NIST researchers develop method to improve CT scanners

4 March 2019 (Last Updated March 4th, 2019 16:21)

US National Institute of Standards and Technology (NIST) researchers have proposed a new measurement technique to improve the calibration of computed tomography (CT) scanners.

US National Institute of Standards and Technology (NIST) researchers have proposed a new measurement technique to improve the calibration of computed tomography (CT) scanners.

NIST added that the new approach could potentially optimise patient treatment by enhancing communication among doctors.

This new method outlines that the X-ray beams produced by CT scanners could be measured to enable useful comparison of scans from different devices.

It also facilitates the creation of the first CT measurement standards linked to the International System of Units (SI) by devising a more precise definition of units used in CT.

Every radiology facility has to regularly calibrate a CT machine by scanning an object of known radiodensity called a phantom to check whether its measurements give the right number of HUs.

A challenge faced during calibration is that a CT scanner’s X-ray generating tube produces a beam that is the white light’s X-ray version with photons having different wavelengths.

As a photon’s penetrating power is connected to its energy, the beam’s overall effect on the phantom has to be averaged out, making the calibration difficult.

In addition, the tube’s X-ray light has to change based on the type of scan, making the calibration more challenging. This is further complicated by the differences among various CT machine manufacturers.

“Better comparisons among scanners might allow us to establish cutoff points for disease such as emphysema getting a particular Hounsfield score or lower.”

Considering all these challenges, the NIST scientists believe that a universal standard would be beneficial, while improved calibration could make diagnosis more efficient and less expensive.

NIST scientist Zachary Levine said: “Better comparisons among scanners might allow us to establish cutoff points for disease such as emphysema getting a particular Hounsfield score or lower.

“It’s also common for CT scans to turn up suspicious growths that might be cancerous, and a doctor commonly orders an MRI as a follow-up. We might eliminate the need for that second procedure.”

The researchers used a linear algebra technique to simplify the data required to overcome the uncertainties created by the tube’s broad X-ray spectrum and voltage setting.

Levine added: “Basically, we’ve shown that you can create a CT scanner performance target that any design engineer can hit.

“Manufacturers have been getting different answers in their machines for decades because no one told their engineers how to handle the X-ray spectrum. Only a small change to existing practice is required to unify their measurements.”