Does anyone know anything about x-ray microtomography?

Clark H

Hello! Please help me and my group with our assignment at uni! We have been asked to write a 3-page essay about x-ray microtomography. But it seems rather difficult to find information about that topic on the internet and in published texts. We would like any information available! Thanks a lot!

Answer
Microtomography, like tomography, uses x-rays to create cross-sections of a 3D-object that later can be used to recreate a virtual model without destroying the original model. The term micro is used to indicate that the pixel sizes of the cross-sections are in the micrometer range. This also means that the machine is much smaller in design compared to the human version and is used to model smaller objects.

These scanners are typically used for small animals (in-vivo scanners), biomedical samples, foods, microfossils, and other studies for which minute detail is desired.

The first X-ray microtomography system was conceived and built by Jim Elliott in the early 1980s. The first published X-ray microtomographic images were reconstructed slices of a small tropical snail, with pixel size about 50 micrometers. (JC Elliott and SD Dover. X-ray microtomography. J. Microscopy 126, 211-213, 1982.)

In 2005, Skyscan, a company that produces scientific instruments, introduced a nano-ct scanner, introducing the concept of Nanotomography. Other companies producing such scanners include Xradia for materials and semiconductor applications and Scanco Medical AG for medical applications.

Working principle

* Imaging system

Fan beam reconstruction
The fan-beam system is based on a 1-dimensional x-ray detector and an electronic x-ray source, creating 2-dimensional cross-sections of the object. Typically used in human Computed tomography systems.
Cone beam reconstruction
The cone-beam system is based on a 2-dimensional x-ray detector (camera) and an electronic x-ray source, creating projection images that later will be used to reconstruct the image cross-sections.

* Sample holder system

The sample stays still, and the camera and electronic x-ray source rotates.
This is best used for in-vivo animal scans, and other situations where the sample should remain unmoving, but is more expensive.
E.g.SkyScan-1076 or SkyScan-1078 or Scanco VivaCT 40 scanners for sample details.
The sample rotates, and the camera and electronic x-ray source stays still.
Much cheaper to build, since moving the sample requires fewer components than moving the camera and the electronic x-ray source.

* Open/Closed systems

Open x-ray system
In an open system, x-rays may escape or leak out, thus the operator must stay behind a shield, have special protective clothing, or operate the scanner from a distance or a different room. Typical examples of these scanners are the human versions, or designed for big objects.
E.g. Scanco medical XtremeCT scanner.
Closed x-ray system
In a closed system, x-ray shielding is put around the scanner so the operator can put the scanner on his desk or special table. Although the scanner is shielded, care must be taken and the operator usually carries a dose meter, since x-rays have a tendency to be absorbed by metal and then re-emitted like an antenna. Although a typical scanner will produce a relatively harmless volume of x-rays, repeated scannings in a short timeframe could pose a danger.
Closed systems tend to become very heavy because lead is used to shield the x-rays. Therefore, the smaller scanners only have a small space for samples.
E.g. SkyScan-1076 or SkyScan-1078 or Scanco mCT 40 or Scanco mCT 80 scanners

Typical use
* Biomedical

* Both dead and alive (in vivo) rat and mouse scanning.
* Human skin samples, small tumors, mice bone for osteoporosis research.

See in vivo microCT scanners for scanning examples.

* Electronics

Small electronic components. E.g. DRAM IC in plastic case.

* Microdevices

E.g. spray nozzle

* Composite materials and metallic foams

E.g. composite material with glass fibers 10 to 12 micrometres in diameter

* Polymers, plastics

E.g. plastic foam

* Diamonds

E.g. detecting defects in a diamond and finding the best way to cut it.

* Food and seeds

* E.g. piece of chocolate cake, cookies
* 3-D Imaging of Foods Using X-Ray Microtomography [1]

* Wood and paper

E.g. piece of wood to visualize year periodicity and cell structure

* Building materials

E.g. concrete after loading.

