Saturday, February 13, 2016

Medical Devices (Part 1)

Medical Devices

Some of the devices nominated by our readers are small enough to travel through a blood vessel. Some are so large they fill an entire room. Some cost thousands of dollars but will stay in the body for 10 years, and some cost pennies and are designed to be thrown away after one use. This industry is characterized by innovators looking for the best way to engineer a solution to a problem and device designers are noted for their ability to borrow ideas from other industries.

Hemodialyzers and Dialysis Machines (1800s–1970s)

        These devices provide an artificial replacement for lost kidney function due to renal failure. In hemodialysis, the patient's blood is pumped through the blood compartment of a dialyzer, exposing it to a semipermeable membrane. The cleansed blood is returned via the circuit back to the body. Ultrafiltration occurs causing water and dissolved solutes to move from blood to dialysate and allows the removal of excess fluid.

Artificial Pacemaker (1960s–1970s) 


    The development of the pacemaker arguably gave legitimacy to the discipline of medical device engineering. Its history is linked to famous developers, such as Earl Bakken, Manuel Villafaña, and Wilson Greatbatch. Modern pacemakers have multiple functions. The most basic monitor the heart's native electrical rhythm. When the pacemaker fails to sense a heartbeat within a normal beat-to-beat time, it stimulates the ventricle with a short low-voltage pulse. This activity continues on a beat-by-beat basis.

Magnetic Resonance Imaging (1977) 

The first magnetic resonance (MR) image was published in 1973 and the first study performed on a human took place on July 3, 1977. MR imaging was developed from the study of nuclear magnetic resonance. In its early years, the technique was referred to as nuclear magnetic resonance imaging. The technology is used to visualize the internal structure and function of the body. MR provides contrast between the different soft tissues of the body, making it especially useful in neurological, musculoskeletal, cardiovascular, and oncological imaging. Applications for MR technology continue to evolve. For example, recent applications in functional MRI measure changes in the brain, which could lead to more information about the nature of diseases, such as stroke. They are also being moved into the OR to take images during surgical procedures. 

Computed Tomography Scanner (1972)

 Since its introduction in the 1970s, computed tomography (CT) has become an important tool in medical imaging. It is the gold standard in the diagnosis of a number of different disease entities. CT produces data that are manipulated through a process known as windowing. It demonstrates bodily structures based on their ability to block the x-ray beam. Although historically the images were in the axial or transverse plane, orthogonal to the long axis of the body, modern scanners allow this volume of data to be reformatted in various planes or even as 3-D representations. The first commercially viable CT scanner was invented by Sir Godfrey Hounsfield in Hayes, UK, at EMI Central Research Laboratories. Hounsfield conceived his idea in 1967, and it was publicly announced in 1972. Allan McLeod Cormack of Tufts University in Massachusetts independently invented a similar process, and both Hounsfield and Cormack shared the 1979 Nobel Prize in medicine. The original prototype took 160 parallel readings through 180 angles, each 1˚ apart, with each scan taking about five minutes. The images from these scans took 2.5 hours to be processed by algebraic reconstruction techniques on a large computer.

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