Aiping Yao


Last Name

Yao

First Name

Aiping

ORCID

0000-0002-3859-2684

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2016 - 201972020 - 20213
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Publications 1 - 10 of 10
  • Computable Anatomical Phantoms for MRI Safety Evaluation of Patients with Implants
    Item type: Other Conference Item
    Yao, Aiping; Zastrow, Earl; Cabot, Eugenia; et al. (2016)
  • Radiofrequency-induced heating of broken and abandoned implant leads during magnetic resonance examinations
    Item type: Journal Article
    Yao, Aiping; Goren, Tolga; Samaras, Theodoros; et al. (2021)
    Magnetic Resonance in Medicine
    Purpose The risks of RF-induced heating of active implantable medical device (AIMD) leads during MR examinations must be well understood and realistically assessed. In this study, we evaluate the potential additional risks of broken and abandoned (cut) leads. Methods First, we defined a generic AIMD with a metallic implantable pulse generator (IPG) and a 100-cm long lead containing 1 or 2 wires. Next, we numerically estimated the deposited in vitro lead-tip power for an intact lead, as well as with wire breaks placed at 10 cm intervals. We studied the effect of the break size (wire gap width), as well as the presence of an intact wire parallel to the broken wire, and experimentally validated the numeric results for the configurations with maximum deposited in vitro lead-tip power. Finally, we performed a Tier 3 assessment of the deposited in vivo lead-tip power for the intact and broken lead in 4 high resolution virtual population anatomic models for over 54,000 MR examination scenarios. Results The enhancement of the deposited lead-tip power for the broken leads, compared to the intact lead, reached 30-fold in isoelectric exposure, and 16-fold in realistic clinical exposures. The presence of a nearby intact wire, or even a nearby broken wire, reduced this enhancement factor to <7-fold over the intact lead. Conclusion Broken and abandoned leads can pose increased risk of RF-induced lead-tip heating to patients undergoing MR examinations. The potential enhancement of deposited in vivo lead-tip power depends on location and type of the wire break, lead design, and clinical routing of the lead, and should be carefully considered when performing risk assessment for MR examinations and MR conditional labeling.
  • Efficient and Reliable Assessment of the Maximum Local Tissue Temperature Increase at the Electrodes of Medical Implants under MRI Exposure
    Item type: Journal Article
    Yao, Aiping; Zastrow, Earl; Neufeld, Esra; et al. (2019)
    Bioelectromagnetics
  • Test field diversification method for the safety assessment of RF-induced heating of medical implants during MRI at 64 MHz
    Item type: Other Conference Item
    Lucano, Elena; Yao, Aiping; Zastrow, Earl; et al. (2016)
    Joint Meeting of the Bioelectromagnetics Society and the European BioElectromagnetics Association (BioEM2016) : Abstract Collection – Complete Collection
  • Experimental and numerical optimization modelling to reduce radiofrequency-induced risks of magnetic resonance examinations on leaded implants
    Item type: Journal Article
    Córcoles, Juan; Yao, Aiping; Kuster, Niels (2021)
    Applied Mathematical Modelling
    Convex formulations can be used to reduce the local specific absorption rate enhancement by active medical implants of radiofrequency fields in magnetic resonance examinations while minimizing the loss of image quality. This paper demonstrates that such an optimization methodology, previously presented for strictly computational models, can be extended to a hybrid scheme using experimentally determined implant models and pre-computed fields, which can enable quasi real-time exposure optimization. The methodology determines the optimum radiofrequency field shimming condition by considering both the reduction of specific absorption rate enhancement at the tip of the implant lead, created by the interaction of the radiofrequency fields tangential to the implant trajectory with the characteristic response of the implant, and the preservation of magnetic field homogeneity, which correlates to image quality. The inputs to this workflow are those required for each implant by standard ISO 10974 evaluation, namely the validated piece-wise transfer function of the implant, the clinical routing within the patient, and the pre-computed numerical estimation of patient exposure without the implant. Optimized incident field conditions were computed to meet a range of numerical targets for specific absorption rate reduction, stepping down percentagewise from the maximum field homogeneity to the minimum exposure enhancement, for a generic implant with a flexible wire in a standard benchtop radiofrequency coil and phantom. Measurements of the corresponding specific absorption rate enhancements validated the predictions from the optimization approach within the combined confidence interval.
  • Integration of big-data analytics in safety assessment of patients with medical implants during MRI exposure
    Item type: Other Conference Item
    Yao, Aiping; Zastrow, Earl; Crespo-Valero, Pedro; et al. (2018)
    BioEM 2018 Abstract Collection
  • Anatomical Model Uncertainty for RF Safety Evaluation of Metallic Implants Under MRI Exposure
    Item type: Journal Article
    Yao, Aiping; Zastrow, Earl; Cabot, Eugenia; et al. (2019)
    Bioelectromagnetics
  • Induced radiofrequency fields in patients undergoing MR examinations: insights for risk assessment
    Item type: Journal Article
    Yao, Aiping; Murbach, Manuel; Goren, Tolga; et al. (2021)
    Physics in Medicine and Biology
    Purpose. To characterize and quantify the induced radiofrequency (RF) electric (E)-fields and B (1+rms) fields in patients undergoing magnetic resonance (MR) examinations; to provide guidance on aspects of RF heating risks for patients with and without implants; and to discuss some strengths and limitations of safety assessments in current ISO, IEC, and ASTM standards to determine the RF heating risks for patients with and without implants. Methods. Induced E-fields and B (1+rms) fields during 1.5 T and 3 T MR examinations were numerically estimated for high-resolution patient models of the Virtual Population exposed to ten two-port birdcage RF coils from head to feet imaging landmarks over the full polarization space, as well as in surrogate ASTM phantoms. Results. Worst-case B (1+rms) exposure greater than 3.5 mu T (1.5 T) and 2 mu T (3 T) must be considered for all MR examinations at the Normal Operating Mode limit. Representative induced E-field and specific absorption rate distributions under different clinical scenarios allow quick estimation of clinical factors of high and reduced exposure. B (1) shimming can cause +6 dB enhancements to E-fields along implant trajectories. The distribution and magnitude of induced E-fields in the ASTM phantom differ from clinical exposures and are not always conservative for typical implant locations. Conclusions. Field distributions in patient models are condensed, visualized for quick estimation of risks, and compared to those induced in the ASTM phantom. Induced E-fields in patient models can significantly exceed those in the surrogate ASTM phantom in some cases. In the recent 19( epsilon 2) revision of the ASTM F2182 standard, the major shortcomings of previous versions have been addressed by requiring that the relationship between ASTM test conditions and in vivo tangential E-fields be established, e.g. numerically. With this requirement, the principal methods defined in the ASTM standard for passive implants are reconciled with those of the ISO 10974 standard for active implantable medical devices.
  • Power to temperature conversion of AIMD under RF exposure
    Item type: Other Conference Item
    Yao, Aiping; Zastrow, Earl; Kuster, Niels (2018)
Publications 1 - 10 of 10