As radiology is inherently a data-driven specialty, it is especially conducive to utilizing data processing techniques. One such technique, deep learning (DL), has become a remarkably powerful tool for image processing in recent years. In this work, the Association of University Radiologists Radiology Research Alliance Task Force on Deep Learning provides an overview of DL for the radiologist. This article aims to present an overview of DL in a manner that is understandable to radiologists; to examine past, present, and future applications; as well as to evaluate how radiologists may benefit from this remarkable new tool. We describe several areas within radiology in which DL techniques are having the most significant impact: lesion or disease detection, classification, quantification, and segmentation. The legal and ethical hurdles to implementation are also discussed. By taking advantage of this powerful tool, radiologists can become increasingly more accurate in their interpretations with fewer errors and spend more time to focus on patient care.

Multiple sclerosis (MS) is an autoimmune disease in which myelin-specific T cells are believed to play a crucial pathogenic role. Nevertheless, so far it has been extremely difficult to demonstrate differences in T cell reactivity to myelin Ag between MS patients and controls. We believe that by using unphysiologically high Ag concentrations previous studies have missed a highly relevant aspect of autoimmune responses, i.e., T cells recognizing Ag with high functional avidity. Therefore, we focused on the characterization of high-avidity myelin-specific CD4+ T cells in a large cohort of MS patients and controls that was matched demographically and with respect to expression of MHC class II alleles. We demonstrated that their frequency is significantly higher in MS patients while the numbers of control T cells specific for influenza hemagglutinin are virtually identical between the two cohorts; that high-avidity T cells are enriched for previously in vivo-activated cells and are significantly skewed toward a proinflammatory phenotype. Moreover, the immunodominant epitopes that were most discriminatory between MS patients and controls differed from those described previously and were clearly biased toward epitopes with lower predicted binding affinities to HLA-DR molecules, pointing at the importance of thymic selection for the generation of the autoimmune T cell repertoire. Correlations between selected immunological parameters and magnetic resonance imaging markers indicate that the specificity and function of these cells influences phenotypic disease expression. These data have important implications for autoimmunity research and should be considered in the development of Ag-specific therapies in MS.

It has been proposed that the intact (ipsilateral) motor cortex play a significant role mediating recovery of motor function in the paretic hand of chronic stroke patients, but this hypothesis has not been tested experimentally. Here, we evaluated the effects of transcranial magnetic stimulation (TMS) on motor performance of the paretic hand of chronic stroke patients and healthy controls. We hypothesized that, if activity in the intact hemisphere contributes to functional recovery, TMS should result in abnormal motor behavior in the paretic hand. We found that stimulation of the intact hemisphere resulted in delayed simple reaction times (RTs) in the contralateral healthy but not in the ipsilateral paretic hand, whereas stimulation of the lesioned hemisphere led to a marked delay in RT in the contralateral paretic hand but not in the ipsilateral healthy hand. RT delays in the paretic hand correlated well with functional recovery. Finger tapping in the paretic hand was affected by TMS of the lesioned but not the intact hemisphere. These results are consistent with the idea that recovered motor function in the paretic hand of chronic stroke patients relies predominantly on reorganized activity within motor areas of the affected hemisphere.

SUMMARYPurpose: Investigate whether patients on vigabatrin demonstrated new-onset and reversible T 2 -weighted magnetic resonance imaging (MRI) abnormalities. Methods: MRI of patients treated during vigabatrin therapy was reviewed, following detection of new basal ganglia, thalamus, and corpus callosum hyperintensities in an infant treated for infantile spasms. Patients were assessed for age at time of MRI, diagnosis, duration, and dose, MRI findings pre-, on, and postvigabatrin, concomitant medications, and clinical correlation. These findings were compared to MRI in patients with infantile spasms who did not receive vigabatrin. Results: Twenty-three patients were identified as having MRI during the course of vigabatrin therapy. After excluding the index case, we detected new and reversible basal ganglia, thalamic, brainstem, or dentate nucleus abnormalities in 7 of 22 (32%) patients treated with vigabatrin. All findings were reversible following discontinuation of therapy. Diffusion-weighted imaging (DWI) was positive with apparent diffusion coefficient (ADC) maps demonstrating restricted diffusion. Affected versus unaffected patients, respectively, had a median age of 11 months versus 5 years, therapy duration 3 months versus 12 months, and dosage 170 mg/ kg/day versus 87 mg/kg/day. All affected patients were treated for infantile spasms; none of 56 patients with infantile spasms who were not treated with vigabatrin showed the same abnormalities. Discussion: MRI abnormalities attributable to vigabatrin, characterized by new-onset and reversible T 2 -weighted hyperintensities and restricted diffusion in thalami, globus pallidus, dentate nuclei, brainstem, or corpus callosum were identified in 8 of 23 patients. Young age and relatively high dose appear to be risk factors.

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Sickle cell disease (SCD) is a hemoglobinopathy affecting more than 100,000 individuals in United States. The disease is characterized by presence of sickle hemoglobin and recurrent episodes of pain. Some individuals with SCD experience frequent hospitalizations and high burden of pain. The role of central mechanisms in SCD pain has not been explored. Twenty-five adolescents and young adults with SCD underwent functional MRI (fMRI). Participants were stratified into high or low pain groups based on the number of hospitalizations for pain in preceding 12 months. Resting state functional connectivity was analyzed using seed based and dual-regression independent component analysis. Intrinsic brain connectivity was compared between high and low pain groups and association with fetal hemoglobin, a known modifier of SCD, was explored. Patients in the high pain group displayed an excess of pro-nociceptive connectivity such as anterior cingulate to default-mode-network structures such as the precuneus, whereas patients in low pain group showed more connectivity to anti-nociceptive structures such as the peri- and sub-genual cingulate. Although a similar proportion of patients in both groups reported to be on hydroxyurea, the fetal hemoglobin levels were significantly higher in the low pain group and were associated with greater connectivity to anti-nociceptive structures. These findings support the role of central mechanisms in SCD pain. Intrinsic brain connectivity should be explored as a complementary and objective outcome measure in SCD pain research.

Although detection of cervical spine injuries by MRI does not discriminate between accidental and abusive head trauma, it can help to distinguish a traumatic from non-traumatic intracranial subdural hemorrhage. Cervical MRI should be considered in children with acute intracranial bleeds and otherwise non-contributory history, physical examination and ophthalmological findings. There is a statistically significant relationship between diffuse hypoxic-ischemic brain injury patterns and abusive head trauma. The high incidence of cervical injuries in children with hypoxic-ischemic injuries suggests a causal relationship. Overall, increased utilization of brain and spine MRI in children being evaluated for abusive head trauma can be helpful.

The inflammatory activity and destructiveness of the multiple sclerosis process are to some degree independent of each other, and the successive evaluation of both of these variables can strengthen prediction of clinical outcome in individual patients.