Sestamibi

Sestamibi

File:Tc99 sestamibi 2D structure.svg
File:Tc99 sestamibi 3D.png
Clinical data
[[Regulation of therapeutic goods |Template:Engvar data]]	US FDA: TECHNETIUM_TC-99M_SESTAMIBI_KIT
Pregnancy category	US: C (Risk not ruled out)
Routes of administration	Intravenous
ATC code	V09GA01 (WHO)
Legal status
Legal status	US: ℞-only
Pharmacokinetic data
Bioavailability	NA
Protein binding	1%
Metabolism	Nil
Elimination half-life	Variable
Excretion	Fecal (33%) and renal (27%)
Identifiers
IUPAC name -
CAS Number	109581-73-9
PubChem CID	5384
E number	{{#property:P628}}
ECHA InfoCard	{{#property:P2566}}
Chemical and physical data
Formula	C36H66N6O6Tc
Molar mass	777.852 g/mol

Overview

Sestamibi is a radiopharmaceutical used in nuclear medicine imaging. It is also known as methoxyisobutylisonitrile or MIBI. The radioisotope attached to the sestamibi molecule is technetium-99m, forming ⁹⁹Tc^m-sestamibi (or Tc99m MIBI).

Uses

Its main use is for imaging the myocardium (heart muscle). It is also used in the work-up of primary hyperparathyroidism to identify parathyroid adenomas, for radioguided surgery of the parathyroid and in the work-up of possible breast malignancies.

Cardiac imaging

Technetium-99m sestamibi is a lipophilic cation which, when injected intravenously into a patient, distributes in the myocardium proportionally to the myocardial blood flow. As opposed to Thallium-201, MIBI does not undergo significant redistribution. Single photon emission computed tomography (SPECT) imaging of the heart is performed using a gamma camera to detect the gamma rays emitted by the technetium-99m sestamibi as it decays. Two sets of images are acquired. For one set, the Tc99m MIBI is injected whilst 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 Tc99m MIBI is injected at peak stress and then imaging is performed . The resulting two sets of images are compared with each other to distinguish ischaemic from infarcted areas of the myocardium. This imaging technique is also known as myocardial perfusion imaging (MPI).

Parathyroid imaging

In hyperparathyroidism, one or more of the four parathyroid glands have developed a benign tumor called an adenoma. The affected gland takes up Tc99m MIBI following an intravenous injection. The patient's neck is imaged with a gamma camera to show the tumor.

Breast imaging

Tc99m MIBI is also used in the evaluation of breast nodules. Malignant breast tissues concentrate MIBI to a much greater extent and more frequently than benign disease. As such, limited characterization of breast anomalies is possible. Scintimammography has the highest specificity for breast cancer of any imaging test, but its sensitivity is too low to allow for routine use.

Radioguided surgery of the parathyroids

Following the administration of Tc99m MIBI it collects in overactive parathyroid glands. During surgery, the surgeon can use a probe sensitive to gamma rays to locate the overactive parathyroid before removing it.

References

• Cardiolite.com
• Parathyroid.com
• Myoview.com
• Miraluma