Ces radiol. 2008, 62(3):233-243

MR imaging in magnetic field of 3 T: theoretical aspects and practical comparisonOriginal article

Jaroslav Tintěra

Základna radiodiagnostiky a intervenční radiologie IKEM, Praha

Aim: In recent years, remarkable increase in number of newly installed MR system with high magnetic field 3 T and also an increase of the interest of high field systems generally can be seen. Very often only the advantages of high-field imaging are emphasized which can lead to raw simplification that high field systems are generally "better". This contribution tries to put the argumentation as closed as possible to current reality using both theoretical physical effects and also by means of own direct comparison of examinations of various body parts.

Method: Examination protocols with very similar image contrast and identical acquisition time were compared on MR systems Siemens Avanto 1.5 T and Trio 3 T equipped with the same hardware as well as software.

Results: Brain MR imaging clearly profits from high magnetic field mainly due to increase of SNR but also due longer T1 relaxation time when performing MR angiography or due to enhanced BOLD effect in functional MR imaging. However, examination of the spine on 3 T has not only advantages because of SAR limitations and also due to CSF pulsation and chemical shift artifacts. High level of SAR causes also problems in chest and abdominal region; moreover images can suffer from inhomogeneity due to dielectric resonance and local magnetic field inhomogeneity. On the contrary, imaging of pelvis region and musculoskeletal system can significantly profit from increased SNR.

Conclusion: The growth of SNR at 3T leads generally to possible higher spatial resolution and/or shorter acquisition time. However, number of other physical aspects influences the examination in positive but also in negative sense.

Keywords: high-field-strength MR system, MR imaging

Accepted: July 17, 2008; Published: September 1, 2008  Show citation