There are a number of indirect diagnostic approaches which can be used to detect cancer. The most common of these methods is known as radiology or roentgenography. Radiology refers to photography by means of roentgen rays, which are electromagnetic radiation of extremely short wave length with great penetrating powers in matter opaque to light. X-rays are produced when high energy beams of electrons strike matter. An X-ray photograph is a negative (like a camera film) rather than a positive (like a print).

Here is an example of a routine chest x-ray (Example E1). Abstract what you think is pertinent, and then compare with the suggested abstraction.