Data were prospectively collected on consecutive procedures performed from January 2016 to June 2016 on a Somatom Definition FLASH Siemens.
Of each procedure patients data (name,
weight and birth date),
examination-data (kind of procedure,
clinical question,
date,
CTDIvol16/32 and DLP16/32) were recorded.
CTDIvol is reported as mGy,
DLP as mGy*cm.
CTDIvol/DLP16 from head CT were divided into 5 age-groups (<4weeks,
4weeks - <1y,
1y -<6y,
6y – 10 y,
>10y) and of each one 75th-percentile was calculated.
CTDIvol/DLP32 from thorax (chest,
cardiovascular CT angiography) and abdomen+pelvis CT examination were divided into 5 weight-groups (<10Kg,
10kg - <15Kg,
15 - <30Kg,
30 -<60Kg,
>60Kg) and of each one 75th-percentile was calculated.
Data were compared to European DRLs and recent literature data.
Weight groups were compared to age groups of previous data as indicated in table 11.2 of PidRL guidelines (<10Kg to newborn,
10kg - <15Kg to 1 years,
15 - <30Kg to 5 years,
30 -<60Kg to 10 years,
>60Kg to adult).
Weight-groups are considered representative samples if at least 10-patients per procedure-type and per patient-group are included.
PiDRL European guidelines recommend DRLs for high-dose routine CT examinations (head,
chest,
abdomen,
trunk and spine) differentiating them on the basis to the clinical task (e.g.
DRL for CT Head,
indication: ventricular size).
Figure 1 shows the list of CT examinations and clinical indication for which DRLs are recommended and the list of those who are included in this study.
Fig. 1: Table 1 - List of recommended CT and clinical indication DRLs (column PiDRL) and of those included in this study (column OPBG DRL)
In particular,
we do not consider CT examinations that are not routinely performed in our Hospital.
Our local DRL are substantially lower than that proposed by PiDRL guidelines.
HEAD
Results are summarized in figure 2 (head).
Fig. 2
All age groups,
except newborn one (1-patient per procedure-type included) are representative.
Specifically CTDIvol/DLP16 for head CT are 29,1/513 (4 weeks – 1y),
31,2/570 (1-6 y),
32,2/582 (6-10 y),
33,1/642 (>10y) respectively.
DRL are estimated only for routine head CT scanning: till this study there were no differentiated scan protocols for routine or ventricular size (shunt) examinations.
Figure 2 shows the revised LDRL OPBG 2016 in comparison to previous LDRL OPBG 2014,
European DRLs and recent literature.
Fig. 2
LDRL 2016 for routine head results to be slightly decreased than those of LDRL OPBG 2014 in all age-group and lower than those proposed by PiDRL guidelines (European DRLs) in age group 1-6 y,
6-10 y and >10y.
In age group 4 weeks – 1 y both CTDIvol (29.1) and DLP (513) result to be higher than European ones (25 and 370 respectively).
The revision of protocols parameters highlighted the use of same scan settings regardless of child-age or clinical question.
A revision of head scan settings for all age – group patients has been done; not yet for clinical task.
CHEST
Results are summarized in figure 3.
Fig. 3
All weight groups are representative (at least 10-patients per procedure-type and per patient-group included).
Specifically CTDIvol/DLP32 for chest CT are 1/22 (<5Kg),
1,52/42 (5-15Kg),
1,83/56 (15-30Kg),
2,99/113 (30-60Kg),
6,07/239 (>60Kg) respectively.
For cardiovascular CT angiography are 0,71/15 (<5Kg),
1,01/21 (5-15Kg),
2,44/36(15-30Kg),
2,87/90 (30-60Kg),
13,72/311 (>60Kg).
Figure 4 shows the revised LDRL OPBG 2016 in comparison to previous LDRL OPBG 2014,
European DRLs and recent literature.
Fig. 4
LDRL 2016 for routine chest results to be lower than that proposed by PiDRL guidelines (European DRLs) and other studies (Granata et al 2015;Ruiz-Cruces et al 2015; Roch et al 2013) in all weight groups.
In weight-group >60kg the DLP is high (239) while the CTDIvol is within the normal range.
This is probably due to the fact that the scanned region is longer than necessary or that neck evaluation is included in chest scanning.
Both CTDIvol and DLP in weight groups 30-60 kg and >60 Kg of revised LDRL 2016 were found to be higher than those of LDRL OPBG 2014.
The revision of the scan parameters (e.g.
tube voltage and ref mAs settings,
helical pitch,
rotation time,
slice thickness,
etc.,
etc.) highlighted the use of tube voltage and image noise indicator higher than those used in 2014 (respectively 120 vs 100 kV and 110 vs 90 ref mAs) in X-CARE (virtual organ-shielding technique) protocol (see figure 5).
Fig. 5
There were no evident clinical reasons to increase those settings.
This fact was due to a software upgrade of CT scanner in 2015: the equipment was implemented with CARE kV (that provide an automatic adjustment of tube current) but chest X-CARE protocols for larger patients were not properly setted.
A revision of X-CARE chest scan settings for >30 Kg patients has been done.
ABDOMEN
Results are summarized in figure 6 (abdomen).
Fig. 6
DRL are estimated only for abdomen+pelvis ; the upper abdomen scanning is not routinely performed in our Hospital.
All weight groups,
except <5Kg group (5-patients per procedure-type included) are representative.
Specifically CTDIvol/DLP32 for abdomen+pelvis CT are 1,9/47(<5Kg),
2,68/83(5-15Kg),
3,25/131(15-30Kg),
7,77/320(30-60Kg),
11,21/532(>60Kg).
Figure 7 shows the revised LDRL OPBG 2016 in comparison to previous LDRL OPBG 2014,
European DRLs and recent literature.
LDRL 2016 for abdomen+pelvis scan results to be lower than that proposed by PiDRL guidelines (European DRLs) and other studies (Granata et al 2015;Ruiz-Cruces et al 2015; Roch et al 2013) in weight groups 5-15kg,
15-30kg and >60kg.
Fig. 7
In weight-group 30-60kg both CTDIvol (7.77) and DLP (320) are higher than those proposed by European DRLs (7 and 290),
Roch et al 2013 (7 and 245) and our LDRL 2014 (7 and 290).
Again this was due to incorrect settings in the protocols of larger patients after the 2015 software upgrade of CT scanner.
A revision of scan settings for 30-60 kg patients has been done.