Radiography OCR Part 1 PDF

2117 AM for the appearance of this image? The “L" marker (at top right) is in the correct location. The explanation appears in this chapter and the answer box is at the end of this chapter. The Normal Frontal Chest Radiograph « Fig. 2.1 displays some of th...

2117 AM for the appearance of this image? The “L" marker (at top right) is in the correct location. The explanation appears in this chapter and the answer box is at the end of this chapter. The Normal Frontal Chest Radiograph « Fig. 2.1 displays some of the normal anatomic features visible on the frontal chest radiograph. « Vessels and bronchi—normal lung markings « Virtually all of the branching white lines you see in the lungs on a chest radiograph are blood vessels. Blood vessels charac- teristiéélly branch and tapergradually from the hila to the per- iphery of the lung. You cannot accurately differentiate between pulmonary arteries and pulmonary veins on a conventional radiograph (Fig. 2.3).  217AM Coracoid process- scapula Medial border- scapula Pulmonary blood essels — Léft hilum- Left pulmonary artery Rght hilum- Right pulmonary artery Right Breast shadow FIG.2.1 Normal Landmarks on Frontal View of Chest.The spine is faintly visible through the heart shadow. Both the right and left lateral costophrenic angles (sulci) are sharply and acutely angled. The white line demarcates the approximate level of the minor or horizontal fissure that is usually visible on the frontal view. There is no minor fissure on the left side. The white circle contains lung markings that are blood vessels. Note that the left hilum is normally slightly higher than the right. The black numeral 3 lies on the posterior 3rd rib, and the white numeral 3 lies on the anterior 3rd rib.  2117 AM FIG.2.2 Technical adequacy of a chest x-ray. « Bronchi are mostly invisible on a normal chest radiograph be- cause they are normally very thin-walled, they contain air and are surrounded by air. Pleura: Normal Anatomy « The pleura is composed of two layers, the outer parietal and inner vis- ceral layer with the pleural space between them. The visceral pleura ls adherent to the lung and enfolds to form the major (obllque) and minor (horlzontal) fissures. « Normally there are several milliliters of fluid, but no air, in the pleural space on a conventional chest radiograph, except where the two layers of visceral pleura enfold to form the fissures. Even then, they are usually no thicker than a line you could draw with the point of a sharpened pencil (Fig. 2.4).  2:17AM e o FIG.2.3 Normal Pulmonary Vasculature.The right lung is shown. In the upright position, the lower lobe vessels (black circle) should be larger in size (not number) than the upper lobe vessels (white circle) and all vessels taper gradually from central to peripheral (arrow). Alterations in pulmonary flow or pressure may change these relationships.  2117AM Visceral pleura lining fissure Costophrenic angle FIG.2.4 Diagram of Pleural Space.The visceral pleura is attached to the lung and folds upon itself to form the fissures. A very small amount of fluid is present in the pleural space between the visceral and parietal pleurae. The parietal pleura lines the inner chest wall but is not normally attached to it. The lateral costophrenic angle is a sharp, deep sulcus present on both the right and left side.  217 AM Normal Pulmonary Vasculature ) | Important Points «In the uprlght posltlon, the blood flow to the bases is normally greater than the flow to the apmes because of the effect of gravrty. Therefore, the vessels at the base are normally larger in sue than the vessels at the apex of the lung « Changes in pressure or flow can alter the normal dynamics of the pul- monary vasculature, some of which are described in Chapter 11. « Online extra: For more on recognizing normal pulmonary vascu- lature and an imaging approach to diagnosing heart disease in adults from the chest x-ray, see e-Appendix B. The ABCs of Heart Disease. The Normal Lateral Chest Radiograph (FIG. 2.5) « As part of the standard two-view chest examination, patients usually have an upright, frontal chest radiograph and an upright, left lat- eral view of the chest. A left lateral chest x-ray (the patient’s left side is against the detector) is of great diagnostic value but is some- times ignored by beginners because of their lack of familiarity with the findings visible in that projection (Box 2.1, Fig. 2.5).  2117AM FIG. 2.5 Normal Left Lateral Chest Radiograph.Th;r;: is a clear space behind the sternum (solid white arrow). The hila produce no discrete shadow (white circle). The vertebral bodies are approximately of equal hgig_ht_anfl their end plates are parallel to each other (double white arrows). The posterior costophrenic angles (solid black arrow) are sharp. Notice how the thoracic spine appears to become blacker (darker) from the shoulder girdle (asterisk)to the diaphragm because thereis less dense tissue for the x-ray beam to traverse at the level of the diaphragm. The superior surface of the right hemidia- phragm is frequently seen continuously from back to front (dashed black arrow) because it is not obscured by the heart, whereas the heart normally touches the anterior aspect of the left hemidiaphragm and obscures  2117AM (silhouettes) it. Notice the normal space posterior to the heart and anterior to the spine; this will be important in assessing cardiomegaly (see Chapter 11). The black line represents the approximate location of the major fissure; the white line is the approximate location of the minor fissure. Both are frequently visible on the lateral view. BOX 2.1 Why Look at the Lateral Chest? I « It can help you define the location of disease you already identified as being present on the frontal image. « It can confirm the presence of disease you may be unsure of on the basis of the frontal image alone, such as a mass or pneumonia. « It can demonstrate the existence of disease not visible on the frontal image (Fig. 2.6).  