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Medical Imaging Technology

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Saved by Andrew P. Miller
on December 5, 2012 at 3:08:10 am

 Medical Imaging Technology   






"The surgical imagination can pleasurably lose itself in devising endless applications of this wonderful process." -NY Times on the discovery of the X-Ray [1] 



Medical imaging has has allowed for the advancement of medical and surgical care for patients during the past century.  William Conrad Rotgen, a German physicist, was the first individual to quantitatively produce a wavelength of radiation that is consistent with the modern day X-ray [9], and helped set in motion the rapid technological advents in medical imaging.  After the ability to harness these radioactive wavelengths was accomplished, it become possible for chemists and physicists to understand the power behind the energy in which they possessed at their fingertips.  The discovery of the X-ray provided a beginning point for future imaging possibilities in medicine which allows healthcare providers to view the internal environment of the human body in a non-invasive manner.  It was not long until it was discovered how large of an impact the possibilities of imagining technologies could have in the field of medicine.  The advent of imaging techniques that displayed a pictorial representation of the internal environment and condition of the human body eventually led to technologies that allow for numerical measures of internal human dynamics, such as electrocardigrams (ECG), blood pressure monitoring, pulse oximetry, and Bispectral Index monitoring (BIS monitor).   



Discovery of X-Rays

Wilhelm Roentgen began his educational career in a manner unbecoming of a dedicated student, but disciplined himself to obtain a degree in mechanical engineering followed by a doctorate one year later [1].  His dedication towards his work led him to the development and discovery of wavelengths of radioactive material that were similar to modern X-rays.  The discovery began with him working meticulously with cathode rays in his laboratory he filled one tube with air, added unknown quantity of gas, and passed an electrical current through it [10].  After ensuring that light could not escape, the electrical current was introduced into the gas filled tube.  To Wilhelm's surprise, he noticed a fluorescent ambiance coming from a cardboard screen when placed close to the apparatus [9].  Wilhelm decided that the results and his theories on this newly discovered wave emission need to be reproduced.  On November 8, 1895, he constructed an apparatus similar to the one he previously used.  The experiment began with him covering the gas filled tube with cardboard and turned down the lights to ensure no light would pass through.  Once the lights were down, the electrical current was applied to the tube, and Wilhelm noticed a flickering light coming from the same screen used earlier coming from across the room [11].  This original screen was painted with a substance named Barium platinocyanide, which was the target for the emission of the invisible rays which Wilhelm had stumbled upon [9].  Wilhelm named these new invisible rays "X-rays" allowing "X" to be denote the unknown nature of these waves [10]. 


The science behind these newly discovered rays quickly began to catch up to their seemingly accidental discovery.  Modern understanding of the X-ray explains that electrons involved in the process of producing X-rays obtain kinetic energy (KE) or "energy possessed by an object by virtue of its motion" [3]. The cathode rays which Wilhelm previously used allowed for these electrons to create a beam that may strike an object, outline it, and possibly absorb into the targeted material.  When the electrons strike the target, their velocity is changed as they pass by a positively charged nucleus, and as a result they emit radiation waves in the form of photons [5].  The scientific term for this process comes from the German word Bremsstrhlung (braking radiation) [12].  These rays of radiation, which are emitted through this process, provided the effects of the X-ray from an atomic view that is invisible to the naked eye.  The study of these processes allowed for science to quantitatively measure the energy needed for these reactions, and the energy that would be emitted from these reactions.  The importance of quantifying these energy expenditures allowed future medical use of X-rays to adapt energy needed for the different tissues of the body, because different body tissues absorb X-rays differently from one another [5].

Development of the First Medical Imaging 


 Wilhelm Conrad Roentgen had discovered rays which possessed the ability to pass through objects and capture images that no one during this time era would have ever imagined possible.  One month after his initially discovery of the fluorescent glow of the Barium plantinocyanide screen, he captured the first X-ray the world had ever seen using his wife as the first photograph [10].  Wilhelm discovered that the X-rays had the ability to capture more than he had even originally believed possible.  Using the same apparatus from his initial experiment, Wilhelm produced an image of the bones of his wife's hand, and the ring that wrapped around her ring finger [1].


"I have seen my death." -Wilhelm's wife after viewing the first X-ray of her hand [9]                                         Early X-ray procedure for the internal imaging of an infant.


This milestone of medical imaging set the stage for future technologies that proceeded.  The first X-ray of Wilhelm's wife's hand attracted the interest of medical professionals during the late 19th and early 20th century.  Wilhelm presented his image to the Wurburg Physical and Medical Society in 1986 which guided the path for the introduction of the X-ray into the world of medicine.  Soon after this publication, aided by these newly developed rays, a doctor in Germany diagnosed sarcoma (malignant tumor of connective tissue [3]) of the tibia of a young boy, and the military implemented X-rays in the location of bullet fragments in soldiers [1].  The quotation from the introductory photograph of this piece denotes the importance of the X-ray  in the world of medicines, for the practice of physicians, and in the outcomes of patient conditions.  X-rays allowed surgeons and physicians to have physical evidence of the internal condition of the human body without needing to unnecessarily open the body to view the internal condition.  These implications also provided useful in the medical training programs across the world.  The first training programs for medicine relied on the ancient teachings of Hippocrates, based solely on what one man believed to be true of the human body.  This was the basis for teaching anatomy to medical students until a law was passed in 1831 that provided medical schools with cadavers for the use of teaching [14].  The birth of X-ray technology provided an even greater means of teaching anatomy in a non-invasive manner.


