Detunable wireless resonator arrays for TMJ MRI: A comparative study.

Temporomandibular Joint Magnetic Resonance Imaging (TMJ MRI) is crucial for diagnosing temporomandibular disorders (TMDs). This study advances the use of inductively coupled wireless coils to enhance imaging quality in TMJ MRI. After investigating multiple wireless resonator configurations, including a 1-loop design with a loop diameter of 9 cm, a 2-loop design with each loop having a diameter of 7 cm, and a 3-loop design with each loop having a diameter of 5 cm, our findings indicate that the 3-loop configuration achieves the optimal signal-to-noise ratio (SNR), surpassing other wireless arrays. Bilateral deployment of wireless coils further amplifies SNR, enabling superior visualization of TMJ structures, particularly with the 3-loop design. This cost-effective and comfortable solution, featuring a detunable design, eliminates the need for system parameter adjustments. The study indicates broad adaptability across MRI platforms, enhancing TMJ imaging for routine clinical diagnostics of TMDs.

A detunable wireless resonator insert for high-resolution TMJ MRI at 1.5 T.

MRI is essential for evaluating and diagnosing various conditions affecting the temporomandibular joint (TMJ) and surrounding structures, as it provides highly detailed images that enable healthcare professionals to assess the joints and surroundings in great detail. While commercial MRI scanners typically come equipped with basic receive coils, such as the head receive array, RF coils tailored for specialized applications like TMJ MRI must be obtained separately. Consequently, TMJ MRI scans are often conducted using the head receive array, yet this configuration proves suboptimal due to the lack of specialized coils. In this study, we introduce a simple, low-cost, and easy-to-reproduce wireless resonator insert to enhance the quality of TMJ MRI at 1.5 T. The wireless resonator shows a significant improvement in signal-to-noise ratio (SNR) and noticeably better imaging quality than the head array alone configuration in both phantom and in vivo images.

Detunable wireless Litzcage coil for human head MRI at 1.5 T.

Inductively coupled radiofrequency (RF) coils are an inexpensive and simple method to realize wireless RF coils in magnetic resonance imaging (MRI), which can significantly ease the MRI scan setup and improve patient comfort because they do not require bulky components such as cables, baluns, preamplifiers, and connectors. However, volume-type wireless coils are typically operated in transmit/receive mode because detuning such coils is much more challenging due to their complex structure and multiple resonant modes. Meanwhile, adding too many detuning circuits to a wireless coil would decrease the coil's quality factor, impair the signal-to-noise ratio, and increase the cost. In this work, we proposed, constructed, and tested a novel wireless volume coil based on the Litzcage design for 1.5-T head imaging. Being an inductively coupled coil, it has a much simpler structure, resulting in a lighter weight and less bulky design. Despite its simpler structure, it exhibits comparable imaging performance with a commercial receive array, providing an alternative to conventional wired coils with a high cost and complex structure. The unique figure-of-8 conductor pattern within the rungs ensures that the proposed wireless Litzcage can be efficiently detuned with minimal detuning circuits.

First ground-based, high-field, cryogen-free, mobile intraoperative magnetic resonance imaging system.

BACKGROUND/OBJECTIVE: Accurately targeting specific regions of interest in the brain is pivotal for the success of neurosurgical procedures. For example, the outcome of brain tumor resection is improved dramatically when surgeons are better able to define surgical borders. Intraoperative magnetic resonance imaging (iMRI) helps reduce the risk of damaging critical areas of the brain and makes it possible to confirm a successful resection or determine the need for further resection prior to closing a patient's head and finalizing the surgery. Here we present a ground-based, iMRI system with a mobile 1-T cryogen-free imager. METHODS: An ex-vivo experimental test of the novel iMRI system is performed to demonstrate preoperative and intraoperative imaging. RESULTS: The ground-based, mobile iMRI system presented here was successfully used to obtain intraoperative MR images without moving the imaging target or compromising conventional surgical techniques. CONCLUSION: The success of this experiment constitutes a major milestone towards the installation of a ground-based, high-field, mobile iMRI system in a hospital setting.

Low-cost inductively coupled stacked wireless RF coil for MRI at 3 T.

Inductively coupled RF coils are an inexpensive and simple method to realize wireless RF coils in MRI. They are low cost and can greatly ease the MR scan setup and improve patient comfort, since they do not require bulky components such as cables, baluns, preamplifiers, and connectors. Previous works have typically used single-layer loops as wireless coils. In this work, we present a novel wireless coil, where two loops are stacked and decoupled with a shared capacitor. We found that such a stacked structure could increase the coil efficiency and SNR. Compared with the single-layer wireless coil, both electromagnetic simulation and MR experiment results demonstrate that the stacked wireless coil has a considerable SNR improvement of approximately 35%.

Macroscopic structure of articular cartilage of the tibial plateau: influence of a characteristic matrix architecture on MRI appearance.

OBJECTIVE: The purpose of our study was to describe the structural organization of the extracellular matrix of articular cartilage of the tibial plateau and its influence on MRI appearance. MATERIALS AND METHODS: Spin-echo images of 11 resected tibial plateaus acquired at 7 T were compared with the structure of the extracellular matrix as shown by fracture sectioning the samples in the plane of imaging. Four samples were scanned at two different orientations relative to the main magnetic field (B(0)). T2 maps were acquired in two orientations on three of these four samples. RESULTS: On the basis of the presence of reproducible regional variations in the shape of the matrix, a characteristic matrix architecture was described. The location of peak signal intensity and T2 on MRI correlated with the level at which the matrix was estimated to be aligned at approximately 55 degrees to B(0) (r = 0.91). This correlation of matrix orientation relative to B(0) with T2 and signal intensity on MRI was not altered by regional variations in the shape of the matrix or by imaging samples at two different orientations. CONCLUSION: The structure of the extracellular matrix, through its orientation-dependent influence on T2 decay, exerts a strong influence on the MRI appearance of cartilage. At the tibial plateau, a characteristic matrix architecture is associated with an equally characteristic MRI appearance.

Hemoglobin imaging with hybrid magnetic resonance and near-infrared diffuse tomography.

This study examines the methodology of combining high-resolution information from magnetic resonance imaging into the reconstruction of near-infrared images of hemoglobin concentration and oxygen saturation. This type of hybrid imaging modality has the potential to provide noninvasive maps of hemoglobin concentration and oxygen saturation with relatively high spatial resolution with a fast time response. The study uses (i) tissue-simulating phantoms, as well as (ii) a rat cranial model, to test the method in two well-controlled situations. The phantom test demonstrates that better reconstruction accuracy can be achieved with the use of MRI-generated spatial regions in near-infrared reconstruction. The rat functional testing reveals that the technique can be applied to in vivo physiology, even in situations where the tissue is quite heterogenous. It also shows that the application of a priori structure in the finite element mesh as well as spatial constraints in the near-infrared image reconstruction, can significantly improve the quality of the resulting hemoglobin images.