Parathyroid Scintigraphy (Sestamibi) — Dictation, Appropriateness, and Dose for Residents

1. The Pre-Op Parathyroid Scan: Pinpoint Localization Under Pressure

It’s a classic outpatient nuclear medicine case, but the stakes are high. The endocrinologist has confirmed primary hyperparathyroidism with labs — elevated PTH and calcium. The surgeon has a minimally-invasive parathyroidectomy scheduled, but they’re flying blind without your read. They need you to pinpoint the adenoma. Is it the typical inferior pole location? Is it ectopic in the mediastinum? Is it hiding behind the thyroid? Your report is the roadmap for their first incision.

When I was a fellow, the challenge wasn’t just finding the hot spot; it was dictating it with the precision the surgeon needed, correlating with the prior ultrasound, and making a definitive statement. You can’t waffle. This guide provides a solid template for your Tc-99m Sestamibi parathyroid scan dictations, ensuring you hit all the key points your attendings and referring surgeons expect. For more guides like this, check out the residents and fellows resource hub.

2. What a NM Parathyroid Scan (Tc-99m Sestamibi) Covers and What Attendings Look For

First, remember the core principle: this is a localization study, not a diagnostic one. The diagnosis of primary hyperparathyroidism is made biochemically. Our job is to tell the surgeon where to look. The study leverages the fact that hyperfunctioning parathyroid tissue (adenomas or hyperplasia) is rich in mitochondria, which avidly take up and retain Tc-99m sestamibi longer than the adjacent thyroid tissue.

An attending expects your report to clearly answer:

• Localization: Is there a focus of persistent radiotracer activity on delayed imaging? Where is it, precisely? Use anatomical landmarks (e.g., “inferior to the lower pole of the right thyroid lobe,” “in the superior mediastinum at the level of the aortic arch”).
• Ectopic Glands: Did you specifically look for and comment on ectopic locations? This includes the mediastinum, retroesophageal space, and even intrathyroidal locations. This is where SPECT/CT is invaluable.
• Single vs. Multi-gland: Does the pattern suggest a solitary adenoma (the most common cause, ~85% of cases) or multi-gland hyperplasia (less common, lower sensitivity on imaging)?
• Correlation: Have you correlated with prior neck ultrasound or other imaging? Mentioning concordance between a sestamibi focus and a sonographically identified nodule is a huge confidence booster for the surgeon.

This study is primarily ordered for pre-operative localization in patients with confirmed primary hyperparathyroidism. It’s also crucial for persistent or recurrent disease after a prior neck surgery, where anatomy is distorted and an ectopic gland is more likely.

3. Radiology Report Template for NM Parathyroid Scan (Tc-99m Sestamibi)

Use this template as a starting point for your macros. It’s structured to be efficient but comprehensive, ensuring you don’t miss key elements.

Technique

Radiopharmaceutical: [20-25] mCi of Technetium-99m Sestamibi administered intravenously.
Imaging Protocol: Dual-phase planar imaging of the neck and upper mediastinum was performed. Early phase imaging was acquired at [15-20] minutes post-injection. Delayed phase imaging was acquired at [2-3] hours post-injection.
Additional Imaging: SPECT/CT of the neck and upper mediastinum was performed during the delayed phase for anatomic localization.

Findings

Early Phase: On early planar images, there is physiologic symmetric uptake of radiotracer within the thyroid gland and salivary glands.

Delayed Phase: On delayed planar images, there is physiologic washout of tracer from the thyroid gland. There is a focus of persistent, intense radiotracer uptake located [e.g., inferior to the lower pole of the right thyroid lobe, in the superior anterior mediastinum, in the tracheoesophageal groove on the left].

(If negative: On delayed planar images, there is physiologic washout of tracer from the thyroid gland. No focal area of persistent abnormal radiotracer uptake is identified in the neck or mediastinum to suggest a parathyroid adenoma.)

SPECT/CT: The delayed SPECT/CT images confirm the focus of sestamibi retention, localizing it to [provide precise anatomic location, e.g., a 1.2 cm soft tissue nodule posterior to the inferior pole of the left thyroid lobe, consistent with the sonographic finding]. There is no other abnormal focus of persistent radiotracer uptake. The visualized portions of the thyroid gland appear otherwise unremarkable.

