Magnetic resonance imaging (MRI) allows for the delineation between normal and abnormal tissue on a macroscopic scale, sampling an entire tissue volume three-dimensionally. While MRI is an extremely sensitive tool for detecting tissue abnormalities, association of signal changes with an underlying pathological process is usually not straightforward. This digital model can then be used to create a 3D-printed custom holder for the brain. (1,2,3)

An MRI sequence is a number of radiofrequency pulses and gradients that result in a set of images with a particular appearance.  

When describing most MRI sequences we refer to the shade of grey of tissues or fluid with the word intensity, leading to the following absolute terms:

- high signal intensity = white

- intermediate signal intensity = grey

- low signal intensity = black

Often we refer to the appearance by relative terms:

- hyperintense = brighter than the thing we are comparing it to.

- isointense = same brightness as the thing we are comparing it to.

- hypointense = darker than the thing we are comparing it to.

This week we´d like to share the best MRI images from embodi3d. Also, we invite you to become an embodi3D® member and get full access, it´s easy and free!

1.  Aortic type III MRI 3D reconstruction

This excellent 3D model was uploaded by valchanov. The aortic arch type III is described using as criterion the vertical distance from the origin of the brachiocephalic trunk (BT) to the top of the arch in the parasagittal ‘stretched-out’ projection. This distance is < 2 diameter of the left common carotid artery (LCA). This can influence the feasibility and difficulty of interventional and/or surgical maneuvers. 

2. An head´s MRI

pmcpartlan uploads this brain´s MRI, T1 sequence.  In the context of neurosurgical planning, one can lay implantable devices on the skull or brain to see precise ultimate spatial fits, as well as anticipate surgical approaches such as any bone windows. The 3D models can also be excellent educational tools that are more robust and less toxic than fixed tissue.

3. An MRI of 25 year old male

In this 3D model reconstruction we can see we exquisite detail all the structures of the face. Excellent for surgical planning.

4. A left knee MRI after an injury

This MRI shows patella´s osteophytes. The cruciate ligaments and meniscus are normal.

5. Left hemisphere´s brain tumor.

Contrast enhancement visualized. Homogeneous enhancement can be seen in: Metastases, Lymphoma, Germinoma and other pineal gland tumors

Pituitary macroadenoma, Pilocytic astrocytoma and hemangioblastoma (only the solid component), Ganglioglioma, Meningioma and Schwannoma.

Three-dimensional models and navigation systems for neurosurgery can be combined to improve surgical planning and surgeon training. An study titled: New Directions in 3D Medical Modeling: 3D-Printing Anatomy and Functions in Neurosurgical Planning reported herein demonstrates that preoperative planning using diffusion tensor imaging (DTI) tractography and 3D models is feasible and can be employed in the preparation of complex operations. Additionally, it is likely that this process can shorten operation times, contribute to better patient safety, and be used for training surgeons.

6. Right anterior cruciate ligament´s injury

This knee MRI without contrast shows an anterior cruciate ligament´s injury. Most tears occur in proximal or mid portion of ligament. 

Staging, Grading, & Classification
• Complete tear: Ligament functionally incompetent
○ Some fibers may remain morphologically intact
• Partial tear
○ High grade (unstable): Abnormal Lachman but not completely disrupted
– Usually ≥ 50% of ligamentous cross section disrupted.
– Tears involving 50-75% of ligament → high likelihood of progression to complete tear.
○ Low grade (stable): Some laxity on exam but defined endpoint on anterior drawer test.

Image Interpretation Pearls
• Use axial MR images to determine partial vs. complete

7. Lumbar spine´s MRI

In this MRI we can see L4-L5 bulging and osteodegenerative changes. Thanks Dr. Pablo Andres Rodriguez Covili, Medico Neurorradiólogo/Chile.

8. Normal hand finger anatomy by MRI

Hand´s MRI can provide important information for diagnosis and evaluation of soft-tissue trauma in the fingers. An optimal imaging technique should include proper positioning, dedicated surface coils, and specific protocols for the suspected abnormalities. Familiarity with the fine anatomy of the normal finger is crucial for identifying pathologic entities. MR imaging is a powerful method for evaluating acute and chronic lesions of the stabilizing articular elements (volar plate and collateral ligaments) of the fingers and thumbs, particularly in the frequently affected proximal interphalangeal and metacarpophalangeal joints. 

In the palmar aspect of the hand, the flexor digitorum superficialis (FDS) tendons of the lesser (second-fifth) digits insert onto the palmar aspects of the bases of the middle phalanges. Prior to their insertion, they briefly split at the level of the proximal phalanges then reunite at the level of the proximal interphalangeal (PIP) joints to create ring apertures for passage of the flexor digitorum profundus (FDP) tendons. 

In the dorsal aspect of the hand, the digital branches of the extensor digitorum (ED) tendon trifurcate distal to the metacarpophalangeal (MCP) joint. A central band from each ED branch inserts on the dorsal aspects of the bases of the lesser middle phalanges. Radial and ulnar bands continue more distally to insert on the dorsal aspects of the bases of the distal phalanges.

The MCP joint collateral ligaments of the thumb and lesser digits extend with slight obliquity from shallow depressions on the radial and ulnar aspects of the metacarpal heads to the bases of the proximal phalanges. 

9. Left foot MRI

An incredible foot´s MRI showing the normal anatomy with exquisite detail. Excellent for surgical assessment. 

10. Another Lumbar spine´s MRI

This MRI shows normal anatomy.

References

1. Demertzis, S., Hurni, S., Stalder, M., Gahl, B., Herrmann, G., & Van den Berg, J. (2010). Aortic arch morphometry in living humans. Journal of anatomy, 217(5), 588-596.

2. Jones, J. (2018). MRI | Radiology Reference Article | Radiopaedia.org. Radiopaedia.org. 

3. Luciano, N. J., Sati, P., Nair, G., Guy, J. R., Ha, S. K., Absinta, M., ... & Reich, D. S. (2016). Utilizing 3D printing technology to merge mri with histology: a protocol for brain sectioning. Journal of visualized experiments: JoVE, (118).

4. Naftulin, J. S., Kimchi, E. Y., & Cash, S. S. (2015). Streamlined, inexpensive 3D printing of the brain and skull. PLoS One, 10(8), e0136198.

5. Bahadure, N. B., Ray, A. K., & Thethi, H. P. (2017). Image analysis for MRI based brain tumor detection and feature extraction using biologically inspired BWT and SVM. International journal of biomedical imaging, 2017.

6. Mirvis, S. E. (2016). Diagnostic Imaging: Musculoskeletal: Trauma.