Protons and neutrons are the basis of a nuclide; an estimate of 1500 nuclides, although unstable, releases subatomic particles (energy) to establish a more stable state (Anderson, 2004). The unstable state is the basis for radioactive decay processing, and the nuclides are labeled radionuclide. The 1940s and 1950s marked the beginning of radionuclide medical production, through the use of reactors, accelerators, and cyclotrons (Anderson, 2004). Although widely and initially implemented for cancer therapy, radionuclides are also used for nuclear medicine imaging. Therapeutic application of radionuclide began in 1951, in the United States, with the first FDA-approved radiopharmaceutical, Sodium iodide, as treatment with thyroid patients (Anderson, 2004).
Two nuclear medicine exams, thyroid and the 24 hour uptake which completes the exam, along with hepatobiliary or gallbladder, will be discussed in the following body of work. Definition, purpose, necessary precautions, description, preparation, and potential results of the exams in question, are some of the topics outlined for discussion throughout the compilation of research material.
Thyroid scan and 24 hour uptake measurement scan
A thyroid scan is a diagnostic procedure, evaluating the gland located in the front of the neck, which controls the metabolism of the body (Weber, 2001). The 24 hour uptake exam measures the amount of radioactive iodine that is administered to the patient (Balon, Silberstein, Meier, Charkes, Royal, Sarkar, and Donohoe; 2006).
When the thyroid gland becomes abnormally large, with swelling larger on one side, or when firm nodules are detected by palpitation. Determination of cause of enlargement and confirmation of the diagnosis of hyperthyroidism, an overactive thyroid, or hypothyroidism, an underactive thyroid, is the basis of the application of the scan (Weber, 2001). The 24 hour uptake measurement is performed to assist nuclear medicine technologists and radiologists in interpreting and reporting results to physicians who order the exam (Balon, Silberstein, Meier, Charkes, Royal, Sarkar, and Donohoe; 2006).
Screening of the patient is important prior to the application of the scan. A low-iodine dietary outline is given, along with laboratory testing that may be necessary (Silberstein, Alavi, Balon, Becker, Charkes, Clarke, Divgi, Donohoe, Delbeke, Goldsmith, Meier, Sarkar, and Waxman; 2004). Medications, such as cough medicines, oral contraceptives and thyroid medications can impede the uptake; therefore, the patient is typically instructed to stop taking such medications for up to four weeks prior to the scanning (Weber, 2001). To avoid inaccurate results, any tests prior to the scan, especially tests administered with iodine or other types of contrasts, have to be reported to the patient’s doctor. Fasting, or absence of food and/or drink, the day before radioactive material is introduced to the body is implemented by some nuclear medicine departments. Prior to the exam, metallic objects such as dentures and jewelry need to be removed from the patient to ensure imaging results do not display obstructions (Weber, 2001).
-Radiopharmaceutical administration and Image acquisition
For the initial part of the exam, approximately 1-5 mCi of Na131 I iodideb is administered prior to scanning, accompanied by 0.4-5.0 mCi of Na 123 I iodideb (Silberstein, 2004). The patient is placed supine-lying on back-on the scanning table; the images acquired are anterior and posterior from the top of the skull through the femurs (Silberstein, 2004). Approximate time is 10-15 minutes to obtain sufficient images for proper reading and reporting results; if whole body scan is acquired, the testing time is approximately 40 minutes in duration.
The uptake measurements are conducted 18-24 hours after the administration of the radioiodine; therefore the label of “24 uptake,” although in certain circumstances, uptake measurements can be cultivated 2-6 hours after initial part of the exam (Balon, 2006). Administration of 99mTc-pertechnetate, approximately 0.013 mCi, in conjunction with the radioiodine administered with the first part of the exam, is before the scanning of the patient. The images needed for reading and reporting results are focused on the neck; in circumstances surrounding following surgery for thyroid cancer, a whole body scan and image is acquired (Balon, 2006).
There are no special precautions necessary; patient should consult his or her doctor in regards to beginning any medications that were stopped prior to the exam (Weber, 2001).
There are no known risks involved with the exam (Weber, 2001).
Results-normal, abnormal, and possible sources of error
Normal scans should display a normal size thyroid, shape and position equally important. There should be no increased or decreased levels of radionuclide present (Weber, 2001). The uptake results should be within a generally normal range (Balon, 2006). Abnormal results indicate “hot spots,” which is an indication of an overactive benign growth; this in no indication of cancer. “Cold spots” are indicative of and underactive thyroid; cysts, nonfunctioning benign growths, inflammation, or cancer are possible sources of cold spots (Weber, 2001).
Error can happen, resulting in inaccurate results and possible rescanning or additional views will need to be performed to avoid the possibility of misdiagnosis. Possible errors with the beginning of the exam are: contaminated scanning table or collimator, “activity” or “artifacts” detected in the esophagus, or uptake in the breast tissue (Silberstein, 2004). With the uptake exam, interference from food or medications and electronic instability are typically sources of error (Balon, 2006).
The scan of the gallbladder, using a small amount of radioactive contrast which is injected into the body, to view how the dye travels through the body and absorbed by the tissues (Edgren, 2001).
A gallbladder scan is implemented to detect gallstones, tumors, or possible defects of the gallbladder. Blockages of the bile duct, which leads from the gallbladder to the small intestine, are also examined; the function of the gallbladder can be viewed as well (Edgren, 2001).
