconstructed catheters was 0.11mm (SD=0.33mm). The position difference between the manually selected catheter CP and the corresponding points obtained automatically was 0.12mm(SD=0.25mm), 0.13mm(SD=0.32mm), and 0.14mm(SD=0.28mm) in x, y and z-directions, respectively.

Conclusion: This study shows feasibility of MRI-only ACR with a high level of positioning accuracy. Implementation of this technique has potential to improve visibility of the clinical targets and to reduce treatment planning time.

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