Computed Tomography-Guided Optimization of Needle Insertion for Combined Intracavitary/Interstitial Brachytherapy With Utrecht Applicator in Locally Advanced Cervical Cancer

Abstract

There are no international guidelines for optimal needle insertion during interstitial intracavitary brachytherapy (IS-ICBT) for cervical cancer. We aimed to investigate the clinical feasibility and added value of computed tomography (CT) guidance to optimize needle insertion in IS-ICBT using the Utrecht applicator and to evaluate needle shifts. Methods and Materials: We enrolled 24 patients who were treated with interstitial-brachytherapy. Two CT scans each were performed for every patient: (1) after applicator insertion without needles (CT preneedle ) and (2) after needle insertion (CT postneedle ). In addition to magnetic resonance imaging after external-beam radiation therapy, CT preneedle was used to determine optimal needle locations and insertion lengths based on applicator and organs at risk positioning on the day of treatment; CT postneedle was used for IS-ICBT planning. The needle-channel axis was used as a reference to determine needle-shift evolution. Results: A total of 266 interstitial needles were inserted in 76 of 93 BT fractions with high intra-and interpatient variations in the number of inserted needles. Based on CT preneedle findings, needle insertion was avoided in 9, 4, 2, and 2 patients at the first, second, third, and fourth fractions, respectively. The unloaded needle frequency was 4%. Average needle contribution to total dwell time was 37.2% AE 19.2%. Shifting was observed in 68% of the needles (mean shift 2.0 AE 2.3 mm), mostly in the posterior direction, and in needles with a larger insertion length. Needle reinsertion was not needed in any patient. No complication due to needle insertion was observed, except for minor vaginal bleeding in 1 patient after needle removal. Conclusions: The adaptive CT-guided IS-ICBT application was feasible and resulted in fewer unloaded needle insertions or complications and more efficient use with higher needle contribution to the treatment. Needle shift was frequent but did not require needle reinsertion with the proposed method.

Multibody dynamic modeling of the behavior of flexible instruments used in cervical cancer brachytherapy

“…5 Related is the ability to accurately position IS needles in the presence of tissue and applicator forces. 6,7 The behavior of flexible BT instruments, such as afterloader source cables or needles, in applicators therefore needs to be well understood, whereas the focus in literature has been on quantifying position variations. This knowledge may additionally aid automated planning of curved source and needle channels in patient-tailored BT applicators, for which constraints on curvature, clearance, and torsion need to be set to ensure that instruments can be predictably inserted.…”

“…Geometric source positioning variations should be minimized as these may systematically affect the dose delivered per fraction, impacting predicted local control and morbidity 5 . Related is the ability to accurately position IS needles in the presence of tissue and applicator forces 6,7 . The behavior of flexible BT instruments, such as afterloader source cables or needles, in applicators therefore needs to be well understood, whereas the focus in literature has been on quantifying position variations.…”

Proton Arc Therapy vs Interstitial HDR Brachytherapy in Gynecologic Cancer with Parametrial/pelvic Side Wall Extension

“…Dosimetric effects of interfractional displacement of source or needle positions is often ignored in iHDR treatment. Tambas et al [24] reported that 68% of needles shifted 2 6 2.3 mm, and other researchers have reported shifts up to 5 mm [25][26][27]. Such shifts alter dose distribution and are comparable to the typical robustness range of a proton plan of 3 mm/3.5%.…”

A Novel Workflow with a Customizable 3D Printed Vaginal Template and a Direction Modulated Brachytherapy (DMBT) Tandem Applicator for Adaptive Interstitial Brachytherapy of the Cervix

“…In our example patient case for 3D printing and the five cases for retrospective planning analysis, we manually reoptimized the needle positions based on the geometric locations of the anatomy of the target and the OARs, and our understanding of the dosimetric capabilities and limits of the DMBT tandem, but of course, it is in our long-term interest to develop an optimization algorithm suitable for this task for a more seamless implementation of the overall proposed workflow. In fact, this is an area of active research in general [ 28 , 29 , 30 , 31 , 32 ].…”