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Accurate, automated MRI series identification is important for many applications, including display ("hanging") protocols, machine learning, and radiomics. The use of the series description or a pixel-based classifier each has limitations. We demonstrate a combined approach utilizing a DICOM metadata-based classifier and selective use of a pixel-based classifier to identify abdominal MRI series. The metadata classifier was assessed alone as Group metadata and combined with selective use of the pixel-based classifier for predictions with less than 70% certainty (Group combined). The overall accuracy (mean and 95% confidence intervals) for Groups metadata and combined on the test dataset were 0.870 CI (0.824,0.912) and 0.930 CI (0.893,0.963), respectively. With this combined metadata and pixel-based approach, we demonstrate accurate classification of 95% or greater for all pre-contrast MRI series and improved performance for some post-contrast series., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

The transfacet minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) is a novel approach available for the management of lumbar spondylolisthesis. It avoids the need to manipulate either of the exiting or traversing nerve roots, both protected by the bony boundaries of the approach. With the advancement in operative technologies such as navigation, mapping, segmentation, and augmented reality (AR), surgeons are prompted to utilize these technologies to enhance their surgical outcomes. A 36-year-old male patient was complaining of chronic progressive lower back pain. He was found to have grade 2 L4/5 spondylolisthesis. We studied the feasibility of a trans-Kambin or a transfacet MIS-TLIF, and decided to proceed with the latter given the wider corridor it provides. Preoperative trajectory planning and level segmentation in addition to intraoperative navigation and image merging were all utilized to provide an AR model to guide us through the surgery. The use of AR can build on the safety and learning of novel surgical approaches to spine pathologies. However, larger high-quality studies are needed to further objectively analyze its impact on surgical outcomes and to expand on its application.

Purpose: During stereotactic radiosurgery (SRS) planning for brain metastases (BM), brain MRIs are reviewed to select appropriate targets based on radiographic characteristics. Some BM are difficult to detect and/or definitively identify and may go untreated initially, only to become apparent on future imaging. We hypothesized that in patients receiving multiple courses of SRS, reviewing the initial planning MRI would reveal early evidence of lesions that developed into metastases requiring SRS., Methods: Patients undergoing two or more courses of SRS to BM within 6 months between 2016 and 2018 were included in this single-institution, retrospective study. Brain MRIs from the initial course were reviewed for lesions at the same location as subsequently treated metastases; if present, this lesion was classified as a "retrospectively identified metastasis" or RIM. RIMs were subcategorized as meeting or not meeting diagnostic imaging criteria for BM (+ DC or -DC, respectively)., Results: Among 683 patients undergoing 923 SRS courses, 98 patients met inclusion criteria. There were 115 repeat courses of SRS, with 345 treated metastases in the subsequent course, 128 of which were associated with RIMs found in a prior MRI. 58% of RIMs were + DC. 17 (15%) of subsequent courses consisted solely of metastases associated with + DC RIMs., Conclusion: Radiographic evidence of brain metastases requiring future treatment was occasionally present on brain MRIs from prior SRS treatments. Most RIMs were + DC, and some subsequent SRS courses treated only + DC RIMs. These findings suggest enhanced BM detection might enable earlier treatment and reduce the need for additional SRS., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background and Objectives: There has been a rise in minimally invasive methods to access the intervertebral disk space posteriorly given their decreased tissue destruction, lower blood loss, and earlier return to work. Two such options include the percutaneous lumbar interbody fusion through the Kambin triangle and the endoscopic transfacet approach. However, without accurate preoperative visualization, these approaches carry risks of damaging surrounding structures, especially the nerve roots. Using novel segmentation technology, our goal was to analyze the anatomic borders and relative sizes of the safe triangle, trans-Kambin, and the transfacet corridors to assist surgeons in planning a safe approach and determining cannula diameters., Methods: The areas of the safe triangle, Kambin, and transfacet corridors were measured using commercially available software (BrainLab, Munich, Germany). For each approach, the exiting nerve root, traversing nerve roots, theca, disk, and vertebrae were manually segmented on 3-dimensional T2-SPACE magnetic resonance imaging using a region-growing algorithm. The triangles' borders were delineated ensuring no overlap between the area and the nerves., Results: A total of 11 patients (65.4 ± 12.5 years, 33.3% female) were retrospectively reviewed. The Kambin, safe, and transfacet corridors were measured bilaterally at the operative level. The mean area (124.1 ± 19.7 mm2 vs 83.0 ± 11.7 mm2 vs 49.5 ± 11.4 mm2) and maximum permissible cannula diameter (9.9 ± 0.7 mm vs 6.8 ± 0.5 mm vs 6.05 ± 0.7 mm) for the transfacet triangles were significantly larger than Kambin and the traditional safe triangles, respectively (P < .001)., Conclusion: We identified, in 3-dimensional, the borders for the transfacet corridor: the traversing nerve root extending inferiorly until the caudal pedicle, the theca medially, and the exiting nerve root superiorly. These results illustrate the utility of preoperatively segmenting anatomic landmarks, specifically the nerve roots, to help guide decision-making when selecting the optimal operative approach., (Copyright © Congress of Neurological Surgeons 2023. All rights reserved.)

Background: There has been heightened interest in performing percutaneous lumbar interbody fusions (percLIFs) through Kambin's triangle, an anatomic corridor allowing entrance into the disc space. However, due to its novelty, there are limited data regarding the long-term benefits of this procedure. Our objective was to determine the long-term efficacy and durability of the percutaneous insertion of an expandable titanium cage through Kambin's triangle without facetectomy., Methods: A retrospective review of patients undergoing percLIF via Kambin's triangle using an expandable titanium cage was performed. Demographics, visual analog scale (VAS) scores, Oswestry Disability Index (ODI), radiographic measurements, perioperative variables, and complications were recorded. VAS, ODI, and radiographic measurements were compared with baseline using the generalized estimating equations assuming normally distributed data. Fusion was assessed with computed tomography (CT) at 1 and 2 years after the procedure., Results: A total of 49 patients were included. Spondylolisthesis, lumbar lordosis (LL), sacral slope, pelvic tilt, and anterior/posterior disc space height were all significantly improved postoperatively at each time point of 3, 6, 12, and 24 months ( P < 0.001). Pelvic incidence-LL mismatch decreased significantly at each follow-up ( P < 0.001) with a mean reduction of 4° by 24 months. VAS back scores reduced by >2 points at the 6, 12, and 24 month follow-ups. ODI scores reduced by >15 points at the 12- and 24-month follow-ups. Of the patients who had 1- and 2-year CT images, fusion rates at those time points were 94.4% (17/18) and 87.5% (7/8), respectively. The mean annual rate of surgically significant adjacent segment disease was 2.74% through an average follow-up of 2.74 years., Conclusion: These results highlight that percLIF, a procedure done without an endoscope or facetectomy, can be performed using an expandable titanium cage through Kambin's triangle with excellent radiographic and clinical results., Clinical Relevance: percLIF via Kambin's triangle is a safe and succesful procedure with long-term improvements in both clinical and radiographic outcomes., Competing Interests: Declaration of Conflicting Interests : Dr Abd-El-Barr is a consultant for Spineology, TrackX, and Depuy. Dr Shaffrey has financial relationships with NuVasive, Medtronic, SI Bone, and Proprio. Dr Wiggins is a strategic advisor for Qure.ai. Dr Chi discloses consulting fees from DePuy and K2M. The authors report that there are no other relevant disclosures pertaining to the content of this manuscript., (This manuscript is generously published free of charge by ISASS, the International Society for the Advancement of Spine Surgery. Copyright © 2023 ISASS. To see more or order reprints or permissions, see http://ijssurgery.com.)

