What is the clinical evidence from this study?

Study design: Other. Population: Calcific aortic valve stenosis (in vitro model) (n=9). Intervention: Ultrasound (US) calcium scoring vs. Micro-CT calcium scoring. Primary outcome: Correlation between US calcium score and CT calcium score (R2 = 0.7391, p=<0.0001).

February 9, 2016Open Access

Quantification of Calcium Amount in a New Experimental Model: A Comparison between Ultrasound and Computed Tomography

Q: What are the key findings of this study?

A newly developed ultrasound method accurately quantified calcium amounts in an in vitro model, demonstrating a strong correlation with computed tomography calcium scores (R2 = 0.7391, p<0.0001).

KGKris GillisAZ Sint-Jan GBGezim BalaElectrophysiology BRBram RoosensVrije Universiteit Brussel

Key Result

A newly developed ultrasound method accurately quantified calcium amounts in an in vitro model, demonstrating a strong correlation with computed tomography calcium scores (R2 = 0.7391, p<0.0001).

Structured PICO

Does a new ultrasound method accurately quantify the amount of calcium compared to computed tomography in an in vitro phantom model?

Population

In vitro agar phantom model (2% agar) containing 9 different amounts of calcium-hydroxyapatite Ca5(PO4)3OH (2 to 50 mg)

Intervention

Ultrasound (US) imaging (10 MHz probe) with a new semi-automatic method for calcium quantification (US calcium score and volume)

Comparator

Micro-computed tomography (micro-CT), the current imaging gold standard

Outcome

Correlation of the calcium amount with US calcium score and CT calcium scoresurrogate

A novel ultrasound-based method accurately quantifies calcium amounts in an in vitro phantom model, showing strong correlation with micro-CT, suggesting potential for future clinical application in assessing valvular calcification.

Main Result

Effect estimate: R2 = 0.7391

p-value: p=<0.0001

Limitations

In vitro static model does not reflect moving structures in clinical practice
Direct contact with agar instead of ultrasound gel may not reflect clinical ultrasound transmission
Variable US equipment settings in clinical practice may interfere with calcium scoring
Use of a 10MHz US probe and high frame rate differs from typical clinical probes
Differences in spatial resolution between US and CT
Variable attenuation of US in vivo may limit the use of absolute values
Patient echogenicity and poor acoustic windows could cause insufficient image quality in clinical practice

Abstract

PURPOSE: Calcification is an important prognostic factor in aortic valve stenosis. However, there is no ultrasound (US) method available to accurately quantify calcification in this setting to date. We aimed to validate a new US method for measuring the amount of calcium in an in vitro model, and compare it to computed tomography (CT), the current imaging gold standard. MATERIALS AND METHODS: An agar phantom (2% agar) was made, containing 9 different amounts of calcium-hydroxyapatite Ca5(PO4)3OH (2 to 50 mg). The phantoms were imaged with micro-CT and US (10 MHz probe). The calcium area (areacalcium) and its maximum pixel value (PVmax) were obtained. These values were summed to calculate CT and US calcium scores (∑(areacalcium × PVmax)) and volumes (∑areacalcium). Both US- and CT-calcium scores were compared with the calcium amounts, and with each other. RESULTS: Both calcium scores correlated significantly with the calcium amount (R2 = 0.9788, p<0.0001 and R2 = 0.8154, p<0.0001 for CT and US respectively). Furthermore, there was a significant correlation between US and CT for calcium volumes (R2 = 0.7392, p<0.0001) and scores (R2 = 0.7391, p<0.0001). CONCLUSION: We developed a new US method that accurately quantifies the amount of calcium in an in vitro model. Moreover it is strongly correlated with CT.

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