Understanding MPR Views in Dental CBCT Imaging

What Is Multiplanar Reconstruction?

Multiplanar Reconstruction (MPR) is one of the most fundamental CBCT image processing techniques. MPR dental imaging allows clinicians to view volumetric data along any desired plane, creating a complete 3D understanding of anatomical structures.

During CBCT acquisition, the X-ray detector captures projection images as the source rotates around the patient's head. Sophisticated reconstruction algorithms process these projections to create a volumetric 3D dataset. From this volume, MPR software extracts images along three orthogonal planes: axial, sagittal, and coronal.

The Three Standard Orthogonal Planes

Axial Views: Horizontal slices perpendicular to the patient's body axis, as if viewing the head from above. Axial slices are arranged from superior (top of head) to inferior (chin). Axial images are excellent for evaluating bone width, buccolingual anatomy, and assessing bilateral symmetry.

Sagittal Views: Vertical slices parallel to the patient's midsagittal plane, creating right-to-left views of anatomical structures. Sagittal views show anteroposterior relationships, dental and skeletal vertical dimensions, and profile relationships. When positioned along the midline, the midsagittal view provides a profile equivalent to a lateral cephalogram.

Coronal Views: Vertical slices perpendicular to the sagittal plane, creating front-to-back views. Coronal images display left-to-right relationships, show nasal floor and maxillary sinus anatomy, and demonstrate the relationship of teeth to the inferior alveolar canal in the mandible.

Practical Interpretation of Each Plane

When to Use Axial Images:

• Assessing buccal cortical thickness before implant placement
• Evaluating symmetry between right and left sides
• Visualizing transverse skeletal dimensions
• Viewing pathology with horizontal extent
• Assessing mandibular nerve canal position relative to tooth roots

When to Use Sagittal Images:

• Evaluating anterior vertical dimension and overbite/overjet
• Assessing posterior vertical height for implant considerations
• Visualizing sinus floor and floor of nasal cavity
• Determining if sinus elevation is necessary
• Evaluating lesions with superior-inferior extent

When to Use Coronal Images:

• Assessing maxillary sinus anatomy and enlargement
• Evaluating nasal floor position
• Visualizing inferior alveolar canal position in relation to mandibular molars
• Detecting unilateral pathology
• Assessing bone width for implant site evaluation

Synchronized Navigation and Slice Selection

Modern CBCT viewers display all three orthogonal planes simultaneously, linked by a synchronized cursor. Clicking on a location in the axial view automatically updates the sagittal and coronal views to display that exact same anatomical location. This synchronized navigation is invaluable for:

• Precisely localizing pathology in three dimensions
• Measuring distances to vital structures
• Understanding complex anatomical relationships
• Navigating to specific anatomical landmarks

Advanced MPR: Curved and Oblique Reconstructions

Beyond the three standard orthogonal planes, advanced software offers custom reconstructions:

Curved Planar Reconstruction (CPR): Creates a plane that follows the curve of the mandible or maxilla, providing panoramic-equivalent images extracted from CBCT data. CPR is excellent for viewing the dental arches and associated bone.

Oblique Reconstructions: Allow viewing along any custom plane orientation. For example, oblique views perpendicular to individual tooth roots help evaluate root morphology and anatomy.

Window and Level Adjustments Across Planes

CBCT data is acquired as grayscale values representing tissue density. Window and level settings control how this data is displayed:

• Bone Window: Center approximately 400 HU, width approximately 1500 HU—optimizes bone visualization.
• Soft Tissue Window: Center approximately 50 HU, width approximately 400 HU—highlights soft tissue details.
• Sinus Window: Center approximately -500 HU, width approximately 1500 HU—highlights air-filled spaces.

Adjust window and level settings as needed to optimize visualization of structures of interest.

Measurement Tools in Multiplanar Views

All three planes support linear and angular measurements essential for treatment planning:

• Bone height and width dimensions
• Distances to critical anatomical structures
• Dental measurements (root length, angulation)
• Skeletal measurements (vertical dimensions, angles)

Volume Rendering and 3D Reconstruction

While MPR provides detailed cross-sectional views, volume rendering creates three-dimensional surface representations. Volume rendering is excellent for:

• Patient education and consent discussions
• Visualizing overall anatomical relationships
• Virtual surgical planning
• Assessing bone morphology from multiple angles

Clinical Best Practices

• Start with a scout image or 3D view to understand overall anatomy
• Navigate through all three orthogonal planes systematically
• Adjust window and level settings based on structures of interest
• Use measurements to quantify observations
• Document findings with labeled screenshots
• Create detailed reports integrating MPR observations with clinical context

Conclusion

Multiplanar reconstruction is the fundamental technique enabling comprehensive CBCT interpretation. Proficiency with axial sagittal coronal CBCT viewing allows clinicians to fully leverage three-dimensional imaging data for diagnosis, treatment planning, and surgical execution. Master these viewing techniques to unlock the full diagnostic potential of CBCT.