The Duke Liver Dataset contains 2146 abdominal MRI series from 105 patients, including a majority with cirrhotic features, and 310 image series with corresponding manually segmented liver masks., Competing Interests: Disclosures of conflicts of interest: J.A.M. No relevant relationships. Z.Z. No relevant relationships. B.K. No relevant relationships. M.A.M. No relevant relationships. W.F.W. Research funding to institution from The Marcus Foundation and the National Institutes of Health (grant no. R01-NS123275); consulting fees from Qure.ai to author; honorarium paid to author from University of Wisconsin–GE CT Protocols Partnership Medical Advisory Board. M.R.B. Grants or contracts from Siemens Healthineers, Madrigal Pharmaceuticals, NGM Biopharmaceuticals, Metacrine, Corcept, and Carmot Therapeutics (author was primary investigator on research grants to institution); associate editor for Radiology., (© 2023 by the Radiological Society of North America, Inc.)

Objective: While Kambin's Triangle has become an ever more important anatomic window given its proximity to the exiting nerve root, there have been limited studies examining the effect of disease on the corridor. Our goal was to better understand how pathology can affect Kambin's Triangle, thereby altering the laterality of approach for percutaneous lumbar interbody fusion (percLIF)., Methods: The authors performed a single-center retrospective review of patients evaluated for percLIF. The areas of Kambin's Triangle were measured without and with nerve segmentation. For the latter, the lumbosacral nerve roots on 3-dimensional T2 magnetic resonance imaging were manually segmented. Next, the borders of Kambin's Triangle were delineated, ensuring no overlap between the area and nerve above., Results: Fifteen patients (67.5 ± 9.7 years, 46.7% female) were retrospectively reviewed. We measured 150 Kambin's Triangles. The mean areas from L1-S1 were 50.0 ± 12.3 mm 2 , 73.8 ± 12.5 mm 2 , 83.8 ± 12.2 mm 2 , 88.5 ± 19.0 mm 2 , and 116 ± 29.3 mm 2 , respectively. When pathology was present, the areas significantly decreased at L4-L5 (P = 0.046) and L5-S1 (P = 0.049). Higher spondylolisthesis and smaller posterior disk heights were linked with decreased areas via linear regression analysis (P < 0.05). When nerve segmentation was used, the areas were significantly smaller from L1-L5 (P < 0.05). Among 11 patients who underwent surgery, none suffered from postoperative neuropathies., Conclusions: These results illustrate the feasibility of preoperatively segmenting lumbosacral nerves and measuring Kambin's Triangle to help guide surgical planning and determine the ideal laterality of approach for percLIF., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Purpose: We sought to develop a computer-aided detection (CAD) system that optimally augments human performance, excelling especially at identifying small inconspicuous brain metastases (BMs), by training a convolutional neural network on a unique magnetic resonance imaging (MRI) data set containing subtle BMs that were not detected prospectively during routine clinical care., Methods and Materials: Patients receiving stereotactic radiosurgery (SRS) for BMs at our institution from 2016 to 2018 without prior brain-directed therapy or small cell histology were eligible. For patients who underwent 2 consecutive courses of SRS, treatment planning MRIs from their initial course were reviewed for radiographic evidence of an emerging metastasis at the same location as metastases treated in their second SRS course. If present, these previously unidentified lesions were contoured and categorized as retrospectively identified metastases (RIMs). RIMs were further subcategorized according to whether they did (+DC) or did not (-DC) meet diagnostic imaging-based criteria to definitively classify them as metastases based upon their appearance in the initial MRI alone. Prospectively identified metastases (PIMs) from these patients, and from patients who only underwent a single course of SRS, were also included. An open-source convolutional neural network architecture was adapted and trained to detect both RIMs and PIMs on thin-slice, contrast-enhanced, spoiled gradient echo MRIs. Patients were randomized into 5 groups: 4 for training/cross-validation and 1 for testing., Results: One hundred thirty-five patients with 563 metastases, including 72 RIMS, met criteria. For the test group, CAD sensitivity was 94% for PIMs, 80% for +DC RIMs, and 79% for PIMs and +DC RIMs with diameter <3 mm, with a median of 2 false positives per patient and a Dice coefficient of 0.79., Conclusions: Our CAD model, trained on a novel data set and using a single common MR sequence, demonstrated high sensitivity and specificity overall, outperforming published CAD results for small metastases and RIMs - the lesion types most in need of human performance augmentation., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: For percutaneous lumbar fusion (percLIF), magnetic resonance imaging and computed tomography are critical to defining surgical corridors. Currently, these scans are performed separately, and surgeons then use fluoroscopy or neuromonitoring to guide instruments through Kambin's triangle. However, anatomic variations and intraoperative positional changes are possible, meaning that safely accessing Kambin's triangle remains a challenge because nerveroot visualization without endoscopes has not been thoroughly described., Objective: To overcome the known challenges of percLIF and reduce the likelihood of iatrogenic injuries by showing real-time locations of neural and bony anatomy., Methods: The authors demonstrate an intraoperative navigational platform that applies nerve root segmentation and image fusion to assist with percLIF. Five patients from a single institution were included., Results: Of the 5 patients, the mean age was 71 ± 8 years and 3 patients (60%) were female. One patient had general anesthesia while the remaining 4 patients underwent awake surgery with spinal anesthesia. The mean area for the L4-L5 Kambin's triangle was 76.1 ± 14.5 mm 2 . A case example is shown where the side of approach was based on the fact that Kambin's triangle was larger on one side compared with the other. The mean operative time was 170 ± 17 minutes, the mean blood loss was 32 ± 16 mL, and the mean hospital length of stay was 19.6 ± 8.3 hours. No patients developed postoperative complications., Conclusion: This case series demonstrates the successful and safe application of nerve segmentation using magnetic resonance imaging/computed tomography fusion to perform percLIF and provide positive patient outcomes., (Copyright © Congress of Neurological Surgeons 2023. All rights reserved.)

