C

Calibration

Calibration is the method for reducing the artifacts or making corrections of geometrical error of X-ray CT scan. It use water and air. If the air is used, it’s called as air calibration.

CAT Phantom

CAT phantom is a phantom that evaluates the performance of X-ray CT system.

Clipping

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

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

Compressed sampling is referred to Compressing sensing.

Cone Angle

During X-ray CT scan, the spread of the X-ray beam in the body axis direction (subject) is called cone angle. It is the angle used in cone-beam CT (CBCT).

Cone Beam Scanners (Rotation: CBCT)

Cone beam scanners are a type of CT scan that has rotational pass.

Read more Cone beam scanners (rotation) page.

Contrast Noise Ratio

CNR is the ratio of contrast to noise in image analysis obtained by X-ray CT and is an index of contrast resolution.

Contrast resolution

CPR (Curved Planer Reconstruction)

CPR (Curved planer reconstruction) is one of X-ray CT image display methods. This is a display method of extracting volume data from an arbitrary plane. Volume data can be extracted according to the running of a Shape (eg tubular shape, blood vessel etc.) impossible with MPR (Multi planer reconstruction). Cut out from the volume data with a curve or polygonal line.

CR Plate (CR Plate Profile)

CR plate is used to indicate the X-ray CT numbers on the horizontal line drown on the X-ray CT slice images. It shows the situation of the shape of the sample. It also call Profile.

CT

Computed Tomography. See the definition of X-ray CT.

CTDI (CT Dose Index)

CTDI is the index that describes irradiation ratio in X-ray CT scan.

CT Fluoroscopy

CT fluoroscopy is the technique that display X-ray CT image in real time.

CT needle aspiration biopsy (CT-NAB)

CT Number

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 X-ray CT scan. It also has the features for artifact reduction, focusing adjustment etc. X-ray 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 Soft

X-ray CT software

CT Software

CT software is refer to X-ray 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. X-ray CT software is called X-ray CT soft quite often.

Cupping Artifact

It is a type of artifact in X-ray CT images. It is also called cupping effect or beam-hardening problem. Please read the detail of cupping artifact page.

D

Detector

Detector is the equipment that get information of X-ray CT scan, then create the set of projection data. It refer to the flat panel detector.

Dynamic Range

Dynamic range is a term that express the range of brightness values that gradation of X-ray CT images, and is one of the items that show the performance of detectors(camera, flat panel).

If the dynamic range is wide, the image can be creates without losing the gradation information even if the X-ray transmission is too much or too little. However, if the dynamic range width is narrow, too much or too little X-ray transmission will result in loss or tone information and adversely affect the reproduced image. To be more specific, if the X-ray transmission is too high, overexposure will occur, and if the X-ray transmission is too low, blackout will occur. 

If the dynamic range is wide, a well-balanced gradation expression can be achieved. However, if the width of the dynamic range is narrow, it is expected that the gradation expression will be poor and the part to be captured will missing. Therefore, the importance of adjusting and selecting the dynamic range of the detector (camera, flat panel) is quite important. 

F

Fan Angle

During X-ray CT scan, the fan angle is the spread angle of the X-ray beam in the slice plane direction. It is the angle used for fan beam CT.

Fan / Line beam Scanner (Translation)

Fan/Line beam scanners is a type of X-ray CT scan system. Line scanners are the first generation of industrial X-ray 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 X-ray CT reconstruction software. Merit is you can use high voltage of X-ray, so that it penetrate through metal object easier, so that it gain high quality of slice images. Demerit is that scanning time is getting longer. 

Feldkamp Reconstruction

Feldkamp reconstruction is a method X-ray CT image reconstruction that considers come angle. From the 2000’s to the present (2015), it is the most used method in X-ray CT image reconstruction. It is also called FDK method.

File artifact

File artifact is an artifact that tends to occur when a substance with a high X-ray absorptivity exists in a certain projection direction in a certain subject area with X-ray CT scan. It is called a file-like artifact because it looks like a file (tool).

Filter Back Projection

Filter back projection is one method of image reconstruction. It changes the image quality by function changes.

FOV (Field of View)

FOV refers to the area/field of view.

Fourier Transform

Fourier transform is a data analysis method and is a method often used for image analysis relating to X-ray CT image analysis. How much resolution is required for one slice thickness (period), is a method to investigate the wave amplitude (wave height) of various frequencies. It is also called modulation transfer function.

Full Scan

Full scan is the type of reconstruction that it reconstructs all area of the entire sample image.

G

Gantry

Gantry is the part of X-ray 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 X-ray CT scan is conducted. Gantry is very common parts of medical X-ray CT.

Go and Go

Go and go is the scan method that X-ray CT scan the sample chronologically. It does X-ray CT scan same directions and axial direction of the sample repeatedly.

Go and Return

Go and return is the method that x-ray CT scan the sample chronologically. It does X-ray CT scan in both way toward of the axial direction of the sample repeatedly.

