Über das Auflösungsvermögen und die Empfindlichkeit eines zweidimensionalen Ionisationskammer-Arrays (PTW: Typ 10024)

The two-dimensional verification of intensity-modulated radiation plans is one of the major requirements for the safe application of this technique. The present study examines the resolution and sensitivity of a two-dimensional ionisation-chamber array (PTW2D-Array, type 10024), which can be used for plan verification instead of films. According to the Shannon-Nyquist theorem, the resolution of the 2D-Array is sufficient for dose distributions with a minimal field size of 2 cm×2 cm. The minimal field size can be reduced to 1 cm×1 cm by shifting the array 5mm in the direction of the MLC movement and by repeating the measurements. The high sensitivity against a monitor decalibration for a single field of a sequence is demonstrated on the basis of an individual case. The minimal threshold for MLC misalignment detected by a chamber of the array is less than 1mm. Therefore, the resolution capabilities of the 2D-Array are sufficient for most intensity-modulated radiation therapy (IMRT) fields.