New Imaging Technology
with Loralie Ma, MD, PhD
What software is used to view these combined images?
The abnormal and uncontrollable cell division that characterizes cancer can create life-threatening tumors. Radiation was one of the first groundbreaking technologies used to destroy these deadly cells that multiply in the body. Today, doctors have three main imaging tools to more accurately direct radiation and save lives: computerized axial tomography (CT) scans, positron emission tomography (PET) scans and magnetic resonance imaging (MRI) scans.
Radiologists can separately acquire the CT, PET and MRI images, which the radiation oncologists can then overlay to develop the most accurate radiation therapy plan possible. According to Loralie Ma, MD, PhD, Medical Director for Medical Imaging of Baltimore at GBMC and Radiologist at Advanced Radiology, the radiologists choose which technology to use, based on the imaging needs.
The CT scan creates computerized x-ray images of the body in cross-sections or three-dimensional views of the internal organs and structures of the body.
The PET scan provides images of biological and cellular functions of the body, highlighting the areas where cells are abnormally multiplying. Doctors inject a glucose (sugar)-based medication into the patient, which circulates through the body and collects in organs and tissues, making it easier to track on the PET scan. “Normal, healthy tissues take up less glucose but malignant tumors are growing at an accelerated rate and therefore take up more sugar,” says Dr. Ma. “This makes it easier to pinpoint the tumor with the PET scan and determine how it is functioning.”
MRI scans use magnetism instead of x-rays to view the cancer site. A radiologist can use an MRI to provide the radiation oncologist with details of the cancer cells and the normal soft tissues that cannot otherwise been seen on X-rays.
These scanning tools offer separate, yet fundamental information to help guide radiation therapy. GBMC was among the first hospitals to use a combination PET/CT scanning system. “The PET/CT scan provides precise information to assist our doctors in accurately locating the tumor to deliver high doses of radiation to the cancer and spare the surrounding, healthy tissue,” says Dr. Ma. The dual scanner provides the exact margin of the tumor so doctors can avoid under-treating the edges of the tumor, while not over-treating the surrounding area.
According to Dr. Ma, even more recent advancements in technology permit the fusion of PET/CT and MRI scans to give doctors an all-in-one imaging tool for diagnostics as well as sophisticated radiation therapy planning.
At GBMC, data from the various scans is imported into the new, state-of-the-art Eclipse treatment planning system. From there, the cancer care team develops a treatment plan for delivering the maximum amount of radiation directly to the cancer, while minimizing the radiation exposure to the normal tissue.
To pinpoint the cancer site even more precisely, radiologists use a new technique known as Image Guided Radiation Therapy (IGRT). During IGRT, ultrasound or x-ray images are obtained to make sure the cancer is positioned dead center in the field of treatment. This is done every day, prior to each radiation treatment, to ensure that the highest dose of cancer-killing radiation is given to one precise location.
