Peripheral moving‐table contrast‐enhanced magnetic resonance angiography (CE‐MRA) using a prototype 18‐channel peripheral vascular coil and scanning parameters optimized to the patient's individual hemodynamics

Purpose

To demonstrate that with a priori determination of individual patient hemodynamics, peripheral contrast‐enhanced magnetic resonance angiography (pCE‐MRA) can be customized to maximize signal‐to noise ratio (SNR) and avoid venous enhancement.

Materials and Methods

Using a 1.5T MRI scanner and prototype 18‐channel peripheral vascular (PV) coil designed for highly accelerated parallel imaging, geometry (g)‐factor maps were determined. SNR‐maximized protocols considering the two‐dimensional sensitivity encoding (2D SENSE) factor, TE, TR, bandwidth (BW), and flip angle (FA) were precalculated and stored. For each exam, a small aortic timing bolus was performed, followed by dynamic three‐dimensional (3D)‐MRA of the calf. Using this information, the aorta to pedal artery and calf arteriovenous transit times were measured. This enabled estimation of the maximum upper and middle station acquisition duration to allow lower station acquisition to begin prior to venous arrival. The appropriately succinct SNR‐optimized protocol for each station was selected and moving‐table pCE‐MRA was performed using thigh venous compression and high‐relaxivity contrast material.

Results

The protocol was successfully applied in 15 patients and all imaging demonstrated good SNR without diagnosis‐hindering venous enhancement.

Conclusion

By knowing each patient's venous enhancement kinetics, scan parameters can be optimized to utilize maximum possible acquisition time. Some time is added for the timing scans, but in return time‐resolved calf CE‐MRA, maximized SNR, and decreased risk of venous enhancement are gained. J. Magn. Reson. Imaging 2009;29:1106–1115. © 2009 Wiley‐Liss, Inc.     

A new approach towards improved visualization of myocardial edema using T2-weighted imaging: a cardiovascular magnetic resonance (CMR) study

Purpose:

To compare T2‐weighted cardiovascular magnetic resonance (CMR) imaging with AASPIR (asymmetric adiabatic spectral inversion recovery) and STIR (short T1 inversion recovery) for myocardial signal intensity, image quality, and fat suppression.

Materials and Methods:

Forty consecutive patients (47 ± 16 years old) referred by cardiologists for CMR‐based myocardial tissue characterization were scanned with both STIR and AASPIR T2‐weighted imaging approaches. Signal intensity of left ventricular myocardium was normalized to a region of interest generating a signal‐to‐noise ratio (SNR). In six patients with regional edema on STIR the contrast‐to‐noise ratio (CNR) was assessed. Two independent observers used a scoring system to evaluate image quality and artifact suppression. Six healthy volunteers (three males, 32 ± 7 years) were recruited to compare fat suppression between AASPIR and STIR.

Results:

SNR of AASPIR was greater than STIR for basal (128 ± 44 vs. 83 ± 40, P < 0.001), mid‐ (144 ± 65 vs. 96 ± 39, P < 0.01), and apical (145 ± 59 vs. 105 ± 35, P < 0.05) myocardium. Improved image quality and greater suppression of artifacts was demonstrated with AASPIR. In patients with regional edema, CNR increased by 49% with AASPIR, while SNR of pericardial fat did not differ (44 ± 39 vs. 33 ± 30, P > 0.05).

Conclusion:

Our findings support the implementation of an AASPIR‐based approach for T2‐weighted imaging due to improved pericardial fat suppression, image quality, and artifact suppression with greater CNR and SNR. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

A new method to combine contrast-enhanced magnetic resonance imaging during live ultrasound of the breast using volume navigation technique: a study for evaluating feasibility, accuracy and reproducibility in healthy volunteers

Objectives

To evaluate feasibility, accuracy and reproducibility of combined US-MR of the breast using volume navigation technique.

Subjects and methods

Five healthy females underwent bilateral contrast-enhanced MR (CE-MR) of the breast in supine position, after positioning three couples of markers on the breast. After CE-MR data uploading in the ultrasound (US) database, manual co-registration was obtained during live US of the breast by means of an electromagnetic transmitter positioned near the subject under examination and two electromagnetic sensors were mounted on the transducer bracket. Transmitter and sensors were connected to a position-sensing unit embedded in the US equipment allowing to track probe position and orientation within the electromagnetic field. Live US image were co-registered to the previously loaded breast CE-MR volume by coupling markers. For each subject, two independent radiologists recorded the examination time and verified twice image alignment using five fixed checkpoints. Pair t Student test and Wilcoxon test were used for statistical analysis.

Results

In all subjects US and CE-MR images were successfully combined. The examination time was 10 ± 2 vs. 9 ± 4 min, respectively (p = 0.642; NS). A total of one hundred measurements of images misalignment were performed: the measurements recorded between the two operators were 0.42 ± 0.32 cm and 0.58 ± 0.41 cm (p = 0.161; NS), and 0.50 ± 0.32 cm and 0.56 ± 0.52 cm (p = 0.928; NS), respectively.

Discussion

In our preliminary experience, volume navigation technique appears to be a accurate and reproducible method to combine CE-MR image during unilateral US of the breast.