Technetium (^99mTc) sestamibi (

INN Inns are generally establishments or buildings where travelers can seek lodging, and usually, food and drink. Inns are typically located in the country or along a highway; before the advent of motorized transportation they also provided accommo ...

) (commonly sestamibi; USP: technetium Tc 99m sestamibi; trade name Cardiolite) is a pharmaceutical agent used in

nuclear medicine Nuclear medicine or nucleology is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease. Nuclear imaging, in a sense, is "radiology done inside out" because it records radiation emitting ...

imaging. The drug is a

coordination complex A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many ...

consisting of the

radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...

technetium-99m Technetium-99m (99mTc) is a metastable nuclear isomer of technetium-99 (itself an isotope of technetium), symbolized as 99mTc, that is used in tens of millions of medical diagnostic procedures annually, making it the most commonly used medical ra ...

bound to six (sesta=6) methoxyisobutylisonitrile (MIBI)

ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electr ...

s. The anion is not defined. The

generic drug A generic drug is a pharmaceutical drug that contains the same chemical substance as a drug that was originally protected by chemical patents. Generic drugs are allowed for sale after the patents on the original drugs expire. Because the active ch ...

became available late September 2008. A scan of a patient using MIBI is commonly known as a "MIBI scan". Sestamibi is taken up by tissues with large numbers of

mitochondria A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...

and negative plasma membrane potentials. Sestamibi is mainly used to image the

myocardium Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that ...

(heart muscle). It is also used in the work-up of primary

hyperparathyroidism Hyperparathyroidism is an increase in parathyroid hormone (PTH) levels in the blood. This occurs from a disorder either within the parathyroid glands (primary hyperparathyroidism) or as response to external stimuli (secondary hyperparathyroidism). ...

to identify

parathyroid Parathyroid glands are small endocrine glands in the neck of humans and other tetrapods. Humans usually have four parathyroid glands, located on the back of the thyroid gland in variable locations. The parathyroid gland produces and secretes par ...

adenomas, for radioguided surgery of the parathyroid and in the work-up of possible

breast cancer Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or a re ...

Cardiac imaging (MIBI scan)

A ''MIBI scan'' or ''sestamibi scan'' is now a common method of cardiac imaging. Technetium (^99mTc) sestamibi is a

lipophilic Lipophilicity (from Greek λίπος "fat" and φίλος "friendly"), refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. Such non-polar solvents are themselves lipop ...

cation which, when injected intravenously into a patient, distributes in the

proportionally to the myocardial blood flow. Single photon emission computed tomography (

SPECT Single-photon emission computed tomography (SPECT, or less commonly, SPET) is a nuclear medicine tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera (that is, ...

) imaging of the heart is performed using a

gamma camera A gamma camera (γ-camera), also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy. The applications of scintigraphy include early drug development ...

to detect the

gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...

s emitted by the technetium-99m as it decays. Two sets of images are acquired. For one set, ^99mTc MIBI is injected while the patient is at rest and then the myocardium is imaged. In the second set, the patient is stressed either by exercising on a treadmill or pharmacologically. The drug is injected at peak stress and then imaging is performed. The resulting two sets of images are compared with each other to distinguish

ischemic Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems w ...

from

infarcted Infarction is tissue death ( necrosis) due to inadequate blood supply to the affected area. It may be caused by artery blockages, rupture, mechanical compression, or vasoconstriction. The resulting lesion is referred to as an infarct (from t ...

areas of the myocardium. This imaging technique has a sensitivity of around 90%. Resting images are useful only for detecting tissue damage, while stress images will also provide evidence of coronary artery (ischemia) disease.

With dipyridamole (Persantine MIBI scan)

When combined with the drug

dipyridamole Dipyridamole (trademarked as Persantine and others) is a nucleoside transport inhibitor and a PDE3 inhibitor medication that inhibits blood clot formation when given chronically and causes blood vessel dilation when given at high doses over a s ...

, a brand name of which is Persantine, a MIBI scan is often referred to as a ''Persantine MIBI scan''.

Parathyroid imaging

primary hyperparathyroidism Primary hyperparathyroidism (or PHPT) is a medical condition where the parathyroid gland (or a benign tumor within it) produce excess amounts of parathyroid hormone (PTH). The symptoms of the condition relate to the resulting elevated serum calcium ...

