2: General Anatomy and Radiographic Positioning Terminology

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General Anatomy

Radiographers must possess a thorough knowledge of anatomy, physiology, and osteology to obtain radiographs that show the desired body part. Anatomy is the term applied to the science of the structure of the body. Physiology is the study of the function of the body organs. Osteology is the detailed study of the body of knowledge related to the bones of the body.
Radiographers also must have a general understanding of all body systems and their functions. Particular attention must be given to gaining a thorough understanding of the skeletal system and the surface landmarks used to locate different body parts. The radiographer must be able to visualize mentally the internal structures that are to be radiographed. By using external landmarks, the radiographer should be able to properly position body parts to obtain the best diagnostic radiographs possible.

Body Planes

The full dimension of the human body as viewed in the anatomic position (see Chapter 1) can be effectively subdivided through the use of imaginary body planes. These planes slice through the body at designated levels from all directions. The following four fundamental body planes referred to regularly in radiography are illustrated in Fig. 2.1A:

Sagittal plane

A sagittal plane divides the entire body or a body part into right and left segments. The plane passes vertically through the body from front to back (see Fig. 2.1A and B). The midsagittal plane is a specific sagittal plane that passes through the midline of the body and divides it into equal right and left halves (see Fig. 2.1C).
Coronal plane
A coronal plane divides the entire body or a body part into anterior and posterior segments. The plane passes through the body vertically from one side to the other (see Fig. 2.1A and B). The midcoronal plane is a specific coronal plane that passes through the midline of the body, dividing it into equal anterior and posterior halves (see Fig. 2.1C). This plane is sometimes referred to as the midaxillary plane.
Horizontal plane
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Fig. 2.1  Planes of the body. (A) A patient in anatomic position with four planes identified. (B) Top-down perspective of patient’s body showing sagittal plane through left shoulder, coronal plane through anterior head, and oblique plane through right shoulder. (C) Midsagittal plane dividing body equally into right and left halves and midcoronal plane dividing body equally into anterior and posterior halves. Sagittal, coronal, and horizontal planes are always at right angles to one another.

(A) The sagittal plane, coronal plane, horizontal plane, and oblique plane are marked on the human body. A vertical plane running from front to back and divides the body into left and right side median vertical longitudinal plane divides the body into right and left halves. A vertical line runs from side to side and divides the body into anterior and posterior portions. A horizontal plane divides the body into upper and lower parts. (B) The top-down view of a human body shows the sagittal plane through the left shoulder, the coronal plane through the anterior head, and the oblique plane through the right shoulder. (C) The top-down view of a human body shows the Midsagittal plane dividing body equally into right and left halves and the midcoronal plane dividing body equally into anterior and posterior halves.

Oblique plane
An oblique plane can pass through a body part at any angle among the three previously described planes (see Fig. 2.1A and B). Planes are used in radiographic positioning to center a body part to the image receptor (IR) or central ray and to ensure that the body part is properly oriented and aligned with the IR. For example, the midsagittal plane may be centered and perpendicular to the IR, with the long axis of the IR parallel to the same plane. Planes can also be used to guide projections of the central ray. The central ray for an anteroposterior (AP) projection passes through the body part parallel to the sagittal plane and perpendicular to the coronal plane. Quality imaging requires attention to all relationships among body planes, the IR, and the central ray.
Body planes are used in computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound (US) to identify the orientation of anatomic cuts or slices shown in the procedure (Fig. 2.2). Imaging in several planes is often used to show large sections of anatomy (Fig. 2.3).
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Fig. 2.2  MRI of the knee in four planes. (A) Sagittal. (B) Coronal. (C) Horizontal. (D) Oblique, 45 degrees.

(A) An M R I shows the sagittal plane of the knee joint. The femur head has a well-defined outline. (B) An M R I shows the horizontal plane of the knee joint. The intercondylar fossa and posteroinferior articular surfaces of the condyles of the femur are visible. The open joint space is dark. (C) An M R I shows the oblique plane of the knee joint. It is M Shaped. (D) An M R I shows the oblique plane of the knee joint. The soft tissues appear white and the bony elements appear dark and grainy.

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Fig. 2.3  Large sections of anatomy are often imaged in different planes. (A) Coronal plane of abdomen and lower limb. (B) Sagittal plane of abdomen and lower limb at level of left kidney, left acetabulum, and left knee.

(A) An M R I shows the abdomen and the lower limb including the kidney, acetabulum, and knee. They appear white. (B) An M R I shows the abdomen and the lower limb including the left kidney, left acetabulum, and left knee.

Special Planes

Two special planes are used in radiographic positioning. These planes are localized to a specific area of the body only.
Interiliac plane
Occlusal plane
The occlusal plane is formed by the biting surfaces of the upper and lower teeth with the jaws closed (see Fig. 2.4B). It is used in positioning of the odontoid process and in some head projections.

Body Cavities

The two great cavities of the torso are the thoracic and abdominal cavities (Fig. 2.5). The thoracic cavity is subdivided into a pericardial segment and two pleural portions. Although the abdominal cavity has no intervening partition, the lower portion is called the pelvic cavity. Some anatomists combine the abdominal and pelvic cavities and refer to them as the abdominopelvic cavity. The principal structures located in the cavities are listed on the following page.
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Fig. 2.4  Special planes. (A) Interiliac plane transecting trunk at tops of iliac crests. (B) Occlusal plane formed by biting surfaces of teeth.

(A) Diagram shows the lateral surface of the body placed on the I R with a support under the body. A horizontal dashed line labeled interillac plane passes through the body. (B) Diagram shows the lateral view of the skull. A dashed line touches the incisal edges of the incisors and tips of the occluding surfaces of the posterior teeth.

Thoracic cavity
Abdominal cavity
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Fig. 2.5  Anterior view of torso showing two great cavities: thoracic and abdominopelvic.

An anterior view of the human body shows two cavities. The lungs, heart, abdomen, and pelvis are highlighted. The parts labeled are the thoracic cavity (including pleural cavity and pericardial cavity) and abdominal cavity (abdominopelvic cavity) including abdominal cavity and pelvic cavity.

Divisions of the Abdomen

The abdomen is the portion of the trunk that is bordered superiorly by the diaphragm and inferiorly by the superior pelvic aperture (pelvic inlet). The location of organs or an anatomic area can be described by dividing the abdomen according to one of two methods: four quadrants or nine regions.
Quadrants
The abdomen is often divided into four clinical divisions called quadrants (Fig. 2.6). The midsagittal plane and a horizontal plane intersect at the umbilicus and create the boundaries. The quadrants are named as follows:
Dividing the abdomen into four quadrants is useful for describing the location of the various abdominal organs. For example, the spleen can be described as being located in the LUQ.
Regions
Some anatomists divide the abdomen into nine regions by using four planes (Fig. 2.7). These anatomic divisions are not used as often as quadrants in clinical practice. The nine regions of the body, divided into three groups, are named as follows:
Superior
Middle
Inferior
In the clinical setting, a patient could be described as having “epigastric” pain. A patient with discomfort in the right lower abdomen could be described as having “RLQ” pain. Sometimes a quadrant term is used, and other times a region term is used.
Diagram shows the four regions of the abdomen, marked clockwise as follows: right upper quadrant, left upper quadrant, left lower quadrant, and right lower quadrant
Fig. 2.6  Four quadrants of abdomen.
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Fig. 2.7  Nine regions of abdomen.

