Medical Physics · 2006 · 54 citations · 8 references
Nuclear ImagingEngineeringMagnetic Particle ImagingStructural DiagnosticsBiomedical EngineeringDiagnostic ImagingMagnetic Resonance ImagingProstate Brachytherapy SeedGradient EchoImaging AgentsTypical Brachytherapy SeedBrachytherapyRadiation OncologyMolecular ImagingRadiologyHealth SciencesImaging AnatomyMedical ImagingSusceptibility ArtifactMagnetic DistortionsNeuroimagingProstatic DiseaseMedical Image ComputingMri-guided Radiation TherapyBiomedical ImagingFunctional X-ray ImagingOperating Room ImagingNeuroscience
MRI sequences with a unidirectional linear read‑encode trajectory generate the artifacts modeled here, while other sequences such as gradient‑echo or steady‑state free‑precession may introduce additional distortions. The authors modeled magnetic distortions around an IMC6711 prostate brachytherapy seed for various orientations, generated simulated images from the distortion maps, and compared them to experimentally acquired spin‑echo, gradient‑echo, and steady‑state free‑precession images on a Philips MRI scanner. The simulated images matched experimental data, enabling accurate localization of the seed within the distortion patterns, and the artifact morphology varied with seed orientation relative to the magnetic field and the read‑encode gradient direction.
Magnetic distortions surrounding a typical brachytherapy seed (IMC6711, within a clinical magnetic resonance imager were modeled for a number of different seed orientations with respect to the main magnetic field. From these distortion maps, simulated images were produced. The simulated images were then compared to images experimentally acquired using a spin echo technique on a Philips magnetic resonance imaging scanner. The modeled images were found to conform very well to those acquired experimentally, thus allowing one to establish where the seed is positioned within the complex image distortion patterns. The artifact patterns were dependent on the orientation of the seed with the main magnetic field, as well as the direction of the read encode gradient. While all imaging schemes which employ a unidirectional linear read encode trajectory should produce the artifacts modeled in this article, sequences other than spin echo may produce additional artifacts. Gradient echo and steady‐state free precession imaging techniques were also performed on the seed for comparison.
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