Neuronal phase consistency tracks dynamic changes in acoustic spectral regularity.

The brain parses the auditory environment into distinct sounds by identifying those acoustic features in the environment that have common relationships (e.g., spectral regularities) with one another and then grouping together the neuronal representations of these features. Although there is a large literature that tests how the brain tracks spectral regularities that are predictable, it is not known how the auditory system tracks spectral regularities that are not predictable and that change dynamically over time. Furthermore, the contribution of brain regions downstream of the auditory cortex to the coding of spectral regularity is unknown. Here, we addressed these two issues by recording electrocorticographic activity, while human patients listened to tone-burst sequences with dynamically varying spectral regularities, and identified potential neuronal mechanisms of the analysis of spectral regularities throughout the brain. We found that the degree of oscillatory stimulus phase consistency (PC) in multiple neuronal-frequency bands tracked spectral regularity. In particular, PC in the delta-frequency band seemed to be the best indicator of spectral regularity. We also found that these regularity representations existed in multiple regions throughout cortex. This widespread reliable modulation in PC - both in neuronal-frequency space and in cortical space - suggests that phase-based modulations may be a general mechanism for tracking regularity in the auditory system specifically and other sensory systems more generally. Our findings also support a general role for the delta-frequency band in processing the regularity of auditory stimuli.

JOURNAL CLUB: Longitudinal Qualitative Characterization of MRI Features After Laser Interstitial Thermal Therapy in Drug-Resistant Epilepsy.

OBJECTIVE: Laser interstitial thermal therapy (LITT), a method for ablating brain tissue under real-time MR thermometry, has been used more frequently in recent years to treat nonmalignant lesions. The purpose of this study is to longitudinally characterize MRI features after LITT in patients with drug-resistant epilepsy, primarily in the setting of mesial temporal sclerosis. MATERIALS AND METHODS: MR images from 23 consecutive patients who underwent LITT were retrospectively reviewed. All patients had images obtained immediately after the ablation. Multiple patients had follow-up imaging at various time points after treatment, from postoperative days 7 through 1539. A total of 54 MRI studies were reviewed. RESULTS: Immediately after LITT, MR images showed a ring-enhancing lesion at the ablation site with minimal surrounding edema. Seven images showed increased enhancement of the ipsilateral choroid plexus. Images in the subacute phase showed a mild increase in edema with similar enhancement. Images in the transitional phase showed a decrease in edema with variable enhancement. Images in the chronic phase showed minimal gliosis with or without cavity formation or cavity formation alone, with either decreased or no enhancement. CONCLUSION: This report describes the time course of the imaging findings after LITT for drug-resistant epilepsy. The typical stages include rim-enhancing lesion with minimal edema, followed by an increase in edema, to eventual gliosis and nonenhancing cavity formation. Radiologists need to be familiar with the postablation findings to minimize misdiagnosis and prevent unnecessary workup.

Trainee report dashboard: tool for enhancing feedback to radiology trainees about their reports.

During their radiology residency, trainees must learn multiple facets of radiology practice, including the writing of radiology reports. An important factor in the trainee's development of reporting skills is feedback from the attending radiologist on the trainee's preliminary reports. The quality and quantity of feedback may vary and are not typically documented. As radiology department workloads have increased and stricter limitations have been imposed on trainee work hours, less time is available for attending radiologists and trainees to perform a joint retrospective review of radiology reports. To compensate, the authors have developed a Web-based dashboard that provides trainees with case-specific feedback about their reports. Components include an attending radiologist-trainee report discrepancy logging and communication system that is integrated with the institutional picture archiving and communication system, an automated preliminary report-final report comparator, modules showing statistics related to the discrepancy logger and report comparator components, and a Web page that unifies these components with image and report display capabilities. Both the actual report feedback and the trainee's use of the system are documented, and the resultant data may be used for evaluating trainee competence in written communication, as mandated by the Accreditation Council for Graduate Medical Education. With these tools, trainees can obtain near-real-time feedback, which may pinpoint issues that can be corrected to improve the quality of their radiology reporting. This system, although it does not supplant face-to-face training sessions with attending radiologists, can augment traditional methods of learning.

Trainee Report Dashboard: Tool for Enhancing Feedback to Radiology Trainees about Their Reports.

During their radiology residency, trainees must learn multiple facets of radiology practice, including the writing of radiology reports. An important factor in the trainee's development of reporting skills is feedback from the attending radiologist on the trainee's preliminary reports. The quality and quantity of feedback may vary and are not typically documented. As radiology department workloads have increased and stricter limitations have been imposed on trainee work hours, less time is available for attending radiologists and trainees to perform a joint retrospective review of radiology reports. To compensate, the authors have developed a Web-based dashboard that provides trainees with case-specific feedback about their reports. Components include an attending radiologist-trainee report discrepancy logging and communication system that is integrated with the institutional picture archiving and communication system, an automated preliminary report-final report comparator, modules showing statistics related to the discrepancy logger and report comparator components, and a Web page that unifies these components with image and report display capabilities. Both the actual report feedback and the trainee's use of the system are documented, and the resultant data may be used for evaluating trainee competence in written communication, as mandated by the Accreditation Council for Graduate Medical Education. With these tools, trainees can obtain near-real-time feedback, which may pinpoint issues that can be corrected to improve the quality of their radiology reporting. This system, although it does not supplant face-to-face training sessions with attending radiologists, can augment traditional methods of learning. © RSNA, 2013.

