Keywords:
Dosimetric comparison, Radiation safety, Dosimetry, CT, Radioprotection / Radiation dose, Neuroradiology brain, CNS
Authors:
J. N. Balcombe1, J. Luckman2, M. Guindy1; 1Tel Aviv/IL, 2Ramat Hasharon/IL
DOI:
10.26044/ecr2019/C-0612
Conclusion
Surprisingly large dose variation of 18% was demonstrated between head CT protocols on 2 identical scanners within one institution.
The cause was variation in the predefined noise index setting within the protocols,
which was set to a different level on each scanner.
The predefined noise index is a critical component of the automated exposure control (AEC) mechanism which is integral to every CT scanner (1). Each manufacturer uses different methods to achieve this function (2).
This setting is not readily visible to the reading radiologist.
There is no mention of this setting on the images in PACS or on the dose summary screen attached to each scan,
as there is no DICOM field for the image quality reference parameter. Therefore discrepancies in this vital scan parameter are not obvious and can persist indefinitely.
In this case dose monitoring software revealed the discrepancy,
and resulted in initiation of a detailed evaluation of the protocol parameters at the scanner console,
eventually revealing the cause of the problem and leading to successful intervention.
Dose monitoring software is an effective tool for revealing inconsistencies in scan parameters between scanners which are supposed to be identical,
but which in real world scenarios may demonstrate significantly different radiation doses.
The dose monitoring software can reveal the dose differences leading to discovery of the underlying protocol error.