-ogram

The suffix [-(o)gram] evolved from the Greek word [γράμμα] (gr?mma) , meaning "letter". It was used to denote the written record that was maintained about a patient's ailment. When modern devices that could record an examination, such as an electrocardiograph, the suffix [-ogram] was added to the graphic, so we end up with an electrocardiogram. Today we use it to mean "examination of" with the caveat that some type of written, photographic, digital or drawn record must be left behind. Examples of the use of this suffix are:

• Cholangiogram: Examination of a bile vessel
• Angiogram: Examination of a vessel
• Mammogram: Examination of a breast 
• Electrocardiogram: Examination of the electrical activity of the heart. EKG or ECG