Optical CT

Optical CT

Optical CTAndrew ONeill

Dt260/3

Supervised by Justin Donnelly

Computed TomographyA technique for displaying a representation of a cross section through a human body or other solid object using X-rays or ultrasound which then is reconstructed by a computer.

Origin of CT scanGodfrey Hounsfield (1919-2004) Invented the CT. He came up with the Idea that one could determine what is inside a object by taking x-rays at all angles around the object. He constructed a computer that could take the input of the x-rays at various angles and create an image of the object in slices.

Evolution of CT1St Generation (Basic beam and detector which ran slowly and required multiple translations)

2nd Generation had multiple detectors and a fan beam which was quicker but still required translation.

2nd Generation CT

Fan beam with multiple rotating detectors which meant translation wasnt needed. Much faster 0.5s per rotation.3rd Generation CT

Fan beam exactly like 3rd generation however detector was static 360 on gantry.4th Generation CT

Reconstruction methods implemented Iterative Reconstruction:Algorithm states that the ray sum is divided by the number of pixels in a matrix then at the next angle the pixel is added to the pixel minus the ray sum then divided by number of pixels in that row the answer to this gives the pixel value at that angle. This is then repeated for every pixel.

Example of Iteration Method

Radon TransformThe radon function computes projections of an image matrix along specified directions. A projection of a two-dimensional function f(x, y) is a set of line integrals. The radon function computes the line integrals from beams in a certain direction. The beams are spaced 1 pixel unit apart. To represent an image the radon takes multiple, parallel-beam projections of the image at different angles by rotating the source and translating it in the x, y direction.

Optical CT

Matlab reconstruction

DiscussionThe project met the brief that was statedFuture work would include adding more pixels and adding a z axis to create a 3D model.

ConclusionThe system worked however not as efficiently as wanted There was many obstacles trying to make a functional program If given more time more pixels and beams could have been added

References[1] Timothy G Feeman Mathematics of medical Imaging a beginners guide Sumat 2009 [2] Paul Suetens Fundmentals of Medical Imaging Second edition 2009[3] Barry Haycock CT scan 2007[4] Mathworks documentation centre. http://www.mathworks.co.uk/help/images/ref/iradon.html[5]Wolfram MathWorld http://mathworld.wolfram.com/RadonTransform.html[6]Mathworks Documentation centre http://mathworld.wolfram.com/RadonTransform.html[7] Science directhttp://www.sciencedirect.com/science/article/pii/S016890021100461X