- 1 Glossary
- 1.1 A
- 1.2 B
- 1.3 C
- 184.108.40.206.1 Calibration
- 220.127.116.11.2 CNR(Contrast noise ratio)
- 18.104.22.168.3 Compression sensing
- 22.214.171.124.4 Compressed sampling
- 126.96.36.199.5 Cone beam scanners (rotation:CBCT)
- 188.8.131.52.6 CR plate (CR plate profile)
- 184.108.40.206.7 CTDI(CT dose index)
- 220.127.116.11.8 CT fluoroscopy
- 18.104.22.168.9 CT number
- 22.214.171.124.10 CT reconstruction software
- 126.96.36.199.11 CT soft
- 188.8.131.52.12 CT software
- 1.4 D
- 1.5 F
- 1.6 G
- 1.7 H
- 1.8 I
- 1.9 J
- 1.10 K
- 1.11 L
- 1.12 M
- 1.13 N
- 1.14 O
- 1.15 P
- 1.16 Q
- 1.17 R
- 1.18 S
- 1.19 T
- 1.20 U
- 1.21 V
- 1.22 W
- 1.23 X
- 1.24 Y
- 1.25 Z
Glossary page of CT
Axial intensity drop
Axial intensity drop is a type of artifact in Cone-beam CT(CBCT) image. In CBCT, since the mechanism structure of CBCT, obtaining data is insufficient to meet with creating accurate reconstruction image in the image reconstruction stage. The most popular algorithm for CBCT reconstruction is FDK. Using FDK algorithm, axial intensity drop is always occurred.
Axial intensity drop is that the middle areas of sample image are accurate, however the top side areas and the bottom side areas are not accurate.
Our CT software, TomoShop® has the solution to reduce the axial intensity drop.
See ☞ CT Image Reconstruction
Actual detector is an element in the development of views. It is the locus of the actual detector.
After grow is a phenomenon that occurs in relation to spatial resolution. Since detector will emit the lite in response to the X-ray, but this reaction is slow and the state also has the light-emitting time on the next data.
Air gap method
Air gap method is one way to measure the slice sensitivity profile(SSPz). It’s done by creating a thin gap between the acyclic, and is a method of finding a slice sensitivity profile(SSPz) in the negative direction.
Ordinal way of the calibration is done using the water. However, air gap calibration is done simply using air. Air calibration is done when CT system is starting and it done in conjunction with the warm-up process.
Artifact is the word for include all noises appear on the slice image data from CT scan.
Read more ☞ Artifact
Bead phantom is one way to measure the slice sensitivity profile(SSPz). It is determined from a plurality of images obtained by CT scanning the small sphere phantom.
Beam hardening correction
Beam hardening correction is the method/function to reduce beam hardening phenomena.
read more ☞ Beam hardening correction
Beam hardening effect
Beam hardening effect is a type of noise that appear on the slice images of CT scan.
read more ☞ Beam hardening effect
Calibration is the method for reducing the artifacts or making corrections of geometrical error of CT scan. It use water and air. If the air is used, it’s called as air calibration.
CNR(Contrast noise ratio)
CNR(Contrast noise ratio) is the ratio that contrast against noise in image inspection. It is also known as contrast resolution.
Compression sensing is a method of restoring objects under certain conditions from observation data that is less than the number of required unknowns, assuming that the observation target data is sparse signal. A signal with sparsity is a signal whose majority of the signal component becomes 0 by applying linear transformation. If the signal has sparsity, it is an image technology that restores the original signal from a small number of sampled data or insufficient sample number data.
An advantage obtained by using the compression sensing technique in the field of X-ray CT is that the object can be reconstructed in a state where the number of projections of X-rays (number of images to be shot) is small. It is expected to eliminate the necessity of photographing from the surrounding direction, narrowing the area to be irradiated with X rays, etc. It is expected to contribute to reducing the exposure dose and downsizing the device. Applications of compression sensing include medical images (speeding up with X-ray CT and improving resolution), image processing (sharpening of out-of-focus images), and the like.
Compressed sampling is referred to Compressing sensing.
Cone beam scanners (rotation:CBCT)
Cone beam scanners are a type of CT scan that has rotational pass.
Read more ☞ Cone beam scanners (rotation)
Contrast noise ratio
CR plate (CR plate profile)
CR plate is used to indicate the CT numbers on the horizontal line drown on the CT slice images. It shows the situation of the shape of the sample. It also call Profile.
CTDI(CT dose index)
CTDI is the index that describes irradiation ratio in CT scan.
CT fluoroscopy is the technique that display CT image in real time.
CT needle aspiration biopsy (CT-NAB)
Index value of X-ray absorption rate.
