Body Positioning in X-Ray Studies
Body Positioning in X-Ray Studies
Body positions in x-ray exams are based on body part, suspected defect or disease, and condition of the patient. The radiographer, also known as the x-ray tech or more formally as the radiologic technologist, uses standardized body positions in performing an x-ray exam. Positions are learned by the radiographer according to body part in relation to body habitus, anatomical position and bisecting planes, and relationship of the body to the x-ray equipment.
Since many body parts overlay other internal structures, the radiographer uses positioning of the body part as well as specific positions of the x-ray equipment to obtain clearer views of the overlapping structures. X-ray exams usually consist of two or more radiographs, taken in orthogonal planes or variations to the relationship of body part and x-ray equipment. Exams require radiographs to be taken at 90 degrees to each other where anatomy is superimposed over important structures, where alignment of fracture ends is questioned, or for localization of foreign bodies. Exams require a minimum of three radiographs when joints or articulations are in the area of interest, although some referring physicians may ask for only two. This allows for evaluation of the bones and well as the joints.
The radiographer applies principles of immobilization in performing the exam. The use of immobilization has two purposes. First, the patient's safety is of primary importance to the radiographer. Second, immobilization assists the patient in maintaining the applied body position during the exam. Some x-ray exams require the patient to suspend breathing during the exposure such as for chest x rays. Suspension of breathing is a method of immobilization that the patient voluntarily performs. In other cases, the radiographer assists the patient in maintaining a position with the use of radiolucent sponges or other positioning aids.
Radiation protection is used to reduce or prohibit x-ray exposure to areas of the body that are biologically sensitive. The determinants of x-ray exposure include time spent under irradiation, distance of x-ray unit, and shielding practices. The most common practice of radiation protection is to protect the reproductive organs, especially in children and young adults. It is standard practice to question women of childbearing age if there is a possibility of pregnancy. Radiographic exams are not usually performed on pregnant women as the developing fetus is biologically sensitive to radiation.
The use of body positioning requires an under-standing of terminology that refers to the relationship of the body to the x-ray equipment and to anatomical references. All body positions and exam requirements are expressed in terms of projection, position, and view. A projection refers to the path the x rays take through the body, from entrance to exit. Position describes the body and its relationship to the x-ray film device (film cassette, image intensifier, image receptor). View is not a positioning term but instead is used in discussion the radiograph. For example, the physician orders an upright chest x ray with two views of an ambulatory patient. The standard positions are P. A. (back to front) and lateral (from the side). The radiographer positions the patient standing at the x-ray image receptor for a posterior-anterior projection (the x rays pass from the patient's back to the front) and a left lateral projection (patient's left side closest to image receptor and x-rays pass from the patient's right to left). Body positioning may also require adjacent areas be addressed (i.e., moving the arms out of the way).
Anatomical position is the fundamental term used in body positioning. In this position, the patient is standing and facing front. The arms are down at the sides and the palms are turned forward so that you can see them. Feet are pointed straight ahead and the toes are lying down on the floor. The surface of the body that is facing front is known as the anterior, or ventral, surface. Any anatomical structure located in the half of the body that is adjacent to the anterior surface is considered to be anterior within the body. The surface of the body facing the rear is the posterior, or dorsal, surface. Any anatomical structure located in the half of the body that is adjacent to the posterior surface is considered to be posterior within the body. The body is also discussed in right and left sides using an imaginary line dividing the sides through the body's center.
Posture and relationship to x-ray equipment
X-ray exams are performed with either stationary or mobile equipment. Stationary equipment may be specialized for upright exams such as a chest x-ray unit or panoramic chair unit. Some stationary equipment only allows for the patient to lie down on a table for the exam. Other stationary equipment has a rotating table that allows for upright exams in addition to having the patient lie on the table. Mobile, or portable, x-ray equipment can accommodate a variety of patient positions. Regardless of the equipment used, the same principles and terminology of positioning are applicable.
Positions for x-ray exams may require description of posture, that is, whether the patient is to be lying down, standing, or seated. The patient's physical condition or ability to cooperate may also affect the positioning procedures used for the exam. If the patient is standing, the body is referred to as upright or erect. The general term for lying down is recumbent. It is necessary to describe the position as face up or face down. Supine position of a patient describes lying on the back and facing up in anatomical position. Prone position describes the patient lying on the abdomen and facing down. For comfort, the patient may turn the head to the side unless the part to be x-rayed is the face, head, or neck. For some exams, the patient is slanted in a head-down position known as Trendelenburg.
Descriptions of the patient's position also varies by the projection. If an oblique projection is required, the body or body part (or the x-ray tube) is rotated 45 degrees from anatomical position. The side and surface closest to the image receptor describe the position. For example, a left anterior oblique describes the patient as having the left, anterior surface of the body closest to the receptor at 45 degrees from anatomical position. Another variation of position is decubitus. In the decubitus position, the patient is lying down and the x rays pass through the patient 90 degrees from the table or bed surface. In a lateral decubitus, the patient is lying on either the right or left side and the x-ray beam passes through the patient from anterior to posterior or posterior to anterior. The position is named for the side that the patient is lying on (i.e., left lateral decubitus describes the patient as lying on their left side). Lateral decubitus positions are used to image the chest or abdomen when it is necessary to demonstrate the presence of an air-fluid interface. In a dorsal decubitus, the patient is supine and the x rays pass through the body from right to left or left to right. This type of position is commonly used in lateral x rays of the spine when the patient cannot be moved into a standard lateral position.