, one or more of the four parathyroid glands either develops a benign tumor called an

adenoma An adenoma is a benign tumor of epithelial tissue with glandular origin, glandular characteristics, or both. Adenomas can grow from many glandular organs, including the adrenal glands, pituitary gland, thyroid, prostate, and others. Some adenom ...

or undergoes

hyperplasia Hyperplasia (from ancient Greek ὑπέρ ''huper'' 'over' + πλάσις ''plasis'' 'formation'), or hypergenesis, is an enlargement of an organ or tissue caused by an increase in the amount of organic tissue that results from cell proliferati ...

as a result of homeostatic dysregulation. The parathyroid gland takes up ^99mTc MIBI following an intravenous injection, and the patient's neck is imaged with a gamma camera to show the location of all glands. A second image is obtained after a washout time (approximately 2 hours), and mitochondria in the oxyphil cells of the abnormal glands retaining the ^99mTc are seen with the gamma camera. This imaging method will detect 75 to 90 percent of abnormal parathyroid glands in primary hyperparathyroidism. An endocrine surgeon can then perform a focused

parathyroidectomy Parathyroidectomy is the surgical removal of one or more of the (usually) four parathyroid glands. This procedure is used to remove an adenoma or hyperplasia of these glands when they are producing excessive parathyroid hormone (PTH): hyperparathy ...

(less invasive than traditional surgery) to remove the abnormal gland.

Radioguided surgery of the parathyroids

Following administration, ^99mTc MIBI collects in overactive parathyroid glands. During

surgery Surgery ''cheirourgikē'' (composed of χείρ, "hand", and ἔργον, "work"), via la, chirurgiae, meaning "hand work". is a medical specialty that uses operative manual and instrumental techniques on a person to investigate or treat a pat ...

, the surgeon can use a probe sensitive to gamma rays to locate the overactive parathyroid before removing it.

Thyroid imaging

Several case reports have demonstrated that ^99mTc MIBI scan may be useful to differentiae the sub-type of amiodarone-induced thyrotoxicosis. Lack of MIBI uptake in the thyroid is compatible with a form of

thyroiditis Thyroiditis is the inflammation of the thyroid gland. The thyroid gland is located on the front of the neck below the laryngeal prominence, and makes hormones that control metabolism. Signs and symptoms There are many different signs and sympto ...

(type-2 AIT) which may respond to treatment with steroids.

Breast imaging

The drug is also used in the evaluation of breast nodules. Malignant breast tissues concentrate ^99mTc MIBI to a much greater extent and more frequently than benign disease. As such, limited characterization of breast anomalies is possible. Scintimammography has a high

sensitivity and specificity ''Sensitivity'' and ''specificity'' mathematically describe the accuracy of a test which reports the presence or absence of a condition. Individuals for which the condition is satisfied are considered "positive" and those for which it is not are ...

for breast cancer, both more than 85%. More recently, breast radiologists administer lower doses of ^99mTc sestamibi (approximately ) for Molecular Breast Imaging (MBI) scans which results in a high sensitivity (91%) and high specificity (93%) for breast cancer detection. It however carries a greater risk of ''causing'' cancer, making it not appropriate for general

breast cancer screening Breast cancer screening is the medical screening of asymptomatic, apparently healthy women for breast cancer in an attempt to achieve an earlier diagnosis. The assumption is that early detection will improve outcomes. A number of screening tests ...

in patients. The last reference listed refers to a dose, which is given with the Dilon single-head system, which requires a higher dose since only one camera is utilized (meaning the camera needs to be able to see through more tissue). A dose, which is used in the other two commercially available MBI systems is essentially equivalent to a mammogram () or a

tomosynthesis Tomosynthesis, also digital tomosynthesis (DTS), is a method for performing high-resolution limited-angle tomography at radiation dose levels comparable with projectional radiography. It has been studied for a variety of clinical applications, incl ...

exam (). Since even small doses of ionizing radiation are believed to carry some risk of causing cancer, MBI is usually limited to women with

dense breast tissue Dense breast tissue, also known as dense breasts, is a condition of the breasts where a higher proportion of the breasts are made up of glandular tissue and fibrous tissue than fatty tissue. Around 40–50% of women have dense breast tissue and o ...

, which often can result in inconclusive mammograms. Researchers continue to devote their time to improving the technology, changing scan parameters, and reducing dose to patients.

References

External links

Cardiolite official pageMolecular Breast Imaging
{{DEFAULTSORT:Technetium (99mtc) Sestamibi Radiopharmaceuticals Bristol Myers Squibb Technetium-99m Organometallic compounds Conjugated nitriles Methoxy compounds Technetium compounds