Focusing technology

Focusing technology is used in order to reduce the artifacts that occur geometric error on the hardware equipment.

TomoShop® extract geometry error automatically that occur in hardware equipment by focusing technology and high versatility of Omni back-projection technology, then it reduces the artifacts of reconstructed images. It is done by GPU with high-speed computing technology.

Focusing process can be done by minimizing the size of data of reconstruction images and Image quality evaluation function that caliber based on group theory (mathematical programming) optimization mathematically.

There was a method using Entropy function with Information theory [1]. However, it loses uniqueness of minimum value and reduces stability of optimization algorithm, which is shown below.


Change in Entropy method (no noise)


Change in Entropy method (with noise)

TomoShop® can reduce artifact with setting the evaluation function even if there are noises, so that the optimization algorithm converges to robust images and bring more accurate assessment of geometric errors that occurred.


Changes in TomoShop®’s evaluation function (no noise)


Changes in TomoShop®’s evaluation function (with noise)

Marker Focusing Correction

The marker focusing correction manually detects the position of the sample / part in the projected image data from multiple directions and corrects the start-up error during CT scan of the detector, stage, and X-ray source.

When using this function, it is possible to correct the troublesome random machine error (random machine operation error) by placing a marker (sphere) near / part of the sample and taking a picture.

The correction value acquired at this time can be used most for CT scanning of other samples with similar conditions or when using the same device for correction.

Random machine error caused by machine vibration etc.

Since the marker (sphere) is a circle on the image, lock on the center of the circle to correct it.

Comparison of before and after of the correction 1

**The example below is that the scanning is done with markers (spheres).

Before

After

The comparison of before and after the correction 2

**The example below is that the scanning is done with markers (spheres).

Before

After

The marker focusing correction technology uses OpenCV to detect the center of a circle, accurately estimate the three-dimensional position of each marker and its motion error, and issue a correction value to correct it.

 

[1] Y. Kyriakou, R.M. Lapp, L. Hillebrand, D. Ertel and W.A. Kalender, Simultaneous Misalignment Correction for Approximate Circular Cone-Beam Computed Tomography, Phys. Med. Biol. Vol. 53, No. 22, pp. 6267-6289, 2008.