MRI - Terminology - CBI:
Overview of Siemens pulse sequence names.
Spin Echo: Uses both a 90 degree and 180 degree RF pulse. Varying the TR and TE can produce images with T1-, Proton Density- or T2-weighting.One of the first MR imaging sequences developed.
Fast Spin Echo: Uses multiple 180 degree RF pulsed to produce a series of echoes (the echo “train”) and allows a significant time reduction compared to SE imaging. FSE images are generally T2-weighted, but T1-weighted images are possible with very short echo trains (typically 3-5 echoes). Also know as Turbo Spin Echo.
Flash: Fast Low Angle SHot. A spoiled gradient echo sequence that allows very short TR values and is often used for rapid T1-weighted images.
MP-RAGE: (Magnetization Prepared Rapid Acquisition Gradient Echo) Allows the user to collect high-resolution (1mm isotropic) 3D anatomical images with T1 weighted contrast at ultra high 3T field strengths.
FISP: A steady-state gradient echo imaging technique that is used in cardiac imaging. It produces a mix of T1 and T2 contrast.
PSIF: A steady-state imaging technique that produces T2* weighted images.
EPI (Echo Planar Imaging): A high-speed imaging technique that uses rapid gradient switching to acquire images of the head during functional imaging. The entire brain set (i.e., 30 slices) can be acquired within about 30 milliseconds and reacquired repeatedly every 1 to 2 seconds for up to 20 minutes in a single fMRI session.
Time-of-Flight: An MR Angiography technique that is used to image flowing blood without using contrast agents. Background tissue signals are suppressed (dark on the image) and blood flowing into the imaging volume shows high signal intensity (bright). This technique can be used in 2 or 3 Dimensional scans.
Phase Contrast: A technique used in MR angiography to produce images that show the difference in phase shifts between flowing and stationary protons.
DENSE: vascular imaging (developed by Dr. Han Wen at MGH)
Spectroscopy: A technique used to measure the chemical composition of the area being imaged. Pathology, such as tumors, often has a different chemical makeup than normal tissues and spectroscopy can be used to detect abnormalities.
Multi-Echo SE: Up to 32 echoes can be collected during a single scan to provide an array of image contrasts or to study T2 decay.
Respiratory Gating: Scans can be designed to collect data only when a subject is at a particular part of the respiratory cycle, such as inspiration or expiration, to help reduce motion artifacts for longer duration scans. A collapsible bellows is attached to the chest or abdomen to monitor movement during the scan. The scanner waits until the desired part of the respiratory cycle occurs and scan data is then collected.
Cardiac Gating: Moving heart muscle and flowing blood in major vessels can cause motion artifacts on MR images. By timing the period of data collection to coincide with the quiet phase of the cardiac cycle, these artifacts can be eliminated or reduced. Gating can also be used when imaging the heart itself. Images can be collected at specific points in the cardiac cycle and allow investigators to view heart wall motion or valve function.
Breathhold: Can be used to eliminate respiratory motion for short duration 2D anatomical scans. These scans are commonly used when imaging the abdomen and thorax.
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