Cutaway model of the human body shows regions of abdomen divided into a 3-by-3 matrix, marked left to right in each region as follows: Upper region: Right hypochondriac, epigastric, and left hypochondriac. Middle region: Right lumbar, umbilical, and left lumbar. Lower region: Right iliac, hypogastric, and left iliac.

Surface Landmarks

Most anatomic structures cannot be visualized directly; the radiographer must use various protuberances, tuberosities, and other external indicators to position the patient accurately. These surface landmarks enable the radiographer to obtain radiographs of optimal quality consistently for a wide variety of body types. If surface landmarks are not used for radiographic positioning or if they are used incorrectly, the chance of having to repeat the radiograph greatly increases.
Many commonly used landmarks are listed in Table 2.1 and diagrammed in Fig. 2.8. These landmarks are accepted averages for most patients and should be used only as guidelines. Variations in anatomic build or pathologic conditions may warrant positioning compensation on an individual basis. The ability to compensate is gained through experience. In the Atlas, positioning instructions based on external landmarks are for average-sized adults.

TABLE 2.1

External landmarks related to body structures at the same level
Body structures External landmarks
Cervical area (see  Fig. 2.8 )
C1 Mastoid tip
C2, C3 Gonion (angle of mandible)
C3, C4 Hyoid bone
C5 Thyroid cartilage
C7, T1 Vertebra prominens
Thoracic area
T1 Approximately 2 inches (5 cm) above level of jugular notch
T2, T3 Level of jugular notch
T4, T5 Level of sternal angle
T7 Level of inferior angles of scapulae
T9, T10 Level of xiphoid process
Lumbar area
L2, L3 Inferior costal margin
L4, L5 Level of superiormost aspect of iliac crests
Sacrum and pelvic area
S1, S2 Level of anterior superior iliac spine (ASIS)
Coccyx Level of pubic symphysis and greater trochanters

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Fig. 2.8  Surface landmarks. (A) Head and neck. (B) Torso.

(A) Diagram shows the lateral view of the head. The commonly used landmarks are labeled as follows: T E A (top of ear attachment), gonion, mastoid tip, vertebra prominens, C 1, C 3, C 5, C 7, T 1, T 3, hyoid bone, thyroid cartilage, and jugular notch. (B) Diagram shows the anterior view of the human body or the torso. The commonly used landmarks labeled are marked from top to bottom as follows: C 5 and thyroid cartilage, T 1, T2, T3, and jugular notch, T 4, T 5, and sternal angle, T7 and inferior angle of the scapula, T 9, T 10, and xiphoid process, L 2, L 3, and inferior costal margin, L 4, L 5, and the iliac crest, S 1 and anterior superior iliac spine, and coccyx, pubic symphysis, and greater trochanters.

Body Habitus

Common variations in the shape of the human body are termed the body habitus. Mills 1 determined the primary classifications of body habitus based on his study of 1000 patients. The specific type of body habitus is important in radiography because it determines the size, shape, and position of the organs of the thoracic and abdominal cavities.
Body habitus directly affects the location of the following:
An organ such as the gallbladder may vary in position by 8 inches, depending on the body habitus. The stomach may be positioned horizontally, high, and in the center of the abdomen for one type of habitus and may be positioned vertically, low, and to the side of the midline in another type. Fig. 2.9 shows an example of the placement, shape, and size of the lungs, heart, and diaphragm in patients with four different body habitus types.
Body habitus and placement of the thoracic and abdominal organs are also important in the determination of technical and exposure factors. The standard placement and size of the IR may have to be changed because of body habitus. The selection of kilovolt (peak) and milliampere-second exposure factors may also be affected by the type of habitus because of wide variations in physical tissue density. These technical considerations are described in greater detail in radiography physics and imaging texts.
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Fig. 2.9  Placement, shape, and size of lungs, heart, and diaphragm in patients with four different body habitus types. (A) Sthenic. (B) Hyposthenic. (C) Asthenic. (D) Hypersthenic (crosswise exposure field).

(A) An x-ray shows the lungs in full inspiration. The lungs filled with air appear radiolucent. The heart and the region below the diaphragm appear radiopaque. (B) An x-ray shows the lungs in full expiration. The lungs appear darker than in (A). The diaphragm is depressed. (C) A diagram shows the anterior view of the human body with the lungs highlighted. The diaphragm is positioned lower. An x-ray shows the anterior view of the human body and the lungs appear radiolucent. The diaphragm is positioned lower. The anterior ends of the ribs are less sharply visualized. (D) An x-ray shows the anterior view of the human body and the lungs appear radiolucent. The diaphragm arches posteriorly from the level of about the sixth or seventh costal cartilage to the level of the ninth or tenth thoracic vertebra. The left side of the diaphragm lies at a slightly lower level.

Box 2.1 describes specific characteristics of the four types of body habitus and outlines their general shapes and variations. The four major types of body habitus and their approximate frequency in the population are identified as follows:
More than 85% of the population has either a sthenic or hyposthenic body habitus. The sthenic type is considered the predominant type of habitus. The relative shape of patients with a sthenic or hyposthenic body habitus and the position of their organs are referred to in clinical practice as ordinary or average. All standard radiographic positioning and exposure techniques are based on these two groups. Radiographers must become thoroughly familiar with the characteristics and organ placement of these two body types.
BOX 2.1  Four types of body habitus: prevalence, organ placement, and characteristics
Sthenic, 50%
Organs
Characteristics
Asthenic, 10%
Organs
Characteristics
Hyposthenic, 35%
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Organs and characteristics for this habitus are intermediate between sthenic and asthenic body habitus types; this habitus is the most difficult to classify.
Hypersthenic, 5%
Organs
Characteristics
Note the significant differences between the two extreme habitus types (i.e., asthenic and hypersthenic). The differences between sthenic and hyposthenic types are less distinct.
Radiographers must also become familiar with the two extreme habitus types: asthenic and hypersthenic. In these two small groups (15% of the population), placement and size of the organs significantly affect positioning and the selection of exposure factors. Consequently, radiography of these patients can be challenging. Experience and professional judgment enable the radiographer to determine the correct body habitus and to judge the specific location of the organs.
Body habitus is not an indication of disease or other abnormality, and it is not determined by body fat or by the physical condition of the patient. Habitus is simply a classification of the four general shapes of the trunk of the human body. When positioning patients, the radiographer should be conscious that habitus is not associated with height or weight. Four patients of equal height could have four different trunk shapes (Fig. 2.10).
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Fig. 2.10  Different trunks are shown for asthenic and hypersthenic habitus, the two extremes. The abdomen is the same length in both patients (diaphragm-to-pubic symphysis). The abdominal organs are in completely different positions. Note high stomach in hypersthenic habitus (green color) and low stomach in asthenic habitus. Art is based on actual autopsy findings by R. Walter Mills, MD.

