YY/T 0890-2013Electronic portal imaging device using in radiotherapy—Functional performance characteristics and test methods (English PDF)

3.1 Electronic imaging device; EID

It refers to the equipment that is composed of one or more radiation detector(s) and relevant electronic components, which can display the anatomical structures of patients in the form of digital radiation images on the viewing screen for observation.

Note: SEE also 3.2 of this edition.

3.2 Electronic portal imaging device; EPID

It refers to the equipment that is composed of one two-dimensional radiation detector and relevant electronic components, and using the radiation beams of the medical electron accelerator as radiation source, which is placed perpendicular to the radiation beam axis, and can display the anatomical structures of patients in the form of digital radiation images on the viewing screen for observation.

3.4 Spatial resolution

It refers to the line pair groups with minimum spatial frequency for the specified line groups of graphic images that can be distinguished by means of eyesight under specified measuring conditions, in unit of lp/mm.

4.1 General requirements

If the parameters and/or conditions of the electronic imaging device may not apply to or cannot meet the requirements specified in this chapter, the accompanying files shall describe these exceptions in details, and shall explain the parameters and/or conditions applicable to this electronic imaging device.

4.3 Requirements for imaging performance

4.3.1 Detector area and pixel pitch

The detector area and pixel pitch of the electronic portal imaging device shall be given in the accompanying files. The detector area shall be given in unit of cm2, while the pixel pitch shall be given in unit of mm. Furthermore, the pixel pitch can also be represented by pixel size.

4.3.4 Detector frame time

The minimum frame time corresponding to the maximum frame frequency (frames/s) shall be given in the accompanying files. The minimum frame time of the detector shall not be greater than 0.5s, while the corresponding maximum frame frequency shall not be less than 2 frames/s.

4.3.5 Signal-to-noise ratio (SNR) and dynamic scope of imaging device

4.3.5.1 The signal-to-noise ratio corresponding to the dose shall be given in the accompanying files, and shall be expressed as percentage or decibels. The dynamic scope shall be given in unit of decibel.

4.3.5.2 For the dose of 1cGy, the signal-to-noise ratio shall not be less than 5,000%.

4.3.8 Spatial resolution of imaging devices

For a given set of imaging conditions (energy, dose monitoring count, and detector frames), when imaging a phantom with a contrast test card located on the EID surface, the distinguishable modulation transfer function (MTF) of the maximum spatial frequency function shall be given in the accompanying files by manufacturers.

4.3.9 Low contrast resolution

The low contrast resolution shall be given in the accompanying files by manufacturers, and shall not be less than the numerical value specified by manufacturers.

4.3.10 Image distortion

The image distortion shall be specified in the accompanying files by manufacturers, and shall not be less than the numerical value specified by manufacturers.

5.1 Test conditions

The required parameters of image acquisition are interrelated, which shall be given together. If it is allowed to adjust the relevance to these parameters for the design of electronic imaging devices, the following 4 parameters shall be repeatedly combined with each other to achieve various kinds of typical settings.

5.2 Mechanical support structure

5.2.1 CHECK the accompanying files and the scope of mechanical movement for radiation field devices, which shall conform to the requirements given in the accompanying files.

5.3 Electronic portal imaging

5.3.1 Detector area and pixel pitch

CHECK the accompanying files, which shall conform to the requirements specified in the Article 4.3.1.

5.3.2 Detector characteristics

CHECK the accompanying files, which shall conform to the requirements specified in the Article 4.3.2.

5.3.3 Number of visible pixels

CHECK the accompanying files, which shall conform to the requirements specified in the Article 4.3.3.

5.3.7 Linearity of imaging devices

5.3.7.1 Aluminum ladder or copper ladder method

5.3.7.1.1 Phantom

The phantom consists of aluminum ladder or copper ladder. The phantom with maximum thickness shall absorb more high-energy photons than the water with 30cm thickness. The gray-scale difference corresponding to the thickness of each ladder shall be equal. The ladder grade shall not be less than Grade 5.

5.3.8 Spatial resolution of imaging devices

PLACE the line-pair phantom at the center of radiation beams. The phantom shall be close to the image receiving surface as far as possible. OBTAIN the images.

5.3.9 Low contrast resolution

5.3.9.1 Phantom

The low-contrast phantoms are obtained by digging holes with the diameter of 0.5mm to 15mm on the aluminum or copper products with certain thickness. The hole depth shall be proportional to the material thickness.

5.3.9.2 Test methods

PLACE the low-contrast phantom at the center of radiation beams. The phantom shall be close to the image receiving surface as far as possible. OBTAIN the images. […]

5.3.10 Image distortion