vol. 6 2/2017 Inżynier i Fizyk Medyczny
94
radiologia
\
radiology
artykuł naukowy
\
scientific paper
Determining the average function (mass density vs HU) for
the different clinical protocols (scanning and reconstruction
conditions), used facilities and modalities, inserts settings in the
phantom, CT scanners was the most optimized solution. That
approach reduced the effect of the uncertainty of the TPS cali-
bration - (mass density) = f (HU). The CT system uses, for the dif-
ferent anatomical regions, various reconstruction algorithms,
scatter correction, internal filters to enhance image features so
the user has no influence on it. Additionally, the user settings
for the protocols are limited by the predefined setups for the
anatomical region. That solution has been verified during the
end-to-end tests. The results were obtained in the range of the
tolerance +/- 1.5% of the calculated dose compared to the mea-
sured dose.
References
1.
Report 05016, CT scanner automatic exposure control sys-
tems, MHRA, Feb 2005.
2.
Report 05016, Wide bore CT scanner comparison report ver-
sion 12, MHRA, Feb 2005.
3.
Comparative specifications, Wide bore CT scanners, Purchasing
and Supply Agency, CEP08029, March 2009. R.R. Liu, K.L. Prado,
D. Cody:
Optimal acquisition parameter selection for CT simulators
in radiation oncology
, J Appl Clin Med Phys., 9(4), 2008, 2878
4.
of%20the%20Philips%20automatic%20exposure%20con-
trol%20system.pdf
Tab. 4
The final calibration of the HU values vs physical densities introduced to TPS
DENSITY
AV
BODY+HEAD ACS ALL
PROTOCOLS
AV
BODY+HEAD fixed ALL
PROTOCOLS
AV ACS +1000
AV
BODY+HEAD ACS ALL PROTOCOLS
PHILIPS+SIEMENS
0,200
-788,68
-789,63
211,32
182,71
0,500
-474,52
-474,83
525,49
506,24
0,960
-67,07
-67,12
932,93
929,68
0,990
-33,39
-33,91
966,61
966,11
1,000
-6,86
-5,47
993,14
996,76
1,060
32,76
31,65
1032,76
1037,57
1,070
46,43
46,54
1046,43
1052,37
1,160
197,12
197,14
1197,12
1220,28
1,530
846,90
846,88
1846,90
1911,29
1,820
1282,12
1283,56
2282,12
2365,37
2,697
1989,04
1995,75
2989,04
3111,51
7,737
6423,27
6439,85
7423,27
7423,27
4,345
5606,33
5640,20
6606,33
6606,33
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