The EANM practice guidelines for parathyroid imaging

Key points

Overview

This European Association of Nuclear Medicine (EANM) guideline updates the first edition, published over a decade earlier. It covers scintigraphy, SPECT/CT, PET/CT and PET/MRI in primary and secondary hyperparathyroidism. Exact preoperative localization allows minimally invasive, selective parathyroidectomy. Failure to localize the gland may require bilateral open neck exploration.

Background

pHPT is the third most common endocrine disease and affects women 2-3 times more often than men. Most cases are due to a solitary adenoma, approximately 15-20% to multiglandular disease, and less than 1% to carcinoma; approximately 5% are hereditary. Ectopic glands occur in approximately 16% of people, and supernumerary glands in 3 to 13%. The most widespread preoperative approach, 99mTc-MIBI scintigraphy with cervical ultrasonography, has a sensitivity of 81-95%.

Scintigraphy and SPECT

For 99mTc-MIBI the adult activity is 400 to 900 MBq. Dual-phase images are taken at 10-15 min and 90-150 min after injection. SPECT/CT is superior to planar or stand-alone SPECT, and dual-phase acquisition is more accurate than single-phase. Dual-tracer subtraction with pertechnetate or 123I-iodide helps when the tracer washes out quickly from the parathyroid or is retained in thyroid nodules. Patients on thyroid hormone replacement should have dual-phase 99mTc-MIBI instead, to avoid stopping therapy. In one study, sensitivity was 61% for multiglandular disease versus 97% for single-gland disease.

PET tracers

For 18F-fluorocholine the activity is 100 to 300 MBq or 1.5-3.2 MBq/kg. Imaging is recommended one hour after injection, if possible preceded by an acquisition at 5 min. A meta-analysis of 14 choline studies (517 patients) reported per-patient sensitivity of 95%, positive predictive value (PPV) of 97% and detection rate of 91%. In a 103-patient comparison, sensitivity was 92% versus 39-56% for conventional scintigraphic methods. Drawbacks include higher costs and false positives from inflammatory lymph nodes and thyroid nodules. 11C-methionine had a pooled sensitivity of 77% and PPV of 98%, but needs an on-site cyclotron. 18F-FDG and other PET tracers are not recommended.

Preparation, precautions and reporting

Active vitamin D analogues and calcimimetics may decrease 99mTc-MIBI uptake and should, if possible, be paused for 2 weeks; calcium channel blockers may also reduce uptake. Pregnancy should be excluded. In pregnancy, imaging is done only if absolutely necessary, and ultrasonography and MRI may be preferred. After 123I-iodide, a 3-day breastfeeding pause is recommended. Reports should localize abnormal glands by thyroid quadrant and depth, or by the ectopic site.

Frequently asked questions

Can parathyroid scintigraphy diagnose hyperparathyroidism?

No. It is used to localize hyperfunctioning glands in patients already diagnosed with pHPT.

When is fluorocholine PET/CT useful?

It is an alternative first-line method, effective even after negative or equivocal standard imaging, and particularly useful in secondary hyperparathyroidism.

Should medications be stopped before 99mTc-MIBI imaging?

If possible, active vitamin D analogues and calcimimetics should be paused for 2 weeks because they may decrease uptake.

Source

Petranović Ovčariček P, Giovanella L, Carrió Gasset I, Hindié E, Huellner MW, Luster M, et al. The EANM practice guidelines for parathyroid imaging. European Journal of Nuclear Medicine and Molecular Imaging 2021;48(9):2801-2822. DOI: 10.1007/s00259-021-05334-y. Open access. This page is a summary prepared by Medpresso from the original publication and is not a substitute for the full text or for medical advice.