Purpose: To investigate the effect of training data type on generalizability of deep learning liver segmentation models., Materials and Methods: This Health Insurance Portability and Accountability Act-compliant retrospective study included 860 MRI and CT abdominal scans obtained between February 2013 and March 2018 and 210 volumes from public datasets. Five single-source models were trained on 100 scans each of T1-weighted fat-suppressed portal venous (dynportal), T1-weighted fat-suppressed precontrast (dynpre), proton density opposed-phase (opposed), single-shot fast spin-echo (ssfse), and T1-weighted non-fat-suppressed (t1nfs) sequence types. A sixth multisource (DeepAll) model was trained on 100 scans consisting of 20 randomly selected scans from each of the five source domains. All models were tested against 18 target domains from unseen vendors, MRI types, and modality (CT). The Dice-Sørensen coefficient (DSC) was used to quantify similarity between manual and model segmentations., Results: Single-source model performance did not degrade significantly against unseen vendor data. Models trained on T1-weighted dynamic data generally performed well on other T1-weighted dynamic data (DSC = 0.848 ± 0.183 [SD]). The opposed model generalized moderately well to all unseen MRI types (DSC = 0.703 ± 0.229). The ssfse model failed to generalize well to any other MRI type (DSC = 0.089 ± 0.153). Dynamic and opposed models generalized moderately well to CT data (DSC = 0.744 ± 0.206), whereas other single-source models performed poorly (DSC = 0.181 ± 0.192). The DeepAll model generalized well across vendor, modality, and MRI type and against externally sourced data., Conclusion: Domain shift in liver segmentation appears to be tied to variations in soft-tissue contrast and can be effectively bridged with diversification of soft-tissue representation in training data. Keywords: Convolutional Neural Network (CNN), Deep Learning Algorithms, Machine Learning Algorithms, Supervised Learning, CT, MRI, Liver Segmentation Supplemental material is available for this article . © RSNA, 2023., Competing Interests: Disclosures of conflicts of interest: B.K. No relevant relationships. J.M. No relevant relationships. K.L. No relevant relationships. I.H.Z. No relevant relationships. E.B. No relevant relationships. M.C. No relevant relationships. Y.W. No relevant relationships. G.J. No relevant relationships. W.F.W. NIH 1R01-NS123275-01A1 and The Marcus Foundation (research funding not direct support for this study); consulting fees from Qure.ai; payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events from Stanford AIMI Symposium 2021; participation on a Data Safety Monitoring Board or Advisory Board from University of Wisconsin-GE CT Protocols Partnership. M.R.B. Grants/contracts from Siemens Healthineers, Madrigal Pharmaceuticals, Carmot Therapeutics, Corcept, NGM Biopharmaceuticals, and Metacrine., (© 2023 by the Radiological Society of North America, Inc.)

Non-contrast head CT (NCCT) is extremely insensitive for early (< 3-6 h) acute infarct identification. We developed a deep learning model that detects and delineates suspected early acute infarcts on NCCT, using diffusion MRI as ground truth (3566 NCCT/MRI training patient pairs). The model substantially outperformed 3 expert neuroradiologists on a test set of 150 CT scans of patients who were potential candidates for thrombectomy (60 stroke-negative, 90 stroke-positive middle cerebral artery territory only infarcts), with sensitivity 96% (specificity 72%) for the model versus 61-66% (specificity 90-92%) for the experts; model infarct volume estimates also strongly correlated with those of diffusion MRI (r 2  > 0.98). When this 150 CT test set was expanded to include a total of 364 CT scans with a more heterogeneous distribution of infarct locations (94 stroke-negative, 270 stroke-positive mixed territory infarcts), model sensitivity was 97%, specificity 99%, for detection of infarcts larger than the 70 mL volume threshold used for patient selection in several major randomized controlled trials of thrombectomy treatment., (© 2023. The Author(s).)

Objective: The authors sought to analyze the current literature to determine dimensional trends across the lumbar levels of Kambin's triangle, clarify the role of imaging techniques for preoperative planning, and understand the effect of inclusion of the superior articular process (SAP). This compiled knowledge of the triangle is needed to perform successful procedures, reduce nerve root injuries, and help guide surgeons in training., Methods: The authors performed a search of multiple databases using combinations of keywords: Kambin's triangle, size, measurement, safe triangle, and bony triangle. Articles were included if their main findings included measurement of Kambin's triangle. The PubMed, Scopus, Ovid, Cochrane, Embase, and Medline databases were systematically searched for English-language articles with no time frame restrictions through July 2022., Results: Eight studies comprising 132 patients or cadavers were included in the study. The mean ± SD age was 66.69 ± 9.6 years, and 53% of patients were male. Overall, the size of Kambin's triangle increased in area moving down vertebral levels, with L5-S1 being the largest (133.59 ± 4.36 mm2). This trend followed a linear regression model when SAP was kept (p = 0.008) and removed (p = 0.003). There was also a considerable increase in the size of Kambin's triangle if the SAP was removed., Conclusions: Here, the authors have provided the first reported systematic review of the literature of Kambin's triangle, its measurements at each lumbar level, and key areas of debate related to the definition of the working safe zone. These findings indicate that CT is heavily utilized for imaging of the safe zone, the area of Kambin's triangle tends to increase caudally, and variation exists between patients. Future studies should focus on using advanced imaging techniques for preoperative planning and establishing guidelines for surgeons.

As the role of artificial intelligence (AI) in clinical practice evolves, governance structures oversee the implementation, maintenance, and monitoring of clinical AI algorithms to enhance quality, manage resources, and ensure patient safety. In this article, a framework is established for the infrastructure required for clinical AI implementation and presents a road map for governance. The road map answers four key questions: Who decides which tools to implement? What factors should be considered when assessing an application for implementation? How should applications be implemented in clinical practice? Finally, how should tools be monitored and maintained after clinical implementation? Among the many challenges for the implementation of AI in clinical practice, devising flexible governance structures that can quickly adapt to a changing environment will be essential to ensure quality patient care and practice improvement objectives., (© RSNA, 2022.)

Competing Interests: Disclosures of conflicts of interest: W.F.W. Research support grant to author's institution from National Institutes of Health/National Institute of Neurological Disorders and Stroke (grant no. 1R01-NS123275) and the Marcus Foundation; consulting fees from Qure.ai for acting as a strategic advisor; honorarium for being a past participant on medical advisory board for University of Wisconsin–GE CT Protocol Partnership. A.S.T. Member of Radiology: Artificial Intelligence trainee editorial board.

Background: Minimally invasive spine surgery (MISS) has the potential to further advance with the use of robot-assisted (RA) techniques. While RA pedicle screw placement has been extensively investigated, there is a lack of literature on the use of the robot for other tasks, such as accessing Kambin's triangle in percutaneous lumbar interbody fusion (percLIF)., Objective: To characterize the surgical feasibility and preliminary outcomes of an initial case series of 10 patients receiving percLIF with RA cage placement via Kambin's triangle., Methods: We performed a single-center, retrospective review of patients undergoing RA percLIF using robot-guided trajectory to access Kambin's triangle for cage placement. Patients undergoing RA percLIF were eligible for enrollment. Baseline health and demographic information in addition to peri- and postoperative data was collected. The dimensions of each patient's Kambin's triangle were measured., Results: Ten patients and 11 levels with spondylolisthesis were retrospectively reviewed. All patients successfully underwent the planned procedure without perioperative complications. Four patients underwent their procedure with awake anesthesia. The average dimension of Kambin's triangle was 66.3 m2. With the exception of 1 patient who stayed in the hospital for 7 d, the average length of stay was 1.2 d, with 2 patients discharged the day of surgery. No patients suffered postoperative motor or sensory deficits. Spinopelvic parameters and anterior and posterior disc heights were improved with surgery., Conclusion: As MISS continues to evolve, further exploration of robot-guided surgical practice, such as our technique, will lead to creative solutions to challenging anatomical variation and overall improved patient care., (© Congress of Neurological Surgeons 2021.)

