@DrAttai T1. Radiation therapy (RT) is the use of ionizing radiation as way to focus subatomic energy to interact with a particular part of body in order to treat a disease. #bcsm #radonc 1/
@DrAttai T1. Radiation oncology is a specialty that evolved out of radiology, which emerged as a medical field with the discovery of the x-ray in 1895. I was a history major, so I’ll share this more as a story #bcsm #radonc 2/
@DrAttai T1. In the early 20th century, radiation used either an electrically generated beam of x-rays at a high energy (x-rays) or by radium, a radioactive element discovered by Marie Curie emitting gamma rays. X-rays and gamma rays are both photons, or light. #bcsm #radonc 3/
@DrAttai T1. The x-rays are used for external beam radiation or teletherapy (treatment at a distance) while radium emitted gamma rays from internal radiation in/on the body, called brachytherapy (short therapy) #bcsm #radonc 4/
@DrAttai T1. Radium is rarely used now, as other radioactive materials are safer and easier to use. In breast cancer Iridium192 is probably the most common type. #bcsm #radonc 5/ 
@DrAttai T1. Technology improved in the 1960s so that higher energy x-rays could treat inside the body, and it would spare the skin while treating inside. The contemporary version of external beam radiation (XRT or EBRT) is the linear accelerator #bcsm #radonc * 6/
@DrAttai T1. When the x-rays first pass through the body, at the skin surface there is a little less dose. The actual dose patients receive isn’t the x-rays, but the body’s own electrons jostled out of its normal position by x-rays #bcsm #radonc 7/
@DrAttai T1. The electrons give the dose treating the disease and causing side effects. We’ll discuss how it works treating disease later. But high energy x-rays (4+ megavolts, usually 6-10) don’t convert into electrons for a few millimeters #bcsm #radonc 8/
@DrAttai T1. So what is radiation therapy doing? Well, the classic answer is that electrons interact with water, creating radicals causing DNA breaks in both strands, damage that can lead to cell death. It’s become more complex that, but it’s still important. #bcsm #radonc 9/
@DrAttai T1. Using enough flow of electrons (a certain dose), the goal is to damage cancer cells so they die off or stop growing. It can cause normal tissue injury so we have worked to find ways to strike the right balance #bcsm #radonc 10/
@DrAttai T1. Currently, we can’t individualize that balance well, so we go by randomized trials that guide us on the appropriate dose, how often to treat, and how large an area to treat. #bcsm #radonc 11/
@DrAttai T1. External radiation is non-invasive, but it requires planning to make sure that it’s (a) accurate and (b) precise so it can be given safely. So radiation therapy requires a process called ‘simulation’ to design treatment #bcsm #radonc 12/
@DrAttai T1. When I started in 1999, we used x-ray machines but now routinely plan treatment on a CT scan. CT planning allow us to do a 3D radiation plan design seeing internal anatomy. #bcsm #radonc 13/
@DrAttai T1. At the end of the simulation process, patients usually receive permanent ink tattoos just under the skin to help ensure accuracy and precision of setup. Simulation is the longest step to be sure the daily treatments are accurate, safe and quick #bcsm #radonc 14/
@DrAttai T1. Radiation oncologists like catchy lingo. All related are 3DCRT (3D, conformal radiation) as CT defined treatment. IMRT = sophisticated planning of 3D; IGRT=accounting for motion daily or while beam is on #bcsm #radonc 15/
@DrAttai T1. Sometimes we use electrons directly from the linear accelerator because they don’t penetrate far into the body. For breast cancer, sometimes electrons have advantages as part of treatment. #bcsm #radonc 16/
@DrAttai T1. What about protons? Protons are heavy positively charged particles. It require a bigger, more expensive machine to generate for radiation. It’s external beam radiation, with a different beam. #radonc #bcsm 17/
@DrAttai T1. Physical characteristics of proton beams give less dose beyond where radiation is aimed and may have potential health advantages, but its value is less clear in adults than in pediatric cancer patients. Carbon ions are similar, more expensive #bcsm #radonc *18/
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