Evaluating Signal Uniformity and Spin Relaxation of Several Laboratory-Based MRI Phantoms

  • N. Mohd Sebri Universiti Kebangsaan Malaysia
  • H. Y. Heah Universiti Kebangsaan Malaysia
  • Y. Dwihapsari Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia
  • M. N. A. Awang Universiti Kebangsaan Malaysia
  • A. N. Yusoff Universiti Kebangsaan Malaysia

Abstract

Many studies have been carried out to develop homogenous and stable MRI phantoms using inexpensive and non-hazardous materials that can mimic human tissues. In this study, three phantoms were prepared in the laboratory, namely polyvinyl alcohol (PVA) phantom, Gd2O3-added PVA phantom and Gd2O3-added agarose gel phantom to evaluate signal uniformity and spin relaxation. The phantoms were scanned using a 3-T magnetic resonance imaging (MRI) machine via spin echo (SE) and turbo spin echo (TSE) sequences to acquire T1- and T2-measurement images. Signal intensity and background noise for the three samples at different repetition times (TR) and echo times (TE) were computed using Image-J software. The average signal-to-noise ratio (SNR) of all phantoms was computed from 25 regions of interest (ROIs) on the image of the middle slice. The SNR vs TR and SNR vs TE curves were fitted to the equations of SNR µ 1 – e-TR/T1 and SNR ∝ e-TE/T2 using curve fitting technique to determine the relaxation and saturation constants. The addition of relaxation modifier in the phantom matrix increased the magnetic field inhomogeneity and fluctuation which resulted in shortening the T1 and T2 values. The effects were more prominent on T1 curve which flattened towards longer TR with a reduction of T1 from 2530.0 ms to 145.3 ms for PVA phantom. A higher water content in agarose gel led to higher saturation (SNRo = 348.7) and longer relaxation during both T1 and T2 processes (T1 = 222.0 ms, T2 = 148.8 ms) compared to PVA phantoms (SNRo= 252.5, T1 = 145.3 ms, T2 = 96.0 ms). The findings also showed that SNR and relaxation of the T1 and T2 curves were better studied using a smaller number of ROI with s3ROI < s25ROI for all phantoms.

Author Biographies

N. Mohd Sebri, Universiti Kebangsaan Malaysia

Undergraduate Student, Diagnostic Imaging and Radiotherapy Program, Faculty of Health Science, Universiti Kebangsaan Malaysia, 50300 Jalan Raja Muda Abdul Aziz, Kuala Lumpur, Malaysia

H. Y. Heah, Universiti Kebangsaan Malaysia

Undergraduate Student, Diagnostic Imaging and Radiotherapy Program, Faculty of Health Science, Universiti Kebangsaan Malaysia, 50300 Jalan Raja Muda Abdul Aziz, Kuala Lumpur, Malaysia

Y. Dwihapsari, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia

Academician/Researcher, Department of Physics, Institut Teknologi Sepuluh Nopember Surabaya(ITS), Kampus ITS Sukolilo, Surabaya 60111 Indonesia

M. N. A. Awang, Universiti Kebangsaan Malaysia

Department of Radiology, Hospital Canselor Tuanku Muhriz, Universiti Kebangsaan Malaysia, 56000 Jalan Yackob Latif, Bandar Tun Razak,  Kuala Lumpur, Malaysia

A. N. Yusoff, Universiti Kebangsaan Malaysia

Researcher, Center for Diagnostic, Therapeutic and Investigative Studies, Faculty of Health Science, Universiti Kebangsaan Malaysia, 50300 Jalan Raja Muda Abdul Aziz, Kuala Lumpur, Malaysia

Published
2021-10-27
How to Cite
MOHD SEBRI, N. et al. Evaluating Signal Uniformity and Spin Relaxation of Several Laboratory-Based MRI Phantoms. Physics and Technology in Medicine, [S.l.], v. 2, n. 1 & 2, p. 9-22, oct. 2021. ISSN 2710-723X. Available at: <https://myjms.mohe.gov.my/index.php/ptm/article/view/13221>. Date accessed: 28 may 2022.