Diagnosis of Pulmonary Artery Embolism: Comparison of Single-Source CT and 3^rd Generation Dual-Source CT using a Dual-Energy Protocol Regarding Image Quality and Radiation Dose

Abstract

Purpose To compare radiation dose, subjective and objective image quality of 3 rd generation dual-source CT (DSCT) and dual-energy CT (DECT) with conventional 64-slice single-source CT (SSCT) for pulmonary CTA.

Materials and Methods 180 pulmonary CTA studies were performed in three patient cohorts of 60 patients each. Group 1: conventional SSCT 120 kV (ref.); group 2: single-energy DSCT 100 kV (ref.); group 3: DECT 90/Sn150 kV. CTDIvol, DLP, effective radiation dose were reported, and CT attenuation (HU) was measured on three central and peripheral levels. The signal-to-noise-ratio (SNR) and contrast-to-noise-ratio (CNR) were calculated. Two readers assessed subjective image quality according to a five-point scale.

Results Mean CTDIvol and DLP were significantly lower in the dual-energy group compared to the SSCT group (p < 0.001 [CTDIvol]; p < 0.001 [DLP]) and the DSCT group (p = 0.003 [CTDIvol]; p = 0.003 [DLP]), respectively. The effective dose in the DECT group was 2.79 ± 0.95 mSv and significantly smaller than in the SSCT group (4.60 ± 1.68 mSv, p < 0.001) and the DSCT group (4.24 ± 2.69 mSv, p = 0.003). The SNR and CNR were significantly higher in the DSCT group (p < 0.001). Subjective image quality did not differ significantly among the three protocols and was rated good to excellent in 75 % (135/180) of cases with an inter-observer agreement of 80 %.

Conclusion Dual-energy pulmonary CTA protocols of 3 rd generation dual-source scanners allow for significant reduction of radiation dose while providing excellent image quality and potential additional information by means of perfusion maps.

Key Points:

• Dual-energy CT with 90/Sn150 kV configuration allows for significant dose reduction in pulmonary CTA.

• Subjective image quality was similar among the three evaluated CT-protocols (64-slice SSCT, single-energy DSCT, 90/Sn150 kV DECT) and was rated good to excellent in 75% of cases.

• Dual-energy CT provides potential additional information by means of iodine distribution maps.

Citation Format

• Petritsch B, Kosmala A, Gassenmaier T et al. Diagnosis of Pulmonary Artery Embolism: Comparison of Single-Source CT and 3rd Generation Dual-Source CT using a Dual-Energy Protocol Regarding Image Quality and Radiation Dose. Fortschr Röntgenstr 2017; 189: 527 – 536

Zusammenfassung

Ziel Das Potential der Dritt-Generation Dual-Source CT (DSCT) in der Lungenemboliediagnostik wurde bis dato noch nicht ausführlich untersucht. Ziel dieser Studie war es, Strahlendosisparameter sowie subjektive und objektive Bildqualität des aktuellsten DSCT Scanners im Single-Energy und Dual-Energy (DE) Modus mit einem herkömmlichen pulmonalen Standard CTA Protokoll am 64-Zeilen CT (SSCT) zu vergleichen.

Material und Methoden Es wurden insgesamt 180 pulmonale CTA Studien in drei Patientengruppen mit jeweils 60 Patienten durchgeführt. 1. Gruppe: konventionelle 120 kV (ref.) 64-Zeilen SSCT; 2. Gruppe: 100 kV (ref.) Single-Energy DSCT; 3. Gruppe: 90/Sn150 kV DECT. Dosisparameter (CTDIvol, DLP, effektive Dosis) wurden evaluiert und die CT Abschwächung (HU) wurde an jeweils drei zentralen bzw. peripheren Lokalisationen gemessen. Das Signal-Rausch-Verhältnis (SNR) und das Kontrast-Rausch-Verhältnis (CNR) wurden berechnet. Die subjektive Bildqualität wurde von zwei Readern ausgewertet (5-Punkte Skala).

Ergebnisse CTDIvol und DLP waren in der DECT Gruppe jeweils signifikant niedriger als in der SSCT Gruppe (p < 0,001 [CTDIvol]; p < 0,001 [DLP]) und der DSCT Gruppe (p = 0,003 [CTDIvol]; p = 0,003 [DLP]). Die effektive Dosis war mit 2,79 ± 0,95 mSv in der DECT Gruppe signifikant geringer als in der SSCT Gruppe (4,60 ± 1,68 mSv, p < 0,001) und der DSCT Gruppe (4,24 ± 2,69 mSv, p = 0,003). SNR und CNR waren in der DSCT Gruppe signifikant höher (p < 0,001). Die subjektive Bildqualität der drei Protokolle war vergleichbar und wurde in 75 % der Fälle (135/180) als gut bzw. sehr gut bewertet mit einer Interobserver-Variabilität von 80 %.

Schlussfolgerung Die Verwendung von Dual-Energy Protokollen in der pulmonalen CTA an Dritt-Generation Dual-Source CT Scannern erlaubt eine signifikante Dosisreduktion bei erhaltener exzellenter Bildqualität und potentieller zusätzlicher Information im Sinne von Perfusions-Karten.

Kernaussagen:

• Die Verwendung von 90/Sn150 kV Dual-Energy CT-Protokollen erlaubt eine signifikante Dosisreduktion in der pulmonalen CTA.

• Die subjektive Bildqualität aller drei untersuchten CT-Protokolle (64-Zeilen SSCT, Single-Energy DSCT, 90/Sn150 kV DECT) war vergleichbar und wurde in 75 % der Fälle als gut bzw. sehr gut bewertet.

• Die Dual-Energy CT bietet potentiell zusätzliche Informationen durch die Erstellung von farbcodierten Jod-Karten.

Key words

pulmonary angiography - radiation dose - image quality - dual-source - dual-energy - pulmonary embolism

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