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Keywords:
Radioprotection / Radiation dose, CT, Cone beam CT, Comparative studies, Dosimetric comparison
Authors:
J. Neubauer1, C. Neubauer1, M. Langer1, E. Kotter1, J. M. Voigt2, M. Fiebich2; 1Freiburg/DE, 2Gießen/DE
DOI:
10.1594/ecr2015/C-1457
Methods and materials
We used a 320-row MDCT (Aquilion One,
Toshiba,
Otawara-shi,
Japan) and a mobile dedicated extremity FPCT (Verity; Planmed,
Helsinki,
Finland) for data acquisition.
For the MDCT the voltage can be set to 80,
100,
120 and 135 kVp.
In FPCT the voltage can be changed from 80 to 96 kVp.
The default settings for wrist examinations were 120 kVp / 40 mAs in the MDCT and 90 kVp / 36 mAs in the FPCT.
In vitro wrist examinations of a cadaveric human hand were performed in default settings and all possible settings with lower doses in the MDCT (default setting and 20 low dose settings) and the FPCT (default setting and 19 low dose settings).
The tube voltage we used in the MDCT ranged from 80 to 120 kVp (80,
100,
120 kVp) with equally modified tube currents from 5 to 40 mAs (5,
7,
10,
15,
20,
30,
40 mAs) for each voltage setting.
Accordingly to the capabilities of the FPCT we chose a tube voltage from 80 to 90 kVp (80,
84,
88,
90 kVp) with a tube current ranging from 12 to 36 mAs (12,
18,
24,
30,
36 mAs) for each voltage setting in the FPCT.
Monte Carlo simulations were used to calculate the radiation doses as previously described [1].
The images were reconstructed with iterative technique (AIDR3) for MDCT and with filtered back projection algorithm for FPCT.
Then the data were sent to a PACS (AGFA Impax 6,
Agfa,
Mortsel Belgium).
Image quality regarding the cortical bone,
cancellous bone,
articular surface,
soft tissue and artifacts was analyzed by 5 independent and blinded readers: 3 radiologists with an experience of 1,
3 and 5 years and 2 orthopedic surgeons with an experience of 10 and 18 years.
The images were presented in a randomized order.
Modality and dose settings were masked for the readers.
For the analysis a Likert scale with a score ranging from 1 (= very good),
2 (= good),
3 (= fair),
4 (= poor) to 5 (= very poor) was used.
Good overall image quality was assumed with a sum of all ratings ≤50.