The principle for “As Low As Reasonably Achievable (ALARA)” protocols have been to focus research and practice to near zero levels of radiation exposure. A common method for radiation dose reduction to patients in interventional procedures is to lower frames per second (fps), or x-ray pulses during pulse fluoroscopy. In turn, there is a decrease in radiation exposure. For example, instead of running at 30 fps (x-ray pulse every .03 seconds), one could run at 15 fps with the sacrifice of image quality (x-ray pulse at .06 seconds, producing a lag compared to real-time device location). The problem with this, however, is that the level of reduction is not as straight forward as it seems.
“One would expect a 50% dose reduction when going from 30 to 15 frames per second, but, because of increased milliamperage, the actual dose savings are 20%-28%.” (Mahesh M; 2001)1
That is, by decreasing the frames per second, you increase the intensity of radiation both you and your patient are exposed to (in addition to increase in scatter radiation) while simultaneously sacrificing crucial image quality. If this sounds counter intuitive, that is because it is.
The solution? Inhibit the total amount of radiation that reaches the patients skin while preserving the whole field of view necessary for the procedure. Or, instead of reducing the speed and increasing the intensity of the x-ray, keep the speed and intensity the same while correspondingly preventing unnecessary radiation exposure to the patient with a physical block.
By “capturing” the full field of view once per second, then focusing radiation to a small region using an automatic secondary collimator, Omega Medical Imaging allows for a significant radiation reduction when running at the same frames per second compared to a conventional system. Bang et al.2 showed that when running at 12.5 fps during endoscopic retrograde cholangiopancreatography (ERCP) procedures, the Omega E-View Artificial Intelligence Fluoroscopy System reduced radiation by up to ~60% for both the patient and staff, a 32%-40% greater reduction than the method of reducing frame rates (assuming mA increase is consistent throughout fps reduction).
Because there will never be a zero level of radiation exposure when using radiation, the near-zero guided by ALARA is consistently a goal to reduce deterministic and stochastic effects of radiation and improve patient care. Current methods, while sufficient for the time, are starting to become obsolete as new innovations in the field of radiation safety, such as the Omega Artificial Intelligent collimator, gain traction in the interventional field.
- Mahesh M. Fluoroscopy: Patient Radiation Exposure Issues. Imaging and Therapeutic Technology. 2001;21:1033-1045.
- Bang JY, Hough M, Hawes RH & Varadarajulu S. Use of artificial intelligence to reduce radiation exposure at fluoroscopy-guided endoscopic procedures. American Journal of Gastroenterology. 2020;00:1-7