Dec 15th Quiz

Complete the quiz by 7:30 pm. For the quiz, put your name and e-mail address in the appropriate box as ususal.

Also, complete the course evaluation. For the course evaluation, do not put your name in the name box, put MR Protocols.

• Click here for the Quiz
• Click here for the course evaluation 

MRI Artifacts Assignment

The following questions are due by Wednesday, Dec 15th at 8:00 pm.

Search the internet and find two pictures of each of the following Artifacts: Aliasing, Chemical Shift, Zipper.

Copy and paste the images into a word document and describe how each artifact is produced and how it can be eliminated.

Also, discuss 3 ways that the appearance of motion can be reduced or eliminated from an MR image.

MRI Pulse Sequences

Click here for full screen version.

MR Assignment for December 8th, 2010

Read chapter 5 of your textbook and answer the following questions (Print the answers and bring it to class on Wednesday).

Draw and label pulse sequence diagrams for each of the following (1-4):

1. Conventional Spin Echo

2. Dual Echo Spin Echo

3. Fast Spin Echo

4. Inversion Recovery

5. What parameters (TR and TE) would you use to produce T1 (t-one) weighting in a spin echo pulse sequence?

6. What do the initials ETL, and ETE stand for, what pulse sequence do they apply to, and give another term used instead of ETL?

7. What parameters (TR, TE and TI) would you use to achieve proton density weighting in Inversion recovery?

8. Give the main reasons for using a Short tau inversion recovery(STIR) sequence?

9. List two advantages and one disadvantage of a gradient rephased echo (GRE) sequence compared to a conventional spin echo sequence?

10. How does T2* differ from T2 weighting?

Important Announcement

There will be no in-person class on November 17th, 2010.

I will provide the lecture notes and other information on this web site.

The next class session will be on December 1st.

More information will follow.

MR Safety Quiz Questions

Deadline: November 24th. (Any time before Thanksgiving)

To answer the following questions refer to the 6 links listed on the web log as “Useful Online Resources”

Type your answers in complete, grammatically correct sentences. 

If you quote directly from a particular resource cite your source by placing the Link number and page number in parentheses after the quote. For example, this is how you should signify that you are using the exact words from an article: “Patients shall be pre-screened for contraindications and informed about MRI safety considerations”(Link 2, pg.9).

Question 1

In order to ensure safety to patients and employees using an MRI facility, the MR suite is setup according to specific areas or zones. Describe each of the four zones, giving an example of an area in the MR unit that would fall in each zone. (Write one paragraph minimum for each zone. Information can be found in Link 1 and Link 2)

Question 2

In the ACR guidelines (Link 1) Personnel  Definitions are provided. What are these definitions and how are they relevant to MR safety?

Question 3

Based on the ACR document (Link 1) regarding  “Patients in Whom There Are or May Be Intracranial Aneurysm Clips”, what are the guidelines/recommendations to ensure the safety of such patients in the MR environment? (Your answer should be at least 15 long)

Question 4

Based on the ACR document (Link 1) regarding  “Patients in Whom There Are or May Be Cardiac Pacemakers or Implantable Cardioverter Defibrillators”, what are the guidelines/recommendations to ensure the safety of such patients in the MR environment? (Your answer should be at least 15 long)

Question 5

Regarding the safe use of MR contrast agents, what do the terms NSF and GFR mean, and what’s their relevance to the use of contrast agents in MRI?  (4 sentences minimum)

Question 6

What are the ACR recommendations regarding the screening of pediatric patients? (3 paragraphs minimum).

Question 7

What are the ACR recommendations regarding MRI procedures on patients who are or may be pregnant?  (3 paragraphs minimum).

Question 8

Fill in the missing information in the following statement:

U.S. Food and Drug Administration labeling criteria (developed by ASTM [American Society for Testing and Materials] International) for portable objects taken into Zone IV.  Square green label is ______________for wholly nonmetallic objects, triangular yellow label is for objects with ______________rating, and round red label is for objects that are _________________.

Which type of materials are classified as “MR conditional? (Refer to Link 3, page 36)

 Question 9

Discuss the bio-effects and potential hazards of static magnetic fields, gradient fields and radiofrequencies used in MRI (3 paragraphs minimum)

Question 10

What is SAR, on what basis is it calculated, and what are the FDA approved  limits for the whole body and specific anatomic regions?

MRI Safety (Lecture 11-10-2010)

There are potential risks in the MR environment... (American College of Radiology (ACR) Guidance Document for Safe MR Practices) 

The goal of the lecture is to highlight the potential risks to patients, family members, visitors, and staff; and explore safe practice guidelines and recommendations.

The fundamental principles involved in MR site planning are discussed, and additional sources of information on MRI safety are listed.

Useful Online Resources

1. ACR Guidance Document for Safe MR Practices: 2007--This document covers topics such as MR Safety Policies and Procedures, Static Magnetic Field Issues, Patient and non-MR personnel screening, pregnancy-related issues, pediatric MR safety concerns, contrast agent safety, etc...

2. MRI Safety: 2009--This document covers zoning, screening, and emergency procedures very well with great illustrations and graphics.