Diagram shows an anterior view of a human body titled hypersthenic on the left and an anterior view of a human body titled asthenic on the right. The abdominal organs are in completely different positions. The diaphragm and the pubic symphysis are the same lengths in both patients. The stomach is shaded in green color. It is high in hypersthenic and low in asthenic.

Osteology

The adult human skeleton is composed of 206 primary bones. Ligaments unite the bones of the skeleton. Bones provide the following:
  1. • Attachment for muscles
  2. • Mechanical basis for movement
  3. • Protection of internal organs
  4. • A frame to support the body
  5. • Storage for calcium, phosphorus, and other salts
  6. • Production of red and white blood cells
The 206 bones of the body are divided into two main groups:
The axial skeleton supports and protects the head and trunk with 80 bones (see Table 2.2). The appendicular skeleton allows the body to move in various positions and from place to place with its 126 bones (Table 2.3). Fig. 2.11 identifies these two skeletal areas.

TABLE 2.2

Axial skeleton: 80 bones
Area Bones Number
Skull Cranial 8
Facial 14
Auditory ossicles a 6
Neck Hyoid 1
Thorax Sternum 1
Ribs 24
Vertebral column Cervical 7
Thoracic 12
Lumbar 5
Sacrum 1
Coccyx 1

TABLE 2.3

Appendicular skeleton: 126 bones
Area Bones Number
Shoulder girdle Clavicles 2
Scapulae 2
Upper limbs Humeri 2
Ulnae 2
Radii 2
Carpals 16
Metacarpals 10
Phalanges 28
Lower limbs Femora 2
Tibias 2
Fibulae 2
Patellae 2
Tarsals 14
Metatarsals 10
Phalanges 28
Pelvic girdle Hip bones 2
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Fig. 2.11  Two main groups of bones. (A) Axial skeleton. (B) Appendicular skeleton.

(A) shows a skeletal view of the human body. The skull, neck, thorax, and vertebral column are highlighted in blue. (B) shows the skeletal view of the human body. The shoulder girdle, upper limbs, lower limbs, and pelvic girdle are highlighted in blue.

General Bone Features

The general features of most bones are shown in Fig. 2.12. All bones are composed of a strong, dense outer layer called the compact bone and an inner portion of less dense spongy bone. The hard outer compact bone protects the bone and gives it strength for supporting the body. The softer spongy bone contains a spiculated network of interconnecting spaces called the trabeculae (Fig. 2.13). The trabeculae are filled with red and yellow marrow. Red marrow produces red and white blood cells, and yellow marrow stores adipose (fat) cells. Long bones have a central cavity called the medullary cavity, which contains trabeculae filled with yellow marrow. In long bones, the red marrow is concentrated at the ends of the bone and not in the medullary cavity.
A tough, fibrous connective tissue called the periosteum covers all bony surfaces except the articular surfaces, which are covered by the articular cartilage. The tissue lining the medullary cavity of bones is called the endosteum. Bones contain various knob-like projections called tubercles and tuberosities, which are covered by the periosteum. Muscles, tendons, and ligaments attach to the periosteum at these projections. Blood vessels and nerves enter and exit the bone through the periosteum.
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Fig. 2.12  General bone features and anatomic parts.

The general features of the bones are labeled as follows: epiphyseal line, articular cartilage, spongy bone (red marrow), compact bone, endosteum, greater tubercle, trabeculae, medullary cavity (yellow marrow), and periosteum. The trabeculae are filled with red and yellow marrow. The medullary cavity contains trabeculae filled with yellow marrow.

An x-ray of the distal femur shows white streaks on the head of the femur. It appears grainy.
Fig. 2.13  Radiograph of distal femur and condyles showing bony trabeculae within entire bone.

Bone Vessels and Nerves

Bone Development

Ossification is the term given to the development and formation of bones. Bones begin to develop in the second month of embryonic life. Ossification occurs separately by two distinct processes: intermembranous ossification and endochondral ossification.
Intermembranous ossification
Bones that develop from fibrous membranes in the embryo produce the flat bones—bones of the skull, clavicles, mandible, and sternum. Before birth, these bones are not joined. As flat bones grow after birth, they join and form sutures. Other bones in this category merge and create the various joints of the skeleton.
Endochondral ossification
Bones created by endochondral ossification develop from hyaline cartilage in the embryo and produce short, irregular, and long bones. Endochondral ossification occurs from two distinct centers of development called primary and secondary centers of ossification.
Primary ossification
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Fig. 2.14  Long bone end showing its rich arterial supply. Arteries, veins, and nerves enter and exit bone at the same point.

Diagram shows the veins in the long bone. The parts labeled are as follows: epiphyseal line, epiphyseal artery, periosteal arteries, nutrient artery, and nutrient foramen. The epiphyseal artery separately enters the ends of long bones. The periosteal arteries enter at numerous points.

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Fig. 2.15  Primary and secondary ossification of bone. (A) Primary ossification of tibia before birth. (B) Secondary ossification, which forms two epiphyses after birth. (C) Full growth into single bone, which occurs by age 21 years.

Diagram (A) shows a short central shaft. The parts labeled are the primary ossification center and the diaphysis. Irregular circular patches are between two horizontal lines. Diagram (B) shows a shaft of a bone and the secondary ossification center on the top and the bottom. The parts labeled on the left are epiphysis, diaphysis, and epiphysis. The parts labeled on the right side are the secondary ossification center, epiphyseal plate, epiphyseal plate, and secondary ossification center. A separate bone begins to develop at both ends of each long bone. Diagram (C0 shows a plate of cartilage called the epiphyseal plate develops between the two areas. The parts labeled are the epiphyseal line on top and the epiphyseal line at the bottom. It divides the ends of the epi[hysis into two parts.

Secondary ossification
Secondary ossification occurs after birth when a separate bone begins to develop at both ends of each long bone. Each end is called the epiphysis (see Fig. 2.15B). At first, the diaphysis and the epiphysis are distinctly separate. As growth occurs, a plate of cartilage called the epiphyseal plate develops between the two areas (see Fig. 2.15C). This plate is seen on long bone radiographs of all pediatric patients (Fig. 2.16A). The epiphyseal plate is important radiographically because it is a common site of fractures in pediatric patients. Near age 21 years, full ossification occurs, and the two areas become completely joined; only a moderately visible epiphyseal line appears on the bone (see Fig. 2.16B).
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Fig. 2.16  (A) Radiograph of a 6-year-old child. Epiphysis and epiphyseal plate shown on knee radiograph (arrows). (B) Radiograph of same area in a 21-year-old adult. Full ossification has occurred, and only subtle epiphyseal lines are seen (arrows). (C) PA radiograph of hand of a 2½-year-old child. Note early stages of ossification in epiphyses at proximal ends of phalanges and first metacarpal, distal ends of other metacarpals, and radius. C, From Standring S. Gray’s Anatomy. 40th ed. New York: Churchill Livingstone; 2009.

