Dr. Abdelkader Mahammedi is Assistant Professor of Neuroradiology at the Department of Radiology, Stanford University School of Medicine. He completed medical school at the University of Algiers in Algeria, and then continued a postdoctoral research fellowship in Diagnostic Radiology at Johns Hopkins Hospital under the mentorship of Dr. Stanley Siegelman. Prior to becoming a specialist neuroradiologist, Dr. Mahammedi completed a Neuroradiology fellowship at the Cleveland Clinic Imaging Institute after having completed residencies in both Nuclear Medicine and Diagnostic Radiology. His specialty interests include brain tumors, stroke, small vessel disease, head and neck imaging, and functional magnetic resonance imaging (fMRI). Dr. Mahammedi has contributed to over 30 peer-reviewed publications, including lead authoring multiple articles in high-impact journals. During the beginning of the COVID-19 pandemic, he led and collaborated with multiple institutions from Italy, Spain, and Brazil. His work was considered the first and largest study in the literature that systematically characterized neurological symptoms and neuroimaging features in hospitalized COVID-19 patients, which was published in the journal Radiology. Recently, he has published the most recent multicenter and global COVID-19-related articles, which were featured by the international media in more than 25 languages including 200 newspapers, CNN, BBC, NPR, local televised broadcasts, and the 2020 RSNA Press Release. He co-authored multiple books, including “Imaging Appearance of Migraine and Tension Type Headache” and "Humanizing BrainTumors: Strategies for You and Your Physician" which was published in 2022. Dr. Mahammedi has received numerous awards and honors, including being selected as a semi-finalist for the prestigious Cornelius Dyke Award of the American Society of Neuroradiology (ASNR) 2021, and Best Case Award at the American Institute of Radiologic Pathology (AIRP) in Neuroradiology. In 2014, he was recognized as one of the authors with top-cited articles for his work in the Journal of Thoracic Imaging at the Society of Thoracic Imaging (STR) meeting, where he introduced a new technique for early detection of pulmonary hypertension on CT scans.

Clinical Focus

  • Neuroradiology
  • Diagnostic Radiology

Academic Appointments

  • Clinical Assistant Professor, Radiology

Professional Education

  • Board Certification: American Board of Radiology, Diagnostic Radiology (2018)
  • Fellowship, Cleveland Clinic Imaging Institute, OH (2018)
  • Residency, Johns Hopkins University, MD (2014)
  • Residency, University of Toledo, OH (2017)
  • Internship, Brookdale University Hospital Medical Center, NY (2013)
  • Medical Education: University of Algiers (I.N.E.S.S.M) (2008) Algeria

All Publications

  • Lessons learned from evolving frameworks in adult glioblastoma. Handbook of clinical neurology Lechpammer, M., Mahammedi, A., Pomeranz Krummel, D. A., Sengupta, S. 2023; 192: 131-140


    Glioblastoma (GBM) is the most common and aggressive malignant adult brain tumor. Significant effort has been directed to achieve a molecular subtyping of GBM to impact treatment. The discovery of new unique molecular alterations has resulted in a more effective classification of tumors and has opened the door to subtype-specific therapeutic targets. Morphologically identical GBM may have different genetic, epigenetic, and transcriptomic alterations and therefore different progression trajectories and response to treatments. With a transition to molecularly guided diagnosis, there is now a potential to personalize and successfully manage this tumor type to improve outcomes. The steps to achieve subtype-specific molecular signatures can be extrapolated to other neuroproliferative as well as neurodegenerative disorders.

    View details for DOI 10.1016/B978-0-323-85538-9.00011-0

    View details for PubMedID 36796938

  • Imaging Appearance of Migraine and Tension Type Headache. Neurologic clinics Mahammedi, A., Wang, L. L., Vagal, A. S. 2022; 40 (3): 491-505

    View details for DOI 10.1016/j.ncl.2022.02.002

    View details for PubMedID 35871781

  • Small Vessel Disease, a Marker of Brain Health: What the Radiologist Needs to Know AMERICAN JOURNAL OF NEURORADIOLOGY Mahammedi, A., Wang, L. L., Williamson, B. J., Khatri, P., Kissela, B., Sawyer, R. P., Shatz, R., Khandwala, V., Vagal, A. 2021: 650-660


    Small vessel disease, a disorder of cerebral microvessels, is an expanding epidemic and a common cause of stroke and dementia. Despite being almost ubiquitous in brain imaging, the clinicoradiologic association of small vessel disease is weak, and the underlying pathogenesis is poorly understood. The STandards for ReportIng Vascular changes on nEuroimaging (STRIVE) criteria have standardized the nomenclature. These include white matter hyperintensities of presumed vascular origin, recent small subcortical infarcts, lacunes of presumed vascular origin, prominent perivascular spaces, cerebral microbleeds, superficial siderosis, cortical microinfarcts, and brain atrophy. Recently, the rigid categories among cognitive impairment, vascular dementia, stroke, and small vessel disease have become outdated, with a greater emphasis on brain health. Conventional and advanced small vessel disease imaging markers allow a comprehensive assessment of global brain heath. In this review, we discuss the pathophysiology of small vessel disease neuroimaging nomenclature by means of the STRIVE criteria, clinical implications, the role of advanced imaging, and future directions.

