Immobilization and Optimization of Pulse Sequences for 0.23T MRI πŸ“

Author: Soon N. Huh, Perry B. Johnson, Jiyeon Park, Ryan Stevens πŸ‘¨β€πŸ”¬

Affiliation: University of Florida Health Proton Therapy Institute, UF Health Proton Therapy Institute, UFHPTI 🌍

Abstract:

Purpose:
It has been challenging to acquire clinically useful MR images of pediatric cancer patients without anesthesia, and MR contrast agents. Custom-made immobilization devices and optimization pulse sequences of B-FFE3D were implemented, reducing scanning time. Image quality was not sacrificed to acquire MR images for contouring, and tumor progression of pediatric patients (under 6 years-of-age).
Methods:
Two sets of immobilization techniques: using blood pressure cuffs and MR-safe headset. Blood pressure cuffs are modified, and patient heads are compressed laterally with the earmuffs on both ears. The headset is fabricated by removing all the electronics. The speaker is placed in plastic bag and controlled by Bluetooth located in control room through ducts in concrete walls. Waffled plastic tubes (3cm diameter) and waffled pipe was used to improve fidelity of music or story transmitted by speaker. The waffled plastic pipe connected to the headset with volume control (acoustic noises depend upon specific pulse sequences of scanning protocol, mainly determined by pulse repetition times, and patient’s personal tolerance). Head-set was placed inside head coil of MR scanner. Susceptibility artifacts from casing of headset were tested with routine water phantom to detect artifacts.
Results:
Management system is effective to minimize motions during scan. Artifact-free MRI has been acquired to evaluate tumor progression with excellent resolution on current protocol. As a routine protocol with T1FFE3D (TR=21msec, and TE=8.0msec, scan time = 3 minutes-per-scan) and B-DDE3D (TR=9.6msed, TE-4.8msec, Flip Angle=60) had been chosen to optimize excellent resolution.
Conclusion:
Pediatric cancer patients under 6 years-of-age tolerated well while using the device. Clinically useful MR images had been acquired. CT/MR compatible compression devices were invented to acquire motions-free MR for determination of iGTV margins, with aid of CBCT.

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