Nicole Zahradka

Dr. Nicole Zahradka

Johns Hopkins University

Research Focus & Metrics

Academic Career Length

1Year (2026-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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15 September 2020 in Sensors
Verified
Journal Article
Open access
PDF file
NZNicole Zahradka
Nicole Zahradka
Khushboo VermaKhushboo Verma
Khushboo Verma
Ahad BehboodiAhad Behboodi
Ahad Behboodi
Barry BodtBarry Bodt
Barry Bodt
HWHenry Wright
Henry Wright
SLSamuel Lee
Samuel Lee
Video- and sensor-based gait analysis systems are rapidly emerging for use in ‘real world’ scenarios outside of typical instrumented motion analysis laboratories. Unlike laboratory systems, such systems do not use kinetic data from force plates, rather, gait events such as initial contact (IC) and terminal contact (TC) are estimated from video and sensor signals. There are, however, detection errors inherent in kinematic gait event detection methods (GEDM) and comparative study between classic laboratory and video/sensor-based systems is warranted. For this study, three kinematic methods: coordinate based treadmill algorithm (CBTA), shank angular velocity (SK), and foot velocity algorithm (FVA) were compared to ‘gold standard’ force plate methods (GS) for determining IC and TC in adults (n = 6), typically developing children (n = 5) and children with cerebral palsy (n = 6). The root mean square error (RMSE) values for CBTA, SK, and FVA were 27.22, 47.33, and 78.41 ms, respectively. On average, GED was detected earlier in CBTA and SK (CBTA: −9.54 ± 0.66 ms, SK: −33.41 ± 0.86 ms) and delayed in FVA (21.00 ± 1.96 ms). The statistical model demonstrated insensitivity to variations in group, side, and individuals. Out of three kinematic GEDMs, SK GEDM can best be used for sensor-based gait event detection.

1 June 2019 in Sensors
Verified
Journal Article
Open access
PDF file
Ahad BehboodiAhad Behboodi
Ahad Behboodi
NZNicole Zahradka
Nicole Zahradka
HWHenry Wright
Henry Wright
JAJames Alesi
James Alesi
SLSamuel Lee
Samuel Lee
A recently designed gait phase detection (GPD) system, with the ability to detect all seven phases of gait in healthy adults, was modified for GPD in children with cerebral palsy (CP). A shank-attached gyroscope sent angular velocity to a rule-based algorithm in LabVIEW to identify the distinct characteristics of the signal. Seven typically developing children (TD) and five children with CP were asked to walk on treadmill at their self-selected speed while using this system. Using only shank angular velocity, all seven phases of gait (Loading Response, Mid-Stance, Terminal Stance, Pre-Swing, Initial Swing, Mid-Swing and Terminal Swing) were reliably detected in real time. System performance was validated against two established GPD methods: (1) force-sensing resistors (GPD-FSR) (for typically developing children) and (2) motion capture (GPD-MoCap) (for both typically developing children and children with CP). The system detected over 99% of the phases identified by GPD-FSR and GPD-MoCap. Absolute values of average gait phase onset detection deviations relative to GPD-MoCap were less than 100 ms for both TD children and children with CP. The newly designed system, with minimized sensor setup and low processing burden, is cosmetic and economical, making it a viable solution for real-time stand-alone and portable applications such as triggering functional electrical stimulation (FES) in rehabilitation systems. This paper verifies the applicability of the GPD system to identify specific gait events for triggering FES to enhance gait in children with CP.

30 May 2019 in Sensors
Verified
Journal Article
Open access
PDF file
NZNicole Zahradka
Nicole Zahradka
Ahad BehboodiAhad Behboodi
Ahad Behboodi
HWHenry Wright
Henry Wright
Barry BodtBarry Bodt
Barry Bodt
SLSamuel Lee
Samuel Lee
Functional electrical stimulation systems are used as neuroprosthetic devices in rehabilitative interventions such as gait training. Stimulator triggers, implemented to control stimulation delivery, range from open- to closed-loop controllers. Finite-state controllers trigger stimulators when specific conditions are met and utilize preset sequences of stimulation. Wearable sensors provide the necessary input to differentiate gait phases during walking and trigger stimulation. However, gait phase detection is associated with inherent system delays. In this study, five stimulator triggers designed to compensate for gait phase detection delays were tested to determine which trigger most accurately delivered stimulation at the desired times of the gait cycle. Motion capture data were collected on seven typically-developing children while walking on an instrumented treadmill. Participants wore one inertial measurement unit on each ankle and gyroscope data were streamed into the gait phase detection algorithm. Five triggers, based on gait phase detection, were used to simulate stimulation to five muscle groups, bilaterally. For each condition, stimulation signals were collected in the motion capture software via analog channels and compared to the desired timing determined by kinematic and kinetic data. Results illustrate that gait phase detection is a viable finite-state control, and appropriate system delay compensations, on average, reduce stimulation delivery delays by 6.7% of the gait cycle.

