Alzheimer's Disease Study Scanning Procedures

From Center for Cognitive Neuroscience
Jump to navigation Jump to search

Pre Scan

The following items generally need to be brought to a functional MRI acquisition.

  • Consent Form: Two copies in case the subject wants to take a copy home.
  • Approved Metal Screening Form: Extra copies may be needed for parents of children being scanned or whenever additional non-MR safety certified individuals must be brought into the control room.
  • Research Questionnaire: Used to document subject medical and family history.
  • Secure Lab Notebook: Used to record acquisition order and other notes about the scans or subject. Remember the notebook contains confidential subject information.
  • Lab Laptop: Used to display functional stimuli and record subject responses.

Obtaining Consent

Discuss the scanning procedure and important safety information with the subject. Take time to answer the subjects questions, explain what Functional MRI is and obtain a signature on the consent forms. More information about obtaining consent from a subject or legal representative can be found on the UCLA Office for Protection of Human Research Subjects.

Metal Screening

The metal screening form is your most important piece of safety equipment . Ask the patient if they have any medical devices and have them fill out the form front and back. The surgical history section on the back may reveal a medical installed medical device which the subject neglected to mention on the front. Final metal screening will take place at the scanner where the subject can lock up personal effects and be screened with a metal detecting wand.

Pre Testing

Explain to the subject that you will now be taking a brief word pairing memory test and that this is practice for a similar activity which will be done in the scanner. We use the Unrelated Word Pairing Test to assess the cognitive state of the subject. If the subject is amnestic and cannot perform the task, explain the alternative Picture Priming Task. After administering the pre-test, explain how the subject will perform the same task in the scanner and provide their responses using the MR safe button box.

Research Questionnaire

Interview the subject and fill out the Research Questionnaire to record the subjects medical history and family history of cognitive decline. The questionnaire can be completed after the scan to make your scan appointment on time. The questionnaire contains some sensitive personal health information and can bias the subjects as to the nature of the study. So collecting that data after the scan can keep the subject more at ease through the majority of the session.

At the Scanner

De-Metal the Subject

Be sure that the patient is fully aware of safety concerns associated with an MRI machine before bringing them into the control room. Inform them that the magnet is always on and point out that nothing metallic or electronic can be brought through the scanner door. Ask the patient to use the restroom before going entering the scanner area.

Have the subject remove any metal from their person and secure their belongings. Check the subject with the metal detector to catch any stray change, paper clips, and hair pins. Bra straps, small metal grommets on jeans, and permanent dental work are generally the only metal which can enter the scanner. MRI safety is a complete topic of its own and should not be taken lightly. Have the subject step

Familiarize the Subject with the Device and Load the Subject

Different subjects have different levels of comfort with the scanning procedure and equipment. Walking the subject around the scanner, showing them that it is open in the back, and making it clear that you will be in communication with the subject throughout the procedure all help make the subject more comfortable. Comfortable and calm subjects are more still and can tolerate more time in the scanner.

Ideally, an MRI technician or co-investigator will be available to load the subject in the scanner while the subject is registered in the scanner console and the multimedia stimuli presentation hardware and software are set up.

Talk with the subject before beginning acquisitions to familiarize them with the intercom. Acquire a circle scout 3 view image to check the subjects position.

Structural Scans

During the structural scans, instruct the patient to relax and try to stay still during the scan sequences. Playing music or a video to entertain the patient can help keep patients comfortable. Depending on the subject, you may need to talk with them between each sequence or at larger intervals. Check the images as they are acquired to spot bad scans before the the session is over.

Sequences

  • Circle Localizer: Quick 3 View Scan. Used to check patient position.
  • Axial Coplanar: Basic Axial Image. Used to register whole brain functional images.
  • MP-RAGE 3T: High Resolution Sagittal Image.
  • Axial T2 3mm Resolution: Primary Diagnostic Scan. Used to assess general levels of atrophy of major brain areas including the hippocampus.
  • Hippocampal High Resolution (HHR) Structural: A small field of view coronal image of the Hippocampus and surrounding structures. These images are segmented for precise cortical thickness measurements.
  • Hippocampal High Resolucton Matched Bandwidth: Another HHR scan used to register functional HHR
  • Diffusion Tensor Image (DTI): A special structural scan which can be used for tractography.

Functional Scans

The subject should be familiarized with the functional activities before they are loaded in the scanner. Before beginning the functional portion of the scan, check that the subject can hear, see and interact with the stimuli using the button box correctly. Remember, while in the scanner, the subject cannot see the remote they are using and may need help positioning their hand. Review the directions for each sequence before you start the sequence.

After a functional scan is acquired, move on to the next sequence and check the new data. Watch for shifting, bobbing, or rolling head movement during the scan. If movement is detectable in the images, time allowing, you may need to ask the subject to re-run a sequence.

In my experience, subjects generally move the most at the beginning of a session and mellow out as time passes. However, after a certain amount of time held still in the scanner, even very patient subjects become increasingly uncomfortable and twitchy. If this happens, they aren't likely to produce more stable images.

Functional Sequences

  • Unrelated Word Learning and Recall: An 8 minute computerized version of a popular memory assessment instrument. This sequence be acquired whole brain or acquiring a smaller FOV for Hippocampal High Resolution (HHR) Functional Images. The design of this paradigm allows us to observe, memory encoding and retrieval.
  • Picture Priming: A 7 minute functional sequence in which subjects are shown full color photographs. Subjects identify whether the picture was taken indoors or outdoors. This is an easier task which can be completed by subjects from Mild Cognitive Impairment and Demented populations who cannot complete the Unrelated Words Task. This task can be run in whole brain or HHR as well

Post Scan

When the last scan is completed, speak to the subject over the intercom and tell the subject you are coming to take them out. Close any open images on the console before bringing the subject into the control room. After checking yourself for metal, enter the scanner room. Lower the bed to its lowest position before removing the headcoil and goggles. Subjects may sit up instinctively when they are uncovered and you want to avoid having them sit or stand up while the bed is at a dangerous height. When the headcoil and functional equipment have been removed, instruct the subject sit up carefully and take their time before standing up. Inform them that people may be temporarily dizzy or uncoordinated after an extended stay in the scanner. Retrieve the subjects personal belongings in the control room, pack up research equipment and vacate the scanner room promptly for the next group.

Post-test the subject on the functional exam according to the Unrelated Word Pairing Test. Log the subject's performance in the notebook and complete the research questionnaire if it has not yet been completed. Always thank your research subjects and inform them that we will likely want to re-scan them in a few years for our longitudinal study.