[Absorbed dose during helical acquisition CT. Effect of acquisition parameters].
OBJECTIVE
European directive 97/43 specifies that the dose delivered to the patient during a radiological procedure should be estimated. In order to prepare for implementation of this new regulation, we have studied the dose delivered during spiral CT acquisition.


METHODS
We have studied the influence of slice thickness, pitch, tube voltage and intensity, and acquisition volume length. We present measurements for single and dual detector CT scanners. We used a pencil ionization chamber to measure air kerma. We measured absorbed dose in water with a waterproof ionization chamber set in a semi-customized phantom filled with water. Chambers were set on the rotation axis of the CT scanners. We studied the dose outside the acquisition volume.


RESULTS
We quantified the influence of each parameter on the absorbed dose. We used our measurements to calculate the dose for different acquisition protocols. Also we evaluated the dose to organs distant from the acquisition area.


CONCLUSIONS
This study is one step toward a systematic estimation of the dose delivered to patient during helical CT exams. To use these results in daily practice, we have to develop software using our measurements.
Service de Cancérologie-Radiothérapie, CHU de Grenoble, BP 217, 38043 Grenoble Cedex. jean-yves.giraud@ujf-grenoble.fr
J Y
JY
Giraud
J
J
Sage
D
D
Taisant
A
A
Dusserre
M
M
Bolla
M
M
Coulomb
H
H
Kolodié
R
R
Barthelemy
B
B
Aumont
G
G
Ferretti
D004867:Equipment Design; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D014057:Tomography, X-Ray Computed / Q000379:methods*