CT reconstruction software
CT reconstruction software is that create 2D slice and 3D images from the set of projection data from CT scan. It also has the features for artifact reduction, focusing adjustment etc. CT reconstruction software used to only has tools in relation of reconstruction tasks, however recently it has also volume visualization tools and measure & analysis tools.
CT software is refer to CT reconstruction that do the reconstruction task to create 2D slice and 3D images from the projection data set of CT scan along with artifact reduction tools, adjustment and correction of focusing tools, etc. CT software is called CT soft quite often.
Detector is the equipment that get information of CT scan, then create the set of projection data. It refer to the flat panel detector.
Fan/line beam scanner (translation)
Fun/Line beam scanners is a type of CT scan system. Line scanners are the first generation of industrial CT Scanners. X-rays are produced and the beam is collimated to create a line. The X-ray line beam is then translated across the sample object and data is collected by the detector. The data is then reconstructed to create a 3D Volume rendering of the sample object by CT reconstruction software.
Filter back projection
Filter back projection is one method of image reconstruction. It change the image quality by function changes.
FOV(Field of view)
FOV refers to the area/field of view.
Full scan is the type of reconstruction that it reconstructs all area of the entire sample image.
Gantry is the part of CT machine that is tunnel shape and has the x-ray source generator and the detector. The samples are put through the tunnel of the gantry when CT scan is conducted. Gantry is very common parts of medical CT.
Go and go
Go and go is the scan method that CT scan the sample chronologicaly. It does CT scan same directions and axial direction of the sample repeatedly.
Go and return
Go and return is the method that CT scan the sample chronologicaly. It does CT scan in both way toward of the axial direction of the sample repeated ly.
Gray scale is a set of gray colord bars that shows the degree of the depth of gray color. on the softare interface, it is located near to the CT images, and it is indicate the CT number of each gray depth of each gray color.
Half scan describe the type of CT scan method that do the CT scan half (180 degree). The total rotational angle is 180 degree + fan angle.
Helical scan artifact
Helical scan artifact is a type of artifact that is apperared with helical scan. The cause of helical scan artifact are Windmill artifact and increasing the gap of 3D reconstruction image parts. Helical artifact is also caled as Step stair artifact.
Industrial CT(Computed tomography)
Industrial CT is the type of CT system that is particular used in industrial fields.
Read more ☞ Industrial CT(Computed tomography)
Isotropic is the situation that all directions of spatial resolution are equal. In other word to say that the size of the pixel and thickness of the slice are equal.
Metal artifact is a type of noise that appear on the slice images of CT scan when the sample contains metals.
Read more ☞ Metal artifact
Misregistration is the noise that appeared when subtraction is applied to CT image processing. overcoming the misregistration is important factor for getting better image result when subtraction is applied.
The method of inspecting misregistration is not completed yet, however there is one example that uses special phantom for it.
Motion artifact is a type of noise of CT slice image. It appear when the sample is moved by accidentally during the CT scan is taken. It is very difficult to reduce motion artifact, therefore, it is better to set the sample to be fixed to make sure that not moving during the CT scanning, and do CT scan it again.
MTF(Modulation transfer function)
MTF is the effect related to spatial frequency. It is used to evaluate the spatial resolution.
MPR(Multi planer reconstruction)
Offset detector is a technique for improving the spatial resolution. In the process or offset technique, shifting 1 of 4 minutes from the center of rotation of the detector and it occur projection data to be facing different and it enable to increase collection data, thus it improve the spatial resolution of the collected image data.
Offset scan is the method that reconstruct the raw data set from the CT scan at the point that offset from the center point(rotational core point) of the sample.
Read more ☞ CT image Reconstruction
Partial scan is the type of reconstruction that it only reconstructs the selected area of the entire sample image.
Read more ☞ CT Image Reconstruction
Partial volume effect
Partial volume effect is the situation that is difficalt to distinguish the CT value within the minimum unit volume in the CT reconstruction image, which means that the correct CT value can not be obtained. And this partial volume effect causes blur on the peripehery. It is appeared strongly when CT scan is done with thick slice thickness.
Pixel is the minimum unit that makes up a 2D image. A pixel has one CT value.
Profile is used to indicate the CT numbers on the horizontal line drown on the CT slice images. It shows the situation of the shape of the sample. It also call CR plate/CR plate profile.
Quick scan is a scan method that for performing a scan continuously prior to the image reconstruction.
Raw data is the 2D projection image data from CT system that before reconstruction is taken.
Ray casting method
Ray casting method is a type of volume rendering method. It is well showing the small details of natural shape that is not geometric shape. Our CT software: TomoShop® series use ray casting method for 3DCG.
