Imaging techniques to examine the respiratory system

2021-07-03 10:34 AM

Pulmonary film has taken at the hospital bed because of the serious illness, unable to stand up, had to be taken lying down, of poor quality, only able to evaluate large lesions

Conventional lung film

Technical brief

Straight chest x-ray: The patient stands symmetrically upright, separates the shoulder blades from the ribcage, takes a deep breath, and holds breath. Distance between X-ray ball and film 1.5 m - 2m.

Left side lung angiogram: The patient stands on the left side close to the film. Always take left lateral radiographs (despite right lung injury) for two reasons: left-sided, the heart shadow is less likely to be magnified, and according to international consensus when reading magnetic resonance films.

Some additional postures in some cases:

Shoot forward or backward, right or left, multiple angles.

Take the lung apex position to see the lung apex lesions covered by the clavicle and ribs .

The patient was lying on the side, and the horizontal X-ray showed early effusion, mild pneumothorax.

Exhalation chest x-ray revealed mild pneumothorax, pulmonary distension.

Lung film quality standards

Straight lung film:

Completely straight: medial border of clavicle symmetric across the midline, anterior arch of rib 6 symmetric in children (Comparison of two distances from the medial border of the sixth rib to the lateral border of the thoracic wall).

Inhale deeply: anterior arch of ribs 6-7 on the diaphragmatic arch.

Stand upright and proportionate the level of fluid in the gastric sac, the shoulder blades separate from the ribcage.

Good contrast includes 3 criteria:

See blood vessels behind the heart, behind the liver.

Visible blood vessels up to about 1.5 cm (1 - 2 cm) from the periphery.

Can see 3-4 upper thoracic vertebrae, guess the remaining thoracic vertebrae.

Pulmonary film has taken at the hospital bed because of the serious illness, unable to stand up, had to be taken lying down, poor quality, can only evaluate large lesions. Therefore, when the patient's condition allows, the standing lung should be taken again.

Tilt lung film:

Completely tilted: the posterior ribs on both sides are almost overlapping, the sternum is completely tilted (visible sternum martial).

Inhale deeply: posterior diaphragmatic rib angle is bright, diaphragmatic arch below the anterior arch of rib 6.

Figure: Diagram of bronchioles.

The sequence of reading lung film

Read straight lung films systematically in a 7-step spiral, avoiding thoracic lesions. Read on a film reading lamp with appropriate brightness.

Figure: The sequence of reading the lung film.
(1. apex; 2. axillary; 3. midline; 4. perihilar; 5. superior hilum; 6. paracardial; 7. basal region).

Step 1: procedure (name, patient number; right, left; date, place of scan)

Step 2: soft chest wall.

Step 3: diaphragm and the area below the diaphragm.

Step 4: thoracic bone.

Step 5: pleura.

Step 6: Lung parenchyma and hilum: compare the two sides.  

Step 7: mediastinum.

Figure: Division of the lesion on the lung film.        

Read the film of the inclined lung:


Heart-aorta-pulmonary artery.

Thoracic bones.

Interlobar grooves.



Spaces behind the heart, behind the sternum, after the trachea-anterior of the spine, the foramen thoracic spine

Notes on normal cardiopulmonary film

The shade of sternocleidomastoid muscle.

The blurred line on the collarbone.

Large pectoral muscle shadow.

Shaded female breasts and nipples.

The shading of the shoulder blades overlaps the lung field.

Cervical lymph node calcification, axillary lymph node calcification.

Shiny shadow of the suprasternal ridge.

Cervical rib: hypertrophy of the transverse trochanter of the C7 cervical vertebra.

Calcification of costal cartilage usually begins after the age of 30.

Fracture of the rib in two, deformity of the rib bridge.

Tracheal balloon and tracheobronchial light bulb.

Single lobe groove.

Small interlobular fissure in the right lung.

Double-barreled gun image: the image of a blood vessel and accompanying sub lobular bronchus, with parallel x-ray axis.

Fibrous bands from old lung damage.

Hilar lymph node calcification.

Primordial nodular calcification.

Thickening of the pleura: obtuse rib angle, flattened diaphragm.

Adhesive diaphragm: tent roof shape.

Bilateral diaphragmatic corner fat layer.

Shadow of inferior vena cava: obtuse right diaphragmatic angle.

When having the above images, it is still concluded that the images of the heart and lungs are normal.

Figure: Blood vessels in the hilum of the lungs.

Figure: The main groups of mediastinal ganglia.

The anatomical and functional unit of the lung

The normal Miller secondary lung lobes are not visible on plain radiographs, and some are seen on computed tomography (CT) scans of the lungs. The important chest radiographic syndromes such as pneumococcal syndrome, interstitial syndrome... are related to abnormalities in the secondary lobules. Each anatomical region of the secondary lobules may be the source of the findings, often seen on plain chest radiographs or on CT scans.

The secondary lobules make up the lung segments.