Artificial intelligence (AI) tools are rapidly being developed for radiology and other clinical areas. These tools have the potential to dramatically change clinical practice; however, for these tools to be usable and function as intended, they must be integrated into existing radiology systems. In a collaborative effort between the Radiological Society of North America, radiologists, and imaging-focused vendors, the Imaging AI in Practice (IAIP) demonstrations were developed to show how AI tools can generate, consume, and present results throughout the radiology workflow in a simulated clinical environment. The IAIP demonstrations highlight the critical importance of semantic and interoperability standards, as well as orchestration profiles for successful clinical integration of radiology AI tools. Keywords: Computer Applications-General (Informatics), Technology Assessment © RSNA, 2021., Competing Interests: Disclosures of conflicts of interest: W.F.W. University of Wisconsin GE CT Protocol Project Medical Advisory Board participation. K.M. Clinical Champion, Imaging AI in Practice (IAIP): 2020; Co-chair, IAIP Steering Committee, 2021 (unpaid volunteer, Radiological Society of North America [RSNA] provided funds for demonstration [administrative assistance, arrangement for Zoom calls] but no funds for the paper itself); former trainee editorial board member of Radiology: Artificial Intelligence. T.M.S.S. Johns Hopkins School of Medicine, adjunct professor; Marquette University College of Engineering, adjunct professor; RSNA, IAIP technical project manager (consulting fees); RSNA Structured Reporting Committee, Society for Imaging Informatics in Medicine (SIIM) Clinical Data Informaticist Task Force co-chair. S.D.O. No relevant relationships. C.D.C. No relevant relationships. M.D.K. Consulting fees from Alara Imaging paid to author as a shareholder; honoraria for speaking engagements with various topics, including AI, from Honor Health SCGR-Wires (author retained complete editorial control for all of these engagements); travel support from Korean Congress of Radiology, RSNA, SIIM, Digital Pathology Association; periodic uncompensated consulting for Nuance; leadership roles as chair of board of directors for SIIM, co-chair of Common Data Elements committee, RSNA Radiology Informatics Committee (RIC) member, IAIP Task Force member for RSNA, and Informatics Commission member for American College of Radiology; stock/stock holder in Alara Imaging. K.P.A. Unpaid volunteer member of the RSNA RIC, RSNA provided funds for demonstration (administrative assistance, arrangement for Zoom calls) but no funds for the paper itself; co-chair of IAIP Demonstration; support for travel from RSNA for RIC committee meetings; unpaid appointed member of Massachusetts General Brigham Data Science Oversight Committee, which occasionally hears concerns and gives institutional guidance on data and tissue-sharing activities; associate editor of Radiology: Artificial Intelligence., (2021 by the Radiological Society of North America, Inc.)

Conventional measures of radiologist efficiency, such as the relative value unit, fail to account for variations in the complexity and difficulty of a given study. For lumbar spine MRI (LMRI), an ideal performance metric should account for the global severity of lumbar degenerative disease (LSDD) which may influence reporting time (RT), thereby affecting clinical productivity. This study aims to derive a global LSDD metric and estimate its effect on RT. A 10-year archive of LMRI reports comprising 13,388 exams was reviewed. Objective reporting timestamps were used to calculate RT. A natural language processing (NLP) tool was used to extract radiologist-assigned stenosis severity using a 6-point scale (0 = "normal" to 5 = "severe") at each lumbar level. The composite severity score (CSS) was calculated as the sum of each of 18 stenosis grades. The predictive values of CSS, sex, age, radiologist identity, and referring service on RT were examined with multiple regression models. The NLP tool accurately classified LSDD in 94.8% of cases in a validation set. The CSS increased with patient age and differed between men and women. In a univariable model, CSS was a significant predictor of mean RT (R 2  = 0.38, p < 0.001) and independent predictor of mean RT (p < 0.001) controlling for patient sex, patient age, service location, and interpreting radiologist. The predictive strength of CSS was stronger for the low CSS range (CSS = 0-25, R 2  = 0.83, p < 0.001) compared to higher CSS values (CSS > 25, R 2  = 0.15, p = 0.05). Individual radiologist study volume was negatively correlated with mean RT (Pearson's R =  - 0.35, p < 0.001). The composite severity score predicts radiologist reporting efficiency in LMRI, providing a quantitative measure of case complexity which may be useful for workflow planning and performance evaluation., (© 2021. The Author(s).)

Artificial or augmented intelligence, machine learning, and deep learning will be an increasingly important part of clinical practice for the next generation of radiologists. It is therefore critical that radiology residents develop a practical understanding of deep learning in medical imaging. Certain aspects of deep learning are not intuitive and may be better understood through hands-on experience; however, the technical requirements for setting up a programming and computing environment for deep learning can pose a high barrier to entry for individuals with limited experience in computer programming and limited access to GPU-accelerated computing. To address these concerns, we implemented an introductory module for deep learning in medical imaging within a self-contained, web-hosted development environment. Our initial experience established the feasibility of guiding radiology trainees through the module within a 45-min period typical of educational conferences., (© 2021. Society for Imaging Informatics in Medicine.)

Purpose: The purpose of this study is to investigate relationship of patient age and sex to patterns of degenerative spinal stenosis on lumbar MRI (LMRI), rated as moderate or greater by a spine radiologist, using natural language processing (NLP) tools., Methods: In this retrospective, IRB-approved study, LMRI reports acquired from 2007 to 2017 at a single institution were parsed with a rules-based natural language processing (NLP) algorithm for free-text descriptors of spinal canal stenosis (SCS) and neural foraminal stenosis (NFS) at each of six spinal levels (T12-S1) and categorized according to a 6-point grading scale. Demographic differences in the anatomic distribution of moderate (grade 3) or greater SCS and NFS were calculated by sex, and age and within-group differences for NFS symmetry (left vs. right) were calculated as odds ratios., Results: Forty-three thousand two hundred fifty-five LMRI reports (34,947 unique patients, mean age = 54.7; sex = 54.9% women) interpreted by 152 radiologists were studied. Prevalence of significant SCS and NFS increased caudally from T12-L1 to L4-5 though less at L5-S1. NFS was asymmetrically more prevalent on the left at L2-L3 and L5-S1 (p < 0.001). SCS and NFS were more prevalent in men and SCS increased with age at all levels, but the effect size of age was largest at T12-L3. Younger patients (< 50 years) had relatively higher NFS prevalence at L5-S1., Conclusion: NLP can identify patterns of lumbar spine degeneration through analysis of a large corpus of radiologist interpretations. Demographic differences in stenosis prevalence shed light on the natural history and pathogenesis of LSDD.

