scholarly journals Design, Implementation, and Evaluation of a Head and Neck MRI RF Array Integrated with a 511 keV Transmission Source for Attenuation Correction in PET/MR

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3297 ◽  
Author(s):  
Lara ◽  
Frass-Kriegl ◽  
Renner ◽  
Sieg ◽  
Pichler ◽  
...  
Keyword(s):  
Head And Neck ◽  
Attenuation Correction ◽  
Parallel Imaging ◽  
Signal To Noise Ratio ◽  
Rf Coil ◽  
Fully Integrated ◽  
Positron Emission ◽  
Rf Coil Array ◽  
Imaging Performance ◽  
Neck Coil

The goal of this work is to further improve positron emission tomography (PET) attenuation correction and magnetic resonance (MR) sensitivity for head and neck applications of PET/MR. A dedicated 24-channel receive-only array, fully-integrated with a hydraulic system to move a transmission source helically around the patient and radiofrequency (RF) coil array, is designed, implemented, and evaluated. The device enables the calculation of attenuation coefficients from PET measurements at 511 keV including the RF coil and the particular patient. The RF coil design is PET-optimized by minimizing photon attenuation from coil components and housing. The functionality of the presented device is successfully demonstrated by calculating the attenuation map of a water bottle based on PET transmission measurements; results are in excellent agreement with reference values. It is shown that the device itself has marginal influence on the static magnetic field B0 and the radiofrequency transmit field B1 of the 3T PET/MR system. Furthermore, the developed RF array is shown to outperform a standard commercial 16-channel head and neck coil in terms of signal-to-noise ratio (SNR) and parallel imaging performance. In conclusion, the presented hardware enables accurate calculation of attenuation maps for PET/MR systems while improving the SNR of corresponding MR images in a single device without degrading the B0 and B1 homogeneity of the scanner.

scholarly journals Capacitive versus Overlap Decoupling of Adjacent Radio Frequency Phased Array Coil Elements: An Imaging Robustness Comparison When Sample Load Varies for 3 Tesla MRI

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Michael J. Beck ◽  
Dennis L. Parker ◽  
J. Rock Hadley
Keyword(s):  
Parallel Imaging ◽  
Phased Array ◽  
Signal To Noise Ratio ◽  
Decoupling Method ◽  
3 Tesla Mri ◽  
Imaging Performance ◽  
Factor Maps ◽  
Decoupled Method ◽  
Array Coil ◽  
Selection Of

Phased array (PA) receive coils are built such that coil elements approximate independent antenna behavior. One method of achieving this goal is to use an available decoupling method to decouple adjacent coil elements. The purpose of this work was to compare the relative performance of two decoupling methods as a function of variation in sample load. Two PA receive coils with 5 channels (5-ch) each, equal outer dimensions, and formed on 12 cm diameter cylindrical phantoms of conductivities 0.3, 0.6, and 0.9 S/m were evaluated for relative signal-to-noise ratio (SNR) and parallel imaging performance. They were only tuned and matched to the 0.6 S/m phantom. Simulated and measured axial, sagittal, and coronal 5-ch PA coil SNR ratios were compared by dividing the overlap by the capacitive decoupled coil SNR results. Issues related to the selection of capacitor values for the two decoupling methods were evaluated by taking the ratio of the match and tune capacitors for large and small 2 channel (2-ch) PA coils. The SNR ratios showed that the SNR of the two decoupling methods were very similar. The inverse geometry-factor maps showed similar but better overall parallel imaging performance for the capacitive decoupled method. The quotients for the 2-ch PA coils’ maximum and minimum capacitor value ratios are 3.28 and 1.38 for the large and 3.28 and 2.22 for the small PA. The results of this paper demonstrate that as the sample load varies, the capacitive and overlap decoupling methods are very similar in relative SNR and this similarity continues for parallel imaging performance. Although, for the 5-ch coils studied, the capacitive decoupling method has a slight SNR and parallel imaging advantage and it was noted that the capacitive decoupled coil is more likely to encounter unbuildable PA coil configurations.

scholarly journals An 8 Dipole Transceive and 24 Loop Receive Array for Non-Human Primate Head Imaging at 10.5T

2020 ◽  
Author(s):  
Russell L. Lagore ◽  
Steen Moeller ◽  
Jan Zimmermann ◽  
Lance DelaBarre ◽  
Jerahmie Radder ◽  
...  
Keyword(s):  
High Resolution ◽  
Rhesus Macaque ◽  
Functional Imaging ◽  
Parallel Imaging ◽  
Larmor Frequency ◽  
Rf Coil ◽  
Imaging Performance ◽  
The Brain ◽  
Receive Array ◽  
Human Primate

AbstractA 32-channel RF coil was developed for brain imaging of anesthetized non-human primates (Rhesus Macaque) at 10.5 tesla. The coil is composed of an 8-channel dipole transmit/receive array, close-fitting 16-channel loop receive array headcap, and 8-channel loop receive array lower insert.The transceiver dipole array is composed of eight end-loaded dipole elements self-resonant at the 10.5 tesla proton Larmor frequency. These dipole elements were arranged on a plastic cylindrical former which was split in two to allow for convenient animal positioning. Nested into the bottom of the dipole array former is located an 8-channel loop receive array which contains 5×10 cm2 square loops arranged in two rows of four loops. Arranged in a close-fitting plastic headcap is located a high-density 16-channel loop receive array. This array is composed of 14 round loops 37 mm in diameter and two partially detachable, irregularly shaped loops that encircle the ears. Imaging experiments were performed on anesthetized non-human primates on a 10.5 tesla MRI system equipped with body gradients with a 60 cm open bore.The coil enabled submillimeter (0.58 mm isotropic) high resolution anatomical and functional imaging as well as tractography of fasciculated axonal bundles. The combination of a close-fitting loop receive array and dipole transceiver array allowed for a higher channel count receiver and consequent higher SNR and parallel imaging gains. Parallel imaging performance supports high resolution fMRI and dMRI with a factor of three reduction in sampling. The transceive array elements during reception contributed approximately one quarter of SNR in the lower half of the brain which was farthest from the close-fitting headcap receive array.