1 November 2025 in JCO Oncology Practice
Verified
Journal Article
Closed access
NMNavneet S. Majhail
Navneet S. Majhail
TCTonya Cox
Tonya Cox
SLStephanie Larson
Stephanie Larson
MBMinoo Battiwalla
Minoo Battiwalla
ARAravind Ramakrishnan
Aravind Ramakrishnan
JPJeremy Pantin
Jeremy Pantin
Chimeric antigen receptor T-cell (CAR-T) therapies are standard of care for the treatment of several hematologic malignancies. Although patients receiving CAR-T therapies are frequently hospitalized given risks of cytokine release syndrome (CRS) and immune effector cell–associated neurotoxicity syndrome (ICANS), there is increasing interest and evidence for the safety of their outpatient administration. We review various models of care and provide operational considerations for centers that are interested in developing outpatient CAR-T programs, with a particular emphasis on using remote patient monitoring (RPM) to facilitate outpatient care. Safe and high-quality outpatient care requires involvement of a multidisciplinary team with clinical pathways for rapid triage and evaluation for CRS and ICANS and their management and, if necessary, timely transition of patients to a higher level of acute care. RPM can facilitate scaling an outpatient program in a cost-effective manner, especially across multiple sites of care, and can reduce the time patients spend in an acute care setting. Overall minimizing hospital-based care and an outpatient approach can alleviate capacity challenges treatment centers have faced that have partly impacted access to CAR-T therapies and have the potential to positively impact patient and caregiver experience and quality of life.

25 January 2023 in Journal of Medical Internet Research
Verified
Journal Article
Open access
RWRobert J Walter
Robert J Walter
SSStephen Schwab
Stephen Schwab
MWMatt Wilkes
Matt Wilkes
DYDaniel Yourk
Daniel Yourk
NZNicole Zahradka
Nicole Zahradka
MMMichael Morris
Michael Morris
Background: Virtual care (VC) and remote patient monitoring programs were deployed widely during the COVID-19 pandemic. Deployments were heterogeneous and evolved as the pandemic progressed, complicating subsequent attempts to quantify their impact. The unique arrangement of the US Military Health System (MHS) enabled direct comparison between facilities that did and did not implement a standardized VC program. The VC program enrolled patients symptomatic for COVID-19 or at risk for severe disease. Patients’ vital signs were continuously monitored at home with a wearable device (Current Health). A central team monitored vital signs and conducted daily or twice-daily reviews (the nurse-to-patient ratio was 1:30). Objective: Our goal was to describe the operational model of a VC program for COVID-19, evaluate its financial impact, and detail its clinical outcomes. Methods: This was a retrospective difference-in-differences (DiD) evaluation that compared 8 military treatment facilities (MTFs) with and 39 MTFs without a VC program. Tricare Prime beneficiaries diagnosed with COVID-19 (Medicare Severity Diagnosis Related Group 177 or International Classification of Diseases–10 codes U07.1/07.2) who were eligible for care within the MHS and aged 21 years and or older between December 2020 and December 2021 were included. Primary outcomes were length of stay and associated cost savings; secondary outcomes were escalation to physical care from home, 30-day readmissions after VC discharge, adherence to the wearable, and alarms per patient-day. Results: A total of 1838 patients with COVID-19 were admitted to an MTF with a VC program of 3988 admitted to the MHS. Of these patients, 237 (13%) were enrolled in the VC program. The DiD analysis indicated that centers with the program had a 12% lower length of stay averaged across all COVID-19 patients, saving US $2047 per patient. The total cost of equipping, establishing, and staffing the VC program was estimated at US $3816 per day. Total net savings were estimated at US $2.3 million in the first year of the program across the MHS. The wearables were activated by 231 patients (97.5%) and were monitored through the Current Health platform for a total of 3474 (median 7.9, range 3.2-16.5) days. Wearable adherence was 85% (IQR 63%-94%). Patients triggered a median of 1.6 (IQR 0.7-5.2) vital sign alarms per patient per day; 203 (85.7%) were monitored at home and then directly discharged from VC; 27 (11.4%) were escalated to a physical hospital bed as part of their initial admission. There were no increases in 30-day readmissions or emergency department visits. Conclusions: Monitored patients were adherent to the wearable device and triggered a manageable number of alarms/day for the monitoring–team-to-patient ratio. Despite only enrolling 13% of COVID-19 patients at centers where it was available, the program offered substantial savings averaged across all patients in those centers without adversely affecting clinical outcomes.

29 June 2021 in Sensors
Verified
Journal Article
Open access
PDF file
NZNicole Zahradka
Nicole Zahradka
Ahad BehboodiAhad Behboodi
Ahad Behboodi
Ashwini SansareAshwini Sansare
Ashwini Sansare
SLSamuel Lee
Samuel Lee
Functional electrical stimulation (FES) walking interventions have demonstrated improvements to gait parameters; however, studies were often confined to stimulation of one or two muscle groups. Increased options such as number of muscle groups targeted, timing of stimulation delivery, and level of stimulation are needed to address subject-specific gait deviations. We aimed to demonstrate the feasibility of using a FES system with increased stimulation options during walking in children with cerebral palsy (CP). Three physical therapists designed individualized stimulation programs for six children with CP to target participant-specific gait deviations. Stimulation settings (pulse duration and current) were tuned to each participant. Participants donned our custom FES system that utilized gait phase detection to control stimulation to lower extremity muscle groups and walked on a treadmill at a self-selected speed. Motion capture data were collected during walking with and without the individualized stimulation program. Eight gait metrics and associated timing were compared between walking conditions. The prescribed participant-specific stimulation programs induced significant change towards typical gait in at least one metric for each participant with one iteration of FES-walking. FES systems with increased stimulation options have the potential to allow the physical therapist to better target the individual’s gait deviations than a one size fits all device.