The impact that X-rays have had on medical imaging is extensive, and has allowed for better patient outcomes and quicker, safer diagnostic measures.  Early cathode rays were replaced with large machines that used the same basic principles that the early gas-filled tubes used during the discovery of the unknown, invisible rays.  Dense tissues such as bones, teeth, and tumors provided great targets for absorption from electrons, and provide the emission of radiation based on the Bremsstrhlung Principle [12].  The ability to create images of hollow organs was developed through the use of basic ideas presented by Wilhelm Roentgen.  Scientists and physicians adopted Wilhelm's theories by introducing a radiopaque substance, such as Barium sulfate, which would absorb the X-ray emission [7].  This Barium based material allows for an easy route of entry into the subject's body, and essentially acts as a magnet for the X-rays subjected to the target area.  Modern use of Barium sulfate is similar to the Barium platinocyanide used on the cardboard screen that led to the discovery of the invisible rays that Wilhelm had once described.  

Additional Imaging Technologies



-CT Scan showing a left hemisphere ischemic stroke.                       -The second oldest method of imaging, the Ultrasound (US), showing fetal detail in utero.



After the discovery of X-rays, and the ability to harness the potential of the kinetic energy produced by the electron beams, newer technologies continued to arise. Computerized Tomography (CT) scans took X-ray imaging to the next step in medical imaging.  The first application of the CT scan, introduced in 1972, exposed the subject to low emission intensity from an X-ray located on one side of the subject, and passed through the targeted area to a detector on the opposite side of the subject [7].  The X-ray tube emits the electron beam, and produces the radiation necessary for adequate imaging.  On the opposite side of the X-ray tube the detectors provide an area of absorption for the rays, and provide the source which attracts the electrons.  As the X-ray detectors rotate around the targeted area, the subject is moved insidiously through the tube creating three-dimensional slices of the targeted area [6].  This improvement provides a sequences of images of internal tissues and structures from multiple angles as opposed to the previously superior, single-angled, stationary X-ray.  






[1] Assmus, A. Early History of X Rays. Beamline, 1995.

[2] Beckmann, E.C. CT scanning in the early days. The British Journal of Radiology, (79), 2006.

[3] Mosby’s Dictionary of Medicine, Nursing, & Health Professions(8th ed.). (2009). St. Louis, MO: Mosby’s, Inc.

[4] Niederer, P.F. Basic elements of nuclear magnetic resonance for use in medical diagnostics: Magnetic Resonances Imaging (MRI) and Magnetic Resonance Spectroscopy (MRS). Technology and   Health Care. (19). 2011.

[5] Niederer, P. F. Diagnostic Medical Imaging: X-Ray projection technique, image subtraction method, direct digital x-ray imaging, computed tomography (CT). Technology and Health Care. (17), 2009

[6] Purves, D., Augustine, G.J., Fitzpatrick, D., Hall, W.C., LaMantia, A., McNamara, J.O., & White, L.E. Neuroscience Fourth Ed. Sunderland, Mass: Sinauer Associations, 2008

[7] Saldin, K.S. Human Anatomy Second Ed. New York, NY: McGraw-Hill, 2008

[8] Zollman, D., McBride, D., Murphy, S., Aryal, B., & Kalita, S. Teaching About the Physics of Medical Imaging. International Conference of Physics Education, 2009.

[9] "Wilhelm Rontgen" Wikipedia, The Free Encyclopedia. 29, November 2012, 17:52 UTC. Wikimedia Foundation, Inc. 2012. <http://en.wikipedia.org/wiki/Wilhelm_R%C3%B6ntgen>

[10] NDT The Discovery of X-Rays. <http://www.ndt-ed.org/EducationResources/HighSchool/Radiography/discoveryxrays.htm>

[11] Frame, P.W. Tales from the Atomic Age. Health Physics Society Newsletter. <http://www.orau.org/ptp/articlesstories/invisiblelight.htm>

[12] Britannica Encyclopedia (2012). <http://www.britannica.com/EBchecked/topic/78784/bremsstrahlung>

[13] Filler, A.G. "The History, Development, and Impact of Computed Imaging in Neurological Diagnosis and Neurosurgery: CT, MRI, and DTI." Internet Scientific Publications. <http://www.ispub.com/journal/the-internet-journal-of-neurosurgery/volume-7-number-1/the-history-development-and-impact-of-computed-imaging-in-neurological-diagnosis-and-neurosurgery-ct-mri-and-dti.html#sthash.jAsbuSM4.pl2KL6DO.dpbs> 

[14] Perry, J.L., & Kuehn, D.P. "Using Cadavers for Teaching Anatomy of the Speech and Hearing Mechanisms."ASHA (2006)


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