Radiographic Anatomy of the Chest (Respiratory System) PDF

RADIOGRAPHIC ANATOMY OF THE CHEST (RESPIRATORY SYSTEM) DAPHNIE GRACE V. CHAVEZ, MHCA, RRT 2 Chest(thorax) -is the upper portion of trunk between the neck and abdomen. 3 BONY THORAX RESPIRATORY SYSTEM MEDIASTINUM 4 BONY THORAX -part of skeletal system...

RADIOGRAPHIC ANATOMY OF THE CHEST (RESPIRATORY SYSTEM) DAPHNIE GRACE V. CHAVEZ, MHCA, RRT 2 Chest(thorax) -is the upper portion of trunk between the neck and abdomen. 3 BONY THORAX RESPIRATORY SYSTEM MEDIASTINUM 4 BONY THORAX -part of skeletal system that provides framework for the parts of the chest involve with breathing and blood circulation. It consists of: 1. Sternum, anteriorly 2. 2 clavicles, superiorly 3. 12 pair of ribs 4. 12 thoracic vertebrae, posteriorly 5 THORACIC VISCERA - Used to described the parts of chest consisting of the lungs and the remaining thoracic organs contained in mediastinum. Mediastinum ▸ The mediastinum contains all thoracic organs except the lungs. ▸ The heart occupies a large portion of the mediastinum, and the shape of the heart varies with age, degree of respiration, and patient position. ▸ Other organs contained within the mediastinum include the thyroid and thymus glands and nervous and lymphatic tissues. 7 TOPOGRAPHIC POSITIONING LANDMARKS  “ ▸ VERTEBRA PROMINENS -AN important landmark for determining the CR location on PA chest projection. ▸ JUGULAR NOTCH -An important landmark for determining the CR placement on AP Chest Projections. ▸ Midthorax - -At the level of T7 “ “ “ “ Air is taken in via the upper airways: nasal cavity, pharynx larynx and through the lower airways Trachea Primary Bronchi Bronchial tree and into the small Bronchioles and Alveoli within the lung tissue. “ “ The lungs are divided into lobes; Left lung - is composed of the ff: upper lobe lower lobe lingula (a small remnant next to the apex of the heart) Right lung -is composed of the ff: ⮚ upper lobe ⮚ middle lobe ⮚ lower lobe ▸ ▸ “ Each branch of the bronchial tree eventually sub-divides to form very narrow terminal bronchioles, which terminate in the alveoli. There are many millions of alveloi in each lung, and these are the areas responsible for gaseous exchange, presenting a massive surface area for exchange to occur over. ▸ Each alveolus is very closely associated with a network of capillaries containing deoxygenated blood from the pulmonary artery. ⮚ “ ▸ Anatomically, the mediastinum is divided into the anterior, middle, and posterior portions. Anterior mediastinum contains: ❖ Thyroid and Thymus glands. ⮚ The middle mediastinum contains: ❖ The heart and great vessels ❖ Esophagus and trachea ⮚ The posterior mediastinum contains: ❖ The descending aorta and the spine. “ The anatomic bony structures of the thorax assist in both inspiration and expiration. These bony structures include the ribs, sternum, and thoracic vertebrae. “ “ Imaging Considerations Radiography ▸ The examination most frequently performed in any radiology department is chest radiography. Although this examination may seem routine, chest radiography provides important information about soft tissues, bones, the pleura, the mediastinum, and lung tissue.  “ Some sources describe pathologies including those in the chest, as: Additive - are harder than normal to penetrate Subtractive (Destructive)-they are easier than normal to penetrate. In the respiratory system, any condition that adds fluid or tissue to the normally aerated chest (e.g., pneumonia) requires an increase in technical factors to afford proper penetration and exposure. “ ▸ Any condition that increases the aeration of the chest (e.g., emphysema) reduces the amount of radiation required for proper exposure to be achieved. “ “ “ “ ▸ The kilovoltage range should be chosen based on the energy level necessary to penetrate the part of interest, keeping in mind the presence of additive or subtractive pathologies. “ ▸ Position and Projection Patient position and projection are also critical exposure conditions that may distort the final image. Position -refers to the arrangement of the patient’s body (e.g., erect, supine, recumbent) Projection - refers to the path of the x-ray beam (e.g., anteroposterior [AP], i.e., entering through the body’s anterior surface and exiting the posterior surface). “ The standard projections for chest radiography : Erect posteroanterior (PA) Left lateral. Each of these serves to place the heart closer to the film because the heart lies in the anterior part of the chest and mostly to the left side. When combined with a standard 72-inch source-to- image distance (SID), magnification of the heart is minimized. “ PA CHEST AP CHEST Chest Radiography On a normal erect PA chest image, the costophrenic and cardiophrenic angles are demonstrated, with the right hemidiaphragm appearing 1 to 2 cm higher than the left because of the position of the liver. When a patient is radiographed in the recumbent position, the lower lung fields may be obscured because of abdominal pressure raising the level of the diaphragm  Recumbent anteroposterior chest demonstrating obscuring of the lower lung fields.  