膝关节3T和7TMRI使用专用的多通道线圈和优化的2D和3D的成像比较

目的显示两种7T("7T高分辨力成像"和"7T快速成像")28通道线圈膝关节成像与最佳的3T8通道线圈膝关节成像的比较。方法这项研究是伦理委员会审查批准的。3T和7TMRI均有10例健康的志愿者[(29.6±7.9)岁]进行了2个2D序列(PD-TSE和T1-SE)和3个3D序列(TRUFI,FLASH和PD-TSESPACE)检查。不同的阅片医师执行一致的评价标准来进行定量的对比噪声比(CNR)和定性评估。结果软骨-骨、软骨-液体、软骨-半月板和半月板-液体的信噪比(SNR)与CNR是一致的,大多数情况下7T比3T的要高,且7T快速检查略优于7T高分辨力检查。主观定性分析的结果是7T检查优于3T检查。阅片医师可靠性高(0.884～0.999)。结论通过高场强和合适的线圈,7T的分辨力可增强,图像采集时间可缩短,且能比3T得到更好的图像结果。要点①7T的MRI使用28通道膝关节线圈能得到高质量影像。②各同向性的3D-MR序列优于高磁场的2D序列。③7T高分辨力快速MR影像采集是可能的。④专用线圈确保高场强MRI在肌肉骨骼中的临床适用性。     

应用32通道心脏线圈在1.5T MR平扫中行全心冠状动脉成像定量分析:与常规的定量冠状动脉造影对比

正目的介绍一种在全心冠状动脉MR成像中判断显著狭窄的方法,并评估该方法的准确性及可重复性。材料与方法本研究方案经该项机构审查委员会批准,所有受试     

前瞻性比较T2加权MRI和动态增强MRI、3D MR波谱成像或扩散加权MRI在重复经直肠超声导引下活检的作用

目的比较T2WMRI和功能MRI技术在指导重复前列腺活检中的作用。方法68例活检阴性,直肠指诊阴性和前列腺特异抗原(PSA)升高病史的病人,在重复前列腺活检     

Comparison of three multichannel transmit/receive radiofrequency coil configurations for anatomic and functional cardiac MRI at 7.0T: implications for clinical imaging

Objectives

To implement, examine, and compare three multichannel transmit/receive coil configurations for cardiovascular MR (CMR) at 7T.

Methods

Three radiofrequency transmit-receive (TX/RX) coils with 4-, 8-, and 16-coil elements were used. Ten healthy volunteers (seven males, age 28?±?4?years) underwent CMR at 7T. For all three RX/TX coils, 2D CINE FLASH images of the heart were acquired. Cardiac chamber quantification, signal-to-noise ratio (SNR) analysis, parallel imaging performance assessment, and image quality scoring were performed.

Results

Mean total examination time was 29?±?5?min. All images obtained with the 8- and 16-channel coils were diagnostic. No significant difference in ejection fraction (EF) (P?>?0.09) or left ventricular mass (LVM) (P?>?0.31) was observed between the coils. The 8- and 16-channel arrays yielded a higher mean SNR in the septum versus the 4-channel coil. The lowest geometry factors were found for the 16-channel coil (mean ± SD 2.3?±?0.5 for R?=?4). Image quality was rated significantly higher (P?Conclusions All three coil configurations are suitable for CMR at 7.0T under routine circumstances. A larger number of coil elements enhances image quality and parallel imaging performance but does not impact the accuracy of cardiac chamber quantification.

Key Points

? Cardiac chamber quantification using 7.0T magnetic resonance imaging is feasible. ? Examination times for cardiac chamber quantification at 7.0T match current clinical practice. ? Multichannel transceiver RF technology facilitates improved image quality and parallel imaging performance. ? Increasing the number of RF channels does not influence cardiac chamber quantification.     

Two-Dimensional sixteen channel transmit/receive coil array for cardiac MRI at 7.0 T: Design, evaluation, and application

Purpose:

To design, evaluate, and apply a 2D 16‐channel transmit/receive (TX/RX) coil array tailored for cardiac magnetic resonance imaging (MRI) at 7.0 T.

Materials and Methods:

The cardiac coil array consists of two sections each using eight elements arranged in a 2 × 4 array. Radiofrequency (RF) safety was validated by specific absorption rate (SAR) simulations. Cardiac imaging was performed using 2D CINE FLASH imaging, T mapping, and fat–water separation imaging. The characteristics of the coil array were analyzed including parallel imaging performance, left ventricular chamber quantification, and overall image quality.

Results:

RF characteristics were found to be appropriate for all subjects included in the study. The SAR values derived from the simulations fall well within the limits of legal guidelines. The baseline signal‐to‐noise ratio (SNR) advantage at 7.0 T was put to use to acquire 2D CINE images of the heart with a very high spatial resolution of (1 × 1 × 4) mm³. The proposed coil array supports 1D acceleration factors of up to R = 4 without significantly impairing image quality.

Conclusion:

The 16‐channel TX/RX coil has the capability to acquire high contrast and high spatial resolution images of the heart at 7.0 T. J. Magn. Reson. Imaging 2012;36:847–857. © 2012 Wiley Periodicals, Inc.     

Design and application of a four-channel transmit/receive surface coil for functional cardiac imaging at 7T

Purpose

To design and evaluate a four‐channel cardiac transceiver coil array for functional cardiac imaging at 7T.

