Amid growing alarm about radiation from CT scans, Mass General Imaging is leading the way to reduce patient exposure.

Reducing CT radiation exposure an ongoing point of emphasis

Amid growing alarm about radiation from CT scans, Mass General Imaging is leading the way to reduce patient exposure.


Concern about radiation exposure from CT (computed tomography) exams has risen dramatically in the wake of a new study that claims the scans will cause a significant increase in new cancer cases and cancer-related deaths. In addition, recent incidents in California, in which patients received excessive radiation through apparent human error, have added to the sense of unease over what is an effective and often life-saving exam.

At Massachusetts General Hospital Imaging, radiation dose reduction has long been a priority--a matter of both unending caution and ongoing innovation. The safety of our patients is always our primary concern, and Mass General Imaging has been at the forefront of research into reducing radiation dose since the mid 1990s. Today our entire staff, including radiologists, the technologists who administer most exams, researchers, and equipment engineers, is engaged in the effort.

Our radiation-reduction efforts focus on:

  • Preventing accidental, isolated incidents of excessive exposure, like those in the recent cases in California.
  • Reducing cumulative radiation dose: the sum total of radiation received by a given patient over time.

Here's a rundown of the ways we work to minimize both accidental and cumulative radiation dose.

Safety checks

Mass General Imaging employees follow strict procedures for checking and double-checking patient information and the type of exam to be performed. The simple act of repeating this information can make sure everyone is on the same page and prevent, for example, a person receiving an unnecessary exam.

Smart protocols

The most important tool we use to reduce radiation exposure is called a "protocol." A protocol is simply a detailed description of how each exam should be conducted--how much radiation to use, how many passes to make over what part of the patient's body, and so on. We have hundreds of protocols for all types of exams on all types of machines, including CT scanners. Our physicians supervise the creation and editing of these protocols over time.

Unlike some medical facilities, we pre-program these protocols into our scanners. This greatly reduces the opportunity for error. The technologist performing the exam need only select the correct protocol from a menu--as opposed to selecting each setting individually in a painstaking and error-prone process.

Dose customization

The CT technology we use gives us the ability to intelligently customize the radiation dose according to the patient's weight, age, medical history, and the body part being scanned. This is especially important for pediatric patients, as well as patients who must receive frequent scans as a part of their care. Moreover, it is simply a part of our culture to reduce the dose as much reasonably possible for all exams.

Dose reduction is a challenging process. It requires a careful balancing of several factors. In general, higher radiation results in a better image. Excessive reduction of radiation dose, therefore, can introduce image noise, leading to an inferior image that may threaten the radiologist's ability to make an accurate diagnosis. For example, a poor quality scan might result in a "false positive"--leading the radiologist to believe disease is present when it is not. Or, a low-quality image might force a repeat scan, which is obviously not in the patient's interest because it repeats radiation exposure.

Teams of our specialty trained radiologists, in consultation with on-staff physicists and our CT technologists, refine the CT exam protocols on an ongoing basis, looking for opportunities to reduce radiation while making sure that image quality remains at a desirable level. We have identified one or more champion radiologists in each specialty area who are designated to oversee the CT protocols relevant to their practice.

Our doctors and researchers play a leading role in the international effort to develop dose-reduction strategies that achieve diagnostic image quality; they are frequently cited in journal articles and appear at conferences. We take pride in our low dose protocols and frequently share them with radiologists and hospitals around the world.

Our CT technologists are highly skilled and invested in this endeavor and they follow the policy and procedure laid down to ensure appropriate protocols are being followed for each patient exam. Our CT team also receives frequent education to ensure consistency and safety.

We also take advantage of improving technology. For example, smart scanners and advanced image-processing software can help to deliver quality images at lower radiation levels. Our doctors also work closely with the scanner vendors to help define the next generation of equipment.

Dose-modification techniques received a stamp of approval in early December when the US Food and Drug Administration included such measures in a set of initial recommendations aimed at reducing radiation exposure from certain types of CT scans.

The American College of Radiology (ACR) publishes guidelines on radiation levels for various types of scans. Mass General Imaging comes in well below these levels for most exams, according to Dr. Dushyant V. Sahani, Director of CT Imaging. For certain exams our doses are similar to the normal amount of background radiation a person experiences in a year in the US.

"Radiation dose is a moving target," Sahani says. "And we have not reached where we ultimately want to be. We will continue our clinical and research efforts in this area, so that the risks from CT are considered negligible."

Decision support

One great way to reduce radiation exposure is to avoid giving radiation in the first place. In many situations, an MRI or an ultrasound exam may be just as effective as a CT while exposing the patient to zero ionizing radiation. At Mass General Imaging, the system that doctors use to schedule exams contains "decision support" intelligence that helps identify such situations. The system requires the doctor to answer questions regarding the patient and guides him or her to alternatives when appropriate.

Duplicate exam prevention

Massachusetts General Hospital ImagingOur scheduling system also warns when the patient has recently had a similar exam or when a similar exam has already been scheduled.

Equipment maintenance and replacement

Mass General Imaging takes every precaution to make sure our equipment remains in top-flight condition. Engineers employed by the scanner vendors are stationed on site at the hospital, working closely with our own experts. In addition, Mass General Imaging employs a full-time physicist who independently checks to make sure that the scanners are emitting the correct amount of radiation. Finally, we are aggressive about replacing outmoded equipment with the latest technology in order to deliver the highest image quality and the lowest possible radiation to our patients.