RT 4912 Review (A) Rex T. Christensen MHA RT (R) (MR) (CT) (ARRT) CIIP Websites: http://www.fonar.com/glossary.htm http://www.mr-tip.com/serv1.php?type=welcome http://www.imaios.com/en/e-Courses/e-MRI 6 Key Imaging Goals Optimize Contrast Optimize Coverage and Slice Thickness Optimize Resolution Minimize Artifacts Maximize Patient Throughput Optimize Signal to Noise (SNR) Scenario 1 Radiologist asks for a MRCP to visualize the biliary system. Scenario 2 Radiologist wants a sagittal T2 FSE fatsat knee with better signal and better resolution. Scenario 3 A coronal T1 wrist is too grainy Scenario 4 A FSE T2 fatsat brachial plexus does not get good fat saturation. Scenario 5 FSE T2 IACs have low spatial resolution Build a Protocol/Optimize It! Brain w/wo contrast Routine knee Routine L-spine Advantages/Disadvantages Changing FOV Changing Slice Thickness Changing ETL Changing NSA/NEX Changing TE Changing Bandwidth Changing TR If this…..then this….. P. 136 and P.137 MRI in Practice I have a question? Student Questions a. b. c. d. 1. Higher magnetic field strength is generally associated with which item listed? decreased T2 higher SNR less scan time d. increased spatial resolution all of the above correct answer B a. b. c. d. e. 2. What is the advantage of using partial flip angles in gradient echo pulse sequence? A "steady state" is established in which most of the tissue magnetization remains longitudinal. It increase MR signal intensity. Very short TR's can be used both a and c none of the above correct answer is D Steady State Shorter TR than a T1 or T2 sequence. There is no time for transverse magnetization to decay before the next pulse sequence. Flip angles of 30 to 45 degrees and a TR less than 50 ms. Gradient Echo T1 gradient echo – T1 times of tissues maximized and T2 times of tissues minimized larger flip angle to avoid longitudinal recovery of fat and water. T2 gradient echo – smaller flip angle to – T2 times of tissues maximized and T1 times of tissues minimized Smaller flip angle allows longitudinal recovery a. b. c. d. e. 3. Which of the following results from an increase in the number of averages of an MRI scan? decreased scan time increased SNR increased artifact increase spatial resolution decreased spatial resolution correct answer is B a. b. c. d. e. 4. T2-weighted images are perfomed with: short TE and short TR short TE and long TR long TE and long TR TE equals TR none of the above correct answer is C a. b. c. d. e. 5. If the technologist decreases the field of view it will: results in an image that depicts more area improves spatial resolution increase Signal to noise ratio increases T1 weighting both B and D correct answer is B a. b. c. d. e. 6. On single slice gradient echo images, rapidly flowing blood appears: dark bright dark or bright depends on the vessel both dark and bright correct answer is B Nursing mothers should suspend breast feeding for up to ___ hours after an MRI exam with contrast. a. 12 b. 24 c. 24-30 d. 36-48 answer: d The distance that the 5 Gauss line stands from the isocenter of the magnet is: a. 5ft b. dependent upon the field strength of the magnet c. dependent upon the field strength, geometry, and type of shielding of the magnet. d. dependent only upon the magnet and shielding answer: c The Unit of measure for RF absorption is: a. Volts per pound b. amps per liter c. watts per kilogram d. volts per Tesla Answer: C Contraindications for an MRI exam include: 1. Cardiac pacemaker 2. ferromagnetic aneurysm clips 3. renal failure a. 1 only b. 2 only c. 1 and 2 d. 1 and 3 answer c A joint effusion of the left knee would appear as what on a T2 weighted scan? Dark area around the joint b. Unremarkable c. Bright area around the joint d. Similar signal with the surrounding soft tissue Answer: C a. Inversion recovery sequences are primarily used to identify Pathology b. Anatomy c. Multiple sclerosis plaques d. Fluid Answer: C a. Gadolinium contrast shortens which imaging sequence T2 b. IR c. T1 d. FLAIR Answer: C a. What scanning sequence is used to evaluate for strokes? T2* b. FLAIR c. Diffusion Weighted Imaging d. T1 Answer: C a. What plane would be used to see the corpus callosum in profile? Transverse b. Coronal c. Sagittal d. Oblique Answer: C a. How will freely diffusing water appear on a DWI scan? a. b. c. Isointense Bright Dark ADC – Apparent Diffusion Coefficient Restricted diffusion = low ADC (dark) Unrestricted diffusion = high ADC (same as trace image) Trace image Restricted diffusion = bright Unrestricted diffusion = no change What is the fringe field distance of 1.5 T magnet? 2 Gauss b. 5 Gauss c. 7 Gauss d. 1.5 Gauss Answer: B a. On a FLAIR or T2 weighted sequence a subdural hematoma will appear a. b. c. Hypointense Isointense Hyperintense References: Westbrook, Catherine and Kaut, Carolyn (1998). MRI In Practice, 3rd Edition, Malden, MA: Blackwell Science, Inc.