Laminaria tent insertion in preplanning MRI for CT-based cervical cancer brachytherapy.

Purpose: Preplanning magnetic resonance imaging (MRI) is routinely used in image-guided adaptive brachytherapy (IGABT) for cervical cancer. However, a preplanning MRI performed without an applicator does not have good accuracy of image fusion with a planning computed tomography (CT) performed with an applicator. This study aimed to evaluate the efficacy of laminaria tent insertion during pre-planning MRI for cervical cancer brachytherapy (BT).

Methods And Materials: Sixteen patients with cervical cancer were enrolled in the study. Images obtained from a single preplanning MRI performed with a laminaria tent inserted into the cervix were fused with images from the planning CT performed with an applicator during each BT session. The alignment between the high-risk clinical target volume on MRI (HR-CTV) and planning CT (HR-CTV) was assessed. Image fusion accuracy was classified as follows: maximum misalignment between HR-CTV and HR-CTV <5 mm was excellent, 5-10 mm as available, and >10 mm as not available. Image fusion accuracy was reviewed by two radiation oncologists.

Results: Fifty-nine BT sessions were analyzed. Fusion images for 39 (66%) sessions were categorized as excellent, and those for the remaining 12 (20%) sessions were available, and 8 (14%) were not available. Complications reported after laminaria tent insertion were grade-1 fever for 5 (8%) BT sessions in 5 patients and grade-1 pain for 8 (13%) sessions in 5 patients.

Conclusion: Laminaria tent insertion during pre-planning MRI may improve the accuracy of image fusion with planning CT and may help delineate the HR-CTV in CT-based IGABT for cervical cancer.