Ates Fettahoglu

All Publications

• A Nonlinear Single Channel Gradient Insert for Prostate Diffusion Imaging. Magnetic resonance in medicine Elsaid, N. M., Zhang, H. Z., Fettahoglu, A., Sun, C., De Simone, A., Nixon, T., Dewdney, A., Peters, D. C., Weinreb, J., Constable, T., Galiana, G. 2025

  Abstract

  This paper reports on the technical performance of a nonlinear "inside-out" gradient and its feasibility and safety for diffusion encoding in humans. The tested hardware is a solenoidal coil with a 10 cm diameter, positioned at the isocenter of the magnet bore, designed to generate strong gradients within the surrounding volume.Various methods were used to characterize the spatial, temporal, mechanical, and acoustic properties of the gradient coil. ADC mapping studies show the feasibility of diffusion-weighted imaging and ADC mapping in phantoms and humans.The hardware was found to generate high gradient strengths (> 200 mT/m) for expected prostate regions whilst heating, noise, and eddy currents remained within acceptable limits for human scanning. Despite its unconventional geometry and compact form factor, standard calibration methods were effective, enabling accurate ADC mapping in both phantoms and human subjects. No peripheral nerve stimulation (PNS) was reported, even at maximum slew rates and gradient amplitudes.Inside-out nonlinear gradients can be calibrated with conventional techniques, and the hardware can provide a more convenient approach to strong diffusion weighting of targeted organs.

  View details for DOI 10.1002/mrm.70125

  View details for PubMedID 41078149

• Arterial Spin-Labeling MRI Identifies Abnormal Perfusion Metric at the Gray Matter/CSF Interface in Cerebral Small Vessel Disease. AJNR. American journal of neuroradiology Mahammedi, A., Fettahoglu, A., Heit, J. J., Wardlaw, J. M., Zaharchuk, G. 2025

  Abstract

  Cerebral small vessel disease (SVD) is a common cause of stroke and cognitive decline. SVD is characterized by white matter hyperintensities (WMH) and dilated perivascular spaces (PVS). While WMH can be associated with reduced CBF and glymphatic clearance, current clinical and radiologic assessments of these associations remain controversial and mostly qualitative. We aim to identify if arterial spin-labeling (ASL)-based CBF differences, particularly in the cortical surface at the GM/CSF interface, correlate with SVD severity.We performed a retrospective cohort study of healthy controls with normal cognition who underwent a brain MRI as part of our university's Alzheimer Disease Research Center (ADRC) and an 15O-water PET study database. Our inclusion criteria included patients aged >50 years with no structural brain abnormalities besides SVD with ASL perfusion images. WMH grading was performed by using the Fazekas scale, WMH score, PVS grade, and manually segmented WMH volume. We identified patients with moderate-to-severe SVD and then selected age-matched samples of patients with minimal or no SVD. CBF of the whole brain (WB), GM, WM, and along the GM/CSF interface were calculated. Several perfusion metrics (WB, GM, and WM) as well as a novel perfusion metric, normalized GM/CSF interface (nGCI) perfusion metric, which indirectly reflects the relative ASL signal near the GM-CSF boundary, were evaluated by using receiver operating characteristic and correlation analyses.Thirty-two patients met the inclusion criteria (n=11 moderate-to-severe SVD, mean age 72 ± 10 years, 6 women; n = 21 none-to-minimal SVD, mean age 70 ± 10 years, 12 women). Of the measured perfusion markers, nGCI had the strongest negative correlation with Fazekas score, total WMH volume, PVS grade, and average total SVD score (r = -0.68, -0.67, -0.54, -0.54, respectively; P < .001) as well as the highest area under the receiver operating characteristics curve (0.95, 95% CI: 0.87-1.0) as a predictor of WMH severity.nGCI, a novel perfusion metric that may capture features of perfusion at the GM-CSF boundary, was strongly correlated with WMH and PVS severity. Further, longitudinal studies are required to determine the potential role of nGCI as a predictive marker of SVD progression.