2:117AM FIG.2.6 The Spine Sign.Frontal (A) and lateral (B) views of the chest demonstrate airspace disease on the lateral image (B) in the left lower lobe that may not be immediately apparent on the frontal image (look closely at (A) and you may see the pneumonia in the left lower lobe behind the heart). Normally, the thoracic spine appears to get “blacker” as you view it from the neck to the diaphragm (see Fig. 2.5). In this case a left lower lobe pneumonia superimposed on the lower spine in the lateral view (arrow) makes the spine appear “whiter” (more dense) just above the diaphragm. This is called the s;lm?b‘;.  2117AM FIG.2.7 Anterior Mediastinal Adenopathy.(A) A normal lateral view shows a clear space behind the sternum —the retrosternal clear space (arrow). (B) Left lateral view of the chest demonstrates a soft tissue density that is filling-in this space behind the sternum (arrow). This represents anterior mediastinal lymphadenopathy in a patient with lymphoma. Adenopathy is probably the most frequent reason the retrosternal clear space is obscured. Thymoma, teratoma, and substernal thyroid enlargement also can produce anterior mediastinal masses but do not usually produce exactly this appearance. Five Key Areas on the Lateral Chest X-Ray (See Fig. 2.5) The Retrosternal Clear Space « Look for the normal lucency behind the upper sternum to “fill-in” with soft tissue density when there is an anterior mediastinal mass present (Fig. 2.7). Diagnostic Pitfalls « Be careful not to mistake the soft tissue of the patient’s superimposed arms for “filling-in” of the retrosternal clear space. Although patients are asked to hold their arms over their head for a lateral chest expos- ure, many are too weak to raise their arms. « To avoid this pitfall, you should be able to identify the location of the patient’s arm by identifying the humerus (Fig. 2.8).  2117 AM FIG.2.8 Arms Obscure Retrosternal Clear Space.ln this example, the patient was not able to hold her arms over her head for the lateral chest examination, as patients are instructed to do in order to eliminate the shadows of the arms from overlapping the lateral chest. The humeri are clearly visible (white arrows) so even though the soft tissue of the patient’s arms appears to fill-in the retrosternal clear space (black arrows), this should not be mistaken for an abnormality such as anterior mediastinal adenopathy (see Fig. 2.7).  217 AM “RUL bronchus Posterior wall bronchus intermedil.g. Right hilar vessels * LUL bronchus - FIG. 2‘.9 Normal Hilar Structures.Left later;l chest x-ray shows the major normal hilar structures. The right pulmonary artery produces an opacity anterior to the distal trachea (T). Normally, only aerated lung is seen posterior to the bronchus intermedius. LUL, Left upper lobe; RUL, right upper lobe. The Hilar Region « The hila may be difficult to assess on the frontal view, especially if both hila are slightly enlarged since comparison with the opposite normal side is impossible. The lateral view may help. Most of the normal hilar densities are made up of the pulmonary arteries. No discrete mass should be visible in the hilar region on the lateral view (Fig. 2.9).  217 AM FIG.2.10 Hilar Mass on Lateral Radiograph.This left lateral view of the chest shows multiple, lobulated soft tissue masses in the region of the hila (arrows). Compare this to the normal hilum in Fig. 2.9. This pa- tient had bilateral hilar adenopathy from sarcoidosis, but any cause of hilar adenopathy or a primary tumor in the hilum might have a similar appearance. « When thereis a h hilar lymph nodes, soft tissue shadow onthe lateral radiograph (Fig. 2.10). The Fissures « On the lateral projection, both the major and minor fissures may be visible as smooth, fine, white lines. The fissures demarcate the upper and lower lobes on the left and the upper, middle, and lower lobes on the right. « Because of the oblique plane of the major fissure, only the right-sided minor fissure is usually visible on the frontal view.  217 AM « The major fissures course obliquely, roughly from the level of the fifth thoracic vertebra to a point on the diaphragmatic surface of the pleura a few centimeters behind the sternum. « The minor fissure lies in a plane roughly at the level of the 4th anterior rib (on the right side only) and is horizontally oriented (see Fig. 2.5). « When a fissure contains fluid or develops fibrosis from a chronic pro- cess, it will become thickened (Fig. 2.11). Thickening of the fissure by fluid is almost always associated with other signs of fluid in the chest such as Kerley B lines and pleural effusions (see Chapter 11). Thickening of the fissure by fibrosis is the more likely cause if there are no other signs of fluid in the chest. The Thoracic Spine « Normally, the thoracic vertebral bodies are roughly rectangular in shape and each vertebral body’s endplate parallels the endplate of the vertebral body above and below it. Each intervertebral disk space remains the same or slightly greater in height as the one above it throughout the thoracic spine.  