Cardiovasc Imaging Asia.  2020 Apr;4(2):38-44. 10.22468/cvia.2020.00024.

Low Iodine Dose is Related with Overestimation of Extracellular Volume Derived from Cardiac CT

• Arakawa H
• Tomizawa N
• Chou S
• Matsuoka S
• Yamamoto K
• Inoh S
• Nojo T
• Kumamaru KK
• Fujimoto S
• Nakamura S

• KMID: 2502249
• DOI: http://doi.org/10.22468/cvia.2020.00024

Abstract

Objective
To assess the relationship between the amount of injected contrast medium and the extracellular volume (ECV) value during cardiac CT and to propose a minimum amount of contrast medium necessary to correctly calculate ECV.
Materials and Methods
A total of 95 patients who underwent comprehensive cardiac CT were included. Patients first underwent myocardial CT perfusion (CTP) with a contrast medium dose determined by the body weight (<70 kg: 50 mL; 70–89 kg: 55 mL; ≥90 kg: 60 mL). Coronary CT angiography (CTA) scan followed with a contrast medium dose of 0.8×body weight (kg). We defined the ECV value calculated after CTP as ECVCTP, and we used the ECV value calculated after the CTA exam as the reference standard (ECVref). We calculated the difference in ECV values (ECVdiff) as ECVCTP-ECVref.
Results
The injected iodine doses during CTP and the entire exam were 284±50 and 559± 69 mg iodine/kg, respectively. There was a weak but significant negative relationship (R2=0.07, p=0.01) between the injected iodine dose during CTP and ECVdiff. The ECVdiff of patients who received an injected iodine dose of <285 mg iodine/kg during CTP was significantly higher (2.7±4.1 vs. 0.8±3.4%, p=0.02) than that of the remaining patients.
Conclusion
ECV derived from cardiac CT might be overestimated when a small amount of contrast medium is injected. Injection of ≥285 mg iodine/kg is adequate to calculate the ECV value using cardiac CT.

Keyword

Contrast agents; Extracellular space; Multidetector computed tomography