  View details for DOI 10.3174/ajnr.A8682

  View details for PubMedID 40506229

• Deep Learning Applications in Imaging of Acute Ischemic Stroke: A Systematic Review and Narrative Summary. Radiology Jiang, B., Pham, N., van Staalduinen, E. K., Liu, Y., Nazari-Farsani, S., Sanaat, A., van Voorst, H., Fettahoglu, A., Kim, D., Ouyang, J., Kumar, A., Srivatsan, A., Hussein, R., Lansberg, M. G., Boada, F., Zaharchuk, G. 2025; 315 (1): e240775

  Abstract

  Background Acute ischemic stroke (AIS) is a major cause of morbidity and mortality, requiring swift and precise clinical decisions based on neuroimaging. Recent advances in deep learning-based computer vision and language artificial intelligence (AI) models have demonstrated transformative performance for several stroke-related applications. Purpose To evaluate deep learning applications for imaging in AIS in adult patients, providing a comprehensive overview of the current state of the technology and identifying opportunities for advancement. Materials and Methods A systematic literature review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A comprehensive search of four databases from January 2016 to January 2024 was performed, targeting deep learning applications for imaging of AIS, including automated detection of large vessel occlusion and measurement of Alberta Stroke Program Early CT Score. Articles were selected based on predefined inclusion and exclusion criteria, focusing on convolutional neural networks and transformers. The top-represented areas were addressed, and the relevant information was extracted and summarized. Results Of 380 studies included, 171 (45.0%) focused on stroke lesion segmentation, 129 (33.9%) on classification and triage, 31 (8.2%) on outcome prediction, 15 (3.9%) on generative AI and large language models, and 11 (2.9%) on rapid or low-dose imaging specific to stroke applications. Detailed data extraction was performed for 68 studies. Public AIS datasets are also highlighted, for researchers developing AI models for stroke imaging. Conclusion Deep learning applications have permeated AIS imaging, particularly for stroke lesion segmentation. However, challenges remain, including the need for standardized protocols and test sets, larger public datasets, and performance validation in real-world settings. © RSNA, 2025 Supplemental material is available for this article.

  View details for DOI 10.1148/radiol.240775

  View details for PubMedID 40197098

• Early-Frame [18F]Florbetaben PET/MRI for Cerebral Blood Flow Quantification in Patients with Cognitive Impairment: Comparison to an [15O]Water Gold Standard. Journal of nuclear medicine : official publication, Society of Nuclear Medicine Fettahoglu, A., Zhao, M., Khalighi, M., Vossler, H., Jovin, M., Davidzon, G., Zeineh, M., Boada, F., Mormino, E., Henderson, V. W., Moseley, M., Chen, K. T., Zaharchuk, G. 2023

  Abstract

  Cerebral blood flow (CBF) may be estimated from early-frame PET imaging of lipophilic tracers, such as amyloid agents, enabling measurement of this important biomarker in participants with dementia and memory decline. Although previous methods could map relative CBF, quantitative measurement in absolute units (mL/100 g/min) remained challenging and has not been evaluated against the gold standard method of [15O]water PET. The purpose of this study was to develop and validate a minimally invasive quantitative CBF imaging method combining early [18F]florbetaben (eFBB) with phase-contrast MRI using simultaneous PET/MRI. Methods: Twenty participants (11 men and 9 women; 8 cognitively normal, 9 with mild cognitive impairment, and 3 with dementia; 10 β-amyloid negative and 10 β-amyloid positive; 69 ± 9 y old) underwent [15O]water PET, phase-contract MRI, and eFBB imaging in a single session on a 3-T PET/MRI scanner. Quantitative CBF images were created from the first 2 min of brain activity after [18F]florbetaben injection combined with phase-contrast MRI measurement of total brain blood flow. These maps were compared with [15O]water CBF using concordance correlation (CC) and Bland-Altman statistics for gray matter, white matter, and individual regions derived from the automated anatomic labeling (AAL) atlas. Results: The 2 methods showed similar results in gray matter ([15O]water, 55.2 ± 14.7 mL/100 g/min; eFBB, 55.9 ± 14.2 mL/100 g/min; difference, 0.7 ± 2.4 mL/100 g/min; P = 0.2) and white matter ([15O]water, 21.4 ± 5.6 mL/100 g/min; eFBB, 21.2 ± 5.3 mL/100 g/min; difference, -0.2 ± 1.0 mL/100 g/min; P = 0.4). The intrasubject CC for AAL-derived regions was high (0.91 ± 0.04). Intersubject CC in different AAL-derived regions was similarly high, ranging from 0.86 for midfrontal regions to 0.98 for temporal regions. There were no significant differences in performance between the methods in the amyloid-positive and amyloid-negative groups as well as participants with different cognitive statuses. Conclusion: We conclude that eFBB PET/MRI can provide robust CBF measurements, highlighting the capability of simultaneous PET/MRI to provide measurements of both CBF and amyloid burden in a single imaging session in participants with memory disorders.

