What is Spir sequence?
SPIR sequence combines features of CHESS (fat-selective RF pulse + spoiler) and STIR (inversion recovery nulling of fat signal). SPIR stands for “Spectral Presaturation with Inversion Recovery” and is pictured right.
What is PD sequence in MRI?
Proton density (PD) image characteristics. When an MRI sequence is set to produce a PD-weighted image, it is the tissues with the higher concentration or density of protons (hydrogen atoms) which produce the strongest signals and appear the brightest on the image.
What does fat sat mean MRI?
fat saturation A specialised MRI technique which selectively saturates fat protons before acquiring data, as in standard sequences, to reduce fat signal. The pre-saturation pulse is applied before each slice selection. Fat saturation requires a homogeneous magnetic field and precise frequency calibration.
When do you use fat sat MRI?
They are applied immediately before the start of an MR imaging sequence. These chemically selective pulses cause the signal from fat to be nulled (saturated) while the water signal is relatively unaffected. The Fat-Sat technique is the most widely used method for fat suppression.
How does fat appear on MRI?
On T1-weighted images, tissues with short T1 times (like subcutaneous fat or fatty bone marrow) appear bright; tissues with long T1 times (like fluid) appear dark. Solids (like cortical bone) also appear dark. If “fat saturation” is used, fat will appear dark on a T1-weighted image.
What is T1 and T2?
T1 and T2 are technical terms applied to different MRI methods used to generate magnetic resonance images. Specifically, T1 and T2 refers to the time taken between magnetic pulses and the image is taken. These different methods are used to detect different structures or chemicals in the central nervous system.
What is T1 flair?
T1-FLAIR stands for T1-weighted-Fluid-Attenuated Inversion Recovery. This nomenclature began to arise in the late 1990s to denote an inversion recovery sequence with dark CSF and other T1-like properties made possible by a medium TI coupled with fast spin-echo signal acquisition.
How is fat suppression used in magnetic resonance imaging?
Fat suppression is commonly used in magnetic resonance (MR) imaging to suppress the signal from adipose tissue or detect adipose tissue 1 . It can be applied to both T1 and T2 weighted sequences. Due to short relaxation times, fat has a high signal on magnetic resonance images (MRI). This high signal, easily recognized on MRI,
Can you use opposed phase imaging to detect FAT?
However, this technique is not specific for fat, and the signal intensity of tissue with a long T1 and tissue with a short T1 may be ambiguous. Opposed-phase imaging is a fast and readily available technique. This method is recommended for demonstra- tion of lesions that contain small amounts of fat.
Where does the fat come from in MR imaging?
During an MR imaging acquisition, two different components produce a signal from white fat: protons from lipids (>80% of the signal) and protons from hydrogen atoms in water located within loose connective tissue (<20% of the signal) (, 3 ).
Which is the best technique for fat suppression?
Selection of a fat suppression technique should depend on the purpose of the fat suppression (contrast enhancement vs tissue characterization) and the amount of fat in the tissue being studied. Fat saturation is recommended for suppression of signal from large amounts of fat and reliable acquisition of contrast material–enhanced images.