    View details for DOI 10.3174/ajnr.A7302

    View details for Web of Science ID 000704411700001

    View details for PubMedID 34620594

    View details for PubMedCentralID PMC9089248

  • Brain and Lung Imaging Correlation in Patients with COVID-19: Could the Severity of Lung Disease Reflect the Prevalence of Acute Abnormalities on Neuroimaging? A Global Multicenter Observational Study AMERICAN JOURNAL OF NEURORADIOLOGY Mahammedi, A., Ramos, A., Bargallo, N., Gaskill, M., Kapur, S., Saba, L., Carrete, H., Sengupta, S., Salvador, E., Hilario, A., Revilla, Y., Sanchez, M., Perez-Nunez, M., Bachir, S., Zhang, B., Oleaga, L., Sergio, J., Koren, L., Martin-Medina, P., Wang, L., Benegas, M., Ostos, F., Gonzalez-Ortega, G., Calleja, P., Udstuen, G., Williamson, B., Khandwala, Chadalavada, S., Woo, D., Vagal, A. 2021; 42 (6): 1008-1016


    Our aim was to study the association between abnormal findings on chest and brain imaging in patients with coronavirus disease 2019 (COVID-19) and neurologic symptoms.In this retrospective, international multicenter study, we reviewed the electronic medical records and imaging of hospitalized patients with COVID-19 from March 3, 2020, to June 25, 2020. Our inclusion criteria were patients diagnosed with Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) infection with acute neurologic manifestations and available chest CT and brain imaging. The 5 lobes of the lungs were individually scored on a scale of 0-5 (0 corresponded to no involvement and 5 corresponded to >75% involvement). A CT lung severity score was determined as the sum of lung involvement, ranging from 0 (no involvement) to 25 (maximum involvement).A total of 135 patients met the inclusion criteria with 132 brain CT, 36 brain MR imaging, 7 MRA of the head and neck, and 135 chest CT studies. Compared with 86 (64%) patients without acute abnormal findings on neuroimaging, 49 (36%) patients with these findings had a significantly higher mean CT lung severity score (9.9 versus 5.8, P < .001). These patients were more likely to present with ischemic stroke (40 [82%] versus 11 [13%], P < .0001) and were more likely to have either ground-glass opacities or consolidation (46 [94%] versus 73 [84%], P = .01) in the lungs. A threshold of the CT lung severity score of >8 was found to be 74% sensitive and 65% specific for acute abnormal findings on neuroimaging. The neuroimaging hallmarks of these patients were acute ischemic infarct (28%), intracranial hemorrhage (10%) including microhemorrhages (19%), and leukoencephalopathy with and/or without restricted diffusion (11%). The predominant CT chest findings were peripheral ground-glass opacities with or without consolidation.The CT lung disease severity score may be predictive of acute abnormalities on neuroimaging in patients with COVID-19 with neurologic manifestations. This can be used as a predictive tool in patient management to improve clinical outcome.

    View details for DOI 10.3174/ajnr.A7072

    View details for Web of Science ID 000658573800006

    View details for PubMedID 33707278

    View details for PubMedCentralID PMC8191655

  • Imaging of Neurologic Disease in Hospitalized Patients with COVID-19: An Italian Multicenter Retrospective Observational Study RADIOLOGY Mahammedi, A., Saba, L., Vagal, A., Leali, M., Rossi, A., Gaskill, M., Sengupta, S., Zhang, B., Carriero, A., Bachir, S., Crivelli, P., Pasche, A., Premi, E., Padovani, A., Gasparotti, R. 2020; 297 (2): E270-E273

    View details for DOI 10.1148/radiol.2020201933

    View details for Web of Science ID 000581882100004

    View details for PubMedID 32437313

    View details for PubMedCentralID PMC7587295

  • Tumor Habitat-derived Radiomic Features at Pretreatment MRI That Are Prognostic for Progression-free Survival in Glioblastoma Are Associated with Key Morphologic Attributes at Histopathologic Examination: A Feasibility Study RADIOLOGY-ARTIFICIAL INTELLIGENCE Verma, R., Correa, R., Hill, V. B., Statsevych, V., Bera, K., Beig, N., Mahammedi, A., Madabhushi, A., Ahluwalia, M., Tiwari, P. 2020; 2 (6): e190168


