Related Experiment Videos
Quantitative diffusion coefficient maps using fast spin-echo MRI
S Brockstedt1, C Thomsen, R Wirestam
1Department of Radiation Physics, Lund University Hospital, Sweden. Sara.Brockstedt@radfys.lu.se
Abstract:
In this work, we have evaluated the performance of a diffusion-sensitive fast spin-echo (FSE) pulse sequence. The proposed pulse sequence utilises velocity-compensating diffusion-encoding gradients and includes the collection of navigator echoes. Spoiler gradients were inserted in the slice-selecting direction to minimise effects from stimulated echoes. Calculations of the b values showed that cross-terms between imaging gradients and diffusion gradients only led to a marginal increase of b values. Pixel-wise calculation of apparent diffusion coefficient (ADC) maps was performed numerically, considering cross-terms between diffusion-encoding and imaging gradients. The sequences investigated used echo train lengths of 16, 8 and 4 echoes and were encoded in either the slice-, frequency- or phase-encoding direction. In order to allow for higher b values a pulse-sequence version using non-motion compensating diffusion-encoding gradients was written. Phantom measurements were performed and the diffusion coefficients of water and acetone were reasonable. Seven healthy volunteers (age 28-50 years) were examined and apparent diffusion coefficient values agreed well with expected values. Diffusion-weighted images, apparent diffusion coefficient maps and images corresponding to the trace of the diffusion tensor of good quality were retrieved in vivo.
Insights
This study evaluated a new diffusion-sensitive fast spin-echo (FSE) pulse sequence for improved MRI. The sequence accurately measured apparent diffusion coefficients (ADC) in phantoms and healthy volunteers.
Area of Science:
- Magnetic Resonance Imaging
- Diffusion MRI
- Pulse Sequence Development
Background:
- Fast spin-echo (FSE) sequences are crucial for reducing scan times in MRI.
- Optimizing diffusion-sensitive FSE sequences is essential for accurate apparent diffusion coefficient (ADC) mapping.
- Minimizing artifacts from stimulated echoes and gradient cross-terms is a key challenge.
Purpose of the Study:
- To evaluate the performance of a novel diffusion-sensitive FSE pulse sequence.
- To assess the impact of velocity-compensating diffusion-encoding gradients and navigator echoes.
- To investigate the accuracy of ADC quantification with this sequence.
Main Methods:
- Developed and implemented a diffusion-sensitive FSE pulse sequence with velocity-compensated gradients and navigator echoes.
- Incorporated spoiler gradients to minimize stimulated echo effects.
- Performed pixel-wise ADC map calculations, accounting for gradient cross-terms.
- Tested sequences with varying echo train lengths (16, 8, 4) and encoding directions.
- Utilized a version with non-motion compensating gradients for higher b values.
- Conducted phantom studies with water and acetone.
- Acquired in vivo data from seven healthy volunteers.
Main Results:
- Calculated b values showed only marginal increases due to gradient cross-terms.
- Phantom measurements yielded reasonable diffusion coefficients for water and acetone.
- In vivo apparent diffusion coefficient values in healthy volunteers aligned with expected values.
- High-quality diffusion-weighted images, ADC maps, and trace images were obtained.
Conclusions:
- The evaluated diffusion-sensitive FSE pulse sequence demonstrates good performance for in vivo diffusion MRI.
- The sequence provides accurate ADC measurements and high-quality diffusion imaging.
- This technique holds promise for clinical applications requiring efficient and accurate diffusion quantification.