The Lumbar Spine and Radiology - Essay Example

The Lumbar Spine and Radiology June 22, The lumbar spine is the long part of the spinal column which allows the human body to bear weight as well as absorbing shocks (Bogduk, 2005, p. 5). This column is known as the vertebra, or vertebral body (Bogduk, 2005, p. 2). The vertebral body is made up of 24 vertebrae, which in turn are made up of cortical bone, pedicles, and laminae. The rest of the vertebral body consists of intervertebral discs, facet joints, and the ligamentum flavum (Bogduk, 2005, p. 5-10). Due to the amount of heavy lifting humans do on a regular basis, it is not uncommon for people to report back pain at least once in their life (Herkowitz & Bell, 2004, p. 4). Despite its ability to hold weight and absorb shocks, the lumbar spine is vulnerable and can easily be damaged in a number of ways. Therefore, it has become necessary to find an adequate means of measuring a patient’s pain. X-ray imaging is based in part on high energy photons passing through a phosphor screen and then scattering around the object being x-rayed, thus producing an image. The other part is a matter of studying the data collected from the original screening (Iniewski, 2009, p. 3). Most x-rays are made up of geometric magnification, which is created by crystals which are responsible for diffracting the image (Chang, 2004, p. 31) Before x-rays were available, the only way for a doctor to measure what it is they are looking at is by asking the patient and making judgments by the pain that they report (Herkowitz & Bell, 2004, p. 3). X-rays are not only necessary when it comes to diagnosing what the injury is, but they must also be performed again before surgery, to make certain that nothing has changed since the last time (Herkowitz & Bell, 2004, p. 459). The image quality of an x-ray plays a large role in how the image will turn out. The goal is to obtain optimal image, which provides the doctor and patient with an adequate view of all features related to the x-ray (McQuillen-Martensen, 2006, p. 1). Some key factors which play a role in image quality are: anatomical positioning, kVp and mA, density and contrast, SID, sharpness as well as focal point and geometry. It is important that the patient be properly set out on the observation table before hand. The patient should be lying face up on the table. The shoulders and “anterior superior iliac spines (ASISs) at equal distance from the imaging table prevent rotation” (McQuillen-Martensen, 2006, p. 414). The x-ray machine can only focus on the certain views. One such view is anterior to posterior (AP), which refers to the side of the body the x-ray is projected from – front to back. AP specifically focuses on the psoas muscles, which can be found lateral to the Lumbar spine (McQuillen-Martensen, p. 414). This form of view is often used when looking for scoliosis or fractures, and is preferable to posterior to anterior (PA). This is because PA could lead to scarring and burns from excess radiation, as well as “the stripping of the paraspinal musculature, which can be associated with a prolonged recovery and post operative pain and disability” (Herkowitz & Bell, 2004, p. 226). The source-image receptor distance (SID) is the “distance from the anode’s focal spot to the IR” (McQuillen-Martensen, 2006, p. 3). When it comes to any view, the SID should be between 40 and 48 inches. The kilovolt peak (kVp) is the maximum amount of energy to pass through the radiation tube. When it comes to AP projection of the Lumbar spine, the kVp is 75-80 (McQuillen-Martensen, 2006, p. 413), which is relatively low. Contrast being the “number of shades of gray that represent the different structures on the image” and density being “the degree of darkness of an image” (McQuillen-Martensen, 2006, p. 4), each play key factors in portraying the bone as well as soft tissue structures within the lumbar. If the kVp were to go beyond 80, it could cause the contrast and density to be blurred, and if it were to be below 75, it could cause the sharpness of the image, or amount of detain available in the image, to decrease. The mA is the measurement of amperage used in exposure. The mA is decided based on the thickness of the patient’s lumbar (McQuillen-Martensen, 21006, p. 414). When this number is multiplied by the amount of time a patient is subjected to the x-ray, the result is the milliampere seconds (mAS). The mAS relates to how grainy an image is. If the number is insufficient, the image will result in a quantum mottle (McQuillen-Martensen, 2006, p. 4). This, in turn, affects density and contrast, and it is important to include all of these things when calculating the beam measurements. The Lateral view of the lumbar is often used for checking spondylolisthesis. Here spot views are often performed because they give a more definite shape. Lateral is also responsible for viewing flexion and extension (Kuri & Stapleton, 2002, p. 135). According to Kathy McQuillen-Martensen, the kVp of Lateral projection should be no less than 85 and no more than 95. Last is the Oblique view. Oblique views are often used on parts of the body that cannot be accurately shot through lateral or AP. They are often used on the Lumbar in the case of spondolylisis, however oblique views do have a high amount of radiation. According to Kuri and Stapleton (2002), this view allows “a good delineation of the contours of the pars interarticularis (p. 136). The kVp used in oblique view should be between 75-85 (McQuillen-Martensen, 2006, p. 413). When it comes to focal spot, there are two main options. The first is small focal spot, and it is usually associated with a low mA as well as low heat. While the small focal spot does allow for a more fine-tuned image, it can sometimes be affected by the movement of the patient. Therefore it is usually recommended the technician use a large focal spot when it comes to phantom images (Wilson, 2000, p. 12). This large focal spot is often used on a station with at least 200 mA’s (Marchiori, 1999, p. 9). Part of the reason that the geometry of image formation in regards to the lumbar spine is so difficult is because it is more complicated than most bone structures which a radiologist will x-ray. The geometry of image formation has to do with the geometry of the beam before and after it passes through the patient (Eskay-Auerbach, 1972, p. 46). This all depends on which part of the lumbar the beam is being shot through. Different geometry