    To identify radiomic features extracted from the tumor habitat on routine MR images that are prognostic for progression-free survival (PFS) and to assess their morphologic basis with corresponding histopathologic attributes in glioblastoma (GBM).In this retrospective study, 156 pretreatment GBM MR images (gadolinium-enhanced T1-weighted, T2-weighted, and fluid-attenuated inversion recovery [FLAIR] images) were curated. Of these 156 images, 122 were used for training (90 from The Cancer Imaging Archive and 32 from the Cleveland Clinic, acquired between December 1, 2011, and May 1, 2018) and 34 were used for validation. The validation set was obtained from the Ivy Glioblastoma Atlas Project database, for which the percentage extent of 11 histologic attributes was available on corresponding histopathologic specimens of the resected tumor. Following expert annotations of the tumor habitat (necrotic core, enhancing tumor, and FLAIR-hyperintense subcompartments), 1008 radiomic descriptors (eg, Haralick texture features, Laws energy features, co-occurrence of local anisotropic gradient orientations [CoLIAGe]) were extracted from the three MRI sequences. The top radiomic features were obtained from each subcompartment in the training set on the basis of their ability to risk-stratify patients according to PFS. These features were then concatenated to create a radiomics risk score (RRS). The RRS was independently validated on a holdout set. In addition, correlations (P < .05) of RRS features were computed, with the percentage extent of the 11 histopathologic attributes, using Spearman correlation analysis.RRS yielded a concordance index of 0.80 on the validation set and constituted radiomic features, including Laws (capture edges, waves, ripple patterns) and CoLIAGe (capture disease heterogeneity) from enhancing tumor and FLAIR hyperintensity. These radiomic features were correlated with histopathologic attributes associated with disease aggressiveness in GBM, particularly tumor infiltration (P = .0044) and hyperplastic blood vessels (P = .0005).Preliminary findings demonstrated significant associations of prognostic radiomic features with disease-specific histologic attributes, with implications for risk-stratifying patients with GBM for personalized treatment decisions. Supplemental material is available for this article. © RSNA, 2020.

    View details for DOI 10.1148/ryai.2020190168

    View details for Web of Science ID 000826480100002

    View details for PubMedID 33330847

    View details for PubMedCentralID PMC7706886

  • Prediction of recurrent glioblastoma after laser interstitial thermal therapy: The role of diffusion imaging. Neuro-oncology advances Mahammedi, A., Bachir, S., Escott, E. J., Barnett, G. H., Mohammadi, A. M., Larvie, M. 2019; 1 (1): vdz021


    Evaluate the utility of diffusion-weighted imaging (DWI) for the assessment of local recurrence of glioblastoma (GBM) on imaging performed 24 h following MRI-guided laser interstitial thermal therapy (LITT). We hypothesize that microscopic peritumoral infiltration correlates with early subtle variations on DWI images and apparent diffusion coefficient (ADC) maps.Of 64 patients with GBM treated with LITT, 39 had MRI scans within 24 h after undergoing LITT. Patterns on DWI images and ADC maps 24 h following LITT were correlated with areas of future GBM recurrence identified through coregistration of subsequent MRI examinations. In the areas of suspected recurrence within the periphery of post-LITT lesions, signal intensity values on ADC maps were recorded and compared with the remaining peritumoral ring.Thirty-nine patients with GBM met the inclusion criteria. For predicting recurrent GBM, areas of decreased DWI signal and increased signal on ADC maps within the expected peritumoral ring of restricted diffusion identified 24 h following LITT showed 86.1% sensitivity, 75.2% specificity, and high correlation (r = 0.53) with future areas of GBM recurrence (P < .01). Areas of future recurrence demonstrated a 37% increase in the ADC value (P < .001), compared with findings in the surrounding treated peritumoral region. A significantly greater area under the receiver operating characteristics curve was determined for ADC values (P < .01).DWI obtained 24 h following LITT can help predict the location of GBM recurrence months before the development of abnormal enhancement. This may alter future treatment planning, perhaps suggesting areas that may be targeted for additional therapy.

    View details for DOI 10.1093/noajnl/vdz021

    View details for PubMedID 32642657

    View details for PubMedCentralID PMC7212867

  • USE-Evaluator: Performance metrics for medical image segmentation models supervised by uncertain, small or empty reference annotations in neuroimaging. Medical image analysis Ostmeier, S., Axelrod, B., Isensee, F., Bertels, J., Mlynash, M., Christensen, S., Lansberg, M. G., Albers, G. W., Sheth, R., Verhaaren, B. F., Mahammedi, A., Li, L. J., Zaharchuk, G., Heit, J. J. 2023; 90: 102927


