Fig 1.
7 Tesla 3D VIBE imaging using the CP (Figure A) and CP2+ mode (Figure B) to shift and focus B1 inhomogeneities from the right liver lobe and peripancreatic area (arrows Figure A) to a less disturbing focal periaortal area (arrow Figure B).
Table 1.
Detailed imaging parameters for the T1 weighted sequences.
Table 2.
Detailed imaging parameters for the T2w TSE sequence and TrueFISP imaging.
Fig 2.
(A) Quantitative analysis showing contrast ratios of different parenchymatous organs to the ipsilateral psoas muscle for the T1-weighted sequences. * indicates statistical significance (p value < 0.05).(B) Quantitative analysis showing contrast ratios of different parenchymatous organs to the ipsilateral psoas muscle for TrueFISP and T2-weighted TSE sequence. * indicates statistical significance (p value < 0.05).
Table 3.
Qualitative image evaluation.
Table 4.
Qualitative image evaluation.
Fig 3.
2D FLASH imaging at 1.5 Tesla (A), 3 Tesla (B) and 7 Tesla (C) in the same subject. The white circles indicate the ROIs for signal measurements in the right liver lobe (1), right psoas muscle (2), left liver lobe (3), spleen (4), left kidney cortex (5) and left psoas muscle (6). Note the slight motion artifacts due to breathing as well as the slight loss in contrast at 3 Tesla (B) compared to 1.5 Tesla (A) and the hyperintense delineation of intra-abdominal vasculature at 7 Tesla (C).
Fig 4.
3D VIBE imaging at 1.5 Tesla (A), 3 Tesla (B) and 7 Tesla (C) in the same subject. Note equivalent overall image quality, contrast, homogeneous fat saturation and signal homogeneity at all three field strengths. Dashed arrows point at incidental hemorrhaged renal cyst.
Fig 5.
T1-weighted 2D in and opposed phase.
T1-weighted 2D in and opposed phase imaging at 1.5 Tesla (A1,2) 3 Tesla (B1,2) and 7 Tesla (C1,2) in the same subject. The typical black rims with a fat/water interface around organs are increasingly sharp and clear visualized in the opposed phase images at 3 and 7 Tesla, compared to 1.5 Tesla and are also visible in the in phase images at 7 Tesla. Nevertheless, strong signal voids due to RF shimming are detectable in the periaortal region at 7 Tesla images. The expected exacerbation of chemical shifting (3.77Tesla, 4.43Tesla, 4.51.5Tesla) associated to the increase of the magnetic field strength resulted in insignificantly decreased mean values of overall image quality and impairment at 7 Tesla compared to 1.5 and 3 Tesla (4.27Tesla, 4.43Tesla, 4.61.5Tesla). Additionally 7 Tesla MRI was relatively strongly impaired due to residual B1 inhomogeneities (3.77Tesla, 4.53Tesla, 4.81.5Tesla). Being a T1w gradient echo sequence, in and opposed phase imaging also provided moderate to high-quality delineation of the non-enhanced vasculature at 7 Tesla (3.87Tesla, 2.13Tesla, 1.91.5Tesla). In accordance to the previous T1w sequences, 7 Tesla demonstrated higher contrast ratios compared to 3 Tesla and 1.5 Tesla for all organs with highest difference for the left kidney (CR7Tesla 0.35, CR3Tesla 0.12, CR1.5Tesla 0.07), p<0.012 respectively. For the right liver lobe S6 (CR7Tesla 0.19, CR3Tesla 0.16, CR1.5Tesla 0.14) and the spleen (CR7Tesla 0.17, CR3Tesla 0.16, CR1.5Tesla 0.09), 7 Tesla revealed slightly higher values without statistical significance (p values from 0.326–1).
Fig 6.
T2 TSE imaging at 1.5 Tesla (A1,2) 3 Tesla (B1,2) and 7 Tesla (C1,2) in the same subject. Note equivalent image quality and contrast at 1.5 Tesla (A) and 3 Tesla (B). Despite the increased spatial resolution no improvement can be detected at 3 Tesla (B). Figure C shows strongly impaired T2 TSE imaging at 7 Tesla, revealing strong signal loss in parenchymatous organs. Hence, assessment of the biliary duct system was significantly hampered at 7 Tesla field strength (1.47Tesla, 4.93Tesla, 4.91.5Tesla). Quantitative evaluation confirmed limitations of T2w TSE at 7 Tesla showing lowest CR values for all analyzed organs compared to 3 Tesla and 1.5 Tesla, being significantly lower for the spleen tissue (CR7Tesla 0.29, CR3Tesla 0.67, CR1.5Tesla 0.63) with p<0.012, and non-significantly lower for liver and kidney tissue. Detailed graphs for evaluation of contrast ratios are displayed in Fig 2.
Fig 7.
3D VIBE imaging at 1.5 Tesla (A), 3 Tesla (B) and 7 Tesla (C) in the same subject. 7 Tesla 3D VIBE imaging demonstrated diagnostic potential by means of detection of pathologies, as it revealed a second hemorrhaged renal cyst (dashed arrow Figure C1), not being displayed at lower field strengths. In the second row, arrows show a further very small renal cyst in the same subject, which is also best visible at 7 Tesla (C2).