The relationship between calcium deposition and the development of coronary artery diseases (CAD) has been well known for decades. As early as 1990, Arthur Agatston and his colleagues introduced the first practically applicable procedure to quantify calcium in coronary arteries – but the acquisition methods for this quantification have not evolved much since then. This is set to change.
CACS history at a glance
Agatston and his colleagues considered any structure with a density of greater than 130 Hounsfield units (HUs) and an area of at least 1 mm² encountered in the coronary arteries to represent calcified plaque.
To be able to produce pictures in sufficient quality, Agatston set his Electron Beam CT (EBCT) to 130 kV. His procedure became standard for Coronary Artery Calcium Scoring (CACS) – also widely known as the Agatston Score – and so did his tube settings.
Up until now, reliable CACS results meant limiting image acquisition to 130 kV or, thanks to the improved spatial and temporal resolution of multidetector CTs (MDCT), to 120 kV. That lead to a significant lack of flexibility. “Nowadays calcium score at 120 kV can result in a comparable radiation dose to some coronary CTA protocols,” says Hugo Marques, MD, radiologist at the Hospital da Luz in Lisboa, Portugal. Modern imaging equipment however has advanced considerably since then, particularly the introduction of low kV for image acquisition and the associated benefits of radiation dose reduction. This raises the question: Is there a way to get CACS results comprising these benefits that neither over- nor underestimate the Agatston Score but are not subject to the usual “historic” restrictions? Luckily, the future is just around the corner.
Tackling restrictions with reconstruction
Currently, only Siemens Healthineers provides a special reconstruction kernel along with their proven low kV capabilities and the unique 10 kV step selection. With this powerful combination, the traditional restriction to 120 kV is tackled and kV settings can be chosen freely allowing for Agatston- equivalent calcium scoring with any kV. In CAD research – especially in trending topics like calcium subtraction – but also in everyday clinical use, this innovative approach has huge potential to become a game changer:
“Having the possibility of doing calcium score at lower kVs not only could result in a big radiation dose saving, but would also allow for similar kV settings in both calcium score and cCTA acquisitions.”
Following the same people-centered path as many other clinical fields, imaging technology will be matched to patients’ needs, rather than the other way around. This approach also offers great benefits for patients compared to conventional CACS: most importantly, it introduces the advantages of low kV scanning but could also allow the re-use of scans that were initially acquired for a different purpose. If there are existing images – for example native thorax acquisitions – for example native thorax acquisitions – it may be possible to use these directly for quantitative measure of coronary calcium. Reducing the number of scans necessary and lowering the voltage whenever possible opens up the potential to significantly save radiation exposure to patients. “Dose optimization for calcium score could have a big population impact since CACS as an advanced cardiovascular risk assessment exam is gaining acceptance especially on intermediate risk asymptomatic individuals.” Marques adds.
Ready to become an innovation leader?
Low-kV scanning and Tin Filter technology have proven their worth in other domains of cardiovascular imaging – and a few visionary pioneers have already realized how they can benefit from this new approach to calcium scoring in their daily routine. Now the time is right to join them.