QRSE: a novel metric for the evaluation of trainee radiologist reporting skills.

Diagnostic radiology training programs must produce highly skilled diagnostic radiologists capable of interpreting radiological examinations and communicating results to clinicians. Established training performance tools evaluate interpretive skills, but trainees' competency in reporting skills is also essential. Our semi-automated passive electronic tool entitled the Quantitative Reporting Skills Evaluation (QRSE) allows radiology training programs to evaluate the quantity of edits made to trainee preliminary reports by attending physicians as a metric to evaluate trainee reporting performance. Consecutive report pairs and metadata extracted from the radiology information system were anonymized and exported to a MySQL database. To perform the QRSE, for each report pair, open source software was first utilized to calculate the Levenshtein Percent (LP), the percent of character changes required to convert each preliminary report to its corresponding final report. The average LP (ALP), ALP for each trainee, and standard deviations were calculated. Eighty-four trainees and 56 attending radiologists interpreted 228,543 radiological examinations during the study period. The overall ALP was 6.38 %. Trainee-specific ALPs ranged from 1.1 to 15.3 %. Among trainee-specific ALPs, the standard deviation was 3.7 %. Our analysis identified five trainees with trainee-specific ALPs above 2 standard deviations from the mean and 14 trainees with trainee-specific ALPs less than 1 standard deviation below the mean. The QRSE methodology allows for the passive, quantitative, and longitudinal evaluation of the reporting skills of trainees during diagnostic radiology residency training. The QRSE identifies trainees with high and low levels of edits to their preliminary reports, as a marker for trainee overall reporting skills, and thus represents a novel performance metric for radiology training programs.

Radiology Report Comparator: a novel method to augment resident education.

Attending radiologists routinely edit radiology trainee dictated preliminary reports as part of standard workflow models. Time constraints, high volume, and spatial separation may not always facilitate clear discussion of these changes with trainees. However, these edits can represent significant teaching moments that are lost if they are not communicated back to trainees. We created an electronic method for retrieving and displaying changes made to resident written preliminary reports by attending radiologists during the process of radiology report finalization. The Radiology Information System is queried. Preliminary and final radiology reports, as well as report metadata, are extracted and stored in a database indexed by accession number and trainee/radiologist identity. A web application presents to trainees their 100 most recent preliminary and final report pairs both side by side and in a "track changes" mode. Web utilization audits showed regular utilization by trainees. Surveyed residents stated they compared reports for educational value, to improve future reports, and to improve patient care. Residents stated that they compared reports more frequently after deployment of this software solution and that regular assessment of their work using the Report Comparator allowed them to routinely improve future report quality and improved radiological understanding. In an era with increasing workload demands, trainee work hour restrictions, and decentralization of department resources (e.g., faculty, PACS), this solution helps to retain an important part of the educational experience that would have otherwise run the risk of being lost and provides it to the trainees in an efficient and highly consumable manner.

The relative effect of vendor variability in CT perfusion results: a method comparison study.

OBJECTIVE: There are known interoperator, intraoperator, and intervendor software differences that can influence the reproducibility of quantitative CT perfusion values. The purpose of this study was to determine the relative impact of operator and software differences in CT perfusion variability. MATERIALS AND METHODS: CT perfusion imaging data were selected for 11 patients evaluated for suspected ischemic stroke. Three radiologists each independently postprocessed the source data twice, using four different vendor software applications. Results for cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) were recorded for the lentiform nuclei in both hemispheres. Repeated variables multivariate analysis of variance was used to assess differences in the means of CBV, CBF, and MTT. Bland-Altman analysis was used to assess agreement between pairs of vendors, readers, and read times. RESULTS: Choice of vendor software, but not interoperator or intraoperator disagreement, was associated with significant variability (p < 0.001) in CBV, CBF, and MTT. The mean difference in CT perfusion values was greater for pairs of vendors than for pairs of operators. CONCLUSION: Different vendor software applications do not generate quantitative perfusion results equivalently. Intervendor difference is, by far, the largest cause of variability in perfusion results relative to interoperator and intraoperator difference. Caution should be exercised when interpreting quantitative CT perfusion results because these values may vary considerably depending on the postprocessing software.

Osteoblastoma in the occipital bone: A case report of a rare tumor in the calvarium.

Osteoblastomas infrequently occur in the calvarium, displaying a preference for temporal and frontal bones when it does. We present an unusual case of a large, expansile osteoblastoma in the occipital bone of a 23-year-old man who presented with a nontender lump at the back of his head. Initial computed tomography scan showed a large occipital bone mass, and after additional imaging, a gross total resection was performed. Histopathological examination revealed an osteoblastoma. Although these tumors are benign, overlapping imaging characteristics of lesions affecting the calvarium often present a diagnostic dilemma. This case emphasizes the importance of imaging in the management and work-up of these patients to decrease the risk of complications and assists surgeons in their preoperative planning.