3. MRI Safety Issues--This document covers the biologic effects of the static magnetic field, time varying magnetic fields (the gradients), and RF energy. It lists various reported causes of death related to MR, and provides illustrations of the new FDA MR safety terminology.

4. PowerPoint Presentation on safety concerns, specifically geared towards non-MR health care providers. (PowerPoint Below).


5. MR Safety July-2007

6. Video on MR Safety

Scanning Parameters and Techniques (Lecture 10-20 & 11-03-2010)

Follow the link to your right for the scanning parameters handout. It is a pdf document that you can print if that is more convenient for you.

Scan parameters and techniques are very important.

Each student shall:

1. identify the eight most important scan parameters, and
2. evaluate how each of the eight parameters influences image quality and scan time.

 

MR Quiz October 27, 2010

Click here for the quiz.

25 multiple choice questions
Start at 6:00pm  end by 7:00 pm

Practice Questions (Due October 13th)

Choose the best response for each of the following statements.

For a sagital MR image of the lumbar vertebrae this is the gradient that is used for frequency encoding.

1. X
2. Y
3. Z

For an axial examination of the lungs this gradient would be used for phase encoding.

1. X
2. Y
3. Z

This is controlled by the slope of the slice select gradient.

1. Image matrix
2. Slice Thickness 
3. Field of View

This is the precessional frequency of hydrogen when the field strength of the magnet is 10,000 Gauss.

1. 21.28 MHz
2. 42.57 MHz
3. 63.86 MHz
4. 10,000 MHz

This is one way of achieving a thin slice in MRI. (reduce slice thickness).

1. use a steep slice select gradient slope
2. use a broad transmit bandwidth.
3. use a narrow receive bandwidth.
4. Both A and C

This gradient is switched on during the collection of the MR signal (during the echo)

1. slice select gradient
2. phase encoding gradient
3. frequency encoding gradient

Fill in the blanks with X, Y or Z based on the correct gradient.

 

Procedure            Slice Selection     Phase Encoding     Frequency Encoding

 

Sag. Knee

 

Coronal neck

 

Axial Lumbar

 

Sag. T. Spine

 

 

 

October--Lecture Notes 1

Image Density and Contrast
Based on previous discussions, we know that different tissues in the body will interact with radiofrequency (RF) energy in different ways. For example, fat will give up the RF energy it received during the 90 degree RF pulse very quickly (short T1 and an even shorter T2 time). Conversely, water takes longer to give up the absorbed RF energy (relax), and therefore has longer T1 and T2 times.

The T1 curves shown above compare the recovery times for fat, white matter, grey matter and CSF. The horizontal axis on the graph represents repetition time (TR) in seconds. Signal intensity can be measured (read by the machine) at any time.

Based on the TI curves in the graph shown above, answer the following questions:-
If signal intensity is measured at the time labeled T1 CSF:

• What is the contrast between grey and white matter on the resulting image?
• Which two tissues will have the highest contrast?

The density of each tissue varies based on when the signal intensity is measured. For the TE shown in the diagram below (slightly less than 0.2 seconds or 200ms), CSF will appear darker than all the other tissues because it has the lowest signal intensity.

Spatial Localization in MRI

We know how a MR signal is generated and how appearance of different tissues on the image is determined (image weighting), but how does the machine determine where the signal is coming from (spatial localization) ?

The machine needs this spatial information in order to form the image. Each voxel in the patient provides information for the corresponding pixel in the image.

The anatomy is broken down into slices of a particular thickness, and then further divided into voxels based on the scan matrix.

So the computer builds up the image one pixel at a time based on location and signal strength information that it receives from the corresponding voxel in the patient?

To localize the voxels, spatial information needs to be encoded into the MR signal.

Three steps are required :

• First of all, the desired slice must be selected
• Then, spatial information is encoded along the rows
• Finally, spatial information is encoded along the columns

All three functions are performed by the gradients. There are three gradients and they are named according to the axis in which they exert their influence. 





Fall 2010 Quiz 1

Follow this link for quiz 1.

MRI Finals Summer 2010

Click here

MR Quiz 4

The MR Physics Quiz 4 is 20 questions

Start: 6:00 pm
End: 6:30 pm

Click here for quiz

MR Physics Quiz 3

Quiz 3 is 20 questions.
Start: 6:00 pm
End: 6:30 pm

Click here and Enjoy...

MR Physics Quiz 2

Start: 6:00 pm
Submit by: 6:45 pm

Click here for Quiz 2.

Lecture 3 PPT

Click here for PowerPoint 3

Lecture 2

Click here for lecture 2--June 10, 2010

MR Physics Quiz1

Clicke here for the quiz. Submit it by 6:45

MRI Lecture PowerPoint

The PowerPoint presentation below summarizes the information presented in the MR Physics lecture held on June 3, 2010. Review for quiz 1.

Resistance and Resistivity

The video clip below is very informative. Pay attention to the following:

1. The different classes of materials--conductor, insulator, semi-conductor, and superconductor.

2. The relative resistivity of the different materials (be able to compare the resistance of the various materials)

3. Describe the four factors that influence the resistivity of a material.