Read more ☞ Volume Visualization
Reconstruction is the task that create 2D slice and 3DCG as the output data of CT scan from the set of raw data (projection data) done by the reconstruction software of CT system. It also called as image reconstruction.
Read more ☞ CT Image Reconstruction
Read more ☞ Ring artifact
ROI(Region of interest)
Shading artifact is a type of artifact/noise related to CT that is caused by beam hardening phenomena.
Sinogram shows the output data from the detector at each projection that has been acquired at during the CT scan is conducting. The each projection position is called as projection and the output data from the detector is called as channel. In general, Y-axis is called as projection and X-axis is called channel.
Slice sensitivity profile(SSPz)
Slice sensitivity profile(SSPz) is the sensitivity profile at z axis of the sample in CT image. Slice sensitivity profile will be the factors that determine the slice thickness.
Spatial resolution is one of the indicator of the quality of images. it is the indicator of whether it is possible to be recognized of how much of the little things in the large scale of CT number difference. It also described as the ability of recognition of the difference between 2 points that are standing very narrow distance in the image.
Stair step artifact
Stair step artifact is one type of artifact in CT image that particularly it can be found in helical CT scan.
Stair step artifact can occur due to the occurrence of windmill artifact and expansion of image reconstruction interval.
Subtraction refer to the technique of displaying only the areas of interest in the created 3D or 2D slice images in CT field. There is one interesting part among many other parts, however the other parts disturb to see the part you want to see, so that you remove the other parts from the image to see the part you want to see.
Surface rendering is a classic three-denominational display technology of CT image reconstruction. It is a way to distinguish the CT value at the threshold. Currently volume rendering if replaced to surface rendering that is seemed to be no longer to use in CT fields.
TSP(Time sensitivity profile)
Vertical artifact is a type of noise that appears on the CT slice images. It is always appear along with ring artifact.
Read more ☞ Vertical artifact
Viewer is the software or deveices for analysing image data from CT scan. Viewer screen is used to be the main tool for analysing the CT images, however CRT is more populer to be used than viewer screen in recent years.
Viewer number is that number of RAW data that used for reconstructing the 3D CT image.
Volume rendering is a method of CG(Computer Graphic). In the past surface rendering used as the main method of CT inspection images. How ever, volume rendering is more popular than surface rendering in current times.
Read more ☞ Volume rendering
Voxel is the minimum unit constituting a 3D image of volume image. The 3D display image used in CT is created by reconstructing based on the set of pixel images.
A voxel is a state in which depth(Z direction) is added to one pixel. Therefore, it is a completely different concept from the 3D image of dynamic pixels used in CAD and others.
Windmill artifact is a type of artifact that is found particularly in the helical CT scan and its shape is look like spiral shape.
The cause of windmill artifact is the problem in the interpolation calculation by increasing the helical pitch in the helical CT scan.
Window is the function of adjusting the CT number/value of CT slice images when the CT image inspection is taken. Window include Window level/value and Window width. It is important to adjust window correctly when the CT image inspection is taken.
Window level/value indicate the concentration of the CT number(CT value)
Window width is the concentration area of window level. Window level is the point and Window width is the area that Window level are there.
Work station is the software or device that is for analysing image data from CT scan with out the functions for CT image reconstruction. The reason for separating CT image reconstruction functions and image analyting functions are due to the development of CT reconstruction functions, so that do the process of reconstruction separately from anlysing of the image.
X-ray is an electromagnetic wave that has wavelength of around 10-12 to 10-8m(0.01 to 100Å). The absorption of X-rays by an object depends on the wavelength of the X-ray to be used, the thickness of the object, the type of the element constituting the object, and their ratio.
X-ray transmission method
The X-ray transmission method is a method of observing the internal structure of an object by utilizing the difference in X-ray transmission force. The penetration power of X-ray increases as the wavelength is shorter. Also, if the atomic numbers of the elements that makes up the object are small or the thickness is thin, X-ray will penetrate well.
In general, short wavelength X-rays are hard and long wavelength X-rays are expressed as soft. The hard X-rays with many short wavelength components are generated if the higher the voltage applied to the X-ray generator. Soft X-rays are used to examine the material composed of light elements, such as living organisms. On the other hand, hard X-rays are generally used when inspecting hard substances such as iron.
X-ray CT scanning system, X-ray fluoroscopic system, X-ray photograph etc use the technology that explained above (X-ray absorption phenomenon, the usage of continuous X-ray). X-ray spectroscopy (emission of florescent X-rays) and X-ray analysis (scattering phenomenon of X-ray) are available other than the X-ray transmission method by the measurement method using X-rays.
Z Axis Filter