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Medical Physics

Medical physics, says John Wong, PhD, director of the department’s Division of Medical Physics, is the “guardian of technology in radiation oncology. Medical physicists make sure that the equipment is correctly used and optimize the treatment approach. They also develop work flows for the radiation therapists to maximize quality and efficiency.”

That’s why medical physics research plays an integral role in the Johns Hopkins Department of Radiation Oncology and Molecular Sciences. “Our goal as researchers is to stay at the forefront of technology, matching clinical objectives with technological solutions. At Johns Hopkins, we aren’t aiming to use the latest machine just to say we can. We are looking to ensure that we provide our patients the best possible treatments and outcomes with the best in quality, efficiency, and the robustness of our solutions,” Dr. Wong explains.

The physics researchers at Johns Hopkins are a bridge, he says, between discovery and clinical use, between the laboratory and the treatment room. See a list of the researchers.

The research group currently has four major areas of focus:

Small Animal Focal Radiation Research Program

Animal research in radiation has traditionally been far behind other medical research areas. Since radiation needs to be tightly focused, it was impossible to treat animals in the same way that humans were treated because radiation machines were too large. That changed when Dr. Wong moved to Hopkins in 2004, bringing with him an idea to develop a downsized radiation machine that would enable researchers to use radiation on mice in similar ways radiation is used to treat people with cancer.

The Small Animal Focal Radiation Research Program (SARRP) allows detailed investigations of biological processes, disease progression, and response to therapy. It enables Hopkins researchers to:

  • Study the timing and scheduling of treatments
  • Look at the effect of radiation on normal tissue (how much toxicity normal tissue can withstand and still be healthy)
  • Examine fractionation, giving higher doses of radiation to shorten treatment times
  • Study how radiation affects stem cells and cognition. Can stem cells repair themselves? How does stem cell damage affect cognition?
  • Localize tumor control and minimize damage to healthy tissue
  • Test new chemical and biological radio-sensitizers
  • Investigate new radiation treatment protocols
  • Target the tumor micro-environment

The future of the program includes research on:

  • Integrated x-ray/BLT guidance
  • Multi-modality imaging
  • Target localization
  • Response assessment
  • Disease progression
  • New delivery methods

SARRP projects


  • Stem cell migration (Ford et al. Radiation Research, 2011)
  • Sertraline slows progression of Huntington Disease (Duan et al., Neurobiol. Disease, 2008)
  • APT – MRI differentiates necrosis and re-growth (Zhou et al., Nature Med., 2010)
  • Disruption of blood brain barrier for drug delivery
  • Vaccine mediated immunotherapy with radiation

Orthopedic Oncology (X. Cao, et al., PNAS, 2011)

  • Radiation damage bone marrow microenvironment for stem cells


  • Investigation of radiation protector
  • Radiosensitivity of a Twist-1 over-expressing lung tumor model


  • Vaccine mediated immunotherapy with radiation; PARP


  • Vaccine mediated immunotherapy with radiation
  • Radiation + intracellular nano-particle based hyperthermia


Oncospace is an informatics program whose goal is to more quickly improve clinical care. The program uses patient data (anonymous to protect privacy) on anatomy, radiation dose distributions, toxicity, and outcome to improve therapy for those about to be treated. This research aims to solve a problem that has existed in radiation research for years, which is that, as clinical trials are completed, technology has evolved to the point that the original research question becomes irrelevant.

With Oncospace, which was developed by Johns Hopkins researcher Todd McNutt, PhD, an analytical database pulls together radiation therapy data in a complex computerized system. That database enables users to analyze outcomes to figure out which worked best and which did not, providing clinicians with information that enables them to create optimal treatment plans.

“More and more, cancer research is data-driven,” says Dr. McNutt. “Oncospace surveys the data from prior patients to uncover similarities between tumors and their relationship to critical organs and tissue they want to spare from radiation. The system finds the set of critical organs from all patients in the system. This method provides upfront information on how good of a radiation dose distribution can be achieved as well as any potential toxicity risks to the patient. The information is then used to automate and ensure quality in radiation treatment planning.” (from Promise and Progress, 2010/2011, Volume One).

Oncospace is currently being tested in treatments for head and neck and pancreatic cancers. Early evidence shows that it considerably improves treatment plan quality and helps clinicians to spare critical organs. The program is being expanded to thoracic and other cancers.


The goal of robotic research taking place at Johns Hopkins now is to help clinicians place imaging and other equipment precisely and to be able to reproduce that placement time after time.

The basis of the program is multiple modality guidance. For example, with a CT scan, a radiation therapist can see the structure around the prostate but not the actual prostate or bladder. Ultrasound, on the other hand, can “see” the prostate and bladder. The current research uses robotics to place the probe, a placement that can be precisely reproduced for future treatments. Then the patient can be treated around the probe, sparing the healthy organ while treating the tumor.


Other research programs at Hopkins are examining quality:

  • An imaging guidance study is using patient data to answer how often imaging should be done in the course of radiation treatment. Every day? Every other day? Or some other length of time?
  • A safety margin study aims to define an institution-specific safety margin (which provides a border between the tumor being treated and the healthy tissue around it). Radiation professionals have traditionally learned safety margins from their teachers and supervisors. This research program is analyzing data to establish margins for each technique. Because practice standards and equipment vary by institution, the margins will be established for Johns Hopkins only. Once the research is disseminated, other institutions can use the findings to create their own margin baselines.


John Wai-Chiu Wong, PhD
Director of the Division of Medical Physics

Todd R. McNutt, PhD
Junghoon Lee, PhD
Robert Hobbs, PhD
Ken Wang, PhD
Kai Ding, PhD
Wolfram Laub, MBA, PhD

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