[Resolution and sensitivity of a two-dimensional ionisation chamber array (PTW type 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 x 2 cm. The minimal field size can be reduced to 1 cm x 1 cm by shifting the array 5 mm 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 1 mm. Therefore, the resolution capabilities of the 2D-Array are sufficient for most intensity-modulated radiation therapy (IMRT)fields.
Poppe
Björn
B
Pius-Hospital und Carl von Ossietzky Universität, AG Medizinische Strahlenphysik, Oldenburg. bjoern.poppe@uni-oldenburg.de
Atung
Zanzem
Z
Chofor
George
G
Blechschmidt
Arne
A
Djouguela
Armand
A
Kollhoff
Ralf
R
Rubach
Antje
A
Harder
Dietrich
D
D006801:Humans; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods* / Q000592:standards; D012680:Sensitivity and Specificity