Low-field Disadvantages
Aren't there some major disadvantages to lower field strength scanners?
|
|
Of course! There are always trade-offs, and here are four of the most significant:
1) Lower signal-to-noise. Although a number of complex factors determine image quality, signal-to-noise is approximately proportional to field strength. All other things being equal, therefore, the signal-to-noise ratio will be smaller in a lower-field scanner. Consequently, to maintain equivalent signal-to-noise, more signal averages and longer imaging times will be necessary in a lower-field scanner.
2) Lower homogeneity. The main magnetic fields of permanent and resistive scanners is significantly less uniform (homogeneous) than that of superconducting scanners. This impairs image quality especially over large fields-of-view and limits the ability to perform certain pulse sequences (such as chemical shift fat suppression, echo-planar imaging, and MR spectroscopy)
3) Impaired detection of calcifications and hemorrhage. Susceptibility artifacts are proportional to field strength, and although this may be an advantage for lower-field scanners for reduced metal artifacts, it may also be a disadvantage as well. In particular, lower-field units are inferior to high-field scanners in their ability to detect focal areas of calcification, iron accumulation, or hemorrhage in tissue.
4) Reduced detection of gadolinium enhancement. Gadolinium enhancement is less apparent at lower than higher fields, requiring relatively higher doses of gadolinium contrast to be administered for the same relative enhancement.
1) Lower signal-to-noise. Although a number of complex factors determine image quality, signal-to-noise is approximately proportional to field strength. All other things being equal, therefore, the signal-to-noise ratio will be smaller in a lower-field scanner. Consequently, to maintain equivalent signal-to-noise, more signal averages and longer imaging times will be necessary in a lower-field scanner.
2) Lower homogeneity. The main magnetic fields of permanent and resistive scanners is significantly less uniform (homogeneous) than that of superconducting scanners. This impairs image quality especially over large fields-of-view and limits the ability to perform certain pulse sequences (such as chemical shift fat suppression, echo-planar imaging, and MR spectroscopy)
3) Impaired detection of calcifications and hemorrhage. Susceptibility artifacts are proportional to field strength, and although this may be an advantage for lower-field scanners for reduced metal artifacts, it may also be a disadvantage as well. In particular, lower-field units are inferior to high-field scanners in their ability to detect focal areas of calcification, iron accumulation, or hemorrhage in tissue.
4) Reduced detection of gadolinium enhancement. Gadolinium enhancement is less apparent at lower than higher fields, requiring relatively higher doses of gadolinium contrast to be administered for the same relative enhancement.
Related Questions
How many brands of scanners are there?
How many brands of scanners are there?