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Issues of Concern

Understanding patient positioning requires a knowledge of the basic terminology relating to radiographic positioning:

Movement: Describing the movement of joints concerning standard positions helps us communicate and describe a patient’s orientation. Flexion corresponds to a decrease in the joint angle, while extension describes an increase in the joint angle. Abduction refers to the movement of a limb away from the midline, while adduction corresponds to the limb’s movement towards the midline. Pronation corresponds to the movement of the hand and forearm that brings the palm and hand facing posteriorly. Supination corresponds to the movement of the hand or forearm to bring the palm facing anteriorly. Eversion in the context of the foot describes the movement of the sole away from the median plane, while inversion refers to the movement of the sole towards the median plane.

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Projections: X-rays travel in a straight line with beams diverging from a source. The initial structures a beam hits are magnified concerning those closest to the detector. Therefore, structures that need to be measured with better accuracy must be placed closer to the detector. The central ray is a simplified way of indicating the direction in which an X-ray beam travels. Different projections describe how the central ray travels through anatomy. Anterior-posterior denotes that the central ray passes through the anterior anatomy and exits posteriorly, while the posterior-anterior denotes that the central beam passes from posterior to anterior. These terms also indicate which structures are closer to the detector. In anterior-to-posterior (AP) radiographs, the posterior structures are closer to the detector, and in posterior-to-anterior (PA) images, the anterior structures are closer to the detector. Therefore, as an example, chest radiographs generally obtain PA to minimize magnification of the cardiac silhouette. This isn’t possible for portable chest radiographs, which are by necessity obtained as AP, resulting in a magnification of the cardiac structures. Lateral indicates a trajectory of the central ray passing from 1 side of the body to the other. An oblique projection corresponds to a central ray trajectory through a plane angled to the transverse or coronal plane. An axial projection corresponds to a central ray that passes through the body’s long axis.

Positioning: Several dozen standard radiographic exams, including chest radiographs and evaluation of the shoulder and knee joints, are considered the most commonly requested studies. Below are some commonly ordered radiographic exams and highlighted instructions regarding patient positioning.

Chest: Patients are positioned for chest radiographs with an erect posture of the chest and a slightly extended chin. The hands are placed on the hips, palms facing out, and shoulders are rolled forward. The central ray is centered on the center of the lung fields, and it is important to ensure no thorax rotation on frontal radiograph acquisition. As mentioned above, chest radiographs are obtained in the PA position with the front of the chest against the detector to minimize the magnification of the cardiac silhouette. The lateral chest radiograph requires the left side to be positioned against the image receptor, thereby minimizing cardiac magnification. The arms are raised and crossed above the head. The chin is extended, and the thorax is without rotation or tilt. The thorax is centered on the central ray and the image receptor anteriorly and posteriorly. For a lateral decubitus chest radiograph, the patient lays on the side (either right or left) with the arms above the head and the chin up. The central ray is centered at the level of the T7 vertebra. Positioning for oblique radiographs requires rotation at approximately 45 degrees.

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Upper Airways: For upper airway radiographs evaluating the trachea and the larynx, the patient stands erect in a seated or standing position. The chin is raised slightly, the arms are down, and the shoulders are depressed. Ensuring no rotation and that the sternoclavicular joints have a symmetric appearance is important for the AP position. On the lateral view, the field of view can be adjusted based on the area of interest.

Hand: When acquiring hand radiographs, the patient is typically seated at the end of the table with the elbow in flexion. The technologist should align the long axis of the hand, generally parallel to the image receptor. The hand should be in pronation with the digits slightly separated. There should be a hand rotation of approximately 45 degrees for an oblique view of the hand. This is ideally performed with a support apparatus to have the hand rested on, with the digits slightly separated. The lateral hand radiograph requires the digits to be separated and spread into a fan-like position, ideally supported by a radiolucent step block. The Norgaard or “Ball-catchers” view requires the hand’s medial (ulnar) aspect to be closely approximated with the palms up and the hands obliqued 45 degrees. This view is commonly employed when evaluating for rheumatoid arthritis.

Wrist: The patient is seated with the arm on the table. The wrist is parallel to the surface of the image receptor without rotation. The hand is pronated with the fingers flexed. The wrist should be in direct contact with the surface of the image receptor. On the lateral view, image acquisition of the wrist, the humerus, and the forearm (and the wrist) should be maintained on the same horizontal plane. The wrist is parallel to the surface of the image receptor and is positioned in a true lateral position. The oblique view is obtained with the wrist rotated 45 degrees so that the wrist’s ulnar aspect rests on the image receptor while the radial side is elevated. If the ordering clinician is concerned about a scaphoid fracture, an ulnar deviation (scaphoid) view of the wrist may be requested. This is the same as a standard PA view with the hand/wrist resting flat on the image receptor, but instead of a neutral (straight) position of the hand/wrist, the hand/wrist is deviated to the ulnar side, thereby elongating the scaphoid. If there is a concern for injury to the scapholunate ligament, the provider may order a clenched fist view to evaluate for widening the scapholunate interval. Widening of the scapholunate interval suggests ligament injury. The clenched fist view is similar to the PA view of the wrist, but the fingers are tightly flexed instead of loosely flexed.