    Performance metrics for medical image segmentation models are used to measure the agreement between the reference annotation and the predicted segmentation. Usually, overlap metrics, such as the Dice, are used as a metric to evaluate the performance of these models in order for results to be comparable. However, there is a mismatch between the distributions of cases and the difficulty level of segmentation tasks in public data sets compared to clinical practice. Common metrics used to assess performance fail to capture the impact of this mismatch, particularly when dealing with datasets in clinical settings that involve challenging segmentation tasks, pathologies with low signal, and reference annotations that are uncertain, small, or empty. Limitations of common metrics may result in ineffective machine learning research in designing and optimizing models. To effectively evaluate the clinical value of such models, it is essential to consider factors such as the uncertainty associated with reference annotations, the ability to accurately measure performance regardless of the size of the reference annotation volume, and the classification of cases where reference annotations are empty. We study how uncertain, small, and empty reference annotations influence the value of metrics on a stroke in-house data set regardless of the model. We examine metrics behavior on the predictions of a standard deep learning framework in order to identify suitable metrics in such a setting. We compare our results to the BRATS 2019 and Spinal Cord public data sets. We show how uncertain, small, or empty reference annotations require a rethinking of the evaluation. The evaluation code was released to encourage further analysis of this topic

    View details for DOI 10.1016/

    View details for PubMedID 37672900

  • Complete Response of a Patient With a Mismatch Repair Deficient Aggressive Pituitary Adenoma to Immune Checkpoint Inhibitor Therapy: A Case Report. Neurosurgery Shah, S., Manzoor, S., Rothman, Y., Hagen, M., Pater, L., Golnik, K., Mahammedi, A., Lin, A. L., Bhabhra, R., Forbes, J. A., Sengupta, S. 2022; 91 (2): e51-e56


    Aggressive pituitary adenomas (APAs) are pituitary tumors that are refractory to standard treatments and carry a poor prognosis. Current treatment guidelines are not standardized but combine surgical resection, radiation therapy, and chemotherapy. Temozolomide is the only chemotherapeutic agent with documented effectiveness and is recommended for APA in European Society of Endocrinology clinical guidelines.A 57-year-old man presented with visual deterioration and bitemporal hemianopsia. MRI of the brain demonstrated a sellar mass suspected to be pituitary macroadenoma with displacement of the stalk and optic nerve impingement. The patient underwent stereotactic endoscopic transsphenoidal resection of the mass. Postoperative MRI demonstrated gross total resection. Pathology revealed a sparsely granulated corticotroph adenoma with malignant transformation. Immunohistochemistry showed loss of expression of MLH1 and PMS2 in the tumor cells. Proton therapy was recommended given an elevated Ki67 index and p53 positivity. Before radiotherapy, there was no radiographic evidence of residual tumor. Temozolomide therapy was initiated after surveillance MRI showed recurrence at 16 months postoperatively. However, MRI demonstrated marked progression after 3 cycles. Next-generation sequencing using the MSK-IMPACT platform identified somatic mutations in MLH1 Y548lfs*9 and TP53 R337C . Immunotherapy with ipilimumab/nivolumab was initiated, and MRI demonstrated no residual tumor burden 34 months postoperatively.APA is a tumor with frequent recurrence and a short median expected length of survival. Here, we demonstrate the utility of immunotherapy in a single case report of APA, with complete resolution of recurrent APA and improved survival compared with life expectancy.

    View details for DOI 10.1227/neu.0000000000002024

    View details for PubMedID 35544035

  • Imaging of Headache Attributed to Vascular Disorders. Neurologic clinics Wang, L. L., Mahammedi, A., Vagal, A. S. 2022; 40 (3): 507-530


    Imaging is essential in the diagnosis of vascular causes of headaches. With advances in technology, there are increasing options of imaging modalities to choose from, each with its own advantages and disadvantages. This article will focus on imaging pearls and pitfalls of vascular causes of headaches. These include aneurysms, vasculitides, vascular malformations, and cerebral venous thrombosis.

    View details for DOI 10.1016/j.ncl.2022.02.004

    View details for PubMedID 35871782

  • Pearls & Oy-sters: Pivoting Treatment Regimens of Pediatric Atypical Teratoid Rhabdoid Tumors to Optimize Care in Adult ATRT: A Case Report NEUROLOGY Rao, R., Koehler, A., Rothman, Y., Turner, B., Denlinger, J., Erickson, M., Hagen, M., Braverman, T. S., Mahammedi, A., Golnik, K., Zuccarello, M., Gozal, Y. M., Broun, E., Chi, S. N., Sengupta, S. 2022; 98 (17): 726-730


    Atypical teratoid rhabdoid tumor (ATRT) is a highly malignant embryonal tumor of the CNS, largely affecting pediatric patients, with exceedingly rare cases in adults at an estimated annual incidence of 1/1,000,000. We report a unique case of ATRT in a 43-year-old female patient who first presented with progressive focal headaches. Imaging revealed a sellar mass with suprasellar extensions, which was partially removed via a transsphenoidal resection. The tumor aggressively recurred just 1 month postoperatively. Her care team pursued a novel treatment plan by using a slightly modified COG ACNS 0332 regimen, which involved radiation, followed by 4 cycles of monthly chemotherapy including vincristine, cyclophosphamide, and cisplatin. Hematopoietic stem cells were collected between radiation and chemotherapy in the event that the patient required stem cell salvage therapy postadjuvant chemotherapy. The MRIs taken at 2 and 4 months postrecurrence indicated a substantial decrease in tumor volume, with corresponding clinical improvements to cranial nerve deficits. Given the scarcity of literature on adult cases of ATRT and the lack of a standard of care for these cases, discussing the efficacy of our patient's treatment plan may aid clinical decision making for adult ATRT cases.

