Relationship between chest lateral width, tube current, image noise, and radiation exposure associated with coronary artery calcium scanning on 320-detector row CT.

BACKGROUND: The relationship between chest lateral width, tube current, image noise, and radiation exposure on 320-detector row CT has not been reported. OBJECTIVE: We investigated the relationships between chest lateral width, estimated radiation exposure (DLPe), and image noise in 300 patients undergoing clinical coronary calcium scanning. METHODS: Patients undergoing coronary calcium scanning with 320-detector row CT (prospective, volumetric mode, 120 kV of tube voltage, 100-550 mA of tube current, 0.5-mm detector width) were grouped by chest lateral width (small, medium, and large) from anteroposterior topograms and 100 consecutive patients were selected from each group (n = 300). Tube current, DLPe, and noise were compared among groups with Kruskal-Wallis or one-way ANOVA. Phantom experiments were performed to evaluate the accuracy of calcium quantification as a function of size and tube current. RESULTS: Median tube current in small, medium, and large patients was 130, 200, and 250 mA, respectively (P < 0.0001). Despite the use of higher tube current settings, noise levels also increased with size (20.2 ± 4.5 HU, 22.0 ± 3.9 HU, and 25.1 ± 4.9 HU, respectively; global P < 0.001). DLPe was significantly higher with increasing size (54, 83, and 104 mGy · cm, respectively; P < 0.0001). Phantom experiments showed that 50-100 mA, 150-200 mA, and approximately 300 mA in small, medium, and large phantoms were associated with stable estimate of calcium. CONCLUSIONS: Increasing chest lateral width is associated with increasing radiation exposure and image noise. The use of 50-100 mA in small and 150-200 mA in medium patients is associated with acceptable noise and stable estimate of coronary artery calcium. In large patients, precise identification of individual calcified lesions remains difficult despite increasing tube current and radiation exposure.

Circulating Chlamydia pneumoniae DNA and advanced coronary artery disease.

BACKGROUND: Chlamydia pneumoniae (C. pneumoniae) has been linked to atherosclerosis. Detection of this pathogen in peripheral blood cells may be valuable in the diagnosis of disease state. This study aimed to evaluate the prevalence of circulating C. pneumoniae DNA and its relationship with severity and extent of coronary artery disease (CAD). METHODS: Blood samples from 269 patients undergoing coronary angiography were collected. The presence of circulating C. pneumoniae DNA was determined by real-time PCR assay. Data regarding coronary risk factors and severity and extent of CAD were collected. Severity and extent of CAD was defined by the number of major epicardial coronary arteries with >50% stenosis and by the Duke jeopardy score. RESULTS: Sixteen of 269 specimens (5.9%) from the study cohort were positive for C. pneumoniae DNA. Thirteen specimens among 149 samples from patients with multi-vessel disease (8.7%) were positive for C. pneumoniae DNA compared with 3 of 120 (2.5%) among patients without multi-vessel CAD. The prevalence of circulating C. pneumoniae DNA was significantly associated with multi-vessel disease. The odds ratio was 5.1 (P=0.02) after adjustment for conventional risk factors. CONCLUSIONS: Presence of circulating C. pneumoniae DNA is associated with advanced CAD, suggesting C. pneumoniae infection as a contributing factor to progression of coronary atherosclerosis.