High-Pitch Computed Tomography Coronary Angiography—A New Dose-Saving Algorithm: Estimation of Radiation Exposure

Purpose. To estimate effective dose and organ equivalent doses of prospective ECG-triggered high-pitch CTCA. Materials and Methods. For dose measurements, an Alderson-Rando phantom equipped with thermoluminescent dosimeters was used. The effective dose was calculated according to ICRP 103. Exposure was performed on a second-generation dual-source scanner (SOMATOM Definition Flash, Siemens Medical Solutions, Germany). The following scan parameters were used: 320 mAs per rotation, 100 and 120 kV, pitch 3.4 for prospectively ECG-triggered high-pitch CTCA, scan range of 13.5 cm, collimation 64 × 2 × 0.6 mm with z-flying focal spot, gantry rotation time 280 ms, and simulated heart rate of 60 beats per minute. Results. Depending on the applied tube potential, the effective whole-body dose of the cardiac scan ranged from 1.1 mSv to 1.6 mSv and from 1.2 to 1.8 mSv for males and females, respectively. The radiosensitive breast tissue in the range of the primary beam caused an increased female-specific effective dose of 8.6%±0.3% compared to males. Decreasing the tube potential, a significant reduction of the effective dose of 35.8% and 36.0% can be achieved for males and females, respectively (P < 0.001). Conclusion. The radiologist and the CT technician should be aware of this new dose-saving strategy to keep the radiation exposure as low as reasonablly achievable

CT-Angiographie der Koronarien mittels Dual Source Computertomographie bei 170 Patienten

Introduction: In preliminary studies DSCT provides robust image quality over a wide range of heart rates and excludes CAD with high accuracy. The aim of the present study was to evaluate the reproducibility of these results in a large, unselected and consecutive group of patients scheduled for invasive coronary angiography (ICA). Material and methods: 170 patients (124 men, 46 women; mean age: 63.6±9.4 years) with known CAD (101 patients) or suspected CAD (69 patients) scheduled for ICA were examined by coronary CTA prior to ICA. All coronary segments were assessed for image quality (1: excellent; 5: non-diagnostic). The presence of significant vessel stenosis (> 50%) was calculated using ICA as standard of reference. Results: A total of 680 vessels were analyzed. Despite of 45 arrythmic patients all analyzed coronary segments were diagnostically evaluable. Mean Agatston score equivalent was 686 (range 0–4950). ICA revealed 364 lesions with &#8805;50% diameter stenosis. DSCT correctly identified 336 of these lesions. 115 lesions with a diameter stenosis < 50% were overestimated by DSCT and thus considered as false-positive findings. On a per-segment basis, sensitivity was 92%, specificity 93%, positive predictive value (PPV) was 75% and negative predictive value (NPV) 98%. On a per-vessel basis DSCT revealed a sensitivity of 93%, a specificity of 88%, a PPV of 78% and a NPV of 97%. On a per-patient basis sensitivity was 94%, specificity 79%, PPV 88% and NPV 90%. Discussion: Initial results of preliminary studies showing robust image quality and high accuracy in DSCT cardiac imaging could be approved with the present study enclosing a large consecutive population. However severe coronary calcifications and irregular heart rate still remain limiting factors for coronary CTA. Conclusions: Despite improved image quality and high accuracy of coronary DSCT angiography, proof of indication is necessary, due to still remaining limiting factors.Einleitung: Bereits in Vorstudien konnte die Dual Source Computertomographie eine robuste Bildqualität in einem breiten Herzfrequenzbereich aufweisen und die Koronare Herzkrankheit (KHK) mit einer hohen diagnostischen Genauigkeit ausschliessen. Das Ziel der vorliegenden Arbeit war die Reproduzierbarkeit dieser Ergebnisse in einem großen, unselektierten Patientenkollektiv, welches für eine invasive Koronarangiographie terminiert war, zu untersuchen. Material und Methoden: 170 Patienten (124 männlich, 46 weiblich) mit einem Durchschnittsalter von 63,6 ± 9,4 Jahren mit bekannter (101 Patienten) oder vermuteter KHK (69 Patienten) wurden zusätzlich, vor der geplanten invasiven Koronarangiographie, mittels Dual Source CT Angiographie untersucht. Die Bildqualität aller Koronarsegmente wurde bewertet (1: exzellent; 5: nicht-diagnostisch). Des Weiteren wurde die diagnostische Genauigkeit bezüglich erkannter signifikanter Gefäßstenosen (groesser gleich 50%) im Vergleich zur invasiven Koronarangiographie bestimmt. Ergebnisse: 680 Koronargefäße wurden untersucht. Trotz 45 Patienten mit arrhythmischen Herzfrequenzen während der Untersuchung waren alle Koronarsegmente diagnostisch auswertbar. Das mittlere Agatston Score Äquivalent betrug 686 (Spannweite 0 – 4950). Mittels invasiver Koronarangiographie konnten 364 Läsionen mit einer Gefäßstenose groesser gleich 50% nachgewiesen werden. 336 dieser Läsionen wurden ebenfalls mittels DSCT erkannt. Allerdings wurden 115 Läsionen mit einer Gefäßstenose < 50% mittels DSCT überbewertet und somit als falsch-positive Befunde gewertet. Bei einer segmentbasierten Auswertung betrug die Sensitivität 92%, die Spezifität 93%, der positive prädiktive Wert (PPV) 75% und der negative prädiktive Wert (NPV) 98%. Bei der Auswertung auf Gefäßbasis lag die Sensitivität der DSCT bei 93%, die Spezifität bei 88%, der PPV bei 78% und der NPV bei 97%, respektive ergaben sich bei der patientenbasierten Auswertung eine Sensitivität von 94%, eine Spezifität von 79%, ein PPV von 88% und ein NPV von 90%. Diskussion: Die in Voruntersuchungen erzielten Ergebnisse der DSCT, welche eine robuste Bildqualität und eine hohe diagnostische Genauigkeit in der kardialen Bildgebung lieferten, konnten in der vorliegenden Arbeit in einem großen, unselektierten Patientenkollektiv bestätigt werden. Jedoch verbleiben starke Kalzifizierungen der Gefäßwand sowie Herzrhythmusstörungen limitierende Faktoren der CT Koronarangiographie, weshalb weiterhin eine strenge Indikationsprüfung erfolgen sollte

