Parathyroid Sestamibi Scan: What It Shows the Surgeon Before Your Operation
Written by John P. Sabra, MD FACS
Updated September 2026
Educational only. This article is not medical advice. Always consult your physician about your individual situation.
The sestamibi scan is one of the most useful pre-operative tests in parathyroid surgery. It is a nuclear medicine study that identifies an overactive parathyroid gland by showing where a radioactive tracer accumulates. When it works, it helps direct your surgeon where to operate. When it does not work, it does not mean there is no disease. Understanding what a sestamibi scan can and cannot do is part of reading your imaging results.
The sestamibi scan uses a radioactive tracer (technetium-99m sestamibi) that is taken up by metabolically active tissue, including overactive parathyroid glands. After injection, the tracer is taken up by both the thyroid and any abnormal parathyroid. The thyroid clears the tracer over time, while an abnormal parathyroid holds onto it. Imaging at multiple time points reveals the location of the retained tracer.
A positive sestamibi scan localizes the abnormal gland to a specific side and level of the neck. A negative sestamibi scan means the test did not show the abnormal gland, but it does not mean there is no parathyroid disease. The diagnosis of primary hyperparathyroidism is biochemical, made by calcium and PTH levels. Imaging is for surgical planning, not for the actual diagnosis.
How the Scan Is Performed
You receive an intravenous injection of the sestamibi tracer. Imaging is performed approximately 15 minutes after injection (the early phase, when both thyroid and parathyroid retain the tracer) and again at 2 hours (the delayed phase, when the thyroid has cleared but an abnormal parathyroid still retains it). The areas of persistent uptake on the delayed phase indicate the abnormal parathyroid location. Many centers add SPECT or SPECT/CT (three-dimensional imaging) to localize the gland more precisely.
⚕ Clinical note The sensitivity of the sestamibi scan for primary hyperparathyroidism is approximately 70 to 80% in published series. Sensitivity is higher for larger adenomas and lower for smaller adenomas or for cases of four-gland hyperplasia. A negative scan is therefore relatively common and does not rule out the disease.
What a Positive Scan Tells the Surgeon
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Side of the neck (right or left): Allows focused surgery rather than bilateral exploration.
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Approximate vertical position: Upper versus lower neck.
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Ectopic location: Can identify parathyroids in unusual locations such as the chest, behind the esophagus, or within the thyroid.
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Pattern of disease: A single focus suggests a single adenoma; multiple foci suggest multi-gland disease.
For patients with a positive sestamibi scan confirming a single adenoma, minimally invasive parathyroidectomy through a small focused incision becomes possible. This is the modern standard for parathyroid surgery and is one of the main reasons sestamibi scanning has become routine in the pre-operative workup.
What a Negative Scan Means
A negative sestamibi scan in the presence of biochemical primary hyperparathyroidism is common and not particularly worrisome. The reasons include the following.
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Small adenoma: Below the resolution limit of the scan.
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Four-gland hyperplasia: Multiple smaller abnormal glands may not produce a focal hot spot.
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Atypical location: Some ectopic glands are missed.
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Technical factors: Variations in scan technique can reduce sensitivity.
For patients with biochemical disease but a negative sestamibi scan, additional imaging is often pursued: thyroid ultrasound (frequently combined with sestamibi as the initial workup), 4D-CT, or in selected cases MRI. Surgery is still appropriate for these patients; the operative approach may shift from focused minimally invasive to bilateral neck exploration.
⚕ Clinical note A patient with a negative sestamibi scan should not be told they do not have parathyroid disease. Imaging is for surgical planning. If the calcium and PTH together meet the biochemical criteria for primary hyperparathyroidism, the disease is present even when imaging cannot find the abnormal gland. Surgery in experienced hands can still cure the disease through systematic bilateral exploration.
Sestamibi vs. Ultrasound vs. 4D-CT
| Imaging Modality | Strengths | Limitations |
|---|---|---|
| Ultrasound | No radiation, real-time, identifies thyroid disease simultaneously. | Operator-dependent. Cannot see ectopic glands in the chest. |
| Sestamibi scan | Identifies metabolically active glands, including ectopic locations. | Misses small adenomas and multi-gland disease. Radiation exposure. |
| 4D-CT | High resolution, identifies very small adenomas, three-dimensional anatomy. | More radiation than sestamibi. Reserved for difficult cases or after failed initial imaging. |
Many centers now combine ultrasound and sestamibi as the standard initial imaging workup for primary hyperparathyroidism. When both agree on a single location, surgical planning is straightforward. When they disagree or both are negative, 4D-CT becomes the next step.
The Bottom Line
The sestamibi scan is a useful pre-operative imaging test for primary hyperparathyroidism. A positive scan localizes the abnormal gland and enables minimally invasive surgery. A negative scan is common, does not rule out the disease, and usually triggers additional imaging or bilateral neck exploration. The diagnosis remains biochemical; imaging is for surgical planning.
If a sestamibi scan has been ordered as part of your parathyroid workup, ask your surgeon what the imaging plan is if the sestamibi scan comes back negative and whether a 4D-CT will be added to the workup.
This article is intended for patient education only. It does not constitute medical advice and does not replace a consultation with your physician. Individual patient circumstances and clinical judgment determine the appropriate evaluation and management for every patient.
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