Keywords:
Dosimetry, CT, Radioprotection / Radiation dose, Radiation physics, Paediatric, Dosimetric comparison
Authors:
A. Ploussi1, V. G. Syrgiamiotis2, T. Makri1, G. A. T. Messaris3, C. Hatzigiorgi1, E. Efstathopoulos1; 1Athens/GR, 2GOUDI/GR, 3Patras/GR
DOI:
10.26044/ecr2019/C-1214
Methods and materials
Patient cohort: The study enrolled 851 pediatric patients who underwent head,
neck,
internal auditory canal (IAC),
chest,
and abdomen-pelvis (AP) CT examinations over an 11-month period at a dedicated children’s hospital.
Patients’ characteristics are summarized on Table 1.
CT data acquisition: All CT examinations were performed on a 16-multidetector CT with the use of age-based protocols and automatic exposure control.
Patients were scanned using iterative reconstruction algorithm (blend of 60% adaptive statistical iterative reconstruction and 40% filtered back projection).
Head CT scans were performed in axial mode using a 2.5 mm slice thickness from the skull base to cerebellum tentorium and a 5 mm slice thickness from cerebellum tentorium to vertex.
All other types of CT examinations were performed using helical mode.
CT dose indices: For the determination of DRLs,
volume CT dose index (CTDIvol) and Dose Length Product (DLP) were retrospectively derived from the dose report stored in the hospital’s Picture Archiving and Communication System (PACS).
DRLs were set at the 75th percentile (3rd quartile) of CTDIvol,
DLP per acquisition and total DLP.
For the head,
neck and IAC CT examinations,
DRLs are referenced to the 16-cm-phantom and for the body (chest and AP) to the 32-cm-diameter phantom.
Table 1.
Patients’ characteristics.
CT Examination
|
Age group
|
Number of examinations
|
Number of acquisitions
|
Male/
Female
|
Age
(yr)
|
Weight (kg)
|
Height (m)
|
Head
|
0-18 months
|
81
|
89
|
52/29
|
0.6±0.6
|
8.8±8.5
|
0.7±0.2
|
18 months-5 y
|
99
|
110
|
60/39
|
3.3±1.1
|
15.7±5.3
|
1.0±0.1
|
5-15 y
|
301
|
335
|
185/116
|
10.1± 2.9
|
40.2±15.8
|
1.4±0.2
|
Neck
|
0-18 months
|
2
|
2
|
0/2
|
0.7±0.3
|
9.5±0.7
|
0.7±0.1
|
18 months-5 y
|
10
|
17
|
7/3
|
3.6±1.1
|
18.0±6.0
|
1.0±0.2
|
5-15 y
|
32
|
44
|
14/18
|
12.0±3.0
|
46.6±19.1
|
1.5±0.1
|
IAC
|
0-18 months
|
8
|
8
|
5/3
|
1.0±0.2
|
8.6±1.7
|
0.7±1.0
|
18 months-5 y
|
19
|
24
|
11/8
|
3.0±1.1
|
14.8±3.4
|
1.0±0.1
|
5-15 y
|
24
|
24
|
11/13
|
9.8±2.9
|
35.0±13.4
|
1.4±0.2
|
Chest
|
0-5 y
|
66
|
97
|
46/20
|
2.8±1.8
|
12.7±6.1
|
0.9±0.2
|
5-16 y
|
147
|
187
|
91/56
|
11.7±3.2
|
47.0±19.3
|
1.5±0.2
|
AP
|
0-5 y
|
22
|
40
|
9/13
|
2.6±1.7
|
13.4±5.5
|
42.4±16.4
|
5-16 y
|
40
|
64
|
16/24
|
10.6±2.9
|
0.9±0.3
|
1.5±0.2
|