For the diagnosis of subsegmental pulmonary emboli at multi-detector row CT, the use of 1-mm section widths results in substantially higher detection rates and greater agreement between different readers than the use of thicker sections.

To achieve high image quality, the heart rate should be sufficiently slow. Selection of appropriate trigger delays and a decreasing heart rate are effective to reduce cardiac motion artifacts.

Rationale and Objectives CT section thickness and reconstruction kernel each influence CT measurements of emphysema. This study was performed to assess whether their effects are related to the magnitude of the measurement. Materials and Methods Low-radiation-dose multidetector CT was performed in 21 subjects representing a wide range of emphysema severity. Images were reconstructed using 20 different combinations of section thickness and reconstruction kernel. Emphysema index values were determined as the percentage of lung pixels having attenuation lower than multiple thresholds ranging from −960 HU to −890 HU. The index values obtained from the different thickness-kernel combinations were compared by repeated measures ANOVA and Bland-Altman plots of mean vs. difference, and correlated with quantitative histology (mean linear intercept, Lm) in a subset of resected lung specimens. Results The effects of section thickness and reconstruction kernel on the emphysema index were significant (p<0.001) and diminished as the index threshold was raised. The changes in index values due to changing the thickness-kernel combination were largest for subjects with intermediate index values (10–30%), and became progressively smaller for those with lower and higher index values. This pattern was consistent regardless of the thickness-kernel combinations compared and the HU threshold used. Correlations between the emphysema index values obtained with each thickness-kernel combination and Lm ranged from r=0.55–0.68 (p=0.007–0.03). Conclusion The effects of CT section thickness and kernel on emphysema index values varied systematically with the magnitude of the emphysema index. All reconstruction techniques provided significant correlations with quantitative histology.

The mass measurement is more accurate, less variable, and more reproducible in coronary calcium quantification than are measurements with other algorithms. Accurate quantification of calcium in each calcified plaque may require that the threshold be set individually, depending on the calcium density.

Use of the mass quantification algorithm in combination with a calibration phantom allows accurate quantification of coronary calcium. Measurements of calcium mass obtained at 1.25-mm section width CT angiography have the best agreement with those obtained at the traditional 3-mm section width imaging protocol.

The injection of approximately 1 g iodine/s resulted in an optimal (250-300 HU) contrast enhancement for cardiac 4-detector-row computed tomography.

No abstract

The authors investigated the contrast enhancement characteristics of the coronary artery stent lumen to assess patency and then evaluated the accuracy of computed tomographic (CT) measurement of the in-stent luminal diameter. Nineteen patients (16 men and three women; mean age, 58.7 years) with 26 stents underwent cardiac-gated CT angiography with a 16-detector row scanner 1-3 weeks after stent placement. CT images depicted the lumina of 20 stents in 14 patients. CT attenuation measured in the treated lumen was higher than, and correlated highly (r >/= 0.87) with, attenuation in the proximal and distal untreated lumen. Estimated values for in-stent luminal diameter were lower with CT than with conventional angiography (P <.001), and the mean error (16.1%) that resulted from estimation based on sharp-kernel CT images was significantly smaller than that (27.3%) from estimation based on medium-smooth-kernel CT images (P <.001). Visualization of the in-stent lumen at CT angiography with a 16-detector row scanner allows assessment of coronary artery stent patency on the basis of measured contrast enhancement.