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 accomm ...

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

nuclear medicine Nuclear medicine (nuclear radiology, nucleology), is a medical specialty involving the application of radioactivity, radioactive substances in the diagnosis and treatment of disease. Nuclear imaging is, in a sense, ''radiology done inside out'', ...

imaging. The drug is a

coordination complex A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of chemical bond, bound molecules or ions, that are in turn known as ' ...

consisting of the

radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...

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 Radiophar ...

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

ligand In coordination chemistry, a ligand is an ion or molecule with a 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 el ...

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 cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is us ...

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

myocardium Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall o ...

(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 hyperparathyroi ...

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 pa ...

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

breast cancer Breast cancer is a cancer that develops from breast tissue. Signs of breast cancer may include a Breast lump, lump in the breast, a change in breast shape, dimpling of the skin, Milk-rejection sign, milk rejection, fluid coming from the nipp ...

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 language, Greek λίπος "fat" and :wikt:φίλος, φίλος "friendly") is the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. Such compounds are c ...

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 ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...

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 ...

from infarcted 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, sold under the brand name Persantine among others, is an antiplatelet drug of the nucleoside transport inhibitor and PDE3 inhibitor class that inhibits blood clot formation when given chronically and causes blood vessel dilatio ...

, 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 calciu ...

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

adenoma An adenoma is a benign tumor of epithelium, epithelial tissue with glandular origin, glandular characteristics, or both. Adenomas can grow from many glandular organ (anatomy), organs, including the adrenal glands, pituitary gland, thyroid, prosta ...

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 Tissue (biology), organic tissue that results from ...

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): hyperpa ...

(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 is a medical specialty that uses manual and instrumental techniques to diagnose or treat pathological conditions (e.g., trauma, disease, injury, malignancy), to alter bodily functions (e.g., malabsorption created by bariatric surgery s ...

, 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 differentiate 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. Thyroiditis is a group of disorders that all cause thyroi ...

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

steroids A steroid is an organic compound with four fused rings (designated A, B, C, and D) arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter mem ...

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 In medicine and statistics, sensitivity and specificity mathematically describe the accuracy of a test that reports the presence or absence of a medical condition. If individuals who have the condition are considered "positive" and those who do ...

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 exam (). In order to keep the radiation doses to patients as low as reasonably achievable, 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 an ...

, where the medical benefit of the scan outweighs the potential risk of radiation exposure. For the same reason, the administered activity is kept low. This can potentially result in noisy images, which in turn causes 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 Drugs developed by Bristol Myers Squibb Isocyanides Diagnostic endocrinology Diagnostic medical imaging Methoxy compounds Organometallic compounds Radiopharmaceuticals Technetium-99m Technetium compounds