Material and Methods
The study has been performed at the operating theatre of a University Paediatric Hospital.
Three c-arm units are available at the surgical area: GE Brivo 785,
Philips BV Libra and Siemens Siremobil.
The last mentioned does not have the capability of exporting images to PACS system,
so it does not take part of the study.
The other units do export stored images and the technical parameters associated with them to the PACS.
The data that have been recorded from the PACS system are: Dose Area Product (DAP),
Entrance dose (E) and fluoroscopy time (t) (4).
Information has been recorded manually from the images for orthopaedic studies performed this last year,
including just two main anatomical regions: hips and spine.
106 patients’ data have been recorded and analysed,
grouped by age,
because patient weight is by now not available in the PACS system.
Classification has been based on European guide 185 Group I,
[5-10) years,
Group II,
[10,15) years and Group III,
[15,
18] years (4).
Younger children have not been included because the sample is minimal.
The quantity of interest to establish DRLs for this studies is the DAP,
because entrance Kerma is specified at a different distance for each c-arm device and fluoroscopy time does not appear to be related with patient size,
no correlation has been found.
For local DRLs establishment in each group,
75th percentile of DAP values sample has been calculated (4),
after having dismissed the outliers. Then,
values obtained have been rounded.
Results and Discussion
Tables 1 and 2 show the mean,
median and 75th percentile for each group.
Mean values include standard deviation,
showing the great dispersion of the data for some groups.
This result was highly expected,
since our hospital is specialised in high complexity procedures and for each region considered there are many different surgeries.
Figures 1 and 2 show the preliminary DRLs obtained for orthopaedic studies,
for hips and spine.
For hips,
DRLs are congruent with age,
and increase with patient size.
However,
spine do not follow this trend,
probably because most of the patients belong to group III.
Furthermore,
group III includes adolescents submitted to spine surgery,
the most common procedure for this age group and the most standardized procedure,
thus patient doses are lower and also more homogeneous.
Doses have been compared with paediatric DRLs published for orthopaedic procedures in ESR 2015 by Almeida et al (5),
even though this publication does not specify type of procedure.
Results are shown in figure 3.
Recent DRLs published for MCU in Europe (4) show similar values as these established in this study: 750-800 mGy.cm2 for groups I and II.
These results reflect the importance of DRLs as an optimization tool in surgical procedures,
for patient doses are significant.