scholarly journals Influence of Rotation Increments on Imaging Performance for a Rotatory Dual-Head PET System

2017 ◽  
Vol 2017 ◽  
pp. 1-11
Author(s):  
Fanzhen Meng ◽  
Xu Cao ◽  
Xuezhou Cao ◽  
Jianxun Wang ◽  
Liang Li ◽  
...  
Keyword(s):  
Mean Squared Error ◽  
Interpolation Method ◽  
Signal To Noise Ratio ◽  
System Response ◽  
Prototype System ◽  
Squared Error ◽  
Positron Emission ◽  
Pet System ◽  
Imaging Performance ◽  
Better Than

For a rotatory dual-head positron emission tomography (PET) system, how to determine the rotation increments is an open problem. In this study, we simulated the characteristics of a rotatory dual-head PET system. The influences of different rotation increments were compared and analyzed. Based on this simulation, the imaging performance of a prototype system was verified. A reconstruction flowchart was proposed based on a precalculated system response matrix (SRM). The SRM made the relationships between the voxels and lines of response (LORs) fixed; therefore, we added the interpolation method into the flowchart. Five metrics, including spatial resolution, normalized mean squared error (NMSE), peak signal-to-noise ratio (PSNR), contrast-to-noise (CNR), and structure similarity (SSIM), were applied to assess the reconstructed image quality. The results indicated that the 60° rotation increments with the bilinear interpolation had advantages in resolution, PSNR, NMSE, and SSIM. In terms of CNR, the 90° rotation increments were better than other increments. In addition, the reconstructed images of 90° rotation increments were also flatter than that of 60° increments. Therefore, both the 60° and 90° rotation increments could be used in the real experiments, and which one to choose may depend on the application requirement.

scholarly journals Rapid Volumetric MRI Using Parallel Imaging With Order-of-Magnitude Accelerations and a 32-Element RF Coil Array

2005 ◽  
Vol 12 (5) ◽  
pp. 626-635 ◽  
Author(s):  
Daniel K. Sodickson ◽  
Christopher J. Hardy ◽  
Yudong Zhu ◽  
Randy O. Giaquinto ◽  
Patrick Gross ◽  
...  
Keyword(s):  
Parallel Imaging ◽  
Rf Coil ◽  
Volumetric Mri ◽  
Coil Array ◽  
Order Of Magnitude ◽  
Rf Coil Array

scholarly journals Signal-to-noise ratio and parallel imaging performance of a 16-channel receive-only brain coil array at 3.0 Tesla

2003 ◽  
Vol 51 (1) ◽  
pp. 22-26 ◽  
Author(s):  
Jacco A. de Zwart ◽  
Patrick J. Ledden ◽  
Peter van Gelderen ◽  
Jerzy Bodurka ◽  
Renxin Chu ◽  
...  
Keyword(s):  
Parallel Imaging ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
3.0 Tesla ◽  
Coil Array ◽  
Noise Ratio ◽  
Imaging Performance

scholarly journals The use of hyperpolarised 13C-MRI in clinical body imaging to probe cancer metabolism

2021 ◽  
Author(s):  
Ramona Woitek ◽  
Ferdia A. Gallagher
Keyword(s):  
Cancer Metabolism ◽  
Signal To Noise Ratio ◽  
Response Assessment ◽  
Early Response ◽  
Multiparametric Mri ◽  
Metabolic Reprogramming ◽  
Response To Treatment ◽  
Additional Information ◽  
Positron Emission ◽  
Breast And Prostate Cancer

AbstractMetabolic reprogramming is one of the hallmarks of cancer and includes the Warburg effect, which is exhibited by many tumours. This can be exploited by positron emission tomography (PET) as part of routine clinical cancer imaging. However, an emerging and alternative method to detect altered metabolism is carbon-13 magnetic resonance imaging (MRI) following injection of hyperpolarised [1-13C]pyruvate. The technique increases the signal-to-noise ratio for the detection of hyperpolarised 13C-labelled metabolites by several orders of magnitude and facilitates the dynamic, noninvasive imaging of the exchange of 13C-pyruvate to 13C-lactate over time. The method has produced promising preclinical results in the area of oncology and is currently being explored in human imaging studies. The first translational studies have demonstrated the safety and feasibility of the technique in patients with prostate, renal, breast and pancreatic cancer, as well as revealing a successful response to treatment in breast and prostate cancer patients at an earlier stage than multiparametric MRI. This review will focus on the strengths of the technique and its applications in the area of oncological body MRI including noninvasive characterisation of disease aggressiveness, mapping of tumour heterogeneity, and early response assessment. A comparison of hyperpolarised 13C-MRI with state-of-the-art multiparametric MRI is likely to reveal the unique additional information and applications offered by the technique.

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