Our Commitment to Minimizing Radiation Exposure

radiation levels

CT doses at Mass General compared to national benchmarks

Radiation levels for common CT exams at Mass General, compared with national benchmarks and annual background radiation. Radiation measured in mSv (millisieverts).


Reduction in average CT radiation dose:

25% - Head
28% - Chest
39% - Abdomen/pelvis
42% - CT enterography
55% - Kidney stone (initial)
87% - Kidney stone (followup)
75% - Cardiac


Radiation reduction: Our ongoing commitment

Department of Radiology Chairman Emeritus James H. Thrall, MD, discusses our decade-long commitment to reducing CT radiation to as low a level as possible for each patient.  Watch now >

Mass General Imaging has developed software tools that help referring physicians choose exams that match the patient's needs—including radiation-free alternatives.  Watch now >

The Webster Center

The Webster Center for Advanced Research and Education in Radiation

Formed in 2010, The Webster Center for Advanced Research and Education in Radiation is devoted not only to reducing radiation exposure for our patients but also to sharing our methods with the world.

  • Mass General is a world leader in the development and implementation of dose-reduction technologies and methods.
  • Our typical dose levels for CT exams are at minimum 30% lower—and as much as 95% lower—than reference levels used by the National Council on Radiation Protection.
  • We customize CT exams for each patient based on weight, age, history, and other factors.
  • Minimizing radiation exposure includes using radiation-free alternatives, such as ultrasound and MRI, when clinically appropriate.
  • We maintain, upgrade, and replace equipment to ensure patient safety and take advantage of technology advances.

Although the life-saving value of imaging technology is undeniable, Massachusetts General Hospital Imaging understands the concerns that patients and their doctors have over radiation exposure, especially from CT (computed tomography) exams. Patient safety is a top priority for Mass General Imaging, and our entire organization—including radiologists, the technologists who administer most exams, researchers, and equipment engineers—is engaged in the effort to prevent accidental exposure and minimize the amount of radiation used in every exam.

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."

Our Pediatric Patients

We are committed to minimizing radiation exposure for all patients, but especially for children. In addition to multiple safeguards to prevent accidental exposure, we strive to continually improve the protocols that govern each type of scan—so that we can use less radiation but still obtain images sufficient for accurate diagnoses. The amount of radiation exposure from x-rays, CT scans and other imaging studies is limited to the minimum necessary to answer the diagnostic question.

Read the FAQ for Families

How We Minimize Radiation Dose

Reducing radiation exposure requires both unending caution and ongoing innovation. Mass General Imaging employs the following strategies:

Safety Checks

We 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 prevent, for example, a person receiving an unnecessary exam.

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 ingrained into our culture to reduce the dose as much as reasonably possible for all exams.

Dose reduction is a challenging process that requires a careful balancing of concerns. In general, higher radiation results in a better image. Too little radiation, 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 our 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.

Decision Support

The most effective 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 doctors to answer questions regarding their patients, provides alternatives, and even blocks the booking of inappropriate exams.

Duplicate Exam Prevention

Our scheduling system also warns when the patient has recently had a similar exam or when a similar exam has already been scheduled.

Mass General Imaging radiation safety

All members of Mass General Imaging,
including the technologists who administer
most exams, are involved in reducing
radiation exposure.

Equipment Maintenance and Replacement

Mass General Imaging takes advantage of improving technology. For example, smart scanners and advanced image-processing software can help to deliver quality images at lower radiation levels. Our researchers and doctors work closely with the scanner vendors to help define the next generation of equipment. We keep to an aggressive schedule for upgrading or replacing outmoded equipment with the latest technology in order to deliver the highest image quality and the lowest possible radiation to our patients. Finally, we take 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.

More on Radiation Dose Reduction

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