This report presents a hands-on introduction to natural language processing (NLP) of radiology reports with deep neural networks in Google Colaboratory (Colab) to introduce readers to the rapidly evolving field of NLP. The implementation of the Google Colab notebook was designed with code hidden to facilitate learning for noncoders (ie, individuals with little or no computer programming experience). The data used for this module are the corpus of radiology reports from the Indiana University chest x-ray collection available from the National Library of Medicine's Open-I service. The module guides learners through the process of exploring the data, splitting the data for model training and testing, preparing the data for NLP analysis, and training a deep NLP model to classify the reports as normal or abnormal. Concepts in NLP, such as tokenization, numericalization, language modeling, and word embeddings, are demonstrated in the module. The module is implemented in a guided fashion with the authors presenting the material and explaining concepts. Interactive features and extensive text commentary are provided directly in the notebook to facilitate self-guided learning and experimentation with the module. Keywords: Neural Networks, Negative Expression Recognition, Natural Language Processing, Computer Applications, Informatics © RSNA, 2021., Competing Interests: Disclosures of Conflicts of Interest: W.F.W. disclosed no relevant relationships. F.K. Activities related to the present article: disclosed no relevant relationships. Activities not related to the present article: author is consultant to MD.ai; employed by DASA. Other relationships: disclosed no relevant relationships. I.S. disclosed no relevant relationships. L.M.P. Activities related to the present article: associate editor of Radiology: Artificial Intelligence. Activities not related to the present article: disclosed no relevant relationships. Other relationships: disclosed no relevant relationships., (2021 by the Radiological Society of North America, Inc.)

Purpose: Reporting efficiency is commonly used to measure performance and quality in diagnostic imaging. For academic centers, balancing the clinical demand for efficient reporting and educational obligation to trainees remains a major challenge. The objective of this study was to quantify the effect of trainee education on reporting efficiency over the academic year (July to June) for a single diagnostic imaging examination type., Methods: The authors reviewed a 10-year data set of lumbar spinal MRI reports and time-stamp data and compared change in mean reporting time for trainee versus attending radiologist-only reports. Odds ratios, linear regression, and correlation analysis were performed to evaluate relationships of mean and cumulative reporting times, volume, and study month., Results: Mean reporting time for the trainee group peaked in July (287.2 ± 4.9 min). The largest month-to-month increase was from June to July (+46.3 min, P < .01) for the trainees, and July showed the largest deviation from annualized mean reporting time (odds ratio, 1.31; 95% confidence interval, 1.16-1.47; P < .001). Mean reporting time improved linearly over the course of the academic year from July to June for trainees (R 2  = 0.59, P = .002), but this effect was absent in the attending radiologist-only group (P = .52)., Conclusions: This study quantifies the effect of trainee education on reporting efficiency and models the operational "learning curve" of improved performance over the academic year. These data may inform staffing and workflow improvement efforts in academic radiology departments., (Copyright © 2020 American College of Radiology. Published by Elsevier Inc. All rights reserved.)

Artificial intelligence and machine learning (AI-ML) have taken center stage in medical imaging. To develop as leaders in AI-ML, radiology residents may seek a formative data science experience. The authors piloted an elective Data Science Pathway (DSP) for 4th-year residents at the authors' institution in collaboration with the MGH & BWH Center for Clinical Data Science (CCDS). The goal of the DSP was to provide an introduction to AI-ML through a flexible schedule of educational, experiential, and research activities. The study describes the initial experience with the DSP tailored to the AI-ML interests of three senior radiology residents. The authors also discuss logistics and curricular design with common core elements and shared mentorship. Residents were provided dedicated, full-time immersion into the CCDS work environment. In the initial DSP pilot, residents were successfully integrated into AI-ML projects at CCDS. Residents were exposed to all aspects of AI-ML application development, including data curation, model design, quality control, and clinical testing. Core concepts in AI-ML were taught through didactic sessions and daily collaboration with data scientists and other staff. Work during the pilot period led to 12 accepted abstracts for presentation at national meetings. The DSP is a feasible, well-rounded introductory experience in AI-ML for senior radiology residents. Residents contributed to model and tool development at multiple stages and were academically productive. Feedback from the pilot resulted in establishment of a formal AI-ML curriculum for future residents. The described logistical, planning, and curricular considerations provide a framework for DSP implementation at other institutions. Supplemental material is available for this article. © RSNA, 2020., Competing Interests: Disclosures of Conflicts of Interest: W.F.W. disclosed no relevant relationships. M.T.C. disclosed no relevant relationships. K.M. Activities related to the present article: affiliated with Brigham and Women’s Hospital. Activities not related to the present article: institution received grant from RSNA R&E Foundation and an SAR research grant. Other relationships: disclosed no relevant relationships. S.A.G. disclosed no relevant relationships. E.G. disclosed no relevant relationships. M.H.R. Activities related to the present article: disclosed no relevant relationships. Activities not related to the present article: institution received grant from Stand Up to Cancer Foundation, Lustgarten Foundation, and National Institutes of Health. Other relationships: disclosed no relevant relationships. G.C.G. disclosed no relevant relationships. K.P.A. Activities related to the present article: affiliated with Brigham and Women’s Hospital, Harvard Medical School, MGH & BWH Center for Clinical Data Science. Activities not related to the present article: board membership Academy for Radiology and Biomedical Imaging Research (board of directors 2012–2014, executive board 2019–present); travel accommodations for RSNA Radiology Informatics Committee; travel reimbursement for ASNR/RSNA CERT Meeting; American College of Radiology, Data Science Institute, senior scientist for education, no funds received. Other relationships: disclosed no relevant relationships., (2020 by the Radiological Society of North America, Inc.)

Purpose: Infected (mycotic) intracranial aneurysms (IIA) are a prevalent source of morbidity in patients with systemic infection. Unlike saccular aneurysms, ruptured IIA frequently presents with intracerebral hemorrhage (ICH), and the appearance of ruptured IIA on CTA overlaps with the CTA "Spot Sign" (SS), an imaging finding in non-infectious, spontaneous ICH. The purpose of this study was to investigate the imaging and clinical features which may differentiate these two entities on CTA for which treatment strategies differ substantially., Methods: In an IRB-approved, retrospective case series, we compared 14 patients with confirmed IIA and 14 patients with positive SS due to other non-infectious etiology (SS(+) ICH). Clinical history, laboratory studies, and CTA reports and images were reviewed to define imaging characteristics of IIA and SS(+) ICH, including the diagnostic criteria for SS used in clinical trials., Results: A total of 7/14 patients (50.0%) diagnosed with IIA had ICH at presentation. Of these, 3/7 patients (42.9%) with ruptured IIA and ICH met diagnostic imaging criteria of SS. The remaining 4/7 patients did not meet criteria due to presence of a connecting vessel. Compared with SS(+) ICH of non-infectious etiology, patients with ruptured IIA were younger (40.7 vs. 66.4 years) and had higher rates of IVDU and bacteremia (p < 0.01) and lower rates of hypertension (p < 0.01). Hematoma volume was similar in both groups, but lobar location was more frequent in ruptured IIA (p = 0.06). Mortality at 1 year from diagnosis was equally high in both groups (42.9%)., Conclusion: This study characterizes ruptured IIA as an imaging mimic of SS and provides a framework for differentiating these lesions, allowing prompt diagnosis and appropriate treatment.

