Magnetic Resonance Imaging and malignancy detection
MRI is very sensitive for detecting invasive carcinoma, usually very close to 100% in fact. DCIS is detected with a sensitivity range of 40-100%, even when the lesions are not detectable from the mammography X-ray, or physical examination.
With MRI using an injected contrast agent, cancers become brighter and more easy to diagnose, which is an advantage that MRI has over mammography and ultrasound.
This page is getting pretty old, but still very useful. However, I just want to let you know that I have created a newer page with more up-to-date information on MRI and Malignancy Detection.
Malignant-looking borders/outer margins of a lesion
The features revealed through magnetic resonance imaging which point towards a malignant condition are often associated with outer irregular borders of a lesion. Malignant lesions commonly feature irregular or spiculated borders, or rim-enhancement on the periphery of the lesion.
On the other hand, features which suggest a more benign condition might be a mass with smooth and lobulated borders, a mass with minimal or no enhancement, a mass with non enhancing internal septations, and patchy parenchymal enhancement.
MRI scans of the breast almost always use an intravenous injection of a medicine that “enhances” the visibility of lesions. Sometimes this process is referred to a dynamic contrast enhanced MRI scan, or DCE MRI.
The injected medicine is called an “MRI contrast agent“, and it works by making lesions appear brighter on the MRI images than the surrounding normal tissue. This increase in contrast between normal and abnormal tissue makes the lesion easier for the radiologist to see, helping to distinguish between benign and malignant tumors.
During the scan, a malignant lesion will tend to demonstrate a rapid increase in signal intensity (within the first 1-2 minutes) after the contrast injection, and is often followed by a ‘wash-out‘ (the lesion becomes less bright) of contrast on images which appear in the minutes that follow.
Benign lesions, on the other hand, tend to exhibit a slow, progressive rise in intensity of the signal with no wash-out of contrast. The contrast enhanced lesion is classified according to the morphology of the contrast, and also by the ‘kinetics‘ or changes in time of the contrast enhancing areas.
It should also be noted that MRI improves contrast and definition for not just cancer, but for related, non-cancerous and pre-cancerous abnormalities such as mastitis, radial scar, atypical hyperplasia, lobular neoplasia, fibroadenomas, sclerosing adenosis, and fat necrosis.
Even though MRI is very useful in determining whether or not a tumor is malignant, the ‘specificity‘, which means the ability to correctly predict on the MRI report that a lesion is truly benign, is limited. This is due to the overlap in the enhanced morphologic appearance of both benign and malignant lesions.
However, MRI expertise in determining the ‘specificity‘ of MRI related data continues to rise. Specificity of MRI is over 80% for solid masses of 1cm or larger.
MRI breast cancer screening may be beneficial for some higher risk groups
Sometimes MRI screening is utlizied for women who have a personal or familial history of breast cancer. MRI screening for women with a hereditary disposition of breast cancer has proven to be clinically valuable, finding about 12% more malignancies than traditional screening methods.
And, a high percentage of MRI detected breast cancers are found at either the DCIS or minimal breast cancer stage.
Breast cancer MRI screening is not practical on a large scale. However, various focus groups have concluded that the use of MRI in breast cancer screening may be recommended for women who, for a variety of reasons, possess a 20% to 25% increased lifetime risk of breast cancer development.
There does seem to be agreement that women who have had prior treatments for Hodgkin disease, and also women with a pronounced family history of either ovarian or breast cancer, be included in this higher-risk, MRI-recommended group. However, there is insufficient convincing evidence and no consensus that other ‘high risk‘ women, for example, those with dense breast tissue and even women with atypical hyperplasia, require MRI screening.
Below is a little quiz with common Q&A on MRI and Malignancy detection… :
- When is MRI usually performed? It is performed after you have had a biopsy that’s positive for cancer, and your doctor needs more information about the extent of the disease. In certain situations, such as for women with high risk of breast cancer, breast MRI may be used with mammograms as a screening tool for detecting breast cancer.
- Why is MRI done? Breast MRI is most often used to screen for breast cancer in women thought to have a high risk of the disease. Your doctor may recommend a breast MRI if you’ve been diagnosed with breast cancer, and your doctor wants to determine the extent of the cancer, you have a suspected leak or rupture of a breast implant, you’re at a high risk of breast cancer (family history, etc), you have a strong family history of breast cancer, you have very dense breast tissue, and mammogram didn’t detect a prior breast cancer, and/or you have a history of precancerous breast changes such as atypical hyperplasia or lobular carcinoma in situ, a strong family history of breast cancer and dense breast tissue.
- What does MRI show? Like CT scans, MRI creates cross-section pictures of your insides. But MRI uses strong magnets instead of radiation to make the images. An MRI scan can take cross sectional views from many angles, as if someone were looking at a slice (view) of your body from the front, from the side, or from above your head. MRI creates pictures of soft tissue parts of the body that are sometimes hard to see using other imaging tests. MRI is very good at finding and pinpointing some cancers. An MRI with contrast dye is the best way to see brain tumors. Using MRI, doctors can sometimes tell if a tumor is benign (not cancer) or malignant (cancer). MRI can also be used to look for signs that cancer may have metastasized (spread) from where it started to another part of the body. MRI images can also help doctors plan treatment such as surgery and/or radiation therapy.
- How does it work? An MRI scanner is a cylinder or tube that holds a large, very strong magnet. As you lye on the table that slides within the tube, the device surrounds you with a powerful magnetic field. The magnetic source then causes the centers of hydrogen atoms in your body to line up in one direction. Once the atoms are lined up, the MRI machine then gives off a burst of radio frequency waves. These waves cause the hydrogen nuclei to change direction. When they return to their original position, they give off certain signals that the scanner detects. Hydrogen nuclei in the body tissues change directions in different ways. A computer takes signals from these changes and converts them into a black and white picture.
- What are some known risks for MRI? A breast MRI is a safe procedure that doesn’t expose you to radiation. But as with other tests, a breast MRI has risks such as a risk of false-positive results, or a risk of reaction to the contrast dye used.
- How do I prepare for my MRI appointment? Schedule your MRI for the beginning of your menstrual cycle, tell your doctor about any allergies you have, tell your doctor if you have kidney problems, tell your doctor if you’re pregnant or if you’re nursing, don’t wear anything metallic during the MRI, and tell your doctor about implanted medical devices.
- Are there any possible complications? People can be hurt in MRI machines if they take metal items into the room, some people become very uneasy and even panic when lying inside the MRI scanner, some people also react to the contrast material- these include nausea, pain at the needle site, a headache that develops a few hours after the test is over, and low blood pressure leading to a feeling of lightheadedness or faintness (this is rare). Be sure to let your health care team know if you have any of these symptoms.
- What else should I know about MRI screening? People who are overweight may have trouble fitting into the MRI machine, the use of MRI during pregnancy has not been well studied, MRI is usually not done in the first 12 weeks of pregnancy unless there is a strong medical reason to use it, do not bring any credit cards or other items with magnetic scanning strips with you into the exam room (the magnet could wipe out the information stored on them), MRI does not expose you to radiation, and not all hospitals and imaging center have dedicated breast MRI equipment available.
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