The Application of Fat-Suppression MR Pulse Sequence in the Diagnosis of Bone-Joint Disease

Jing Wu, Ling-Quan Lu, Jian-Ping Gu, Xin-Dao Yin

Department of Radiology, Nanjing Hospital, Nanjing Medical University, Nanjing, China.

DOI: 10.4236/ijmpcero.2012.13012                

Abstract

Fat-suppression technology of magnetic resonance is very important in clinical practice.This article is written to interpret the principle, advantages/disadvantages and clinical applications of some regular fat-suppression sequences in the diagnosis of Bone-Joint Disease, including 1) frequency-selective saturation (FS); 2) short-TI inversion recovery (STI-R); 3)frequency selective inversion pulse; 4) fat suppression water or fat selective excitation technique; 5) Dixon technology and 6) magnetization transfer contrast (MTI).

Keywords

Magnetic Resonance Imaging; Fat Suppression Sequences; Bone Joint

1. Introduction

Fat tissue contains amount of hydrogen protons which show high signal in both T1-weighted imaging (T1WI) and T2-weighted imaging (T2WI) sequence, which not only cover the signal of other tissues, but also produce chemical shift artifact. Fat suppression MR pulse sequence can suppress the signal from adipose tissue, so it can be used in routine magnetic resonance imaging in order to reduce chemical shift artifact and improve visualization of uptake of contrast material. Now this imaging sequence is also significant in the diagnosis of musculoskeletal diseases. This article is written to describe the principles of these different kinds of fat-suppression MR sequences and their applications for the musculoskeletal system.

2. Commonly Used Fat-Suppression MR Sequences

2.1. Frequency-Selective Saturation (FS)

Procession frequency of protons in fat is different from that in water molecules. A frequency-selective saturation radio-frequency pulse with the same resonance frequency as that of lipids is applied at first, then a homogeneity spoiling gradient pulse is applied immediately. Thus, the signal we get contains no contribution from lipid [1]. This method can be used in any MR imaging sequence, such as TIWI, T2WI, and PDWI (FS-T1WI, FS-T2WI, FS-PDWI). FS-T2WI has advantage in spine, joints of extremities and Minor Joints, especially has high value in the diagnosis of vertebral body occult fractures, thus can used as a routine sequence for spinal trauma [2]. While FS-PDWI is commonly used in joints of extremities, such as knee joint. It has advantage in the detecting the occult fractures of extremities, especially with Bone Contusion, ligament, tendon and menisci injury [3,4]. This fat suppression is specific, for it can get complete suppression of lipid signal, so signal in nonadipose tissue is practically unaffected as long as the saturation pulse frequency and bandwidth are properly selected. But this method has a high demand for magnetic field homogeneity, so it can only be used MR instruments with highfield-strength magnets; in the large FOV scan, the effect of fat suppression is poor in peripheral region. It is only applied to small-FOV examinations such as head, neck, spine imaging and minor joints of extremities imaging. Also it increases the scanning time and specific absorption rate (SAR) value as well.

Figure 1 FS-T2WI has advantage in knee joint, which can detect the occult fractures of knee, especially with bone contusion, ligament, tendon and menisci injury.

Conflicts of Interest

The authors declare no conflicts of interest.

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