Rehabilitation and Radiology Series< /br>Summer, 2006

Objectives:

1. demystify neuroimaging techniques, at least slightly, so you can identify and explain them briefly
2. get a few more board questions right
3. choose well from available options, and decide when to go ahead and order vs consult your radiologist
4. recognize and respect contraindications and non-contraindications for various studies
5. articulate limitations of radiographic studies and appropriately apply findings to patient management

HERE'S THE PLAN:

• Session 1: Go over the Quia quiz
• Session 2: More neuroimaging, odds and ends...
• Session 3: Team Based Learning day with GRAT, application, and prizes.

Materials:

Extra Images that go with Quia quiz:

Risser stages are defined as follows:

• Stage 0 = 0% excursion
• Stage I = at least 25% excursion
• Stage II = at least 50% excursion
• Stage III = at least 75% excursion
• Stage IV = 100% excursion, spinal growth complete
• Stage V = fusion to ilium, height growth complete

Risser image is from American Family Practice web site.

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Handout

CT

• What is it and how does it work? Computerized Tomography - Really just a whole lot of plain polytomography figured out by a computer to produce a good image
• Good for: Quick anatomical looks at hemorrhages, edema, venticle size, etc.
• Lousy for: really fine detail
• Contraindicated for: ? really none besides those for plain films

MRI

• What is it and how does it work? Magnetic Resonance Imaging - positively charged nuclei spin and get energized and synchronized by a radiofrequency pulse produced by a strong magnet, then verious responses and times to response are studied
• Good for: incredible anatomical detail
• Lousy for: calcifications, patients who can't hold still, need urgent medical attention, or are extremely large or claustophobic
• Contraindicated for: intraocular implants, aneurysm clips, some other implanted metals depending on magnetic properties and location, people who forget to take metal objects out of their pockets

PET

• What is it and how does it work? Positron Emission Tomography, done with very unstable radiopharmaceuticals and positrons are formed, collide with electrons, emitting two gamma rays at 180 degrees to each other when thereby annihilated.
• Good for: 3-D precise anatomic imaging of tumors, etc.
• Lousy for: convenience and efficiency - needs a cyclotron nearby!
• Contraindicated for: Multiple repeat stuides due to radiation exposure

SPECT

• What is it and how does it work? Single Photon Emission Computed Tomography (SPECT) uses less unstable isotopes and emits single, not paired gamma rays
• Good for: tracer-based studies indicating activity levels
• Lousy for: details of anatomy
• Contraindicated for: Multiple repeat stuides due to radiation exposure

FMRI:

• What is it and how does it work? Functional MRI; it relies on the fact that the iron in hemoglobin has different properties and will affect T2 time much more when deoxygenated than oxygenated.
  
• Good for: Assessing regional blood flow
• Lousy for: Detailed anatomy
• Contraindicated for: same as for MRI in general

MRI spectroscopy:

• What is it and how does it work? Examines emission characteristics of multiple comounds with sufficient proton density to detremine local concentrations.
• Good for: fatty acids, lactate, N-acetylaspartate (NAA), N-acetylated glycoproteins, choline, methylene groups glutamate, N-aminoisobutyric creatine, and glycerol), methyne groups (sugars)
• Lousy for: anatomical detail
• Contraindicated for: same as MRI

References:

• UIC's great neuroanatomy site!
• Today's Chemist at Work, Volume 8, No. 10, 36-38, 40. MRS: "Catching up with Star Fleet medical"
• Wikipedia links (copy and paste):
• http://en.wikipedia.org/wiki/Positron_emission_tomography for PET
• http://en.wikipedia.org/wiki/Medical_imaging for links to multiple types of studies
• http://en.wikipedia.org/wiki/Magnetic_resonance_imaging#Magnetic_resonance_spectroscopy for various forms of MRI
• Here is the Rehab and Radiology MS Powerpoint show for this series.

Since my M.D. also stands for Messy Desk, please use my e-mail!
Write me anytime at:vstefans@george.ach.uams.edu