Approach to chest radiographs and computed tomography Flashcards
Suggested order of interpreting chest radiograph
- Technique
- Written data
- Chest wall/soft tissues
- Abdomen
- Diaphragm
- Pleura
- Heart
- Mediastinum
- Hila
- Lung parenchyma
Technical factors to look for
1) Rotation
2) Inspiration
3) Exposure
Rotation
Spinous processes should
project midway between
medial heads of clavicles
-i.e. clavicles are equidistant from the spinous processes
Inspiration
Dome of right hemidiaphragm projects over the anterior 6th /7th interspace and posterior right 10th interspace
Exposure
The lower thoracic disc spaces should be seen through the cardiac silhouette , and left diaphragm (i.e. disk spaces seen behind heart but should not see bony details of the spine + should visualize the left diaphragm)
When are posterior ribs more apparent
-on PA film (anterior ribs less visible on this film)
How many posterior ribs are visible
-up to 10 visible ribs on full inspiration
Importance of proper inspiration
-poor inspiration results in simulation of an enlarged heart and increased density of lower lobes
Consequences of improper exposure
1) increased density - under exposed/penetrated - appears white because too little contrast
2) decreased density - over exposed/penetrated -appears lucent/dark - too much contrast
Written data -things you should check
- the patients right side is on your left (i.e. view images as through you are standing in front of the patient)
- patients name may give clue to ethnic group (certain diseases are more prevalent in some groups)
- may state hospital ward patient is on
Things to check when looking at the chest wall/soft tissues
1) Check each rib individually
2) Check the clavicles
3) Check for the presence or absence of breastss
4) Check for the presence of soft tissue masses
5) Check the vertebra (body, pedicles, spinous process, disc space)
Things to check when looking at the abdomen
Looking for intrraperitoneal air (indicates perforated ulcer?
I.e. air rising above diaphragm
Things to check when looking at the diaphragm
- Point where diaphragm meets chest wall forms a shart acute angle (the lateral and posterior costophrenic angles)
- Right hemidiaphragm normally about 2cm higher than the left
- Normal diaphragm is convex
What flat diaphragms can indicate
-emphysema -due to hyperinflated lung
Things to check when looking at pleura
- Are costophrenic angles blunted?
- Scrutinize perimeter of lung laterally and medially
3 Pleural calcifications?
Cause of blunting costophrenic angles
- pleural effusion
- thickening
Minimum amount of fluid needed to detect a pleural effusion on a lateral and frontal film
-75-200 cc
Apperance of pneumothorax
thin white line representing the visceral pleura separated from the chest wall
Meniscus sign
- aka air crescent sign
- the result of air accumulation between a mass or nodule and normal lung parenchyma
- most frequently encountered in patients with aspergillosis
- we saw it in case of effusion
Assessing heart size
Cardiothoracic (CT) ratio = maximum transverse diameter of heart/maximum transverse diameter of rib cage
Normal CT ratios
> 0.5 on PA view
0.6 on AP view
suggestive of cardiomegaly
Composition of hila
- lobar bronchi
- pulmonary arteries/veins
- lymph nodes
Position left and right hilum
-left hilum is slightly higher than right
What may cause hila enlargement
- arteries
- masses
- enlarged lymph nodes
What checking hila for
- nodules or masses
- seen as enlarged hilum
Radiographic appearance of lung parenchyma
- gas filled alveoli = black
- pulmonary vessels = white
- bronchi don’t normally contriute to radiographic density
How to recognize vessels in the lung parenchyma
They have a tapering and branching pattern
Views of computed tomorgraphy
- saggital
- coronal
- transverse/axial
Checking for nodules in CT - meaning of random distribution
- TB
- Mets
Checking for nodules in CT- meaning of centrilobar distribution
- disease that enter lung through airways
- hypersensitivity pneumonitis
- respiratory bronchiolitis
- centrilobular emphysema
Checking for nodules in CT -meaning of perilymphatic distribution
- diseases that enter via lymphatics
- sarcoidosis (classic)
- silicosis
- lymphangitic carcinomatosis
- pulmonary edema
Approach to disease patterns on CT
- Identify the pattern:
- Distribution and content
- upper or lower lobes
- Central or peripheral
- Associated findings- pleural effusion, lymphadenopathy, enlarged heart and pulmonary vasculature, calcification
Identify the pattern algorithm
1. Increased or decrease opacity/attenuation A. increased opacity/attenuation/density -consolidation? -interstitial? -nodular/mass? -Atelectasis? B. Decreased opacity/attenuation/lucent -pneumothorax -emphysema -bronchiectasis
Different contents
- Water
- Pus
- Blood
- Cells
Different distributions and what they could indicate
1) Lobar
2) Diffuse
3) Multi-focal
Differential diagnosis water consolidation
- heart failure
- ards
- low albumin
- renal failure
Differential diagnosis pus consolidation
-pneumonia
Differential diagnosis blood consolidation
- trauma
- goodpasture
- henoch schonlein
- SLE
Differential diagnosis cell consolidation
- BAC
- organizing pneum
- chron eosin pneum
- sarcoid
