Approach to Chest X-Ray and CT, Dr. Zagurovskaya

Supine X-ray technique

Imagining plate is under the patient.

Causes for Opacities

-Air space consolidation -Atelectasias (loss of air space) -Summation of shadows -Chest wall soft tissues -Pleural Effusion

Loculated Lucency

Think pneumothorax or bulla.

Chest X Ray in CF

-Bronchial inflammation and bronchiectasis -Hyper inflated lungs -Bilateral reticular opacities corresponding to thickened distal airways and bronchiectasis

Radiation and Pregnancy

-Controversial. -V/Q scan potentially results in higher fetal radiation exposure. -CT PA believed to cause less radiation exposure. -*Elevated D Dimer is NORMAL IN 2ND AND THIRD TRIMESTER, thus is not an indication for a CTPA*

Cervicothoracic Sign

-Differentiates anterior from posterior lesions of superior mediastinum. -Anterior mediastinum ends at clavicle. If a lesion extends beyond this point, it must be a lesion of a more posterior structure. (i.e. apical segments of upper lobes, pleura, or posterior mediastinum).

Proper upright PA X-ray technique

-Extended chin, hands on waist, shoulders rolled forward and downward. -Deep inspiration. -Both apices are seen, clavicles are equal distance from spinous processes, scapulae out of the way, spine visible through heart, 8-10 ribs visible, both costophrenic angles visible.

CXR of emphysema

-Hyperinflation -Flattened diaphragm -Attenuated pulmonary markings -Teardrop heart -Increased retrosternal clear space on lateral view

Hilum Overlay Sign

-Indicates an anterior or posterior mediastinal lesion. -Circumscribed opacity with incomplete medial border is extraparenchymal. -If lesion arises from hilum, it would null the borders.

Causes of cystic lung disease

-Langerhans cell histiocytosis -Lymphangioleiomyomatosis -Pneumatoceles -Lymphocytic interstitial pneumonia

Lateral View X-Ray

-Left side of chest is placed as close to the plate as possible to minimize any magnification artifacts. -From this angle keep in mind the relative anatomy of the heart chambers (Right heart more superior, ventricles more anterior).

Empyema

-Lenticular collection of pleural fluid. -Air fluid level exhibits length disparity between PA and lateral views. -Forms obtuse angles along interface with adjacent pleura. -Smooth enhancing walls on CT.

3 signature radiographic characteristics of interstitial lung disease on radiograph

-Made up of lines (reticular pattern)(left) -made up of dots (nodular pattern)(middle) -Made up of both (reticulonodular pattern)(right)

Radiation Dose

-Measured in mSv (millisievert). -Public dose; 1mSv/year, not above 5. -Radiation workers; 20mSv/year, not to exceed 50. -CXR; .1mSv -Chest CT; 7mSv -CTA Coronary; 5-12mSv

Causes of chronic consolidation

-Neoplasm -Sarcoidosis -Organizing pneumonia -Eosinophilic pneumonia -Alveolar proteinosis

How do pathologies present on chest X-rays?

-Opacities -Lucency -Loss of border/interface (silhouette sign) -Density

Decubitus View

-Patient lying on their side. -Pulmonary effusion; suspect side on the bottom to allow fluid to fall and collect. -Pneumothorax; suspect side on top to allow gas to rise and collect.

Swyer-James-MacLeod Syndrome

-Post-infective obliterative bronchiolitis. (internet) -Caused by incomplete development of the alveolar buds as a result of damage to the terminal and respiratory bronchioles, usually due to viral lower respiratory tract infection in infancy or early childhood. (PPT)

Most common causes of unilateral diffuse increase in parenchymal lucency

-Prior unilateral lung transplant -Swyer-James-MacLeod syndrome -Pulmonary Artery hypoplasia/aplasia

Meniscus Sign in Pleural Effusion

-Pseudo meniscus can be seen in chronic pleural thickening. -Loss of downward angle of costodiaphragmatic sulcus. Downward angle is replaced with an upward angle resembling a meniscus.

