12 Apr, 2024

Breast MRI vs Mammogram vs Ultrasound: Which Imaging of the Breast Should You Choose?

If you have just found a lump in your breasts, received an abnormal test result, or want a routine breast screening to stay on top of your health, but you don't know which type of breast imaging test to choose, you've just found a complete guide that answers all your questions.

Scan.com offers breast imaging tests, including mammograms, ultrasound, and MRI, from over 200+ imaging centres nationwide, with flexible appointment times. The choice is all yours: your preferred location, budget, and time. 

Confused about which breast imaging test to choose? You can book a private consultation to speak with an expert clinician who’ll review your medical history, needs and goals and provide tailored advice about which scan is most suitable for you. If you do decide to book a scan with us, we’ll discount your fee by £50 automatically. 

Now, let’s get into the guide: Breast MRI vs Mammogram vs Ultrasound: Which Imaging of the Breast Should You Choose?

Mammogram vs Ultrasound - How Do They Work?

What Is a Mammogram, and How Does It Work?

A mammogram (also called mammography) is an imaging test that uses X-rays to screen the breasts for early signs of cancer and other breast diseases where there are no presenting symptoms. It is also used as a diagnostic tool to investigate breast pain, changes in breast appearance, and lumps, which may be tumours, fibroids, or cysts. 

During a mammogram, a mammographer (skilled scan technician) will help position your breasts one at a time between two parallel flat plates. The top plate (called a paddle) will slowly descend until it compresses your breast. Some women may find this mildly uncomfortable or painful, depending on factors such as breast size, presence of implants, tolerance level, and whether the scan is done before or during their menstrual period when the breasts may be fuller and more tender. 

With your breast firmly secured, an X-ray machine will pass a beam of rays through the breasts to a detector located below the bottom plate. An image will be formed representing shadows cast by different tissue types in your breasts, depending on how much X-rays they absorb or let pass through them. 

What Is an Ultrasound, and How Does It Work?

An ultrasound (also called ultrasonography or sonography) is a painless, non-invasive imaging test that uses sound waves to visualise the organs and soft tissues (e.g., fat, muscles, and blood vessels) inside the body. 

During an ultrasound, you'll need to lie down on your back or side. A sonographer (ultrasound technician) will move a small hand-held device (called an ultrasound probe or transducer) over the area(s) of your breasts to be examined. 

The transducer sends a burst of sound waves into your breasts. These waves will bounce off different tissue types with varying speeds and intensities and return as echoes, which will be converted into a detailed image by a nearby computer. It is by detecting differences in the echoes received that ultrasound can highlight abnormalities surrounded by healthy tissue and determine their characteristics.

What Are the Key Differences Between a Breast Ultrasound vs Mammogram?

  • Imaging Quality: Mammograms are highly sensitive in detecting and visualising small tumours, distortions, and microcalcifications (specks of hardened calcium deposits), which can sometimes indicate cancer at its early stages. It is primarily used for breast screening.

Ultrasound, on the other hand, provides real-time imaging that allows for the detection and thorough assessment of abnormalities in the breast tissue. It is particularly effective at distinguishing between cystic (fluid-filled) and solid masses (tumours), and it can also define whether they are benign (non-cancerous) or malignant (cancerous). Although, additional tests like a biopsy may be needed for a confirmative diagnosis. 

  • Cost: A breast ultrasound is cheaper than a mammogram.

  • Time: Mammograms usually take 15 to 20 minutes, while an ultrasound may take up to 30 minutes or more.

  • Risks: Due to their use of X-rays, mammograms aren't considered safe for pregnant women. Additionally, repeated use of mammograms in younger women carries an elevated risk of radiation-induced cancer, which is one reason why the recommended age for annual mammograms is age 40 years and up. In contrast, there are no risks associated with breast ultrasound. 

  • Limitations: Compared to a mammogram, an ultrasound is not able to provide a complete view of the breast in one image nor can it penetrate certain deep areas inside the breasts, particularly in very large breasts. Also, it may not detect calcifications. 

In addition, mammograms are less effective in women with dense breasts. While dense breasts are common and normal, they are also a risk factor for breast cancer. There is said to be an estimated two- to six-fold increased breast cancer risk among women with extremely dense breast tissue compared to women with entirely fatty breasts.