(A) An x-ray shows the knee joint. The epiphysis and the epiphysial plate are clearly visible. There are open intraarticular joint spaces. (B) An x-ray shows the knee joint. The epiphysial lines are slightly visible. They appear white. Two white arrows point at the lines. (C) An x-ray shows a hand. There are gaps between the proximal ends of phalanges and first metacarpal, distal ends of other metacarpals, and radius.

Classification of Bones
Long bones
Long bones are found only in the limbs. They consist primarily of a long cylindric shaft called the body and two enlarged, rounded ends that contain a smooth, slippery articular surface. A layer of articular cartilage covers this surface. The ends of these bones all articulate with other long bones. The femur and the humerus are typical long bones. The phalanges of the fingers and toes are also considered long bones. A primary function of long bones is to provide support.
Short bones
Short bones consist mainly of cancellous bone containing red marrow and have a thin outer layer of compact bone. The carpal bones of the wrist and the tarsal bones of the ankles are the only short bones. They are varied in shape and allow minimum flexibility of motion in a short distance.
Flat bones
Flat bones consist largely of two tables of compact bone. The narrow space between the inner and outer tables contains cancellous bone and red marrow, or diploë, as it is called in flat bones. The bones of the cranium, sternum, and scapula are examples of flat bones. The flat surfaces of these bones provide protection, and their broad surfaces allow muscle attachment.
Irregular bones
Irregular bones are so termed because their peculiar shapes and variety of forms do not place them in any other category. The vertebrae and the bones in the pelvis and face fall into this category. Similar to other bones, they have compact bone on the exterior and cancellous bone containing red marrow in the interior. Their shape serves many functions, including attachment for muscles, tendons, and ligaments, or they attach to other bones to create joints.
Sesamoid bones
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Fig. 2.17  Bones are classified by shape. (A) Humerus is a long bone. (B) Carpals of the wrist are short bones. (C) Sternum is a flat bone. (D) Vertebra is an irregular bone. (E) Patella is a sesamoid bone.

Diagram (A) shows a long, narrow, and cylindrical bone. Diagram (B) shows cancellous bones. They are varied in shape. Diagram (C ) shows the flat bone called sternum in the middle and the ribs rise from it. Diagram (D) shows an irregularly shaped bone. Diagram (E) shows a small and oval-shaped bone.

TABLE 2.4

Structural classification of joints
Connective tissue Classification Movement
Fibrous Slightly movable
Immovable
Immovable
Cartilaginous Slightly movable
Immovable
Synovial Freely movable
Freely movable
Freely movable
Freely movable
Freely movable
Freely movable

Arthrology

Arthrology is the study of the joints, or articulations between bones. Joints make it possible for bones to support the body, protect internal organs, and create movement. Various specialized articulations are necessary for these functions to occur.
The two classifications of joints described in anatomy books are functional and structural. Studying both classifications can be confusing. The most widely used and primary classification is the structural classification, which is used to describe all the joints in this atlas. This is also the classification recognized by Nomina Anatomica. For academic interest, a brief description of the functional classification is provided.
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Fig. 2.18  Examples of three types of fibrous joints. (A) Syndesmosis: Inferior tibiofibular joint. (B) Suture: Sutures of skull. (C) Gomphosis: Roots of teeth in alveolus.

Diagram (A) shows inferior tibiofibular joint. The sheets of fibrous tissue are highlighted and are marked by an arrow. Diagram (B) shows the lateral view of the skull. The sutures are highlighted. An enlarged image shows the sutures of the skull. Diagram (C) shows the roots of teeth in the alveolus. The fibrous periodontal ligaments underlying the tooth are highlighted. The alveolus appears grainy.

Functional Classification

When joints are classified as functional, they are broken down into three classifications. These classifications are based on the mobility of the joint, as follows:

Structural Classification
Structurally, joints are classified into three distinct groups on the basis of their connective tissues: fibrous, cartilaginous, and synovial. Within these three broad categories are the 11 specific types of joints. They are numbered in the text for easy reference to Table 2.4.
Fibrous joints
Fibrous joints do not have a joint cavity. They are united by various fibrous and connective tissues or ligaments. These are the strongest joints in the body because they are virtually immovable. The three types of fibrous joints are as follows:
Cartilaginous joints
Cartilaginous joints are similar to fibrous joints in two ways: (1) They do not have a joint cavity, and (2) they are virtually immovable. Hyaline cartilage or fibrocartilage unites these joints. The two types of cartilaginous joints are as follows:
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Fig. 2.19  Examples of two types of cartilaginous joints. (A) Symphysis: Pubic symphysis. (B) Synchondrosis: Epiphyseal plate found between epiphysis and diaphysis of growing long bones.

Diagram (A) shows the pubic symphysis highlighted on the pubic bones. An enlarged image below shows the pubic symphysis marked by two blue curves. Diagram (B) shows the epiphyseal plate found between epiphysis and diaphysis of a bone. They are granulated at the ends.

Synovial joints
An articular capsule completely surrounds and enfolds all synovial joints to join the separate bones together. The outer layer of the capsule is called the fibrous capsule, and its fibrous tissue connects the capsule to the periosteum of the two bones. The synovial membrane, which is the inner layer, surrounds the entire joint to create the joint cavity. The membrane produces a thick, yellow, viscous fluid called synovial fluid. Synovial fluid lubricates the joint space to reduce friction between the bones. The ends of the adjacent bones are covered with articular cartilage. This smooth and slippery cartilage permits ease of motion. The two cartilages do not actually touch because they are separated by a thin layer of synovial membrane and fluid.
Some synovial joints contain a pad of fibrocartilage called the meniscus, which surrounds the joint. Specific menisci intrude into the joint from the capsular wall. They act as shock absorbers by conforming to and filling in the large gaps around the periphery of the bones. Some synovial joints also contain synovial fluid-filled sacs outside the main joint cavity, which are called the bursae. Bursae help to reduce friction between skin and bones, tendons and bones, and muscles and bones. Menisci, bursae, and other joint structures can be visualized radiographically by injecting iodine-based contrast medium and/or air directly into the synovial cavity. This procedure, called arthrography, is detailed in Chapter 13.
The six synovial joints complete the 11 types of joints within the structural classification. They are listed in order of increasing movement. The most common name of each joint is identified, and the less frequently used name is given in parentheses.
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Fig. 2.20  Lateral cutaway view of knee showing distinguishing features of a synovial joint.

A cross-sectional diagram of bone shows labels marked from top to bottom as follows: suprapatellar bursa, articular capsule, infrapatellar bursa, joint cavity (synovial fluid), meniscus (cross-section), articular capsule, synovial membrane, and articular cartilage.

