CT Imaging of the Thorax Flashcards
Where is this done at:
patient is sent out for imaging (CT) at an imaging center or hospital; radiologist does complete interpretation of images, and you receive report
primary care outpatient setting
Where is this done at:
Some have CTs, some don’t; you may review and interpret x-rays and can ask for a quick read by radiologist or wait for results; radiologist has final “read” responsibility and will send report
Urgent care
Where is this done at:
patient is taken from bed to imaging department nearby; provider may review images and will often consult with the radiologist by phone for urgent image results; radiologist has final “read” responsibility
emergency department
Where is this done at:
- ordering imaging prior to surgery; they will often review imaging as well as radiologist; radiologist has final “read” responsibility, but surgeon is heavily involved and may act on their own interpretation
surgery
What settings can imaging interpretation be done?
- primary care outpatient setting
- urgent care
- emergency department
- surgery
What is the #1 reason for a chest CT?
follow-up on an abnormal chest radiograph result
What are indications for a chest CT?
- abnormal chest x-ray results
- lung or thorax cancer
- evaluate for acute pulmonary infection or acute process
- evaluate from cardiac or vascular disease
- trauma
How are chest CTs used for lung/thorax cancer?
- annual screening or lung cancer
- presence of pulmonary nodules
- further evaluation of a suspicious mass on CXR
- identification of metastasis from another primary cancer
- cancer staging
- tumors in mediastinum (lymphomas/thymomas)
What are these associated with:
- pneumonia that hasn’t resolves or is atypical in appearance
- empyema of lungs
- pulmonary embolism
- ARDS (acute respiratory distress syndrome)
- pneumothorax or hemothorax
chest CT to evaluate for acute pulmonary infection or acute process
What are these associated with:
- COPD
- interstitial lung disease
chest CT to evaluate for chronic pulmonary disease
What are these associated with:
- thoracic aortic aneurysm or dissection
- congenital cardiac disease
- coronary artery occlusion
- strain or hypertrophy of ventricles
- pericardial disease
chest CT to evaluate for cardiac or vascular disease
What are these associated with:
- rib fractures and flail chest
- major contusions chest wall
- general scan after major trauma (pan scan)
chest CT for trauma
What is performed to further investigate inconclusive or abnormal CXR findings?
chest CT
What are some advantages of a CT?
- rapid scanning time (5-10 mins)
- useful in emergent situations
- provides large amount of information to help narrow differential diagnosis
- available and ubiquitous
- less claustrophobia than MRI
- no need for sedatives for claustrophobic patients
What are some disadvantages of a CT?
- significant radiation exposure
- exposure to contrast agents and potential (small) for nephrotoxicity or adverse renal events
What consists of hundreds of xrays that are stitched together by a computer program?
CT scans
What is this describing:
gantry moves patient into position, stops and image taken. This is repeated for all sequences and scan can take 5-10 minutes?
traditional CT
What is this describing:
in this type of CT, the gantry moves continuously to put the patient into the correct position for each image. Scan can be under a minute
helical CT
What is this describing:
uses helical technology, but now has up to 256 detectors to create quick and detailed images
multidetector CT
What are some CT scan advantages over x-rays?
- avoids superimposition of structures found on xrays
- able to provide detailed imaging of specific areas
- more accurate diagnosis over x-ray
- large amount of detail rapidly which allows for quick diagnosis in ED
What are the different views/positioning of CT scans and can be switched by use of your computer?
- coronal view
- sagittal view
- axial view
When we view CT images, we interpret them as if what?
as if we are standing at the patient’s feet and looking up at the “slices” made by the CT
What describes the radiodensity of material?
attentuation
As x-ray passes through denser objects like bone or metal, the signal is (1)
highly attenuated
In CT scans, bone and metal appear?
highly attenuated (white)
In CT scans, soft tissue and fat appears?
grey
In CT scans, air appears?
low attenuation (dark grey to black)
The density of structures on CT is measured in (1)
Hounsfield units
Blood is (1) than water, so it will appear (2)
- more dense
- whiter
What may have higher density than the tissue around it?
a tumor
What is used to improve their interpretation, and radiologists can “zoom in” within different ranges of the hounsfield scale?
windowing
What are the different types of windows on the CT thorax?
