Use of the modified three-point Dixon technique in obtaining T1-weighted contrast-enhanced fat-saturated images on an open magnet

The purpose of this study was to investigate the modified three-point Dixon technique as a method for obtaining fat-saturated T1-weighted sequences before and after intravenous gadolinium administration using an open MR imaging scanner. A preliminary experiment using an oil/gadolinium phantom was performed on a 0.35-T open magnet and an advanced 1.5-T unit. Fat saturation was achieved at 1.5T using a frequency selective presaturation technique and a modified three-point Dixon technique on the low-field scanner. The modified three-point Dixon sequence was then evaluated in ten patients undergoing MRI examinations of the spine with gadolinium enhancement to determine image characteristics and diagnostic potential. The phantom study demonstrated a homogenous suppression of signal from oil and a good distinction between fat and a gadolinium chelate on the 0.35-T unit comparable to that on the 1.5-T scanner. By applying the modified three-point Dixon technique on the open-magnet, the distinction between fat and gadolinium dimeglumine was rated as very good in 139 and good in 17 axial slices in a total of 156 images. No image was rated as difficult or not possible. Motion artifacts that hampered the reading were detected in the lower cervical spine due to respiratory movement in four (3% of all) images. The modified three-point Dixon technique provides the combination of gadolinium enhancement with fat saturation on an open magnet. Early clinical applications appear promisin

Enhanced vertebra to disk ratio as a new semi-quantitative imaging biomarker for Gaucher disease patients

Purpose: Gaucher disease (GD) is an inherited lysosomal storage disorder. The Vertebral Disk Ratio (VDR) is a semi-quantitative imaging biomarker designed to diagnose and monitor GD. Computed from standard T1 MRI images, the VDR is derived from 2D segmentations. This study aimed to evaluate the 3D version of VDR, namely eVDR, and analyze the performances of two eVDR–derived response criteria for GD patients. Methods: Three datasets were used: 8 longitudinal GD patients, 13 non-GD patients, and 2 longitudinal GD patients with known Bone Marrow Burden (BMB) scores. Two eVDR-derived response criteria were tested: 1) a parametric version (PeVDR) averaging all eVDR measures recorded for the 5 lumbar vertebrae; and 2) a non-parametric version (NPeVDR), considering all eVDR measures as independent and evaluating therapeutic response in a paired fashion. Analyses included assessment of reader variability in eVDR (3D) versus VDR (2D) and comparison with BMB response criteria. Results: The repeatability of eVDR (3D) versus VDR (2D) demonstrated no difference in mean values but a lower variance (p < 0.004). The PeVDR intra-reader variability had a standard deviation < 0.1 with a coefficient of variation < 5%; the inter-reader variability featured a Limit of Agreement < 5% and a Bias < 3%. Observational comparison of eVDR and BMB scoring and sensitivity indicated a correlation between PeVDR and BMB, with an improved sensitivity with the NPeVDR version. Conclusions: Based on a standard MRI sequence, the eVDR imaging biomarker and its derived response criteria improved GD assessments and could help assessing other bone marrow diseases

Magnetic Resonance Imaging and biochemical markers of osteoarthritis of the knee

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