Preliminary Diagnosis: Melanoma
I. What imaging technique is first-line for this diagnosis
- Primary lesions are not commonly imaged.
II. Describe the advantages and disadvantages of this technique for diagnosis of melanoma.
- Not applicable
III. What are the contraindications for the first-line imaging technique?
- Not applicable
IV. What alternative imaging techniques are available?
- CT with contrast
- MRI with contrast
- PET/CT
V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of melanoma.
CT with contrast
Advantages
- Relatively inexpensive and fast imaging modality
- Offers exquisite detail of the underlying osseous structures detailing osseous involvement from the primary tumor and helping detect bony metastasis
Disadvantages
- Exposes patients to ionizing radiation
- Less adept in staging the neoplastic process
MRI with contrast
Advantages
- More sensitive and specific in detecting the extent of soft tissue invasion and infiltration of the primary tumor
- Highly specific and sensitive in detecting perineural extent of tumor
- Does not expose patients to ionizing radiation
- More sensitive in detecting soft tissue metastasis compared to CT imaging
Disadvantages
- Expensive
- Time-consuming
- Requires significant patient cooperation to minimize motion artifact
- Less adept in staging the neoplastic process compared to companion PET/CT imaging
PET/CT
Advantages
- More sensitive and specific in detecting the primary tumor and any soft tissue, osseous, or lymph node metastasis
- High negative predictive value and may alter treatment
- Gold standard in tumor staging
Disadvantages
- Highly expensive imaging
- Time-consuming
- Requires significant patient cooperation
VI. What are the contraindications for the alternative imaging techniques?
CT with contrast
- May be contraindicated in pregnant patients
- Relative contraindication in patients with renal failure
- Relative contraindication in patients with contrast allergy
MRI with contrast
- Contraindicated in patients with non-MR compatible hardware
- Gadolinium contrast is contraindicated in patients with a GFR less than or equal to 30
PET/CT
- May be contraindicated in pregnant patients and patients who are breast-feeding
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