Gray Scale

Gray scale is a set of gray colored bars that shows the degree of the depth of gray color. On the software interface, it is located near to the CT images, and it is indicate the CT number of each gray depth of each gray color.

H

Half Scan

Half scan describe the type of X-ray CT scan method that do the X-ray CT scan half (180 degree). The total rotational angle is 180 degree + fan angle.

Hounsfield Unit 

Hounsfield number refers to CT number. It’s also called as Hounsfield Number. It is named after Sir Godfrey Newbold Hounsfield (1919-2004) who is British engineer, is known for the first person to built CT system. 

Helical Scan Artifact

Helical scan artifact is a type of artifact that is appeared 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 called as Step stair artifact.

I

Industrial X-ray CT (Computed tomography)

Industrial X-ray CT is the type of X-ray CT system that is particular used in industrial fields.

Read more Industrial CT(Computed tomography) page.

Isotropic

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.

Iterative Reconstruction (IR)

Iterative reconstruction (IR) is a X-ray CT image reconstruction method that has been newly developed and used in recent X-ray CT reconstruction methods.

This method is x-ray CT image reconstruction that has attracted attention especially in medical X-ray CT category, since it can reduce the exposure dose by 25 to 75% compared to conventional X-ray CT scan method and can reduce the exposure sate. In other advantage is that the number of X-ray CT images can be reduced as compared with the case of normal X-ray CT scan method, so that the imaging time can be reduced.

At present, the image quality of iterative reconstruction (IR) is said to be slightly inferior to the conventional methods, however it is said that there is no problem in determining the degree of exposure reduction according to the safety purpose. For example, in the case of ureter stones, even if the exposure is reduced by 75% or more, it is said that there is no problem in observing lung fields and ureter stones. It is also said that it’s possible to significantly reduce the amount of exposure even in the case of a X-ray CT scan using contrast agents.

Read more Iterative reconstruction (IR) function for TomoShop page.

J

K

L

Laminography

Laminography is a technique that combines 2D X-ray fluoroscopy and 3D CT, so it can be considered a 2.5-dimensional inspection. It is an effective method for inspecting flat samples such as printed circuit boards (PCBs), microchips (ICs), and BGAs. The X-ray radiation angle is not straight at the sample but is angled at less than 90 degrees.

M

Metal Artifact

Metal artifact is a type of noise that appear on the slice images of X-ray CT scan when the sample contains metals.

Read more Metal artifact page.

Misregistration

Misregistration is the noise that appeared when subtraction is applied to X-ray 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

Motion artifact is a type of noise of X-ray CT slice image. It appear when the sample is moved by accidentally during the X-ray 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 x-ray CT scanning, and do X-ray 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)

Conventionally, X-ray CT is a transverse image, however by obtaining multiple images in the body axis direction, it can be rearranged, sagittal, frontal disconnection and oblique disconnection also possible.

N

Non-destructive Testing (NDT)

Human society is surrounded by various natural items and artificial items. These natural and artificial items are destroyed by accidents or over-deteriorations and it causes various safety issues. Therefore, various inspections are necessarily to finding the causes of these destructions. Inspection is also important and contributing for developing the new technical and finding new academic things.

Non-destructive testing (NDT) is the one of those inspectional methods and it can be tested without destruction of the items. The main purposes of non-destructive testing are finding damaging areas, measuring the size, recognizing the shape/locations/characteristics/atmosphere etc. The methods of non-destructive testing are Radiographic testing (RT), Ultrasonic testing (UT), Magnetic particle Inspection (MPI), Penetrant inspection (PI) and Eddy-current testing (ECT). X-ray CT scan is belong to Radiographic testing (RT).

Neutron Tomography (Neutron CT)

It is a CT system by using neutron source. 

O

Offset Detector

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

Offset scan is the method that reconstruct the raw data set from the X-ray CT scan at the point that offset from the center point(rotational core point) of the sample.

Read more CT image Reconstruction page.

P

Partial Scan

Partial scan is the type of reconstruction that it only reconstructs the selected area of the entire sample image.

Read more CT Image Reconstruction page.

Partial Volume Effect

Partial volume effect is the situation that is difficult to distinguish the CT value within the minimum unit volume in the x-ray CT reconstruction image, which means that the correct CT value can not be obtained. And this partial volume effect causes blur on the periphery. It is appeared strongly when X-ray CT scan is done with thick slice thickness.

Pixel

Pixel is the minimum unit that makes up a 2D image. A pixel has one CT value.

Profile

Profile is used to indicate the CT numbers on the horizontal line drown on the X-ray CT slice images. It shows the situation of the shape of the sample. It also call CR plate/CR plate profile.

Proton Computed Tomography (Proton CT)

It is a CT by using proton beam.

Q

Quick Scan

Quick scan is a scan method that for performing a scan continuously prior to the image reconstruction.