On a mammogram, soft tissues like fluids, muscles, and fat show as shades of grey, while high-density tissues appear white. However, both cancerous and benign tumours also appear light grey or white, making them hard to detect in dense breasts. Meanwhile, a breast ultrasound can easily detect and distinguish tumours from healthy breast tissues in dense breasts, as cancerous masses typically appear darker. 

Mammogram vs Ultrasound - Which Is Better?

A mammogram is the gold-standard breast cancer screening tool — the only one known to reduce deaths by breast cancer through early detection, according to research. When done routinely, it can detect malignant (cancerous) growths up to 3 years before they become noticeable, promoting early intervention and significantly improving survival and cure rates. 

Ultrasound isn't often used independently as a routine screening test because it can easily miss early signs of breast cancer, such as microcalcifications. It is usually ordered to investigate a visible lump or for further evaluation and characterisation of an abnormality found on a mammogram or clinical breast exam. There are, however, cases where a breast ultrasound scan might be an appropriate screening solution, such as when:

  • You have breast implants.

  • You are pregnant and have breast health concerns.

  • You can feel a palpable lump but a mammogram failed to detect an abnormality.

  • You have dense breasts.

  • You have an average to high risk of breast cancer, or you are experiencing breast cancer symptoms but are younger than the recommended annual mammogram age (i.e., 40 to 50 years and above).

When considering breast ultrasound vs mammogram age ranges, you should keep in mind that ultrasound is significantly more accurate and serves as a superior initial imaging test compared to screening mammograms for detecting and correctly identifying cancer in women younger than 45 years with dense breasts. It is as women age past 50 years that mammograms become progressively sensitive and accurate for early cancer detection, owing to natural changes in breast composition, where breasts tend to become more fatty and less dense. 

Speaking about dense breasts, how do you know if you have them? - It isn't determined by size or firmness but by how much fibrous and glandular tissue is in your breast compared to fatty tissue. You can’t feel it with your hands, nor can a doctor during a breast physical exam. The only way to find out is through a mammogram, making it the first port of call in detecting cancer. Your mammogram report should say if you have fatty, scattered, heterogeneously dense or extremely dense breasts. 

In summary, a mammogram and ultrasound are complementary to each other, and one shouldn’t be picked over the other, especially for first-time screening, as a mammogram provides valuable information about breast density. Subsequently, the decision about whether to continue screening with both mammogram and ultrasound, ultrasound alone, or another imaging modality (such as a breast MRI) should be made in consultation with a doctor. 

Diagnostic Breast Ultrasound vs Mammogram

A mammogram does an outstanding job of detecting abnormal breast tissues called masses, but it cannot definitively differentiate between a cyst and cancer on its own. Following the discovery of a lump by touch or an abnormal mammogram, a follow-up ultrasound (or diagnostic breast ultrasound) is necessary to check whether the mass is a cyst (i.e., a fluid-filled mass) or a tumour (i.e., a solid mass). While cysts are commonly benign, the presence of a tumour doesn't always indicate cancer.

To determine the nature of a tumour, a diagnostic breast ultrasound may be employed instead of a mammogram to closely examine a tumour's size, shape, and margin, as well as the characteristics of blood vessels that carry blood in, around and out of the area. Cancerous tumours are known to have poorly formed and chaotic vascular networks.

Other Breast Imaging Options

An imaging test that can easily join in the mammogram vs ultrasound for breast cancer detection debate is a breast MRI. 

Magnetic resonance imaging (MRI) is an imaging technique that uses a strong magnetic field and pulse(s) of high-frequency radio waves to create three-dimensional (3D) detailed images of the body’s internal structures, including bones, organs, and soft tissues.  

During an MRI for breast cancer, you lie on a bed that slides into a cylinder-shaped machine. Inside, the scanner generates a magnetic field, which forces the protons in your breast tissues to align with it. A high-frequency pulse of radio waves is then applied from an opposite direction to disrupt this alignment, and when it is turned off, the protons realign, emitting their own little wave (or signal) in the process. With the help of a computer, the MRI scanner processes the signals received into cross-sectional detailed images of the breast.

In some cases, a gadolinium-based contrast agent might be administered via an injection or intravenous (IV) fluid before an MRI to enhance the visualisation of healthy and abnormal tissues. 

Is Breast MRI Better Than Ultrasound?

