Medical Imaging Radiation Exposure in U.S. Dropped Over Past Decade

来自Imalogix的CT成像辐射剂量跟踪软件在RSNA 2019年展出。戴夫·福内尔摄。

More than a decade ago, there was an alarming, rapid rise in ionizing radiation exposure in the U.S. population that was mainly driven the increased use of medical imaging. One of the biggest drivers was the rapid expansion of computed tomography (CT). However, radiology society driven campaigns to lower doses and new technologies developed by imaging systems vendors have succeeded in cutting radiation exposure rates in the most recent assessment.

“We had a big report in 2009 called the Radiation Exposure to the U.S. Population, and it showed a dramatic rise medical radiation exposure. But, this new report shows that the overall radiation exposure to the U.S. population has gone down by between 15-20 percent over the past 10 years,” explained study co-authorMahadevappa Mahesh, Ph.D., chief of medical physicist and professor of radiology and medical physics, Johns Hopkins University, Baltimore, treasurer of the American Association of Physicists in Medicine (AAPM), a board member of theAmerican College of Radiology (ACR). He is also the co-chair of theNational Council on Radiation Protection and Measures Report (NCRP), and presented the most recent NCRP data analysis at the 2019Radiological Society of North America (RSNA)meeting.

TheNCRP 184 report涵盖了2006年至2016年期间，这是医疗保险和医疗补助服务中心(CMS)的最新数据。该报告显示，与2009年NCRP 160报告(涵盖2006年之前的时期)相比，美国人口受到的医学成像辐射剂量大幅下降。

Key findings of the study include:

• CT dose dropped about 6 percent, despite a 20 percent increase CT scans since 2006;
• Drop of more than 50 percent for nuclear imaging scans, mainly due to fewer procedures begin performed;
•所有x射线成像模式均可降低15- 40%。

Decreases show the impact of using"as low as reasonably achievable” (ALARA)principals, new dose guidelines outlined jointly by numerous medical societies, and American College of Radiology (ACR) dose reduction initiatives likeImage Wisely, Image Gently, and the ACR Dose Index Registry, Mahesh said

Mahesh, and many other medical physicist and radiology experts, have called for wider use ofradiation dose monitoringsoftware, because a hospital or imaging center needs to establish a baseline for its use of dose before they can measure the impact of any dose lowering efforts, changes in protocols, use of newer imaging equipment, or use of dose-lowering techniques. Some hospitals adopted dose recording software to improve their imaging protocols to improve safety for their patients and staff, but it was new recording requirements by the Joint Commission and some states that helped push many other facilities to adopt the technology.

He said there was growing concern a decade ago when the last council report was published, which showed a steep increase in radiation dose. This was mainly due to a rapid increase in the use of CT and other types of X-ray based and nuclear radiotracer medical imaging. This prompted the ACR to create the Image Wisely program and push for the use of more thoughtful imaging doses based on patient size, using the ALARA principle.

“The average dose to patients has gone down by 6 percent while CT exams have increased about 20 percent and we added new procedures likecardiac CTand CT perfusion,” Mahesh said. “Cardiac CT was one of the prime examples where we really saw the dose go down. In 2006, we were doing cardiac CT angiography exams with about 15-20 mSv of dose, but with the use of prospective gating CT technology it went down to 7-8 mSv. Then we had CT dose modulation, where we can do it at 3-5 mSv. If you are really enthusiastic and work at it, you can now go below 1 mSv. We have been able to do this in a decade and without the loss of image quality.”

Declines were seen across all the imaging modalities. Cardiac interventional angiography dropped 43 percent, non-cardiac interventional angiography dropped 40 percent, and radiography and fluoroscopy dropped 27 percent. However, he said the biggest decline was in nuclear imaging, where there was a 56 percent drop in dose. This was mainly driven by a decreasing number of nuclear exams, with many exams now being performed by CT.

“The technological advances over the past 10 years are really having an impact,” Mahesh explained. “For example, digital detectors are a lot more dose efficient so we don’t need the same amount of radiation to get the same image quality.”

Other technologies that have had a big impact on lowering dose include CT dose modulation, iterative reconstruction to improve image quality of lower dose CT scans, and dose recording and reporting software. “Now we have manufactures giving CT dose notifications so the users know when they exceed certain dose thresholds,” Mahesh said.

Dose recording software has helped prevent “dose creep” by the technologists who slowly increase dose of the imaging systems because it results in improved image quality. But now, systems send alerts when protocol limits are exceeded and can track which staff members are not following ALARA principles. This software also has helped lower the amount of dose received by staff.

他补充说:“此外，在过去10年里，我们看到人们对辐射剂量和优化的认识有了更多的提高。”“如果你知道你正在使用的剂量，你会尝试更谨慎地优化协议。我们现在也有认证要求来记录你的剂量。认证允许网站查看他们的协议。这并不能解决所有问题，但至少可以考虑优化剂量。”

He said participating in theACR Dose Index Registryalso provides hospitals feedback on what other sites are doing regarding dose and how your facility compares, which is a motivator to lower dose.

马赫什说:“我们也看到工作人员在x光和其他地方受到的辐射减少了，因为当我们降低病人的剂量时，每个人都受益。”

Find out more from this study in aVIDEO interview with Mahesh.