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Short versus long echo time for cranial MR angiography in children and adults
1Department of Radiology, University Hospitals of Cleveland, OH.
Purpose:
To evaluate the ability of short-echo-time (TE) versus long-TE three-dimensional time-of-flight MR angiography sequences to decrease phase-related signal loss and refocus signal from blood in intracranial MR angiography of adults and children.
Methods:
We evaluated 3-D time-of-flight cranial MR angiography in 33 cases (18 children and 15 adults) using two sequences. The longer-echo reference sequence had a TE of 8.0 milliseconds and a field echo of 6.5 milliseconds; the shorter-echo sequence had a TE of 5.1 and a field echo of 4.2 milliseconds. Repetition time, flip angle, and matrix were constant. The bandwidth for the longer-echo sequence was 130 Hz, 195 Hz for the shorter-echo sequence.
Results:
The greatest improvement in diagnostic images was for children; significant and mildly improved signal recovery was demonstrated in 15 and 2 cases, respectively, of a total of 18 studies. This allowed improved diagnostic assessment. However, in the adult group significantly and mildly improved signal recovery were present in only 2 and 6 cases, respectively, of a total of 15 studies. In the group of children and adults combined, decreased lumen definition and peripheral vessel visibility were present in 24 and 30 of 33 cases, respectively, because of higher signal from background tissue when the shorter-TE field-echo sequence was used and, hence, reduced vascular contrast.
Conclusion:
The use of a short-field-echo/TE sequence is therefore recommended as the initial study in children but as a secondary examination in areas of abnormality in adults. This study illustrates the improved signal recovery from phase-related sources and improved visibility of intracranial stenosis in children with the use of a short-echo sequence. In adults, the short-echo sequence should not be used for the initial screening but reserved for secondary evaluation.
Insights
Short echo-time MR angiography sequences improve intracranial vessel imaging in children. For adults, short echo-time sequences are best for secondary evaluations of abnormalities, not initial screening.
Area of Science:
- Radiology
- Medical Imaging
- Neuroimaging
Background:
- Intracranial MR angiography (MRA) is crucial for diagnosing vascular conditions.
- Phase-related signal loss can degrade image quality in MRA.
- Optimizing MRA sequences is essential for accurate diagnosis in both pediatric and adult populations.
Purpose of the Study:
- To compare short-echo-time (TE) versus long-TE 3D time-of-flight (TOF) MRA sequences.
- To evaluate the ability of these sequences to reduce signal loss and improve blood signal refocusing in intracranial MRA.
- To assess performance in both pediatric and adult patients.
Main Methods:
- Evaluated 33 cases (18 children, 15 adults) using two 3D TOF MRA sequences.
- Compared a long-TE sequence (TE 8.0 ms) with a short-TE sequence (TE 5.1 ms).
- Maintained constant repetition time, flip angle, and matrix; varied bandwidth (130 Hz vs. 195 Hz).
Main Results:
- Significant signal recovery and improved diagnostic assessment were observed in 15/18 pediatric cases.
- Adults showed less improvement, with significant and mild signal recovery in only 2/15 and 6/15 cases, respectively.
- Shorter TE sequences led to decreased lumen definition and vessel visibility in 24/33 combined cases due to increased background signal.
Conclusions:
- Short-echo-time/TE sequences are recommended for initial intracranial MRA in children.
- In adults, short-echo sequences are better suited for secondary evaluation of specific abnormalities.
- Short-echo sequences enhance signal recovery and intracranial stenosis visibility in children, but require careful consideration in adults.