Publications by authors named "S M Ahmadi"

765 Publications

Simultaneous imputation and classification using Multigraph Geometric Matrix Completion (MGMC): Application to neurodegenerative disease classification.

Artif Intell Med 2021 Jul 8;117:102097. Epub 2021 May 8.

Department of Computer Aided Medical Procedures (CAMP), Technical University of Munich (TUM), Boltzmannstr. 3, 85748 Garching, Germany; German Center for Vertigo and Balance Disorders (DSGZ), Ludwig-Maximilians University (LMU), Fraunhoferstr. 20, 82152, Planegg, Germany. Electronic address:

Large-scale population-based studies in medicine are a key resource towards better diagnosis, monitoring, and treatment of diseases. They also serve as enablers of clinical decision support systems, in particular computer-aided diagnosis (CADx) using machine learning (ML). Numerous ML approaches for CADx have been proposed in literature. However, these approaches assume feature-complete data, which is often not the case in clinical data. To account for missing data, incomplete data samples are either removed or imputed, which could lead to data bias and may negatively affect classification performance. As a solution, we propose an end-to-end learning of imputation and disease prediction of incomplete medical datasets via Multi-graph Geometric Matrix Completion (MGMC). MGMC uses multiple recurrent graph convolutional networks, where each graph represents an independent population model based on a key clinical meta-feature like age, sex, or cognitive function. Graph signal aggregation from local patient neighborhoods, combined with multi-graph signal fusion via self-attention, has a regularizing effect on both matrix reconstruction and classification performance. Our proposed approach is able to impute class relevant features as well as perform accurate and robust classification on two publicly available medical datasets. We empirically show the superiority of our proposed approach in terms of classification and imputation performance when compared with state-of-the-art approaches. MGMC enables disease prediction in multimodal and incomplete medical datasets. These findings could serve as baseline for future CADx approaches which utilize incomplete datasets.
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http://dx.doi.org/10.1016/j.artmed.2021.102097DOI Listing
July 2021

Comparison of electronic versus conventional assessment methods in ophthalmology residents; a learner assessment scholarship study.

BMC Med Educ 2021 Jun 13;21(1):342. Epub 2021 Jun 13.

Conestoga Eye, Lancaster, PA, USA.

Background: Assessment is a necessary part of training postgraduate medical residents. The implementation of methods located at the "shows how" level of Miller's pyramid is believed to be more effective than previous conventional tools. In this study, we quantitatively compared electronic and conventional methods in assessing ophthalmology residents.

Methods: In this retrospective study, eight different conventional methods of assessment including residents' attendance, logbook, scholarship and research skills, journal club, outpatient department participation, Multiple Choice Question (MCQ), Objective Structured Clinical Examination (OSCE), and professionalism/360-degree (as one complex) were used to assess 24 ophthalmology residents of all grades. Electronic media consisting of an online Patient Management Problem (e-PMP), and modified electronic OSCE (me-OSCE) tests performed 3 weeks later were also evaluated for each of the 24 residents. Quantitative analysis was then performed comparing the conventional and electronic assessment tools, statistically assessing the correlation between the two approaches.

Results: Twenty-four ophthalmology residents of different grades were included in this study. In the electronic assessment, average e-PMP scores (48.01 ± 12.40) were much lower than me-OSCE (65.34 ± 17.11). The total average electronic score was 56.67 ± 11.28, while the total average conventional score was 80.74 ± 5.99. Female and male residents' average scores in the electronic and conventional method were (59.15 ± 12.32 versus 83.01 ± 4.95) and (55.19 ± 10.77 versus 79.38 ± 6.29), respectively. The correlation between modified electronic OSCE and all conventional methods was not statistically significant (P-value >0.05). Correlation between e-PMP and six conventional methods, consisting of professionalism/360-degree assessment tool, logbook, research skills, Multiple Choice Questions, Outpatient department participation, and Journal club active participation was statistically significant (P-value < 0.05). The overall correlation between conventional and electronic methods was significant (P-value = 0.017).

Conclusion: In this study, we conclude that electronic PMP can be used alongside all conventional tools, and overall, e-assessment methods could replace currently used conventional methods. Combined electronic PMP and me-OSCE can be used as a replacement for currently used gold-standard assessment methods, including 360-degree assessment.
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http://dx.doi.org/10.1186/s12909-021-02759-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8201812PMC
June 2021

Simulation and surface topology of activity of pyrazoloquinoline derivatives as corrosion inhibitor on the copper surfaces.

