Breast MRI at 7 Tesla with a bilateral coil and T1-weighted acquisition with robust fat suppression: image evaluation and comparison with 3 Tesla

Objectives

To evaluate the image quality of T1-weighted fat-suppressed breast MRI at 7 T and to compare 7-T and 3-T images.

Methods

Seventeen subjects were imaged using a 7-T bilateral transmit-receive coil and 3D gradient echo sequence with adiabatic inversion-based fat suppression (FS). Images were graded on a five-point scale and quantitatively assessed through signal-to-noise ratio (SNR), fibroglandular/fat contrast and signal uniformity measurements.

Results

Image scores at 7 and 3 T were similar on standard-resolution images (1.1?×?1.1?×?1.1-1.6 mm³), indicating that high-quality breast imaging with clinical parameters can be performed at 7 T. The 7-T SNR advantage was underscored on 0.6-mm isotropic images, where image quality was significantly greater than at 3 T (4.2 versus 3.1, P?≤?0.0001). Fibroglandular/fat contrast was more than two times higher at 7 T than at 3 T, owing to effective adiabatic inversion-based FS and the inherent 7-T signal advantage. Signal uniformity was comparable at 7 and 3 T (P?<?0.05). Similar 7-T image quality was observed in all subjects, indicating robustness against anatomical variation.

Conclusion

The 7-T bilateral transmit-receive coil and adiabatic inversion-based FS technique produce image quality that is as good as or better than at 3 T.

Key Points

? High image quality bilateral breast MRI is achievable with clinical parameters at 7 T. ? 7-T high-resolution imaging improves delineation of subtle soft tissue structures. ? Adiabatic-based fat suppression provides excellent fibroglandular/fat contrast at 7 T. ? 7- and 3-T 3D T1-weighted gradient-echo images have similar signal uniformity. ? The 7-T dual solenoid coil enables bilateral imaging without compromising uniformity.     

Imaging the female pelvis at 3.0 T

Three-Tesla whole body imaging is rapidly becoming part of routine clinical practice. Although it is generally thought that pelvic imaging at 3.0 T will be beneficial because of increased signal to noise and greater spectral separation, adjustments in protocol and sequence parameters are necessary to optimize image quality. The question remains as to whether 3.0-T imaging will offer further benefits beyond 1.5 T in terms of lesion characterization and functional imaging. This article aims to address safety concerns and to illustrate the potential benefits and technical challenges of imaging the female pelvis at 3.0 T. Imaging protocols and sequence parameters for routine gynecologic indications are suggested, and potential clinical applications at 3.0 T are discussed such as magnetic resonance spectroscopy, perfusion, diffusion weighted imaging, and the use of alternate contrast agents.     

Barriers to physicians' decisions to discuss hospice: insights gained from the United States hospice model

Due to its comprehensive and cost-saving design, hospice has become a critical component of health care. Physicians have become the primary gatekeepers to information on hospice and sources of referral to hospice. However, many physicians do not discuss hospice options until late in the disease course, when patients and their families are no longer able to benefit from hospice services. Although physicians, as well as patients and hospice personnel, cite patient and hospice structure factors as barriers, the present article will focus on barriers physicians have more control over, such as their discomfort discussing terminality and fear of losing contact with patients. Focusing on the American hospice model, the present article will review past findings, examine gaps in the research, and propose systematic ways to discern whether the factors physicians claim are barriers actually affect their decision making about hospice referral.     

Time‐dependent diffusion in skeletal muscle with the random permeable barrier model (RPBM): application to normal controls and chronic exertional compartment syndrome patients

