# Evidence-Based Investigation of Coronary Calcium Score in Cardiac Computed Tomography
## 1 Introduction  
Computed tomography (CT) is one of the most important imaging modalities in current clinical practice, owing to its ability to provide diagnostic information quickly and non-invasively. It is used in research, as well as in the clinic, and can diagnose tumors, bleeding, infections, and fractures, and assess bone condition [1]. Advances in CT now allow the detection of stem cells labeled with gold nanoparticles [2]. Advances in CT equipment have also made it possible to obtain accurate images of coronary arteries. More recently, the development of multi-detector CT (MDCT) technology and various software packages has made it possible to diagnose coronary artery stenosis. Among the cardiac examinations performed using CT, the calculation of the coronary artery calcification score helps to determine the degree of coronary artery stenosis by quantifying calcification of the coronary arteries [3]. The advent of dual-source CT using two X-ray tubes and detectors allows image reconstruction with only a 90-degree rotation, thereby improving the temporal resolution two-fold with the same X-ray tube rotation speed as that of MDCT [4]. Thisfeature reduces the required examination time and allows excellent image acquisition, even at a heart rate of 70 beats/min or above [5; 6].  
Coronary images can be analyzed for calcification using coronary calcium quantification software, which determines the location of the calcification detected in the axial image, as well as its volume and mass. The results can then be compared with those of age- and sex-matched individuals. Coronary artery calcification is an indicator of atherosclerosis [7] and serves as an early warning sign of coronary artery disease. Primary care physicians can therefore use calcification scores to evaluate the risk of developing coronary artery disease [8; 9; 10]. Additionally, calcification can reflect disease progression or regression, and can therefore be quantified to assess treatment effectiveness. Previous research has indicated a robust association between coronary atherosclerotic burden and coronary heart and cardiovascular diseases [11; 12].  
Any intensity exceeding 130 Hounsfield units (HU) in a CT image is considered calcium [13]. However, intensities resulting from noise and artifacts can also exceed this threshold. Distinguishing artifacts from calcium is straightforward owing to their distinct patterns and shapes. By contrast, noise is random and can be challenging to distinguish from calcium; this determination relies on the subjective judgment of the assessor. Hence, the calcium score cannot be definitively attributed solely to calcium [14].  
Quantum noise, which contributes to the noise found in radiographic images, arises from increased radiation attenuation due to effective thickness [15; 16; 17]. Consequently, radiographic images of overweight and obese patients may exhibit Poisson noise, which may be quantified as calcium if its intensity surpasses 130 HU. Hence, the calcium score may be less accurate in overweight and obese patients than in patients of an average weight. Obesity is strongly correlated with coronary heart disease and cardiovascular risk factors; obese patients are therefore at a higher risk of coronary artery calcification [18; 19; 20; 21].  
Accurately discerning noise in images from overweight and obese patients is crucial for obtaining precise calcium scores. This study sought to confirm that an elevated BMI is associated with increased noise levels in CT images. Noise levels obtained from the CT scans of patients who were overweight and obese were compared with those of patients of a normal weight.