Optimization of high-resolution USPIO magnetic resonance imaging at 4.7 T using novel phantom with minimal structural interference
✍ Scribed by Henrik Antell; Jussi Numminen; Usama Abo-Ramadan; Mika R. Niemelä; Juha A. Hernesniemi; Marko Kangasniemi
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 705 KB
- Volume
- 32
- Category
- Article
- ISSN
- 1053-1807
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✦ Synopsis
Purpose: To characterize the effect of ultrasmall superparamagnetic iron oxides (USPIOs) on magnetic resonance imaging (MRI) signal at 4.7 T, and to find the highest sensitivity pulse sequence for high-resolution USPIO MRI.
Materials and Methods:
A novel phantom was constructed for optimization of sequence parameters for neuroradiological MR applications, and a wide range of dilutions of the USPIO ferumoxtran-10 was imaged using T 2 / T 1 -, T 1 -, T 2 -, T* 2 -, and PD-weighted sequences. The effect of varying sequence parameters was investigated using phantom measurements and simulations.
Results: The relaxivities r 1 , r 2 , and r* 2 of ferumoxtran-10 at 4.7 T (21 C) were 5.1, 82.2, and 148.4 mmol À1 L s À1 , respectively. Gradient echo sequences produced superior susceptibility artifacts at high concentrations; susceptibility artifacts were seen down to a concentration of 137 nmol Fe/mL. A concentration of 17.5 mmol Fe/mL caused a signal void independently of sequence and parameters, and at concentrations 273 nmol Fe/mL no signal void was caused. Signal enhancement on T 1 -weighted imaging was seen only at concentrations 137-547 nmol Fe/mL. For the same effective echo time T 2 -weighted rapid acquisition with relaxation enhancement (RARE) yielded significantly higher contrast-tonoise ratio with RARE factor 16 than with RARE factor 8.
Conclusion:
At nanomolar concentrations of USPIO, steady-state free precession offers an alternative to T 2 -and T* 2 -weighted sequences. Optimum parameters depend highly on USPIO concentration.