Like ultrasound, breast MRI is typically used to evaluate palpable masses or abnormalities found on a mammogram. However, it is more highly sensitive in detecting breast cancer.

In one study with 529 women with higher risk of cancer, researchers compared three screening methods: mammography, high-frequency breast ultrasound, and MRI. MRI showed higher sensitivity (91%), detecting both preinvasive cancers in the lining of breast ducts (known as intraductal breast carcinoma or stage 0 cancer) and invasive cancers. This result was comparable to ultrasound (40%) and mammogram (33%), as well as the combination of both (49%).

There are several other studies that prove an MRI for breast cancer is better than ultrasound as well as mammograms, particularly for detecting cancer early in women with higher risk. These women are those that have several risk factors, including:

  • Personal history of cancer or non-cancerous diseases.

  • Family history of breast or ovarian cancer.

  • Previous radiation therapy to the chest or breast region.

  • A BRCA1 or BRCA2 inherited gene mutation.

  • A genetic disorder such as Li-Fraumeni or Cowden syndrome.

  • Early menarche (first menstrual period) and late-onset menopause.

Breast MRI vs Mammograms - Which to Choose and Why?

Here is a quick breast MRI vs mammogram comparison to help you make an informed decision on which to use and why.

  • Sensation: An MRI for breast cancer scan is a painless, non-invasive procedure. However, people with claustrophobia might experience discomfort due to the enclosed nature of the MRI scanner; in such cases, an open MRI may be used. With a mammogram, you might feel a mild to moderate level of discomfort or pain due to the compression applied by the machine and may likely experience soreness afterwards.

  • Time: A mammogram usually takes 15 to 20 minutes. A breast MRI can take 30 to 90 minutes. 

  • Sensitivity: Mammograms are known to detect up to 98% of cancers in fatty breasts, but this sensitivity drops to 30% - 48% in extremely dense breasts. Its sensitivity may also be diminished in the presence of breast implants. Meanwhile, an analysis of 22 different studies concluded that MRI is the most sensitive imaging modality, compared to ultrasound and mammography, for detecting cancer in non-high-risk women with dense breasts. A breast MRI scan can also detect small-sized lesions missed by mammograms and provide a comprehensive evaluation of unidentified abnormalities presented by them. 

  • False Positives: MRI has a variably high false-positive rate, which means it can sometimes identify a benign mass as cancerous, leading to unnecessary additional imaging tests, tissue sampling (a biopsy), and psychological distress. This is why screening with MRI isn’t advised for women with low to average risk. 

Although not as high, a mammogram is prone to making the same mistakes, more commonly in women with dense breasts, a history of breast biopsies, high familial risk, or those taking oestrogen. 

  • Risk: Unlike mammograms, MRI doesn’t use radiation, so it is safe for use on pregnant women and repeated, continuous use in younger women. Additionally, the use of a strong magnetic field means MRI is contraindicated (i.e., not suitable for use) for people with metallic implants such as cardiac pacemakers, intracranial aneurysm clips, cochlear implants, drug infusion pumps, and stainless-steel intrauterine contraceptive devices. 

Now to the question: Breast MRI vs Mammograms - which to choose and why? - If you are aged 40 years and older with a higher risk of breast cancer, screening with MRI can increase the chances of early detection. In fact, it is recommended that you undergo an annual screening mammogram and a breast MRI. The European Society of Breast Imaging (ESUOBI) recommends scheduling your screening tests on days 7 to 14 of your menstrual cycle to get a clear and accurate visual of the breasts.

However, younger women below the recommended mammogram age or with dense breasts may be recommended imaging with MRI alone or after an ultrasound. Suppose you are at high risk but can’t undergo an MRI due to contraindications. In that case, you will benefit from using screening mammography and breast ultrasound together.

Ultrasound vs Mammogram vs MRI - the bottom line

Between an ultrasound vs mammogram vs MRI, your choice for a diagnostic imaging test or routine breast cancer screening test—as well as how frequently you use them—depends on several factors, including age, risk factors, medical history, and specific circumstances. 

Next steps

Book your mammogram without a GP referral. Skip NHS waiting lists.

Book the breast ultrasound you need. With results ready within seven (7) days, you can fast-track your diagnosis and get timely intervention. 

Book a private MRI for breast cancer and get 1:1 expert clinical consultations before and after your scan. 


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