* Geology

E.g. sandstone

* Microfossils

E.g. bentonic foraminifers

* Space

E.g. Locating Stardust-like particles in aerogel using x-ray techniques [2]

* Others

E.g. cigarettes

* Stereo images

Visualizing with blue and green or blue filters to see depth

What are the airport body scanners?

Q. I've been hearing a lot about them. Does your body show up naked or is it an x-ray image. Or what?

Answer
the newest scanners can produce a 3D image of you entire body highlighting any abnormalities being carried on your person.

Powered by Yahoo! Answers

How does the CT SCAN,MRI,and PET scanners can help to diagnose some disease of the reproductive system?

ck

Answer
Each one provides a different way to construct a 3D image of internal organs. Because they use different physical phenomena, they detect different aspects of the body's structure and function.

CT scans are regular X-rays. They do best at finding dense tissues, especially bones and some kinds of tumors. Doctors sometimes use dyes that show up on X-rays to add contrast to images of soft tissue. MRI interacts with the hydrogen atoms in body tissues, and senses some features of the chemical environment at each point in the body. PET always uses a slightly radioactive dye, and measures where the dye goes. For example, PET sometimes uses a sugar-based dye, and detects which parts of the body or brain consume that sugar - this measures energy consumption. Other dyes accumulate in different parts of the body, for different chemical reasons.

tell me the difference :)?

I AM VIETN

Between normal X-ray technology and Computed Tomography used in hospital , especially about Computer Function of CT
thanks
------------------------------------------------------------------------------------------
Small suggestion :)
Are you having blog , could you invite me as your friend :)

Answer
Standard x-rays are simple images similar to photographs taken in the X-ray spectrum of light.

Computed tomography (CT), originally known as computed axial tomography (CAT or CT scan) and body section roentgenography, is a medical imaging method employing tomography where digital geometry processing is used to generate a three-dimensional image of the internals of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation. The word "tomography" is derived from the Greek tomos (slice) and graphia (to write). CT produces a volume of data which can be manipulated, through a process known as windowing, in order to demonstrate various structures based on their ability to block the X-ray beam. Although historically the images generated were in the axial or transverse plane (orthogonal to the long axis of the body), modern scanners allow this volume of data to be reformatted in various planes or even as volumetric (3D) representations of structures.

Although most common in healthcare, CT is also used in other fields, for example nondestructive materials testing.


Advantages Over Projection Radiography

First, CT completely eliminates the superimposition of images of structures outside the area of interest. Second, because of the inherent high-contrast resolution of CT, differences between tissues that differ in physical density by less than 1% can be distinguished. Third, data from a single CT imaging procedure consisting of either multiple contiguous or one helical scan can be viewed as images in the axial, coronal, or sagittal planes, depending on the diagnostic task. This is referred to as multiplanar reformatted imaging.


Regarding your question about the computing portion, X-ray slice data is generated using an X-ray source that rotates around the object; X-ray sensors are positioned on the opposite side of the circle from the X-ray source. Many data scans are progressively taken as the object is gradually passed through the gantry. They are combined together by the mathematical procedure known as tomographic reconstruction.

Newer machines with faster computer systems and newer software strategies can process not only individual cross sections but continuously changing cross sections as the gantry, with the object to be imaged, is slowly and smoothly slid through the X-ray circle. These are called helical or spiral CT machines. Their computer systems integrate the data of the moving individual slices to generate three dimensional volumetric information (3D-CT scan), in turn viewable from multiple different perspectives on attached CT workstation monitors.
CT scanner with cover removed to show the principle of operation
CT scanner with cover removed to show the principle of operation

In conventional CT machines, an X-ray tube and detector are physically rotated behind a circular shroud (see the image above right); in the electron beam tomography (EBT) the tube is far larger and higher power to support the high temporal resolution. The electron beam is deflected in a hollow funnel shaped vacuum chamber. X-rays are generated when the beam hits the stationary target. The detector is also stationary.

The data stream representing the varying radiographic intensity sensed reaching the detectors on the opposite side of the circle during each sweep is then computer processed to calculate cross-sectional estimations of the radiographic density, expressed in Hounsfield units. Sweeps cover 360 or just over 180 degrees in conventional machines, 220 degrees in EBT.

