Aquifer - Radiology
What is the total range of hounsfield units availabe? - ✔️✔️-1000 (air) to +1000 (metal)
[so range is 2000]
What does a typical computer display show for greyscale range? What can the human
eye actually distinguish? - ✔️✔️256shades (that means each shade of grey covers
~8HU)
The can only distinguish 17 shades of grey
What is a good way to check diaphragm flattening? - ✔️✔️Look at the lateral film
Window vs. Reconstruction on CT? - ✔️✔️Reconstructions - processing of the raw CT
data allows for better resolution of the structures [higher resolution and higher contrast]
Reconstruction can be done in 3D (ortho) or in a linear way too (vascular)
Diaphragm will be flat like you can set a ruler down on the edge
What can a poor inspiration/hypoinflation appear like? - ✔️✔️consolidation or PNA
How to look at the lung fields? - ✔️✔️Sweep or a zig zag down the lung field (both in
PA and lateral views)
look for focal, diffuse, BL asymmetrical, interstital/vasc markings, lucencies
(cavity/bullae/PTX),
compare upper and lower and L/R zones
Middle
lower zones
Which hilum should always appear higher on the radiograph? - ✔️✔️The LEFT sided
hilum should be higher - if its not its pathological
What to look for with the heart? - ✔️✔️Size of the heart - the cadiac:thoracic cavity
ratio
LA
LV
What mediastinal lines should be observed on PA film? - ✔️✔️R paratracheal line
Azygous area
Azygoesophageal line
Paraaortic line (all the way down)
,If you can see these you need to figure out the reason why
How to look at the bones on Xray? - ✔️✔️Quadrant method [above and below the ribs]
(the middle lung section you just
also go down the spine looking for abnormalities, mets, or collapse
When should you START looking at OLD films? - ✔️✔️AFTER you have
COMPLETELY evaluated the new scan
What are the ACR appropriateness criteria? - ✔️✔️The aim is to provide continuously
updated evidence-based algorithms that ensure the safest, most cost-effective, and
most efficient path to radiological diagnosis or intervention matched to specific variants
of clinical presentations.
Federal LAW requires referring physicians to consult Appropriate Use Criteria (AUC),
such as ACR Appropriateness Criteria, prior to ordering advanced imaging services
(ADIS), including CT, MR, nuclear medicine, and PET, for Medicare patients.
How are appropriateness criteria divided/staged? - ✔️✔️Older appropriateness rating
tables used a numerical rating scale: • Usually Appropriate = 9, 8, or 7 • May be
Appropriate = 6, 5, or 4 • Usually Not Appropriate = 3, 2, or 1
Newer appropriateness rating tables simply use the three categories: • Usually
Appropriate (Green cells in the table) • May be Appropriate (Yellow cells in the table) •
Usually Not Appropriate (Red cells in the table)
What lobe of lung is seen at the apicies? - ✔️✔️The R and L upper lobes
What is the silhouette sign? - ✔️✔️The visual interface between structures of different
density.
Its actually when a silhouette is LOST that we say its a "silhouette sign"
What is spine sign? - ✔️✔️When the combined density of the vertebrae and some
source of fluid/consolidation make the vertebrae look MORE dense [just like ice over
water accentuates the ice appearing like they have increased density even though they
still the same ice]
What are cases in which spine sign occur? - ✔️✔️Spine sign - vertebral bodies should
be relative lucent (black) above the diaphragm on lateral projection.
-Lateral x-ray goes through spine + pneumonia and vertebra will appear whiter (fewer x-
rays reach detector since some are absorbed in the pneumonia)
,- Helpful sign for detection of lower lobe pneumonia. - - Very useful for detecting LLL
pneumonia behind the heart.
- If vertebral bodies appear more dense (whiter) above the level of diaphragm, and part
of one of the diaphragms is obscured → spine sign → sign of lower lobe pneumonia
- There are other causes for the spine to appear whiter (such as a blastic bone
metastasis).
What is the lingula aligned with? - ✔️✔️The left heart border (this is more visible in the
lateral view xray)
What are air bronchograms? - ✔️✔️Air-filled bronchi within an area of consolidation.
These are frequently seen in pneumonia, but can also be seen in some tumors and
other lung abnormalities
More common in alveolar disease
Air bronchogram ≠ pneumonia
Can be seen in lung cancer (adenocarcinoma with bronchioloalveolar pattern)
Can be seen in lymphoma of the lung
Seen in:
A. Pneumonia
C. Pulmonary edema
D. Pulmonary hemorrhage
E. ARDS
Which patients w/ PNA should have a follow up xray? - ✔️✔️All patients > 40 years
History of recurrent pneumonia
Current/former smokers
Patients whose symptoms do not resolve
What is the MC cause of solitary pulmonary nodules on CT scan? - ✔️✔️Well-
differentiated adenocarcinoma (formerly known as bronchioalveolar carcinoma (BAC))
Common in smokers AND non-smokers (esp females)
True/False - mycoplasma PNA can cause Kerley B lines as seen in CHF?