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Fig. 2.21  Examples of six types of synovial joints. (A) Gliding: Intercarpal joints of wrist. (B) Hinge: Elbow joint. (C) Pivot: Atlas and axis of cervical spine (viewed from above). (D) Ellipsoid: Radiocarpal joint of wrist. (E) Saddle: Carpometacarpal joint. (F) Ball and socket: Hip joint.

Diagram (A) shows the Intercarpal joints of the wrist. The carpals have yellow granules on them. The cartilages are shaded. Diagram (B) shows the elbow joint. An arrow indicates flexion and extension. Diagram (C ) shows the top view of the atlas and axis of the cervical spine. An arrow points at the ends projecting at the ends. Diagram (D 1, D 2) shows joints of the wrist. An arrow indicates movement in two directions at right angles to each other. Diagram (E) shows the carpometacarpal joint. The face of each bone end has a concave and a convex aspect. An enlarged image of the carpometacarpal joint shows a gap between the two ends. Diagram (F) shows the hip joint. The ball and socket area is highlighted using a dashed line.

Bone Markings and Features

The following anatomic terms are used to describe either processes or depressions on bones.

Processes or Projections

Processes or projections extend beyond or project out from the main body of a bone and are designated by the following terms:

Depressions

Depressions are hollow or depressed areas and are described by the following terms:

Fractures

A fracture is a break in the bone. Fractures are classified according to the nature of the break. Several general terms can pertain to them:
Common classifications of fractures are listed as follows and identified in Fig. 2.22:
  1. • Compression
  2. • Open or compound
  3. • Simple
  4. • Greenstick
  5. • Transverse
  6. • Spiral or oblique
  7. • Comminuted
  8. • Impacted
Many fractures fall into more than one category. A fracture could be spiral, closed, and nondisplaced.
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Fig. 2.22  Common classifications of fractures.

Eight diagrams show the classification of the fractures. The first diagram shows compression between the vertebral column. The second diagram shows a leg with an open or compound fracture. A fragment of bone breaking through the skin. The third diagram shows a leg with a simple fracture. A fracture of the bone only, without damage to the surrounding tissue. The fourth diagram shows a leg with a greenstick fracture. There is a crack or break on one side of a long bone. The fifth diagram shows a leg with a transverse fracture. The bone breaks at a 90-degree angle to the long axis. The sixth diagram shows a leg with a spiral or oblique fracture. The break has a curved or sloped pattern. The seventh diagram shows a leg with a comminuted fracture. There is a break in the bone into more than two fragments. The eighth diagram shows a leg with an impacted fracture. The fracture shows bone fragments driven into each other.

Anatomic Relationship Terms

Radiographic Positioning Terminology
Approval of Canadian positioning terminology is the responsibility of the CAMRT Radiography Council on Education. This council provided information used in the development of this chapter and clearly identified terminology differences between the United States and Canada. 5
image
Fig. 2.23  (A) Use of common radiology terms proximal and distal. (B) Use of common radiology terms caudad angle and cephalad angle.

Diagram (A) shows the anterior surface of the leg. An arrow pointing upwards is labeled proximal and an arrow pointing downwards is labeled distal. Diagram (B) shows a patient lying on the radiographic table in a supine position. The legs are elevated by placing a pillow under the knee joints. His arms are placed along the sides of his body. An arrow pointing towards the chest is labeled as cephalad central ray angle and an arrow pointing towards the thighs is labeled as caudad central ray angle.

The terminology used by ARRT and CAMRT is consistent overall with that used in this atlas.
The following are the four positioning terms most commonly used in radiology:
  1. • Projection
  2. • Position
  3. • View
  4. • Method

icon Projection
Projections can also be defined by the relationship formed between the central ray and the body as the central ray passes through the entire body or body part. Examples include axial and tangential projections.
All radiographic examinations described in this atlas are standardized and titled by their x-ray projection. The x-ray projection accurately and concisely defines each image produced in radiography. Table 2.5 provides a summary view of the most common radiographic projections linked to the body positions. The essential radiographic projections follow.
Anteroposterior projection
In Fig. 2.25, a perpendicular central ray enters the anterior body surface and exits the posterior body surface. This is an AP projection. The patient is shown in the supine or dorsal recumbent body position. AP projections can also be achieved with upright, seated, or lateral decubitus positions.
Posteroanterior projection
In Fig. 2.26, a perpendicular central ray is shown entering the posterior body surface and exiting the anterior body surface. This illustrates a posteroanterior (PA) projection with the patient in the upright body position. PA projections can also be achieved with seated, prone (ventral recumbent), and lateral decubitus positions.
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Fig. 2.24  All three body positions produce AP projections.

The first diagram shows a patient standing in an upright position against the radiographic table. The perpendicular C R enters the anterior surface. The second diagram shows a patient in a supine position on the radiographic table. The perpendicular C R enters the posterior surface. The third diagram shows a patient's lateral decubitus. A support is placed under the head. The perpendicular C R enters the lateral surface.

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Fig. 2.25  AP projection of chest. Central ray enters anterior aspect and exits posterior aspect.

The first diagram shows the top view of a patient in a supine position on the radiographic table. The central ray enters the anterior aspect and exits posteriorly. The second diagram shows a patient in a supine position on the radiographic table. The central ray enters the anterior aspect and exits posteriorly.

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Fig. 2.26  PA projection of chest. Central ray enters posterior aspect and exits anterior aspect. Patient is in upright position.

The first diagram shows the top view of a patient standing with his chest against the I R. The central ray enters the anterior aspect and exits posteriorly. The second diagram shows a patient standing with his chest against the I R. The central ray enters the anterior aspect and exits posteriorly.

TABLE 2.5

Summary of common projections
Projections Definition Associated Positions
Anteroposterior (AP) Perpendicular CR enters anterior surface and exits posterior surface of part/body
  1. • Supine
  2. • Upright (facing x-ray tube)
  3. • Lateral decubitus
  4. • Extremity positioned with coronal plane parallel to IR
Posteroanterior (PA) Perpendicular CR enters posterior surface and exits anterior surface of part/body
  1. • Prone
  2. • Upright (facing IR/Bucky)
  3. • Lateral decubitus
  4. • Extremity positioned with coronal plane parallel to IR
Lateral Perpendicular CR enters lateral surface and exits opposite lateral surface of part/body
  1. • Left lateral
  2. • Right lateral
  3. • Dorsal or ventral decubitus
  4. • Extremity positioned with coronal plane perpendicular to IR
AP oblique Perpendicular CR enters anterior surface and exits posterior surface of rotated (obliqued) part/body
  1. • Left posterior oblique (LPO)
  2. • Right posterior oblique (RPO)
  3. • Extremity positioned with coronal plane rotated in relation to IR
∗Specific amount of part/body rotation required∗
PA oblique Perpendicular CR enters posterior surface and exits anterior surface of rotated (obliqued) part/body
  1. • Left anterior oblique (LAO)
  2. • Right anterior oblique (RAO)
  3. • Extremity positioned with coronal plane rotated in relation to IR
∗Specific amount of part/body rotation required∗
Axial CR is angled longitudinally more than 10 degrees
Any position
∗Note more specific axial terms below∗
AP axial
Angled CR enters anterior surface and exits posterior surface of part/body
∗Specific CR angle amount and direction required∗
  1. • Supine
  2. • Upright (facing x-ray tube)
PA axial
Angled CR enters posterior surface and exits anterior surface of part/body
∗Specific CR angle amount and direction required∗
  1. • Prone
  2. • Upright (facing IR/Bucky)
AP axial oblique
Angled CR enters posterior surface and exits anterior of rotated (obliqued) part/body
∗Specific CR angle amount and direction required∗
  1. • LPO or RPO position
∗Specific amount of part/body rotation required∗
PA axial oblique
Angled CR enters posterior surface and exits anterior surface of rotated (obliqued) part/body
∗Specific CR angle amount and direction required∗
  1. • LAO or RAO position
∗Specific amount of part/body rotation required∗

