Related Experiment Videos
Multiple spin-echo MR imaging of the body: image contrast and motion-induced artifact
D G Mitchell1, S Vinitski, D L Burk
1Thomas Jefferson University Hospital, Department of Radiology, Philadelphia, Pennsylvania 19107.
Abstract:
For a given TR and TE, image quality changes when the number of spin echoes obtained is varied. To investigate the importance of this in clinical imaging, a total of 4 patients and 9 volunteers had MRI examinations of the abdomen (n = 7) and/or pelvis (n = 8) which included at least 2 sequences with identical TR (2000 or 2500 ms), TE (80 ms) and other parameters, but with a different series of refocusing pulses. Sequences included single-echo (S), asymmetric and symmetric double-echo (AD and SD) and quadruple-echo (Q) techniques. Image contrast and severity of motion-induced artifact was measured via blind examination by 3 independent MRI radiologists and calculation of signal-difference, signal-difference-to-noise ratios and intensity of motion-induced "ghost artifact." The order of decreasing signal differences was S, SD, AD and Q, and all of three liver lesions were better seen with S than with SD techniques. These observations are consistent with signal loss from cumulative inaccuracies from multiple 180 degrees RF pulses. The order of increasing intensity of ghost artifact was Q, SD, AD and S, consistent with the beneficial motion artifact-reducing effects of even-echo rephasing. Knowledge of these effects of multi-echo imaging allows one to make informed decisions about imaging protocols rather than to simply obtain multiple echoes "because they are free."
Insights
Varying the number of spin echoes in MRI affects image quality. Single-echo sequences offer better contrast and lesion visualization than multi-echo techniques, despite increased motion artifacts.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Medical Imaging Physics
Background:
- Image quality in MRI is influenced by sequence parameters, including the number of spin echoes.
- Multi-echo techniques are often employed, but their impact on contrast and artifacts requires careful consideration.
Purpose of the Study:
- To investigate how varying the number of spin echoes impacts image quality in abdominal and pelvic MRI.
- To compare contrast and motion artifact levels between single-echo, double-echo, and quadruple-echo sequences.
Main Methods:
- MRI examinations of the abdomen/pelvis were performed on 4 patients and 9 volunteers.
- Identical TR/TE parameters were used across single-echo (S), asymmetric double-echo (AD), symmetric double-echo (SD), and quadruple-echo (Q) sequences.
- Image contrast and motion artifacts were assessed by blinded radiologists and quantified using signal-difference and ghost artifact intensity measurements.
Main Results:
- Signal differences decreased in the order: S > SD > AD > Q.
- Liver lesions were better visualized with single-echo sequences compared to double-echo.
- Motion artifact intensity increased in the order: Q < SD < AD < S, indicating beneficial motion reduction with even-echo rephasing.
Conclusions:
- Single-echo sequences provide superior contrast and lesion detection compared to multi-echo sequences due to signal loss in the latter.
- Multi-echo imaging, particularly even-echo rephasing, effectively reduces motion artifacts.
- Informed selection of MRI protocols based on these trade-offs is crucial for optimizing diagnostic image quality.