X-ray and CT Scans - Essay Example

?DOES CT REPLACE X-RAY AND IF SO FOR WHAT? X-ray and CT scan make available the view of the internal organs and help in the correct diagnosis without having to perform intrusive surgery. The CT scan is comparatively new and recent development that makes use the same technology as X-ray but can be used to reconstruct better 2-dimentional and 3-dimentional images. This is done by means of computers with dedicated imaging equipment. One of the major problem or disadvantage with respect to both X-ray and CT imaging technology is the fact that these techniques use ionizing radiation. Because ionizing radiation can cause tissue damage in a longer run, there is a limit on the total radiation dose per year to which a patient can be subjected. Radiation dose is of particular concern especially in the paediatric and obstetric radiology. This paper discusses in detail the possibilities of replacing X-ray with CT scans for specific proposes. DOES CT REPLACE X-RAY AND IF SO FOR WHAT? INTRODUCTION Medical imaging techniques have under gone several changes over the year. X-rays and CT scans are among the most common imaging techniques used in the medical field to study various disorders in the body. Both the technique involves the use of ionizing radiation and has health concerns especially in paediatric and obstetrics field of medicine. The accidental discovery of X-Rays in 1895 by Wilhelm Conrad Rontgen contributed to the imaging techniques especially in the medical field 1. X-rays have short wavelength, on the order of degree of cells, and their elevated energy they can break through the human body. This paper compares the use of planar X-ray with that of the CT scans and also discusses the possibilities of replacing the traditional X-ray with CT scans for specific purposes. Traditional X-ray X-ray is an imaging technique that is based on transmission of X-rays from a source that passes through the patient and is detected either by film or an ionization compartment on the opposite side of the body. Differential dwindling of X-rays that passes through the body create the contrast in the image between different tissues. For instance, X-ray dwindling is predominantly efficient in bone, when compared to soft tissues. In planar X-ray radiography, the image in the x-ray film is just the 2-dimensional projection of the tissues that is between the X-ray source and the film (see figure 1). As a result, the image formed does not present clarity in different tissues and a proper distinction. Planar X-ray radiography aids in several procedures such as intravenous pyelography (IVP) to spot diseases of the GU tract as well as aid in identifying kidney stones 2. The use of X-ray in abdominal radiography helps in the study of any disorders in liver, bladder, abdomen, and pelvis. It is also helpful in chest radiography for identifying the diseases of the lung or any fractures in ribs. X-ray fluoroscopy is another technique used to identify a number of different GU and GI diseases 2. One of the major disadvantages with planar X-ray radiography is the overlapping layers of soft tissue or composite bone structures can a lot be complicated to understand, even for an expert radiologist. In order to overcome these problems the X-ray computed tomography (CT) came into existence. X-ray Computed Tomography Godfrey Hounsfield in the year 1972 invented X-ray computed tomography, for which he, jointly with Allan Cormack, who had independently done earlier work on the mathematics of the system, were awarded together the Nobel Prize in Medicine in 1979 2. This technique overcomes the disadvantage of planar X-ray by enabling the acquisition of 2-dimensional X-ray images of thin “cross segments/slices” through the body. Multiple images from adjacent segments can be obtained in order to restructure it into a 3-dimensional volume. The X-ray supply is compactly collimated to interrogate a thin “cross segments/slices” through the patient. The X-ray source and detectors go around simultaneously around the patient, producing a sequence of 1-dimensional projections at a number of diverse angles. Later these data are rebuilt to provide a 2-dimensional image and by taking multiple slices can also provide a 3-dimentional image. CT images when compared to planar X-rays have an exceptionally high spatial resolution (~1 mm) and present realistic distinguish between soft tissues 2. Over and above anatomical imaging, CT is the imaging technique that can create the highest resolution angiographic images, specifically, images that can give an idea about blood flow in vessels. Of late there are further developments that have improved the CT imaging. For instance, in spiral and multi-slice CT it is possible to get full 3-dimensional images in a single patient breath-hold. CT images show realistic dissimilarity among soft tissues such as kidney, liver, and muscle since the X-rays passed through each organ are no longer superimposed one above the other at the detector, which is true in the case of planar X-ray radiography 2. The fundamental principle after CT is that the 2-dimensional internal structure of an organ can be reconstructed from a series of 1-dimensional projections of the object acquired at diverse angles. With the purpose of obtaining an image from a thin slice of tissue, the X-ray beam is collimated to pass out a thin beam (see figure 2 & 3). These X-rays passes through the body in a thin slice and the detectors that are positioned opposite the X-ray source, record the total number of X-rays that are passed through the patient. This result in a 1-dimensional projection and the signal intensities in this projection are dictated by the 2-dimensional allocation of tissue attenuation coefficients within the slice. Further, in order to get clearer picture, the X-ray source and the detectors are continuously rotated in different angle and the measurements repeated. The