2117 AM FIG.2.11 Fluid in the Major Fissures.Left lateral view of the chest shows thickening of both the right and left major fissures (arrows). This patient was in congestive heart failure and this thickening represents fluid in the fissures. Normally, the fissures are either invisible or, if visible, they are fine, white lines of uniform thickness no thicker than a line made with the point of a sharpened pencil. The major fissure usually courses from the level of the 5th thoracic vertebral body to a point on the anterior diaphragm about 2 cm behind the sternum. Notice the increased interstitial markings that are visible throughout the lungs and are due to abnormal fluid in the interstitium of the lung.  2118AM and Degenerative Disk Disease.Normally, the thoracic vertebral bodies are roughly rectangular in shape (dashed white arrow). In this study, there is loss of stature of the 8th thoracic vertebral body due to osteoporosis (black arrow). Compression fractures frequently involve the superior endplate of the vertebral body first. There are small osteophytes present at multiple levels from degenerative disk disease (solid white arrows). « Degeneration of the disk can lead to narrowing of the disk space and the development of small, bony spurs (osteophytes) at the margins of the vertebral bodies. « When there is a compression fracture, most often from osteoporosis, the vertebral body loses height. Compression fractures very com- monly first involve depression of the superior endplate of the verte- bral body (Fig. 2.12). « Don't forget to look at the thoracic spine when studying the lateral chest radiograph for valuable clues about systemic disorders (see Chapter 22).  2118AM The Diaphragm « Because the diaphragm is composed of soft tissue (muscle) and the abdomen below it contains soft tissue structures like the liver and spleen, only the upper border of the diaphragm, abutting the air- filled lung, is usually visible on conventional radiographs. « Even though we have one diaphragm that separates the thorax from the abdomen, we do not normally see the entire diaphragm from the left-to-right side on conventional radiographs because of the position of the heart in the center of the chest. Therefore, radiographically we refer to the right-half of the diaphragm as the right hemidiaphragm and the left-half of the diaphragm as the left hemidiaphragm. ) | Important Points + How to tell the right from the left hemidiaphragm on the lateral radiograph: « The right hemidiaphragm is usually visible for its entire length from front to back. Normally, the right hemidiaphragm is slightly higher than the left, a relationship that tends to hold true on the lateral radiograph as well as the frontal. « The left hemidiaphragm is seen sharply posteriorly but is silhouet- ted by the muscle of the heart anteriorly (i.e., its edge disappears anteriorly because the heart and the diaphragm are both soft tis- sue density) (see Fig. 2.5). « Air in the stomach or splenic flexure of the colon appears immedi- ately below the left hemidiaphragm. The liver lies below the right hemidiaphragm and bowel gas is usually not seen between the liver and the right hemidiaphragm. The Posterior Costophrenic Angles (Posterior Costophrenic Sulci) « Each hemidiaphragm produces a rounded dome that indents the central portion of the base of each lung, like the bottom of a wine bottle. This produces a depression or sulcus that surrounds the base of each lung and represents the lowest point of the pleural space when the patient is upright.  218AM « On a frontal chest radiograph, this sulcus is most easily viewed at the outer edge of the lung as the lateral costophrenic sulcus (also called the lateral costophrenic angle) and on the lateral radiograph as the posterior costophrenic sulcus (also known as the posterior costo- phrenic angle ) (see Figs. 2.1 and 2.5). « Normally, the costophrenic sulci are sharply outlined and acutely angled. « Pleural effusions accumulate in the deep recesses of the costophrenic sulci with the patient upright, filling-in their acute angles. This is called blunting of the costophrenic angles (see Chapter 7). « It requires only about 75 mL of fluid (or less)to blunt the posterior :ostophreilic angle on the lateral projectio while it takes about y blunt the lateral c phrenic angles on the frontal projecti Normal CT Anatomy of the Chest « By convention, CT scans of the chest, like most other radiologic studies, are viewed with the patient’s right on your left and the patient’s left on your right. If the patient is scanned in the supine position, as most usually are, the top of each image is anterior and the bottom of each image is posterior unless marked otherwise (Fig. 2.13). (S FIG.2.13 CT Axial (A), Coronal (B), and Sagittal Views (C) of the Thorax.The three standard planes for imaging the thorax are shown (see Fig. 1.6). Remember that this data was all acquired at the time of the same scanning session but volume acquisition allows digital reformat- ting in