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Ryan Halter

Associate Professor of Engineering

Program Area Lead: Biomedical Engineering
Adjunct Associate Professor of Surgery, Geisel School of Medicine
Technical Associate Director, Center for Precision Health and Artificial Intelligence (CPHAI)

Professor Halter discusses his research developing medical imaging devices and systems for monitoring, diagnosing, and treating disease.

Research Interests

Biomedical instrumentation; electrical impedance tomography and spectroscopy; medical imaging; tissue bioimpedance; cancer detection technologies; traumatic brain injury; medical robotics

Education

  • BSc Engineering Science and Mechanics, Pennsylvania State University 1999
  • MSc Engineering Mechanics, Pennsylvania State University 2001
  • PhD Biomedical Engineering, Dartmouth College 2006

Awards

  • Society of Critical Care Medicine’s Gold Snapshot Award (2021)
  • New Investigator Award in Prostate Cancer Research: DoD CDMRP (2009-2012)
  • Research Robotic Fellowship: Intuitive Surgical, Inc (2009-2011)

Professional Activities

  • Member, Institue of Electrical & Electronic Engineers (IEEE)
  • Member, International Society for Electrical Bio-Impedance (ISEBI)
  • Member, Dartmouth's Committee for the Protection of Human Subjects (CPHS)

Startups

RyTek Medical
Founder and CEO
SynchroHealth
Co-Founder

Research Projects

  • Electrical Impedance Imaging: Enabling deep space missions through medical imaging and diagnosis of the long-term physiological effects of space travel

    Electrical Impedance Imaging: Enabling deep space missions through medical imaging and diagnosis of the long-term physiological effects of space travel

    Goal: to provide an imaging tool to effectively monitor the long-term physiological effects

    of deep space and automate diagnosis, enabling crew members to be proactive in the

    event of injury. More specifically, we are designing an integrated US-EIT system and

    demonstrate proof-of-concept of US-EIT for enhanced ultrasound imaging capabilities of

    deep internal bleeding.

  • Electrical impedance tomography in pulmonary and cardiac applications

    Electrical impedance tomography in pulmonary and cardiac applications

    The most common application, so far, of electrical impedance tomography (EIT) has been pulmonary monitoring of patients. In particular, we have been pursuing EIT for cardiac output monitoring (a related application) and EIT as a surrogate for pulmonary function tests.

  • Combined whole breast ultrasound and electrical impedance tomography

    Combined whole breast ultrasound and electrical impedance tomography

    Ultrasound is a supplemental screening technique that has good sensitivity in dense breasts, is inexpensive, and is widely available, but unfortunately, it has high rates of false positives. Electrical impedance tomography (EIT) is a second attractive modality that is low-cost and has shown promise for cancer detection and in differentiating fibrocystic tissues from other tissues. Combining automated whole breast ultrasound (ABUS), which is a recent improvement to standard ultrasound, with EIT may significantly reduce the number of false positives of ABUS. If successful, the combined ABUS/EIT system could become an important screening technology for women with dense breasts.

  • Enabling technologies for effective image-guided surgical navigation in trans-oral cancer surgery

    Enabling technologies for effective image-guided surgical navigation in trans-oral cancer surgery

    Throat cancers have been increasing in incidence worldwide. Despite advances in surgical and non-surgical management of these cancers, treatment continues to be associated with significant functional and cosmetic morbidity. More minimally invasive trans-oral surgical (TOS) approaches have reduced treatment morbidity and complications. However, one drawback of TOS is the difficulty in intraoperatively assessing tumor extent and locating major vascular structures. Surgical navigation with image guidance has shown improved safety and efficacy with other surgical procedures; however it is currently not feasible in TOS due to the soft tissue and airway deformation that occurs with placement of instruments needed to access the throat, thus rendering preoperative scans unusable in the intraoperative setting.

    The overarching objective of our research is to develop enabling technologies that allow for surgical navigation with image guidance for TOS. Our research strategy is to acquire intraoperative imaging during TOS in order to develop models of upper aerodigestive tract deformation that reflect the intraoperative state. This, in turn, would allow for registration of preoperative images to the intraoperative state. We are well equipped to solve this problem due to the unique intraoperative CT and MR imaging resources available at the Dartmouth Center for Surgical Innovation. We have successfully developed a 3D printable polymer laryngoscopy system which, unlike standard metal laryngoscopes, is CT and MRI compatible. We have also acquired preliminary intraoperative imaging data during laryngoscopy procedures. The next steps in this research will be to further quantify and characterize tissue deformation that occurs during TOS and ultimately develop a surgical navigation platform for trans-oral procedures.

