Week Ten - Molecular Imaging Applications

Question 1

What is WRSS and what is it used for?

Answer 1

Weighted residual least square sum used to test the accuracy of a model.

Question 2

Why is parameter estimation used?

Answer 2

With known PTAC, TTAC, we can estimate parameter K constants.

Question 3

What is WRSS a measure of?

Answer 3

The discrepancy between the data and an estimation model. Small WRSS = good model.

Question 4

What are residuals?

Answer 4

Deviations from actual empirical data.

Question 5

Name 5 methods of parameter estimation.

Answer 5

1. Non-linear least squares method.
2. Autoradiographic method.
3. SUV method.
4. Graphical analysis method.
5. Linear least squares method.

Question 6

What are 2 issues with the non-linear least squares method?

Answer 6

1. The estimated outcomes are dependent on the choice of initial estimates. The starting values must be reasonably close to the as yet unknown parameters or it may not converge - or it might converge on a local minimum and not the global minimum.
2. Computationally inefficient and therefore not suitable for voxel by voxel estimation.

Question 7

What is autoradiography?

Answer 7

The use of X-ray film to detect radioactive substances.

Question 8

What does the autoradiographic method require knowledge of?

Answer 8

Knowledge of: LC, k1, k2, k3, k4.

Measurement of Cglu, T, Cp(t)

Question 9

What is the autoradiographic method good for/shit at?

Answer 9

Good for: grey matter

Shit at: high bias in pathology.

Question 10

What is the SUV method?

Answer 10

Standard uptake value = tissue radioactivity concentration/(injected tracer dose/patients body weight adjusted for fat content)

Question 11

Why is the SUV method a popular approach in oncology studies?

Answer 11

It identifies malignant from benign tumours and assesses the efficiency of therapy.

Question 12

What effects the accuracy of the SUV method?

Answer 12

Patient weight, measurement time, plasma glucose level.

Question 13

Name three graphical analysis methods.

Answer 13

Patlak method, logan method, yokoi plot.

Question 14

What are graphical analysis methods?

Answer 14

Data transformed to allow estimation of parameters from linear regression. The slope and intercept of the graphical analysis are related to the parameters of interest in the kinetic model. V simple and computationally efficient.

Question 15

What are the two compartments in the Patlak method?

Answer 15

1. Central compartment that is in rapid equilibrium with plasma.
2. Peripheral compartment where the tracer enters without leaving during the time of the measurements.

Question 16

What are the three compartments in the Logan method?

Answer 16

1. Plasma
2. Non-specific binding in tissue
3. Specific binding in tissue

Question 17

What are the two compartments in the Yokoi method?

Answer 17

1. Plasma

2. Tissue

Question 18

What is the linear least squares method?

Answer 18

A form of mathematical regression analysis that finds the line of best fit for a dataset which provides a visual demonstration of the relationship between data points.