Three-dimensional cinematic rendering (3DCR) is an emerging postprocessing technique for computed tomography (CT) and CT angiography (CTA) that produces photorealistic, volumetric images. In contrast to conventional volume rendering techniques, 3DCR depicts life-like shadowing and surface reflection, which can improve the perception of depth and complex anatomic spatial relationships. This tool allows clinical neuroimagers to study, explore, and teach the complex relational anatomy of the cerebral vessels and skull in a more intuitive manner. The purpose of this report is to introduce the physical and optical principles behind 3DCR and to explore applications of 3DCR in modern cerebrovascular imaging. Using CTA source data, we describe our approach to visualizing cerebrovascular anatomy and disease and introduce three simple, reproducible techniques through a series of case vignettes. First, we show how selective manipulation of rendered models can imitate cadaveric dissection. Next, we discuss surface rendering as a means of recapitulating the neurologic physical exam. Last, we provide a step-by-step method of simulating the operating room perspective in visualizing cerebrovascular disease. In our experience, 3DCR proves most useful for visualizing structures at the vessel-skull interface, which can be difficult to assess with conventional imaging methods. 3DCR, therefore, complements traditional 2-dimensional and 3-dimensional imaging methods and serves as an emerging tool for neuroimagers to communicate with and educate other clinicians., (© 2020 by the American Society of Neuroimaging.)

Background Diagnostic uncertainty in CT of possible intracranial hemorrhage requires short-interval follow-up imaging, resulting in reduced efficiency of care and higher costs. Purpose To quantify the diagnostic performance of dual-energy CT versus simulated single-energy CT in the differentiation of small foci of intracranial hemorrhage from calcium. Materials and Methods Images from consecutive unenhanced dual-energy CT of the head in patients from a single emergency department obtained from December 2014 to April 2016 were reviewed retrospectively for hyperattenuating intracranial foci. Ground truth was established from reference standard comparison CT or MRI. Foci were divided into development and test sets. Development set foci regions of interest were used to derive candidate CT attenuation thresholds for virtual noncalcium (VNCa) and calcium images. Test set foci were used for threshold validation, and diagnostic performance and confidence were evaluated for two readers blinded to final diagnosis. Statistical comparisons were made with exact binomial tests or repeated-measures analysis of variance. Results The study included 137 patients (65 years ± 17; 70 men) with 146 foci. Foci were divided into a development set ( n = 105) and a test set ( n = 41). Quantitative analysis of the development set produced candidate thresholds of 44 HU for VNCa images and 7 HU for calcium-only images, yielding diagnostic accuracies for the test set of 88% (36 of 41 foci; 95% confidence interval [CI]: 78%, 98%) and 95% (39 of 41 foci; 95% CI: 88%, 100%), respectively. Dual-energy CT improved reader accuracy from 90% (reader 1, 37 of 41 foci; 95% CI: 81%, 99%) and 93% (reader 2, 38 of 41 foci; 95% CI: 85%, 100%) to 100% (both readers, 41 of 41 foci; 95% CI: 100%, 100%). Diagnostic confidence (classifications rated as "certain") increased from 71% (29 of 41 foci; 95% CI: 57%, 85%) to 90% (37 of 41 foci; 95% CI: 81%, 99%) for reader 1 ( P = .019) and from 46% (19 of 41 foci; 95% CI: 31%, 62%) to 85% (35 of 41 foci; 95% CI: 75%, 96%) for reader 2 ( P = .0001). Conclusion Dual-energy CT showed high diagnostic performance in the differentiation of small foci of intracranial hemorrhage from calcium and improved diagnostic accuracy and confidence in the initial evaluation of suspected hemorrhage. © RSNA, 2019 See also the editorial by Kotsenas in this issue.

Acute subdural hemorrhage (SDH) is commonly encountered by emergency radiologists in the setting of trauma. When history or imaging evidence of trauma is absent, the differential diagnosis for SDH should be expanded. Intracranial aneurysm rupture is a rare and underrecognized cause of SDH which may present without concurrent subarachnoid hemorrhage. The mechanism of aneurysmal SDH is controversial, but understanding the anatomic microenvironment of the aneurysm provides insight and clarifies aneurysm features predisposing to subdural compartment rupture. Aneurysmal SDH is a neurosurgical emergency and its treatment strategies differ from traumatic SDH. Outcomes are poor if treatment is delayed; thus, radiologists play a central role in recognizing this uncommon but potentially devastating complication of aneurysm rupture. The goal of this article is to familiarize radiologists with clinical and imaging characteristics of aneurysmal SDH and review pertinent anatomy, risk factors, and potential etiologies. Aneurysmal rupture can easily be overlooked in the routine workup of atraumatic SDH, and radiologists must know when to recommend vascular imaging to avoid the catastrophic consequences of a missed diagnosis.

Computed tomography is often the first-line diagnostic imaging modality in the evaluation of patients with neurologic emergencies. A patient-centered approach to radiation dose management in emergent neuroimaging thus revolves around the appropriate use of computed tomography, including clinical decision support for ordering providers, thoughtful protocol design, the use of available technological advances in computed tomography, and radiation exposure monitoring at a population level. A multifaceted approach can help to minimize radiation exposure to individual patients while preserving diagnostic quality imaging., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Purpose: To assess the impact of hepatobiliary phase images obtained during intravenous gadoxetate disodium-enhanced liver MRI in the planning of image-guided liver tumor ablations., Methods: This institutional review board-approved retrospective study included 34 patients (21 men, 13 women, ages 25-80) who underwent 36 liver MRI examinations with gadoxetate disodium within 12 weeks prior to image-guided thermal ablation of 62 liver tumors during 36 procedures. Visibility of bile ducts, subdivided by branch order, on hepatobiliary phase images was compared to standard MRI sequence images by an attending abdominal radiologist and fellow. Interventional decision making (whether or not to ablate and technical plan) using hepatobiliary phase images was compared with standard MRI sequences by the ablationists. The technical success and adverse events of ablation procedures were noted., Results: Bile duct visibility was significantly increased by at least one branch order in 18/36 (50%) examinations (p < 0.0001). Interventional decisions were significantly impacted in 15 (41.7%) of 36 ablation procedures (p < 0.0001), including changes to the technical plan in six (16.7%) of these procedures (p = 0.005). Technical success was achieved for 60/62 (97%) of tumors. Mild (grade 1) adverse events occurred in 4/36 (11%) procedures; no biliary complications occurred., Conclusions: Use of hepatobiliary phase images obtained during gadoxetate disodium-enhanced liver MRI impacted both when and how to perform image-guided liver tumor ablations in our practice.