  • Therapy monitoring

    Therapy monitoring

    Therapy monitoring is an important emerging application of imaging modalities. These and other current research topics include:

    • near-infrared imaging of brain tissue;
    • near-infrared spectroscopy for diagnosing peripheral vascular disease;
    • electrical impedance spectroscopy for radiation therapy monitoring;
    • magnetic resonance elastography for detecting brain or prostate lesions; to follow the progression of diabetic damage in the foot; and to answer basic questions of wave propagation in tissue;
    • microwave imaging spectroscopy for hyperthermia therapy monitoring, brain imaging, and detection of early-stage osteoporosis;
    • electrical impedance tomography for monitoring traumatic brain injury progression and therapy.
  • Combined ultrasound and electrical impedance tomography (EIT)

    Combined ultrasound and electrical impedance tomography (EIT)

    Combined ultrasound and electrical impedance tomography (EIT) puts 3-D ultrasound imaging together with EIT data in a co-registered volume. EIT relies on the mathematical processing of impedance data collected non-invasively from patients to reconstruct the 3-D distribution of the electrical properties of the tissues inside the patient. Combining ultrasound and EIT has the potential to greatly improve the quality and spatial resolution of the reconstructed electrical properties.

  • Electrical impedance imaging for prostate cancer screening

    Electrical impedance imaging for prostate cancer screening

    Electrical impedance imaging for prostate cancer screening is the process of imaging non-invasively the electrical properties (conductivity and permittivity) of the prostate and its vicinity using electrodes mounted onto an intracavitary probe.

  • Electrical impedance imaging for breast cancer screening

    Electrical impedance imaging for breast cancer screening

    Electrical impedance imaging for breast cancer screening is the process of imaging the electrical property (conductivity and permitivity) of tissue using electrodes located on the body surface. This project is one branch of the larger effort to develop innovative technologies for breast cancer detection.

  • Electrical bioimpedance

    Electrical bioimpedance

    Electrical bioimpedance measurements of tissue provide significant levels of contrast between benign and malignant pathologies due to the vastly different morphologies occurring between tissue types. Focal sensing or mapping of these properties can provide clinicians useful information regarding the extent and severity of diseases like cancer. Our group is currently developing technologies to couple bioimpedance sensors to clinical devices including: 1) intraoperative instruments for use in assessing surgical margins during tumor resection; and 2) standard biopsy needles for use in providing real-time pathological assessment of tissue.

Selected Publications

  • Halter RJ, Schned AR, Heaney JA, Hartov A, Paulsen KD, "Electrical properties of prostatic tissues: I. single frequency admittivity properties," Journal of Urology, 182:1600-1607, 2009.
  • Halter RJ, Schned AR, Heaney JA, Hartov A, Paulsen KD, "Electrical properties of prostatic tissues: II. Spectral admittivity properties," Journal of Urology, 182:1608-1613, 2009.
  • Halter RJ, Zhou T, Meaney PM, Hartov A, Barth, Jr RJ, Rosenkranz KM, Wells WA, Kogel CA, Borsic A, Rizzo EJ, Paulsen KD "Correlation of in vivo and ex vivo tissue dielectric properties to validate electromagnetic breast imaging: initial clinical experience," Physiological Measurement, 30:S121-S136, 2009.
  • Halter RJ, Hartov A, Paulsen KD, "Video Rate Electrical Impedance Tomography of Vascular Changes: Preclinical Development," Physiological Measurement, 29(3):349-364, 2008.
  • Halter RJ, Hartov A, Paulsen KD, "A broadband high frequency electrical impedance tomography system for breast imaging," IEEE Transactions on Biomedical Engineering, 55(2):650-659, 2008.

Patents

  • Remote-sensing, bluetooth-enabled resistance exercise band | 11623114
  • Surgical vision augmentation system | 11553842
  • System and method of laryngoscopy surgery and imaging | 10582836
  • Systems and methods for cardiovascular-dynamics correlated imaging | 10575792
  • Surgical vision augmentation system | 10568522
  • System, method and device for monitoring the condition of an internal organ | 8764672

Courses

  • ENGS 169: Intermediate Biomedical Engineering
  • ENGS 57: Intermediate Biomedical Engineering
  • ENGS 76: Machine Engineering
  • ENGM 189.1: Medical Device Commercialization (.5 credit)
  • ENGM 189.2: Medical Device Development (.5 credit)
  • ENGG 189.1: Medical Device Commercialization (.5 credit)
  • ENGG 189.2: Medical Device Development (.5 credit)

