Functional imaging of neural circuits in the spine using contrast-free super-resolution ultrasound

The National Institute of Neurological Disorders and Stroke awarded the University of Illinois $599,169 on September 1, 2026, under the 21st Century Cures Act — Brain Research through Advancing Innovative Neurotechnologies (BRAIN) Initiative, CFDA 93.372, to develop and validate contrast-free super-resolution ultrasound imaging techniques for functional imaging of neural circuits in the spinal cord.

The research demonstrates phase subtraction imaging (PSI) and null subtraction imaging (NSI) as novel tools for functional ultrasound imaging of spinal cord blood flow without contrast agents, achieving spatial resolution better than ten micrometers. The work targets improved understanding and treatment of chronic pain by developing spatiotemporal biomarkers that correlate pain to specific nerve bundles in the spine, with application to optimizing spinal cord stimulation therapy for neuropathic pain conditions refractory to pharmacologic treatment.

Performance occurs in Urbana, Illinois through August 31, 2029. The BRAIN Initiative aims to accelerate development and application of innovative neurotechnologies enabling researchers to produce a dynamic picture of brain and neural circuit function across time and space, with the goal of advancing prevention and treatment of brain disorders.

Abstract

Chronic pain is pain lasting more than three months that affects the quality of life of 51 million US adults with a $560-635 billion burden due to treatment and loss in productivity [NAT11]. Further, 17 million adults with chronic pain have reported high impact chronic pain that limits the activities of daily living [CDC23]. The subjective nature of chronic pain makes the degree and quality difficult to quantify. Further, there are limited interventions available for medically refractory chronic pain. New technologies to better understand and treat chronic pain are necessary to alleviate the economic and emotional burden of chronic pain in the USA. The spinal cord is an emerging target in the management of chronic pain. Chronic pain is often associated with spinal cord issues [DIB17] and in many cases pharmacologic treatment is ineffective [CAV19]. Spinal cord stimulation (SCS) is the most common neurostimulation therapy to treat neuropathic pain conditions when pharmacologic approaches fail [LEM15]. SCS has a spatiotemporal component in that different regions of the spinal cord, i.e., neural circuits, are associated with different outcomes. Therefore, for optimal application and targeting of SCS in pain management, IT is critical to develop spatiotemporal BIO-markers that correlate pain to specific nerve bundles in the spine. We recently demonstrated the ability to create super-resolved ultrasound blood flow imaging without contrast agents (label free) and with spatial resolution better than 10 ΜM (Λ/10). This technique is called phase subtraction imaging (PSI) and is a follow-on technique to null subtraction imaging (NSI), which provided super-resolved power doppler images [KOU24, KOU25]. The goal of the proposed research is to demonstrate and validate PSI and NSI as novel tools for functional ultrasound (FUS) imaging of the spinal cord with high spatiotemporal resolution sufficient to image neural circuits. The scientific premise is that super resolved FUS using PSI and NSI can provide critical and specific information about spinal cord function in vivo, with sufficient spatial resolution to identify neural circuits in the spine without the need for external contrast agents. To complete these goals we propose two specific aims. The first aims is to quantify the performance of PSI and NSI with and without contrast agents and compare to state-of-the-art super-resolution ultrasound techniques. In this aim we will conduct experiments in the spines of rats in vivo. We will compare our novel PSI/NSI techniques with conventional methods, such as DAS, and with ultrasound localization microscopy (ULM). We will compare the performance of PSI/NSI for spinal blood flow imaging with and without contrast agents present and versus various transmit and receive conditions. The second aim is to correlate super-resolution spatiotemporal changes in blood flow in the spinal cord via FUS to spinal cord nerve cells activated by external stimulus. In this aim, we will use different stimuli on different limbs to assess the localization capabilities of our super-resolution imaging technologies and compare with C-FOS staining to correlate image findings with neural activity. We will further correlate the degree of stimulation with the degree of blood flow changes using imaging and increased uptake of C-FOS.