Background: Radiation-induced fibrosis (RIF) of musculoskeletal tissue is a common complication of radiation therapy for extremity soft-tissue sarcoma, with no standardized strategy for prevention and treatment. Angiotensin-(1-7) (Ang-[1-7]), a well-tolerated endogenous heptapeptide hormone with antitumor and antifibrotic properties, was tested as a radioprotectant for RIF and stiffening of irradiated muscles., Methods: Male CD-1 mice were randomized to one of three treatment groups: control, simulated sarcoma radiation therapy to the gastrocnemius and soleus muscles, or radiation therapy along with continuous Ang-(1-7) delivery initiated three days before radiation therapy. The biologically equivalent dose of radiation (∼100.3 Gy) absorbed by normal musculature during the course of radiation therapy for extremity sarcoma was delivered by means of four dose fractions of 7.3 Gy over two weeks. Fibrosis (n = 5 per group) and mechanical properties (n = 4 to 6 per group) of the muscles were measured at six weeks and four months after radiation therapy, and the intramuscular concentration of the profibrotic cytokines transforming growth factor-beta (TGF-β) and connective tissue growth factor (CTGF) (n = 8 to 10 per group) were measured at six weeks., Results: Interstitial (p < 0.01) and perivascular (p < 0.05) fibrosis increased significantly in the muscles treated with radiation therapy alone versus the nonirradiated controls at both six weeks (interstitial, +89%; perivascular, +112%) and four months (interstitial, +154%; perivascular, +88%). The muscles treated with radiation alone also exhibited increased tension (p < 0.01) versus nonirradiated controls at both six weeks (+779%) and four months (+1761%) when placed under 5% strain, and at four months (+1390%; p < 0.001) under 10% strain. At four months, muscle stiffness had increased in the mice treated with radiation therapy alone (+90%; p = 0.002) compared with nonirradiated controls. TGF-β production was also greater in this group at six weeks (+37%; p = 0.06) versus control. Ang-(1-7) administration prevented RIF and stiffening, with no differences observed for any other outcome between those receiving radiation therapy with Ang-(1-7) and the nonirradiated controls. Likewise, Ang-(1-7) mitigated the increase in TGF-β and CTGF concentration from radiation therapy., Conclusions: Ang-(1-7) attenuated RIF, stiffening, and production of profibrotic cytokines that were elevated in mouse skeletal muscles after simulated radiation therapy for extremity sarcoma., Clinical Relevance: Ang-(1-7) may serve as a potential therapy for the prevention of RIF in patients who require radiation therapy as adjuvant treatment for soft-tissue sarcoma., (Copyright © 2016 by The Journal of Bone and Joint Surgery, Incorporated.)

Temozolomide (TMZ) and BCNU have demonstrated anti-glioma synergism in preclinical models. We report final data from a prospective, multi-institutional study of BCNU wafers and early TMZ followed by radiation therapy with TMZ in patients with newly diagnosed malignant glioma. 65 patients were consented in 4 institutions, and 46 patients (43 GBM, 3 AA) were eligible for analysis. After resection and BCNU wafer placement, TMZ began on day four postoperatively. Radiation and TMZ (RT/TMZ) were then administered, followed by monthly TMZ at 200 mg/m2 for the first 26 patients, which was reduced to 150 mg/m2 for the remaining 20 patients. Non-hematologic toxicities were minimal. Nine of 27 patients (33 %) who received 200 mg/m2 TMZ, but only 1 of 20 (5 %) who received 150 mg/m2, experienced grade 3/4 thrombocytopenia. Median progression free survival (PFS) and overall survival (OS) period was 8.5 and 18 months, respectively. The 1-year OS rate was 76 %, which is a significant improvement compared with the historical control 1-year OS rate of 59 % (p = 0.023). However, there was no difference in 1-year OS compared with standard RT/TMZ (p = 0.12) or BCNU wafer followed by RT/TMZ (p = 0.87) in post hoc analyses. Early post-operative TMZ can be safely administered with BCNU wafers following resection of malignant glioma at the 150 mg/m2 dose level. Although there was an OS benefit compared to historical control, there was no indication of benefit for BCNU wafers and early TMZ in addition to standard RT/TMZ or early TMZ in addition to regimens of BCNU wafers followed by RT/TMZ.

Purpose: Resected brain metastases (BM) require radiation therapy to reduce local recurrence. Whole brain radiation therapy (WBRT) reduces recurrence, but with potential toxicity. Postoperative stereotactic radiosurgery (SRS) is a strategy without prospective data and problematic target delineation. SRS delivered in the preoperative setting (neoadjuvant, or NaSRS) allows clear target definition and reduction of intraoperative dissemination of tumor cells., Methods and Materials: Our treatment of resectable BM with NaSRS was begun in 2005. Subsequently, a prospective trial of NaSRS was undertaken. A total of 47 consecutively treated patients (23 database and 24 prospective trial) with a total of 51 lesions were reviewed. No statistical difference was observed between the 2 cohorts, and they were combined for analysis. The median follow-up time was 12 months (range, 1-58 months), and the median age was 57. A median of 1 day elapsed between NaSRS and resection. The median diameter of lesions was 3.04 cm (range, 1.34-5.21 cm), and the median volume was 8.49 cc (range, 0.89-46.7 cc). A dose reduction strategy was used, with a median dose of 14 Gy (range, 11.6-18 Gy) prescribed to 80% isodose., Results: Kaplan-Meier overall survival was 77.8% and 60.0% at 6 and 12 months. Kaplan-Meier local control was 97.8%, 85.6%, and 71.8% at 6, 12, and 24 months, respectively. Five of 8 failures were proved pathologically without radiation necrosis. There were no perioperative adverse events. Ultimately, 14.8% of the patients were treated with WBRT. Local failure was more likely with lesions >10 cc (P=.01), >3.4 cm (P=.014), with a trend in surface lesions (P=.066) and eloquent areas (P=.052). Six of the 8 failures had an obvious dural attachment or proximity to draining veins., Conclusions: NaSRS can be performed safely and effectively with excellent results without documented radiation necrosis. Local control was excellent even in the setting of large (>3 cm) lesions. The strong majority of patients were able to avoid WBRT. NaSRS merits consideration in a multi-institution trial., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background: Chronic ethanol (EtOH) leads to disruptions in resting electroencephalogram (EEG) activity and in sleep patterns that can persist into the withdrawal period. These disruptions have been suggested to be predictors of relapse. The thalamus is a key structure involved in both normal brain oscillations, such as sleep-related oscillations, and abnormal rhythms found in disorders such as epilepsy and Parkinson's disease. Previously, we have shown progressive changes in mouse thalamic T-type Ca channels during chronic intermittent EtOH exposures that occurred in parallel with alterations in theta (4 to 8 Hz) EEG patterns., Methods: Two groups of 8-week-old male C57BL/6 mice were implanted with wireless EEG/electromyogram (EMG) telemetry and subjected to 4 weeks of chronic, intermittent EtOH vapor exposure and withdrawal. During the week after the final withdrawal, mice were administered ethosuximide (ETX; 200 mg/kg) or saline. EEG data were analyzed via discrete Fourier transform, and sleep-scored for further analysis., Results: Chronic intermittent EtOH exposure produced changes in the diurnal rhythms of the delta (0.5 to 4 Hz) and theta bands that persisted into a subsequent week of sustained withdrawal. These disruptions were restored with the T-channel blocker ETX. Repeated EtOH exposures preferentially increased the relative proportion of lower frequency power (delta and theta), whereas higher frequencies (8 to 24 Hz) were decreased. The EtOH-induced decreases in relative power for the higher frequencies continued into the sustained withdrawal week for both groups. Increases in absolute delta and theta power were observed in averaged nonrapid eye movement and rapid eye movement sleep spectral data during withdrawal in ETX-treated animals, suggesting increased sleep intensity., Conclusions: These results suggest that persistent alterations in delta and theta EEG rhythms during withdrawal from chronic intermittent EtOH exposure can be ameliorated with ETX and that this treatment might also increase sleep intensity during withdrawal., (Copyright © 2012 by the Research Society on Alcoholism.)