Videos

Seminar: Enabling the Surgeon of the Future—Technologies for enhanced surgical navigation

The Halter Lab

ENGS 76: Machine Engineering

Lab Tour: Dartmouth-Hitchcock Medical Center

Seminar: Smart Devices and Systems for Surgical Guidance

Seminar: Surgical Enhancement: Using Electrical Bioimpedance to Improve Clinical Practice

News

Research Quick Takes

Navid Rashedi

Feb 27, 2025

Early Detection of Internal Bleeding

PhD student Navid Rashedi (pictured), Professor Ethan MurphyAlexandra Hamlin '16 Th'17 Th'19, research associate Victor Borza, and Professors Jonathan Elliott, Ryan Halter, and Vikrant Vaze are co-authors of: "Detection of occult hemorrhage using multivariate non-invasive technologies" published in Physiological Measurement. "This work investigated machine learning to combine multiple technologies—electrical impedance and near infrared spectroscopy—to better detect internal bleeds in a porcine study. Internal bleeds are often not detectable until it's too late. This approach appears to detect them earlier and more accurately," said Murphy. 

DIADH team 2024

Jul 18, 2024

ENTerpoint Surgical Navigation System

The Dartmouth Innovation Accelerator for Digital Health (DIADH)—a partnership between the Center for Technology and Behavioral Health and the Magnuson Center—awarded $50,000 to a team (pictured) led by alum Yuan Shi Th'24, that includes Professor Ryan Halter, for their "ENTerpoint Surgical Navigation System." The system "has the potential to significantly enhance safety and efficacy of transoral robotic surgery while reducing costs," says Shi.

resident performing a suturing task using a da Vinci Single Port

Jun 06, 2024

Oral Retractor for Robotic Surgery

PhD researcher Yuan Shi, alum Xiaotian Wu '14 Th'19, Professor Ryan Halter, and Adjunct Professor Joseph Paydarfar co-authored "An Imaging-Compatible Oral Retractor System for Transoral Robotic Surgery," published in Annals of Biomedical Engineering. "This device enables artifact-free imaging, which makes intra-operative image guidance possible," said Shi. "We are getting ready to use this novel retractor system in a clinical study at DHMC."

LBNP experiment set-up

May 02, 2024

EIT for Early Bleed Detection

PhD students Spencer Bertsch Th'19 and Navid Rashedi, alum Yifei Sun Th'22, and Professors Ethan Murphy (first author), Jonathan Elliott, Ryan Halter, and Vikrant Vaze—along with DHMC and Mayo Clinic researchers—co-authored "Non-invasive biomarkers for detecting progression toward hypovolemic cardiovascular instability in a lower body negative pressure model" published in Scientific Reports. The paper summarizes how electrical impedance tomography (EIT) can be used as a novel marker for early bleed detection.

Feb 29, 2024

SPIE Medical Imaging Conference

At the SPIE Medical Imaging conference, PhD students Yuan Shi (Halter Lab), Chengpei Li, Haley Stoner, and William Warner Th'17 Th'19 (Paulsen Lab) presented their work on image-guided surgery, including talks on "A surgical navigation framework for image-guided transoral robotic surgery" and "Intraoperative stereovision cortical surface segmentation using fast segment anything model," and posters on "Large MRI specimen submersion phantom design" and "Smart line detection and histogram-based approach to robust freehand ultrasound calibration."

ENDO GIA stapler

Jan 11, 2024

A Better, Safer Surgical Stapler

Professors Ethan Murphy and Ryan Halter, and PhD student Harsha Devaraj, along with Medtronic collaborators, coauthored "Development of an Electrical Impedance Tomography Coupled Surgical Stapler for Tissue Characterization" published in IEEE Transactions on Biomedical Engineering. The featured article investigates the incorporation of electrical impedance tomography into a surgical stapler to improve outcomes. Further studies are planned based on the promising results.

Using an iPhone to produce accurate high-density EEG scans for electrode localization

Dec 14, 2023

3D iPhone Scanning for EEG

Alums Alicia Everitt Th'19 and Haley Richards Th'22 are first authors on "EEG electrode localization with 3D iPhone scanning using point-cloud electrode selection" accepted for publication by the Journal of Neural Engineering. The authors, including Professors Ryan Halter and Ethan Murphy, present a method "using an iPhone to produce accurate high-density EEG scans for electrode localization—providing a needed portable and inexpensive solution," says Murphy.