R

Raw Data

Raw data is the 2D projection image data from X-ray 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 page.

Reconstruction

Reconstruction is the task that create 2D slice and 3DCG as the output data of X-ray CT scan from the set of raw data (projection data) done by the reconstruction software of X-ray CT system. It also called as image reconstruction.

Read more CT Image Reconstruction page.

Reconstruction factor

Ring Artifact

Ring artifact is a type of artifact that is not exist in the real situation.

Read more Ring artifact page.

ROI(Region of interest)

S

Scenography

Scan Pitch

Shading Artifact

Shading artifact is a type of artifact/noise related to X-ray CT that is caused by beam hardening phenomena.

Sinogram

Sinogram shows the output data from the detector at each projection that has been acquired at during the X-ray 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.

Slip ring

Slice sensitivity profile(SSPz)

Slice sensitivity profile(SSPz) is the sensitivity profile at z axis of the sample in X-ray CT image. Slice sensitivity profile will be the factors that determine the slice thickness.

Spatial Resolution

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.

Spiral CT Scan

Spiral CT scan is a method of X-ray CT scan that using spiral movement when the scan is conducted. It is often called as Helical CT scan, however some X-ray CT manufacture use deferent term for this, such as Volume CT scan (Hitachi).

Stair Step Artifact

Stair step artifact is one type of artifact in x-ray 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.

Streak Artifact

Streak artifact is a type of artifact that is not exist in the real situation.

Read more Streak artifact page.

Subtraction

Subtraction refer to the technique of displaying only the areas of interest in the created 3D or 2D slice images in X-ray 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

Surface rendering is a classic three-denominational display technology of X-ray 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 X-ray CT fields.

T

Three-dimensional CT

Three-dimensional CT is the most widely used X-ray CT scan method in recent years. This is the most commonly used X-ray CT scanning method because it can scan the entire sample in shorter time than the two-dimensional CT scanning method which is known as the previous generation of X-ray CT scan method. It is also called as cone-beam CT (CBCT). 

Three-dimensional Display

Three-dimensional display is to display the three-dimensional data by reconstructing the projection data after X-ray CT scan. Normally, it is composed of 2D slice images (axial section XY, coronal section XZ, sagittal section YZ) and 3D volume display. The image quality is determined by the conditions at the time of X-ray CT scanning, the number of axial sectional image, the degree of reduction of artifacts, etc. Panoramic display is a unique display method. Panoramic display method is often used in dental X-ray CT, but it is also in other X-ray CT system like industrial X-ray CT, since it is convenient to check multiple sections with one operation.

Time resolution

TSP (Temporal Sensitivity Profile)

TSP (Temporal resolution sensitivity) is an index that indicates how quickly imaging is possible, and in X-ray CT the scan time of the X-ray tube, or the time of projection data that contributes per image defined by the sensitivity distribution.

Two-dimensional CT

Two-dimensional CT is also called fan-beam CT. This is an old generation X-ray CT scan method. It is a method to scan two dimensionally by using line sensors etc. in the camera component. Scanning the entire sample takes a considerable amount of time, however compared to three-dimensional CT, the x-ray halation phenomenon, which causes metal artifacts or beam-hardening artifacts (cupping effect), is less likely to occur, so it is still popularly used for scanning narrow range or only a portion of the entire sample. 

U

V

Vertical Artifact

Vertical artifact is a type of noise that appears on the X-ray CT slice images. It is always appear along with ring artifact.

Read more Vertical artifact page.

Viewer

Viewer is the software or devices for analyzing image data from X-ray CT scan. Viewer screen is used to be the main tool for analyzing the X-ray CT images, however CRT is more popular to be used than viewer screen in recent years.

View Number

Viewer number is that number of RAW data that used for reconstructing the 3D X-ray CT image.

Volume Rendering

Volume rendering is a method of CG (Computer Graphic). In the past surface rendering used as the main method of X-ray CT inspection images. How ever, volume rendering is more popular than surface rendering in current times.

Read more Volume rendering page.

Voxel

Voxel is the minimum unit constituting a 3D image of volume image. The 3D display image used in X-ray 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.

W

Windmill Artifact

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

Window is the function of adjusting the CT number/value of X-ray CT slice images when the X-ray CT image inspection is taken. Window include Window level/value and Window width. It is important to adjust window correctly when the X-ray CT image inspection is taken.

Window Level / Value (WL)

Window level/value indicate the concentration of the CT number (CT value)

Window Width (WW)

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

Work station is the software or device that is for analyzing image data from X-ray CT scan with out the functions for X-ray CT image reconstruction. The reason for separating X-ray CT image reconstruction functions and image analyzing functions are due to the development of X-ray CT reconstruction functions, so that do the process of reconstruction separately from analyzing of the image.

X

X-ray

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.

X-ray inspection

Y

Z

Z Axis Filter