radiologist continues until adequate data have been collected to rebuild an image with high spatial resolution. Cerebral Scans CT scans are made use in a wide range of medical settings. One of the most significant functions of CT is in cases of head trauma. With the use of CT it is today possible to examine skull fractures caused due to some accidents and associated brain injures, or hemorrhages. It becomes easy for a radiologist to identify hemorrhages as it shows up on CT scans as regions of amplified signal intensity. This is because of the higher attenuation from the high levels of protein in hemoglobin. On the other hand in case of Edema, that is common in the patients with stroke, CT images shows up as a region of reduced signal intensity. CT is also a most preferred option in the case of identifying brain tumors. The calcification in lesions such as meningiomas or gliomas, can be easily identified in the CT images. Finally, CT images can also be used to examine changes in bone structure and volume in diseases of the sinus. In case of planar X-rays, these applications are not possible and hence CT scans are a preferred option in the medical field 2. Pulmonary Disease CT scans are a major option in identifying several lung related diseases such as cancers. CT scores better in identification of pulmonary disease because lung imaging is extremely complicated using ultrasound and magnetic resonance imaging (MRI). Today with the advancement of CT technology it can identify pulmonary malignancies and emboli, and is over and over again used to detect the degree of spread of diseases of the lung such as silicosis, fibrosis, and emphysema. Additionally it is also possible to identify Cystic fibrosis at an early stage and treat it 2. Abdominal Imaging CT is furthermore extremely helpful in the recognition of abdominal tumors and ulcerations particularly in the liver. It is also possible to identify infectious pathologies such as hepatic hemangiomas. It is mainly done using a series of images after injection of the iodinated contrast agent and the scans soon after the injection show hemangioma increases in signal intensity, but within half an hour there is uniform augmentation of the whole tumor. It is also possible to identify multiple fractures in elderly patients due to osteoporosis or any other conditions 2. Cardiac Imaging With the help of multi-slice CT, it is possible to identify the blocks in the arteries. CT angiography avoids the invasive placing of a catheter. This is time efficient and also helps in cases of emergencies 3. Advantages and Disadvantages of CT There are a number of advantages that CT has over traditional X-rays. For instance, it is possible to eliminate the superimposition of images of structures that need not be studied. Besides because of the inbuilt high-contrast resolution of CT, it is possible to distinguish between tissues that differ in physical density even by less than 1%. As a result it can help in identifying damaged cells of cancerous cells in a tissue more clearly. Further, multiplanar reformatted imaging can be obtained using either multiple contiguous or one helical scan. CT Colonography is increasingly gaining popularity especially in UK and may be as useful as a barium enema for detection of tumors and bowel cancers. However, the dose of radiation can be reduced to a greater extend 4. However, contrasting traditional X-ray equipment which are rather straightforward and small, CT scan apparatus are to a great extent advanced and significantly more multifaceted since the scanner needs to spin around the patient being scanned. As a result, CT Scan equipment costs much more than X-ray equipment and is much more expensive for the patient. CT Scan also exposes the patient to greater risks of radiation when compared to X-ray. It is a proven fact that several rounds of CT scan or X-rays can be dangerous in a longer term. Hence it is very important to undergo X-ray or a CT scan under the advice of a doctor. Even though the risks and expenditure of getting a CT scan is greater than an X-ray, today it has gained popularity among the medical staff as well as the patients as it can present a lot more information in a short span of time and provide a better chance of a correct diagnosis 5. Traditional X-rays also continues to be used and is good enough to identify bone fractures and deformities. Finally, it can be said that both CT scans and X-rays need to be used for specific purposes and only if necessary as both the techniques involve harmful radiations. References 1. X-rays and CT scans. Web site. Available at: http://wings.buffalo.edu/eng/mae/courses/417-517/Orthopaedic%20Biomechanics/Lecture%206.pdf Accessed March 21, 2012. 2. X-Ray Imaging and Computed Tomography. Web site. Available at: http://media.wiley.com/product_data/excerpt/63/04712376/0471237663.pdf Accessed March 22, 2012. 3. Sun, Z. Multislice CT angiography in cardiac imaging: prospective ECG-gating or retrospective ECG-gating? Biomedical Imaging and Intervention Journal. Web site. Available at: http://www.biij.org/2010/1/e4 Accessed March 22, 2012. 4. Brian R. Subach et. al. Reliability and accuracy of fine-cut computed tomography scans to determine the status of anterior interbody fusions with metallic cages. Virginia Spine Institute. Web site. Available at: http://www.spinemd.com/publications/articles/reliability-and-accuracy-of-fine-cut-computed-tomography-scans-to-determine-the-status-of-anterior-interbody-usions-with-metallic-cages Accessed March 22, 2012. 5. Difference Between X-Ray and CT-Scan. Web site. Available at: http://www.differencebetween.net/technology/difference-between-x-ray-and-ct-scan/ Accessed March 22, 2012. Appendices Figure 1: The basic setup for X-ray imaging Figure 2: The principle of computed tomography with an X-ray source and detector unit rotating synchronously around the patient Figure 3: The principle of computed tomography Read More