Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz

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Gewählte Publikation:

Nagy, E.
Optimization of contrast agent application protocols in pediatric thoracic computer tomography.
Doktoratsstudium der Medizinischen Wissenschaft; Humanmedizin; [ Dissertation ] Graz Medical University; 2020. pp. 87 [OPEN ACCESS]


Autor*innen der Med Uni Graz:
Kalmar Peter
Pfleger Andreas
Sorantin Erich

Background and Purpose: Computed tomography angiography (CTA) is a challenging task in young children. Bolus tracking is generally advised for contrast agent (CA) timing to ensure optimal image quality. The adaption of automated bolus tracking (ABT) thresholds to different tube voltages is reasonable. However, a clear methodology to achieve the adapted ABT thresholds with the maintenance of image quality is scarce. Several variants of CA application protocols are well established in the daily routine; however, a direct head to head comparison of their applicability in the pediatric routine is missing. This work aimed to provide a transparent approach to ABT threshold calculation, as well as ABT threshold values for everyday use based on phantom measurements. Furthermore, it aimed to compare different CA application protocols for cardiothoracic CTA regarding image quality and CA iodine volume in children younger than two years of age. Methods: Phantom measurements were conducted on an Electron Density Phantom with tissue-mimicking materials at every available tube voltages of three different CT scanners. ABT thresholds were calculated by curve fitting models using linear regression. Additionally, retrospective analysis of 70 cardiothoracic CTA scans of young children (<2 years) were performed to compare three different CA application protocols: the so-called “microbolus technique” (MBT), a conventional dual-phase protocol and one with empirical bolus delay. Furthermore, an assessment of objective and subjective image quality was performed as well. Results: ABT thresholds were calculated at different kV settings and reference thresholds with minimal differences between the CT scanners in this regard. Bland-Altman analysis ruled out any systemic inter-scanner bias. As for CA application protocols, significantly lower CA volume was applied using the MBT protocol as well as consecutively less CA-related artifacts and better image quality were achieved with the MBT. Conclusions: The adaptation of bolus tracking threshold is essential in thoracic CTA. Using the provided method for ABT threshold calculation, a difference up to 45% might occur between ABT thresholds at 120 kV and 70 kV. Furthermore, the examined CA application protocols showed comparable performance. With the MBT a slightly better image quality was achieved using less CA volume.

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