Positron emission mammography (PEM) is a

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 emi ...

imaging modality used to detect or characterise

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 ...

Mammography Mammography (also called mastography) is the process of using low-energy X-rays (usually around 30 kVp) to examine the human breast for diagnosis and screening. The goal of mammography is the early detection of breast cancer, typically through ...

typically refers to

x-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

imaging of the breast, while PEM uses an injected

positron The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. It has an electric charge of +1 '' e'', a spin of 1/2 (the same as the electron), and the same mass as an electron. When a positron collide ...

emitting

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers ( mass num ...

and a dedicated scanner to locate breast tumors. Scintimammography is another nuclear medicine breast imaging technique, however it 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 ...

. Breasts can be imaged on standard whole-body PET scanners, however dedicated PEM scanners offer advantages including improved resolution. PEM is not recommended for routine use or for

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 part due to higher

radiation dose Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel ...

compared to other modalities. Compared to

breast MRI One alternative to mammography, breast MRI or contrast-enhanced magnetic resonance imaging (MRI), has shown substantial progress in the detection of breast cancer. Uses Some of the uses of MRI of the breasts are: screening for malignancy in women ...

, PEM offers higher specificity. Specific indications can include "high-risk patients with masses > 2 cm or aggressive malignancy and serum tumor marker elevation". ¹⁸F-FDG is the most common radiopharmaceutical used for PEM.

Equipment

PEM uses a specialised scanning system. Though some systems resemble a small PET scanner with a ring of detectors, others consist of a pair of gamma radiation detectors placed above and below the breast. On these systems, mild breast compression is applied to spread the breast and reduce its thickness. The detection process is identical to standard PET scanners. Positrons emitted by the injected ¹⁸F-FDG annihilate on interaction with

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have n ...

s in tissue, leading to the emission of a pair of

photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they alwa ...

s travelling in opposite directions. The detection of two simultaneous photons indicates the emission of a positron at a point on the line linking the two detection events. An image is the reconstructed from the collected emission data.

History

Mammography using positron emitters was first proposed in 1994. PEM is now approved in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

and Europe for post-diagnosis imaging, with multiple commercial systems available.

References

{{Medical imaging 2d nuclear medical imaging Breast imaging Cancer screening

Equipment

History

See also

References