Keywords:
CT, Radioprotection / Radiation dose, Radiation safety, Dosimetric comparison
Authors:
C. Crowley, B. Carey, O. O’Connor; Cork/IE
DOI:
10.26044/ecr2019/C-3757
Results
Figure 3 shows the workflow of data selection and analysis for Period 1 and Period 2.
After introducing the radiographer feedback tool,
there was a small increase in the rate of red alerts from 4.7% in Period 1 to 5.1% in Period 2.
The five most common study descriptions that resulted in red alerts were the same for both time intervals: CT pulmonary angiograms (CTPA),
CT abdomen pelvis (CT ABP),
CT thorax abdomen pelvis (CT TAP),
CT brain (CTB) and CT thorax (CT Th).
The rate of red alerts triggered by each of these studies during either time interval is shown in Table 1.
There was no significant difference in the rate of red alerts triggered by CT ABP studies between Period 1 and Period 2 (4.7% versus 4.3% respectively).
The rate of red alerts triggered by CTPA (23.7% versus 13.2%),
CTB (11.6% versus 2.5%) and CT Th (4.6% versus 2.2%) studies fell substantially.
However,
the red alert rate for CT TAP studies increased (2.4% versus 6.6%).
Table 2 shows details regarding the true alerts triggered by the top five study descriptions resulting in red alerts for Period 1 and Period 2.
The number of true alerts fell by more than half (from 7 to 3) between both time intervals.
The total DLP for all but one of these alerts exceeded the alert threshold by less than 10%.
The exception was a CT kidneys ureters bladder (CT KUB) performed in Period 1 for which the total DLP exceeded the threshold by 21.56 %.
Figure 4 shows the number of false alerts triggered by these same studies and the various reasons behind each.
Note that some CT examinations had more than one cause for a false alert.
The most common cause of a false alert in Period 1 was a large patient (70 false alerts).
The most common cause of a false alert in Period 2 was tied between a large patient and the addition of an extra study without changing the study protocol (88 false alerts each).
The mean DLP of the main protocols used for the top five study descriptions triggering red alerts are compared for Period 1 and Period 2 in Table 3.
There was no significant difference between mean DLP values for these studies in either time period.
The majority were lower than national dose reference levels (NDRLs)4 or just slightly above,
with the exception of those for CT code stroke and for CT brain pre- and post-IV contrast.
The latter is justified given it is a dual-phase study.
We feel the former is also justified at our centre given it is the principle stroke service provider for south and southwest Ireland.
Radiographers provided their justifications for 17.1% of studies that generated red alerts during Period 2.
Both reviewers independently confirmed the accuracy of these justifications.