Other projections of the thorax are used less frequently than the erect PA and left lateral projections. The AP projection is the method of choice for mobile radiography when the patient is too ill to tolerate a visit to the department and assume an erect position. As much as possible, it is important that mobile chest radiographs be taken with the patient sitting in bed in the erect position to demonstrate any air–fluid levels present. Maintenance of the beam perpendicular to the plane of the image receptor is essential to avoid any foreshortening of the heart. FIGURE 3-4 A, Normal appearance of chest on inspiration. B, Expiration film on the same patient demonstrates elevation of the diaphragm and a heart that is more transverse and appears larger. ▸ The lateral chest view examines the lungs, bony thoracic cavity, mediastinum, and great vessels. Lateral radiographs can be particularly useful in assessing the retrosternal and retrocardiac airspaces. Oblique projections of the thorax are useful in separating superimposed structures such as the sternum, esophagus, and thoracic spine.  A lordotic chest radiograph is useful in demonstrating the apical regions of the lung, which are normally obscured by bony structures on the standard PA projection (Fig. 3-5). Certain diseases such as tuberculosis (TB) have a predilection for the apices. FIGURE 3-5 Lordotic chest radiograph taken on expiration to demonstrate a possible pneumothorax.  In infants, the mediastinum appears wide because the thymus is normally large in a healthy infant. This radiographic appearance is readily visible on both PA and lateral views and is referred to as the “sail sign” because of its characteristic appearance (Fig. 3-11). Diagnosis is difficult because the width of the upper mediastinum varies greatly with the phase of respiration. A crying child may present an opportune moment for the technologist to make an exposure, but the resultant Valsalva maneuver adds to the distortion of the thymus. Valsalva maneuver - increases both the intrathoracic pressure and the intraabdominal pressure by asking the patient to inhale deeply and hold the breath to force the diaphragm and chest muscles against a closed glottis. FIGURE 3-11 Normal enlargement of the thymus in a 3- month-old infant demonstrates the “sail sign,” evidenced by the uniform density increase in the right upper lung area. The upright position is preferred for the following reasons: 1. It prevents engorgement (an excess of blood) of pulmonary vessels, whereas supine or recumbent positioning tends to increase engorgement of pulmonary vessels, which can change the radiographic appearance of these vessels and the lungs. 2. It allows full expansion of the lungs. In the recumbent position, full expansion of the lungs is prevented.. The upright position is very important in order to visualize possible air and fluid levels in the chest. 3. In the upright position, fluid will locate near the base of the lung while the air will rise. In the recumbent position, fluid will spread out over the posterior surface of the lung, resulting in a hazy appearance of the entire lung. 4. An upright chest film is preferred over an upright abdominal film for the diagnosis of pneumoperitoneum (free air in the abdominal cavity). ▸ Ask the patient to move the shoulders forward and downward, so that the chest wall and both shoulders are in contact with the cassette. This helps to carry the clavicles below the lung apices. Adjust the height of the cassette so that its upper border is about 2 inches above the shoulders so that the lung apices are not cut off. Ask the patient to extend the neck, chin, and head upward and vertical. The neck and chin otherwise tend to superimpose the trachea and uppermost lung regions. The patient's arms are placed overhead or on their hips with elbows angled anteriorly. This will rotate the scapulae off the chest, thereby preventing their superimposition over the lungs. In female patients with large pendulous breasts, it is very important to minimize breast shadows. *Ask the patient to pull the breasts upward and laterally (outwards), then remove her hands as she leans against the cassette holder to keep them 52 Rotation Even a small degree of rotation distorts the mediastinal borders, and the lung nearest the film will appear less translucent. The following points should be stressed to obtain a true PA view (without rotation): 54 Ensure that the patient is standing evenly on both feet. Both shoulders should be rolled forward and downward. The chest radiograph should be well centered so that the medial ends of the clavicle are equidistant from the vertebral spinous processes at T4/5. However, scoliosis and other thoracic deformities negate the value of conventional centering. 56 Respiration Be sure to make the exposure upon a second full inspiration by the patient. The patient should take as deep a breath as possible, and then hold it to fully aerate the lungs. Taking a second deep breath before holding it allows for a deeper inspiration, as more air is inhaled during the second breath than during the first breath. 57 The best way to determine the degree of inspiration is to start at the top of the patient's rib cage. With rib number one, and count down to the tenth or eleventh rib posteriorly. A general rule for average adult patients is to show a minimum of 10 ribs on a good PA chest radiograph. Older patients have less inhalation capability, with a resulting low lung volume, which requires a higher central ray location. 58 Cardiothoracic ratio is a simple and cheap tool in the estimation of heart size. It is a useful index of cardiac size evaluation, and a value of 50% is generally considered to indicate the upper limit of normal. 59