High resolution neck ultrasound has revolutionized the diagnosis and treatment of thyroid and parathyroid nodular disease. In the late 1980s, several endocrinologists across the country began to use neck ultrasound for the evaluation and biopsy of small thyroid lumps that could not be felt by hand. Since then, ultrasound resolution capabilities have improved so much that parathyroid tumors underneath the thyroid and deep in the neck can actually be seen.
In addition, clinical endocrinologists have access to comprehensive knowledge of the patient's historical data, physical examination details and other laboratory testing information that significantly increase the physician's ability to locate thyroid and parathyroid nodules. This has led to the recruitment of a new generation of endocrinologist ultrasonographers who are using neck ultrasound in inventive ways to diagnose and treat thyroid and parathyroid disease. R. Mack Harrell, MD, is one of these pioneers.
Neck Ultrasound Experience
Dr. Harrell has personally performed thousands of neck ultrasounds since 1991. In 2006 alone, he personally conducted more than 700 ultrasound evaluations of neck endocrine structures. Dr. Harrell believes that the doctor making the clinical decisions should be the person who searches the neck for disease.
Using a General Electric e-9 ultrasound with matrix probe technology, Dr. Harrell can identify enlarged parathyroid glands in 90 percent of his parathyroid patients with calcium levels higher than 11.0 mg/dl. With accurate ultrasound localization of parathyroid tumors, there is a greater-than 95 percent chance that minimally invasive surgery will be successful.
In addition, Dr. Harrell uses his office ultrasound probe to guide him in performing fine needle aspiration biopsy of thyroid nodules to help rule out thyroid cancer. With ultrasound guidance, biopsies can be obtained in less than 10 minutes without any need for injected anesthesia agents (just a little skin numbing with an ice-cold skin spray of ethyl chloride). The same procedure in a hospital radiology setting typically involves several shots of injected xylocaine for local anaesthesia and 60 minutes of special procedure time. When it comes to maximizing diagnostic efficiency in thyroid and parathyroid disease, there may be no better option than high resolution, office-based ultrasound in the hands of a certified clinical endocrinologist.
Sestamibi is a radioactive pharmaceutical compound delivered intravenously in hospital radiology suites for the purpose of "lighting up" abnormal parathyroid tissue. The compound reveals parathyroid tumors through the use of radiation-detecting technologies such as gamma cameras or radio-guided probes. Sestamibi concentrates rapidly in normal thyroid tissue and parathyroid tissue. After about two hours, this agent "washes out" of normal thyroid and parathyroid tissue, but remains detectable in parathyroid tumors. Thus, a typical outpatient Sestamibi scan consists of two sets of pictures taken by a radiation detector called a gamma camera:
- An initial picture of normal thyroid and parathyroid tissue taken right after injection of the agent, and
- A second picture taken two hours later that demonstrates Sestamibi uptake in overactive parathyroid glands
Outpatient Sestamibi Scanning
Outpatient Sestamibi scanning is very helpful when it demonstrates abnormal parathyroid tissue, but in 30 to 40 percent of patients with clear cut hyperparathyroidism, the test fails to demonstrate abnormal glands after two hours. This circumstance occurs commonly if there is abnormal thyroid tissue blocking the parathyroid signal, or if the offending parathyroid tissue is deep within the neck, in multiple locations, or close to a blood vessel.
In most cases, parathyroid tumors are most effectively localized by preoperative high resolution neck ultrasound performed by an endocrinologist. When outpatient Sestamibi scanning and high resolution ultrasound both demonstrate abnormal parathyroid tissue in the same location, the endocrinologist and endocrine surgeon can be very confident that removal of a single gland through a minimally invasive 1-inch incision will be curative.
Intra-operative Sestamibi Scanning
At Memorial Center for Integrative Endocrine Surgery, because our ultrasonography equipment is so effective for preoperative parathyroid localization, Sestamibi is used mainly on the day of parathyroid surgery. The Sestamibi injection is given 90 minutes before surgery. During the actual surgery a narrow radio-guided probe is inserted into the 1-inch incision, and the probe is used to directly find abnormal parathyroid tissue in the neck. This technique detects enlarged parathyroids 90 percent of the time and is not susceptible to many of the shortcomings of the gamma camera.
Unfortunately, even this gamma probe technology misses multiple gland disease in 10 percent of patients. That is why the center's physicians are adamant about the use of rapid intra-operative parathyroid hormone testing. If the rapid PTH determination drops by more than 50 percent after removal of a diseased parathyroid gland, the patient is very likely to be cured of hypercalcemia and hyperparathyroidism.
Radioactive iodine (RAI) therapy has been used to treat overactive thyroids and thyroid cancer since the 1950s. Thyroid cells are natural iodine sponges that soak up dietary iodine from the blood and convert it into thyroid hormone as part of their normal function. Physicians administer an oral radioactive form of iodine to act like a guided missile to kill overactive thyroid cells or thyroid cancer cells.
Administering Radioactive Iodine
In the case of thyroid cancer, RAI is given orally about three to four weeks after the thyroid is surgically removed. In order for the RAI to be maximally effective, the patient needs to have a blood TSH (thyroid-stimulation hormone) level in excess of 25 (must be off thyroid hormone for at least two to four weeks) and should be on an iodine-restricted diet (no seafood or kelp) for one to two weeks. In order to help protect family members, the patient is admitted to the hospital for 24 to 48 hours of radioactive isolation when the RAI is administered.
In most cancer patients, the dose ranges from 75 to 200 millicuries. Usually, these doses are very well tolerated, but may cause neck discomfort and salivary gland tenderness and swelling in a small minority of patients. On the day of hospital discharge, the endocrinologist starts thyroid hormone therapy and schedules a follow-up check of thyroid hormone blood levels in six to eight weeks. Subsequent to discharge, patients are instructed to avoid intimate contact with other human beings (especially children) for one week.
Combination of Treatments
In summary, RAI therapy is a very effective means to kill microscopic amounts of thyroid cancer left in the neck after thyroid cancer surgery. At Memorial Center for Integrative Endocrine Surgery, RAI is used in most patients whose thyroid cancers exceed a half inch in diameter (larger than 2 centimeters) or exhibit aggressive characteristics on pathologic evaluation. Moderate RAI dosing combined with optimal thyroid surgery with careful lymph node excision has resulted in a thyroid cancer cure for most patients of R. Mack Harrell, MD, and David Bimston, MD.
Many people ask if the use of therapeutic radioactive iodine can lead to other cancers later in life. Until recently, the answer seemed to be a definitive "no." However, a recent cohort study in Scandinavia has suggested a small excess risk for cardiovascular disease and non-thyroidal cancers in RAI-treated patients who were followed for many years. This situation concerns the center's physicians greatly and because of the possibility of a small risk of adverse long-term outcomes, they use RAI to treat thyroid disease only when the benefits far outweigh the risks.