Progress in Imaging the Human Torso at the Ultrahigh Fields of 7 and 10.5 T

Imaging of the human torso at high magnetic fields such as 4 T was considered almost an impossible task due to the short wavelength of the required RF relative to the object size, and this idea was cemented by the early, virtually unrecognizable images of the torso first reported at 4 T (see Fig. 4A). This skepticism was, in a way, a continuation of the doubts surrounding the use of high magnetic fields for imaging in the human body that existed since the early days of MR imaging. At that time, based on modeling the electrically lossy and conductive human body tissue, it was suggested that sensitivity and RF penetration issues made imaging at frequencies beyond w10 MHz (w0.24 T) inadvisable. 114 Especially after the launch of 7 T,1 however, the UHF imaging community achieved critically important strides in our understanding of the physics of RF interactions in the human body, which in turn has led to solutions for the challenges posed by such UHFs. As a result, the originally observed poor image quality, as demonstrated in Fig. 4A obtained at 4 T, has progressed to the high-quality and high-resolution images obtained at 7 T and now at 10.5 T in the human torso. Despite these tremendous advances, work still remains to further improve the image quality and fully capitalize on the potential advantages UHF has to offer. Many potential improvements are well known to the practitioners in the field and simply need to be implemented. Inevitably, new technologies will be developed also, bringing new transformative changes and carrying UHF imaging of organ systems of the human torso to new heights.