Application of Diffusion Tensor Imaging in Forecasting Neurological Injury and Recovery after Human Cervical Spinal Cord Injury.

The aim of this study is to determine the strength and accuracy of diffusion tensor imaging (DTI) parameters to predict neurological injury and recovery in adult cervical spinal cord injury (SCI). DTI magnetic resonance imaging (MRI) was performed on 23 acute cervical SCI patients within 12 h after injury and on 45 controls utilizing a rapid DTI sequence (∼5 min). Neurological assessments were conducted from within 24 h of injury up to 6 months utilizing detailed International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) examinations. Spearman correlation and receiver operating characteristic (ROC) analysis were used to identify relationships between the DTI parameters at the lesion epicenter and adjacent regions, with injury severity and recovery. In proximity to the anatomical injury (within one level above and below epicenter), there was significant reduction in fractional anisotropy (FA), and elevation in mean diffusivity (MD) and radial diffusivity (RD). DTI values measured one level rostral to the injury epicenter showed stronger correlations with multiple clinical features at several time-points. Area under the curve (AUC) obtained from ROC analysis showed FA (AUC = 0.77) measured at lesion epicenter, and FA (0.83), MD (0.76), and RD (0.83) values measured immediately rostral (one level above) to epicenter discriminate injury severity. Further, MD (0.78) measured at lesion epicenter, and MD (0.79) and RD (0.74) values measured immediately rostral to epicenter discriminate neurological recovery. DTI indices measured immediately rostral to the anatomical level of injury consistently showed better correlation (moderate to strong) and accuracy in predicting neurological injury (FA, r = -0.51 and RD, r = 0.54) and recovery (MD, r = -0.51) than indices measured at the epicenter. There was weak to moderate correlation of all measures at lesion epicenter in predicting neurological injury (FA: r = -0.48; MD: r = 0.23; RD: r = 0.34; axial diffusivity [AD]: r = 0.02) and recovery (FA: r = 0.27; MD: r = -0.44; RD: r = -0.35; AD: r = -0.34).

The effects of anatomic variations on stereotactic laser amygdalohippocampectomy and a proposed protocol for trajectory planning.

BACKGROUND: Stereotactic laser amygdalohippocampectomy (SLAH) is a promising minimally invasive alternative for mesial temporal lobe epilepsy. As seizure outcome has been associated with the extent of amygdalar and hippocampal ablation, it is important to select a safe trajectory optimizing involvement of both structures; however, variations in temporal anatomy significantly affect the overall complexity of planning. OBJECTIVE: To quantify anatomic variables of SLAH and facilitate stereotactic planning by developing a protocol for optimally targeting the amygdalohippocampal complex (AHC). METHODS: We performed a retrospective analysis of 19 SLAHs. Anatomic measurements from preoperative magnetic resonance imaging and laser trajectory measurements from coregistered postoperative magnetic resonance imaging were taken in 11 patients. Simple linear regression analysis was performed to identify significant predictor variables determining ablation extent. Based on these data, a protocol for optimal trajectory planning was developed and subsequently implemented in 8 patients. RESULTS: The medial angle of the laser trajectory correlated with the medial angle of the AHC. The length of amygdalar cannulation was predictive of its ablation volume. All trajectories passed through a posteroinferior corridor formed by the lateral ventricle superiorly and collateral sulcus inferiorly. Our protocol facilitated planning and increased the volume of AHC ablation. CONCLUSION: The medial AHC angle dictates the medial trajectory angle and a path from the posteroinferior corridor through the hippocampus and the center of the amygdala dictates the caudal angle. These observations led to a protocol for long-axis AHC cannulation that maintains an extraventricular trajectory to minimize hemorrhage risk and targets the center of the amygdala to optimize ablation volumes.

Advanced imaging applications for endovascular procedures.

Advanced imaging techniques, particularly in CT and MRI, have become state-of-the-art to support the performance of interventional neuroradiologic procedures. Multidetector CT scanners with submillimeter detectors and real-time workstations have allowed the use of a noninvasive study, CT angiography, as a first-line diagnostic study at many institutions to detect and evaluate the morphology of aneurysms. Follow-up for postsubarachnoid spasm now includes transcranial Doppler, CT angiography, and sometimes perfusion to guide therapy. While both intracranial and extracranial stenosis have long been well evaluated by MR and CT angiography, information about the intimal wall and plaque morphology is now possible. In the setting of acute ischemia, CT with perfusion or MR with diffusion and perfusion has increased the ability to separate territory at risk from infarcted tissue, and can help to guide more appropriate intervention. This article addresses current state-of the-art imaging applications as well as a few techniques on the horizon that show great promise in helping to characterize those lesions amenable to endovascular therapy.