The Value of CT Contrast

If there was a tool available that would automatically improve your job performance by nearly one-third, you’d want to use it, right? (And no, we’re not talking about ChatGPT.) The tool is contrast media, and a new study in JAMA Surgery found that the use of contrast in emergency CT exams improved the diagnostic accuracy of radiologists by 30%.

Radiology has a love-hate relationship with contrast. Contrast media unquestionably improves medical image quality, but it also adds a layer of complexity to imaging operations. Patients have to be screened and monitored for contrast allergies and reactions, IV lines have to be placed, injectors have to be monitored and maintained. 

Radiology researchers and clinicians have explored a variety of methods for non-contrast imaging, in particular in the emergency setting, where the time spent setting up a contrast exam could delay patient care. 

But while the risks of giving contrast are extensively debated, what are the risks of not using it? Researchers from multiple US institutions sought to answer this question in a study of 201 patients who got CT scans in emergency departments for acute abdominal pain over 3 weeks in 2017. All patients were scanned on Siemens Healthineers’ Somatom Force dual-source dual-energy CT scanner.

The original scans were contrast-enhanced, and a dual-energy technique was used to produce non-contrast images. Both sets of images were read by faculty and resident radiologists. Compared to the gold standard of contrast CT at 100%, findings included:

  • Diagnostic accuracy of unenhanced CT was 70%, or 30 percentage points lower than contrast CT
  • Faculty radiologists were more accurate than residents for primary diagnoses (82% vs. 76%), but less accurate for actionable secondary diagnoses (87% vs. 90%)
  • Faculty made fewer false-negative primary diagnoses than residents (38% vs. 62%)
  • False-negative and false-positive results were common (19% and 14%, respectively)

The Takeaway 

Reducing the use of contrast is a worthy goal, but it carries risks of its own, as this study indicates. False-negative interpretations are among the worst kinds of radiology errors with non-contrast exams, and clinicians should weigh the diagnostic penalty of withholding contrast media in the emergency setting, especially given the extremely low rate of contrast reactions in low-risk patients.

GE HealthCare’s MRI Contrast Play

GE HealthCare has expanded its MRI contrast portfolio with the European debut of Pixxoscan. The gadolinium-based contrast agent gives GE another macrocyclic gadolinium-based contrast agent to sell in Europe, in addition to its Clariscan GBCA.

MRI contrast developers have been working to address one of the most persistent problems in MRI: their reliance on gadolinium. Gadolinium works great for lighting up MR images, but it’s a toxic metal that has to be bonded with a chelate – a sort of molecular cage – in order to be used safely in humans. 

Pixxoscan is a macrocyclic GBCA that’s based on gadobutrol, a formulation already used in Bayer’s Gadovist GBCA and that’s now available generically. Macrocyclic GBCAs are considered more stable and less likely to release gadolinium than linear agents. 

Most linear GBCAs have been barred from the European market since 2017. The FDA never took a similar approach, but the US market has largely shifted from linear GBCAs to macrocyclic agents due to safety concerns. 

GE HealthCare highlighted that Pixxoscan is formulated at twice the concentration of gadolinium ions, which reportedly enables it to be used at half the injection volume of other GBCAs. The company also said that the agent’s cage-like macrocyclic chelate provides high kinetic stability. 

Pixxoscan will start shipping initially in Austria, and GE HealthCare expects to expand it across Europe. A spokesperson didn’t confirm plans for a US rollout.   

Pixxoscan’s launch comes as two of GE HealthCare’s competitors, Guerbet and Bracco, are rolling out their formulations of gadopiclenol, a high-relaxivity agent that can be used at half the dose of conventional GBCAs. The companies collaborated on the development of the agent, which Guerbet is selling as Elucirem and Bracco as Vueway. 

The Takeaway

GE HealthCare’s launch of Pixxoscan gives the company another macrocyclic agent to sell in Europe in addition to Clariscan. The question is how the agent will compete with gadopiclenol from Bracco and Guerbet, which are already touting its dose and relaxivity advantages.

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-- The Imaging Wire team

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