# Markerless Motion Tracking of Lung Tumors using Dual Energy Imaging

> **NIH NIH R01** · LOYOLA UNIVERSITY CHICAGO · 2024 · $285,230

## Abstract

Project Summary/Abstract
 Lung cancer is one of the most common and deadliest malignancies in the world. Radiation therapy (RT) is
often used alone or in combination with surgery or chemotherapy, and thus is a critical component in the
management of this disease. However, accurate delivery of RT in the lung is limited by respiratory motion, which
can result in significant displacements of the tumor (up to 2 cm). Without compensation, this motion necessitates
the irradiation of a larger volume of normal lung to account for displacement of the tumor. This larger volume of
lung irradiated increases the incidence of symptomatic radiation pneumonitis. A number of methods have been
used clinically to reduce the volume of lung irradiated including the use of breath hold and compression.
However, both are uncomfortable and difficult for patients who often have multiple comorbidities. Alternatively,
researchers are evaluating methods to track the tumor in real time and potentially adapt the treatment parameters
to the position of the lung tumor. Methods to accomplish this goal require the implantation of fiducial markers or
electromagnetic transponders. However, implantation of these devices carries a significant risk of pneumothorax,
pulmonary hemorrhage and exacerbation of underlying chronic obstructive pulmonary disease (COPD). Another
approach for tumor tracking – markerless tumor tracking (MTT) – relies on images of the tumor obtained at the
time of treatment. The most common modality for the delivery of RT is the linear accelerator equipped with an
on-board imager (OBI). X-ray-based MTT, using planar MV or kV imaging on a standard linear accelerator, is
attractive as it uses a widely available technology and can be performed in near real time. In cases where the
tumor is clearly visible, x-ray-based MTT can track tumors with a high degree of accuracy. However, a major
difficulty with MTT is that tumor-overlapping bone may not be detectable on x-ray projections.
 Our group has explored dual energy (DE) fluoroscopic imaging to increase the likelihood of successful and
accurate MTT, and have implemented DE imaging on the OBI of a commercial linear accelerator using fast-kV
switching technology. DE imaging involves obtaining x-ray images at high (i.e., 120 kVp) and low (i.e., 60 kVp)
energies. By performing a weighted-logarithmic subtraction (WLS), a third image is produced that suppresses
bone and enhances soft tissue/tumor visibility. Our hypothesis is that implementing DE imaging on a linear
accelerator will enable a practical and cost effective method for enhanced tumor visualization and image
guidance in lung RT. Moreover, DE imaging will allow for MTT ensuring a high dose is delivered to the tumor
while limiting the volume of normal tissue irradiated. To test this hypothesis and to accomplish the goals of this
research, the following specific aims are proposed: A) Identify areas for improvement in fast-kV DE imaging and
MTT with the goal toward cl...

## Key facts

- **NIH application ID:** 10817079
- **Project number:** 5R01CA207483-06
- **Recipient organization:** LOYOLA UNIVERSITY CHICAGO
- **Principal Investigator:** Mathias Lehmann
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $285,230
- **Award type:** 5
- **Project period:** 2017-03-15 → 2026-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10817079

## Citation

> US National Institutes of Health, RePORTER application 10817079, Markerless Motion Tracking of Lung Tumors using Dual Energy Imaging (5R01CA207483-06). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10817079. Licensed CC0.

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