VIDEO: Making sure lower dose X-ray is still diagnostic quality

Medical physicists have been working for the past decade or more to help implement ALARA and Image Wisely protocols to help reduce the amount of dose patients receive from computed tomography (CT), X-ray, fluoroscopy, and interventional angiography. Now, the ACR Quality and Safety Commission and Physics Commmission effort to develop a list of image qualiuty standards to measure for low-dose imaging to try and address the radiologists concerns about low image quality. 

"We wanted to use a quantitative way to see if we can come up with what metrics to measure," Mahesh explained. He said it has become apparent that a set of reproducible measurement guidelines is needed to ensure low-dose scans are still diagnostic quality. Often today, this is left to the judgement of radiologists, where their subjective interpretations can vary widely. 

"We are always talking about taking doses down, but if you go to much, you cannot build back that image quality, no matter what you do or if using deep learning algorithms," Mahesh explained.

The commission also realized this was not going to be a simple single number sort of solution because there are a lot of factors involved. So, they came up with a survey for all the specialties in radiology. It showed a set of images and radiologists were asked to rate what was most important between spatial resolution, motion, contrast resolution and other variables that can change the look of an image when reducing X-ray dose levels. Details from the study were presented at RSNA 2022. 

What they found was surprising to the researchers, because what is important boils down to which subspecialty radiologist you ask, or was type off exam they are looking at. 

"For MSK for example, they were con defend about contrast, but not motion because there is not much motion in the legs," Mahesh said. "Whereas the cardiac guys highly rated motion artifact as a big issue."

The details found in the survey will help the commission develop tags for image quality importance based on the exam protocol. This will be used to develop what is being called a "clinical diagnostic reference level," which will be clinically indicated, rather than just looking at how much dose has been cut our of scan without understanding what features a radiologist might need to focus on in certain types of exams.  

While lower radiation dose is important, it also needs to be tied to image quality metrics, Mahesh explained. 

"In some programs, the images are rated based on radiation dose, rather than the image quality, and that is driving some people to lower the dose and it is not doing justice for the patient," Mahesh said. 

The goal of the initiative is to create clinical diagnostic reference levels for all types of exams, such as head CT, cardiac CT, And others. 

"It is not easy to do, which is why we created the survey the different subspecialties because we wanted them to think about this and to get buy in," he explained. "When we publish this, we don't want it to just be on paper, we want it to be practical."

Once published, this also will be something that ACR plans to present to the Centers for Medicare and Medicaid Services (CMS), because this is something that should be tied into reimbursements. He said some reimbursements are tied to dose levels used, but in some cases, to pull the relevant clinical information out of these studies, a higher dose might be needed. 

"Our method can provide a quantifiable and reproducible measure," Mahesh said. 

Artificial intelligence (AI) and 3D printing might also have a role to play in rating studies for readability. AI can be developed to rate exams according to the factors in the quality control measures that are developed. Mahesh said 3D printing can now be used to create inexpensive patient phantoms based on real patient imaging studies to test and calibrate the AI algorithm.