Hydro-MRI of the small bowel: effect of contrast volume, timing of contrast administration, and data acquisition on bowel distention.

OBJECTIVE: The purpose of this study was to assess oral contrast agents, volumes of the agents, and time points of data acquisition in regard to small-bowel distention and patient acceptance. SUBJECTS AND METHODS: Six healthy volunteers underwent imaging on 16 different days. Four volumes (450, 900, 1,350, and 1,800 mL) of each of the four contrast compounds (0.2% locust bean gum plus 2.5% mannitol, VoLumen containing 2.0% sorbitol, VoLumen containing 1.4% sorbitol, and tap water) were used. Two-dimensional true fast imaging with steady-state free precession data sets were acquired at 5-minute intervals after contrast ingestion. Distention values for small-bowel segments (duodenum, proximal and distal jejunum, ileum) and occurrence of side effects were documented. RESULTS: Analysis of bowel distention revealed significantly greater distention for all carbohydrate sugar alcohol-containing solutions compared with water but no significant difference among the three contrast agents. Sufficient duodenal distention was achieved with 900 mL of any of the contrast agents, but imaging had to be performed soon after ingestion. For MRI of the distal jejunum and ileum, a volume of 1,350 mL is preferable, and the time point of data acquisition plays a minor role. Ingestion of 1,800 mL of the carbohydrate sugar alcohol solutions led to a significantly higher rate of side effects such as abdominal cramps than did ingestion of smaller volumes. CONCLUSION: The data indicate that sufficient contrast consumption and optimal timing of data acquisition are essential to distention of the small bowel. Oral contrast agent protocols should be adapted to the bowel region in question.

Whole-body MRI for staging patients with head and neck squamous cell carcinoma.

CONCLUSIONS: Whole-body MRI is feasible for the tumor staging of patients with malignant head and neck tumors and appears to be a quick, reliable and proven alternative in general and for patients with contraindications to CT. This examination minimizes the logistical effort required compared to multimodality strategies. Its economic impact remains to be determined. OBJECTIVE: To assess the performance of whole-body MRI for staging patients with squamous cell carcinoma of the head and neck region. MATERIAL AND METHODS: This was a randomized, prospective clinical study. For tumor staging, 21 patients (mean age 56.7 years; range 43-80 years) with advanced malignant head and neck tumors underwent whole-body MRI in addition to routinely performed imaging investigations, including sonography, chest X-ray, CT of the head, neck and thorax and endoscopy. All investigations were accomplished within a period of 10+/-3 days in a random order. A randomized, blinded, consensus assessment of all the whole-body MRI examinations was performed by two radiologists. The localization and extent of the primary tumor and metastases were documented for whole-body MRI and compared to the standard of reference (all other imaging modalities as well as histology). Point estimates of the diagnostic accuracy of whole-body MRI were calculated. RESULTS: In accordance with the standard of reference, the overall TNM category was correctly determined with whole-body MRI in all 21 patients. However, four patients were classified as having carcinoma of unknown primary, as the primary tumor was not found with any imaging modality. Two patients had mediastinal, pulmonary and hepatic metastases.

Myocardial infarct: depiction with contrast-enhanced MR imaging--comparison of gadopentetate and gadobenate.

Institutional review board approval and patient written informed consent were obtained. On two separate occasions, 24 hours apart, contrast-enhanced cardiac magnetic resonance (MR) imaging was performed prospectively at 1, 3, 5, 10, and 20 minutes after injection of gadopentetate dimeglumine and gadobenate dimeglumine in 15 patients (11 men, four women) with history of myocardial infarction. Both agents allowed detection of infarcted myocardium. T1 values at all times were significantly (P < .05) lower for gadobenate, compared with values for gadopentetate, in both infarcted and noninfarcted myocardium. At 1 minute after administration of both agents, T1 values in left ventricular cavity (LVC) were not different; at 3-20 minutes after injection, values were significantly (P < .05) lower for gadobenate. Differences between contrast-to-noise ratio (CNR) values of infarcted and noninfarcted myocardium were significantly higher on gadobenate-enhanced images (P < .05). CNR values between infarcted myocardium and LVC were significantly higher on gadopentetate-enhanced images (P < .05). Gadopentetate might permit better delineation of infarcts, especially subendocardial infarcts.

