Synthetic MRI for Clinical Neuroimaging: Results of the Magnetic Resonance Image Compilation (MAGiC) Prospective, Multicenter, Multireader Trial.

BACKGROUND AND PURPOSE: Synthetic MR imaging enables reconstruction of various image contrasts from 1 scan, reducing scan times and potentially providing novel information. This study is the first large, prospective comparison of synthetic-versus-conventional MR imaging for routine neuroimaging. MATERIALS AND METHODS: A prospective multireader, multicase noninferiority trial of 1526 images read by 7 blinded neuroradiologists was performed with prospectively acquired synthetic and conventional brain MR imaging case-control pairs from 109 subjects (mean, 53.0 ± 18.5 years of age; range, 19-89 years of age) with neuroimaging indications. Each case included conventional T1- and T2-weighted, T1 and T2 FLAIR, and STIR and/or proton density and synthetic reconstructions from multiple-dynamic multiple-echo imaging. Images were randomized and independently assessed for diagnostic quality, morphologic legibility, radiologic findings indicative of diagnosis, and artifacts. RESULTS: Clinical MR imaging studies revealed 46 healthy and 63 pathologic cases. Overall diagnostic quality of synthetic MR images was noninferior to conventional imaging on a 5-level Likert scale (P < .001; mean synthetic-conventional, -0.335 ± 0.352; Δ = 0.5; lower limit of the 95% CI, -0.402). Legibility of synthetic and conventional morphology agreed in >95%, except in the posterior limb of the internal capsule for T1, T1 FLAIR, and proton-density views (all, >80%). Synthetic T2 FLAIR had more pronounced artifacts, including +24.1% of cases with flow artifacts and +17.6% cases with white noise artifacts. CONCLUSIONS: Overall synthetic MR imaging quality was similar to that of conventional proton-density, STIR, and T1- and T2-weighted contrast views across neurologic conditions. While artifacts were more common in synthetic T2 FLAIR, these were readily recognizable and did not mimic pathology but could necessitate additional conventional T2 FLAIR to confirm the diagnosis.

High-b-value diffusion-weighted MR imaging of adult brain: image contrast and apparent diffusion coefficient map features.

BACKGROUND AND PURPOSE: Recent improvements in MR gradient technology allow significant increases in diffusion weighting without prohibitive signal-to-noise degradation. The purpose of our investigation was to establish normative references for the signal intensity characteristics and apparent diffusion coefficient values of the adult brain at high b values. METHODS: Fifty adults underwent diffusion-weighted single-shot spin-echo echo-planar MR imaging. Isotropic diffusion-weighted images were obtained with b values of 0, 1,000, 2,000, 2,500, 3,000, and 3,500 s/mm2. Qualitative assessments were made in multiple regions of interest in gray and white matter. Three apparent diffusion coefficient maps were generated for each of six patients with a 2-point technique at a b value of 0 and at b values of 1,000, 2,000, and 3,000 s/mm2. RESULTS: Increasing b values result in a progressive decrease in the gray to white matter signal intensity ratio. Isointensity between gray and white matter results at b values between 1,000 and 2,000 s/mm2. At b values greater than 2,000, the gray-white pattern reverses relative to the usual b value of 1,000. Apparent diffusion coefficient values were shown to decrease with increasing b values. CONCLUSION: Attention to the reversal of gray-white contrast and the dependence of apparent diffusion coefficient on the b value are important in avoiding erroneous assignment of pathologic abnormalities to normal regions. This study provides the normative data for future diffusion investigations performed at high b values.

Relationship of the optic nerve to the posterior paranasal sinuses: a CT anatomic study.

PURPOSE: To delineate the relationship between the optic nerves and the posterior paranasal sinuses using CT data. METHODS: Direct coronal sinus CT scans of 150 consecutive patients with chronic inflammatory sinus disease were reviewed by two radiologists. Axial oblique reconstructions along the course of the optic nerve were obtained for the first 100 patients. The direct relationship between the optic nerve and the posterior ethmoid and sphenoidal sinuses was recorded, as were identations into the sinus wall, course of the nerve through the sinus region, pneumatization of the anterior clinoid process, and bone dehiscence. RESULTS: The relationship of the optic nerve to the posterior paranasal sinus fell into one of four discrete categories, type 1 through type 4. All 300 nerves were intimately related to the sphenoidal sinus. A small minority (3%) were in contact with the posterior ethmoidal sinus. Only type 4 nerves had contact with the posterior ethmoid air cell. Type 1 nerves course adjacent to the sphenoid sinus without indentation of the wall (228 nerves, 76%). Type 2 nerves course adjacent to the sphenoidal sinus, causing indentation of the sinus wall (44 nerves, 15%). Type 3 nerves course through the sphenoid sinus (19 nerves, 6%). Type 4 nerves course immediately adjacent to the sphenoidal sinus and the posterior ethmoidal air cell (9 nerves, 3%). Bone dehiscence over the optic nerve was found in 24% of the nerves; 4% of the optic nerves in our study had an associated pneumatized anterior clinoid process and 77% of these had an associated dehiscence over the optic canal. CONCLUSIONS: In all our cases the course of the optic nerve was adjacent to the sphenoidal sinus. Only 3% were in contact with the posterior ethmoidal sinus. Anatomic configurations that predispose the optic nerve to injury include type 2 or 3 optic nerves, bone dehiscence over the nerve, and pneumatization of the anterior clinoid process. These configurations are common and should be routinely sought out so that devastating complications from sinus surgery can be avoided.