    View details for DOI 10.1212/WNL.0000000000200196

    View details for Web of Science ID 000787364300010

    View details for PubMedID 35256482

  • Role of imaging in rare COVID-19 vaccine multiorgan complications INSIGHTS INTO IMAGING Cau, R., Mantini, C., Monti, L., Mannelli, L., Di Dedda, E., Mahammedi, A., Nicola, R., Roubil, J., Suri, J. S., Cerrone, G., Fanni, D., Faa, G., Carriero, A., Scuteri, A., Francone, M., Saba, L. 2022; 13 (1): 44


    As of September 18th, 2021, global casualties due to COVID-19 infections approach 200 million, several COVID-19 vaccines have been authorized to prevent COVID-19 infection and help mitigate the spread of the virus. Despite the vast majority having safely received vaccination against SARS-COV-2, the rare complications following COVID-19 vaccination have often been life-threatening or fatal. The mechanisms underlying (multi) organ complications are associated with COVID-19, either through direct viral damage or from host immune response (i.e., cytokine storm). The purpose of this manuscript is to review the role of imaging in identifying and elucidating multiorgan complications following SARS-COV-2 vaccination-making clear that, in any case, they represent a minute fraction of those in the general population who have been vaccinated. The authors are both staunch supporters of COVID-19 vaccination and vaccinated themselves as well.

    View details for DOI 10.1186/s13244-022-01176-w

    View details for Web of Science ID 000768833900002

    View details for PubMedID 35286509

    View details for PubMedCentralID PMC8919150

  • Association Between CT Angiogram Collaterals and CT Perfusion in Delayed Time Windows for Large Vessel Occlusion Ischemic Strokes JOURNAL OF STROKE & CEREBROVASCULAR DISEASES Voleti, S., Aziz, Y. N., Vidovich, J., Corcoran, B., Zhang, B., Mistry, E., Khandwala, V., Khatri, P., Tomsick, T., Wang, L., Mahammedi, A., Vagal, A. 2022; 31 (3): 106263


    Recent endovascular trials have established the use of CT perfusion (CTP) in endovascular treatment selection for patients with large vessel occlusions (LVO). However, the relationship between CTP and collateral circulation is unclear in delayed time windows. We explored the relationship between CT Angiogram (CTA) collaterals and CTP parameters in delayed time windows (6-24 hours).We utilized a single institutional, retrospective stroke registry of consecutive patients between May 2016 and May 2018 with anterior LVO with CTA and CTP imaging within 6-24 hours of stroke onset. We graded baseline collaterals on single phase CTA using modified Tan collateral score (0-3) and dichotomized into good (2-3) and poor (0-1) collaterals. We recorded automated CTP parameters, including estimated ischemic core (cerebral blood flow (CBF)<30%), penumbra (Tmax>6 s), and mismatch ratio. We used Mann-Whitney test and linear regression to assess associations.We included 48 patients with median age of 62 years (IQR= 52-72), median core of 17.5 mL (IQR=0-47), and median penumbra of 117.5 mL (IQR= 62-163.5). Patients with good collaterals had smaller median core (0 mL, IQR=0-12 mL vs. 40.5 mL, IQR=15-60 mL) (p < 0.001), smaller median penumbra (83.5 mL, IQR=43-135 mL vs. 142.5 mL, IQR=77-190 mL) (p = 0.04), larger median mismatch ratio (13.7, IQR=5.7-58.0 vs. 3.1, IQR=2.1-5.0) (p < 0.001), and lower median hypoperfusion intensity ratio (0.23, IQR=0-0.44 vs. 0.52, IQR=0.45-0.63) (p < 0.001) than patients with poor collaterals.In delayed time window LVO patients, good CTA collaterals are significantly associated with smaller CTP core, smaller penumbra, larger mismatch ratio, and lower hypoperfusion intensity ratio. CTA collateral assessment could be a potential valuable surrogate to perfusion imaging, particularly in stroke centers where CTP is unavailable.

