Radiology to Detect Lung Cancer

Chest x-ray: Approximately half of all x-rays obtained in hospitals are chest x-rays. It is usually performed to gain an assessment of the lungs, heart and chest wall. A chest x-ray can locate Pneumonia, heart failure, emphysema, and other medical conditions as well as lung cancer.

It is the first test the doctor will order to look for any tumour or spots on the lungs. If it’s normal there is a high probably there is no lung cancer, but if anything suspicious is spotted, the doctor will order further tests.

CT Scanning or Computed Tomography also known as CT or CAT Scan uses unique equipment to obtain multiple cross-sectional images of organs and tissues of the body.

A CAT scan can produce images far more detailed than a conventional chest x-ray and is especially useful for diagnosing tumours. It simultaneously shows many different types of body tissue including the lungs, heart, bones, soft tissues, muscle and blood vessels.

Modern CT scans utilize a method called spiral (or helical) CT which captures images of the chest from many different angles. With the assistance of a computer, it processes the images to create cross-sectional pictures or “slices” of the area causing concern.

The images can then be printed out or examined on a monitor. Sometimes to achieve a better picture, after the first set is taken an intravenous injection of a radio-contrast agent is administered. This helps to outline the structures within the body. A second set of pictures is then taken so they can be examined together.

A CT scan provides the precise information about the size, shape, and position of a tumour, and helps discover any enlarged lymph nodes which could contain cancer which has spread from the lung.

CT scans are much more sensitive than an ordinary routine chest x-ray when looking for early lung cancers, and assist in ensuring patients receive the treatment they need as soon as possible. A CT scan is also useful in looking for tumours in the adrenal glands, brain, and other internal organs usually affected by lung cancer spread.

Magnetic resonance imaging (MRI): MRI scans use radio waves and strong magnets instead of x-rays. The energy released from the radio waves is absorbed and re-released in a pattern shaped by the type of tissue and the disease being investigated.

A very sophisticated computer translates the pattern of radio waves given by tissues and organs into very detailed images of parts of the body. Not only does this produce cross sectional slices of the body like a CT scanner, it can also produce slices parallel with the length of the body.

Positron emission tomography (PET) uses glucose which is a form of sugar containing a radioactive atom. Cancer cells in the body absorb large amounts of this radioactive sugar and a special camera is then able to detect the radioactivity.

A PET scan is a very useful test to discover if someone is suffering from early stage lung cancer and is often used to discover if the cancer has spread to the lymph nodes.

It’s also valuable in ascertaining whether a shadow on a chest x-ray is cancer or not. PET scans are also helpful when a doctor thinks the cancer has spread, but isn’t sure where the spread may be. PET scans can also be used instead of several different x-rays because they scan your whole body.

Bone scans use small amounts of radioactive substance (usually technetium diphosphonate) which is injected into a vein. The amount of radioactivity used is very low and doesn’t cause long-term effects. The radioactive substance builds up in bone areas suspected of having cancer metastasis, (spread).

It’s important to remember other bone diseases can also cause abnormal bone scan results so the results need to be read in conjunction with the results of other tests performed.

Bone scans are usually performed on patients with small cell lung cancer. They are also usually only done in patients with non-small cell lung cancer when other test results or symptoms suggest the cancer has spread to the bones.

Top Image: National Cancer Institute, National Institutes of Health. Lung cancer driven by the Kras oncogene (in purple).

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