What are Kerley B lines? - ✔️✔️TRUE
Kerley B lines (septal lines) represent thickening of interlobular SEPTA
Note that sometimes Kerley B lines can be distinguished because they extend and
touch the pleura
, What are ground glass opacities? - ✔️✔️"Ground glass" is a radiology descriptive term
(used in both chest radiographs and CT imaging) to indicate that blood vessels are not
obscured, as would be the case in alveolar lung opacities.
Compare ground glass opacities vs. consolidation opacities - ✔️✔️Ground Glass:
Blood vessels are not obscured on CT.
"Smoke-like" opacity on CT that does not obscure blood vessels
Descriptive term (usually primarily used on CT imaging). May represent either interstitial
or alveolar disease. Some diseases (like PJP infection in HIV infection, early edema,
etc.), often have "ground glass" opacities early in the disease process.
Consolidation: BLOOD VESSELS are obscured on CT and air bronchograms are more
common.
What dosage of radiation in x-rays is 1 CT scan worth? - ✔️✔️150 x-rays worth of
radiation per CT scan (ON AVERAGE)
Some scans use more or less however depending on the application - for example
PE scan = 400CXRs
Abdominal Scan = 750CXRs
V/Q scan = 800CXRs
What is a hydropneumothorax? How much fluid is needed to be able to distinguish this?
- ✔️✔️AN AIR-FLUID LEVEL (a horizontal edge between air and fluid)
You will only see air-fluid levels on upright or decubitus studies
It takes at least 150 cc of fluid to see it on a PA CXR;
50 cc on a lateral;
and about 5 to 10 cc on a CT scan.
What is a pleural pseudotumor? - ✔️✔️A pleural "pseudotumor" is a loculated or
localized collection of fluid in a major (oblique) fissure or right minor (horizontal) fissure
and it can be mistaken for mass in the lung (hence the name "pseudotumor"). They are
more common in pleural effusions associated with CHF for reasons that are not well
explained. The abnormality is in the pleural space and NOT in the lung.
What is deep sulcus sign? - ✔️✔️Deep sulcus sign is the sign of a pneumothorax on a
supine chest radiograph (look for costophrenic angle thats pushing DOWN with a very
sharp looking sulcus)
What is continuous hemidiaphragm sign? - ✔️✔️Continuous hemidiaphragm sign is a
sign of a pneumomediastinum on a chest radiograph
What is the total range of hounsfield units availabe? - ✔️✔️-1000 (air) to +1000 (metal)
[so range is 2000]
What does a typical computer display show for greyscale range? What can the human
eye actually distinguish? - ✔️✔️256shades (that means each shade of grey covers
~8HU)
The can only distinguish 17 shades of grey
What is a good way to check diaphragm flattening? - ✔️✔️Look at the lateral film
Window vs. Reconstruction on CT? - ✔️✔️Reconstructions - processing of the raw CT
data allows for better resolution of the structures [higher resolution and higher contrast]
Reconstruction can be done in 3D (ortho) or in a linear way too (vascular)
Diaphragm will be flat like you can set a ruler down on the edge
What can a poor inspiration/hypoinflation appear like? - ✔️✔️consolidation or PNA
How to look at the lung fields? - ✔️✔️Sweep or a zig zag down the lung field (both in
PA and lateral views)
look for focal, diffuse, BL asymmetrical, interstital/vasc markings, lucencies
(cavity/bullae/PTX),
compare upper and lower and L/R zones
Middle
lower zones
Which hilum should always appear higher on the radiograph? - ✔️✔️The LEFT sided
hilum should be higher - if its not its pathological
What to look for with the heart? - ✔️✔️Size of the heart - the cadiac:thoracic cavity
ratio
LA
LV
What mediastinal lines should be observed on PA film? - ✔️✔️R paratracheal line
Azygous area
Azygoesophageal line
Paraaortic line (all the way down)
,If you can see these you need to figure out the reason why
How to look at the bones on Xray? - ✔️✔️Quadrant method [above and below the ribs]
(the middle lung section you just
also go down the spine looking for abnormalities, mets, or collapse
When should you START looking at OLD films? - ✔️✔️AFTER you have
COMPLETELY evaluated the new scan
What are the ACR appropriateness criteria? - ✔️✔️The aim is to provide continuously
updated evidence-based algorithms that ensure the safest, most cost-effective, and
most efficient path to radiological diagnosis or intervention matched to specific variants
of clinical presentations.
Federal LAW requires referring physicians to consult Appropriate Use Criteria (AUC),
such as ACR Appropriateness Criteria, prior to ordering advanced imaging services
(ADIS), including CT, MR, nuclear medicine, and PET, for Medicare patients.