Forearm: For an AP view of the forearm, the patient is seated at the end of the table. The arm is extended, and the hand is supinated (palm up). The wrist and elbow joints are included within the field of view. To acquire a lateral forearm radiograph, the elbow should be flexed 90 degrees during the acquisition of a true lateral position. This is obtained by resting the flexed elbow and forearm on the receptor with the ulnar side down (on the receptor) and the radial (thumb) side up (closer to the beam).

Elbow: The AP elbow radiograph requires the elbow to be extended with the hand supinated. An AP oblique radiograph requires the elbow to be oriented 45 degrees in internal rotation. A lateral radiograph of the elbow requires the elbow to be flexed 90 degrees with the forearm and humerus laying flat on the table and the image receptor, ulnar side down on the receptor, and thumb/radial side up.

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Humerus: The humerus AP radiograph is obtained with the patient standing erect or supine, with the humerus aligned to the long axis of the image receptor. For a true AP view, the arm needs to be abducted slightly with the hand supinated. A lateral radiograph of the humerus can be obtained in different ways. For example, 1 method of obtaining a lateral view includes placing the image receptor vertically between the arm and the thorax.

Shoulder: A shoulder series typically includes at least 2 orthogonal views (for example, anterior-posterior and the lateral or scapular Y view) of the glenohumeral joint. For the AP view, the arm is slightly abducted, and the thorax can be rotated to place the posterior shoulder against the image receptor. The center of the image receptor is at the glenohumeral joint. The arm/hand can be neutral, internal, or external, affecting the projection of the humeral head. Depending on the clinical scenario and department protocols, additional modifications can be obtained. Additional predictions include axillary and Grashey views (AP oblique). The Grashey view is obtained with the patient rotated 35-45 degrees so the X-ray beam is parallel to the articular surface of the glenoid. The axillary view is a substitution for the scapular Y view. In the trauma setting, it is a more reliable assessment of glenohumeral alignment as it is less susceptible to patient positioning and technique errors. An understanding of the expected normal radiographic appearance is essential for image interpretation. For example, in the setting of posterior shoulder dislocation, AP views of the shoulder obtained with internal and external rotation may look similar due to entrapment of the dislocated humeral head on the glenoid. Under such circumstances, the technician must label the images as internal and external rotation to show the radiologist that these represent 2 unique images and not a repeat of 1 view. Another clue to posterior glenohumeral dislocation is an overlap of the humeral head and glenoid on the Grashey view or lack of overlap on the AP view.

Foot: For the anterior-posterior image acquisition of the foot, the patient is supine or seated with the plantar surface on the image receptor. The foot is extended, and the plantar surface is flat on the image receptor. The anterior-posterior medial oblique view requires the foot to be obliquely positioned 30 to 40 degrees. The lateral radiograph requires the patient to be recumbent on the affected side with the knee flexed. The plantar surface of the foot is perpendicular to the image receptor, thereby acquiring a true lateral image. The weight-bearing anterior-posterior foot radiograph requires the patient’s weight to be evenly distributed with both feet on 1 image receptor. The weight-bearing lateral image requires the image receptor to be placed vertically between the feet and high enough for a horizontal central ray.

Ankle: The patient is supine or seated on the table with the leg extended. The ankle and leg are aligned parallel to the edge of the image receptor. There should be no rotation to acquire a true anterior-posterior view. For the ankle mortise view, the long axis of the foot is internally rotated 15 to 20 degrees to have the intermalleolar line parallel to the tabletop. For the lateral ankle view, the patient is in a lateral recumbent position on the table with the foot dorsiflexed 90 degrees. The lateral aspect of the ankle is generally placed against the receptor with an X-ray beam directed from medial to lateral.

Tibia-fibula: For the AP view of the tibia-fibula, the leg is extended while ensuring no rotation of the knee or ankle. The unaffected limb is placed behind the patient with the affected side down for the lateral view. Support can be placed along the distal aspect of the affected foot to obtain a true lateral image.

Knee: For the AP view of the knee, the leg is extended and centered on the central ray. The leg is rotated inward to place the knee and the lower leg in a true anterior-posterior position. The image receptor is centered on the central ray. The patient is positioned on the affected side for a lateral view, with the knee flexed 20-30 degrees. One method to obtain the tunnel view is to have the knee flexed 40-50 degrees with the patient prone and support placed under the tibia-fibula.

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