Received: 4 March 2021
Accepted: 13 May 2021
First Online: 27 May 2021
: All procedures contributing to this work comply with the ethical 314 standards of the relevant national and institutional guidelines on human experimentation (Finland) and 315 with the Helsinki Declaration of 1975, as revised in 2008. Permission from the Northern Savo hospital district ethical board was obtained on 25th 316 July 2017 (Number 268/2017). The study is registered in 317 ClinicalTrials.gov (Identifier: NCT03327688). Consent from patients was not required due to the retrospective nature of the analyses.
: Not applicable.
: The first author, OH, is the owner of a small company Ultra-Mestarit Oy providing ultrasound training to medical professionals. The other authors declare that they have no competing interests.