EngE_1104_Spring_2007_Lab_10_Students_Copy_V1A_TW -...

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Explorations Of Our Digital Future Spring 2007 Lab 8: Written by Jeremy Garrett, Edited by Tom Walker, Copyrighted Feb. 2006 —Jan. 2007 Lab Objective: The objective of this lab is to better understand matrices, images, computers, and image manipulation by creating and manipulating “false-color” MRI images of a real human brain. Lab Overview: An MRI has been used to take “pictures” of the inside of a patient’s brain. MRI machines do not take pictures in the normal sense; instead they record the number of atomic nuclei of certain types per unit volume. By changing the settings, doctors can tune the machines to be more sensitive to certain chemicals than others. As a result, medical imaging technicians and neurosurgeons often assign artificial colors to represent those different results. In this lab you will load two sets of images into MatLab. (One set from a patient when he/she was healthy and a second set taken after the patient became ill.) You will then build a false color composite image for the doctor. To further assist the doctor, you will then subtract one image from the other to look for changes in internal chemicals that make up the brain. You will also use edge detection to help the doctor check for physical changes to the brain (such as those caused by strokes, tumors, or blunt trauma). Comments and Some General Background Information: This lab strongly relies on the skills that you gained in the Chromakey Lab, so please keep your old lab handy for reference. Although MRI machines vary in strength, they all use extremely strong magnets, which are among the strongest anywhere on earth. (The strongest magnet ever made is only about 10 times stronger than those used in an MRI machine.) The magnets inside these MRI machines are so strong that they actually grab and rotate the nuclei inside the atoms in the patient’s body. Then, when the magnet “lets go” of the nuclei, the nuclei flip and rotate and emit microwaves – of the same kind that we cook food with – but these come OUT of the patient and into the MRI’s sensors. Just as with a microwave oven the set of frequencies that are described as “microwaves” (which are actually ~1cm long waves) are created and absorbed most easily by the hydrogen that is inside water. By changing the sensitivities and frequencies that are used, it is possible to make the MRI machine more or less sensitive to various molecules. By scanning multiple times it is possible to assign a different color to the results of each set of settings. The images that you are using in this lab were actually created when Mr. Garrett took real MRI data (from the website shown at the end of this lab) and used MatLab to scale the data and separate it into three sets – which is the other main way that colored MRI images are made. Regardless of which technique is used, each color and each brightness represents a different concentration of some molecule (usually water). These changes in concentration can quickly show not only
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This note was uploaded on 09/19/2011 for the course ENGE 1114 taught by Professor Twknott during the Fall '06 term at Virginia Tech.

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EngE_1104_Spring_2007_Lab_10_Students_Copy_V1A_TW -...

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