  View details for DOI 10.2967/jnumed.123.266273

  View details for PubMedID 38071587

• Short- and Long-Term MRI Assessed Hemodynamic Changes in Pediatric Moyamoya Patients After Revascularization. Journal of magnetic resonance imaging : JMRI Zhao, M. Y., Tong, E., Duarte Armindo, R., Fettahoglu, A., Choi, J., Bagley, J., Yeom, K. W., Moseley, M., Steinberg, G. K., Zaharchuk, G. 2023

  Abstract

  Cerebrovascular reserve (CVR) reflects the capacity of cerebral blood flow (CBF) to change following a vasodilation challenge. Decreased CVR is associated with a higher stroke risk in patients with cerebrovascular diseases. While revascularization can improve CVR and reduce this risk in adult patients with vasculopathy such as those with Moyamoya disease, its impact on hemodynamics in pediatric patients remains to be elucidated. Arterial spin labeling (ASL) is a quantitative MRI technique that can measure CBF, CVR, and arterial transit time (ATT) non-invasively.To investigate the short- and long-term changes in hemodynamics after bypass surgeries in patients with Moyamoya disease.Longitudinal.Forty-six patients (11 months-18 years, 28 females) with Moyamoya disease.3-T, single- and multi-delay ASL, T1-weighted, T2-FLAIR, 3D MRA.Imaging was performed 2 weeks before and 1 week and 6 months after surgical intervention. Acetazolamide was employed to induce vasodilation during the imaging procedure. CBF and ATT were measured by fitting the ASL data to the general kinetic model. CVR was computed as the percentage change in CBF. The mean CBF, ATT, and CVR values were measured in the regions affected by vasculopathy.Pre- and post-revascularization CVR, CBF, and ATT were compared for different regions of the brain. P-values <0.05 were considered statistically significant.ASL-derived CBF in flow territories affected by vasculopathy significantly increased after bypass by 41 ± 31% within a week. At 6 months, CBF significantly increased by 51 ± 34%, CVR increased by 68 ± 33%, and ATT was significantly reduced by 6.6 ± 2.9%.There may be short- and long-term improvement in the hemodynamic parameters of pediatric Moyamoya patients after bypass surgery.4 TECHNICAL EFFICACY: Stage 2.

  View details for DOI 10.1002/jmri.28902

  View details for PubMedID 37515518

• Multimodal Perfusion PET/MR Imaging with [18F]-Labeled FDG, FBB and PI-2620 within the AT(N) Framework Fettahoglu, A., Zhao, M. Y., Mormino, E., Zeineh, M., Moseley, M., Zaharchuk, G. 2023

  View details for DOI 10.1007/s10334-023-01108-9

• Determination of PET Tracer Arrival Time (TAT) in the Brain Using Early-Phase Uptake Dynamics: Conmparison to Simultaneous ASL Arterial Transit Time (ATT) Fettahoglu, A., Khalighi, M., Zhao, M. Y., Moseley, M., Zaharchuk, G. ISMRM Workshop on PET/MRI. 2023
• Eddy-current characterization and pre-emphasis on a compact inside-out nonlinear gradient ISMRM Fettahoglu, A., Zhang, H., Elsaid, N., Galiana, G. ISMRM. 2023
• Validation of early-frame [18F]FDG PET for CBF quantification: Comparison to simultaneous eASL measurements in memory patients Fettahoglu, A., Zhao, M. Y., Chen, K., Khalighi, M., Zeineh, M., Mormino, E., Moseley, M., Zaharchuk, G. AAIC. 2023
• Dual-phase PET for Cerebral Blood Flow Quantification & Amyloid Imaging Using [18F]Florbetaben: Validation Against a Gold Standard [15O]Water ISMRM Workshop on PET/MRI Fettahoglu, A., Zhao, M. Y., Khalighi, M., Mormino, E., Chen, K., Moseley, M., Zaharchuk, G. Proc. ISMRM Workshop on PET/MRI 2023. 2023
• Analysis of gas breakdown and electrostatic simulation characteristics of a Spherical Inertial Electrostatic Confinement Fusion Chamber (SIEC-K) Journal of Nuclear Sciences Fettahoglu, A. 2021

  View details for DOI 10.1501/nuclear.2023.53