DSA performance testing module

1、 Overview:

1. Main body: PMMA board;

2. A wedge-shaped copper ladder with a dynamic range of 7 levels: 7 linear copper wedge-shaped ladders with thicknesses ranging from 0.2 mm to 1.4 mm are placed in the longitudinal direction of the plug, and another set of copper ladders with thicknesses ranging from 1.4 mm to 0.2 mm is used for logarithmic compensation testing.

3. Vascular simulation board plugin: It can move horizontally by 10mm and comes with four aluminum strips with a simulated vascular density of at least 99.5% purity. The plugin body has a length of 160mm, a thickness of 10mm, and a width of 170mm.

4. Vascular simulation board plug-in: equipped with 4 aluminum strips with a purity of 99.5%, with a gap of 15mm between the aluminum strips. The aluminum strips are 160mm long, 5mm wide, and have thicknesses of 0.05mm, 0.1mm, 0.2mm, and 0.4mm, respectively, used to simulate different vascular densities.

5. The 6-meter long remote control pneumatic valve causes the vascular simulation board to move in different directions during the detection process.

2、 Testing items:

detectionThe realistic contrast range, resolution, linearity, uniformity, amplifier dynamic range, registration accuracy, and subtraction effect of DSA system are quantitatively measured for high contrast and low contrast spatial resolution.

2、 Usage:

1.turn DSA phantom placed on the bed surface

2. Minimize the distance between the focus and the image receiver

3. Adjust the size of the light field to the mark on the phantom; It is best not to directly irradiate the image receiver

4. Start subtraction and create a mask (the basic image before medication is the mask)

5. Press the balloon, and the slider of the DSA phantom will move

6. Continue subtraction and simulate the medication process of contrast imaging

7. Subtracting the mask from the image after medication is the DSA image at this time

3、 Dynamic range

Definition: Dynamic range is the maximum difference in dose that an image receiver can display (e.g. when the dose is particularly small, it cannot be displayed on the image receiver even if it is small). It is precisely because image receivers have different responses to different doses that subtraction imaging becomes possible.The attenuation body of the DSA module is 57mm organic glass (PMMA), combined with copper steps of different thicknesses (0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 0.2 mm Cu).

Detection process: Start subtraction(Recommendation rate greater than 1 ton per second, lead time greater than 20 seconds), do not move the slider.

Result evaluation: All copper steps on the base imageThe mask should be visible, and a copper step image with a thickness of 1.4mm should be seen on the subtraction image.

4、 Artifact

Definition: Interference images should not appear on subtraction images. The ideal subtraction should only have the difference between mask and post medication imaging(i.e. blood vessels) are displayed.

Detection process: Start subtraction, do not move the slider, frame rate greater than1 frame per second, lasting for more than 20 seconds.

Result evaluation: If there are artifacts, they should be marked (pay attention to the edges of the copper steps)

5、 Comparison sensitivity

definition:The ability of DSA system for low contrast vascular imaging involves simulating blood vessels with aluminum strips of different thicknesses (0.4, 0.2, 0.1, 0.05 mm AI) on the slider of the DSA phantom. Under typical dose conditions (approximately 5uGy per frame), the thinnest aluminum strip should be visible on the subtraction image.

Detection process: Start subtraction, move the slider to obtain subtraction images

Result evaluation: The thinnest aluminum strip(0.5mm Al) should be visible on 0.8mm copper steps. If this requirement cannot be met, the exposure dose should be evaluated. If the dose is lower than the reference dose, it is also acceptable that the thinnest aluminum strip cannot be displayed on a 0.8mm copper step.

6、 Nonlinear compensation reduction(Regarding errors)

definition: The attenuation of X-rays is non-linear and depends on the density and thickness of the object. The attenuated image becomes linear after logarithmic gain processing by the system.

Detection process: The detection process is the same as the contrast sensitivity, and the results can be directly detected using the contrast sensitivity.

Result evaluation: From If the brightness difference in the subtraction image is visible from a 1.4mm copper step to a 0.2mm copper step, it indicates that there is an error in the logarithmic gain (nonlinear attenuation compensation).