In:
Medical Physics, Wiley, Vol. 43, No. 10 ( 2016-10), p. 5603-5615
Abstract:
Biliary stents may cause susceptibility artifacts, gradient‐induced artifacts, and radio frequency (RF) induced artifacts on magnetic resonance images, which can hinder accurate target volume delineation in radiotherapy. In this study, the authors investigated and quantified the magnitude of these artifacts for stents of different materials. Methods Eight biliary stents made of nitinol, platinum‐cored nitinol, stainless steel, or polyethylene from seven vendors, with different lengths (57–98 mm) and diameters (3.0–11.7 mm), were placed in a phantom. To quantify the susceptibility artifacts sequence‐independently, Δ B 0‐maps and T 2 ∗ ‐maps were acquired at 1.5 and 3 T. To study the effect of the gradient‐induced artifacts at 3 T, signal decay in images obtained with maximum readout gradient‐induced artifacts was compared to signal decay in reference scans. To quantify the RF induced artifacts at 3 T, B 1‐maps were acquired. Finally, Δ B 0‐maps and T 2 ∗ ‐maps were acquired at 3 T of two pancreatic cancer patients who had received platinum‐cored nitinol biliary stents. Results Outside the stent, susceptibility artifacts dominated the other artifacts. The stainless steel stent produced the largest susceptibility artifacts. The other stents caused decreased T 2 ∗ up to 5.1 mm (1.5 T) and 8.5 mm (3 T) from the edge of the stent. For sequences with a higher bandwidth per voxel (1.5 T: BW vox 〉 275 Hz/voxel; 3 T: BW vox 〉 500 Hz/voxel), the B 0‐related susceptibility artifacts were negligible ( 〈 0.2 voxels). The polyethylene stent showed no artifacts. In vivo , the changes in B 0 and T 2 ∗ induced by the stent were larger than typical variations in B 0 and T 2 ∗ induced by anatomy when the stent was at an angle of 30° with the main magnetic field. Conclusions Susceptibility artifacts were dominating over the other artifacts. The magnitudes of the susceptibility artifacts were determined sequence‐independently. This method allows to include additional safety margins that ensure target irradiation.
Type of Medium:
Online Resource
ISSN:
0094-2405
,
2473-4209
Language:
English
Publisher:
Wiley
Publication Date:
2016
detail.hit.zdb_id:
1466421-5
