Australian national diagnostic reference levels for MDCT - PAEDIATRIC

The following tables present the current national 'Child' and 'Baby/Infant' DRLs for Multi Detector CT

Table 1:   Australian Child (5-14 yrs) MDCT DRLs
Australian Child (5-14 years
MDCT Diagnostic Reference Levels
Child Protocol DLP
(mGy.cm)
CTDI vol
(mGy)
Head 600 35
Chest 110 5
AbdoPelvis 390 10
Table 2:   Australian Baby/Infant (0-4 years) MDCT DRLs
Australian Baby (0-4 years)
MDCT Diagnostic Reference Levels
Baby
Protocol
DLP
(mGy.cm)
CTDI vol
(mGy)
Head 470 30
Chest 60 2
AbdoPelvis 170 7

Note: CTDIvol values for the Head are based on the 16 cm PMMA reference phantom and Chest and AbdoPelvis are based on the 32 cm PMMA reference phantom.

The service is ongoing with dose comparisons available in calendar year periods.

Results

At the end of July 2012, ARPANSA was given access to paediatric dosimetry MDCT data that had been collected via a Royal Australian and New Zealand College of Radiologist’s (RANZCR) supported survey of paediatric facilities in Australasia. Sufficient paediatric data was submitted for ARPANSA to calculate paediatric DRLs for baby and child cohorts for Head, Chest and AbdoPelvis protocols.

Due to differences in the surveyed scan parameters it was not possible to directly import the RANZCR data into the ARPANSA database and insufficient data was generated per facility for ARPANSA to be able to generate individual Facility Reference Levels (FRL). However 4 fields, kVp, Girth (cm), CTDIvol (mGy) and DLP (mGy.cm) were able to be used in this analysis. It should also be noted that for multiple phase scans the CTDIvol was based on the average value and the DLP was based on the total value.

Adult MDCT DRLs have previously been determined by calculating the 75th percentile of the spread of FRLs. As the QUDI dataset did not allow this approach, the Paediatric MDCT DRLs were calculated by determining the 75th percentile of the spread of individual doses submitted.

Conclusion

These calculated CTDIvol and DLP DRLs are broadly in agreement with paediatric data published by Brady et. al. in BJR, DOI 10.1259/bjr/28015185 and data submitted to the ARPANSA survey from a specialist paediatric teaching hospital.

ARPANSA acknowledges the data provided by the QUDI program.

The ARPANSA DRL Service is ongoing with dose comparisons available in calendar year periods. We would encourage all MDCT imaging facilities that acquire paediatric scans to register and compare their doses both for their benefit and so that updated paediatric DRLs will accurately reflect contemporary Australian scanning dosimetry.

For more information on DRLs or the Australian National DRL Service please see the Introduction and Fact sheet pages.

Statistical analysis

Habitus, reference phantom diameter, age cohort & number of scans

Head 16 cm Baby - 316 scans
  Mean Std Dev Minimum Maximum Median 25th % 75th %
Age 2.0 1.5 0.0 5.0 1.6 0.7 3.3
Girth 16.3 1.9 8.6 21.9 16.6 15.3 17.5
CTDIvol 21.2 8.2 3.6 49.3 21.3 15.8 25.5
DLP 344.1 167.7 37.9 1021.8 345.6 211.3 469.0

 

Head 16 cm Child - 497 scans
  Mean Std Dev Minimum Maximum Median 25th % 75th %
Age 9.7 3.0 5.0 15.0 9.5 6.8 12.4
Girth 18.7 1.3 15.0 21.6 18.7 17.8 19.6
CTDIvol 29.5 10.0 6.0 88.0 28.4 24.3 32.9
DLP 492.9 205.3 63.3 1477.0 519.6 338.6 604.1

 

Chest 32 cm Baby - 107 scans
  Mean Std Dev Minimum Maximum Median 25th % 75th %
Age 2.1 1.6 0.0 4.9 2.0 0.6 3.5
Girth 18.3 3.4 9.7 30.9 18.7 16.3 20.2
CTDIvol 2.0 2.5 0.4 19.4 1.2 0.9 1.8
DLP 46.8 29.3 6.4 121.6 43.5 20.9 60.2

 

Chest 32 cm Child - 119 scans
  Mean Std Dev Minimum Maximum Median 25th % 75th %
Age 9.4 3.0 5.0 14.9 9.6 6.4 11.7
Girth 25.5 4.9 12.4 44.9 24.4 22.2 27.8
CTDIvol 4.3 5.6 0.2 31.1 1.9 1.2 5.2
DLP 88.5 80.1 6.7 468.7 62.2 45.0 109.1

 

AbdoPelvis 32 cm Baby - 40 scans
  Mean Std Dev Minimum Maximum Median 25th % 75th %
Age 3.0 1.4 0.1 4.9 3.3 2.2 4.3
Girth 18.6 3.0 9.9 27.7 18.5 16.9 20.4
CTDIvol 5.4 4.7 0.6 21.1 4.8 1.9 6.5
DLP 129.1 82.5 19.0 374.6 122.5 57.7 165.6

 

AbdoPelvis 32 cm Child - 128 scans
  Mean Std Dev Minimum Maximum Median 25th % 75th %
Age 10.5 3.0 5.0 14.9 10.7 8.0 13.5
Girth 26.7 5.6 17.3 42.9 25.6 22.0 30.7
CTDIvol 7.7 4.7 1.3 42.4 6.9 5.5 8.9
DLP 303.9 166.9 16.8 911.8 265.1 203.1 388.1

 

For more information on DRLs of the Australian National DRL Service please see the Introduction and Fact Sheet pages.


Further information on International Best Practice for Radiation Protection of Patients can be found on the International Atomic Energy Agency Radiation Protection of Patients website, which can be accessed via the following link: