Imaging Studies to Diagnose Ovarian Cancer
A variety of imaging techniques may be performed to determine the size, shape, location, and consistency of the ovaries.
Ultrasound, an imaging method based on the principle that solids reflect sound waves in a manner that can be converted into a picture, is a valuable tool for the diagnosis of ovarian cancer. During ultrasound, a transducer probe releases high-frequency sound waves that bounce off the ovaries, are collected, and are transmitted onto a video screen to create a picture called a sonogram.
When the probe is placed on top of the abdominal wall, the process is known as transabdominal ultrasonography. When the probe is placed within the vagina, the process is known as transvaginal ultrasonography or transvaginal sonography (TVS).
The transvaginal method allows the probe to be placed closer to the ovaries, which improves the quality and resolution of the sonogram. Therefore, many experts prefer TVS as an imaging method for ovarian abnormalities; however, TVS does not distinguish cancerous masses from those caused by benign disease. The diagnostic potential of transvaginal sonography is improved when paired with the blood test known as CA125.
In addition to TVS, other imaging methods may be employed to visualize the ovaries. It is important to note that these methods alone do not guarantee an accurate diagnosis. Therefore, they usually are performed along with other tests such as needle aspiration cytology or CA125.
Computed tomography (CT or CAT scan) is an imaging technique in which an x-ray rotates around the body and takes pictures (scans) at numerous angles. Sometimes a special dye known as contrast medium is injected or consumed to highlight body parts during CT scanning (if ovarian cancer is suspected, contrast medium may be used to highlight the intestines and emphasize any spread of cancer within the pelvic cavity). A computer puts the scans together and creates detailed images of the body's organs in cross-section.
Magnetic resonance imaging (MRI scan) is another computer-assisted imaging method. It uses a powerful electromagnet to align water molecules within the body and create an internal picture.
Transvaginal color flow doppler is an ultrasound test that measures blood flow to the ovaries. As with TVS, a high-frequency probe is placed within the vagina. Blood measurements are displayed as graphs showing the resistance index (holding back of blood flow) and pulsatile index (speed of blood flow).
In women with healthy ovaries or noncancerous disease (e.g., ovarian cyst), the ovaries are nourished by normal blood vessels. If an ovarian cancer is present, the tumor requires many new blood vessels for adequate circulation. Such new blood vessels offer little resistance to blood flow. Therefore, low resistance and pulsatile indexes suggest the presence of a cancerous tumor.