UAB Radiation Oncology, Rays of Hope Volume 5 issue 1 | Page 13

CLINICAL SPOTLIGHT 
PROTON PHYSICS
Rex Cardan, Ph.D.,
tapped to lead Proton
Physics 
Dr. Rex Cardan, a medical physicist with UAB for nearly 7 years,
has been leading the physics support at the Acton Road and
Alexander City campuses. In that time, he has helped to develop
and improve UAB quality programs at each site, commissioned
two new linear accelerators, and has overseen the treatment of
thousands of patients.
     Along with his clinical service, Dr. Cardan is a mentor in the
physics residency program and is actively involved in the
academic mission at UAB through leading talks at national
conferences, working and publishing on advancing technology
projects in radiation oncology, and developing open source
software solutions used internationally to help win the fight
against cancer.
     In 2017, he started Red Ion LLC, a startup company which
has since developed radiation oncology software for large
hospitals and companies including Varian Medical Systems.
Here at UAB, he is known mostly for his automation plan check
software “X-Check” which inspects each patient treatment plan
prior to delivery and has helped deliver the safest treatments
across all of the UAB sites.
     Focused on the future and passionate about advancing
software automation systems in radiation oncology, Dr. Cardan
continues to lead the way in software systems and help UAB
shine a light in both the national and international landscapes.
The dose-depth curve of protons and photons can be seen in the
image below:
Rex Cardan, Ph.D. will be the Proton Physicist for Proton International
at UAB.  Image by Laura Cardan Photography.
Why is Proton Therapy a
preferred treatment
option?  What is the
Bragg Peak?
Proton therapy is different than traditional radiation therapy in
the way the energy is delivered to the patient. With proton
therapy, very little dose is delivered along the path prior to
reaching the target. Instead, protons deliver most of their
energy at a prescribed, programmable distance inside the
body, known as the Bragg Peak.  Immediately after this burst of
energy, the proton completely stops to irradiate.  This type of
treatment delivery differs from traditional radiation therapy,
which deposits most of its energy near the surface of the body. 
Image source:  Stack Exchange Physics, Dose-depth curve of photons vs.
protons, https://physics.stackexchange.com/q/169665.
Source: varian.com/oncology/products/treatment-
delivery/probeam-proton-therapy-system?cat=bragg-peak.
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