chemistry

Molecular breast imaging

Molecular breast imaging is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Molecular breast imaging rather than just read about it. In short: Molecular breast imaging (MBI), also known as scintimammography, is a type of breast imaging test that is used to detect cancer cells in breast tissue of individuals who have had abnormal mammograms, especially for those who have dense breast tissue, post-operative scar tissue or breast implants. MBI is not used for screening or in place of a mammogram.

Key takeaways

Molecular breast imaging belongs to chemistry; place it in that map before memorising details.
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Reproduce the core statement of Molecular breast imaging from memory before moving on to harder problems.

Reference excerpt

Molecular breast imaging (MBI), also known as scintimammography, is a type of breast imaging test that is used to detect cancer cells in breast tissue of individuals who have had abnormal mammograms, especially for those who have dense breast tissue, post-operative scar tissue or breast implants. MBI is not used for screening or in place of a mammogram. Rather, it is used when the detection of breast abnormalities is not possible or not reliable on the basis of mammography and ultrasound alone. When mammography plus ultrasound are insufficient to characterize an abnormality, the gold standard next step is Magnetic Resonance Imaging (MRI) of the breast. However, in patients with contraindications (e.g. certain implantable devices) or who prefer to avoid MRI (claustrophobia, discomfort), use of scintimammography is an acceptable alternative.

Mechanism Scintiamammorgraphy is based on the principle of scintigraphy, where the gamma radiation emitted from injected radiopharmaceuticals is measured by gamma cameras. Cancer cells take up radiopharmaceutical at a higher rate than surrounding normal tissue, and as such they show up on scintigraphy as areas of increases gamma radiation emission. A limitation to this principle is that not all breast lesions with metabolic activity higher than background are cancerous (eg fibroadenoma), and as such judicious use of molecular breast imaging by breast imagers is required. The most common radiopharmaceutical used in MBI is 99mTc-sestamibi, with doses of 240-300 MBq in current protocols, resulting in an effective dose to a patient of around 2.4 mSv. Earlier iterations of MBI required much higher doses of radiation up to 1100 MBq, which in part led to MBI falling out of favor in the latter part of the last century. However advances in gamma camera technology such as breast specific gamma imaging (BSGI) have allowed for quality resolution at much lower radiation doses, and as such there has been increasing use of MBI. Molecular breast imaging added to screening mammogram increases cancer detection rate by about 7-16 positive results per 1000 tests completed, however the dose of radiation experienced by the patient is increased.

Procedure The procedure is conducted according to practice guidelines corresponding to the region where they are performed (American College of Radiology guidelines in the U.S.). A patient can expect to receive an injection of radiopharmaceutical agent intravenously in the arm contralateral to the breast under investigation. After waiting 5–10 minutes, the breast tissue is placed into the MBI system and a series of images are obtained. Imaging time for both breasts is approximately 40 minutes. For lesions identifiable on MBI but not mammography or ultrasound, MBI guided biopsy is appropriate.

Equipment Breast-specific gamma cameras have been developed with a smaller field of view than conventional cameras, allowing higher resolution imagery and compression of the breast as in x-ray mammography (which improves detection of smaller lesions).

Clinical indications Mammography is widely accepted as the first-line screening option for the detection of breast cancer, with a sensitivity for detection of cancer at around 85-90%. However, in patients with dense breast tissue or those with risk of breast cancer greater than 20%, the sensitivity of mammography drops significantly, with some studies reporting a sensitivity of less than 50%. In these patients, many centers utilize breast ultrasound as additional screening modality, which studies have shown increases breast cancer detection by 2 cancers detected per 1000 people screened. Ultrasound also plays an important role in further characterization of indeterminate lesions seen on screening mammography, but it does result in a significant increase in false positive rate when compared to mammography alone. Breast MRI is considered the gold-standard in supplemental imaging of dense breasts, with an increase in cancer detection of about 15 cancers per 1000 screens. In patients where MRI is contraindicated (certain implantable devices, certain kidney conditions) or in those who prefer to avoid MRI (claustrophobia), molecular breast imaging is a viable alternative. MBI has shown to increase detection of breast cancer in dense breasts by 7-16 cancers per 1000 screens.

See also Technetium (99mTc) sestamibi Nuclear medicine Positron emission mammography

References

External links Scintimammography entry in the public domain NCI Dictionary of Cancer Terms This article incorporates public domain material from Dictionary of Cancer Terms. U.S. National Cancer Institute.

Illustrations

Worked examples

Example 1 — a first encounter with Molecular breast imaging

Start with the simplest possible case. Write down what Molecular breast imaging claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Molecular breast imaging before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Molecular breast imaging ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Molecular breast imaging

In research: Molecular breast imaging appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Molecular breast imaging in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Molecular breast imaging is common in secondary-school and first-year university syllabi. It links to neighbouring topics 2D nuclear medical imaging, Breast imaging, Cancer screening, so understanding it makes those chapters shorter.
In everyday life: Look for Molecular breast imaging outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Molecular breast imaging in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Molecular breast imaging means in your own words.
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Work through the three examples above with pen and paper.
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Frequently asked questions

What is Molecular breast imaging in simple terms?

Why does Molecular breast imaging matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Molecular breast imaging?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Molecular breast imaging.