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High resolution renal diffusion imaging using a modified steady-state free precession sequence
1NMR Research Center, Department of Diagnostic Radiology, Dartmouth-Hitchcock Medical Center, Hanover, New Hampshire, USA.
Abstract:
A modified steady-state free precession (SSFP) diffusion sequence is proposed for high resolution renal imaging. A pair of bipolar diffusion gradients was used to minimize the errors in measured apparent diffusion coefficient (ADC) caused by variations in T1, T2, and RF flip angle that have been observed with previously employed SSFP diffusion sequences. Motion sensitivity was reduced by the use of compensated gradients, frame-by-frame averaging, and a repetition time of 22 ms, which for a single-acquisition 128 x 128 image requires only 3 s. High resolution was achieved by signal averaging. The modified sequence was applied to in vivo diffusion measurements. In six normal rat kidneys the ADCs (mean +/- SD; x 10(-3) mm2/s) of the cortex, outer medulla, and inner medulla were 2.28 +/- 0.05, 2.38 +/- 0.10, and 2.95 +/- 0.05, respectively. The technique requires relatively large gradients to achieve adequate diffusion weighting.
Insights
This study introduces a new diffusion imaging sequence for high-resolution kidney scans. The modified sequence accurately measures apparent diffusion coefficients (ADCs) in rat kidneys, reducing errors from common imaging variations.
Area of Science:
- Magnetic Resonance Imaging
- Biomedical Engineering
- Nephrology
Background:
- Steady-state free precession (SSFP) diffusion sequences are used for renal imaging.
- Existing SSFP diffusion sequences can suffer from errors due to T1, T2, and RF flip angle variations.
- Motion sensitivity is a challenge in fast imaging sequences.
Purpose of the Study:
- To develop a modified SSFP diffusion sequence for high-resolution renal imaging.
- To minimize errors in apparent diffusion coefficient (ADC) measurements.
- To reduce motion sensitivity in diffusion-weighted renal imaging.
Main Methods:
- A modified SSFP diffusion sequence utilizing bipolar diffusion gradients was developed.
- Compensated gradients, frame-by-frame averaging, and a short repetition time (22 ms) were employed.
- High resolution was achieved through signal averaging.
Main Results:
- The modified sequence successfully applied to in vivo diffusion measurements in rat kidneys.
- Accurate ADC values were obtained for the renal cortex, outer medulla, and inner medulla.
- The technique demonstrated reduced sensitivity to variations in T1, T2, and RF flip angle.
Conclusions:
- The modified SSFP diffusion sequence offers a robust method for high-resolution renal diffusion imaging.
- This technique improves the accuracy of ADC measurements in the kidney.
- Further development may involve optimizing gradient strength for enhanced diffusion weighting.