Lecture 2 - Introduction to Basic Physics: MRI Image Characteristics & Atomic Physics (Fill-in-the-Blank)

Fill-in-the-blank flashcards covering MRI image characteristics (voxels, FOV, matrix size, resolution, PSF, noise, SNR, CNR, windowing), scientific notation, SI units, and basic atomic physics (quarks, Rutherford, Bohr model, and particle properties) from the lecture notes.

In MRI, the unit element of an image is the __.

voxel

The voxel represents the MR signal in a volume __.

element

The matrix size determines the number of __ in an MRI image.

voxels

The Field of View (FOV) is essentially the image __.

dimensions

Resolution = __ / matrix size.

FOV

For an 8x8 matrix with a 4 mm FOV, the resolution is 4 mm / 8 = __ mm.

0.5

Larger matrix sizes = more __ but longer scan times.

detail

Examples of FOV values include 270 mm, 200 mm, and __ mm.

160

One way to measure resolution is to stimulate the detector system with a single point input; the resultant output image is the __.

point spread function

Noise in MRI can follow Gaussian, Rician, or __ distributions.

Rayleigh

SNR = average of S divided by the __.

standard deviation of the noise

Contrast = difference in pixel values divided by the __.

average pixel intensity

Windowing is the process of manually changing __ to adjust contrast.

contrast

CNR = SNR(A) – SNR(B).

the difference between the SNR of region A and region B

In physics, we prefer to use SI units; all SI units can be broken down into SI __.

constants

19,394,000 written in scientific notation is __.

1.9394 × 10^7

15 mm equals __ μm.

15000

25 MHz equals __ GHz.

0.025

All matter is comprised of atoms; the nucleus contains protons and neutrons, while electrons __ around.

orbit

Protons and electrons are spin __.

1/2

Thomson's plum pudding model depicted a sphere of positive charge with embedded __.

electrons

Rutherford's gold foil experiment showed that the charge is concentrated at the atom's __.

center

Bohr described electrons orbiting the nucleus in fixed __ energy levels.

quantized

Electrons will 'give off' light when falling to a lower energy level and will '' light when jumping up energy levels.

absorb

In Bohr's model, the number of protons equals the number of __.

electrons

Mass of a proton is approximately __ kg.

1.6726 x 10^-27

Mass of a neutron is approximately __ kg.

1.6749 x 10^-27

Mass of an electron is approximately __ kg.

9.109 x 10^-31

Charge of a neutron is __.

0

Charge of a proton is __.

+1

Charge of an electron is __.

-1

Resolution equation

Resolution (x/y) = FOV/MS

Note: there is x/y because FOV can have two different x/y dimensions

Higher resolution yields _____; lower resolution causes _____

1. separation of closely spaced features;

2. merging

How to generate points from the imaging system (meaning, how to avoid blurring/point spread function)

System can include:

1. Tiny hole in lead plate (X-ray)

2. Point source of radioactivity (Nuclear medicine)

3. Thin metal wires (CT)

4. Small hole filled with h20 (MRI)

Gaussian statistical distribution follows

normal distribution or bell curve, symmetrical, with most values close to the mean.

Rician statistical distribution is ______

Asymmetrical

Rician distribution measures the ____ of background noise, which can only be _____

1. magnitude

2. Positive

Increasing signal of Rician distribution makes the curve more ____

Gaussian-like

Rayleigh distribution is purely _____ w/ no _____

1. Background noise

2. Underlying signal strength

Name the SNR statistical distributions

Human eye can deal with which CNR?

>5

Improving contrast to noise ration (CNR) will _______

improve the perception of the distinct differences between two clinical regions of interest

CNR =

SNR =

Based on this equation, what happens to the resolution if FOV and MS double

Resolution remains the same, because there is no difference between 4/2 vs 8/4

If MS increases by two, resolution___

Decreases by 2

If FOV decreases by two, resolution ___

Decreases by two

Isotropic resolution means that___

That Rx = Ry = thickness of the image voxel dimensions, resulting in uniform resolution in all directions.