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Optimizing Imaging Dose and Quality through Monitoring

Proper medical imaging requires a careful balance between the quality and the safety of the exam.  A poor quality exam is a disservice to the care of the patient while an exam with more radiation dose than necessary can undermine its safety.

Five years ago, the imaging physics team at Duke University began looking at radiation dose values in patients undergoing imaging examinations and found that to optimize the balance between dose and image quality, the entire imaging chain needed to be evaluated. They determined that automated monitoring of objective measures of image quality is the best to achieve that balance.

Historically, radiation dose monitoring has been about aggregating dose data that is naïve to patient size, age, gender, body habitus, and resultant image quality. The only question that is normally asked of the dose monitoring system is whether the dose for a given exam exceeds some global threshold. “We are different in that we are asking more and targeted questions making sure they take into account patient-specific factors such as size,” says Joshua Wilson, a physicist at Duke. “A large patient may require a high dose to achieve necessary image quality, which appears as an ‘overdose’ and requires unnecessary follow-up while a small patient could receive 2- or 3-fold the necessary radiation dose for a good image and yet be well under the threshold.”

The Duke team’s approach is automating objective measures of image quality. “Beyond just compiling data on patient demographics, protocol parameters, and resultant radiation doses, we are compiling data on image quality that relates back to human observer preferences,” Wilson says. This way when radiologists, technologists, and medical physicists meet to discuss imaging protocols, parameter modifications can be driven by objective quantitative data rather than anecdotes. “More than ever before, medical physicists have a clear mandate to put their expertise to use in making medical procedures centered around the patient. It is a privilege for us that we can bring the science of medical physics to provide precise, consistent, and optimal patient-centered care,” says Ehsan Samei, the chief imaging physicist at Duke.

Size-specific dose estimate (left) and image noise (right) for three CT scanners as a
function of patient diameter for abdominal CT. Precision of imaging safety and quality
can be gauged by the spread of the data, respectively, which are used as optimization
metrics to improve the consistency of care across the clinical operation.