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Erschienen in:
16.10.2017 | Technical Note
Preliminary results of a new workflow for MRI/CT-based image-guided brachytherapy in cervical carcinoma
Erschienen in: Japanese Journal of Radiology | Ausgabe 12/2017
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Purpose
We propose a method of image-guided brachytherapy (IGBT) that combines MRI-based target volume delineation for the first fraction with CT datasets of subsequent fractions, using an automatic, applicator-based co-registration, and report our preliminary experience.
Materials and methods
The MRI of the first fraction was used for the first brachytherapy planning. For each subsequent brachytherapy fraction, after the same applicator insertion, a new CT scan with the applicator in place was obtained. The MR image set was registered to the subsequent brachytherapy treatment planning CT using the applicator for rigid body registration. To demonstrate the registration quality, we used here the Dice index as a measurement of tandem delineation overlap between CT and MRI.
Results
The median Dice index was 0.879 (range 0.610–0.932), which indicated that the contours on CT and MRI fitted well. With this combination method, the median D90 of HR CTV and the calculated D2 cm3 of the bladder, rectum, and sigmoid in each fraction were 7.2 (4.0–10.4), 5.9 (2.3–7.7), 4.0 (1.9–6.7), and 3.8 (0.6–7.2) Gy, respectively.
Conclusion
Our described method of MRI-guided IGBT offers a practical option for the benefits of target delineation.