# Hybrid virtual-MRI/CBCT: A new paradigm for image guidance in liver SBRT

> **NIH NIH R01** · UNIVERSITY OF MARYLAND BALTIMORE · 2022 · $563,843

## Abstract

ABSTRACT
This proposal aims to establish a hybrid virtual-MRI/CBCT system for precision image guidance in radiation
therapy of liver cancer. Stereotactic body radiation therapy (SBRT) improves the treatment outcome over
conventional fractionated radiotherapy by delivering high fractional dose in few fractions. However, SBRT of
liver cancer still has high local failure rate up to 20-30% at 2-3 years and high overall grade>=3 toxicity rate up
to 30% with patient deaths from the treatment. Previous studies demonstrated a strong correlation between the
treatment outcome and the tumor localization accuracy of the image guidance technique used. Currently, cone
beam CT (CBCT) is the most widely used imaging technique for liver SBRT. However, CBCT has extremely
limited soft tissue contrast with no visualization of most liver tumors. As a result, its localization error is
frequently over 6mm, and the dose coverage of tumor volume can fall below 90%, which is far from enough for
tumor control. Drastically reducing localization errors is imperative to improve the outcome of liver SBRT.
Combined MRI-Radiotherapy machines could provide MRI contrast for liver tumor localization. However, such
machines are rare and expensive for most clinics. As such, an alternative solution is urgently required to meet
the ubiquitous need of all radiation oncology departments: a solution in the form of a novel low-cost imaging
system with MRI equivalent contrast. Since CBCT is readily available on most radiotherapy machines, creating
CBCT-based imaging systems would be the most effective strategy. Our recent publication demonstrated the
feasibility of such strategy. (Harris, Med Phys 2018) Our long-term goal is to establish the next generation of
CBCT systems with virtual multi-modality imaging capabilities for high precision tumor localization and adaptive
therapy in radiation therapy. In this application, our overall objective is to establish a novel system to generate
hybrid virtual-MRI/CBCT from CBCT, with virtual-MRI inside the liver for target localization and augmented
CBCT outside the liver for healthy tissue verification. The specific aims are: (1). Establish a 3D hybrid virtual-
MRI/CBCT system for image guidance in breath-hold liver SBRT without respiratory motion. (2). Establish a 4D
hybrid virtual-MRI/CBCT system for image guidance in free-breathing liver SBRT with respiratory motion. (3).
Optimize and clinically evaluate the systems through simulation studies and a prospective clinical trial. Our
expected deliverables through the academic-industrial partnership are novel hybrid virtual-MRI/CBCT systems
ready to be integrated to all radiotherapy machines with only CBCT systems. This new imaging capability will
have significant clinical impact because it will create a paradigm shift in image-guided radiation therapy by
revolutionizing the widely used CBCT systems to enable a new era of low-cost high-precision virtual multi-
modality guided radiotherapy. This precis...

## Key facts

- **NIH application ID:** 10229488
- **Project number:** 5R01EB028324-04
- **Recipient organization:** UNIVERSITY OF MARYLAND BALTIMORE
- **Principal Investigator:** Lei Ren
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $563,843
- **Award type:** 5
- **Project period:** 2019-09-30 → 2025-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10229488

## Citation

> US National Institutes of Health, RePORTER application 10229488, Hybrid virtual-MRI/CBCT: A new paradigm for image guidance in liver SBRT (5R01EB028324-04). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10229488. Licensed CC0.

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