Is ultrasound suitable for evaluating a jaw mass identified on a computed tomography (CT) scan?

Ultrasound for Jaw Mass Evaluation

Ultrasound is not suitable as the primary imaging modality for evaluating a jaw mass identified on CT; instead, proceed directly to MRI for soft tissue characterization or obtain additional CT imaging with dental reformatting protocols for osseous detail.

Why Ultrasound is Inadequate for Jaw Masses

The jaw presents unique anatomical challenges that make ultrasound poorly suited for comprehensive evaluation:

• Complex bony architecture: The curved, archlike configuration of the mandible and maxilla creates significant acoustic shadowing that obscures underlying pathology 1, 2
• Limited acoustic windows: Dense cortical bone and superimposed dental structures prevent adequate ultrasound penetration to visualize deep jaw lesions 1
• Inability to assess bone involvement: Jaw masses frequently involve or arise from osseous structures, which ultrasound cannot adequately characterize 3, 2

Appropriate Imaging Algorithm for Jaw Masses

When CT Has Already Been Performed

Since you already have a CT scan showing a jaw mass, the next step depends on the lesion characteristics:

For predominantly soft tissue masses:

• MRI with and without contrast is the preferred next step for superior soft tissue characterization, assessment of perineural spread, and evaluation of marrow involvement 3
• MRI provides superior delineation of mass extent, relationship to neurovascular structures, and differentiation between tumor and adjacent soft tissues 3

For predominantly osseous lesions:

• Dental CT reformatting using thin-section (1mm) axial images to create panoramic and cross-sectional views eliminates streak artifacts and optimally displays bone architecture 1, 2
• This technique projects metal artifacts over tooth crowns rather than through the bone of interest, permitting superior visualization 1

Why Not Ultrasound?

While ultrasound has proven utility for superficial soft tissue masses in other anatomic locations (sensitivity 86.87-94.1%, specificity 95.95-99.7% for superficial lesions) 4, these performance characteristics do not apply to jaw masses because:

• The jaw is not a superficial location accessible to ultrasound evaluation 5
• Bone involvement—a critical feature in jaw pathology—cannot be assessed by ultrasound 3, 2
• There is no relevant literature supporting ultrasound for jaw mass evaluation, unlike its established role for extremity soft tissue masses 6, 4

Clinical Pitfalls to Avoid

• Do not attempt ultrasound-guided biopsy of jaw masses without adequate cross-sectional imaging first, as you may miss critical bone involvement or neurovascular relationships 3
• Do not rely on conventional radiographs alone after CT has shown a mass, as superimposition of dental structures obscures underlying pathology 1, 2
• Ensure adequate imaging before biopsy planning so the biopsy tract can be incorporated into definitive surgical resection if needed 7

Specific Next Steps

1. Review the existing CT for osseous destruction, soft tissue extent, and relationship to critical structures 3
2. Order MRI with contrast if the mass has significant soft tissue component, involves neural structures, or shows aggressive features 3
3. Consider dental CT reformatting if the primary concern is osseous involvement or implant planning 1, 2
4. Refer to oral-maxillofacial surgery or head-neck oncology based on imaging findings before attempting biopsy 7