Radiation Dose Reduction in Computed Tomography-Guided Lung Interventions using an Iterative Reconstruction Technique

Abstract

Purpose: To compare the radiation doses and image qualities of computed tomography (CT)-guided interventions using a standard-dose CT (SDCT) protocol with filtered back projection and a low-dose CT (LDCT) protocol with both filtered back projection and iterative reconstruction.

Materials and Methods: Image quality and radiation doses (dose-length product and CT dose index) were retrospectively reviewed for 130 patients who underwent CT-guided lung interventions. SDCT at 120 kVp and automatic mA modulation and LDCT at 100 kVp and a fixed exposure were each performed for 65 patients. Image quality was objectively evaluated as the contrast-to-noise ratio and subjectively by two radiologists for noise impression, sharpness, artifacts and diagnostic acceptability on a four-point scale.

Results: The groups did not significantly differ in terms of diagnostic acceptability and complication rate. LDCT yielded a median 68.6 % reduction in the radiation dose relative to SDCT. In the LDCT group, iterative reconstruction was superior to filtered back projection in terms of noise reduction and subjective image quality. The groups did not differ in terms of beam hardening artifacts.

Conclusion: LDCT was feasible for all procedures and yielded a more than two-thirds reduction in radiation exposure while maintaining overall diagnostic acceptability, safety and precision. The iterative reconstruction algorithm is preferable according to the objective and subjective image quality analyses.

Key Points:

• Implementation of a low-dose computed tomography (LDCT) protocol for lung interventions is feasible and safe.

• LDCT protocols yield a significant reduction (more than 2/3) in radiation exposure.

• Iterative reconstruction algorithms considerably improve the image quality in LDCT protocols.

Citation Format:

• Chang DH, Hiss S, Mueller D et al. Radiation Dose Reduction in Computed Tomography-Guided Lung Interventions using an Iterative Reconstruction Technique. Fortschr Röntgenstr 2015; 187: 906 – 914

Zusammenfassung

Ziel: Vergleich der Dosis und Bildqualität bei CT-gesteuerten Interventionen unter Verwendung eines Standarddosisprotokolls (SDCT) mit gefilterter Rückprojektion (FBP) und eines Niedrigdosisprotokolls (LDCT) mit FBP und iterativer Rekonstruktion (IR).

Material und Methoden: Retrospektiv wurde die Bildqualität und Strahlendosis (Dosislängenprodukt und CTDI) bei 130 Patienten, die sich einer CT-gesteuerten Lungenintervention unterzogen ausgewertet. SDCT wurde bei 65 Patienten mit einer automatischen Dosismodulation und 120 kVp, LDCT bei 65 Patienten mit einer fixierten mAs und 100 kVp durchgeführt. Die Bildqualität wurde objektiv mittels Kontrast-zu-Rausch-Verhältnis sowie subjektiv anhand einer 4-Punkte-Skala von zwei Radiologen bezüglich Bildrauschen, Schärfe, Artefakte und diagnostische Akzeptanz bewertet.

Ergebnisse: Es gab keine signifikanten Unterschiede bezüglich der diagnostischen Akzeptanz und der Komplikationsrate in beiden Gruppen. Im Vergleich zu SDCT erreichte LDCT eine Dosisreduktion im Median um 68,6 %. Die Implementation der iterativen Rekonstruktion war bezüglich der Rauschunterdrückung und der subjektiven Bildqualität der FBP überlegen. Bezüglich der Aufhärtungsartefakte ergab sich kein Unterschied zwischen beiden Gruppen.

Schlussfolgerung: Das LDCT-Protokoll erzielt eine signifikante Reduktion der Strahlenexposition um mehr als 2/3, während die diagnostische Sicherheit und Präzision beibehalten werden. Die iterative Rekonstruktion ist, aus der Analyse der objektiven und subjektiven Auswertung der Bildqualität zu bevorzugen.

Kernaussagen:

• Niedrigdosisprotokolle (LDCT) sind bei CT-gesteuerten Interventionen an der Lunge bezüglich diagnostischer Akzeptanz, Sicherheit und Präzision gut durchführbar.

• Die Verwendung von LDCT zeigt in unserer Studie eine Reduktion der Strahlendosis um mehr als 2/3 im Vergleich zu einem Standarddosisprotokoll.

• Die Implementation iterativer Rekonstruktionsalgorithmen bei LDCT verbessert die objektive und subjektive Bildqualität.

Key words

thorax - biopsy - CT - interventional procedures - image manipulation/reconstruction

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