Martin Seltmann

Detection of Coronary Artery Stenoses by Low-Dose, Prospectively ECG-Triggered, High-Pitch Spiral Coronary CT Angiography

OBJECTIVES We sought to evaluate the diagnostic accuracy of a new prospectively electrocardiogram (ECG)-triggered high-pitch scan mode for coronary computed tomography angiography (CTA), which allows an effective dose of less than 1 mSv. BACKGROUND Coronary CTA provides increasingly reliable image quality, but the associated radiation exposure can be high. METHODS Seventy-five patients with suspected coronary artery disease and in sinus rhythm were screened for participation. After exclusion of 25 patients for body weight >100 kg or failure to lower heart rate to ≤ 60 beats/min, 50 patients were studied by prospectively ECG-triggered high-pitch spiral computed tomography (CT). Coronary CTA was performed using a dual-source CT system with 2 × 128 × 0.6-mm collimation, 0.28-s rotation time, a pitch of 3.4, 100-kVp tube voltage, and current of 320 mA. Data acquisition was prospectively triggered at 60% of the R-R interval and completed within 1 cardiac cycle. Diagnostic accuracy for detection of coronary artery stenoses ≥ 50% diameter stenosis was determined by comparison to invasive coronary angiography. Per-patient diagnostic performance was the primary form of analysis. RESULTS In all 50 patients (34 males, 59 ± 12 years of age), imaging was successful. For the detection of 16 patients with at least 1 coronary artery stenosis, CT demonstrated a sensitivity of 100% (95% confidence interval [CI]: 79% to 100%) and specificity of 82% (95% CI: 65% to 93%). The positive predictive value was 72% (95% CI: 49% to 89%) and the negative predictive value was 100% (95% CI: 87% to 100%). Sensitivity was 100% (95% CI: 88% to 100%) and specificity was 94% (95% CI: 89% to 97%) on a per-vessel basis. Per-segment sensitivity was 92% (95% CI: 80% to 97%), and specificity was 98% (95% CI: 96% to 98%). Mean dose-length product for coronary CTA was 54 ± 6 mGy · cm, the effective dose was 0.76 ± 0.08 mSv (0.64 to 0.95 mSv). CONCLUSIONS In nonobese patients with a low and stable heart rate, prospectively ECG-triggered high-pitch spiral coronary CTA provides high diagnostic accuracy for the detection of coronary artery stenoses.

Quantification of non-calcified coronary atherosclerotic plaques with dual-source computed tomography: comparison with intravascular ultrasound

Background The quantification of non-calcified coronary plaques using multidetector computed tomography has not been extensively investigated. Objective To evaluate the ability of dual-source computed tomography (DSCT) to quantify non-calcified plaque volumes using intravascular ultrasound (IVUS) as the standard of reference. Methods The datasets of 70 patients with suspected or known coronary artery disease who underwent DSCT (330 ms gantry rotation, 2×64×0.6 mm collimation, 60–90 ml contrast agent) were analysed before invasive coronary angiography, with IVUS performed as part of the diagnostic procedure. 100 individual non-calcified coronary atherosclerotic plaques (one to three plaques per patient) with suitable fiducial markers were matched and selected for plaque volume measurements using manual segmentation. Only DSCT datasets with good or excellent image quality were considered for analysis. Results Intra and interobserver variability for plaque volume measurements by DSCT were 6±5% and 11±7%, respectively. Mean total plaque volume by DSCT was 89±66 mm3 (range 14–400 mm3). Mean total plaque volume by IVUS was 90±73 mm3 (range 16–409 mm3). The mean difference between DSCT and IVUS was 1±34 mm3 (range −131–85 mm3). Despite the good correlation for plaque volume measurements (r=0.89, p<0.001), agreement between the two methods was only modest (Bland–Altman limits of agreement −67 to +65 mm3). Conclusions Non-calcified plaque volumes as determined by DSCT yielded good correlation but only modest agreement in comparison with IVUS.

