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Clinical Molecular PET/MRI Hybrid Imaging
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
It is the ultimate goal for hybrid PET/MRI systems to be able to acquire MR-signals at the very same time as the PET-signal is acquired, so a truly simultaneous measurement of them both is possible. This feature is needed for a very practical reason: first, MRI sequences take much longer to be acquired compared to a CT scan. A CT scan takes some seconds whilst a combination of desirable MRI-sequences can take up to an hour to be acquired. Moreover, the multitude of MRI-signals available (structural, molecular, in high temporal resolution) can be used for improvement of the PET-acquisition results. Due to their small dimensions compared to PMTs and their insensitivity to even very strong static and fluctuating magnetic fields, the availability of APDs and SiPMs was a key feature for simultaneous PET/MRI systems as they are available today. Beyond the rather practical technical reasons why one would aim for a simultaneous acquisition of PET along with MRI, there are a plurality of research and some clinical applications that only become possible, or at least profit, when PET and MRI are acquired simultaneously. The latter will be mentioned later in this chapter.
Brain cancer
Published in Ruijiang Li, Lei Xing, Sandy Napel, Daniel L. Rubin, Radiomics and Radiogenomics, 2019
William D. Dunn, Rivka R. Colen
Conventional MRI sequences, such as T1-weighted, T2-weighted (T2WI), gadolinium-enhanced T1WI, and fluid-attenuated inversion recovery (FLAIR) images are the most commonly obtained sequences in neuroradiology clinical practice. Visualized on gadolinium-enhanced T1WI, glioblastoma typically appears as a heterogeneously ring enhancing lesion, representing the active proliferating portion of the tumor with rapid angiogenesis and blood brain barrier disruption, surrounding non-enhancing hypointense regions that represent necrosis (Figures 13.1 and 13.2).9 Beyond the area of enhancement is the peritumoral T2-weighted/FLAIR hyperintensity, reflecting a mixture of edema and tumor infiltration in the surrounding tissue.10
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Published in Mara Cercignani, Nicholas G. Dowell, Paul S. Tofts, Quantitative MRI of the Brain: Principles of Physical Measurement, 2018
Francesco Grussu, Claudia A.M. Gandini Wheeler-Kingshott
As discussed earlier, most MRI sequences can be weighted to sensitise images to diffusion along a specific direction (given by the direction along which the diffusion gradient is applied). This gives reduced signal in areas of the sample where the self-diffusion coefficient in that direction is higher.
Brain Tumor Classification Using Enhanced Statistical Texture Features
Published in IETE Journal of Research, 2022
Mallikarjun Mudda, R. Manjunath, N. Krishnamurthy
Examination data of each patient contain three MRI sequences : T1-weighted images, T2-weighted images and PD-weighted images. All the image data are derived from 1.5T magnetic resonance imaging equipment of the General Electric (GE) Co. Ltd., with an axial FSE (fast spin echo) imaging sequence to obtain the MRI sequences, to reduce the sensitivity of the imaging system to the non-uniformity of the magnetic field and to increase the energy deposition of the echo sequence. The obtained T1-weighted images contain 124 slices, while T2-weighted images, PD-weighted images contain 24 slices, each from every patient. The image resolution in all slices is 512 × 512; however, the including number of slices in T1-weighted image sequence is quite different from that of T2-weighted images and PD-weighted images, which leads to the imaging thickness of a slice, the tissue location in the brain and the contained information are not completely corresponding. Therefore, in the experiment we have taken three MRI sequences from each T1-weighted images, T2-weighted images and PD-weighted images as the input data and combined all three to get registered image in the experimental test.