Table 1.
7T and 3T T1VIBE, T2 DESS and T2* SWI forearm protocols for HR: Higher and LR: Lower resolution sequences.
Table 2.
7T in-vivo imaging protocols for elbow, forearm, and hand [Figs 3 and 5–9; T1VIBE, T2 DESS, T2* SWI, DTI, and TOF].
Fig 1.
Left: 3T vs. 7T T1 VIBE images on both higher [HR which is optimized for 7T] and lower [LR which is optimized for 3T] resolutions [as described Table 1]. In the 3T images [A, B, C, G, H and I], smaller order vessels as indicated by arrows are barely visible; while they are well detected on the 7T images [D, E, F, J, K and L]. Yellow arrows indicate micro-vessel branches and yellow ellipses delineate nerves from surrounding muscle plane. Note motion and pulsatile flow artifacts [band of bright points] originating from the median artery in the anterior to posterior phase encoding direction. Right: SNR and CNR charts for T1 VIBE images. [A and B] and [C and D] represent SNR and CNR; respectively. The 7T SNR and CNR were ~ 2/1.5 times that of 3T for the HR/LR scans, respectively. Out of all three volunteer, the above data is from single volunteer only.
Fig 2.
Left: 3T vs. 7T T2 DESS images on both higher [HR which is optimized for 7T] and lower [LR which is optimized for 3T] resolutions [as described Table 1]. Small order vessel [yellow arrows] and nerve [yellow circles] signals as indicated by circles are difficult to identify on the 3T [A, B, C, G, H and I] images but are well delineated on the 7T [D, E, F, J, K, L] images Right: SNR and CNR charts for T1 VIBE images. [A and B] and [C and D] represent SNR and CNR; respectively. The 7T SNR and CNR were ~ 2/1.5 times that of 3T for the HR/LR scans, respectively. Out of all three volunteer, the above data is from single volunteer only.
Table 3.
3T/7T MRI Analysis [Image Quality Scale: 1-nondiagnostic, 2- poor, 3-fair, 4-good and 5-excellent; Artifacts scale: 1-absent, 2-present but not affecting anatomic detail and 3-present and severely affecting image interpretation].
Fig 3.
7T T1 VIBE and T2 DESS images of the forearm demonstrating homogeneous excitation in axial [elbow to wrist], coronal and sagittal planes. The B1+ field coefficient of variation was calculated to be 21% in the forearm [encapsulated within the coil volume].
Fig 4.
3T/7T T2* SWI: Intramuscular vascular branches [off the radial artery] are shown on the HR/LR 3T [A, B, C, G, H and I] images, but are more delineated on 7T [D, E, F, J, K and L] images. Yellow arrow and circles: indicate micro-vessel branches. Out of all three volunteer, the above data is from single volunteer only.
Fig 5.
7T T1 VIBE and T2 DESS: A1 [T1 VIBE] represents radial and median nerve delineation [arrows]; A2 [T2 DESS] shows ulnar nerve [arrow]; B:1–3 [T1 VIBE] and corresponding T2 DESS [B:4–6] show three axial slices [close to elbow, forearm, and close to wrist] that depict radial, median and ulnar nerves [yellow arrows, circles] in addition to the major arteries [red arrows]; Note that there are motion and pulsatile flow artifacts [band of bright points] from median artery in anterior to posterior phase encoding direction; C:1–2 [T1 VIBE] and C:3–4 [T2 DESS] show joint anatomy depicting bone, cartilage, and synovial fluid.
Fig 6.
7T T2* SWI [bottom row] show marked enhancement of vascular patterns of arteries, veins and muscular perforators [marked with yellow arrow] when compared to the T1 VIBE images [top row].
Fig 7.
Top row: 7T DTI with T1 VIBE and T2 DESS validation: A represents T1 VIBE image and B represents T2 DESS image for validation of the locations of the forearm nerves [yellow circles]. C, D, E and F represent ADC, FA, TRACEW, and color-coded DTI map identifying forearm nerves, respectively [note the rotation of the T1 VIBE and T2 DESS images to match the DTI ones.] G and H represent FA map in sagittal view showing median [m] and radial [r] nerves using multiple intensity projection [MIP]. I demonstrates multiple intensity projection [MIP] of combined m and r nerves. Bottom row: 7T fiber tractography: 1, 2 and 3 show DTI FA maps demonstrating separate forearm nerves with anatomical validation [yellow rectangles] side by side. 4 and 5 demonstrate 3D DTI and DSI rendering showing forearm nerves tractography, respectively.
Table 4.
Quantitative DTI track analysis values for forearm nerves as shown in Fig 7, [FA: Fiber Anisotropy, ADC: Apparent diffusion coefficient, Ax: Axial/Longitudinal, Diff: Diffusivity, sd: standard deviation, and Rad: Radial].
Fig 8.
7T TOF and T1 VIBE: A [TOF] demonstrates eight proper palmar digital arteries [two of them are yellow circled], digital tendons and synovial sheaths on axial view and B [T1 VIBE] shows proper palmer arteries and two proper palmer digital arteries in thumb, and cross-sectional transmetacarpal view highlighting intrinsic muscles, flexor digitorum superficialis and profundus tendons apparatus with synovial sheaths, ligamentous structures, and inter-metacarpal vasculature. C demonstrates multiple intensity projection [MIP] of hand vasculature and [D, E and F] represent non-contrast enhanced MR angiographic images of palmar and digital microvasculature in the hand. G demonstrates 3D view of volume rendering texture [VRT].
Fig 9.
7T Vasculature Segmentation: A represents coronal image as an example of paint grows segmentation method using T1 VIBE images. B displays forearm vasculature segmentation [3D view] showing brachial artery and its branches [arrows] as well as venae comitans and superficial arteriovenous networks. C shows complete ulnar artery [arrow] and D represents radial [arrow] and brachial bifurcation [arrow] in the forearm.