Ning Lu

Ning Lu

Publications

You can also find my articles on my Google Scholar profile.

Journal Articles

Improving real-time ultrasound spine imaging with a large-aperture array

Published in Science Advances, 2025

Abstract: Ultrasound offers a safe, low-cost alternative to computed tomography (CT) and magnetic resonance imaging for spinal diagnostics and intervention by enabling real-time imaging. However, the complex structure of the spine and acoustic shadowing from bones present challenges for ultrasonography. This study addresses these limitations using an 8.8-centimeter 384-element large-aperture array and full aperture-based imaging protocols. Volumetric scanning across multiple vertebrae was accomplished in 5 seconds using ultrafast, diverging wave acquisition. In seven healthy volunteers, the large-aperture array and diverging wave transmission improved resolution, contrast, and visualization of the spinal canal, venous plexuses, and facet joints compared with conventional probes. A comparison between the coregistered CT and ultrasound scan confirmed the imaging accuracy. A simulated lumbar puncture demonstrated needle tip visualization throughout the trajectory into the spinal canal. The results suggest that large-aperture arrays, coupled with diverging wave imaging sequences, are a valuable tool for spine imaging and image-guided intervention.

Recommended citation: N. Lu, et al. (2025). "Improving real-time ultrasound spine imaging with a large-aperture array." Sci. Adv.. 11,eadw2601.
Download Paper

Treatment envelope of transcranial histotripsy: challenges and strategies to maximize the treatment location profile

Published in Physics in Medicine & Biology, 2024

Abstract: A 750 kHz, 360-element ultrasound array was developed for transcranial histotripsy. This study evaluates its performance using experiments and simulations in human skulls. Results show that treatment efficacy depends on skull properties, with shallow targets facing greater challenges due to attenuation and pre-focal pressure hotspots. Strategies such as array design optimization and pose adjustment are proposed to enhance treatment. These findings guide the development of next-generation histotripsy arrays for clinical applications.

Recommended citation: N. Lu, et al. (2024). "Treatment envelope of transcranial histotripsy: challenges and strategies to maximize the treatment location profile." Physics in Medicine & Biology. 69(22).
Download Paper

Two-step aberration correction: application to transcranial histotripsy

Published in Physics in Medicine & Biology, 2022

Abstract: Phase aberration correction (AC) is crucial in transcranial histotripsy to correct for the skull-induced focal distortion. This paper enhances a 2-step AC method for clinical use, combining a CT-based analytical approach with a cavitation-based approach using acoustic cavitation emission (ACE). A 700 kHz, 360-element hemispherical transducer was used to generate histotripsy-induced cavitation and acquire ACE shockwaves. Testing on excised human skulls showed that the 2-step AC achieved 90 ± 7% peak focal pressure, reduced focal shift, and improved refocusing compared to individual AC methods. This real-time AC workflow enhances transcranial histotripsy for brain therapy.

Recommended citation: N. Lu, et al. (2022). "Two-step aberration correction: application to transcranial histotripsy." Physics in Medicine & Biology. 67(12).
Download Paper

Transcranial magnetic resonance-guided histotripsy for brain surgery: pre-clinical investigation

Published in Ultrasound in medicine & biology, 2022

Abstract: This study evaluates the in vivo feasibility of transcranial MR-guided histotripsy (tcMRgHt) for brain surgery. Using a 700 kHz, 128-element MR-compatible transducer inside a 3T MRI scanner, histotripsy was delivered to eight pigs through an excised human calvarium after craniotomy. MRI scans before and after treatment confirmed well-confined lesions without excessive edema or hemorrhage. Histology showed precise tissue ablation, correlating with MRI findings. These results demonstrate the first in vivo feasibility of tcMRgHt in the pig brain, supporting further investigation for clinical brain surgery applications.

Recommended citation: N. Lu, et al. (2022). "Transcranial magnetic resonance-guided histotripsy for brain surgery: pre-clinical investigation." Ultrasound in medicine & biology. 48(1).
Download Paper

Transcranial MR-Guided Histotripsy System

Published in IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (Front Cover Article), 2021

Abstract: This study develops the first transcranial MR-guided histotripsy (tcMRgHt) system for in vivo brain treatment. A 700 kHz, 128-element MR-compatible ultrasound transducer was designed, achieving peak negative pressures of 137 MPa in free field and 72 MPa through a skull with aberration correction. The system is MR-compatible and enabled electronic focal steering. In vivo testing in pigs demonstrated successful targeted brain tissue ablation without excessive bleeding or edema. The results confirm the feasibility of using tcMRgHt for transcranial treatment in a swine model.

Recommended citation: N. Lu, et al (2021). "Transcranial MR-Guided Histotripsy System." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control. 68(9).
Download Paper

Conference Papers

Accurate and Robust Eye Tracking with Ultrasound: A Computational Study

Published in 2023 IEEE International Ultrasonics Symposium (IUS), 2023

Abstract: This paper introduces an ultrasound simulation platform for generating realistic eye-tracking data, accounting for transducer design, sensor noise, occlusions, and headset slippage. Using a face/eye model with adjustable gaze and eyelid opening, synthesized data were input into a machine learning algorithm to estimate gaze and slippage. The system achieved a gaze RMSE of 0.085° without slippage and 0.756° with slippage. This end-to-end pipeline supports the optimization of wearable ultrasound devices and explores ultrasound as a complementary technology to camera-based eye tracking for AR/VR applications.

Recommended citation: N. Lu, et al. (2023). "Accurate and Robust Eye Tracking with Ultrasound: A Computational Study." 2023 IEEE International Ultrasonics Symposium (IUS) Proceedings.
Download Paper