Journal of magnetic resonance imaging : JMRI
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J Magn Reson Imaging · Aug 2000
Comparative StudyProsthetic heart valves: evaluation of magnetic field interactions, heating, and artifacts at 1.5 T.
The purpose of this study was to use ex vivo testing techniques to determine the magnetic resonance imaging (MRI) safety aspects for 32 different heart valve prostheses that had not been evaluated previously in association with the 1.5-T MR environment. Ex vivo testing was performed using previously described techniques for the evaluation of magnetic field interactions (deflection angle and torque), heating [gel-filled phantom and fluoroptic thermometry; 15 minutes of MRI at a specific absorption rate (SAR) of 1.1 W/kg], and artifacts (using gradient echo and T1-weighted spin-echo pulse sequences). Thirteen heart valve prostheses displayed interactions with the magnetic field. ⋯ Heating was < or =0.8 degrees C for these implants. Artifacts varied from mild to severe depending on the amount and type of metal used to make the particular heart valve prosthesis. For these 32 different heart valve prostheses, the relative lack of substantial magnetic field interactions and negligible heating indicate that MR procedures may be conducted safely in individuals with these implants using MR systems with static magnetic fields of 1.5 T or less.
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J Magn Reson Imaging · Aug 2000
Colon diseases: MR evaluation using combined T2-weighted single-shot echo train spin-echo and gadolinium-enhanced spoiled gradient-echo sequences.
This study demonstrates the appearance of large bowel diseases on magnetic resonance (MR) images using breath-hold T2-weighted half-Fourier acquisition snapshot turbo spin-echo (HASTE), breath-hold T1-weighted spoiled gradient-echo (SGE), and breath-hold gadolinium-enhanced T1-weighted SGE with and without fat-suppression sequences. The study represents a collective experience using a generalized combined abdominal-pelvic imaging protocol. Of 29 patients, 27 had surgical, endoscopic, microbiological, and/or histopathological correlation, and 2 had a diagnosis based on characteristic imaging findings. ⋯ Mass lesions were best shown on T2-weighted HASTE and gadolinium-enhanced fat-suppressed SGE images. Of 14 patients with non-neoplastic diseases, inflammatory changes were best shown on gadolinium-enhanced fat-suppressed T1-weighted SGE images in all cases. MR imaging with fast scanning breath-hold techniques and intravenous gadolinium enhancement provided good depiction and characterization of large bowel diseases.