Axial projection
In an axial projection (Fig. 2.27), there is longitudinal angulation of the central ray with the long axis of the body or a specific body part. This angulation is based on the anatomic position and is most often produced by angling the central ray cephalad or caudad. The longitudinal angulation in some examinations is achieved by angling the entire body or body part while maintaining the central ray perpendicular to the IR.
The term axial, as used in this atlas, refers to all projections in which the longitudinal angulation between the central ray and the long axis of the body part is 10 degrees or more. When a range of central ray angles (e.g., 5 to 15 degrees) is recommended for a given projection, the term axial is used because the angulation could exceed 10 degrees. Axial projections are used in a wide variety of examinations and can be obtained with the patient in virtually any body position.
Tangential projection
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Fig. 2.27  AP axial projection of skull. Central ray enters anterior aspect at an angle and exits posterior aspect.

The first diagram shows a skull is on a plane with its anterior surface facing up. The central ray is angled 5 to 15 degrees enters the anterior aspect at an angle and exits the posterior aspect. The second diagram shows the top view of a skull on a plane. The central ray enters the anterior aspect at an angle and exits the posterior aspect.

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Fig. 2.28  Tangential projection of zygomatic arch. Central ray skims surface of the skull.

The first diagram shows the dorsal surface of a slight head on the plane. The central ray skims the surface of the skull. The second diagram shows the chin placed on the plane. The central ray is angled 5 to 15 degrees enters the anterior aspect at an angle and exits the posterior aspect.

Lateral projection
Oblique projection
Most oblique projections are achieved by rotating the patient with the central ray perpendicular to the IR. As in the lateral projection, the direction of the central ray for oblique projections is described with reference to the associated radiographic position. A right posterior oblique (RPO) position places the right posterior surface of the body closest to the IR and corresponds with an AP oblique projection exiting through the same side. This relationship is discussed later. Oblique projections can also be achieved for some examinations by angling the central ray diagonally along the horizontal plane rather than rotating the patient.
Complex projections
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Fig. 2.29  Lateral projection of chest. The patient is placed in right lateral position. Right side of the chest is touching IR. Central ray (CR) enters left or opposite side of body.

The first diagram shows the top view of a patient standing with his lateral arm against the I R. The central ray (C R) enters the right and exits through the opposite side of the body. The second diagram shows a patient standing with his lateral arm against the I R with both his arms abducted and extended above and resting on his head. The central ray (C R) enters the right and exits through the opposite side of the body.

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Fig. 2.30  Lateromedial projection of forearm. Central ray enters lateral aspect of forearm and exits medial aspect.

The humerus and the forearm are placed in contact with the table. The long axis of the elbow joint is parallel with the long axis of the forearm. The central ray enters the lateral aspect of the forearm and exits the medial aspect.

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Fig. 2.31  PA oblique projection of chest. Central ray enters posterior aspect of body (even though it is rotated) and exits anterior aspect.

The first diagram shows the top view of a patient standing with his body rotated and the right side of the anterior body surface is against the I R. The central ray enters the posterior aspect of the body and exits the anterior aspect. The second diagram shows a patient lying in a lateral recumbent position. The central ray enters the posterior aspect of the body and exits the anterior aspect.

TABLE 2.6

Special projections summary
Projections Definition
Axiolateral Angled CR enters and exits lateral surfaces of the body/part
Axiolateral oblique Angled CR enters and exits lateral surfaces of a rotated (oblique) body/part
Transthoracic CR passes through the thorax
Craniocaudal CR enters the cranial surface of a part and exits the caudal surface of a part; commonly used in mammography
Tangential CR skims curved surface of part to project it free of superimposition
Inferosuperior CR enters inferior surface and exits superior surface of the part
Superoinferior CR enters superior surface and exits inferior surface of the part
Plantodorsal Specific to the foot; CR enters plantar and exits dorsum surfaces
Dorsoplantar Specific to the foot; CR enters dorsum and exits plantar surfaces
Lateromedial CR passes through a part in the lateral position, entering the lateral and exiting the medial surfaces
Mediolateral CR passes through a part in the lateral position, entering medial and exiting lateral surfaces
Submentovertical Specific to the head; CR enters the inferior surface of the mandible (mentum) and exits the cranial vertex
Acanthoparietal Specific to the head; CR enters the acanthion and exits the parietal bones
Parietoacanthial Specific to the head; CR enters the parietal bones and exits the acanthion
True projections
The term true (true AP, true PA, and true lateral) 6 is often used in clinical practice. True is used specifically to indicate that the body part must be placed exactly in the anatomic position.
A true AP or PA projection is obtained when the central ray is perpendicular to the coronal plane and parallel to the sagittal plane. A true lateral projection is obtained when the central ray is parallel to the normal plane and perpendicular to the sagittal plane. When a body part is rotated for an AP or PA oblique projection, a true AP or PA projection cannot be obtained. In this atlas, the term true is used only when the body part is placed in the anatomic position.
In-profile
In-profile is an outlined or silhouette view of an anatomic structure that has a distinctive shape. The distinctive aspect is not superimposed. The view is frequently seen from the side.

Position
During radiography, general body positions are combined with radiographic positions to produce the appropriate image. For clarification of positioning for an examination, it is often necessary to include references to both because a particular radiographic position, such as right lateral, can be achieved in several general body positions (e.g., upright, supine, lateral recumbent) with differing image outcomes. Specific descriptions of general body positions and radiographic positions follow.
BOX 2.2  Body positions

General body positions Radiographic body positions
Upright Lateral
Seated
Oblique
Right posterior oblique (RPO)
Left posterior oblique (LPO)
Right anterior oblique (RAO)
Left anterior oblique (LAO)
Supine
Prone
Recumbent
FowlerTrendelenburg
Decubitus
Right lateral
Left lateral
Ventral
Dorsal
Lordotic

A patient lying on the radiographic table in a dorsal recumbent position. His arms are placed along the sides of his body. The legs are elevated by placing a pillow under the knee joints.
Fig. 2.32  Supine position of body, also termed dorsal recumbent position. The patient’s knees are flexed for comfort.
A patient lying on the radiographic table in a ventral recumbent position. The anterior surface of the body is facing the table. His arms are placed along the sides of his body.
Fig. 2.33  Prone position of body, also termed ventral recumbent position.
A patient is in the right lateral recumbent position on the radiographic table with both his arms abducted and extended above. Both his arms are resting on his head.
Fig. 2.34  Recumbent position of body, specifically right lateral recumbent position.
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Fig. 2.35  Trendelenburg position of body. Feet are higher than the head.

