Introduction: X-ray imaging is the most commonly used medical imaging method. Chest
imaging is one of the most common examinations in general radiography. Due to its frequent
performances it is also one of the most dose-loading. Particularly common procedures are
chest X-rays in bed, where imaging is performed in a supine position with an image detector
directly below the patient. Purpose: The purpose of this thesis was to determine the
differences in dose loads (DAP, effective dose, dose to organs, EI) and image quality when
imaging the thoracic organs lying down, using different exposure conditions and changing
the position of the image detector. Methods: We did our diploma work with a review of
existing literature and experimental work. The experimental part was performed on a
anthropomorphic phantom PBU 60 and a Multix / Vertix X-ray machine manufactured by
Siemens, at the Faculty of Medicine. We used DR and CR systems. We performed 210 chest
organ imaging, using exposure conditions ranging from 81 to 90 Kv and from 0.50 to 1.0
mAs. The RGO was 82 cm in all SS positions. The phantom was placed in the AP projection.
The DAP value and the exposure index were observed for individual measurements. Later,
trough programs, we also calculated the effective dose, SNR and CNR value. Results:
Based on the results, we found that both in the DR and in the CR system, there are
statistically significant differences in the exposure index. In the DR system, there are
statistical differences between P1 (position of the image receiver under the phantom) and P3
(position of the image receiver under the table) (p <0.001). the difference averaged 100.15
(48.77%). In the CR system, however, we found that there were statistically significant
differences in all positions. The largest difference on average was between P1 and P3, 138.59
(64.77%). There were no significant statistical differences between the DAP value and the
effective dose in the DR and CR systems. Differences between P1 and P2 and between P1
and P3 are statistically significant for the CNR values of the DR system. The largest average
difference between P1 and P2 (position of the image receiver under the lining) is 4.01 dB
(12.96%). With the CR system, there are statististically significant differences between P1
and P3 and between P2 and P3. The largest average difference between P2 and P3 is 1.28
Db (4.22%). With the DR system, there are statistically significant differences in SNR values
between P1 and P2 and between P1 and P3. The largest average difference between P1 and
P2 is 4.6 Db (13.91%). In the case of the CR system, there are statistically significant
differences between P2 and P3 and between P1 and P3. The largest average difference was
between P1 and P3 of 0.99 dB (3.04%). Discussion and conclusion: We proved that the
value of the exposure index and the image quality are affected by the changed position of
the image receiver and the changed exposure conditions, while the DAP value is not affected
by the position of the image receiver. The DAP value was influenced only by changing the
exposure conditions.
|