Predisposition to Achilles tendon (AT) ruptures in middle-aged individuals may be associated with age-related changes to inherent passive biomechanical properties of the gastrocnemius-Achilles (GC-AT) muscle-tendon unit, due to known muscle-tendon structural changes in normal aging. The goal of this study was to determine whether the passive biomechanical response of the GC-AT muscle-tendon unit was altered with age in 6 young (8 months) and 6 middle-aged (24 months) F344xBN hybrid rats from the National Institute on Aging colony. Fung's quasilinear viscoelastic (QLV) model was used to determine in vivo history and time-dependent load-relaxation response of the GC-AT. Effective stiffness and modulus were also estimated using linear regression analysis. Fung's QLV revealed a significantly decreased magnitude of the relaxation response (parameter C, p=0.026) in middle-aged animals compared to young animals (0.108±0.007 vs. 0.144±0.015), with similar time-dependent viscous GC-AT properties (τ(1), τ(2)). The product of elastic parameters (A*B), which represents the initial slope of the elastic response, was significantly increased by 50% in middle-aged rats (p=0.014). Estimated GC-AT stiffness increased 28% at peak tensions in middle-aged rats (2.7±0.2 N/mm) compared to young rats (1.9±0.2 N/mm; p=0.036). While the limitations of this animal model must be considered, the changes we describe could be associated with the observation that GC-AT pathology and injury is more common in middle-aged individuals. Further studies are necessary to characterize the load-to-failure behavior of AT in middle-aged compared to young animals., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Botulinum Neurotoxin A (BoNT-A) injections have been used for the treatment of muscle contractures and spasticity. This study assessed the influence of (BoNT-A) injections on passive biomechanical properties of the muscle-tendon unit. Mousegastrocnemius muscle (GC) was injected with BoNT-A (n = 18) or normal saline (n = 18) and passive, non-destructive, in vivo load relaxation experimentation was performed to examine how the muscle-tendon unit behaves after chemical denervation with BoNT-A. Injection of BoNT-A impaired passive muscle recovery (15% vs. 35% recovery to pre-stretching baseline, p < 0.05) and decreased GC stiffness (0.531 ± 0.061 N/mm vs. 0.780 ± 0.037 N/mm, p < 0.05) compared to saline controls. The successful use of BoNT-A injections as an adjunct to physical therapy may be in part attributed to the disruption of the stretch reflex; thereby modulating in vivo passive muscle properties. However, it is also possible that BoNT-A injection may alter the structure of skeletal muscle; thus modulating the in vivo passive biomechanical properties of the muscle-tendon unit.

Passive viscoelastic properties of muscle-tendon units are key determinants of intra- and post-operative success. Atrophied, retracted, and stiff muscle-tendon units are technically challenging to manipulate and perform poorly after surgical repair. This study employs botulinum neurotoxin A (BoNT-A)-mediated inhibition of presynaptic acetylcholine release to examine in vivo neural contributions to soft-tissue biomechanical properties. In vivo load-relaxation and active muscle contractile force testing protocols were performed in the rat rotator cuff model. The passive properties were assessed using linear regression analysis and Fung's quasi-linear viscoelastic (QLV) model. BoNT-A injected muscle--tendon units had a significant reduction in force of contraction (p = 0.001). When compared to saline injected controls, the BoNT-A significantly decreased parameter 'A' of the QLV model, which represents the linear elastic response (p = 0.032). The viscous properties in the BoNT-A treatment group were not significantly different from saline injected controls, as determined by comparison of QLV model parameters 'C,' 'τ(1),' and 'τ(2).' In conclusion, neural tone contributes significantly to muscle-tendon unit passive biomechanical properties. Pre-surgical treatment with BoNT-A may improve the rehabilitation of muscle by altering its passive elastic properties. Accordingly, pharmacological modulation of skeletal muscle stiffness with BoNT-A increases flexibility, potentially improving function. Chemical denervation with BoNT-A may also improve the manipulation of stiff and difficult to mobilize muscles during surgical procedures.

Purpose: The chemical denervation that results from botulinum neurotoxin A (BoNT-A) causes a temporary, reversible paresis that can result in easier surgical manipulation of the muscle-tendon unit in the context of tendon rupture and repair. The purpose of the study was to determine whether BoNT-A injections can be used to temporarily and reversibly modulate active and passive skeletal muscle properties., Methods: Male CD1 mice weighing 40-50 g were divided into a 1-week postinjection group (n = 13: n = 5 saline and n = 8 BoNT-A) and a 2-week postinjection group (n = 17: n = 7 saline and n = 10 BoNT-A). The animals had in vivo muscle force testing and in vivo biomechanical evaluation., Results: There was a substantial decline in the maximal single twitch amplitude (p < .05) and tetanic amplitude (p < .05) at one week and at 2 weeks after BoNT-A injection, when compared to saline-injected controls. BoNT-A injection significantly reduced the peak passive properties of the muscle-tendon unit as a function of displacement at one week (p < .05). Specifically, the stiffness of the BoNT-A injected muscle-tendon unit was 0.417 N/mm compared to the control saline injected group, which was 0.634 N/mm, a 35% reduction in stiffness (p < .05)., Conclusions: Presurgical treatment with BoNT-A might improve the surgical manipulation of the muscle-tendon unit, thus improving surgical outcomes. The results implicate neural tone as a substantial contributor to the passive repair tension of the muscle-tendon unit. The modulation of neural tone through temporary, reversible paresis is a novel approach that might improve intraoperative and postoperative passive muscle properties, allowing for progressive rehabilitation while protecting the surgical repair site., (Copyright © 2011 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.)

Some epilepsies are linked to inherited traits, but many appear to arise through acquired alterations in neuronal excitability. Status epilepticus (SE) is associated with numerous changes that promote spontaneous recurrent seizures (SRS), and studies have suggested that hippocampal T-type Ca(2+) channels underlie increased bursts of activity integral to the generation of these seizures. The thalamus also contributes to epileptogenesis, but no studies have directly assessed channel alterations in the thalamus during SE or subsequent periods of SRS. We therefore investigated longitudinal changes in thalamic T-type channels in a mouse pilocarpine model of epilepsy. T-type channel gene expression was not affected during SE; however Ca(V)3.2 mRNA was significantly upregulated at both 10 d post-SE (seizure-free period) and 31 d post-SE (SRS-period). Overall T-type current density increased during the SRS period, and the steady-state inactivation shifted from a more hyperpolarized membrane potential during the latent stage, to a more depolarized membrane potential during the SRS period. Ca(V)3.2 functional involvement was verified with Ca(V)3.2 inhibitors that reduced the native T-type current in mice 31 d post-SE, but not in controls. Burst discharges of thalamic neurons reflected the changes in whole-cell currents, and we used a computational model to relate changes observed during epileptogenesis to a decreased tendency to burst in the seizure-free period, or an increased tendency to burst during the period of SRS. We conclude that SE produces an acquired channelopathy by inducing long-term alterations in thalamic T-type channels that contribute to characteristic changes in excitability observed during epileptogenesis and SRS.