Impression

1. Focal persistent radiotracer uptake [e.g., inferior to the lower pole of the right thyroid lobe], as detailed above. Findings are highly suggestive of a parathyroid adenoma. Anatomic localization is provided by the SPECT/CT images.
2. No scintigraphic evidence of additional hyperfunctioning parathyroid tissue in the neck or mediastinum to suggest multi-gland disease.

(Negative Impression Example):
NEGATIVE PARATHYROID SCINTIGRAPHY.
No definitive focus of persistent radiotracer uptake is identified to localize a parathyroid adenoma. This does not exclude the presence of a small adenoma or multi-gland hyperplasia, which can be below the limits of resolution for this technique.

4. Free Template Sources for Your On-Call Toolkit

Building a personal macro library is a rite of passage in residency. But you don’t have to start from scratch. Beyond your own institution’s templates, two great free repositories exist that are worth bookmarking:

• RadReport.org: Curated by the RSNA, this is a massive library of peer-reviewed templates covering nearly every modality and subspecialty. It’s a reliable source for standardized, high-quality reporting structures.
• Radiology Templates (AU): This Australian-maintained site is another excellent resource with a clean interface and practical, clinically-focused templates.

They are great for finding a solid starting point that you can then customize for your own workflow and your attendings’ preferences.

5. The Next-Level Move: Free-Form Dictation to Structured Report

The template above is solid, but toggling between your dictaphone and a static macro can be clunky, especially when you have multiple findings. This is where AI-assisted reporting tools can streamline your workflow. Instead of meticulously filling in every blank, you can dictate the positive findings in a more natural, free-form way.

For example, you could simply dictate: “Delayed images show a hot spot just inferior to the left thyroid lobe. The SPECT-CT confirms this corresponds to a 1.1 cm nodule posterior to the thyroid.”

Tools like GigHz Precision AI are designed to parse that free-form dictation and automatically populate a structured report based on ACR and society-backed templates. The system helps ensure your final report contains all the necessary elements—like precise localization and negative findings—without the manual copy-pasting. It also incorporates Clinical Decision Support (CDS) frameworks, which can surface relevant guidelines or classifications based on your findings, helping you create a more robust and clinically valuable report.

6. When Should You Order a NM Parathyroid Scan? ACR Appropriateness Criteria

The decision to order a parathyroid scan isn’t random; it’s guided by established clinical criteria. The American College of Radiology (ACR) provides evidence-based guidelines to help clinicians choose the right test for the right reason.

For a patient with biochemically confirmed primary hyperparathyroidism, the ACR Appropriateness Criteria for Parathyroid Adenoma state that Tc-99m Sestamibi parathyroid scintigraphy, particularly with SPECT/CT, is Usually Appropriate for pre-operative localization.

This is the cornerstone indication. While sestamibi is the workhorse, it’s often part of a multi-modal approach. Key alternatives and complementary studies include:

• Neck Ultrasound: Often the true first-line imaging study. It’s excellent for identifying adenomas adjacent to the thyroid but can miss smaller, deeper, or ectopic glands. Combining US and sestamibi boosts sensitivity for solitary adenomas to over 95%.
• 4D CT Parathyroid: A dynamic, contrast-enhanced CT protocol that has very high sensitivity, especially for small or ectopic adenomas missed by other modalities. It involves more radiation, so it’s often used as a problem-solving tool or in cases of recurrent/persistent hyperparathyroidism.
• MRI of the Neck: Can be useful in specific situations, such as in younger patients or for re-operative cases, but is generally considered a secondary option.
• Selective Venous Sampling: An invasive, interventional radiology procedure reserved for complex, re-operative cases where non-invasive imaging has failed to localize the source of excess PTH.

7. How Much Radiation Does a NM Parathyroid Scan Deliver?

Patients and referring providers often ask about radiation dose, and it’s our job to provide an accurate and contextualized answer. A Technetium-99m Sestamibi scan is a low-dose nuclear medicine study.