Influence of slice thickness and reconstruction kernel on the computed tomographic attenuation of coronary atherosclerotic plaque

BACKGROUND The computed tomographic (CT) attenuation of coronary atherosclerotic plaque has been proposed as a marker for tissue characterization and may thus potentially contribute to the assessment of plaque instability. OBJECTIVE We analyzed the influence of reconstruction parameters on CT attenuation measured within noncalcified coronary atherosclerotic lesions. METHODS Seventy-two patients were studied by contrast-enhanced dual-source CT coronary angiography (330 millisecond rotation time, 2 x 64 x 0.6 mm collimation, 120 kV, 400 mAs, 80 mL contrast agent intravenously at 6 mL/s), and a total of 100 distinct noncalcified coronary atherosclerotic plaques were identified. Image data sets were reconstructed with a soft (B20f), medium soft (B26f), and sharp (B46f) reconstruction kernel. With the medium soft kernel, image data sets were reconstructed with a slice thickness/increment of 0.6/0.3 mm, 0.75/0.4 mm, and 1.0/0.5mm. Within each plaque, CT attenuation was measured. RESULTS Mean CT attenuation using the medium soft kernel was 109 +/- 58 HU (range, -16 to 168 HU). Using the soft kernel, mean density was 113 +/- 57 HU (range, -13 to 169 HU), and using a sharp kernel, mean density was 97 +/- 49 HU (range, -23 to 131 HU). Similarly, reconstructed slice thickness had a significant influence on the measured CT attenuation (mean values for medium soft kernel: 102 +/- 52 HU versus 109 +/- 58 HU versus 113 +/- 57 HU for 0.6-mm, 0.75-mm, and 1.0-mm slice thickness). The differences between 0.75-mm and 0.6-mm slice thickness (P = 0.05) and between medium sharp and sharp kernels (P = 0.02) were statistically significant. CONCLUSIONS Image reconstruction significantly influences CT attenuation of noncalcified coronary atherosclerotic plaque. With decreasing spatial resolution (softer kernel or thicker slices), CT attenuation increases significantly. Using absolute CT attenuation values for plaque characterization may therefore be problematic.

Coronary vessel and luminal area measurement using dual-source computed tomography in comparison with intravascular ultrasound: effect of window settings on measurement accuracy.

Background: Image display settings (window and level) have a substantial impact on measurements of coronary artery and plaque dimensions in computed tomography (CT), and their influence on measurement accuracy has not been systematically evaluated. We analyzed the influence of window width/level settings on the accuracy for determining cross-sectional lumen and outer vessel diameters in contrast-enhanced CT angiography compared with intravascular ultrasound (IVUS). Methods: We evaluated the data sets of 35 patients. Coronary CT angiography was performed as part of a research protocol before invasive coronary angiography. A contrast-enhanced volume data set was acquired using a dual-source CT (DSCT) scanner (Siemens Healthcare, Forchheim, Germany). Intravascular ultrasound was performed using a 40-MHz IVUS catheter (Atlantis, Boston Scientific Corporation, Natick, Mass) and motorized pullback at 0.5 mm/s. One hundred exactly corresponding sites within the coronary artery system were identified in both DSCT and IVUS using bifurcation points as fiducial markers. In DSCT data sets, multiplanar reconstructions (0.75-mm slice thickness) were rendered orthogonally to the centerline of the coronary artery at each of the 100 sites. Computed tomographic images were displayed using 4 previously published settings (700/200, 700/140, and 500/150 Hounsfield units [HU], and 1 HU/65% of the mean luminal intensity [HU] and 155%/65% of the mean luminal intensity [HU] for window width/level) as well as with a visually adjusted setting for subjectively optimal lumen and outer vessel area measurement. Coronary lumen and cross-sectional vessel areas were manually traced using all 5 display settings and compared with IVUS measurements. Results: Concerning cross-sectional vessel area measurements, correlation was close and significant compared with IVUS using all settings (r ≥ 0.93, P = 0.01 for all settings). Bland-Altman analysis revealed a good agreement between both modalities with a systematic bias toward overestimation in CT. Least bias was demonstrated using the setting 155%/65% of the mean luminal intensity for window width/level, with a mean (SD) difference of 0.2 (1.73) mm2. For the measurement of the luminal area, the window setting using a width of 1 HU and a level of 65% of the mean luminal intensity showed the lowest correlation to IVUS (r = 0.85), with a systematic bias toward underestimation of the lumen in CT. Bland-Altman analysis revealed a moderate agreement with a mean (SD) difference of −2.1 (1.6) mm2. For all other settings, a very close correlation was observed (r > 0.9, P = 0.01), and Bland-Altman analysis revealed a slight trend toward lumen underestimation in CT, yet with a good agreement. The least bias was demonstrated using the setting 700/200 HU for window width/level with a mean (SD) difference of −0.1 (0.9) mm2. Conclusion: Previously published window settings and visually adjusted window setting correlate very well with IVUS measurements regarding coronary artery cross-sectional and luminal area, with a better agreement for luminal area measurements. A systematic bias toward overestimation of vessel area in CT was observed as well as a slight trend toward lumen underestimation. This bias was least for vessel area measurement using 155%/65% of the mean luminal intensity (HU) for window width/level, whereas for luminal area measurement, the setting 700/200 HU for window width/level yielded the least bias.

