The Oncology San Antonio Cancer Care Network’s Radiation Oncology Team is a Vital Part of Our Multidisciplinary Approach to Cancer Treatment. 

Radiation therapy, or radiotherapy, employs ionizing radiation to kill cancer cells. 

The goal is to give the tumor a lethal dose of radiation while limiting the exposure to the surrounding healthy tissue. Prior to treatment, the radiation oncology team makes extremely precise calculations to contour the shape and intensity of the radiation beam for maximum accuracy.

3-D Conformal Therapy

This technology allows us to shape the radiation beam around the tumor, limiting exposure of surrounding tissue. We use Computer Tomography (CT) images to construct a 3-Dimensional, computer-generated image of the internal organs and the tumor, which greatly facilitates targeting the treatment area.

Computer Tomography (CT) Scanning & Simulation

We use CT scanning and simulation to map the organs and structures within the body and acquire precise measurements and other technical data. This information helps the radiation oncologist and staff prepare and deliver the radiation in the most focused manner possible.

GammaKnife® Radiosurgery

GammaKnife® radiosurgery uses gamma rays focused through a target point in the patient’s brain. The dose of radiation is delivered to the tumor in one treatment session and has proven effective for benign or malignant brain tumors.


Electron Beam Therapy (EBT)

An external radiation treatment method that is useful for skin cancers or tumors that are growing beneath the skin, but very close to the surface.

Intensity Modulated Radiation Therapy (IMRT)

IMRT targets the tumor with multiple high-energy x-ray beams, precisely focused to kill cancer cells while sparing healthy tissue. The strength of the beams can be adjusted to exactly accommodate the size, location and stage of the cancer.

Image Guided Radiation Therapy (IGRT)

A radiation treatment supported by enhanced graphic targeting, IGRT targets the treatment area using 2-D and 3-D imaging. This precision can achieve better patient outcomes with fewer side effects. IRGT has proven effective in treating prostate, breast, lung, spine, cancers of the head/neck and other sites in the body.

Bertha Leal
Radiation Physician Coordinator

(Dr. Stewart)
Office Phone: 210.544.5111
Fax: 210.299.8099