CEFLA MyRay Hyperion X9 - CTDI (Computed Tomography Dose Index) Measurements

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OPERATOR'S MANUAL
EN
10.6. CTDI (COMPUTED TOMOGRAPHY DOSE INDEX) MEASUREMENTS
The CTDI was measured using a cylindrical PMMA phantom with a diameter of 16 cm with holes at 12, 3, 6 and 9
o’clock and in the centre.
Diagram of PMMA cylinder for CTDI measurements
During the measurements, the holes that remained empty were filled with PMMA cylinders and the ionisation
chamber was inserted in the hollow reference cylinder.
The possible operating conditions of the X-ray device consist of the following 11 scanning modes, distinguished by
size of the field of view selected and by choice between high resolution and maximum resolution (HiRes):
[11x13e], [11x8], [11x8] HiRes, [11x5], [11x5] HiRes, [8x8], [8x8] HiRes, [8x5], [8x5] HiRes, [5x5], [5x5] HiRes.
The version with the smaller panel, 1308 DXT instead of 1313 DXT, has only 7 of these modes:
[11x8e], [11x5], [11x5] HiRes, [8x5], [8x5] HiRes, [5x5], [5x5] HiRes.
The load factors (mA, exposure time) are automatically determined by the system. The X-ray load automatically set
by the machine for this dosimetric phantom for CTDI is reasonably similar to that of an average patient. The table
indicates the X-ray load used, typically suggested by the X-ray device.
Type
of
examination
Technical factors
Central
Lateral
(left
of patient)
Lateral
(right
of patient)
Lateral
(back
of patient)
Lateral
(front
of patient)
[11x13e]
***
kV
90
90
90
90
90
mA
4.00
4.00
4.00
4.00
4.00
exposure time (s)
7.2
7.2
7.2
7.2
7.2
mAs
28.80
28.80
28.80
28.80
28.80
CTDI100 [mGy]
2.946
2.568
2.629
2.492
2.551
[11x8e]
*
kV
90
90
90
90
90
mA
4.00
4.00
4.00
4.00
4.00
exposure time (s)
7.2
7.2
7.2
7.2
7.2
mAs
28.80
28.80
28.80
28.80
28.80
CTDI100 [mGy]
3.202
2.808
2.891
2.672
2.761
[11x8]
**
kV
90
90
90
90
90
mA
4.00
4.00
4.00
4.00
4.00
exposure time (s)
3.6
3.6
3.6
3.6
3.6
mAs
14.40
14.40
14.40
14.40
14.40
CTDI100 [mGy]
2.104
1.838
1.878
1.780
1.822
[11x8]
HiRes
**
kV
90
90
90
90
90
mA
6.00
6.00
6.00
6.00
6.00
exposure time (s)
9.0
9.0
9.0
9.0
9.0
mAs
54.00
54.00
54.00
54.00
54.00
CTDI100 [mGy]
7.271
6.182
6.206
6.144
6.182
[11x5]
kV
90
90
90
90
90
mA
4.00
4.00
4.00
4.00
4.00
exposure time (s)
3.6
3.6
3.6
3.6
3.6
mAs
14.40
14.40
14.40
14.40
14.40
CTDI100 [mGy]
2.287
2.006
2.065
1.909
1.972