Women who are pregnant or breastfeeding need to consult their physicians before being scheduled for the exam. To avoid the possible errors with reporting results, certain medications and the possible consumption of a high fat meal should be withheld (Edgren, 2001). Typically two to four hours of fasting is recommended prior to being injected with the radiopharmaceutical (Balon, 2001). Any history of previous surgeries, timeframe of most recent meal, what medications the patient is currently taking, along with lab results of bilirubin and liver enzyme levels, and results from a gallbladder ultrasound that was conducted prior to the scan is important (Balon, 2001).
-Radiopharmaceutical administration and Image acquisition
DISIDA, 2,6-diisopropylacetanilido iminodiacetic acid or BRIDA, bromo-2, 4, 6-trimethylacetanilido iminodiacetic acid is injected into the body, 1.5-5 mCi, by way of intervenous (Balon, 2001). Anterior views are acquired, duration being 30-60 minutes. Additional views, such as right lateral and left or right anterior oblique, may be obtained if necessary (Balon, 2001). Decubitus views can be obtained if the question of a bile leak is in question.
Patient can return to normal activities after scan, and no known special care is required (Edgren, 2001).
Although the risk of radiation is minimal, due to exposure to the radioiodine used in the exam, a patient may experience a reaction to the contrast used (Edgren, 2001).
Results-normal, abnormal, and possible sources of error
A gallbladder without stones, lack of growths, tumors, and no signs of infection or swelling are considered normal results. Normal filling of bile into the gallbladder and secretion of the bile duct without blockages are also detected (Edgren, 2001). Abnormal results indicate possible dysfunction or inflammation of the gallbladder, the presence of stones in the gallbladder or bile duct, along with tumors, growths, or other types of blockages are results of an abnormal scan (Edgren, 2001).
The sources of error vary from insufficient or prolonged fasting, the presence of severe hepatocellular disease, bile duct obstruction, illness, pancreatitis, chronic cholecystitis, or a bile leak due to gallbladder perforation (Balon, 2001).
For the thyroid scan, a physical exam and patient’s history should be obtained prior to recommendation, scheduling, and conducting of exam. The diagnosis of hyperthyroidism or hypothyroidism is made when the uptake exam is conducted, when measurements of the serum thyroid hormones and TSH levels are taken; a higher uptake result often has better clinical significance than a lower uptake (Balon, 2006).
Prior to the gallbladder scan, an indication for the study is required. Abnormal results, such as a biliary leak, are detected when tracer, the contrast, is found in any other location than the liver, gallbladder, bile ducts, bowel or urine. This can be typically detected with decubitus views (Balon, 2001).
Anderson, C. J. 2004. Nuclear Medicine. Chemistry: Foundations and Applications.
Balon, H. R., MD, Chair (William Beaumont Hospital, Royal Oak, MI); Silberstein, E. B., MD (University of Cincinnati Medical Center, Cincinnati, OH); Meier, D. A., MD (William Beaumont Hospital, Royal Oak, MI); Charkes, N. D., MD (Temple University Hospital, Philadelphia, PA); Royal, H. D., MD (Mallinckrodt Institute of Radiology, St. Louis, MO); Sarkar, S. D., MD (Jacobi Medical Center, Bronx, NY); Donohoe, K. J., MD (Beth Israel Deaconess Medical Center, Boston, MA).
- Society of Nuclear Medicine Procedure Guideline for Thyroid Uptake
Measurement. Version 3.0, 5 September 2006.*
Balon, H. R., MD (William Beaumont Hospital, Royal Oak, MI); Brill, D. R., MD
(Chambersburg Hospital, Chambersburg, PA); Fink-Bennett, D. M., MD
(William Beaumont Hospital, Royal Oak, MI); Freitas, J. E., MD (St.
Joseph Mercy Hospital, Ann Arbor, MI); Krishnamurthy, G. T., MD
(Tuality Community Hospital, Hillsborough, OR); Ziessman, H. A., MD
(Georgetown University, Washington, DC); Lang, O., MD (Charles University,
Prague, Czech Republic); and Robinson, P. J., MD (St. James University, Leeds,
United Kingdom). 2001. Society of Nuclear Medicine Procedure Guideline for
Hepatobiliary Scintgraphy. Version 3.0, 23 June 2001.
Edgren, A. R. 2001. Gallbladder nuclear medicine scan. Encyclopedia of Medicine.
Silberstein, E. B., MD, Chair (University of Cincinnati Medical Center, Cincinnati, OH);
Abass, A., MD (Hospital of the University of Pennsylvania, Philadelphia, PA);
Balon, H. R., MD (William Beaumont Hospital, Royal Oak, MI); Becker, D., MD
(Weill Cornell Medical School, New York, NY); Charkes, N. D., MD (Temple
University, Philadelphia, PA); Clarke, S. E. M., MD (Guy’s and St. Thomas
NHS Foundation Trust, School of Medicine, King’s College, London);
Divgi, C. R., MD (Hospital of the University of Pennsylvania, Philadelphia,
PA); Donohoe, K. J., MD (Beth Israel Deaconess Medical Center, Boston,
MA); Delbeke, D., MD, PhD (Vanderbilt University Medical Center, Nashville,
TN); Goldsmith, S. J., MD (Weill Cornell Medical Center, New York, NY);
Meier, D. A., MD (William Beaumont Hospital, Royal Oak, MI); Sarkar, S. D.,
MD (Jacobi Medical Center, North Bronx Healthcare Network, Bronx, NY);
Waxman, A. D., MD (Cedars Sinai Medical Center, Los Angeles, CA).
- Society of Nuclear Medicine Procedure Guideline for Scintigraphy
for Differentiated Papillary and Follicular Thyroid Cancer.
Weber, E. S. 2001. Thyroid nuclear medicine scan. Encyclopedia of Medicine.
*Document implemented to compliment Silberstein’s 2004 research document.