• Medical diagnostic instruments come in several forms.Medical instruments image by Keith Frith from Fotolia.com
  
  The Merriam-Webster dictionary defines "diagnostic" as pertaining to establishing a diagnosis. Whether you call them diagnostic instruments, tools or equipment, nowadays a whole fleet of instruments exists for medical diagnosis. While the number of tools available is almost as varied as the conditions to diagnose, a few medical diagnostic instruments stand out above the rest.
  
  

MRI

• In the last 30 years, the magnetic resonance imaging instrument, or MRI, has become an important diagnostic tool. With the use of 3D images, doctors view the deepest inner realms of the human body. As a result, minute abnormalities or problems can be quickly spotted and the appropriate treatment determined. Due to its poor reflection of bone density, MRI is especially suited to intracranial or intraspinal images, according to Encyclopedia Britannica.
  
  

Stethoscope

• One of the oldest diagnostic tools still used today, the stethoscope found its humble beginnings around 1816, when Rene Laennec, a physician in France, invented a tool that eventually came to be known as the stethoscope. Even in this technological age, the stethoscope still serves as the go-to instrument for listening to both the lungs and the heart. A common use for this diagnostic tool involves distinguishing between certain lung conditions, including pneumonia, asthma and bronchitis. Skilled physicians using solely the stethoscope can still diagnose heart irregularities and murmurs. It is safe to say this medical diagnostic instrument remains one of the simplest, most common tools routinely used today.
  
  

ECG

• The electrocardiograph has been around since 1903, when Willem Einthoven, a Dutch physiologist, invented what we commonly now refer to as the ECG. The ECG, also known as an EKG, a derivation of its German form "elektrokardiogram," is still used today as a way to study the beats and performance of a patient's heart. The ECG achieves this by recording the electric pulse emitted by the heart as it beats. In this way, doctors gain diagnostic clues to heart attacks and other potentially deadly heart conditions.
  
  

The Internet

• While you should not forgo the consultation and knowledge of a qualified medical practitioner, the Internet has fast become one of the most basic of diagnostic tools. With a few keystrokes, you can enter your symptoms and in seconds have a list of possible causes. As a complementary instrument, the Internet empowers patients to give their doctors detailed information that can assist the professional diagnosis of whatever ails you. The billions of images alone on the Internet can enable concerned patients or caretakers to determine the difference between something requiring urgent medical care, and something likely to clear up with patience or a little over-the-counter treatment. Reputable websites, with expert medical information reviewed and supervised by an independent medical review panel, have been helping consumers understand illnesses since 1996.