The use of trans-applicator intracavitary ultrasonography in brachytherapy for cervical cancer: phantom study of a novel approach to 3D image-guided brachytherapy

Abstract

PurposeTo assess the feasibility of applying trans-applicator intracavitary ultrasonography to image-guided brachytherapy for cervical cancer.Material and methodsFor this experiment, a phantom was created and included a polyethylene tube, intended to simulate a tandem applicator, which was inserted into chicken meat and embedded in agar, along with magnetic resonance imaging (MRI)-compatible ovoid applicators. Three-dimensional images of the phantom were obtained using computed tomography (CT), MRI (T2-weighted), and intracavitary ultrasonography sectional images acquired at 1 mm slice intervals. Intracavitary ultrasonography images were acquired from within the simulated tandem applicator using a radial transducer. Magnetic resonance imaging and intracavitary ultrasonography images were manually registered onto CT images. The chicken meat was contoured as the target volume independently on the CT, MRI, and intracavitary ultrasonography images, and the Dice similarity coefficient was used to compare the target volumes. The dose distributions of a sample brachytherapy plan were also evaluated.ResultsComputed tomography, MRI, and intracavitary ultrasonography all visualized the three-dimensional phantom volumes. Intracavitary ultrasonography images depicted the meat with high echoic signals and a border clearly distinguishable from the surrounding agar. The Dice similarity coefficient values for the target volumes on CT vs. MRI, CT vs. intracavitary ultrasonography, and MRI vs. intracavitary ultrasonography were 0.966, 0.965, and 0.971, respectively, indicating similar contouring with the three modalities. Among the modalities, the differences in D50, D90, D98, and D100 values were 1.8%, 2.9%, 3.7%, and 2.9%, respectively.ConclusionsThree-dimensional reconstructed trans-applicator intracavitary ultrasonographic images clearly depicted meat tissue within the phantom, and could thus be used for brachytherapy planning. This study proves the concept of trans-applicator intracavitary ultrasonography for intracavitary brachytherapy. Further research such as development of intracavitary ultrasonography system, 3D reconstruction method, ultrasonography-compatible applicators, and ultrasonography-based target concept is warranted to assess the potential clinical application.

Description of a novel technique for ultrasound-based planning for gynaecological 3D brachytherapy and comparison between plans of this technique and 2D with fluoroscopy

“…In this study, local control at 3 years of 86%, overall survival of 75% and a cause-specific survival of 79% are reported. The use of transrectal ultrasound to guide treatment has also been described [ 8 , 9 ], as well as the experimental use of an internal transducer, through the applicator, for proper tumour delineation and subsequent planning [ 10 ].…”

Review of strategies for MRI based reconstruction of endocavitary and interstitial applicators in brachytherapy of cervical cancer

“…86 Many authors have shown the feasibility of US assisted cervix BT compare to MRI. 81,[87][88][89][90] Some studies have been presented supporting its use in terms of clinical outcomes of patients undergoing intracavitary BT based on US imaging, showing similar findings that MRI based procedures, following GEC ESTRO recommendations. 81,91 At the moment, although recent studies support the use of US for contouring HR-CTV for IGABT of cervical cancer, [92][93][94] its exclusive use in the reconstruction process has not yet been implemented in the case of complex and interstitial BT.…”