Body Positioning in X-Ray Stu... Health Article

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 hyperextended 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.