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Evaluation of New Markers for the Interstitial Plastic Component in MR-Based Cervix Brachytherapy

J Chimeno Hernandez1, F Blazquez1, G Montoliu2, J Bosque2, G Jose1, J Ruiz Rodriguez1, V Carmona Meseguer1, F Lliso-Valverde1, J Perez-Calatayud1*, (1) Radiotherapy Department,Hospital Universitari i Politecnic La Fe, Valencia,Spain , (2) Radiodiagnostic Department, Hospital Universitari I Politecnic La Fe, Valencia, Spain


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: (T2) clinical dosimetry is the ESTRO-ABS recommended planning procedure in cervix brachytherapy planning. To improve efficiency and accuracy, the planning should be done based exclusively in MR, avoiding CT registration. The use of interstitial needles improves both coverage and organs at risk sparing. This is the case of the Utrecht applicators (Elekta). Currently, there are dummies only for the endocavitary component (Perez-Calatayud 2009) but non for the Utrecht plastic needles, because their small diameter.
In our hospital, the needles reconstruction is managed using a self-developed virtual library (Otal 2017). The concern here is that it is based on the measurement provided by the Rad-Onc of the inserted depth derived from the reading of a special ruler.
The purpose of this work is to evaluate a new marker for the 1 mm inner diameter Utrecht interstitial component.

Methods: HDR MRI Lumen Marker (C4 Imaging) is a new sealed high-density polyethylene tube containing a cobalt chloride:N-Acetylcysteine saline solution. All MRI acquisitions were performed with Signa HDxt 3T (General Electric) with T2 mode and a slice thickness of 2.5 mm and the protocol described in Richart J (2018). The viability of the dummies was assessed in five patients. In order to adjust the solution distal limit inside the dummy with the maximum Source to Indexer Distance (SIDmax, it is 129 cm) of the microSelectron V3 (Elekta), a homemade gadget was added to the dummies.

Results: all the patients the dummies were completely visible in the axial sequence, allowing the complete catheters reconstruction.
The homemade gadget improved the accuracy and efficiency of the determination of SIDmax avoiding the uncertainty coming from the dark line generated by the plastic needles in the MRI images.

Conclusion: new dummies are visible in MRI 3T T2 allowing improving reconstruction efficiency and accuracy.


Brachytherapy, Reconstruction, MRI


Not Applicable / None Entered.

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