any plane. The left main bronchus (black arrow) and the right main bronchus (white arrow) are seen in (A). Ao, Aorta; LA, left atrium; LV, left ventricle; PA, pulmonary artery; R, right; RA, right atrium; S, superior vena cava.  2:18AM » Important Points « Chest CT scans are usually windowed and displayed in at least two formats designed to be viewed as parts of the same study, in order to optimize anatomic definition. « Lung windows are chosen to maximize our ability to image abnormal- ities of the lung parenchyma and to identify normal and abnormal bronchial anatomy. The mediastinal structures frequently appear as a homogenous white density on lung windows. « Mediastinal windows are chosen to display the mediastinal, hilar, and pleural structures to best advantage. The lungs usually appear com- pletely black when viewed with mediastinal windows. « Bone windows are also often used as a third way of displaying the data, demonstrating the bony structures to their best advantage. « It is important to know that the displays of these different windows are manipulations of the data obtained during the original scan and do not require re-scanning the patient (see Fig. 1.5). Normal CT Anatomy of the Lungs « CT scans of the lungs reveal additional and more detailed anatomy than conventional radiographs. With computer reconstruction of thin-section CT images, the lungs can be visualized in any plane, although the three most common planes are the axial, sagittal, and coronal (see Fig. 2.13; Fig. 1.6). « Blood vessels are visible for almost their entire course from hilum to pleural surface. Pulmonary arteries can be differentiated from pul- monary veins (Fig. 2.14, Video 2.1). « The trachea is usually oval in shape and about 2 cm in diameter. « In most people, there is a space present just underneath the arch of the aorta but above the pulmonary artery called the aortopulmon- ary window (Fig. 2.16). The aortopulmonary window is an important landmark because it is a favorite location for enlarged lymph nodes  2118AM to Egneag; At or slightly below this level, the trachea bifurcates at the carina into the right and left main bronchi (Fig. 2.17). FIG.2.14 MIP of Pulmonary Vasculature. MIP (or MIPs if pleural) stands for maximum intensity projection and is a way to display certain structures of a given density preferentially making them stand- out more easily. It is a computer post-processing manipulation of the same data acquired at the time of the original scan. It produces an image that looks like an angiogram and is used particularly for CT-angiography (as here) and is also utilized for finding pulmonary nodules (see Video 2.1).  2118AM FIG.2.15 Bronchus-Artery Relationship.The normal relationship between the pulmonary artery (dashed arrow) and its accompanying bronchus (solid arrow) is that the artery is usually larger than the bronchus. In bronchiectasis, that relationship is reversed with the bronchus becoming larger than the artery (see Chapter 10).  2118AM F 8| I Trachea \L ] Ascending i Left main aorta bronchus Right main bronchus RPA Descending aorta FIG.2.16 Aortopulmonary Window (Space).The aortopulmonary (aortic-pulmonary) window (AP window) is a mediastinal space important in imaging because it is a common site of lymphadenopathy. It is bound superiorly by the aortic arch, inferiorly by the left pulmonary artery (LPA), medially by the trachea, and laterally by the left lung. Don’t confuse the name for this space with the very rare congentital heart disesase, also called an aortopulmonary window. RPA, Right pulmonary artery.  2:18AM 2.17 Coronal and Axial CT at Carina.(A) The trachea (T) bifurcates at the carina (C) into the right main bronchus (RMB) and left main bronchus (LMB). After the origin of the right upper lobe bronchus (dashed white arrow), the bronchus intermedius (BI) gives rise to the right lower lobe bronchus (dashed black arrow) and middle lobe bronchus (not shown). The left upper lobe bronchus is shown by the solid black arrow. The solid white arrow points to the aortopulmonary window (see Fig. 2.16). (B) Just distal to the carina, the right main bronchus (RMB) gives rise to the upper lobe bronchus (white arrow). The left main bronchus (LMB) is also seen at this level.  218AM FIG.2.18 Bronchus Intermedius.Distal to the origin of the right upper lobe bronchus is the short bronchial section called the bronchus intermedius (solid black arrow). The bronchus intermedius divides into the middle and lower lobe bronchi more caudal to this image. There is normally only lung tissue posterior to the bronchus intermedius (white arrow): soft tissue in this location wouldbe suspicious for a tumor or adenopathy. The left main bronchus is shown by the dashed black arrow. « Slightly more inferior are the right and left main bronchi and the bronchus intermedius. The right main bronchus will appear as a circular, air-containing structure that will then become tubular as the right upper lobe bronchus comes into view. Only aerated lung should be seen posterior to the bronchus intermedius. The left main bronchus will appear as an air-containing circular structure on the left (Fig. 2.18). The Fissures « Depending on slice thickness, the fissures will be visible either as thin white lines or by an avascular band up to 2 cm thick as they travel obliquely through the lungs (Fig. 2.19). 2118AM