How are appropriateness criteria divided/staged? - ✔️✔️Older appropriateness rating
tables used a numerical rating scale: • Usually Appropriate = 9, 8, or 7 • May be
Appropriate = 6, 5, or 4 • Usually Not Appropriate = 3, 2, or 1
Newer appropriateness rating tables simply use the three categories: • Usually
Appropriate (Green cells in the table) • May be Appropriate (Yellow cells in the table) •
Usually Not Appropriate (Red cells in the table)
What lobe of lung is seen at the apicies? - ✔️✔️The R and L upper lobes
What is the silhouette sign? - ✔️✔️The visual interface between structures of different
density.
Its actually when a silhouette is LOST that we say its a "silhouette sign"
What is spine sign? - ✔️✔️When the combined density of the vertebrae and some
source of fluid/consolidation make the vertebrae look MORE dense [just like ice over
water accentuates the ice appearing like they have increased density even though they
still the same ice]
What are cases in which spine sign occur? - ✔️✔️Spine sign - vertebral bodies should
be relative lucent (black) above the diaphragm on lateral projection.
-Lateral x-ray goes through spine + pneumonia and vertebra will appear whiter (fewer x-
rays reach detector since some are absorbed in the pneumonia)
,- Helpful sign for detection of lower lobe pneumonia. - - Very useful for detecting LLL
pneumonia behind the heart.
- If vertebral bodies appear more dense (whiter) above the level of diaphragm, and part
of one of the diaphragms is obscured → spine sign → sign of lower lobe pneumonia
- There are other causes for the spine to appear whiter (such as a blastic bone
metastasis).
What is the lingula aligned with? - ✔️✔️The left heart border (this is more visible in the
lateral view xray)
What are air bronchograms? - ✔️✔️Air-filled bronchi within an area of consolidation.
These are frequently seen in pneumonia, but can also be seen in some tumors and
other lung abnormalities
More common in alveolar disease
Air bronchogram ≠ pneumonia
Can be seen in lung cancer (adenocarcinoma with bronchioloalveolar pattern)
Can be seen in lymphoma of the lung
Seen in:
A. Pneumonia
C. Pulmonary edema
D. Pulmonary hemorrhage
E. ARDS
Which patients w/ PNA should have a follow up xray? - ✔️✔️All patients > 40 years
History of recurrent pneumonia
Current/former smokers
Patients whose symptoms do not resolve
What is the MC cause of solitary pulmonary nodules on CT scan? - ✔️✔️Well-
differentiated adenocarcinoma (formerly known as bronchioalveolar carcinoma (BAC))
Common in smokers AND non-smokers (esp females)
True/False - mycoplasma PNA can cause Kerley B lines as seen in CHF?
What are Kerley B lines? - ✔️✔️TRUE
Kerley B lines (septal lines) represent thickening of interlobular SEPTA
Note that sometimes Kerley B lines can be distinguished because they extend and
touch the pleura
, What are ground glass opacities? - ✔️✔️"Ground glass" is a radiology descriptive term
(used in both chest radiographs and CT imaging) to indicate that blood vessels are not
obscured, as would be the case in alveolar lung opacities.
Compare ground glass opacities vs. consolidation opacities - ✔️✔️Ground Glass:
Blood vessels are not obscured on CT.
"Smoke-like" opacity on CT that does not obscure blood vessels
Descriptive term (usually primarily used on CT imaging). May represent either interstitial
or alveolar disease. Some diseases (like PJP infection in HIV infection, early edema,
etc.), often have "ground glass" opacities early in the disease process.
Consolidation: BLOOD VESSELS are obscured on CT and air bronchograms are more
common.
What dosage of radiation in x-rays is 1 CT scan worth? - ✔️✔️150 x-rays worth of
radiation per CT scan (ON AVERAGE)
Some scans use more or less however depending on the application - for example
PE scan = 400CXRs
Abdominal Scan = 750CXRs
V/Q scan = 800CXRs
What is a hydropneumothorax? How much fluid is needed to be able to distinguish this?
- ✔️✔️AN AIR-FLUID LEVEL (a horizontal edge between air and fluid)
You will only see air-fluid levels on upright or decubitus studies
It takes at least 150 cc of fluid to see it on a PA CXR;
50 cc on a lateral;
and about 5 to 10 cc on a CT scan.
What is a pleural pseudotumor? - ✔️✔️A pleural "pseudotumor" is a loculated or
localized collection of fluid in a major (oblique) fissure or right minor (horizontal) fissure
and it can be mistaken for mass in the lung (hence the name "pseudotumor"). They are
more common in pleural effusions associated with CHF for reasons that are not well
explained. The abnormality is in the pleural space and NOT in the lung.
What is deep sulcus sign? - ✔️✔️Deep sulcus sign is the sign of a pneumothorax on a
supine chest radiograph (look for costophrenic angle thats pushing DOWN with a very
sharp looking sulcus)
What is continuous hemidiaphragm sign? - ✔️✔️Continuous hemidiaphragm sign is a
sign of a pneumomediastinum on a chest radiograph