Forensic age estimation in living adolescents with CT imaging of the clavicula-impact of low-dose scanning on readers' confidence

OBJECTIVES: Computed tomography (CT) imaging of the clavicula displays the reference standard for forensic bone age diagnostics in adolescents and young adults. Consequently, highest efforts on radiation reduction are warranted. Therefore, the aim of this study was to investigate the feasibility of low-dose (LD) CT imaging of the clavicula for age estimation in living adolescents. METHODS: A total of 207 non-contrast chest CT of 144 patients born between 1988 and 2012, performed in 2018 due to various clinical indications, were included in this retrospective study. The mean patient age was 16.9 ± 6.6 years. Patients were divided into a LD (n = 146) and standard-dose (SD; n = 61) group. Image quality, confidence levels, and ossification stages (using the 5-stage classification including the subgroups 2a–3c) were assessed by two radiologists independently. Radiation dose was determined via dosimetry software. RESULTS: Dose simulation with z-axis reduction to depict the clavicula only resulted in a median exposure of 0.1 mSv (IQR: 0.0) in LD compared with 0.9 mSv (IQR: 0.6) in SD (p < 0.001). The median image quality was rated by both readers significantly worse in LD compared with SD on a Likert scale ranging from 1 to 4 with a median of 3 (IQR: 1) versus 4 (IQR: 0; p < 0.001 for both readers). There was an almost perfect agreement for the ossification stages between both readers with a Cohen’s kappa of 0.83 (p < 0.001). Median confidence levels of both readers were not significantly different between LD and SD in the decisive subgroups 2a–3c. CONCLUSIONS: Low-dose CT imaging of the clavicula for age estimation in living adolescents is possible without loss of readers’ confidence. KEY POINTS: • Radiological bone age diagnostics in young delinquents with unknown exact chronological age is important as the judicial systems differentiate between youths and adults. • Low-dose computed tomography scanning of the medial clavicular joint for forensic age estimation is feasible in living adolescents without loss of readers’ confidence. • Sufficient image quality of the medial clavicular joint for forensic bone age diagnostics in living adolescents is achievable using a median dose of 0.1 mSv

Evaluation of Computer-Assisted Quantification of Carotid Artery Stenosis

The purpose of this study was to evaluate the influence of advanced software assistance on the assessment of carotid artery stenosis; particularly, the inter-observer variability of readers with different level of experience is to be investigated. Forty patients with suspected carotid artery stenosis received head and neck dual-energy CT angiography as part of their pre-interventional workup. Four blinded readers with different levels of experience performed standard imaging interpretation. At least 1 day later, they performed quantification using an advanced vessel analysis software including automatic dual-energy bone and hard plaque removal, automatic and semiautomatic vessel segmentation, as well as creation of curved planar reformation. Results were evaluated for the reproducibility of stenosis quantification of different readers by calculating the kappa and correlation values. Consensus reading of the two most experienced readers was used as the standard of reference. For standard imaging interpretation, experienced readers reached very good (k = 0.85) and good (k = 0.78) inter-observer variability. Inexperienced readers achieved moderate (k = 0.6) and fair (k = 0.24) results. Sensitivity values 80%, 91%, 83%, 77% and specificity values 100%, 84%, 82%, 53% were achieved for significant area stenosis >70%. For grading using advanced vessel analysis software, all readers achieved good inter-observer variability (k = 0.77, 0.72, 0.71, and 0.77). Specificity values of 97%, 95%, 95%, 93% and sensitivity values of 84%, 78%, 86%, 92% were achieved. In conclusion, when supported by advanced vessel analysis software, experienced readers are able to achieve good reproducibility. Even inexperienced readers are able to achieve good results in the assessment of carotid artery stenosis when using advanced vessel analysis software