Advanced Imaging Modalities (CBCT, CT, MRI, Ultrasound, Nuclear Medicine)
CBCT
Understand the principles: cone-shaped beam, flat-panel detector, single rotation, isotropic voxels. Know advantages (high spatial resolution, low dose vs CT, 3D bone detail) and limitations (scatter, beam hardening, metal artifact, limited soft-tissue contrast, and field-of-view trade-offs). Know common applications: implant planning, endodontics, orthodontics, and airway assessment. Understand that CBCT dose is lower than medical CT but not negligible; optimize FOV and exposure.
CT and MRI
CT: excellent bone detail, higher dose, good for trauma and tumors. MRI: superior soft-tissue contrast, no ionizing radiation, but contraindicated with certain implants and requires patient cooperation. Know T1 vs T2 weighting and common sequences.
Ultrasound and nuclear medicine
Ultrasound: real-time, no radiation, operator-dependent; good for superficial structures. Nuclear medicine: functional imaging (e.g., bone scan, salivary function), low spatial resolution.
Traps
Questions test which modality is best for a specific task and whether CBCT is appropriate for soft-tissue diagnosis (it is not). Watch for confusion about dose comparisons and artifact sources.
Rule of thumb
Bone detail → CBCT/CT; soft tissue → MRI/ultrasound; function → nuclear medicine. Match the modality to the question being asked.