Fat suppression techniques in breast magnetic resonance imaging: a critical comparison and state of the art

Abstract

Robust and accurate fat suppression is highly desirable in breast magnetic resonance imaging (MRI) because it can considerably improve the image quality and lesion conspicuity. However, fat suppression is also more challenging in the breast compared with other regions in the body. Technical advances have been made over time to make fat suppression more efficient and reliable. Combined with other innovations, breast MRI continues to be the most sensitive and comprehensive diagnostic modality in the detection and evaluation of breast lesions. This review offers a critical comparison of various fat suppression techniques in breast MRI including spectral-selective excitation and saturation techniques based on the chemical shift difference between fat and water, the inversion recovery techniques based on the T1 relaxation time difference, the hybrid spectral-selective inversion recovery techniques, and the new Dixon fat and water separation techniques based on the phase difference between fat and water signal at different echo times. This review will also cover less frequently used techniques such as slice-selective gradient reversal. For each fat suppression technique in breast MRI, a detailed explanation of the technical principle, the advantages and disadvantages, the approaches for optimization as well as the clinical examples are included. The additional challenges of fat suppression in breast MRI at higher field strength and in the presence of metallic and silicone implants are also discussed.

An intraoperative MRI system for margin assessment in breast conserving surgery: Initial results from a novel technique

“…Each sample was taken from different areas of the lumpectomy specimen by the pathologist, following an on‐site, real‐time, macro‐pathology assessment, in order to obtain a variety of tissue types. The individual tissue samples were then analyzed by the system, which determined the T2* value utilizing a fat suppression technique . The calculated T2* values were correlated with final histopathology results.…”

Improved visualization of the lumbar spine nerve roots in dogs using water excitation (ProSet) as opposed to short tau inversion recovery: A retrospective study of two fat suppression MRI sequences

“…Water excitation techniques use a series of small radiofrequency pulses, with specific interpulse delay (composite pulses) in order to enhance the chemical shift effect of fat and water . The sequence scheme using composite pulses can be variable and can be a pair (1:1), a triplet (1:2:1), or a quadruplet (1:3:3:1) . With radiofrequency pulse of 90° and a sequence scheme of 1:2:1, the first radiofrequency pulse (22.5°) is applied and fat and water start dephasing.…”

“…As result, fat will be along the longitudinal and water along the transverse axis, thus, allowing only water molecules to contribute to the signal formation while recovering. By using a 1:3:3:1 scheme, the preparatory 90° radiofrequency pulse is subdivided in four smaller angles (11.25°‐33.75°‐33.75°‐11.25°) providing a more efficient water and fat separation and lower susceptibility to field inhomogenicities, although slightly increasing the acquisition time . Water excitation is also a slice selective technique, which provides suppression in a specific slice unlike inversion recovery techniques, such as STIR, that can only be applied to the whole volume at the same time.…”

Calculation of Inversion Time (TI) value for Fat suppression in the modified Spin Echo sequence method

“…This results in fat being shifted relative to water in an image and is called the chemical shift artefact δ. [13][14][15] This is described in terms of frequency as follows δ = ( Δf/ fo ) 10 6 (1)…”

“…Here the aim was to find the appropriate value of the inversion time (TI), for use in the modified spin echo sequence, which would suppress the contribution from the fat. [13][14][15] …”