Sci Rep 2021 Jun 9;11(1):12223. Epub 2021 Jun 9.

Department of Chemistry, Kerman Branch, Islamic Azad University, Kerman, Iran.

In the present study, corrosion inhibition performances of some pyrazolo [3,4-b] quinoline-3,5-dione derivatives against the corrosion of copper metal were investigated using B3LYP/6-311++g(d,p) calculation level in aqueous media. Additionally, interaction energies were calculated for all the pyrazoloquinoline derivatives compounds. In the calculations it is observed that studied molecules adsorb on metal surface with the help of electron donor heteroatoms in their molecular structures. Chemical thermodynamic parameters regarding the interaction between inhibitor molecule and copper surface were estimated and discussed. Density of the electron profile analysis and chemical electrostatic potential of nuclear charges in the molecule were applied to consider the nature of a number of probable interactions between Cu metal surface and inhibitors in terms of bond critical point (BCP). Calculated quantum chemical parameters showed that the pyrazoloquinoline derivatives including the OH and NO exhibit high inhibition performance.
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http://dx.doi.org/10.1038/s41598-021-91159-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8190070PMC
June 2021

Oncogenic mutations in PI3K/AKT/mTOR pathway effectors associate with worse prognosis in BRAF-driven papillary thyroid cancer patients.

Clin Cancer Res 2021 Jun 4. Epub 2021 Jun 4.

Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, Harvard Medical School

Purpose: The extent to which routine genomic sequencing can identify relevant secondary genomic alterations among -mutant papillary thyroid carcinoma (PTC) is unknown. Such markers would prove highly valuable for prognostic purposes.

Experimental Design: We reviewed clinicopathological data of 225 patients with -mutant PTC and integrated them with genomic data derived from targeted next generation sequencing on tumor specimens. We defined patient subgroups based on secondary oncogenic events (separate from ) and compared their clinical features and outcomes with those without additional oncogenic alterations.

Results: Additional oncogenic alterations were identified in 16% of tumors. Patients in the "+additional mutations" group were more likely to be at high ATA risk of recurrence (48.6 17.6%; = 0.0009), had larger baseline tumor (2.7 1.9 cm; = 0.0005) and more advanced stage at presentation (14.3% 1.1% stage 4; <0.0001). Importantly, over a 65-month follow up, disease-specific mortality was increased when additional mutations were identified (13.8% 1.4% in the only group; = 0.005). Separately, we identified a subcluster of patients harboring oncogenic mutations in key effectors of the PI3K/AKT/mTOR pathway, which were independently associated with disease-specific mortality [odds ratio (95% confidence interval) = 47.9 (3.5-1246.5); = 0.0043].

Conclusions: Identification of additional PIK3/AKT/mTOR alterations in patients with -mutant PTC provides important and actionable prognostic risk stratification. These data support genomic profiling of PTC tumors to inform prognosis and clinical strategy.
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http://dx.doi.org/10.1158/1078-0432.CCR-21-0874DOI Listing
June 2021

How Multilayered Feathers Enhance Underwater Superhydrophobicity.

ACS Appl Mater Interfaces 2021 Jun 2;13(23):27567-27574. Epub 2021 Jun 2.

Department of Mechanical Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States.

Inspired by ducks, we demonstrate that air pockets within stacked layers of porous superhydrophobic feathers can withstand up to five times more water pressure compared to a single feather. In addition to natural duck feathers, this "layer effect" was replicated with synthetic feathers created by laser cutting micrometric slots into aluminum foil and imparting a superhydrophobic nanostructure. It was revealed that adding layers promotes an increasingly redundant pathway for water impalement, which serves to pressurize the enclosed air pockets. This was validated by creating a probabilistic pore impalement model and also by filling the feathers with an incompressible oil, rather than air, to suppress the layer effect. In addition to revealing a utility of natural duck feathers, our findings suggest that multilayered engineered surfaces can maintain air pockets at high pressures, useful for reducing the drag and fouling of marine structures or enhancing desalination membranes.
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http://dx.doi.org/10.1021/acsami.1c04480DOI Listing
June 2021