CT is used in medicine as a diagnostic tool and as a guide for interventional procedures. Sometimes contrast materials such as intravenous iodinated contrast are used. This is useful to highlight structures such as blood vessels that otherwise would be difficult to delineate from their surroundings. Using contrast material can also help to obtain functional information about tissues.

Pixels in an image obtained by CT scanning are displayed in terms of relative radiodensity. The pixel itself is displayed according to the mean attenuation of the tissue(s) that it corresponds to on a scale from -1024 to +3071 on the Hounsfield scale. Pixel is a two dimensional unit based on the matrix size and the field of view. When the CT slice thickness is also factored in, the unit is known as a Voxel, which is a three dimensional unit. The phenomenon that one part of the detector cannot differ between different tissues is called the Partial Volume Effect. That means that a big amount of cartilage and a thin layer of compact bone can cause the same attenuation in a voxel as hyperdense cartilage alone. Water has an attenuation of 0 Hounsfield units (HU) while air is -1000 HU, cancellous bone is typically +400 HU, cranial bone can reach 2000 HU or more (os temporale) and can cause artefacts. The attenuation of metallic implants depends on atomic number of the element used: Titanium usually has an amount of +1000 HU, iron steel can completely extinguish the X-ray and is therefore responsible for well-known line-artifacts in computed tomogrammes.

Powered by Yahoo! Answers

How far is the automated 3-D segmentation of Brain MRI efficient compared to manual segmentation?

3d x ray scanner image

Sandhya

We are doing a project on automated 3-D segmentation of brain MRI using MATLAB. We would like to know the extent to which "Surf" commands are efficient in producing reliable segmented 3-D image. The accuracy level, how much it is better compared to manual segmentation. We need statistical detail, kindly help us....

Answer
This correspondence deals with the development of an
automated 3-D segmentation of Brain MRI. The proposal is a
model-based approach for accurate, robust, and automated
tissue segmentation of brain MRI data of single as well as
multiple magnetic resonance sequences. The main contribution
of this study is that we employ an edge-based geodesic active
contour for the segmentation task by integrating both image
edge geometry and voxel statistical homogeneity into a novel
hybrid geometricâstatistical feature to regularize contour
convergence and extract complex anatomical structures. We
validate the accuracy of the segmentation results on simulated
brain MRI scans of both single T1-weighted and multiple T1/
T2/PD-weighted sequences. When compared to a current stateof-
the-art region based level-set segmentation formulation,
our white matter and gray matter segmentation resulted in
significantly higher accuracy levels with a mean improvement
in Dice similarity indexes. Thus the development of the project
is done using MATLAB simulation for results.
A Hybrid Automated 3D Segmentation in Brain MRI -------------------------------------------------------- Advantages of a MRI scan
⢠MRI scanners are good at looking at the non-bony parts
or "soft tissues" of the body. In particular, the brain, spinal
cord and nerves are seen much more clearly with MRI
than with regular x-rays and CAT scans.
⢠Also, muscles, ligaments and tendons are seen quite well
so that MRI scans are commonly used to look at knees
and shoulders following injuries.
⢠A MRI scanner uses no x-rays or other radiation.
⢠A disadvantage of MRI is itâs higher cost compared to a
regular x-ray or CAT scan. Also, CAT scans are frequently
better at looking at the bones that MRI.

Please name companies that makes Cone Beam CT Scanning Equipment?

Mr. USA

I am looking for a CBCT equipment that would allow me to create 3D images from the scans. I need an integrated CBCT and 3D facility. I also need a handheld CT scanner. Prices? List of manufacturers, too. Thank you, kindly.

Answer
You can view and dowload a presentation of CBCT manufacturers at Scribd. A web link to each vendor's website is included.
http://www.scribd.com/doc/14048324/Cone-Beam-CBCT-Scanners-April-2009

A growing directory of customers for CBCT scanners is located here:
http://knol.google.com/k/murry-shohat/cbct-x-ray-services-directory/2srzofgvr8kjr/12#

Powered by Yahoo! Answers