The purpose of this work was to carry out diffusion tensor imaging (DTI) at multiple diffusion times T_d in skeletal muscle in normal subjects and chronic exertional compartment syndrome (CECS) patients and analyze the data with the random permeable barrier model (RPBM) for biophysical specificity. Using an institutional review board approved HIPAA‐compliant protocol, seven patients with clinical suspicion of CECS and eight healthy volunteers underwent DTI of the calf muscle in a Siemens MAGNETOM Verio 3 T scanner at rest and after treadmill exertion at four different T_d values. Radial diffusion values λ_rad were computed for each of seven different muscle compartments and analyzed with RPBM to produce estimates of free diffusivity D₀, fiber diameter a, and permeability κ. Fiber diameter estimates were compared with measurements from literature autopsy reference for several compartments. Response factors (post/pre‐exercise ratios) were computed and compared between normal controls and CECS patients using a mixed‐model two‐way analysis of variance. All subjects and muscle compartments showed nearly time‐independent diffusion along and strongly time‐dependent diffusion transverse to the muscle fibers. RPBM estimates of fiber diameter correlated well with corresponding autopsy reference. D₀ showed significant (p < 0.05) increases with exercise for volunteers, and a increased significantly (p < 0.05) in volunteers. At the group level, response factors of all three parameters showed trends differentiating controls from CECS patients, with patients showing smaller diameter changes (p = 0.07), and larger permeability increases (p = 0.07) than controls. Time‐dependent diffusion measurements combined with appropriate tissue modeling can provide enhanced microstructural specificity for in vivo tissue characterization. In CECS patients, our results suggest that high‐pressure interfiber edema elevates free diffusion and restricts exercise‐induced fiber dilation. Such specificity may be useful in differentiating CECS from other disorders or in predicting its response to either physical therapy or fasciotomy. Copyright © 2014 John Wiley & Sons, Ltd.     

High-resolution human cervical spinal cord imaging at 7 T

We present high‐resolution anatomical imaging of the cervical spinal cord in healthy volunteers at the ultrahigh field of 7 T with a prototype four‐channel radiofrequency coil array, in comparison with 3‐T imaging of the same subjects. Signal‐to‐noise ratios at both field strengths were estimated using the rigorous Kellman method. Spinal cord cross‐sectional area measurements were performed, including whole‐cord measurements at both fields and gray matter segmentation at 7 T. The 7‐T array coil showed reduced sagittal coverage, comparable axial coverage and the expected significantly higher signal‐to‐noise ratio compared with equivalent 3‐T protocols. In the cervical spinal cord, the signal‐to‐noise ratio was found by the Kellman method to be higher by a factor of 3.5 with the 7‐T coil than with standard 3‐T coils. Cervical spine imaging in healthy volunteers at 7 T revealed not only detailed white/gray matter differentiation, but also structures not visualized at lower fields, such as denticulate ligaments, nerve roots and rostral–caudal blood vessels. Whole‐cord cross‐sectional area measurements showed good agreement at both field strengths. The measurable gray/white matter cross‐sectional areas at 7 T were found to be comparable with reports from histology. These pilot data demonstrate the use of higher signal‐to‐noise ratios at the ultrahigh field of 7 T for significant improvement in anatomical resolution of the cervical spinal cord, allowing the visualization of structures not seen at lower field strength, particularly for axial imaging. Copyright © 2011 John Wiley & Sons, Ltd.     

Single breathhold noncontrast thoracic MRA using highly accelerated parallel imaging with a 32-element coil array

Purpose:

To evaluate the feasibility of performing single breathhold three‐dimensional (3D) thoracic noncontrast MR angiography (NC‐MRA) using highly accelerated parallel imaging.

Materials and Methods:

We developed a single breathhold NC MRA pulse sequence using balanced steady state free precession (SSFP) readout and highly accelerated parallel imaging. In 17 subjects, highly accelerated noncontrast MRA was compared against electrocardiogram‐triggered contrast‐enhanced MRA. Anonymized images were randomized for blinded review by two independent readers for image quality, artifact severity in eight defined vessel segments and aortic dimensions in six standard sites. NC‐MRA and CE‐MRA were compared in terms of these measures using paired sample t‐ and Wilcoxon tests.

Results:

The overall image quality (3.21 ± 0.68 for NC‐MRA versus 3.12 ± 0.71 for CE‐MRA) and artifact (2.87 ± 1.01 for NC‐MRA versus 2.92 ± 0.87 for CE‐MRA) scores were not significantly different, but there were significant differences for the great vessel and coronary artery origins. NC‐MRA demonstrated significantly lower aortic diameter measurements compared with CE‐MRA; however, this difference was not considered clinically relevant (>3 mm difference) for less than 12% of segments, most commonly at the sinotubular junction. Mean total scan time was significantly lower for NC‐MRA compared with CE‐MRA (18.2 ± 6.0 s versus 28.1 ± 5.4 s, respectively; P < 0.05).

Conclusion:

Single breathhold NC‐MRA is feasible and can be a useful alternative for evaluation and follow‐up of thoracic aortic diseases. J. Magn. Reson. Imaging 2012;35:963–968. © 2011 Wiley Periodicals, Inc.