Quartz 4

MRI Extras

2 min read

TMJ Imaging Anatomy

TMJ Disc Displacement Case Study

Case 1: TMJ Internal Derangement

  • ==Imaging: Open and closed mouth MRI==
  • ==Findings: Disc was anteriorly positioned relative to the condylar head in closed mouth position. On opening, disc remained anteriorly displaced.==
  • ==Diagnosis: Non-reducing anterior disc displacement==
  • ==Clinical Correlation: Patient experiences popping/clicking sounds because the disc is not recaptured.==

Understanding MRI Signals

T1 Weighted Sequence (T1WI)

  • Low Signal Intensity (Black): Air, calcium, cortical bone, rapidly flowing blood.
  • Intermediate Signal Intensity: Fluid, ligaments, muscles, tendons, abdominal organs, cartilage.
  • High-Protein Tissue: Abscess, complex cysts, synovial fluid.
  • High Signal Intensity (Bright): Fat, blood, gadolinium (contrast), melanin, protein.

T2 Weighted Image (T2WI)

  • Low Signal Intensity (Black): Air, calcium, cortical bone, rapidly flowing blood.
  • Intermediate Signal Intensity: Ligaments, tendons, liver, pancreas, adrenals, cartilage.
  • Variable Intermediate/High: Fat, liver, pancreas, adrenals, muscles, cartilage.
  • High Signal Intensity (Bright): Fluid, Cerebrospinal Fluid (CSF), bladder, bile/gallbladder, kidneys.

T1WI vs T2WI Comparison[^46][^47][^48][^49][^50][^51][^52][^53]

Primary Signal Differentiators

  • T1WI: Fat appears bright.
  • T2WI: Fluid appears bright.

TMJ Disc Visualization

  • Closed Position: Evaluation of the disc relationship to the condyle and glenoid fossa.
  • Open Position: Evaluation of the disc translation and morphology during mandibular excursion.

This page intentionally left blank in the source material.

MRI Principles

Image Generation Process[^41]

  • Magnetic field and radiofrequency pulses: The patient is placed in a relatively strong magnetic field.
  • Hydrogen alignment: Nuclei of many atoms, mainly hydrogen, align with the magnetic field.
  • Radiofrequency signal: Several pulses are applied, causing protons to rotate away from the direction induced by the imaging magnet.
  • Relaxation and detection: At the end of the pulse sequence, relaxation occurs, and the signal is detected by a receiver coil.
  • Signal intensity: A larger number of nuclei of loosely bound hydrogen atoms results in a larger intensity of the recovered signal.
  • Reconstruction: Fourier transform and reconstruction techniques are used to produce the final images.
  • Signals are generated based on tissue properties (fluid, fat, etc.) rather than density

Graph View

Backlinks