The most comprehensive QA phantom for modern MV portal imagers


The most comprehensive QA phantom for modern MV portal imagers




  • QUALIFORMED's OTP-EPID phantom has been designed to accurately measure in a single acquisition all the main parameters which characterise the performance of portal imagers operating with high energy X-ray photons (1-45 MV) used in radiotherapy to determine patient position vis-à-vis radiation beam limits.
  • You can find on the market many other phantoms that were developed 20 years ago and are no longer at all adapted to modern portal imager with flat panel. Our newly developed phantom is perfectly suitable for all old as modern high energy portal imagers. It uses all modern techniques to individually assess all essential parameters characterising the quality of images obtained with the imager (contrast, spatial resolution, geometric distortions, linearity of the signal...)
  • Analysis of the images of the OTP-EPID test object is optimal (precise, automatic, quick) when used in conjunction with the QUALIMAGIQ software platform, complemented by the MOD-EPID analysis module. Analysis of the images without software remains possible.



  • Geometrical distortions: 49 tungsten balls distributed over a large surface to enable mapping of distortion.
  • Spatial resolution with two high contrast Edges: OTP-EPID is the only test object available for applying ISO method 12233:2000, referred to as the "Edge Spread Function", in order to accurately measure the imager's MTF.
  • Spatial resolution with Line Pair patterns: 16 horizontal and vertical patterns made up of regularly spaced line pairs, alternately radio-opaque and radio-transparent, allow you to evaluate spatial resolution visually or with the DROEGE & MORIN method.
  • Contrast: 22 circular targets of increasing thickness distributed equidistant from the beam's center. This circular distribution of targets around the beam axis and their wide diameter prevent the contrast measurements from being distorted by respectively, the non-homogeneity of the signal caused by the flattening filter, the noise or a lack of spatial resolution
  • Linearity of the imager response: Measured by 11 copper tubes of increasing height set along a circular ring centered around the centre of the beam to be free of influence of any lack of homogeneity of the signal caused by the flattening filter.
  • Uniformity of the linearity of the imager response: 13 groups of 4 copper tubes situated in 13 zones distributed evenly over the entire surface of the test object.


Geometrical distortion targets

Geometrical distortion targets

Contrast targets


Spatial resolutions targets

Uniformity and linearity targets







  • The essential measurements caracterising the image quality (spatial resolution, contrast and distortion) may all be taken within a small radiation field (12x12 cm², 100cm from the source), equivalent in size to the most frequently used area of the imager.
  • Measurement of the spatial resolution with a modern and accurate standardised method (ESF).

  • The contrast is evaluated by large targets and constant diameters to avoid tainting the measurement with distortions by noise, spatial resolution  or/and non-homogeneity of the signal.

  • All of the targets contained in OTP-EPID phantom are kept within a plastic matrix, which ensures that their orientation follows the divergence of the radiation beam, thereby providing objects whose contours remain distinct in the images.

  • The exterior surface of the test object is black and the alignment grooves are white, thereby facilitating alignment with the positioning lasers whatever their color.


Only 5 minutesis all the time you need to perform the entire image quality control: installation of the phantom, image acquisition and analysis with MOD-EPID module from QUALIMAGIQ platform software, yielding 6 different PDF analysis reports and trend curve for each tested parameter.


This phantom optimally fulfils all requirements of the French AFSSAPS decision dated 27/07/07 regulating Internal quality control of external radiation therapy installations: points 5.9.6 and 5.9.10 of the annex.


Compatible portal imagers:

  • All high energy (1 to 45 MV) portal imagers with an active surface wider than 25 x 25 cm².


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