A patient is in a supine position on the radiographic table with their head tilted downward. His arms are placed along the sides of his body. The legs are elevated by placing a pillow under the knee joints.

General body positions
The following list describes the general body positions. All are commonly used in radiography practice.
Lateral position
Lateral radiographic positions are always named according to the side of the patient that is placed closest to the IR (Figs. 2.39 and 2.40). In this atlas, the right and left lateral positions are indicated as subheadings for all lateral x-ray projections of the head, chest, and abdomen in which either the left or the right side of the patient is placed adjacent to the IR. The specific side selected depends on the condition of the patient, the anatomic structure of clinical interest, and the purpose of the examination. In Figs. 2.39 and 2.40, the x-ray projection for the positions indicated is lateral projection.
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Fig. 2.36  Fowler position of the body. Head is higher than the feet.

A patient is in a supine position on the radiographic table with a head higher than the feet. His arms are placed along the sides of his body. The legs are elevated by placing a pillow under the knee joints.

A patient is lying on the left anterior side (semi-prone) on the radiographic table with the left leg extended. The right knee and thigh are partially flexed.
Fig. 2.37  Sims position of body. The patient is on the left side in recumbent oblique position.
A patient is in a supine position with knees and hip flexed and thighs abducted and rotated externally. The hands are resting on the chest. Both the knees are placed on knee supports.
Fig. 2.38  Lithotomy position of body. Knees and hips are flexed, and thighs are abducted and rotated laterally.
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Fig. 2.39  Left lateral radiographic position of chest results in lateral projection.

The first diagram shows the top view of a patient standing with his lateral arm against the I R. The central ray (C R) enters the right and exits through the opposite side of the body. The second diagram shows a patient standing with his lateral arm against the I R with both his arms abducted and extended above and resting on his head. The central ray (C R) enters the right and exits through the opposite side of the body.

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Fig. 2.40  Right lateral radiographic position of chest results in lateral projection.

The first diagram shows the top view of a patient standing with his lateral arm against the I R. The central ray (C R) enters the left and exits through the opposite side of the body. The second diagram shows a patient standing with his lateral arm against the I R with both his arms abducted and extended above and resting on his head. The central ray (C R) enters the left and exits through the opposite side of the body.

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Fig. 2.41  RAO radiographic position of chest results in PA oblique projection.

The first diagram shows the top view of a patient standing with his body rotated and the right side of the anterior body surface is against the I R. The central ray enters the posterior aspect of the body and exits the anterior aspect. The second diagram shows a patient lying in a lateral recumbent position. The central ray enters the posterior aspect of the body and exits the anterior aspect.

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Fig. 2.42  LAO radiographic position of chest results in PA oblique projection.

The first diagram shows the top view of a patient standing with his body rotated and the left side of the anterior body surface is against the I R. The central ray enters the posterior aspect of the body and exits the anterior aspect. The second diagram shows a patient lying in a lateral recumbent position. The central ray enters the posterior aspect of the body and exits the anterior aspect.

Oblique position
An oblique radiographic position is achieved when the entire body or body part is rotated so that the coronal plane is not parallel with the radiographic table or IR. The angle of oblique rotation varies with the examination and structures to be shown. In this atlas, an angle is specified for each oblique position (e.g., rotated 45 degrees from the prone position).
Oblique positions, similar to lateral positions, are always named according to the side of the patient that is placed closest to the IR. In Fig. 2.41, the patient is rotated with the right anterior body surface in contact with the radiographic table. This is a right anterior oblique (RAO) position because the right side of the anterior body surface is closest to the IR. Fig. 2.42 shows the patient placed in an LAO position.
The relationship between oblique position and oblique projection can be summarized simply. Anterior oblique positions result in PA oblique projections, as shown in Figs. 2.41 and 2.42. Similarly, posterior oblique positions result in AP oblique projections, as illustrated in Figs. 2.43 and 2.44.
The oblique positioning terminology used in this atlas has been standardized using RAO and LAO or RPO and LPO positions along with the appropriate PA or AP oblique projection. For oblique positions of the limbs, the terms medial rotation and lateral rotation have been standardized to designate the direction in which the limbs have been turned from the anatomic position (Fig. 2.45).
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Fig. 2.43  LPO radiographic position of chest results in AP oblique projection.

The first diagram shows the top view of a patient standing with his body rotated and the left side of the posterior body surface is against the I R. The central ray enters the posterior aspect of the body and exits the anterior aspect. The second diagram shows a patient lying in a lateral recumbent position. The central ray enters the posterior aspect of the body and exits the anterior aspect.

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Fig. 2.44  RPO radiographic position of chest results in AP oblique projection.

The first diagram shows the top view of a patient standing with his body rotated and the right side of the posterior body surface is against the I R. The central ray enters the posterior aspect of the body and exits the anterior aspect. The second diagram shows a patient lying in a lateral recumbent position. The central ray enters the posterior aspect of the body and exits the anterior aspect.

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Fig. 2.45  (A) Medial rotation of knee. (B) Lateral rotation of knee.

(A) shows two legs with one leg turned inwards. It is indicated by an arrow pointing towards the other knee. (B) shows two legs with one leg turned outward. It is indicated by an arrow pointing outside.

A patient is placed in the left lateral decubitus radiographic position with the back (posterior surface) closest to the I R. The central ray is directed horizontally.
Fig. 2.46  Left lateral decubitus radiographic position of abdomen results in AP projection. Note horizontal orientation of central ray.
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Fig. 2.47  Right dorsal decubitus radiographic position of abdomen results in right lateral projection. Note horizontal orientation of central ray.

A patient is placed in a dorsal decubitus radiographic position with one side of the body next to the I R. The patient's arms are extended to the vertical position, supporting his head. The central ray is directed horizontally.

