In Vivo and In Vitro Studies of the Steady State Free Precession-Diffusion-Weighted MR Imagings on Low b-value : Validation and Application to Bone Marrow Pathology
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Purpose：The purpose of this study was a phantom study to measure the diffusion properties of water molecules by steady-state free precession diffusion-weighted imaging (SSFP- DWI) with a low b-value and to determine if this sequence might be useful for application to the evaluation of bone marrow pathology. Materials and methods：1. The phantom study: A phantom study using two diffusion weighted sequences for the evaluation of the diffusion coefficient was performed. Three water-containing cylinders at different temperatures were designed: phantom A was 3℃, B was 23℃ and C was 63℃. Both SSFP and echo planar imaging (EPI) sequences (b-value: 1000 s/mm2) were performed for comparison of the diffusion properties. The Signal to noise ratios (SNR) and apparent diffusion coefficient (ADC) values of the three phantoms using each diffusion-weighted sequence were assessed. 2. The Clinical study: SSFP-DWI was performed in 28 patients [sacral insufficiency fractures (10), osteoporotic lumbar compression fractures (10), malignant compression fractures (8)]. To measure the ADC maps, a diffusion-weighted single shot stimulated echo-acquisition mode sequence (650s/ mm2) was obtained using the same 1.5-T MR imager 1) Results：For the phantom study, the signal intensity on the SSFP as well as the classic EPI-based DWI was decreased as the temperature increased in phantom A to C. The ADC values of the phantoms on EPI-DWI were 0.13×10-3 mm2/s in phantom A, 0.22×10-3 mm2/s in B and 0.37×10-3 mm2/s. in C. The SSFP can be regarded as a DWI sequence in view of the series of signal decreases. Conclusion：Bone marrow pathologies with different diffusion coefficients were evaluated by SSFP-DWI. All benign fractures were hypointense compared to the adjacent normal bone marrow where as the malignant fractures were hyperintense compared to the adjacent normal bone marrow.
Abstract
Purpose：The purpose of this study was a phantom study to measure the diffusion properties of water molecules by steady-state free precession diffusion-weighted imaging (SSFP- DWI) with a low b-value and to determine if this sequence might be useful for application to the evaluation of bone marrow pathology. Materials and methods：1. The phantom study: A phantom study using two diffusion weighted sequences for the evaluation of the diffusion coefficient was performed. Three water-containing cylinders at different temperatures were designed: phantom A was 3℃, B was 23℃ and C was 63℃. Both SSFP and echo planar imaging (EPI) sequences (b-value: 1000 s/mm2) were performed for comparison of the diffusion properties. The Signal to noise ratios (SNR) and apparent diffusion coefficient (ADC) values of the three phantoms using each diffusion-weighted sequence were assessed. 2. The Clinical study: SSFP-DWI was performed in 28 patients [sacral insufficiency fractures (10), osteoporotic lumbar compression fractures (10), malignant compression fractures (8)]. To measure the ADC maps, a diffusion-weighted single shot stimulated echo-acquisition mode sequence (650s/ mm2) was obtained using the same 1.5-T MR imager 1) Results：For the phantom study, the signal intensity on the SSFP as well as the classic EPI-based DWI was decreased as the temperature increased in phantom A to C. The ADC values of the phantoms on EPI-DWI were 0.13×10-3 mm2/s in phantom A, 0.22×10-3 mm2/s in B and 0.37×10-3 mm2/s. in C. The SSFP can be regarded as a DWI sequence in view of the series of signal decreases. Conclusion：Bone marrow pathologies with different diffusion coefficients were evaluated by SSFP-DWI. All benign fractures were hypointense compared to the adjacent normal bone marrow where as the malignant fractures were hyperintense compared to the adjacent normal bone marrow.