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Practical CBCT and DICOM guides
Evidence-based explainers for dentists, radiologists and students working with 3D dental imaging. Short, focused, and built around the questions people actually search for.
Basics
CBCT vs CT
CBCT uses a cone-shaped beam and a flat-panel detector, rotates once around the head, and delivers much lower radiation than medical CT — at the cost of lower soft-tissue contrast. For dental and maxillofacial indications, CBCT is the right tool; for tumor staging or soft-tissue disease, medical CT (or MRI) is still needed.
Imaging
Hounsfield units
Hounsfield units are defined so that water is 0 and air is −1000. Cortical bone sits between 1,000 and 3,000 HU, trabecular bone between 150 and 850 HU. CBCT gray values correlate with HU but are not calibrated — use them for comparison within one scan, not as absolute density.
Imaging
Voxel size
CBCT voxel size usually ranges from 0.075 to 0.4 mm. Small voxels (0.075–0.15 mm) are for endodontics, root fractures and fine periodontal detail. Mid-range (0.2–0.3 mm) is standard for implant planning and orthognathic work. Large voxels (0.3–0.4 mm) are for airway, TMJ and full-skull assessment.
File formats
DICOM explained
DICOM is both a file format and a network protocol. A CBCT study is usually hundreds of DICOM files — one per slice — wrapped together with metadata in a folder. Opening it without a dedicated viewer is painful; any modern viewer reads the folder as a single 3D volume.
How-to
How to view a CBCT
Export the study as DICOM from the scanner, drop the folder or zip into a browser-based viewer, scroll through axial, coronal and sagittal planes, measure or annotate as needed, then share with a link. No install required.
Basics
What is DICOM
DICOM is both a file format and a network protocol. A .dcm file holds the image pixels plus metadata (patient name, study date, scanner model, slice spacing). Hospitals use DICOM to move images between scanners, PACS servers and viewers without losing any information.
Imaging
CBCT field of view
Small FOV (around 4×4 cm) is for endodontics and single-tooth assessment. Medium FOV (8–10 cm) is the workhorse for implants and quadrants. Large FOV (>13 cm) covers full arches, TMJs and orthodontic planning. Always pick the smallest FOV that answers the clinical question.
Safety
CBCT radiation dose
CBCT effective dose varies enormously by FOV size, mA·s and voxel choice — from ~30 μSv for a small endo scan to over 1,000 μSv for a large maxillofacial protocol. Pulsed acquisition, smaller FOV and lower mA·s all reduce dose substantially with minimal diagnostic loss for most indications.
Imaging
CBCT artifacts
The five most common CBCT artifacts are beam hardening (dark streaks from dense metal), motion (blurred edges from patient movement), ring (concentric circles from miscalibrated detector pixels), scatter (cupping or low-contrast haze) and aliasing (stair-step on small voxel detail). Most are preventable with positioning and protocol; some require post-processing.
Imaging
MPR explained
MPR works because CBCT voxels are typically isotropic (same size in X, Y and Z). That means a slice through the volume in any direction is at full resolution. MPR is what makes oblique implant planning, panoramic curve generation and TMJ angled views possible from a single scan.
Basics
Panoramic vs CBCT
Use panoramic for screening, eruption assessment, fracture rule-out and treatment overview. Use CBCT when you need to know spatial relationships, depth, or 3D anatomy — implants, impacted teeth in oblique positions, complex endo, pathology extent. CBCT is not a replacement; it's an upgrade for specific questions.
Clinical
CBCT for implants
For each planned implant site, evaluate bone height to vital structures (inferior alveolar nerve, maxillary sinus, nasal floor), buccolingual width, bone density, ridge inclination and adjacent tooth angulation. Modern workflow plans the prosthetic position first, then derives implant axis from that.
Clinical
CBCT in endodontics
Use CBCT in endodontics for: failed previous treatment with persistent symptoms, complex anatomy (extra MB2, C-shaped, dilacerated roots), suspected vertical root fracture, internal/external resorption, anatomic relationships before surgery (apicoectomy near IAN or sinus), and assessment of large periapical lesions. A 4×4 cm FOV at 80–100 μm voxel is the workhorse.
File formats
DICOM vs JPEG
CT and CBCT data are 12–16 bit per pixel — 4,096 to 65,536 distinct values. JPEG is 8-bit (256 values) and lossy. Once converted, you can't adjust window/level to see soft tissue or bone separately, can't measure in mm, and can't reconstruct in another plane. Send DICOM for diagnosis, JPEG only for casual reference.
Reference
CBCT glossary
CBCT vocabulary cluster: voxel (3D pixel), FOV (field of view), MPR (multiplanar reconstruction), MAR (metal artifact reduction), mA·s and kVp (exposure parameters), ALARA (as low as reasonably achievable), isotropic (equal voxel sides), beam hardening (artifact from dense material), Hounsfield units (CT density scale, only approximated in CBCT).