T1 AND T2 CHARACTERISTICS OF POLY(VINYL) ALCOHOL SLIME PHANTOM WITH DIFFERENT RELAXATION MODIFIER CONCENTRATIONS

Abstract

Many studies have been carried out to produce magnetic resonance imaging (MRI) phantom which is inexpensive, non-hazardous, easy to produce, mimic human tissue and has good SNR homogeneity. Among those that were studied were poly(vinyl) alcohol (PVA) slime phantoms. The characteristics of PVA slime phantom chosen for this study include naturally flexible, tough and has relaxation times close to human tissue. The objectives of this study were to investigate the T1 and T2 characteristics of the PVA slime phantom with different relaxation modifier (gadolinium (III) oxide, Gd₂O₃) concentrations and to determine its suitability as alternative to agarose gel phantom. Five PVA slime phantoms were prepared by mixing PVA and borax solution at a fixed ratio but with the addition of different quantity of Gd₂O₃. The T1 (fixed echo time (TE) and different repetition time (TR)) and T2 (fixed TR and different TE) weighted images of all phantoms including distilled water were acquired using SIEMENS Magnetom Verio 3-tesla MRI system at the Radiology Department, Hospital Canselor Tuanku Muhriz (HCTM) via spin echo (SE) and turbo spin echo (TSE) sequences respectively. The signal-to-noise ratio (SNR) of all phantoms was calculated using Image-J software (The National Institutes of Health, NIH) by implementing the region of interest (ROI) analysis. The SNR vs TR and SNR vs TE curves were fitted to the exponential equations for T1 and T2 relaxation using MATLAB® R2018b (The Math Works, Inc., Natick) to determine the T1, T2 and saturation (SNRo). For all phantoms, T1 curves demonstrated that the SNR increases exponentially with increasing TR (constant TE) while T2 curves showed that the SNR decreases exponentially with increasing TE (constant TR). Gd was found to affect the T1 but not 105 Solid State Science and Technology, Vol. 27, No 1 & 2 (2019) 105-121 ISSN 0128-7389 | http://myjms.moe.gov.my/index.php/masshp the T2 curves. SNRo, T1 and T2 relaxation times decrease with increasing Gd₂O₃ concentration. It can be concluded that with a systematic increase in the quantity of relaxation modifier, the T1 and T2 relaxation times decrease in a systematic manner. Further studies are necessary to investigate the stability of the PVA slime phantom over a long period of time.