Overview: Traditional Diagnostics 

Many of the signs and symptoms associated with cancer are not unique to cancer, and can indicate many other illnesses or diseases. To get an accurate diagnosis your doctor may order a number of tests to better understand your health. Your doctor can use them in any combination and some are better suited for certain parts of the body or specific cancer types. Cancer treatments are most successful when cancer is caught early, and so ensuring you have an accurate and swift diagnosis is the first line of defense in cancer treatment.

While newer more advanced diagnostic tools exist they are more expensive than standard diagnostic tools, because of this they are rarely the first tests used for diagnosis. In the next unit, we’ll discuss the latest advances in diagnostics, but before we do it's important to understand traditional diagnostic tools and how they work, as well as their benefits and limitations.   

Lab tests, including blood and urine, help your doctors understand your overall health. They provide information on how well your organs are functioning, and are also able to give information about certain types of cancer including blood cancer. 

Imaging tests give specific information about the parts of the body they are focused on. Unlike lab tests, which give an overall picture of your health, imaging tests show the location of tumors, their size, and if they have spread to nearby tissues.

Patient being prepped for MRI. Source: National Cancer Institute.

Traditional imaging tests include:

• Ultrasound use high-frequency sound waves that move through your body to create images called sonograms
•  X-rays use a type of high energy ionizing radiation to create images on film
• CT or CAT scans (Computed tomography or computerized axial tomography) use ionizing radiation to make computer generated detailed pictures of the inside of your body
• MRI scans (magnetic resonance imaging) uses radio waves and strong magnets instead of x-rays to make detailed pictures of the inside of your body
• Endoscopy is a thin lighted tube-like device with a camera that looks inside your body providing a video image
• Biopsies remove a small sample of tissue to check for cancerous cells
  

Both CT scans and x-rays use a beam of radiation to distinguish tissue density.  These tests project a beam of energy through your body, this energy passes through in varying degrees depending on the density of your tissues. The energy that passes through is then picked up by a collector on the opposite side and translated into an image. Tissues that are more dense absorb more of this radiation, and less dense tissues allow more to pass through, this difference creates the image. For example, a dense mass on a liver would absorb more radiation than the surrounding tissue and the detector/collector will convert this difference into an image. MRIs use the same principle but instead of radiation they use radio waves which interact with the amount of water in a tissue.