Challenges in Computed Tomography of the Head – Achieving Diagnostic Quality while Adhering to New Dose Level References

Congress:

EuroSafe Imaging 2019

Poster Number:

ESI-0085

Type:

EuroSafe Imaging

Keywords:

Action 2 - Clinical diagnostic reference levels (DRLs), Action 3 - Image quality assessment based on clinical indications, Head and neck, CT, Technical aspects, Safety, Quality assurance, Dosimetric comparison

Authors:

T. D. Do, K. Graf, R. Mueller, T. Mokry, T. F. Weber, W. Stiller, H. U. Kauczor

DOI:

10.26044/esi2019/ESI-0085

DOI-Link:

https://dx.doi.org/10.26044/esi2019/ESI-0085

Fig. 1: Head support shells. Attachable head shell in extension to the scanner table...

Fig. 2: Effects of cervical spine angulation. Different scans of the same patient with...

Fig. 3: Bismuth eye shield shown on an axial scan (A). Head CT dose of the same patient...

Fig. 4: Comparison of standard Filtered Back Projection (sFBP: A), hybrid iterative...

Background/introduction

The new dose level references were released by the German Federal Office for Radiation Protection in June 2016 including for a routine head CT. The dose level references for the adult brain were drastically reduced, i.e. the CTDIvol from 65 mGy to 60 mGy and DLP from 950 mGy*cm to 850 mGy*cm (1).The new levels are derived from the 75th percentile of the distribution of patients’ expositions from a large number of operators with CT equipment nationwide since the last update in 2010. Moreover, there...

Description of activity and work performed

Head support shells Studies in anthropomorphic phantoms have shown that a gantry tilt approximately reduces the lens dose for 75% (3).Since a gantry tilt is not possible with every CT scanner and an alignment of the scan plane along the skull base head support shells were introduced to achieve similar effects in dose reduction. On the one hand the angulated head positioning shortens the scan length that is necessary to image the whole brain. On the other the direct radiation of the orbits with the...

Conclusion and recommendations

Head shells and flexed position of the cervical spine, whenever possible, reduce radiation dose through shorter scan length and prevent exposure of eye lens to primary beam Eye shields can reduce dose to eye lens, but have to be placed after the scout acquisition. Eye shields might hamper diagnostic image quality in facial trauma. Iterative reconstruction with a sharp kernel can improve image quality in head CT.

Personal/organisational information

Thuy D. Do is a radiologist at the University Hospital Heidelberg, Germany, dedicated to research in the field of metal artifact reduction and image quality in computed tomography imaging.

References

1. Bundesamt für Strahlenschutz. Accessed at http://www.bfs.de/DE/themen/ion/anwendung-medizin/diagnostik/referenzwerte/referenzwerte_node.html;jsessionid=E7CE8CED7B3D090D7C41A464A032E8BF.1_cid382. Accessed 04.01.2019. 2. Council Directive 2013/59/EUROATOM. Accessed at https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32013L0059. Accessed 04.01.2019. 3. Nikupaavo U, Kaasalainen T, Reijonen V, et al. Lens dose in routine head CT: comparison of different optimization methods with anthropomorphic phantoms. AJR Am J Roentgenol. 2015;204(1):117-23. 4. Stewart FA, Akleyev AV, Hauer-Jensen M, et al. ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs--threshold doses for tissue reactions in a radiation protection context. Ann...