Therapeutic Medical Physics Research Lab
Medical Physics Graduate Program

Chihray, Liu, PhD; Faculty Member

Under the direction of Dr Chihray Liu, the Therapeutic Medical Physics research lab in the Department of Radiation Oncology is engaged in a variety of projects that are focused on cancer treatment using radiation.

These treatment techniques include:

  • High energy (MV) external photon beams
  • Low energy (OV) external photon beams
  • Heavy charged particle (Proton) external beams
  • Light charge particle (Electron) external beams
  • Brachy-therapy (Isotope or Micro-X-Ray Tube)


Clinical Workflow Optimization

The main mission of a therapeutic physicist is to provide a safe treatment environment and high quality of care for cancer patients. Workflow optimization includes (1) providing an accurate and efficient system of communication between different teams in the radiation oncology department that will result in the best possible quality of patient care; and (2) streamlining quality assurance procedures for patient treatment devices such as the linear accelerator. Development of these workflow procedures is of tantamount importance in providing a highly sophisticated, streamlined radiation oncology department.

Prototype Detector Development and Imaging Applications

Imaging is a critical component of image-guided radiation therapy. While much work in IGRTY has focused on image reconstruction algorithms and applications in adaptive therapy, much work in the development of suitable detectors remains. In collaboration with UF Nuclear Engineering, current activities include development of proton portal imaging detector based on exit dose imaging. Our prototype system involves a CCD camera system using 6LiF/ ZnS scintillation screen. New scintillation materials are being investigated for improved imaging signal performance.  As well, a Monte Carlo model is being developed to optimize detector geometry and performance limits in a high neutron scatter environment in proton therapy. The goal is to provide accurate visualization of proton collimation for QA and in vivo beam delivery. An ancillary project is the development and testing of He4 and Cs2LiYCI6 (CLYC) scintillation detectors capable of neutron dose and spectra measurement. These detectors can be used for measurements at proton therapy and nuclear facilities for more accurate radiation protection calculations.

Image Registration Strategies

The department is in the process of installing a state-of-the-art MR simulator, exclusively for radiation therapy patients. Research in MR image registration strategies are led by Drs. Samant and Wu, in collaboration with Philips. 3D MR data is registered with 2D MR cine imaging to determine patient internal organ movements during registration. 4D motion modeling and artificial neural network are used to build a fast, accurate, and robust image registration framework that is used to track abdominal targets for the gating of irradiation.

Application of Machine Learning in Radiotherapy

Machine learning has great promise for applications in radiotherapy, ranging from diagnosis, image analysis, treatment design to follow-up. The current goal of the physics team’s research in this area is to leverage the power of ML to address challenging issues in radiotherapy treatment design and quality assurance. The team’s effort focuses on ML research that can impact our current practice and improve patient treatment quality and outcome.

IGRT/SBRT Clinical Implementation

Advanced image-guided radiation therapy systems provide the technical platform to deliver extremely precise, intense doses of radiation to tumors using the technique known as stereotactic body radiation therapy (SBRT). Our goal is to leverage on-going advancements in IGRT, organ motion management, and beam delivery technologies to enhance SBRT treatment outcomes and to explore the promise and potential of SBRT as a paradigm of curative treatment and local tumor control for various disease sites, including the lungs, spine, and liver.

Dose Calculation/Plan Optimization

Intensity-modulated radiation therapy and volumetric-modulated radiation therapy (VMAT) represent one of the most significant technical advances in radiation therapy since the advent of the medical linear accelerator. It allows the clinical implementation of highly conformal nonconvex dose distributions. However, these advances do not come without a risk. IMRT is not just an add-on to the current radiation therapy process; it represents a new paradigm that requires the knowledge of multimodality imaging, setup uncertainties and internal organ motion, tumor control probabilities, normal tissue complication probabilities, three-dimensional (3-D) dose calculation and optimization, and dynamic beam delivery of non-uniform beam intensities. Among all those factors, our group’s research interests focus on how to improve the dose computation accuracy while maintain the computation efficiency during IMRT/VMAT planning process.

Quality Assurance

Quality assurance is essential in the safe and effective delivery of radiation treatment. Our group has collaborated with industry leaders in developing innovative ways to streamline the QA process. Both commercial products as well as in-house developed methods have been in use for periodic machine QA and patient-specific QA. We are constantly reviewing our QA programs to ensure safe radiation delivery and to increase QA efficiency.