Causes of acute consolidation

-Pulmonary edema -Pneumonia -Aspiration -Hemorrhage/contusion -Infarction

Causes of Fine Nodular Lung Disease

-Sarcoidosis -Metastasis -TB

Silhouette Sign

-The loss of a border or interface between two structures. -Due to a pathology that causes a structure to change attenuation, thus blurring the border/interface between structures. -Image; loss of left heart and diaphragm on PA

Anatomy checklist for chest x ray

-Tracheobronchial Tree -Cardiomediastinal contours -Hila -Lungs and interstitial markings -Pleura and Chest wall -Diaphragm

Oblique Radiograph

-Used in emergent situations. -Source and plate obliqued in such a way as to focus on a particular area of the patient that is of concern.

Lung Abscess

-no significant change in shape and length of air fluid level between frontal and lateral views. -CT; acute angles with lungs. -Irregular walls.

Possible causes for air space consolidation

-pus/infection -blood -neoplastic cells -fluid/edema

DDX For abnormal hila

-vascular issues -primary tumor -lymphadenopathy

3 big question when seeing an opacity on chest xray

1) Is the volume of the affected lung preserved? 2) Are the borders well or ill defined? 3) Does the opacity extend beyond the lungs?

Check list for reading a chest x ray

1) Patient data 2) Image technical data and quality 3) Obvious abnormalities (Example; theres a shark in the lung) 4) Systematic check of anatomy (Dr. Ayoob suggests starting at trachea and other central structures and moving out). 5) Support hardware 6) Second look at hidden areas 6) Consider clinical question/scenario.

Causes of reticular pattern interstitial lung disease

1) edema; heart failure, fluid overload. 2) interstitial pneumonia; viral, PCP, mycoplasma 3) Lymphangitis 4) UIP; honeycombing, IPF, RA, systemic sclerosis, dermatomyositis 5) Drugs; nitrofurantoin, methotrexate, amiodarone, busulifan, bleomycin, cytoxan.

"Hidden areas" to check in chest xray

Apices Posterior sulcus Mediastinum Hila

Air Bronchogram

Bronchi appear dark on x ray. This is due to the fact that they are air filled, and the surrounding alveoli are becoming radio-opaque due to edema or other infiltrate.

Kerley B Lines

Caused by edema, interstitial inflammation/infection, lymphangetic carcinomatosis.

Lower lung predominant emphysema

Causes; -*alpha 1 antitrypsin deficiency* -*ritalin injection* -Aging -Bronchopulmonary dysplasia (common in pts of premature birth).

Radiation Dose Considerations

Children 7x more sensitive to radiation than adults. Girls more than boys. Be careful, don't image unless necessary.

Right Middle Lobe Consolidation

Cingular and RML opacities project over the heart on lateral chest x ray.

When is an expiratory view used?

Expiratory views are used in suspected pneumothorax patients. Expiration accentuates the pneumothorax visual characteristics. (Image; right x ray is expiratory)

Differentiating between a lesion of lung parenchyma vs surrounding structures

Lesions of surrounding structures that encroach into the lungs often have smooth borders with the structure they originate from. Example; the following image is of a diaphragmatic lesion that is swelling into the lung space.

What is the advantage of a PA image?

Little to no magnification artifact of the heart size.

DDX of middle mediastinal mass

Lymphadenopathy, aortic/arch vessels aneurysm, bronchial/esophageal congenital duplication cyst, pulmonary artery enlargement.

DDX Of anterior mediastinal mass

Lymphadenopathy, germ cell tumor, thyme/thyroid mass/enlargement, diaphragmatic hernia, pericardial cyst.

Large Bulla CXR

Mimics pneumothorax, but no acute dyspnea

DDX of Posterior mediastinal mass

Neurogenic tumor, hiatal or posterior diaphragmatic hernia, descending thoracic aortic aneurysm.

Spine Sign

Paradoxically increased density of lower spine in lateral x ray, often due to a lower lobe pneumonia or other opacity.

Loculated Pleural Effusion

Pleural effusion that occurs in the fissures or between the pleural layers.

Normal difference of height between diaphragms

Roughly 2cm.

Golden's S Sign

S shape caused by edge of minor fissure and hilar mass in RUL atelectasis.

Lordotic view

Slight upward angle on an AP chest Xray. Focuses on the apical regions of the lungs.

What is the disadvantage of an AP image?

The heart is father away from the imaging plate, thus magnifying it. It is easy to over-read cardiomegaly or other cardiac dilation into an AP image.

Bronchus Cut-Off Sign

abrupt truncation of a bronchus from obstruction, which may be due to cancer, mucous plugging, trauma or foreign bodies. Typically, there is associated distal lobar collapse.