SU‐F‐E‐02: A Feasibility Study for Application of Metal Artifact Reduction Techniques in MR‐Guided Brachytherapy Gynecological Cancer with Titanium Applicators

Purpose: Utilization of Titanium Tandem and Ring (T&R) applicators in MR‐guided brachytherapy has become widespread for gynecological cancer treatment. However, Titanium causes magnetic field disturbance and susceptibility artifact, which complicate image interpretation. In this study, metal artifact reduction techniques were employed to improve the image quality and reduce the metal related artifacts. Methods: Several techniques were employed to reduce the metal artifact caused by titanium T&R applicator. These techniques include Metal Artifact Reduction Sequence (MARS), View Angle Tilting (VAT) to correct in‐plane distortion, and Slice Encoding for Metal Artifact Correction (SEMAC) for through‐plane artifact correction. Moreover, MARS can be combined with VAT to further reduce the in‐plane artifact by reapplying the selection gradients during the readout (MARS+VAT). SEMAC uses a slice selective excitation but acquires additional z‐encodings in order to resolve off‐resonant signal and to reduce through‐plane distortions. Results: Comparison between the clinical sequences revealed that increasing the bandwidth reduces the error in measured diameter of T&R. However, the error is larger than 4mm for the best case with highest bandwidth and spatial resolution. MARS+VAT with isotropic resolution of 1mm reduced the error to 1.9mm which is the least among the examined 2D sequences. The measured diameter of tandem from SEMAC+VAT has the closest value to the actual diameter of tandem (3.2mm) and the error was reduced to less than 1mm. In addition, SEMAC+VAT significantly reduces the blooming artifact in the ring compared to clinical sequences. Conclusion: A higher bandwidth and spatial resolution sequence reduces the artifact and diameter of applicator with a slight compromise in SNR. Metal artifact reduction sequences decrease the distortion associated with titanium applicator. SEMAC+VAT sequence in combination with VAT revealed promising results for titanium imaging and can be utilized for MR‐guided brachytherapy in gynecological cancer. The author is employee with Philips Healthcare