Effect of imaging parameters and clinical characteristics on pericoronary adipose tissue attenuation in patients without coronary plaque.

BACKGROUND: Pericoronary adipose tissue (PCAT) attenuation serves as a marker of coronary inflammation. However, numerous confounders may affect PCAT attenuation. This study aimed to investigate the influence of coronary computed tomography angiography (CCTA) imaging parameters and clinical characteristics on the fat attenuation index (FAI) of PCAT. METHODS: One hundred and ninety-six subjects [mean age ± standard deviation (SD), 55.4±9.5 years; 81 males] who underwent CCTA and had no coronary plaque were included in this retrospective study. Images were scanned at 100 or 120 kVp and reconstructed using two methods. PCAT attenuation was assessed using two measurement approaches: a proximal 40-mm segment of each coronary artery and a 10-mm segment in each coronary artery segment. The intraclass correlation coefficient (ICC) was used to assess interobserver agreement for FAI measurements. Linear regression analyses were performed to identify independent factors associated with FAI. RESULTS: Interobserver agreement for FAI measurements was excellent, with an ICC of 0.985-0.998; 120 kVp was independently associated with higher FAI values across the majority of segments (β=4.9-8.1, all P<0.001), except for FAI_RCA_mid_10mm and FAI_LCX_dist_10mm. The reconstruction method Iterative Model Reconstruction (IMR; level 1) with Cardiac Routine yielded significantly lower FAI than iDose4 (level 5) with Xres Standard in FAI_RCA_40mm, FAI_LAD_40mm, FAI_LAD_mid_10mm, and FAI_LCX_prox_10mm (β=-3.0 to -2.2, all P<0.05). Sex (male vs. female) was independently associated with FAI_LCX_dist_10mm (β=-3.7, P=0.032). Body mass index (BMI) ≥24 kg/m2 was associated with lower FAI_LAD_40mm, FAI_LAD_prox_10mm, and FAI_LAD_dist_10mm (β=-3.4 to -2.4, all P<0.05). Diabetes was negatively associated with FAI_LAD_prox_10mm (β=-3.9, P=0.030). Smoking was a positive predictor for FAI_RCA_40mm, FAI_LAD_40mm, FAI_RCA_mid_10mm, FAI_LAD_prox_10mm, and FAI_LCX_dist_10mm (β=4.1-6.5, all P<0.05). Dyslipidemia showed a negative association with FAI_LAD_40mm, FAI_RCA_dist_10mm, and FAI_LCX_prox_10mm (β=-3.9 to -2.5, all P<0.05). Other factors, including vessel attenuation, age, hypertension, and family history of coronary artery disease (CAD), showed no significant associations. CONCLUSIONS: In patients without coronary plaque, PCAT attenuation depends on imaging parameters and clinical characteristics, underscoring the importance of considering both imaging and clinical factors when interpreting FAI measurements.