Current MRI Protocol
MRI Settings
Institution: University Hospitals, Case Medical Center
Contact: ?
Machine: Siemens MAGNETOM Skyra 3T, Clinical
Receiver Coil: knee coil
Imaging Sequence: 3D, gradient echo???, T1-weighted
Resolution: 0.5 mm, isotropic
Repetition time (TR): 20 ms
Echo time (TE): 4.92 ms
Flip angle: 25 degrees
These settings were extracted from the DICOM header of a recent imaging session (CoBi Core project CBC_0049/01/dat/MRI/knee1?). This protocol has been used to create an isotropic, T1-weighted image set that reasonably represented the structures of interest, namely cartilage, soft-tissue and an outline of the bony anatomy. Fields not directly relevant to the MRI settings, e.g. imaging date, operator name, etc., have been removed from the list.
attachment:MRI_Settings_T1.txt
-- ["craigbennetts"] DateTime(2013-10-23T20:34:57Z) The approach for modeling may influence the desired imaging protocols. If models are lofted from curves, 2D image sets may be better since they have higher in-plane resolutions than a 3D image set. However, 2D image sets require multiple different orientations to define different structures of interest (i.e. axial for ligaments and tendon; sagittal for cartilage and bone). If models are generated from segmented/smoothed triangulated surfaces, a 3D image set is better.
Example Images
Axial slice:
attachment:knee_AXL.png
Sagittal slice:
attachment:knee_SAG.png
Coronal slice:
attachment:knee_COR.png
Specimen Transport
For transport to imaging, the specimen will be zip tied to the following mounting jig:
ImageLink(Mounting_Jig.png, width=400, alt=Experimentation Workflow)
-- ["hallorj"] DateTime(2013-10-23T17:37:01Z) We should brainstorm/discuss options for specimen transport. One potential issue with the previous mounting fixture is the size. It adds a fair amount (could be measured) of overall width to the specimen. Currently, a knee coil is being used for imaging, where we used a larger head coil previously (I believe this was the case in the old 4T machine at UH). The knee coil is advantageous to obtain higher quality images. I will request the dimensions of the knee coil we currently use and we'll go from there. Also, this info could be moved to the specimen preparation section.
Specimen Orientation
Within the mounting jig, the specimen will be oriented with the patella directed away from the base plate (see figure of mounting jig). For alignment in the MRI, the femur side will be clearly marked on the outside of the bag that contains the knee. The femur, with the base plate down (and the patella up), will be inserted into the scanner first, which approximates a supine position of a patient (head first into the scanner).
Additional MRI Information
Following is an overview of imaging sequences and their suitability for visualizing different anatomical structures of the knee
Cartilage: 1) gradient echo, with or without fat suppression, 2) spin echo, with fat suppression
Mensicus: Proton density
Ligaments/tendons: T2-weighted
Grenier JM, Green N, Wessley, MA. Knee MRI. Part 1: basic overiview. Clinical Chiropractic, 2004, 7:84-89. [http://www.sciencedirect.com/science/article/pii/S1479235404000197# Science Direct Link]
3D gradient echo: good for cartilage
3D spin echo: good for cartilage, ligaments, meniscus
Subhas N, Kao A, Freire M, Polster JM, Obuchowski NA, Winalski CS. MRI of the Knee Ligaments and Menisci: Comparison of Isotropic-Resolution 3D and Conventional 2D Fast Spin-Echo Sequences at 3T. American Journal of Roentgenology, 2011, 197:442-450. [http://www.ncbi.nlm.nih.gov/pubmed/21785092 PubMed Link]
Techniques for reducing metal artifacts:
Stradiotti P, Curti A, Castellazzi G, Zerbi A. Metal-related artifacts in instrumented spine. Techiques for reducing artifacts in CT and MRI: state of the art. European Spine Joural, 2009, 18(Suppl 1):S102-S108. [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2899595/ NCBI Link]