Decubitus position
In radiographic positioning terminology, the term decubitus indicates that the patient is lying down and that the central ray is horizontal and parallel with the floor. Three primary decubitus positions are named according to the body surface on which the patient is lying: lateral decubitus (left or right), dorsal decubitus, and ventral decubitus. Of these, the lateral decubitus position is used most often to show the presence of air-fluid levels or free air in the chest and abdomen.
In Fig. 2.46, the patient is placed in the left lateral decubitus radiographic position with the back (posterior surface) closest to the IR. In this position, a horizontal central ray provides an AP projection. Fig. 2.46 is accurately described as an AP projection with the body in the left lateral decubitus position. Alternatively, the patient may be placed with the front of the body (anterior surface) facing the IR, resulting in a PA projection. This would be correctly described as a PA projection of the body in the left lateral decubitus position. Right lateral decubitus positions may be necessary with AP and PA projections, depending on the examination.
In Fig. 2.47, the patient is shown in a dorsal decubitus radiographic position with one side of the body next to the IR. The horizontal central ray provides a lateral projection. This is correctly described as a lateral projection with the patient placed in the dorsal decubitus position. Either side may face the IR, depending on the examination or the patient’s condition.
The ventral decubitus radiographic position (Fig. 2.48) also places a side of the body adjacent to the IR, resulting in a lateral projection. Similar to the earlier examples, the accurate terminology is lateral projection with the patient in the ventral decubitus position. Either side may face the IR.
Lordotic position
The lordotic position is achieved by having the patient lean backward while in the upright body position so that only the shoulders are in contact with the IR (Fig. 2.49). An angulation forms between the central ray and the long axis of the upper body, producing an AP axial projection. This position is used for visualization of pulmonary apices (see Chapter 3) and clavicles (see Chapter 6).
Note to educators, students, and clinicians
In clinical practice, the terms position and projection are often incorrectly used. These are two distinct terms that should not be interchanged. Incorrect use leads to confusion for the student who is attempting to learn the correct terminology of the profession. Educators and clinicians are encouraged to use the term projection generally when describing any examination performed. The word projection is the only term that accurately describes how the body part is being examined. The term position should be used only when referring to placement of the patient’s body. Correct examples are, “We are going to perform a PA projection of the chest with the patient in the upright position,” and “We are going to perform an AP oblique projection of the lumbar spine in the left posterior oblique (LPO) position.”

View

The term view is used to describe the body part as seen by the IR. Use of this term is restricted to the general discussion of a finished radiograph or image. View and projection are exact opposites. For many years, view and projection were often used interchangeably, which led to confusion. In the United States, projection has replaced view as the preferred terminology for describing radiographic images. For consistency, this atlas refers to all views as images or radiographs.
In clinical practice, it is common to see the term view used in radiology procedure orders. For example, a radiology procedure order pulled from the radiology information system (RIS) worklist may state “3 view shoulder.” This should be interpreted as an order for three radiographic projections or positions. The radiology department protocol manual will indicate which three projections are routine for that procedure.

Method
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Fig. 2.48  Left ventral decubitus radiographic position of abdomen results in left lateral projection. Note horizontal orientation of central ray.

The diagram on top shows the top view of a patient with his anterior surface against the table. The side of the body is adjacent to the I R. His arms are placed along the sides of his body. The central ray is directed horizontally. The second diagram shows a patient in a prone position. The side of the body is adjacent to the I R. Both his arms are placed in front of his face. The central ray is directed horizontally.

A patient standing and leaning backward in a position of extreme lordosis. The neck and the shoulder are resting against the vertical grid device. The central ray enters the chest axially.
Fig. 2.49  Lordotic radiographic position of chest results in AP axial projection. Central ray is not angled; however, it enters chest axially as a result of body position.
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Fig. 2.50  Abduction and adduction of arm.

A patient is standing upright with his right arm extended to his side. An arrow pointing up indicates the movement of the arm from the central axis of the body or body part. An arrow pointing down indicates the movement of the arm toward the central axis of the body or body part.

A patient is standing upright with the palmar surface of his hand facing front. An arrow pointing up indicates the straightening of a joint. An arrow pointing down indicates bending a joint.
Fig. 2.51  Extension of arm (anatomic position) and flexion (bending).
The first diagram shows the vertebrae bent towards the left. The second diagram shows the vertebrae in a straight position. The third diagram shows the vertebrae bent towards the right.
Fig. 2.52  Hyperextension, extension, and hyperflexion of neck.

Body Movement Terminology

The following terms are used to describe movement related to the limbs. These terms are often used in positioning descriptions and in the patient history provided to the radiographer by the referring physician. They must be studied thoroughly.
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Fig. 2.54  Pronation and supination of forearm.

A man standing in an upright position is rotating the forearm so that the palm is down. It is indicated by an arrow pointing inwards. A man standing in an upright position is rotating the forearm so that the palm is up. It is indicated by an arrow pointing outside.

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Fig. 2.55  (A) Rotation of chest and abdomen. The patient’s arm and knee are flexed for comfort. (B) Medial rotation of left leg. (C) Lateral rotation of left leg.

(A) A patient is on the radiographic table by rotating the body around its axis. His knees and elbow are flexed. (B) A leg is rotated toward the midline of the body. It is indicated by an arrow. (C) A leg is rotated away from the midline of the body. It is indicated by an arrow.

A man standing in an upright position is moving his arm in a circular motion. It is indicated by two circular arrows.
Fig. 2.56  Circumduction of arm.
A skull is tilted 15 degrees from the long axis.
Fig. 2.57  Tilt of skull is 15 degrees from long axis.
A hand turned to its radial side is labeled radial deviation and a hand turned to its ulnar side is ulnar deviation.
Fig. 2.58  Radial deviation of hand (turned to radial side) and ulnar deviation (turned to ulnar side).
A foot bent towards the leg is labeled as dorsiflexion. A foot bent downward towards the sole is plantar flexion.
Fig. 2.59  Foot in dorsiflexion and plantar flexion. Note movement is at ankle joint.

TABLE 2.7

Greek and Latin nouns: common singular and plural forms
Singular Plural Examples: singular—plural
-a -ae maxilla—maxillae
-ex -ces apex—apices
-is -es diagnosis—diagnoses
-ix -ces appendix—appendices
-ma -mata fibroma—fibromata
-on -a ganglion—ganglia
-um -a antrum—antra
-us -i ramus—rami

TABLE 2.8

Frequently misused single and plural word forms
Singular Plural Singular Plural
adnexus adnexa mediastinum mediastina
alveolus alveoli medulla medullae
areola areolae meninx meninges
bronchus bronchi meniscus menisci
bursa bursae metastasis metastases
calculus calculi mucosa mucosae
coxa coxae omentum omenta
diagnosis diagnoses paralysis paralyses
diverticulum diverticula plexus plexi
fossa fossae pleura pleurae
gingiva gingivae pneumothorax pneumothoraces
haustrum haustra ramus rami
hilum hila ruga rugae
ilium ilia sulcus sulci
labium labia thrombus thrombi
lamina laminae vertebra vertebrae
lumen lumina viscus viscera

Medical Terminology

Single and plural word endings for common Greek and Latin nouns are presented in Table 2.7. Single and plural word forms are often confused. Examples of commonly misused word forms are listed in Table 2.8; the singular form generally is used when the plural form is intended.

Abbreviations used in Chapter 2

ARRT American Registry of Radiologic Technologists
ASIS Anterior superior iliac spine
CT Computed tomography
LAO Left anterior oblique
LLQ Left lower quadrant
LPO Left posterior oblique
LUQ Left upper quadrant
MRI Magnetic resonance imaging
RAO Right anterior oblique
RLQ Right lower quadrant
RPO Right posterior oblique
RUQ Right upper quadrant
US Ultrasound
See Addendum A for a summary of all abbreviations used in Volume 1.