Congress:
EuroSafe Imaging 2020
Keywords:
Performed at one institution, Not applicable, Dosimetric comparison, Dosimetry, Cone beam CT, Radioprotection / Radiation dose, Neuroradiology brain, Interventional Radiology
Authors:
A. Brehm, G. Stamm, M. Lüpke, B. Stieltjes, M.-N. Psychogios
DOI:
10.26044/esi2020/ESI-02924
Description of activity and work performed
We measured effective dose according to the IRCP 103 (1) using an anthropomorphic phantom equipped with 60 thermoluminescent dosimeters (TLDs). Twelfe TLDs were inserted into the head, while all other relevant organs were covered with at least 4 TLDs. In order to account for variation and to ensure that a dose above the minimal reliable detection level can be recorded, each acquisition was performed ten times. The phantom wasn`t moved during the different acquisition runs. Additionally, we measured dose to the eye lens with 2 TLDs per eye.
Manufacturer-specified protocols, which we routinely use in clinical practice were measured on a biplane angiography-system (Artis Q, Siemens Healthineers AG, Forchheim, Germany). The placement of the phantom reassembled the placement of a typical patient. The coverage for each protocol can be seen in figure 1.
We summarized the effective dose to patient values for each protocol in table 1.
FDCT Protocol |
20s DR Head |
7s DR Head |
mpFDCT HD |
mpFDCT low-dose |
Bolus-tracking |
FDCT Perfusion |
Number of rotations |
1 |
1 |
2 |
2 |
- |
10 |
Tube potential (kV) |
109 |
109 |
70 |
70 |
73 |
77 |
dose/frame (μGy/f) |
1.82 |
1.82 |
1.2 |
0.36 |
3.00 |
0.36 |
Rotation angle (degree) |
200 |
200 |
200 |
200 |
- |
200 |
Angulation step (degree/frame) |
0.4° |
0.4° |
0.8° |
0.8° |
- |
0.8° |
Number of images |
500 |
500 |
2 x 250 |
2 x 250 |
2 per second |
10 x 250 |
Scan time/rotation (s) |
20 |
7 |
10 |
10 |
- |
5 |
Lens-Dose (mGy)
|
24.4 |
22.7 |
60.4 |
13.8 |
0.25/s* |
45.6 |
Effectie dose (mSv) |
2.6 |
2.4 |
8.9 |
2.8 |
0.047/s* |
|
Table 1. Summary of the FDCT protocols and their effective dose measurements (*dose rate)
In all measurements at least 97% of the radiation was recorded in the brain, red bone marrow, esophagus and thyroid. The remaining organs received less than 3% of radiation, rendering them clinically unimportant. The eye lens dose was not used for the calculation of the effective dose, as it does not have a weighting factor.