    View details for DOI 10.1016/j.jstrokecerebrovasdis.2021.106263

    View details for Web of Science ID 000795432800016

    View details for PubMedID 34954596

  • Automated grading of enlarged perivascular spaces in clinical imaging data of an acute stroke cohort using an interpretable, 3D deep learning framework SCIENTIFIC REPORTS Williamson, B. J., Khandwala, V., Wang, D., Maloney, T., Sucharew, H., Horn, P., Haverbusch, M., Alwell, K., Gangatirkar, S., Mahammedi, A., Wang, L. L., Tomsick, T., Gaskill-Shipley, M., Cornelius, R., Khatri, P., Kissela, B., Vagal, A. 2022; 12 (1): 788


    Enlarged perivascular spaces (EPVS), specifically in stroke patients, has been shown to strongly correlate with other measures of small vessel disease and cognitive impairment at 1 year follow-up. Typical grading of EPVS is often challenging and time consuming and is usually based on a subjective visual rating scale. The purpose of the current study was to develop an interpretable, 3D neural network for grading enlarged perivascular spaces (EPVS) severity at the level of the basal ganglia using clinical-grade imaging in a heterogenous acute stroke cohort, in the context of total cerebral small vessel disease (CSVD) burden. T2-weighted images from a retrospective cohort of 262 acute stroke patients, collected in 2015 from 5 regional medical centers, were used for analyses. Patients were given a label of 0 for none-to-mild EPVS (< 10) and 1 for moderate-to-severe EPVS (≥ 10). A three-dimensional residual network of 152 layers (3D-ResNet-152) was created to predict EPVS severity and 3D gradient class activation mapping (3DGradCAM) was used for visual interpretation of results. Our model achieved an accuracy 0.897 and area-under-the-curve of 0.879 on a hold-out test set of 15% of the total cohort (n = 39). 3DGradCAM showed areas of focus that were in physiologically valid locations, including other prevalent areas for EPVS. These maps also suggested that distribution of class activation values is indicative of the confidence in the model's decision. Potential clinical implications of our results include: (1) support for feasibility of automated of EPVS scoring using clinical-grade neuroimaging data, potentially alleviating rater subjectivity and improving confidence of visual rating scales, and (2) demonstration that explainable models are critical for clinical translation.

    View details for DOI 10.1038/s41598-021-04287-4

    View details for Web of Science ID 000743649400052

    View details for PubMedID 35039524

    View details for PubMedCentralID PMC8764081

  • The use of ARMCan app to improve the quality of life in breast cancer patients with chemobrain The use of ARMCan app to improve the quality of life in breast cancer patients with chemobrain. Koehler, A. 2022
  • Complications in COVID-19 patients: Characteristics of pulmonary embolism CLINICAL IMAGING Cau, R., Pacielli, A., Fatemeh, H., Vaudano, P., Arru, C., Crivelli, P., Stranieri, G., Suri, J. S., Mannelli, L., Conti, M., Mahammedi, A., Kalra, M., Saba, L. 2021; 77: 244-249


    The purpose of this study is to evaluate chest CT imaging features, clinical characteristics, laboratory values of COVID-19 patients who underwent CTA for suspected pulmonary embolism. We also examined whether clinical, laboratory or radiological characteristics could be associated with a higher rate of PE.This retrospective study included 84 consecutive patients with laboratory-confirmed SARS-CoV-2 who underwent CTA for suspected PE. The presence and localization of PE as well as the type and extent of pulmonary opacities on chest CT exams were examined and correlated with the information on comorbidities and laboratory values for all patients.Of the 84 patients, pulmonary embolism was discovered in 24 patients. We observed that 87% of PE was found to be in lung parenchyma affected by COVID-19 pneumonia. Compared with no-PE patients, PE patients showed an overall greater lung involvement by consolidation (p = 0.02) and GGO (p < 0.01) and a higher level of D-Dimer (p < 0,01). Moreover, the PE group showed a lower level of saturation (p = 0,01) and required more hospitalization (p < 0,01).Our study showed a high incidence of PE in COVID-19 pneumonia. In 87% of patients, PE was found in lung parenchyma affected by COVID-19 pneumonia with a worse CT severity score and a greater number of lung lobar involvement compared with non-PE patients. CT severity, lower level of saturation, and a rise in D-dimer levels could be an indication for a CTPA.Certain findings of non-contrast chest CT could be an indication for a CTPA.

    View details for DOI 10.1016/j.clinimag.2021.05.016

    View details for Web of Science ID 000743263000004

    View details for PubMedID 34029929

    View details for PubMedCentralID PMC8130594

  • Progressive myelopathy in myelin oligodendrocyte glycoprotein antibody-associated disease: A new mimicker of progressive multiple sclerosis? MULTIPLE SCLEROSIS AND RELATED DISORDERS Marcucci, S. B., Elkasaby, M., Walch, R., Zare-Shahabadi, A., Mahammedi, A., Abboud, H., Zabeti, A. 2021; 52: 102964