The Miller secondary lobe is the smallest anatomical unit of the lung surrounded by a connective septum. Polygonal cone at the base of the pleura, apex toward the hilum. The base of the lobules is polygonal, 1-2.5cm in diameter.

The septum of the lobules is the linear organization, which is the associative organization. In this septum, there are pulmonary and lymphatic venules.

The axis of the lobules is the central lobular bronchiole, accompanied by the central lobular artery. Central lobular bronchioles divide into 3 to 5 terminal bronchioles, which carry air to the alveoli. Each secondary lobe has 3 to 5 alveoli. The alveoli are the functional units of the lungs.

Each terminal bronchiole divides into many respiratory bronchioles, which also contain alveolar cells that participate in gas exchange. The respiratory bronchioles divide into alveolar ducts and then the alveolar sacs are composed of pneumocytes. The primary lobules are part of the lung parenchyma from the alveolar ducts.

The lobular arterioles accompany the bronchioles, this parallel division starting from the segmental artery, which shares the same name and diameter as the bronchi.



Figure: Miller secondary pulmonary lobe.

Locating the lung, lung segment

On a straight lung film, the projections of lobes and lobes overlap, on the inclined film the plane of the interlobar fissures or the boundaries of the segments are nearly parallel to the x-ray beam, so it is easy to locate.

The right lung has 2 interlobular grooves, 3 lobes, and 10 lobes.

Figure: Locating right lung segment.

Figure: Locating left lung segment.

The left lung has 1 interlobular groove, 2 lobes, and 9 lobes.

Right lung:

Upper lobe:

Parietal lobe = PT 1.

Anterior segment = PT 2.

Posterior segment = PT 3.

Middle lobe:

Posterior lateral segment = PT 4.

Medial anterior segment = PT 5.

Lower lobe:

Fowler segment = PT 6.

Paracardiac segment = PT 7.

Anterior basal segment = PT 8.

Baseline segmentation = PT 9.

Posterior segment = PT10.

Left lung:

Upper lobe:

Parietal lobe = PT 1.

Anterior segment = PT 2.

Posterior segment = PT 3.

Upper segment = PT 4.

Lower segment = PT 5.

Lower lobe:

Fowler segment = PT 6.

Anterior basal segment = PT 8.

Baseline segmentation = PT 9.

Posterior segment = PT 10.

Note: There are some slight differences in the segmentation, mediastinal division, and names of mediastinal ganglion groups among authors.

Figure: Locating lung segments on computed tomography (MF; interlobar fissure).

Basic visual cues

Shadow sign:

Two parts have the same density, if the same plane, the boundary of each other cannot be seen, for example:

The anterior left diaphragm has the same density and is in the same plane as the heart, so it is removed.

Obliteration of the right lower arch of the heart when there is the opacity of middle lobe pulmonary consolidation.

Clear mediastinal lines when lesions are in the same plane.

Figure: Shadow overlap sign: A - middle lobe opacity, B - a focal pleural effusion.

Chest signs:

Mediastinal opacity, if the superior border above the clavicle is indistinct, is in the anterior mediastinum because it is in the same plane (Ì£continuous) as the cervical stroma; Conversely, if the superior border of the mediastinal opacity above the clavicle is evident, it is in the posterior mediastinum because it is surrounded by air of the apical lung parenchyma.

Figure: Cervical sign: A - posterior mediastinal opacity, B - anterior mediastinal opacity. 

Chest signs:

The shading at the base of the lung, if there is a sharp lower border on the background of the abdominal opacity, is from the lung, surrounded by air; If the lower border of this shading is removed, it is from the abdomen, which is bounded by the soft part of the abdomen.

Figure: Thoracic and abdominal signs: A – shading in the thorax, B shading in the abdomen.

Tangent signs:

The margin of an organ or lesion is visible when its attenuation is different from that of the surrounding environment and when its edge is tangent to the X-ray beam. For example, the opacity of the breast or the opacity of the nipple has a distinct lower border. sharpness if the lower limit is a plane parallel to the x-ray beam.

Golden S sign or reversed S sign:

Lobar atelectasis gives a shady image, with a sharp and concave proximal margin against the interlobar fissure. If this border has a convex segment showing an inverted S image, this convex segment corresponds to a bronchial tumor causing atelectasis. The chord of this convex segment is approximately equal to the tumor diameter. This sign can be seen at many sites of atelectasis, on conventional lung radiographs as well as on computed tomography.

Signs of hilar convergence:

Hilar enlargement may be caused by pulmonary artery dilatation or by parahilar tumors (eg, lymph nodes). If the blood vessels stop at the border or within the shadow border of the hilum no more than 1cm, then the hilar enlargement is due to pulmonary artery dilatation; Conversely, if the blood vessels enter the hilar shadow more than 1cm, the large hilar is due to a tumor next to the hilum.

Signs of hilar coverage:

The shadow of the mediastinum, if the hilum stops at the border or goes inwards no more than 1cm from the border, it is due to the large cardiac shadow; If the hilum goes in more than 1cm of the border, this shadow is due to a mediastinal tumor.

