Development of Spherical Postmortem Brain Container for High Resolution 7T MR Spectroscopy
Poster No:
1954
Submission Type:
Abstract Submission
Authors:
Shannon Lamb1, Jessica Weber1, Minjie Wu1, Howard Aizenstein1, Shaolin Yang1
Institutions:
1University of Pittsburgh, Pittsburgh, PA
First Author:
Co-Author(s):
Introduction:
Magnetic Resonance Spectroscopy (MRS) is a valuable technique for investigating the chemical composition of the brain and is increasingly used in postmortem studies. Magnetic shimming is the vital process of improving magnetic field homogeneities. Inhomogeneities can result in signal dropout, line broadening, localization error, and reduced spectral resolution in MRS. Both shimming efficiency and potentially achieved magnetic field homogeneity at 7T are sensitive to the shape of the postmortem brain container in the scanner bore. A more spherically symmetrical container may bring about a more homogenous magnetic field, and the shimming procedure may be more efficient and effective. Therefore, in this abstract we report the build and experimental test of the spherical postmortem brain container (SPBC) for use in postmortem brain studies.
Methods:
We had various constraints to consider when designing and manufacturing the SPBC. First, the container needs to be as close to a perfect sphere as possible, mimicking that of MRI QA or calibration phantoms, and no larger than 180 mm. The SPBC needs to fit various brain sizes and be watertight. The brain also has to be held in the approximate center of the container for the most optimal results. Furthermore, the container must be able to stay stationary while on a shaker table, which is used to dislodge air bubbles trapped in the liquid and the liquid-brain interfaces. Finally, the container needs to be easy to open and clean.
We evaluated the performance of the SPBC by comparisons with a cylindrical postmortem brain container detailed in a Sanghoon Kim et al. paper (2021). First, the SPBC needs to have an easier and quicker set up in the scanner bore. The shimming procedure with the SPBC needs to converge quicker and provide the same or better magnetic field homogeneity compared to the cylindrical container. The SPBC must also produce images with minimal artifacts and spectra with sharp metabolite peaks. To test these parameters, we filled the containers with an ovine brain immersed in formalin or Fomblin. The SPBC was placed in a 7T Nova head coil and a set of sequences, including localizer, FASTESTMAP, MP2RAGE (INV1, INV2, and UNI), and MRS (STEAM) sequences were scanned to acquire the MRI and MRS data from the postmortem brains.
We evaluated the performance of the SPBC by comparisons with a cylindrical postmortem brain container detailed in a Sanghoon Kim et al. paper (2021). First, the SPBC needs to have an easier and quicker set up in the scanner bore. The shimming procedure with the SPBC needs to converge quicker and provide the same or better magnetic field homogeneity compared to the cylindrical container. The SPBC must also produce images with minimal artifacts and spectra with sharp metabolite peaks. To test these parameters, we filled the containers with an ovine brain immersed in formalin or Fomblin. The SPBC was placed in a 7T Nova head coil and a set of sequences, including localizer, FASTESTMAP, MP2RAGE (INV1, INV2, and UNI), and MRS (STEAM) sequences were scanned to acquire the MRI and MRS data from the postmortem brains.
Results:
The current SPBC is composed of 10 major components in three different categories of materials (see Figure 1). The sphere top, sphere bottom, sphere cap, sphere cap handle, and sphere base were all prototyped on the UltiMaker S5 3D Printer in polylactic acid (PLA). The 2 brain platforms were made of acrylic and are used to keep the brain in the center of the sphere regardless of liquid density or agitation. The rubber seals were cut from 3 mm rubber mats. The resulting design had two key spherically asymmetric functional components. The three rectangular cavities at the bottom of the sphere lock with the base to prevent movement when on the shaker plate. The three depressions on the top of the sphere provide an ergonomic grip.
The SPBC was quicker and easier to set up in the scanner bore with the coil compared to the cylindrical container. The SPBC had a faster time to converge in the shimming process. It exhibited similarly sharp spectral peaks and comparable image quality to the cylindrical container. Although ring-shaped artifacts were seen in the MP2RAGE INV1 and INV2 formalin images, no artifacts were seen in the acquired MP2RAGE INV1 and INV2 Fomblin images (see Figure 2).
The SPBC was quicker and easier to set up in the scanner bore with the coil compared to the cylindrical container. The SPBC had a faster time to converge in the shimming process. It exhibited similarly sharp spectral peaks and comparable image quality to the cylindrical container. Although ring-shaped artifacts were seen in the MP2RAGE INV1 and INV2 formalin images, no artifacts were seen in the acquired MP2RAGE INV1 and INV2 Fomblin images (see Figure 2).
Conclusions:
The SPBC has shown preliminary superiority to its cylindrical competition in ease of use due to the faster shimming time and similar setup to a phantom. Once the SPBC has been proven to work with multiple different solutions and with minimal artifacts, it has the potential to expand our understanding of metabolite quantities and locations within Alzheimer's disease, Parkinson's disease, and various mood disorders using high-resolution MRS.
Novel Imaging Acquisition Methods:
Anatomical MRI 2
MR Spectroscopy 1
Physiology, Metabolism and Neurotransmission:
Physiology, Metabolism and Neurotransmission Other
Keywords:
Magnetic Resonance Spectroscopy (MRS)
MRI
STRUCTURAL MRI
Other - Postmortem
1|2Indicates the priority used for review