Currently, mammography is the most effective technology available for breast cancer screening. But, aside from the conventional mammography, there are several techniques that can be used for screening. These techniques are:
- Digital Mammography
- Computer-Aided Detection
- PET scan
- Electrical Impedance Scanning
- Ductal Lavage
The ultrasound, also referred to as sonography, is a technique in which high-frequency sound waves, unhearable for humans, are bounced off tissues and internal organs. The echoes generated produce a picture known as a sonogram. This form of imaging is commonly used to distinguish between solid tumors and cysts. An ultrasound is sometimes also used to examine lumps that are difficult to see on a mammogram. The ultrasound can also be used as part of other diagnostic procedures, such as needle biopsies (the removal of tissue, or fluid, through the use of needles).
Ultrasounds are not used for routine breast exams, because this technique is not suitable for detecting early signs of cancer.
Compared to the conventional mammograms, digital mammograms use computerized images instead of x-ray film. Before printed on film, the images are displayed on a monitor, where they can be modified (enhanced, magnified, etc.). The patient won't notice a difference between the conventional and digital mammogram, as they are both performed using the same procedure.
Digital mammography has a few advantages over conventional mammography. As previously indicated the images are electronically stored, this digital aspect of the mammograms makes long-distance consultations easier. There is also an improved accuracy with the digital mammograms, which decreases the number of follow-ups required. Despite these benefits, digital mammography does not increase the number of breast cancer tumors found in women.
For more information about mammography, visit our section on mammograms.
Computer-aided detection (CAD) is the use of computers to bring suspicious areas on a mammogram to the radiologist's attention. It is used after the radiologist has done the initial review of the mammogram, and is performed by scanning the mammogram into the computer.
MRI (Magnetic Resonance Imaging) is the creation of detailed pictures of areas inside the body through the use of a magnet, this form of imaging does not use radiation.
The MRI of a breast is conducted by placing the patient on her stomach, on a scanning table. The patient's breasts will hang into a hollow in the table, which contains coils which detect magnetic signals. The table is then moved into a tube-like machine that contains a magnet. The first series of picture are then taken, upon which the patient sometimes receives the contrast agent. The contrast agent can be used to improve the visibility of a tumor. The entire session may take about an hour.
A PET (Positron Emission Tomography) scan is a computerized image of chemical changes taking place in human tissue. Patients are given an injection of a combination of sugar and a small amount of radioactive material. This radioactive sugar helps in locating a tumor, because cancer cells absorb sugar faster than other tissues in the body.
After the radioactive substance has been injected, the patients lies still on a table for 45 minutes while she moves through the PET scanner 6 to 7 times. This time period allows the drug to circulate the body, and if a tumor is present the sugar will accumulate in it. PET scans are more accurate in detecting larger and/or aggressive tumors than they are in locating small and/or less aggressive ones.
Electrical Impedance Scanning
Human tissue has different electrical impedance levels (the speed of electricity through material). Breast tissue that is cancerous has a much lower electrical impedance (conducts electricity better) than normal breast tissue. The EIS is done by placing an electrode patch on the patient's arm, and passing a very small current into the body. The current travels through the breasts, where it is measured by the scanning probe, which is placed over the breast. This gives a computerized image of the breasts; tumors show up as bright white spots on the screen.
At this time, mammograms are the most effective tool we have to detect changes in the breast that may be cancer. In women at high risk of breast cancer, researchers are studying the combination of mammograms and ultrasound. Researchers are also exploring positron emission tomography (PET) and other ways to make detailed pictures of breast tissue.
Ductal lavage is an investigational technique for collecting samples of cells from breast ducts for analysis. The physician introduces a salt water solution into a milk duct, through a thin tube which is inserted into the opening of the duct on the surface of the nipple. The doctor then extracts fluids from the duct, which are then checked for indications of cancer.