3D TOMOGRAPHY AND IMAGE RECONSTRUCTION

Where do computers fit in medical imaging?

1. The whole process is computer controlled.
2. Computers are used for 3D reconstruction of images.
3. Visualisation
4. Storage of results

The Problem in Hand

We have three views of the Ferrari. From these views we wish to generate an idea of what the car looks from the interior, the type of its engine and who is driving the car.

The Approach

1. Think of a property that differentiates between the regions.
2. Find the numerical values of the regions using some physical technique.
3. If you cannot find the values individually, find the values of regions.
4. Reconstruct the image using a computer algorithm.

CT

We shall use CT as a case example.

ART

The ART (Algebraic Reconstruction Technique) is a computer technique used for image reconstruction.

Technique

Divide the area of interest into small pixels.

Number the regions 1,2,3, ... N]
Pass a narrow beam of Xray through the region
and measure the intensity of the attenuated beam.
Measure the beam intensities for different angles
and tranlations.

Aim: to find the attenuation offered by each pixel.

Attenuation of a region xj = log (no. of photons entering the
region / no. of photons leaving the region

x1 + x2 + x3 ............... + xN = log (no. of photons entering the
first region / no. of photons leaving the last region)

This gives us an equation. Repeat the process to obtain a set of
simultaneous equations. Solve geometrically by reiteration.
Contact us to learn the details of the reiteration process.

Other Projection methods

1. Fourier Transform Methods
2. Filter Back Projection Method

Shortcomings of ART

1. Slow ..... needs 30-40 times more time than the filtered back propagation method
2. but the ART is easy to programme
3. It also needs a huge storage place

The need for faster computers

Better Resolutions
Real Time algorithms
Better reconstruction
New algorithms

Some buzz words

Parallel processing
DSP
RISC processors
FPGAs
Transputers

Medical Tomography Applied to other fields

Non-destructive testing (NDT)
mapping of geologic data
3D Reconstruction from real photographs: Internet, computer games, remote
learning