Despite of the fact that Computed Tomography (CT) makes up only 6 % of all X-ray examinations, it is responsible for around 50 % of the collective, effective ionising radiation exposure for patients.
As a result, the accurate Dose measurement together with the examination of the image quality is at the heart of Quality Assurance in CT.
Acceptance tests at CT scanners are carried out according to IEC 61223-3-5
(DIN EN 61223-3-5).
Constancy tests at CT scanners have to be done in accordance with the Standard IEC 61223-2-6
(DIN EN 61223-2-6).
The Standard specifies the following test parameters:
- Noise
- Uniformity
- Mean CT-Number
- Spatial Resolution
- Tomographic section thickness
- Dose
- Positioning of the patient support
The parameters for testing the image quality are calculated with the use of a test device which is generally supplied by the CT manufacturer at the time of delivery. For the dose measurement a special head and body phantom made of PMMA (Polymethyl- methacrylate) is stipulated. The phantoms are used in conjunction with a pencil-shaped ion chamber DCT10-RS and the Dosemeter DOSIMAX plus A HV. It is the so called CTDI value (Computed Tomography Dose Index), an integral of the Dose profile along a straight tomographic level, which must be calculated. The CTDI value must be measured at least every 6 months and always following any maintenance work to the CT Installation.
More detailed information can be found in our specialist booklet “Radiation Exposure in Computed Tomography” (Order number: VD1019101; please see the follwing page)
Additionally, IBA Dosimetry offers the customer a wide range of test devices and phantoms all of which allow more detailed tests of image quality than required by current standards.