Feasibility of MRI Zero TE Imaging for Interstitial Brachytherapy Needles Reconstruction
H Alsaleh, S Aldelaijan*, C Constantinescu, B Moftah, King Faisal Specialist Hospital & Research CentreRiyadhSA
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PO-GePV-M-252 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
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Purpose: MRI provides excellent soft tissue contrast for tumor delineation and OAR segmentation for gynecological HDR brachytherapy. However, reconstruction of the thin plastic interstitial needles requires a CT scan with marker as the MR images show no visible signal from needles with conventional T1 and T2 sequences due to the extremely short T2 of plastic. Zero TE imaging (ZTE) is a novel technique that can depict signal from structures with very short-T2 values. In this work we evaluate the capability of ZTE for needles reconstruction and if it can be used as an alternative method to CT scanning with markers.
Methods: Three empty 6F flexible catheter plastic interstitial needles (Elekta Brachytherapy, Netherlands) were immersed in demineralized water and scanned in GE 3T MRI system (Signa Premier; GE Healthcare, Milwaukee, WI) and Philips CT (Philips, Amsterdam, Netherlands). MR images were acquired with 3D T1W (TR\TE 552\10 ms ,and 1 mm voxel), 3D T2W (TR\TE 3051\104 ms , and 1 mm voxel) and silent Zero TE sequence (TR\TE 1060\20 ms , and 0.58 mm voxel). As a reference, helical CT images for the same setup were acquired with and without CT markers with 120 kV and 1 mm slice thickness. MR and CT images were registered in Eclipse treatment planning system (Varian Medical Systems, Palo Alto, CA).
Results: ZTE images generated a positive contrast for the interstitial needles as compared to conventional T1 and T2 images. Additionally, registration between CT with markers and ZTE MR showed better correlation of needle positions than T1 and T2.
Conclusion: ZTE imaging offers a promising alternative to CT imaging for needle reconstruction and makes MR-only gynecological brachytherapy treatment planning feasible. These findings need to be confirmed with clinical data and optimized ZET sequence for cancer patients.
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