Deep Learning Image Processing Enables 40% Faster Spinal MR Scans Which Match or Exceed Quality of Standard of Care : A Prospective Multicenter Multireader Study.

OBJECTIVE: This prospective multicenter multireader study evaluated the performance of 40% scan-time reduced spinal magnetic resonance imaging (MRI) reconstructed with deep learning (DL). METHODS: A total of 61 patients underwent standard of care (SOC) and accelerated (FAST) spine MRI. DL was used to enhance the accelerated set (FAST-DL). Three neuroradiologists were presented with paired side-by-side datasets (666 series). Datasets were blinded and randomized in sequence and left-right display order. Image features were preference rated. Structural similarity index (SSIM) and per pixel L1 was assessed for the image sets pre and post DL-enhancement as a quantitative assessment of image integrity impact. RESULTS: FAST-DL was qualitatively better than SOC for perceived signal-to-noise ratio (SNR) and artifacts and equivalent for other features. Quantitative SSIM was high, supporting the absence of image corruption by DL processing. CONCLUSION: DL enables 40% spine MRI scan time reduction while maintaining diagnostic integrity and image quality with perceived benefits in SNR and artifact reduction, suggesting potential for clinical practice utility.

Influence of the dielectric substrate on the effective optical constants of silver plasmonic films.

The effective optical properties of plasmonic thin films can be used to model the far-field response of nanostructured materials to an incident electromagnetic field. In the present work, optically thin nanostructured silver (Ag) plasmonic films were fabricated on transparent dielectric substrates of soda-lime glass, sapphire, and fused silica using oblique angle deposition. The influence of the underlying dielectric substrate on the effective optical properties of the nanostructured layer was investigated by an ellipsometric-optical model based on Mueller matrix ellipsometry. The wavelength-dependent uniaxial optical responses of the nanostructured Ag films fabricated on sapphire were modeled with three Gaussian and one Tanguy oscillator, representing key optical phenomena over the range from 300 to 1000 nm. In comparison with the same Ag films on glass, the results confirm that the effective optical properties cannot be considered in isolation from the substrate. As expected, the extinction peak associated with the localized surface plasmon resonance was redshifted by approximately 220 nm per unit of the substrate refractive index. Importantly, it was found that the direction of incidence also influences the film behavior, with a substantial redshift in the extinction peak for light directed through the dielectric compared to free-space illumination. This property can have a significant effect on the far-field performance of these films.

Critical Assessment of Myelography Practices: A Call for Rational Guideline Revision.

BACKGROUND AND PURPOSE: Patient preparation for myelography and postprocedural monitoring varies widely between practices, despite published guidelines. Our aim was to examine the current practice variations in discontinuing reportedly seizure threshold-lowering medications before myelography and to assess the reported incidence of postmyelographic seizures. MATERIALS AND METHODS: An e-mail survey was sent to American Society of Neuroradiology members concerning the number of postmyelographic seizures experienced in the past 5 years, the presence of an institutional policy for discontinuing seizure threshold-lowering medications, and the type of myelographic contrast used. We compared the postmyelographic seizure frequency in the responses. RESULTS: Of 700 survey responses, 57% reported that they do not discontinue seizure threshold-lowering medications before myelography. Most (97%) indicated never having a patient experience a seizure following myelography. The number of postmyelographic seizures between those who discontinue seizure threshold-lowering medications and those who do not was not statistically significant (OR = 2.13; 95% CI, 0.91-4.98; P = .08). Most (95%) reported using nonionic hypo-osmolar agents. CONCLUSIONS: Survey results revealed widely variable practices for patient myelography preparation and postprocedural monitoring. We found no difference in reported seizures between those who discontinued seizure threshold-lowering medications and those who did not. In light of our findings, we propose that discontinuing reportedly seizure threshold-lowering medications is not warranted with the current nonionic water-soluble contrast agents and may be potentially harmful in some instances. This work supports revision of existing recommendations to withhold such medications before myelography.

Complications of Radiotherapy and Radiosurgery in the Brain and Spine.

Radiation therapy is an integral part of the standard of care for many patients with brain and spine tumors. Stereotactic radiation surgery is increasingly being used as an adjuvant therapy as well as a sole treatment. However, despite newer and more focused techniques, radiation therapy still causes significant neurotoxicity. In this article, we reviewed the scientific literature, presented cases of patients who had developed different complications related to conventional radiation therapy or radiosurgery (gamma knife), demonstrated the imaging findings, and discussed the relevant clinical information for the correct diagnoses. Radiation therapy can cause injury in different ways: directly damaging the structures included in the radiation portal, indirectly affecting the blood vessels, and increasing the chance of tumor development. We also divided radiation complications according to the time of occurrence: acute (0 to 4 weeks), early delayed (4 weeks to months), and late delayed (months to years). With the increasing application of radiation therapy for the treatment of CNS tumors, it is important for the neuroradiologist to recognize the many possible complications of radiation therapy. Although this may cause significant diagnostic challenges, understanding the pathophysiology, time course of onset, and imaging features may help institute early therapy and prevent possible deleterious outcomes. Learning Objectives: To recognize the main complications of radiation therapy and stereotactic radiosurgery in the brain and spine, and to highlight the imaging findings to improve the diagnostic process and treatment planning.

Effective optical constants of anisotropic silver nanoparticle films with plasmonic properties: erratum.

This erratum reports a correction to Fig. 5 in the original manuscript, Opt. Lett.41, 5495 (2016)OPLEDP0146-959210.1364/OL.41.005495.

CT Angiography of the Head in Extracorporeal Membrane Oxygenation.

Extracorporeal membrane oxygenation is an artificial cardiopulmonary bypass technique used to support patients with severe pulmonary failure or both pulmonary and cardiac failure. The hemodynamic changes produced by extracorporeal membrane oxygenation affect the appearance of CTA of the head images, often confounding interpretation if the correct history and understanding of extracorporeal membrane oxygenation are not known. This technical report describes the principles of extracorporeal membrane oxygenation, techniques to optimize intracranial CTA imaging, and pitfalls.

Effective optical constants of anisotropic silver nanoparticle films with plasmonic properties.

Mueller matrix ellipsometry has been used to determine the effective optical constants of island-like Ag films deposited by thermal evaporation. These films depart substantially from bulk silver with a prominent localized surface plasmon resonance. Moreover, despite the isotropic appearance, they exhibit uniaxial optical properties with the optical axis inclined by 83.4° from the substrate normal toward the direction of the incoming vapor flux. The uniaxial model supports the plasmon resonance peaks revealed by in-plane absorbance measurements of the films. The uniaxial behavior suggests that the resonances along the ordinary axes are weakly coupled between neighboring particles, whereas the extraordinary resonance is relatively strongly coupled. Therefore, the anisotropy should be considered in the practical applications of these plasmonic films.