Cancer Diagnostic Imaging
How is cancer diagnosed?
There is no single imaging test that can accurately diagnose cancer. The complete
evaluation of a patient usually requires a thorough history and physical examination
along with diagnostic testing. Many tests are needed to determine whether a person
has cancer, or if another condition (such as an infection) is mimicking the symptoms
of cancer. Effective diagnostic testing is used to confirm or eliminate the presence
of disease, monitor the disease process, and plan for and evaluate the effectiveness
of treatment. Tests may be for staging, to determine the extent of cancer and if it has spread, or they may be done to assess
prognosis or select specific therapies. In some cases, it is necessary to repeat testing
when a person’s condition has changed, or if a sample collected was not of good quality,
or an abnormal test result needs to be confirmed. Diagnostic procedures for cancer
may include imaging, laboratory tests (including tests for tumor markers), tumor biopsy,
endoscopic examination, surgery, or genetic testing. Tests are often repeated regularly
throughout treatment to re-stage, that is, to determine the effectiveness of treatment and the cancer's response to
What are the different types of diagnostic imaging?
Imaging is the process of producing valuable pictures of body structures and organs.
It is used to detect tumors and other abnormalities, determine the extent of disease,
and evaluate the effectiveness of treatment. Imaging may also be used when performing
biopsies and other surgical procedures. Listed below are various types of imaging
tests that may be used.
X-rays are diagnostic tests that use invisible electromagnetic energy beams to produce
images of internal tissues, bones, and organs on film. X-rays may be taken of any
part of the body to detect a tumor or cancer.
Computed tomography (CT or CAT scan)
A noninvasive diagnostic imaging procedure that uses a combination of X-rays and computer
technology to produce both horizontal, or axial, images (often called slices) of the
body. A CT scan shows detailed images of any part of the body, including the bones,
muscles, fat, and organs. CT scans are more detailed than general X-rays.
A lymphangiogram is an imaging study that can detect cancer cells or abnormalities
in the lymphatic system and structures. It involves a dye being injected into the
A mammogram is an X-ray examination of the breast. It is used to detect and diagnose
breast disease in women who either have breast problems such as a lump, pain, or nipple
discharge, as well as for women who have no breast complaints. Mammography cannot
prove that an abnormal area is cancerous, but if it raises a significant suspicion
of cancer, a biopsy must be performed to confirm a cancer diagnosis. During a biopsy
procedure, tissue is removed by needle or open surgical biopsy and examined under
a microscope to determine if it is cancer. Mammography has been used for about 30
years, and in the past 15 years technical advancements have greatly improved both
the technique and results. Today, dedicated equipment, used only for breast X-rays,
produces studies that are high in quality but low in radiation dose. Radiation risks
are considered to be negligible.
This diagnostic procedure, without the use of X-rays, uses high-frequency sound waves
and a computer to create images, called sonograms, of blood vessels, tissues, and
organs. Sonograms are used to view internal organs as they function and to assess
blood flow through various vessels. Tumors in the abdomen, liver, and kidneys can
often be seen with an ultrasound. (Ultrasound is not useful in the chest because the
ribs block the sound waves.) Ultrasound can be used through a probe that can be inserted
into organs, such as the anus, vagina, or esophagus and brought closer to the internal
organs, producing a more accurate picture.
Magnetic resonance imaging (MRI)
MRI is a diagnostic procedure that uses a combination of a large magnet, radiofrequencies,
and a computer to produce detailed images of organs and structures within the body.
An MRI is often used to examine the heart, brain, liver, pancreas, male and female
reproductive organs, and other soft tissues. It can assess blood flow, detect tumors
and diagnose many forms of cancer, evaluate infections, and assess injuries to bones
Positron emission tomography (PET)
PET is a specialized radiology procedure used to examine various body tissues to identify
certain conditions. PET may also be used to follow the progress of the treatment of
certain conditions. PET is a type of nuclear medicine procedure. This means that a
tiny amount of a radioactive substance, called a radionuclide (a radiopharmaceutical
or radioactive tracer), is injected into the body during the procedure to assist in
the examination of the tissue under study. A special type of camera can then detect
the radioactivity in the body. Specifically, PET studies evaluate the metabolism (utilization
of tagged glucose molecules) of a particular organ or tissue, so that information
about the physiology (functionality) and anatomy (structure) of the organ or tissue
is evaluated, as well as its biochemical properties. Thus, PET may detect biochemical
changes in an organ or tissue that can identify the onset of a disease process before
anatomical changes related to the disease can be seen with other imaging processes,
such as computed tomography (CT) or magnetic resonance imaging (MRI). More recently,
PET/CT performs PET and CT at the same time and produces a composite image that can
both produce a picture of an organ and measure its utilization of sugar.
Nuclear medicine scan
These scans take pictures after injecting into the body a substance called radionuclides
that release a low level of radiation. Special cameras create pictures of where the
material travels and collects. A tumor may show up as a "hot spot." These scans are
used to detect tumors and bone abnormalities. Some common nuclear scans are bone scan,
PET scan, thyroid scan, MUGA scan, or gallium scan.