First pointwise encoding time reduction with radial acquisition (PETRA) implementation for catheter detection in...

Area of Science:

• Medical Imaging
• Radiotherapy Physics
• Oncology

Background:

• Interstitial high-dose-rate (HDR) brachytherapy requires accurate catheter placement for effective treatment.
• Current imaging methods for catheter detection can have limitations in spatial accuracy and artifact susceptibility.

Purpose of the Study:

• To optimize and evaluate the Pointwise Encoding Time Reduction with Radial Acquisition (PETRA) sequence for detecting empty catheters in interstitial HDR brachytherapy.
• To assess the spatial accuracy and image quality of PETRA compared to conventional sequences.
• To evaluate the clinical feasibility of PETRA for MR-only treatment planning.

Main Methods:

• PETRA sequence was optimized and tested on phantoms containing empty catheters.
• Image quality and catheter detectability were assessed, comparing PETRA to T2-weighted sequences.
• Catheter tip position accuracy was evaluated using a treatment planning system (TPS).
• Clinical feasibility was assessed in a gynecological cancer patient with endometrial adenocarcinoma.

Main Results:

• PETRA provided positive signal for empty catheters with more accurate cross-sections than T2-weighted sequences (0.4 mm difference from nominal 2 mm diameter).
• PETRA exhibited minimal susceptibility differences and symmetric metal artifacts, unlike clinical sequences.
• PETRA-CT catheter tip position differences were < 1 mm, and interstitial catheter positional differences between PETRA and CT were < 1 mm on average.
• PETRA successfully detected interstitial catheters and templates in phantoms and a patient, fusing well with CT.

Conclusions:

• PETRA successfully and accurately detected interstitial catheters in phantoms.
• The first clinical implementation of PETRA demonstrates its potential for MR-only treatment planning in interstitial HDR brachytherapy.