of the beam is necessary going through the disc compared to the cortical bone. The trouble with the geometry of image formation when it comes to the lumbar spine is flexion. Flexion is the process of bending compared to extension, or standing straight. When the body, specifically the lumbar spine, is in flexion, it alters how much exposure one receives from the beam (Bogduk, 2005, p. 178). Occasionally this can be useful because is allows for further studying of motion within a particular segment (Eskay-Auerbach, 1972, p. 46). Part of the problem comes from the high amount of sensitivity that the lumbar nerve is subjected to when it is injured. Because of this, radiologists do not want to expose the nerves to any unnecessary radiation. Since the lumbar spine is a large body part, it is usually subjected to a large amount of radiation in order to submit the best picture for processing. Simple x-rays only allow for 2D projection, which makes things difficult, especially since there are many angles of which the lumbar spine must be studied at to determine what is causing the patient pain. It is also important to take into account that various parts of the body which receive more or less amounts of radiation, depending on what they can handle. For instance, bones such as the vertebrae in the lumbar spine are subjected to higher amounts of radiation than organs or such. However, part of the vertebral body is made up of a gel-like fluid, which could be affected by heavy radiation were it exposed for long periods of time. Of course, most radiologists know how to handle the amount of radiation being subjected to a patient. Before patients undergo x-rays, there are objects of similar size and shape put through the x-rays to see how much each can take. And with current technology it is possible to scientifically generate how much radiation can be applied to persons of certain weight and height (Eskay-Auerbach, 1972, p. 46). For instance, if the x-ray is conducted PA rather than AP, someone with a smaller body weight would be more likely to be subjected to high radiation due to a lack of tissue and body fat (Bonnick, 2010, p. 337). This may not happen as often as it once did now that technicians know more about how radiation works, but it is still a possibility. Therefore certain precautions are taken when taking patients to x-rays, for instance factoring in one’s body weight as well as their build. It is also important to look at pregnancy. Were a pregnant woman to be exposed to x-rays during the early stages, it may be suggested that she terminate the pregnancy (International Commission on Radiological Protection, 1991, p. xiv). In this case it is important that the patient and fetus should undergo evaluation by a physician who is qualified. It is also necessary to consider scatter radiation management. Scatter radiation is when the radiation from the photons aimed at the patient are disrupted by various objects which in turn affect how the image with be. The amount of scattered radiation is based on a number of things. For instance, if the examination table was made of heavy materials, it would increase the scattered radiation. For this reason tables are made of wood or graphite. Also, the Compton Effect has a lot to do with how much scatter radiation the patient is subjected to (Barbaric, 1994, p. 6). This is because “the Compton Effect is a process in which the incoming photon interacts with any of the orbital electrons that can be considered virtually free, as long as the energy of the gamma is much larger than the binding energy” (Paic, 1988, p. 8). This is to say that photons from the patient are interacting with the photons from the beam, causing the image to be distorted, or foggy. Since the Lumbar Spine is thick, it will require a high tube of radiation, which in other cases could present high amounts of scatter. However, there are grids which have been created that monitor the amount of scatter received from high tubes. Therefore the Lumbar Spine, which would have created a massive amount of scatter radiation, is now capable of being imaged without much difficulty (Hayat, 2008, p. 55). Therefore it is easy to see that steps are being taken to reduce scatter radiation, which in turn allows for a more adequate image. With more adequate imaging, there will be less need for x-rays. Were the Lumbar Spine to be damaged due to radiation from an x-ray, that patient could face never walking again. Therefore it is necessary for doctors and nurses to look into x-ray principles and how they may affect each patient they have before submitting said patient to an x-ray. Outline A. Introduction B. What is the Lumbar Spine 1. Why x-rays are necessary C. How Focal Spot Selection Applies to the Lumbar Spine 1. A look at mA and kVp D. Geometry of Image Formation and the Lumbar Spine E. Scatter Radiation Management 2. What is scatter and how it can be managed F. Radiation Safety and Dangers G. Conclusion Citation Barbaric, Z. L. (1994). Principles of Genitourinary Radiology. New York, NY: Thieme Medical Publishers. Bogduk, N. (2005). Clinical Anatomy of the Lumbar Spine and Sacrum. London, England: Elsevier, Limited. Bonnick, S. L. (2010). Bone Densitometry in Clinical Practices: Application and Interpretation. Denton, TX: Humana Press Chang, C. L. (2004). X-Ray Multiple Wave Diffraction: Theory and Application. Berlin, Germany: Springer-Verlag Berlin Heidelberg. Eskay-Auerbach, M. (1972). Medical-Legal Aspects of the Spine. Tuscon, AZ: Lawyers & Judges Publishing. Hayat, M. A. (2008). Cancer Imaging: Lung and Breast Carcinomas. London, England: Elsevier Academic Press. Herkowitz, H. N., and Bell, G. R. (2005). The Lumbar Spine. Philadelphia, PA: Lippincott Williams & Wilkins. Iniewski, K. (2009). Medical Imaging: Principles, Detectors, and Electronics. Hoboken, NJ: John Wiley & Sons, Inc. International Commission on Radiological Protection (1991). Radiological Protection in Biomedical Research. Annals of the ICRP 2(3), xiv. Kuri, J., & Stapleton, E. (2002). The Spine At Trial: Practical Medicolegal Concepts About the Spine. Chicago, Illinois: American Bar Association. Marchiori, D. M. (1999). Clinical Imagining: With Skeletal, Chest, and Abdominal Pattern Differentials. Davenport, IA: C.V. Mosby. McQuillen-Martensen, K (2006). Radiographic Image Analysis. St. Louise, MI: Elsevier Saunders. Paic, G. (1988). Ionizing Radiation: Protecting and Dosimetry. 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