Journal of magnetic resonance imaging : JMRI
-
J Magn Reson Imaging · Sep 2001
MRI of carcinoid tumors: spectrum of appearances in the gastrointestinal tract and liver.
The purpose of this study was to evaluate the spectrum of appearances of gastrointestinal carcinoid tumors at magnetic resonance imaging (MRI) and to elucidate patterns of appearances of carcinoid liver metastases on precontrast and postgadolinium images. The MR examinations of 29 patients (11 men, 18 women; age range, 33-87 years) with histologically confirmed gastrointestinal carcinoid tumors, representing our complete 9.5 years of experience with this entity, were retrospectively reviewed. Twelve patients had MR examinations prior to resection or biopsy of the primary tumor (preoperative group); 17 patients were imaged postsurgically (postoperative group). ⋯ Twenty-three metastases (15%) were visible only on immediate postgadolinium images. MRI is able to demonstrate findings in carcinoid tumors, including the primary tumor, mesenteric metastases, and liver metastases. Liver metastases are commonly hypervascular and may be demonstrable only on immediate postgadolinium images.
-
J Magn Reson Imaging · Sep 2001
Metallic neurosurgical implants: evaluation of magnetic field interactions, heating, and artifacts at 1.5-Tesla.
The purpose of this study was to use ex vivo testing to determine the magnetic resonance imaging (MRI) safety aspects for seven different metallic neurosurgical implants 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 1.4 W/kg), and artifacts (using T1-weighted, spin-echo and gradient-echo pulse sequences). None of the metallic implants displayed interactions with the magnetic field. ⋯ Artifacts were relatively minor. The lack of magnetic field interactions and negligible heating indicate that MR procedures may be conducted safely in patients with these neurosurgical implants using MR systems with static magnetic fields of 1.5-T or less. Furthermore, these implants may be considered for use in interventional MR procedures insofar as the MR safe qualities and relatively small artifacts would likely be desirable for such procedures.
-
Accurate localization of minimally invasive devices is critical to the success of interventional procedures. Device orientation and tip position are two of the most important pieces of information needed to define device location for magnetic resonance imaging (MRI)-guided interventional procedures. While a single one-element micro coil incorporated into an interventional device has proven to be effective in some applications, it can only supply tip position information. ⋯ This makes the micro coil design appropriate for many flexible interventional devices. Reliable near-real-time tracking of three points on an interventional device is demonstrated on a 0.2T MRI system with modest gradient performance. Phantom and in vivo animal experiments are used to demonstrate the utility of this new coil design.
-
J Magn Reson Imaging · Jun 2001
Comparative StudyT2-weighted MRI of the female pelvis: comparison of breath-hold fast-recovery fast spin-echo and nonbreath-hold fast spin-echo sequences.
In 49 patients who had pelvic abnormalities, breath-hold T2-weighted fast-recovery (FR)-fast spin-echo (FSE) (imaging time = 24 sec) and nonbreath-hold FSE MR images (2 min 8 sec) were compared qualitatively (on a four-point scale) and quantitatively (using signal-to-noise ratios (SNRs) and contrast ratios (/SIs of the lesions-SIs of the myometrium/SIs of the myometrium)). Motion artifacts were reduced on breath-hold FR-FSE (3.8:3.2 = breath-hold FSE:nonbreath-hold FSE, P < 0.01) and image quality was comparable (3.8:3.7, NS). In all patients, pathology (leiomyoma [N = 26], adenomyosis [N = 10], endometrial carcinoma [N = 8], and ovarian cystic lesions [N = 21]) was recognized with comparable lesion conspicuity (3.8:3.7, NS) and better delineation of the structures (3.9:3.6, P < 0.05) on the FR-FSE images. ⋯ Magn. Reson. Imaging 2001;13:930-937.
-
In vivo magnetic resonance spectroscopy (MRS) addresses metabolic pathways and their steady states in different tissue types. The brain has by tradition, and due to technical limitations in other organs, been one of the tissues most studied by MRS, and both 1H- and 31P-MRS have been used. ⋯ Furthermore, MR sensitivity is much greater for protons than it is for phosphorus and 1H-MRS, therefore allowing better spatial resolution. This review focuses on neurospectroscopy and diagnostic insights into diverse neurological problems provided by 1H-MRS applied as a clinical tool.