Figure: Signs of hilar convergence.

Mediastinal lines on straight lung film:

Several structures of the mediastinum have pulmonary-pleural imprints. If the following two conditions are met, this impression will produce a mediastinal opacity, which is the border of the structure that makes the impression: - a sudden change in density: the air density of the lung and the fluid density of the lung. structure.

Figure: The structural edge is tangent to the X-ray beam.

Anterior mediastinal tract (1).

Posterior mediastinal line (2).

Single ravenous line (3).

Upper vascular lines (4) (5).

Para-aortic line (6).

Left paravertebral line (7).

Paraoesophageal line (8).

Parasite inferior vena cava (9).

The image is too bright:

Diffuse or localized. The ball is round or luminescent.      

Shaded image:

Blurred line, blurred ice, shore. Round shape. Triangular shape.

Distribution: Diffuse, Scattered, Localized: lobed, segmented.

Border: clear, irregular, blurred.

Agree or disagree.

Change the image: according to the posture, according to the breathing in, out.

Horizontal upper border: slightly shifted level.

Figure: Description of the shaded image (left) and common cave shapes (right).


Ultrasound is a simple, low-cost, non-radioactive technique. SI is not transmitted by gas, so its role is very limited in the examination of the respiratory system. After conventional chest radiograph, additional SI may be indicated in a few cases in pleural, diaphragmatic, mediastinal pathology.

Ultrasound plays an important role in the cardiac examination.


Fan-type ultrasonic transducers have a frequency of 3.5 MHz, supplemented with a high-frequency straight-line type 5;7;10 MHz. The patient lies on his back, the ultrasound scan direction is from below the diaphragm, through the liver parenchyma, through the spleen parenchyma. Sitting position, transverse intercostal ultrasound to puncture pleural fluid.

Transsternal ultrasonography can show large arteries and veins at the base of the neck.

Pleural disease

Pleural effusion:

Ultrasound detection of pleural fluid is very sensitive, especially on the right side. The fluid has a hollow-sounding image on the hyperechoic diaphragm. When the amount of fluid is small, the fluid will gather at the costal angle of the diaphragm. When the volume of fluid is high, the lower lobe of the lung can be seen moving in the fluid.

Ultrasound also plays a role in distinguishing pleural fluid and pleural thickening in some cases that are difficult to distinguish on conventional lung films.

The pleural effusion was localized in many places, and we found some locations of effusion close to the chest wall and guided aspiration.

Solid pleural injury:

Thickening of the pleura will not show signs of pleural slip and is not as sensitive as conventional lung films or computed tomography films.

Pleural tumor shows thickened pleural nodule, often associated with pleural effusion.

Lung disease

Tumor or dense mass of the lung close to the chest wall, which can be seen on ultrasound if not separated by air in the lung, sometimes helps biopsy the lesion under ultrasound guidance.

Mediastinal disease

The lower mediastinum is easiest to see large lymph nodes, pleural-pericardial cysts can be seen...

The upper mediastinum is difficult to see thyroid nodules can be seen, and large blood vessels are abnormal.

The mediastinum is not visible except in children. Intraesophageally probe (7.5 MHz) visualizes the esophageal wall, surrounding mediastinal components, left atrium, and aorta.

Diaphragm disease

Ultrasound shows diaphragmatic movement with breathing. The diagnosis was made of hernia and diaphragmatic fistula when the abdominal contents were seen in the thorax. Diagnosed diaphragmatic tumor.

Computerized tomography Scan

Computed tomography (CT) is a technique that has become irreplaceable in the diagnosis of lung disease. Thick and thin cut layers depending on the pathology and structure to be studied can be from 1 to 10mm. The lung parenchyma is located in the density region about - 800 UH, mediastinum or soft, localized in the mean density of the mediastinal and chest wall structures, about 0 - 40 HU.

Some densities of structures in the thoracic cavity

Gas: ≤ - 100 H.

Lungs < - 750 H and > - 850 H.

Grease > - 100 H and < - 10 H.

Shift > -10 H and < 30 H.

Solid structure > 20 H and < 70 H.

Cartilage > 60 H and < 150 H.

Solid bone > 100 H.

Intravenous contrast injection in computed tomography must have the same preparation as an angiogram. For contrast intolerance reactions: it is necessary to consider risk factors, equip facilities at the computerized tomography room for prevention and initial management.

Magnetic resonance imaging

Magnetic resonance imaging is a harmless technique, if contraindications are observed for patients with pacemakers, intraocular metal foreign bodies, intracranial metal surgical clips, or blood vessels. The technique cannot be performed for patients who are afraid of solitude who must lie down in the tunnel for a long time, or for children who are not allowed to sleep. Components of the mediastinum such as the heart and blood vessels are very well analyzed in the multi-directional plane. Normal lung parenchyma does not give a magnetic resonance signal, so it is not investigated on magnetic resonance.