Materials and Methods

A four‐element cardiac transceiver surface coil array was developed with two rectangular loops mounted on an anterior former and two rectangular loops on a posterior former. specific absorption rate (SAR) simulations were performed and a B calibration method was applied prior to obtain 2D FLASH CINE (mSENSE, R = 2) images from nine healthy volunteers with a spatial resolution of up to 1 × 1 × 2.5 mm³.

Results

Tuning and matching was found to be better than 10 dB for all subjects. The decoupling (S₂₁) was measured to be >18 dB between neighboring loops, >20 dB for opposite loops, and >30 dB for other loop combinations. SAR values were well within the limits provided by the IEC. Imaging provided clinically acceptable signal homogeneity with an excellent blood‐myocardium contrast applying the B calibration approach.

Conclusion

A four‐channel cardiac transceiver coil array for 7T was built, allowing for cardiac imaging with clinically acceptable signal homogeneity and an excellent blood‐myocardium contrast. Minor anatomic structures, such as pericardium, mitral, and tricuspid valves and their apparatus, as well as trabeculae, were accurately delineated. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

Eight-channel transmit/receive body MRI coil at 3T.

Multichannel transmit magnetic resonance imaging (MR) systems have the potential to compensate for signal-intensity variations occurring at higher field strengths due to wave propagation effects in tissue. Methods such as RF shimming and local excitation in combination with parallel transmission can be applied to compensate for these effects. Moreover, parallel transmission can be applied to ease the excitation of arbitrarily shaped magnetization patterns. The implementation of these methods adds new requirements in terms of MRI hardware. This article describes the design of a decoupled eight-element transmit/receive body coil for 3T. The setup of the coil is explained, starting with standard single-channel resonators. Special focus is placed on the decoupling of the elements to obtain independent RF resonators. After a brief discussion of the underlying theory, the properties and limitations of the coil are outlined. Finally, the functionality and capabilities of the coil are demonstrated using RF measurements as well as MRI sequences.     

Design,evaluation and application of an eight channel transmit/receive coil array for cardiac MRI at 7.0 T

The objective of this work is to design, examine and apply an eight channel transmit/receive coil array tailored for cardiac magnetic resonance imaging at 7.0 T that provides image quality suitable for clinical use, patient comfort, and ease of use. The cardiac coil array was designed to consist of a planar posterior section and a modestly curved anterior section. For radio frequency (RF) safety validation, numerical computations of the electromagnetic field (EMF) and the specific absorption rate (SAR) distribution were conducted. In vivo cardiac imaging was performed using a 2D CINE FLASH technique. For signal-to-noise ratio (SNR) assessment reconstructed images were scaled in SNR units. The parallel imaging capabilities of the coil were examined using GRAPPA and SENSE reconstruction with reduction factors of up to R = 4. The assessment of the RF characteristics yielded a maximum noise correlation of 0.33. The baseline SNR advantage at 7.0 T was put to use to acquire 2D CINE images of the heart with a spatial resolution of 1 mm × 1 mm × 4 mm. The coil array supports 1D acceleration factors of up to R = 3 without impairing image quality significantly. For un-accelerated 2D CINE FLASH acquisitions the results revealed an SNR of approximately 140 for the left ventricular blood pool. Blood/myocardium contrast was found to be approximately 90 for un-accelerated 2D CINE FLASH acquisitions. The proposed 8 channel cardiac transceiver surface coil has the capability to acquire high contrast, high spatial and temporal resolution in vivo images of the heart at 7.0 T.     

Comparison of a 28-channel receive array coil and quadrature volume coil for morphologic imaging and T2 mapping of knee cartilage at 7T

Purpose:

To compare a new birdcage‐transmit, 28‐channel receive array (28‐Ch) coil and a quadrature volume coil for 7T morphologic MRI and T2 mapping of knee cartilage.

Materials and Methods:

The right knees of 10 healthy subjects were imaged on a 7T whole body magnetic resonance (MR) scanner using both coils. 3D fast low‐angle shot (3D‐FLASH) and multiecho spin‐echo (MESE) sequences were implemented. Cartilage signal‐to‐noise ratio (SNR), contrast‐to‐noise ratio (CNR), thickness, and T2 values were assessed.

Results:

SNR/CNR was 17%–400% greater for the 28‐Ch compared to the quadrature coil (P ≤ 0.005). Bland–Altman plots show mean differences between measurements of tibial/femoral cartilage thickness and T2 values obtained with each coil to be small (?0.002 ± 0.009 cm / 0.003 ± 0.011 cm) and large (?6.8 ± 6.7 msec/?8.2 ± 9.7 msec), respectively. For the 28‐Ch coil, when parallel imaging with acceleration factors (AF) 2, 3, and 4 was performed SNR retained was: 62%–69%, 51%–55%, and 39%–45%.

Conclusion:

A 28‐Ch knee coil provides increased SNR/CNR for 7T cartilage morphologic imaging and T2 mapping. Coils should be switched with caution during clinical studies because T2 values may differ. The greater SNR of the 28‐Ch coil could be used to perform parallel imaging with AF2 and obtain similar SNR as the quadrature coil. J. Magn. Reson. Imaging 2012;441‐448. © 2011 Wiley Periodicals, Inc.