What is the recommended computed tomography (CT) scan protocol for evaluating a bony tumor of the hard palate in a patient with potential impaired renal function?

CT Imaging for Hard Palate Bony Tumors

Order a CT of the neck/maxillofacial region with IV contrast using bone algorithm reconstruction to optimally evaluate bony erosion and invasion of the hard palate. 1

Primary Imaging Protocol

CT with IV contrast is the recommended modality when evaluating suspected bony involvement of the hard palate. 1 The American Society of Clinical Oncology (ASCO) guidelines specifically state that CT has superior ability over MRI and ultrasound to evaluate for bone erosion that occurs with masses adjacent to the palate in minor salivary gland tumors. 1

Technical Specifications

• Bone algorithm images should be processed concurrently with routine soft-tissue algorithm to best evaluate erosion and invasion of the hard palate. 1
• IV iodinated contrast is recommended to increase conspicuity of the primary lesion, better characterize necrotic or hypervascular tumors, increase sensitivity for detecting metastatic adenopathy, and evaluate patency of vascular structures. 1
• CT also provides superior detection of focal intratumoral calcifications, which are most often seen in benign and malignant mixed tumors. 1

Renal Function Considerations

If the patient has impaired renal function that contraindicates IV contrast:

• CT without contrast remains appropriate for evaluating bone erosion and matrix mineralization, as these features are visible on noncontrast imaging. 1
• The bone algorithm reconstruction is the critical component for assessing bony involvement, which does not require contrast. 1
• However, recognize that you lose the ability to optimally characterize the soft tissue component and detect adenopathy without contrast. 1

Complementary Imaging

Add contrast-enhanced MRI with diffusion sequence if there is concern for perineural invasion or skull base involvement. 1, 2 The hard palate has the highest concentration of minor salivary glands in the upper aerodigestive tract, and malignant salivary tumors (particularly adenoid cystic and mucoepidermoid carcinomas) have a propensity for perineural spread. 3 MRI is significantly superior to CT for detecting perineural tumor spread along named nerves. 1

It is not uncommon to use both MRI and CT when planning resection of a malignant salivary gland mass, particularly when there is concern for skull base invasion and/or perineural tumor spread. 1

Clinical Correlation with Imaging Findings

Research demonstrates that CT detectability of hard palate lesions correlates with pathological depth of invasion (p-DOI), with lesions having p-DOI ≥4 mm being reliably detectable on contrast-enhanced CT. 4 Furthermore, tumors with p-DOI ≥7 mm are significantly more likely to show palatal bone invasion on CT. 4 This information is useful for surgical planning, as radiological depth of invasion (r-DOI) shows excellent correlation with p-DOI (intraclass correlation coefficient = 0.80). 4

Common Pitfalls to Avoid

• Do not order plain radiographs or panoramic films as your primary imaging - they have insufficient sensitivity for evaluating the extent of palatal tumors and bone involvement. 1
• Do not skip the bone algorithm reconstruction - standard soft-tissue windows alone may miss subtle bone erosion. 1
• Do not assume CT alone is sufficient for high-grade or aggressive tumors - these require MRI to evaluate for perineural spread and skull base extension. 1, 2
• Do not order PET/CT as initial imaging - it is reserved for advanced-stage high-grade salivary gland cancers, not for initial characterization of a hard palate mass. 1, 2