Feasibility of Novel CBCT-Based Online Adaptive Radiotherapy In a Cervical Cancer Patient with a Hip Prosthesis
Abstract
Purpose
When cervical cancer patients with a hip prosthesis undergo standard-CBCT imaging, metal artifacts are present in the image due to the prosthesis high-Z material, leading to potential uncertainty in setup or contouring/dose calculation in oART. With the introduction of HyperSight imaging, metal artifacts are reduced with a metal artifact reconstruction (MAR) algorithm. This work evaluates HyperSight imaging for oART in a cervical cancer patient with a hip prothesis.
Methods
One patient with a left side hip prothesis was previously treated for cervical cancer at our institution with IGRT using HyperSight-CBCT setup imaging. Six evenly spaced CBCTs (Fraction 1, 5, 10, 15, 20, 25) were used to simulate an adaptive session. Partial arcs were used to avoid beams entering through prosthesis. Image quality was assessed using CNR ratio and artifact index. The quality of contours was evaluated using a scoring system to assess auto-contours and the degree of manual edits required, 1 being unacceptable/extensive edits up to 5 being acceptable/no edits.
Results
Across the six HyperSight CBCT’s, mean CNR was 4.56+-0.3 (right) and 3.96+-0.56 (left), with corresponding artifact indices of 22.47HU+-3.4 (right) and 28.68HU+-1.5 (left).For CTV contours, Fraction 1, 5, 10, and 15 required minor to moderate edits and few (1-5% slices) to some edits (6-20% slices) were made, while Fraction 20 and 25 contours were clinically unacceptable, with extensive edits made (>50% of slices). oART was successful for all six fractions, and the adapted plan chosen each fraction. The CTV V98%>=98% was averaged to be 98.73%, over all fractions. The average maximum dose delivered to the rectum, bladder, and bowel bag was 102.78%, 101.12%, and 103.73%, respectively.
Conclusion
This work exhibits the use of HyperSight CBCT images for oART in a cervical cancer patient with a hip prosthesis. HyperSight images show promise for reliable contouring and accurate dose calculation.