    Background MOG-IgG-associated disease (MOGAD) in adults typically presents as a monophasic or relapsing optic, spinal, or opticospinal neuroinflammatory syndrome. Current recommendations discourage testing for MOG-IgG in patients with clinical or paraclinical findings more typical of MS, or in patients with a progressive clinical course. However, this approach may impede identification of the full phenotypic spectrum of this recently described disorder. Methods We retrospectively reviewed charts of 39 MOG-IgG-seropositive patients from two Ohio-based neuroimmunology centers to identify unusual disease patterns. Those with a progressive course were included in this case series. Results We describe five cases of progressive myelopathy associated with MOG-IgG. Most patients had features suggestive of MS, including typical MRI and cerebrospinal fluid findings. However, MOG-IgG positive patients with progressive myelopathy showed poor response to MS disease modifying therapy and better response to intravenous immunoglobulins similar to previous reports on MOGAD patients. Conclusion MOG-IgG-seropositive patients may present with progressive myelopathy and may have a clinical and radiologic phenotype suggestive of primary progressive or secondary progressive MS, or progressive solitary sclerosis. MOG-IgG testing should be considered in patients with progressive myelopathy, especially if clinically worsening on MS therapy.

    View details for DOI 10.1016/j.msard.2021.102964

    View details for Web of Science ID 000669497800002

    View details for PubMedID 33915519

  • Reuse of Molecules for Glioblastoma Therapy PHARMACEUTICALS Koehler, A., Karve, A., Desai, P., Arbiser, J., Plas, D. R., Qi, X., Read, R. D., Sasaki, A. T., Gawali, V. S., Toukam, D. K., Bhattacharya, D., Kallay, L., Krummel, D., Sengupta, S. 2021; 14 (2)


    Glioblastoma multiforme (GBM) is a highly malignant primary brain tumor. The current standard of care for GBM is the Stupp protocol which includes surgical resection, followed by radiotherapy concomitant with the DNA alkylator temozolomide; however, survival under this treatment regimen is an abysmal 12-18 months. New and emerging treatments include the application of a physical device, non-invasive 'tumor treating fields' (TTFs), including its concomitant use with standard of care; and varied vaccines and immunotherapeutics being trialed. Some of these approaches have extended life by a few months over standard of care, but in some cases are only available for a minority of GBM patients. Extensive activity is also underway to repurpose and reposition therapeutics for GBM, either alone or in combination with the standard of care. In this review, we present select molecules that target different pathways and are at various stages of clinical translation as case studies to illustrate the rationale for their repurposing-repositioning and potential clinical use.

    View details for DOI 10.3390/ph14020099

    View details for Web of Science ID 000622910400001

    View details for PubMedID 33525329

    View details for PubMedCentralID PMC7912673

  • Neurofibromatosis Type 2 (NF2) and the Implications for Vestibular Schwannoma and Meningioma Pathogenesis INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Bachir, S., Shah, S., Shapiro, S., Koehler, A., Mahammedi, A., Samy, R. N., Zuccarello, M., Schorry, E., Sengupta, S. 2021; 22 (2)


    Patients diagnosed with neurofibromatosis type 2 (NF2) are extremely likely to develop meningiomas, in addition to vestibular schwannomas. Meningiomas are a common primary brain tumor; many NF2 patients suffer from multiple meningiomas. In NF2, patients have mutations in the NF2 gene, specifically with loss of function in a tumor-suppressor protein that has a number of synonymous names, including: Merlin, Neurofibromin 2, and schwannomin. Merlin is a 70 kDa protein that has 10 different isoforms. The Hippo Tumor Suppressor pathway is regulated upstream by Merlin. This pathway is critical in regulating cell proliferation and apoptosis, characteristics that are important for tumor progression. Mutations of the NF2 gene are strongly associated with NF2 diagnosis, leading to benign proliferative conditions such as vestibular schwannomas and meningiomas. Unfortunately, even though these tumors are benign, they are associated with significant morbidity and the potential for early mortality. In this review, we aim to encompass meningiomas and vestibular schwannomas as they pertain to NF2 by assessing molecular genetics, common tumor types, and tumor pathogenesis.

    View details for DOI 10.3390/ijms22020690

    View details for Web of Science ID 000611334800001

    View details for PubMedID 33445724

    View details for PubMedCentralID PMC7828193

  • Pyogenic brain abscess, ventriculitis and diffuse meningitis with fatal outcome in an adult: Radiologic-pathologic correlation☆,. Radiology case reports Mahammedi, A., Bachir, S., Purdy, J., Larvie, M., Buehler, M. 2018; 13 (5): 1063-1068


    Rupture of brain abscesses with evolution into ventriculitis with meningitis may result in sudden and dramatic worsening of the clinical situation. We present a 57-year-old man with such an event and fatal outcome. Multiple imaging modalities including computed tomography and advanced magnetic resonance imaging were correlated with gross specimen and histologic images. The differential diagnosis of multiple lesions with ring enhancement and prominent perifocal edema includes mainly infectious and neoplastic processes, such as brain abscess, metastasis, and multicentric glioblastoma. Pyogenic ventriculitis is an uncommon manifestation of severe intracranial infection that might be clinically obscure. We discuss the characteristic magnetic resonance findings of brain abscess and its complications, including meningitis and ventriculitis with emphasis on the role of diffusion-weighted and fluid-attenuated inversion recovery imaging.

