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Antje Hellwich
Antje Hellwich
@antjehellwich.bsky.social
4 months ago
To date, 7T TOF-MRA has shown value in the evaluation of cerebrovascular malformations, atherosclerosis, and neurodegenerative diseases. However, it also faces challenges such as susceptibility artifacts at the air-bone interface of the sella turcica region, and physiological motion (e.g., vascular pulsation), which lead to suboptimal imaging of the petrous segment of the internal carotid artery (ICA). This paper aims to optimize imaging of the petrous ICA through optimized acquisition parameters. The petrous segment of the ICA is located in the parasellar region, where the large susceptibility difference between air and bone leads to susceptibility artifacts. These artifacts affect the homogeneity of both the B0 and B1 fields, which can result in asymmetry of TOF signals between the two sides. Even B0 shimming and volume-specific parallel-transmit (pTX) B1 shimming could not fully resolve the signal loss at the ICA. The optimization strategy was revised by altering the flow compensation scheme and increasing the acquisition bandwidth, therefore shortening the echo time (TE) and reducing the influence of T2* effects. Furthermore, changing the phase-encoding direction redirected pulsation artifacts away from critical vascular structures. Together, these approaches minimized the impact of susceptibility and pulsation artifacts in this region and led to a better display of the ICA on the TOF-MRA. The figures show a 77-year-old male with atherosclerosis. Visual inspection of the original TOF-MRA images revealed the following findings: 1. Shorter TE values exhibit superior efficacy in suppressing vascular pulsation artifacts. 2. Reduced TE improved homogeneity of the blood flow signal. 3. Under conditions of pronounced pulsation artifacts, P>>A (posterior-to-anterior) phase-encoding orientation effectively prevents cross-vessel interference induced by pulsation-related artifacts.

To date, 7T TOF-MRA has shown value in the evaluation of cerebrovascular malformations, atherosclerosis, and neurodegenerative diseases. However, it also faces challenges such as susceptibility artifacts at the air-bone interface of the sella turcica region, and physiological motion (e.g., vascular pulsation), which lead to suboptimal imaging of the petrous segment of the internal carotid artery (ICA). This paper aims to optimize imaging of the petrous ICA through optimized acquisition parameters. The petrous segment of the ICA is located in the parasellar region, where the large susceptibility difference between air and bone leads to susceptibility artifacts. These artifacts affect the homogeneity of both the B0 and B1 fields, which can result in asymmetry of TOF signals between the two sides. Even B0 shimming and volume-specific parallel-transmit (pTX) B1 shimming could not fully resolve the signal loss at the ICA. The optimization strategy was revised by altering the flow compensation scheme and increasing the acquisition bandwidth, therefore shortening the echo time (TE) and reducing the influence of T2* effects. Furthermore, changing the phase-encoding direction redirected pulsation artifacts away from critical vascular structures. Together, these approaches minimized the impact of susceptibility and pulsation artifacts in this region and led to a better display of the ICA on the TOF-MRA. The figures show a 77-year-old male with atherosclerosis. Visual inspection of the original TOF-MRA images revealed the following findings: 1. Shorter TE values exhibit superior efficacy in suppressing vascular pulsation artifacts. 2. Reduced TE improved homogeneity of the blood flow signal. 3. Under conditions of pronounced pulsation artifacts, P>>A (posterior-to-anterior) phase-encoding orientation effectively prevents cross-vessel interference induced by pulsation-related artifacts.

Optimization of Petrous Internal Carotid Artery Imaging in #7T Ultra-High-Field TOF-MRA by Hui Liu, Ph.D. (Siemens Healthineers, Zhengzhou, China).
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#MRI #NeuroSky #MRA #VesselImaging #UHF #UltraHighField

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