The estimated effective dose is approximately 6-9 mSv for the sestamibi injection and planar imaging alone. When SPECT/CT is added for better localization (which is standard practice at most centers), the total effective dose is in the range of 7-12 mSv.

To put this in perspective, this dose is in the 1-10 mSv tier, comparable to the amount of natural background radiation a person receives over the course of several months to a few years. It’s a safe and well-established procedure for its indicated use.

8. NM Parathyroid Scan (Tc-99m Sestamibi) Imaging Protocol

Understanding the “why” behind the protocol helps in troubleshooting tricky cases. The standard is the dual-phase technique, which relies on the differential washout of the tracer between the thyroid and parathyroid tissue. An alternative, the dual-isotope subtraction method, is more complex but can be more sensitive for subtle cases.

The dual-phase protocol with SPECT/CT is the most common approach in modern practice. It provides an excellent balance of functional information and precise anatomical localization.

Common protocol pitfalls: The dual-isotope subtraction protocol (using a second tracer like I-123 or Tc-99m pertechnetate to image the thyroid) is more sensitive for multi-gland hyperplasia but is technically demanding. Patient motion between the two acquisitions can cause significant misregistration artifacts, leading to false-positive or false-negative results. For this reason, most centers have standardized on the dual-phase protocol with SPECT/CT.

9. The 3-Months-Free Offer for Residents and Fellows

3+ months free for radiology residents and fellows

Look like a rockstar on your reports — dictate positive findings in free form, and the AI generates a structured report using ACR + SIR templates with the appropriate clinical decision support firing automatically.

All we ask is feedback so we can keep improving the product for trainees. The signup is simple. No credit card, no long forms. To get set up, just provide these three items:

1. Your PGY year (e.g., PGY-2, PGY-4)
2. Your training type (radiology residency or specific fellowship — IR, body, MSK, neuro, peds, breast, nucs)
3. Your training program / hospital name
4. (Optional) Your institutional email

Ready to give it a try? Apply for the residents free-access program and we’ll get you set up.

10. Frequently Asked Questions

Is GigHz Precision AI HIPAA-compliant?

Yes. The platform is designed for de-identified workflows by default. It operates on the de-identified text of your findings, not on raw DICOM images or patient-identifying information from the EMR. All data is handled within a secure, HIPAA-compliant environment.

Do I need my hospital’s IT department to set this up?

No. GigHz Precision AI is a browser-based tool. There’s no software to install on hospital workstations. It works on any modern browser, including the one on your call-room computer, your personal laptop, or even an iPad.

Does it work with PowerScribe or other dictation systems?

Yes. It works alongside your existing dictation system. You can dictate your findings as you normally would, then copy-paste the relevant text into the tool to generate the structured report. The final, polished report can then be easily transferred back into your PACS/RIS.

Can I use it on my phone or iPad?

Yes, the platform is web-based and responsive, so it works on mobile devices and tablets. This is particularly useful for reviewing a generated report or checking a template on the go.

Can I customize the templates?

Yes. While the system comes pre-loaded with standardized templates from societies like the ACR and SIR, you can create, modify, and save your own templates to match your personal preferences or the specific requirements of your attendings and institution.

What happens after my residency or fellowship ends?

Trainees who participate in the free-access feedback program are eligible for significant discounts on post-training plans. The goal is to support you during training and continue to provide value as you transition into practice.

Free GigHz Tools That Pair With This Article

Three free tools that complement the material above:

• ACR Appropriateness Criteria Lookup — Type an indication or clinical scenario in plain language and get the imaging studies the ACR rates for it, with adult and pediatric radiation levels. Built directly from 297 ACR topics, 1,336 clinical variants, and 15,823 procedure ratings.
• GigHz Imaging Protocol Library — A searchable library of 131 imaging protocols with the physics specs surfaced and the matching ACR Appropriateness Criteria alongside. Plain-English narratives readable in 60 seconds, organized by modality.
• GigHz Radiation Dose Calculator — Pick the imaging studies a patient has had and see total dose in millisieverts (mSv) with comparisons to natural background radiation, transatlantic flights, and chest X-rays. Useful for shared decision-making.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 7, 2026