Diagnostic dilemmas in parathyroid scintigraphy

Area of Science:

• Nuclear Medicine
• Endocrinology
• Radiology

Background:

• Parathyroid adenoma localization is crucial for surgical planning.
• Technetium Tc-99m MIBI scintigraphy is a common imaging modality.
• Limited sensitivity and confounding factors like thyroid nodular disease can affect accuracy.

Purpose of the Study:

• To refine the interpretation of Tc-99m MIBI scintigraphy.
• To improve preoperative localization of parathyroid adenomas.
• To analyze false-negative and false-positive results in patients with concomitant thyroid nodular disease.

Main Methods:

• Prospective review of dual-phase Tc-99m MIBI scintigraphy in 77 patients with primary hyperparathyroidism and solitary parathyroid adenomas.
• Inclusion of Tc-99m pertechnetate imaging before surgery.
• Identification and revision of false-negative and false-positive scintigraphic findings.

Main Results:

• Revision of 19 false-negative scans identified adenomas in seven patients, often due to rapid tracer washout.
• Subtraction imaging could have identified two additional lesions.
• Four studies were falsely positive, three associated with thyroid nodular disease, yielding a 91% positive predictive value.

Conclusions:

• Differential washout of Tc-99m MIBI from thyroid and parathyroid tissue is inconsistent.
• Subtraction imaging and contour analysis are recommended for rapid MIBI washout cases.
• Thyroid lesions contribute to, but do not fully explain, false-positive findings.