Additional anatomical and movement terms
Additional terms are used to describe relationships of body parts or directions. These terms are often paired describing opposites. Cephalic, or superior, describes a direction toward the head of the body while caudal, or inferior, refers to the feet or away from the head. Proximal describes the source or beginning (i.e., the knee is proximal to the ankle). Distal directs you away from the source or beginning. Medial refers to the middle or toward the center of the body while lateral refers to the outside or away from the center. The surfaces of the hand and foot have special anatomical terms. Plantar refers to the sole of the foot, dorsum to the top or anterior surface of the foot, and palmar to the palm of the hand.
Movements of the joints are also important in body positioning. Flexion refers to decreasing the angle between two parts such as the bending of the elbow. Its opposite movement is extension. The hyper-extended joint is straightened beyond neutral or bent so as to increase the normal angle beyond neutral. In describing flexion and extension of the spine, bending forward is flexion, neutral position is extension, and bending backward is hyperextension. Movement of the arms or legs toward the body's median line is known as adduction while moving them away from the body is abduction. Specialized movements are used to demonstrate stress on a joint. Such movements of the ankle and foot are performed without moving the leg. They are described as eversion, an outward movement, and inversion, an inward movement. Other specialized movements may be described for their effect on adjacent joints or articulations. If the hand is supinated, it is in anatomical position (palm facing up). If pronated, the palm faces down. X-ray exams of the shoulder may require views of both pronation and supination of the hand to completely evaluate structures of the head of the humerous as it articulates in the shoulder joint.
The body habitus describes the basic body shape. Body shape is important in x-ray exams as the size, shape, and position of the organs varies by body type. The technologist should adjust the x-ray unit accordingly, in order to obtain an adequate image. There are four terms used to describe body habitus:
- Hyperstenic (large to massive). Chest and abdomen are broad and deep, lungs are short, diaphragm is high.
- Stenic (average).
- Hypostenic (slender).
- Asthenic (very slender). Chest is narrow, shallow, and long so diaphragm is low.
In the hyperstenic patient, the stomach typically lays across the abdomen at or above waist level. The stomach of a stenic patient is shaped like a comma laying slightly skewed from left to right and centered at the waistline. The stomach of a hypostenic patient is elongated into a "J" shape and may extend into the pelvis. Since the astenic patient appears to have little abdominal space between the diaphragm and pelvis, the stomach is quite long and slender lying primarily in the pelvis. An understanding of body habitus and the relationship of the organs in the chest, abdomen, and pelvis are essential in positioning for upper and lower gastrointestinal exams. In addition, other positioning considerations are important, including posture, respiration, and stomach contents.
Most x-ray exams require little if any preparation by the patient. In many cases, the change from street clothes to a hospital gown is all that is required. Some exams may require the patient to fast for several hours while others may require ingestion of a radiopaque liquid that will define the gastrointestional system in the radiographs. Special imaging procedures such as nuclear medicine, sonography, or magnetic resonance imaging may have additional preparation requirements.
Few x-ray examinations require aftercare. If the examination required an injection of medication or contrast media, instructions will be given about the contrast and care of the puncture site. Following examination of the gastrointestinal system, patients are typically instructed to drink plenty of fluids and are advised how the exam may affect bowel movements.
Complications following x-ray exams are rare. If an injection is required or catheter is used, there may be the typical complications at the puncture site-bruising, bleeding, and discomfort. Patients should be advised of the possibility of complications from their exam, preferably in writing.
Articulation— A joint, a connection between bones.
Orthogonal planes— Intersecting planes, planes at right angles to each other.
Position— A body posture such as upright, recumbent, supine, prone, lateral, also the description of the posture of an anatomical part such as oblique.
Radiograph— X-ray image, either physical (on film or paper) or digital.
Radiographer— Allied health professional who performs diagnostic imaging exams using x-rays, magnetic resonance imaging, computed tomography, sonography, and others.
Health care team roles
Although the radiographer actually performs the examination in most cases, there are other members of the health care team in the radiology department or imaging center. Many facilities have transport personnel whose job it is to move patients in and out of the imaging rooms and department. These individuals are trained in the safe handling of patients and support equipment as well as proper lifting techniques and universal precautions against infections. Many hospitals provide a radiology nurse to perform injections, assist the physician in special procedures, or provide patient care as required. The radiologist will interpret the resulting images.
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American Society of Radiologic Technologists. 15000 Central Ave. SE. Albuquerque, NM 87123-3917. 505-298-4500. 800-444-2778. Fax 505-298-5063. 〈http://www.asrt.org〉.