Interventional magnetic resonance angiography with no strings attached: wireless active catheter visualization.

Active instrument visualization strategies for interventional MR angiography (MRA) require vascular instruments to be equipped with some type of radiofrequency (RF) coil or dipole RF antenna for MR signal detection. Such visualization strategies traditionally necessitate a connection to the scanner with either coaxial cable or laser fibers. In order to eliminate any wire connection, RF resonators that inductively couple their signal to MR surface coils were implemented into catheters to enable wireless active instrument visualization. Instrument background to contrast-to-noise ratio was systematically investigated as a function of the excitation flip angle. Signal coupling between the catheter RF coil and surface RF coils was evaluated qualitatively and quantitatively as a function of the catheter position and orientation with regard to the static magnetic field B0 and to the surface coils. In vivo evaluation of the instruments was performed in interventional MRA procedures on five pigs under MR guidance. Cartesian and projection reconstruction TrueFISP imaging enabled simultaneous visualization of the instruments and vascular morphology in real time. The implementation of RF resonators enabled robust visualization of the catheter curvature to the very tip. Additionally, the active visualization strategy does not require any wire connection to the scanner and thus does not hamper the interventionalist during the course of an intervention.

Whole-body 3D MR angiography of patients with peripheral arterial occlusive disease.

OBJECTIVE: We assessed the diagnostic performance of whole-body 3D contrast-enhanced MR angiography in comparison with digital subtraction angiography (DSA) of the lower extremities in patients with peripheral arterial occlusive disease. SUBJECTS AND METHODS. Fifty-one patients with clinically documented peripheral arterial occlusive disease referred for DSA of the lower extremity arterial system underwent whole-body MR angiography on a 1.5-T MR scanner. Paramagnetic gadobutrol was administered and five contiguous stations were acquired with 3D T1-weighted gradient-echo sequences in a total scanning time of 72 sec. DSA was available as a reference standard for the peripheral vasculature in all patients. Separate blinded data analyses were performed by two radiologists. Additional vascular disease detected by whole-body MR angiography was subsequently assessed on sonography, dedicated MR angiography, or both. RESULTS: All whole-body MR angiography examinations were feasible and well tolerated. AngioSURF-based whole-body MR angiography had overall sensitivities of 92.3% and 93.1% (both 95% confidence intervals [CIs], 78-100%) with specificities of 89.2% and 87.6% (both CIs, 84-98%) and excellent interobserver agreement (kappa = 0.82) for the detection of high-grade stenoses. Additional vascular disease was detected in 12 patients (23%). CONCLUSION: Whole-body MR angiography permits a rapid, noninvasive, and accurate evaluation of the lower peripheral arterial system in patients with peripheral arterial occlusive disease, and it may allow identification of additional relevant vascular disease that was previously undetected.

Peripheral vasculature: whole-body MR angiography with midfemoral venous compression--initial experience.

Five volunteers and 10 patients suspected of having peripheral vascular disease underwent multistation contrast material-enhanced three-dimensional whole-body magnetic resonance (MR) angiography. The first examination, based on standard protocol, lasted 72 seconds, while the following two examinations, performed with a high-spatial-resolution T1-weighted gradient-recalled-echo sequence for the last two stations (lower extremities) lasted 170 seconds. In the second high-resolution examination, midfemoral venous compression was used. Intraindividual comparison showed the high-resolution protocol with venous compression resulted in the best qualitative and quantitative image quality through higher signal-to-noise and contrast-to-noise ratios in the calf arteries. Despite prolonged acquisition times, there was no venous contamination. The data suggest that midfemoral venous compression should be incorporated in multistation protocols of the lower extremities to improve depiction of calf arteries without disturbing venous overlap.