Feasibility and evaluation of dual-source transmit 3D imaging of the orbits: Comparison to high-resolution conventional MRI at 3T

• Reduced FOV imaging enables a 3D approach for a very fast assessment of the orbits.
• Conventional MRI exhibited higher eSNR values and consecutively higher scores for overall image quality in the subjective readers’ analysis.
• All pathologies could be detected compared to high-resolution conventional MRI making 3D pTX SPACE to a potential alternative and fast imaging technique.

PurposeTo prospectively compare the image quality and diagnostic performance of orbital MR images obtained by using a dual-source parallel transmission (pTX) 3D sequence (Sampling Perfection with Application optimized Contrasts using different flip angle Evolution, SPACE) with the image quality of conventional high-resolution standard protocol for clinical use in patients at 3T.Materials and methodsAfter obtaining institutional review board approval and patient consent, 32 patients with clinical indication for orbital MRI were examined using a high-resolution conventional sequences and 3D pTX SPACE sequences. Quantitative measurements, image quality of the healthy orbit, incidence of artifacts, and the subjective diagnostic performance to establish diagnosis was rated. Statistical significance was calculated by using a Student's t-test and nonparametric Wilcoxon signed rank test.ResultsLength measurements were comparable in the two techniques, 3D pTX SPACE resulted in significant faster image acquisition with higher spatial resolution and less motion artifacts as well as better delineation of the optic nerve sheath. However, estimated contrast-to-noise and signal-to-noise and overall image quality as well as subjective scores of the conventional TSE imaging were rated significantly higher. The conventional MR sequences were the preferred techniques by the readers.ConclusionThis study demonstrates the feasibility of 3D pTX SPACE of the orbit resulting in a rapid acquisition of isotropic high-resolution images. Although no pathology was missed in 3D pTX SPACE, conventional MRI techniques showed the higher diagnostic confidence in our study, presumably due to the higher signal-to-noise and contrast-to-noise ratios. We observed high-resolution TSE imaging to be the preferred technique, 3D pTX SPACE cannot replace conventional MRI so far.