 |
 ADVANCED IMAGING CENTER PHYSICIAN NEWS |
 May 1, 2001 |
Diagnosis of Parathyroid Adenomas: Sestamibi Parathyroid Scintigraphy
 |
 |
 |
|
ADVANCED IMAGING CENTER PHYSICIAN NEWS |
May 1, 2001 |
|
|
|
CLINICAL INFORMATION: The patient is a 45-year-old female who presented to offices of Dr. Manuel Arroyo* and Dr. Clayton Reynolds** with high serum levels of calcium and parathyroid hormone PTH. Parathyroid adenoma was clinically suspected. She was referred to AIC for a radionuclide parathyroid scan.
TECHNIQUE: The patient is usually injected with about 20 millicuries of 99m Technetium Sestamibi and anterior images are obtained over the neck and chest 5, 10, 20, 60, and 120 to 150 minutes post injection.
NORMAL SCAN: The initial images (Fig. 1a) demonstrate normal physiologic uptake of Sestamibi within the salivary glands and parotid glands in addition to the thyroid as well as the heart. On the 2.5 hour delayed images (Fig. 1b), there has been washout of most of the activity from the thyroid gland. No abnormal uptake is noted in the neck or mediastinum. Note that a normal parathyroid gland (and there are generally 4 of them: 2 superior and 2 inferior ones usually posterior to the upper and lower poles of the thyroid) does NOT show any uptake.
ABNORMAL SCAN: A parathyroid adenoma also demonstrates rapid uptake on the initial images. However, unlike a normal thyroid, the adenoma demonstrates persistent uptake of Sestamibi and is readily visible on delayed images. Ectopic adenomas in the mediastinum are also easily detected with this technique. Fig. 2a-b demonstrate the initial and delayed images on the above patient who has had a history of thyroidectomy. Consequently, the thyroid in never visualized. However, a small but well demarcated focus of increased uptake is noted on both the initial and delayed images in the region of the right inferior parathyroid gland (arrows) consistent with an adenoma.
CAUSES OF PRIMARY HYPERPARATHYROIDISM: Parathyroid Adenoma (87% = single 80% + multiple 7%), Parathyroid hyperplasia (10%), Parathyroid Carcinoma (3%)
DISADVANTAGES: Thyroid may not wash out by 3 hours (solution: Sestamibi-Pertechnetate subtraction); Thyroid adenoma may also demonstrate retained uptake.
ACCURACY: Sestamibi scan is highly accurate in detecting parathyroid adenomas (sensitivity and specificity of about 95%). A combination of this scan and CT, MRI or US can detect and localize nearly 100% of adenomas.
For more information, or for any questions or concerns, please call me at (661) 949-8111.
Ray H. Hashemi, M.D., Ph.D.,
Director* Dr. Manuel Arroyo, MD, is a family practitioner in Lancaster, California, and can be reached at (661) 949-5833.
** Dr. Clayton Reynolds, MD, is an endocrinologist in Lancaster, California, and can be reached at (661) 945-7806.