Left ventricular thrombus attenuation characterization in cardiac computed tomography angiography.

BACKGROUND Because of their similar visual appearance, differentiation of left ventricular thrombotic material and myocardial wall can be difficult in contrast-enhanced coronary computed tomography (CT) angiography. OBJECTIVE We identified typical thrombi attenuation of left ventricular thrombi with the use of CT measurement. METHODS Over a time period of 6 years, we retrospectively identified 31 patients who showed a left ventricular thrombus in CT angiography datasets. Patients underwent routine contrast cardiac CT to investigate coronary artery disease. CT attenuation of each thrombus was assessed in the 4-chamber view. CT densities were also determined in the ascending aorta, left ventricle, and myocardial wall both in the mid-septal and mid-lateral segments. The mean CT attenuation of thrombi and the difference between attenuation in thrombi, left ventricular cavity, and myocardial wall were determined. The ratio of attenuation values in thrombus versus aorta and myocardium versus aorta were also determined. RESULTS Mean (±SD) CT attenuation of all left ventricular thrombi in 31 patients was 43.2 ± 15.3 HU (range, 25-80 HU). Mean CT densities of septal and lateral myocardial wall were 102.9 ± 23.1 HU (range, 63-155 HU) and 99.3 ± 28.7 HU (range, 72-191 HU), respectively, and were thus significantly higher than the CT attenuation of thrombi (P < 0.001). A threshold of 65 HU yielded a sensitivity, specificity, and positive and negative predictive values of 94%, 97%, 94%, and 97%, respectively, to differentiate thrombus from the myocardial wall. The mean ratio between CT attenuation of thrombus and CT attenuation within the ascending aorta was 0.11 ± 0.05 (range, 0.04-0.23), which was significantly lower compared with the mean ratio between CT attenuation of the myocardial wall and the CT attenuation within the ascending aorta. CONCLUSION CT attenuation within left ventricular thrombi was significantly lower than myocardial attenuation in CT angiography datasets. Assessment of CT attenuation may contribute to the differentiation of thrombi.

Myocardial viability by dual-energy delayed enhancement computed tomography

A 77-year-old male presented with an inferior ST-segment elevation myocardial infarction. Coronary angiography revealed thrombotic occlusion of the right coronary artery ([Fig. 1][1]). Percutaneous intervention was unsuccessful, and imaging was requested to determine suitability for surgical

Ventricular septal rupture and right ventricular intramyocardial dissection secondary to acute inferior myocardial infarction

A 61-year-old female patient presented with sub acute myocardial infarction with an occluded right coronary artery on invasive evaluation and a ventricular septal rupture on echocardiogram. Cardiac computed tomography (CT) was performed to better define the septal anatomy. As the anatomy on cardiac CT was considered unfavorable for percutaneous intervention, the patient underwent successful surgical repair.

Suture-induced right coronary artery stenosis.

An 82-year-old patient developed right heart failure in the days after surgical aortic valve replacement. Coronary CT angiography showed a high-grade stenosis of the mid-right coronary artery. Adjacent suture material seen on noncontrast CT suggested that the lesion was related to surgical closure of the right atrial cannulation site. Invasive angiography confirmed the stenosis, and percutaneous intervention was successfully performed.

Calcified right intraventricular thrombus in a patient with systemic lupus erythematous and antiphospholipid syndrome

A 37-year-old patient with known systemic lupus erythematous, antiphospholipid syndrome and previous pulmonary embolism presented with non-ST elevation myocardial infarction while on adequate anticoagulation therapy. The patient was further evaluated with cardiac computed tomography. A small diagonal branch occlusion was the only coronary lesion present. A partially calcified right ventricular thrombus was incidentally found. Because of the small vessel size, cardiac catheterization was deemed unnecessary, and the patient was discharged with adjustment of immunosuppressive therapy and anticoagulation.