    View details for DOI 10.1016/j.radcr.2018.04.019

    View details for PubMedID 30228844

    View details for PubMedCentralID PMC6137902

  • Semiautomatic Volumetric Tumor Segmentation for Hepatocellular Carcinoma: Comparison between C-arm Cone Beam Computed Tomography and MRI ACADEMIC RADIOLOGY Tacher, V., Lin, M., Chao, M., Gjesteby, L., Bhagat, N., Mahammedi, A., Ardon, R., Mory, B., Geschwind, J. 2013; 20 (4): 446-452


    To evaluate the precision and reproducibility of a semiautomatic tumor segmentation software in measuring tumor volume of hepatocellular carcinoma (HCC) before the first transarterial chemo-embolization (TACE) on contrast-enhancement magnetic resonance imaging (CE-MRI) and intraprocedural dual-phase C-arm cone beam computed tomography (DP-CBCT) images.Nineteen HCCs were targeted in 19 patients (one per patient) who underwent baseline diagnostic CE-MRI and an intraprocedural DP-CBCT. The images were obtained from CE-MRI (arterial phase of an intravenous contrast medium injection) and DP-CBCT (delayed phase of an intra-arterial contrast medium injection) before the actual embolization. Three readers measured tumor volumes using a semiautomatic three-dimensional volumetric segmentation software that used a region-growing method employing non-Euclidean radial basis functions. Segmentation time and spatial position were recorded. The tumor volume measurements between image sets were compared using linear regression and Student's t-test, and evaluated with intraclass-correlation analysis (ICC). The inter-rater Dice similarity coefficient (DSC) assessed the segmentation spatial localization.All 19 HCCs were analyzed. On CE-MRI and DP-CBCT examinations, respectively, 1) the mean segmented tumor volumes were 87 ± 8 cm(3) (2-873) and 92 ± 10 cm(3) (1-954), with no statistical difference of segmented volumes by readers of each tumor between the two imaging modalities and the mean time required for segmentation was 66 ± 45 seconds (21-173) and 85 ± 34 seconds (17-214) (P = .19); 2) the ICCs were 0.99 and 0.974, showing a strong correlation among readers; and 3) the inter-rater DSCs showed a good to excellent inter-user agreement on the spatial localization of the tumor segmentation (0.70 ± 0.07 and 0.74 ± 0.05, P = .07).This study shows a strong correlation, a high precision, and excellent reproducibility of semiautomatic tumor segmentation software in measuring tumor volume on CE-MRI and DP-CBCT images. The use of the segmentation software on DP-CBCT and CE-MRI can be a valuable and highly accurate tool to measure the volume of hepatic tumors.

    View details for DOI 10.1016/j.acra.2012.11.009

    View details for Web of Science ID 000317028900009

    View details for PubMedID 23498985

    View details for PubMedCentralID PMC3602801

  • Pulmonary Artery Measurements in Pulmonary Hypertension The Role of Computed Tomography JOURNAL OF THORACIC IMAGING Mahammedi, A., Oshmyansky, A., Hassoun, P. M., Thiemann, D. R., Siegelman, S. S. 2013; 28 (2): 96-103


    We studied the relationship between pulmonary artery diameter (PAD) as measured on computed tomography (CT) and pulmonary artery pressure (PAP) with the specific goal of assessing the reliability of various measurements on high-resolution chest CT as predictors of pulmonary hypertension (PH).In a preliminary study we determined the method of measuring the main PAD (mPAD) that best correlated with PAP. Using this approach we measured mPAD on CT and correlated the data with PAP obtained from right heart catheterization in 298 patients with known PH and in 102 controls. Various metrics were analyzed for their specificity and sensitivity as screening measurements for PH.The mean PAD and mPAD/ascending aorta diameter (AAD) ratio were found to have the highest correlation with PAP (r=0.51 and 0.53, respectively; P<0.001). A threshold of mPAD>29.5 mm was found to be 70.8% sensitive and 79.4% specific for PH, and an mPAD threshold >31.5 mm had a sensitivity and specificity of 52.0% and 90.2%, respectively. An mPAD/AAD ratio >1 was found to be 70.8% sensitive and 76.5% specific for PH. There was no significant correlation between mPAD and body surface area or age (r=0.04 and 0.07, respectively). A strong statistically significant difference (P<0.0001) was found between mPAD and mPAD/AAD ratio between controls and the PH group.mPAD and mPAD/AAD ratio may be used to detect PH in patients of any age or with any body surface area.

    View details for DOI 10.1097/RTI.0b013e318271c2eb

    View details for Web of Science ID 000315350700008

    View details for PubMedID 23096163