- soft tissue window (organs, anything soft)
- bone window
- lung window (pneumonia)
What is used to better visualize for soft tissue structures of the thorax (fat, muscles, organs)?
soft tissue window
What does not visualize the lung parenchyma as it is out of the Hounsfield range of the window?
soft tissue window
What gives you the ability to view the lung parenchyma for visualization of:
- pneumonia
- nodules or masses
- COPD
- occupational lung disease
- interstitial lung disease
lung window
What gives you the ability to view:
- clavicle
- sternum
- vertebral bodies
- ribs
bone window
What allows you to evaluate for:
- fracture or trauma
- bony malignancy or metastasis
- degenerative disk disease
bone window
What does this describe:
- increased density
- higher Hounsfield units
hyperdense
What does this describe:
- less dense
- lower Hounsfield units
hypodense
What does this describe:
- same density when compared to other tissue
isodense
What can be added to the images to better delineate specific structures and can have systemic reactions from any administration, but anaphylaxis-type reactions almost always with IV administration?
contrast
What are the different types of contrast used in CT?
- intravenous iodine based
- oral/rectal barium-based
What is used to evaluate for intravascular and organ disease?
intravenous iodine based contrast
What is better when evaluating digestive or GI conditions, can be used to identify colon or rectal tumors on CT abdomen and pelvis, and is not used in chest imaging?
oral/rectal barium-based contrast
What are some other routes of IV iodinated contrast that are less common?
- intrathecal
- intraarterial
- intraabdominal
Some people have different reactions when given what?
contrast
What is the most severe and possibly fatal adverse outcome with IV iodinated contrast?
- anaphylactoid reactions
(1) do not require previous exposure while (2) do require previous exposure to occur
- anaphylactoid reactions
- anaphylactic reactions
What causes possible increase in serotonin, histamine, and complement cascade? (can make you itch)
contrast
People with allergic-like reactions to contrast can be what?
premedicated with oral steroid and antihistamine
What results from properties of the contrast material that can cause ionic or fluid disruptions to body homeostasis and is usually brief and transient?
nonanaphylactoid reactions
What are some nonanaphylactoid reactions?
- feeling of flushing or warmth
- metallic taste in mouth
- nausea or vomiting
- bradycardia
- vasovagal lightheadedness
- neuropathy
What are some indicationns to order a CT of thorax with contrast?
- don’t need to focus on the circulatory system
- focus is on lung parenchyma
Annual CTs are used for?
preventative screening for lung cancer
In a CT with and without IV contrast, patient may be scanned (1) contrast first and then contrast is (2) and a second scan is performed
- without
- added
If you order a CT with and without contrast, the images are what?
timed to be taken when contrast reaches specific structures (capillary beds for most exams, pulmonary arteries for possible pulmonary embolism)
What are some indications for ordering a CT of the thorax with and without IV contrast?
- suspicion of lung cancer
- infection of the skin and soft tissue
What is non-standard and is when images are times to coincide with the contrast material passing through the pulmonary arterial system?
CT pulmonary angiogram (CT-PA)
What are indications for a CT-PA?
suspicion for a pulmonary embolism
What is non-standard and is when images are timed to coincide with the contrast material passing through specific parts of arterial system?
- CT angiography
What are some indications for a CT angiography?
- aneurysms
- artherosclerosis
- evaluate arteries supplying a tumor
- stenosis of blood vessels
What are the different contrast phases?
- arterial phase
- venous phase
- delayed phase
What contrast phase is 15-45 seconds after IV contrast?
arterial phase
What contrast phase is 60 seconds after IV contrast?
venous phase
What contrast phase can be up to 10 minutes after injection?
delayed
Everyday, we are exposed to radiation as measures in (1)
- millisierverts (mSv)
You have an increased risk of cancer with what (radiation)?
- prolonged exposure to 10 mSv
- brief exposure to 50 mSv
Who have a higher likelihood of later cancer vs. non exposed children? What cancers?
children exposed to CT scan
- leukemia
- brain cancer
One CT scan of the abdomen and pelvis without contrast is equivalent to (1) chest xrays and (2) mammograms
- 220
- 37
What do principles of ALARA in radiology mean?
as low as reasonably achievable (in radiology)
Which settings have the highest risk of radiation?
- ED
- surgery
- primary care
What is the upper limit of normal size for the ascending aorta?
4 cm
What is the upper limit of normal size for the descending aorta?
3 cm
Evaluation of the aorta on CT scans is looking for what?
- plaques on walls
- aneurysm or dissection
- thrombus
What decrease in size as they get closer to bifurcating at the T5 level?
pulmonary arteries
Why do you evaluate the appearance of pulmonary arteries on a CT?
- filling defects with PE
- aneurysms of pulmonary arteries
What is the mediastinum generally evaluated for in CT scans?
masses
- lymphoma
- thymoma
- teratoma
- thyroid masses
What is thin-walled and appears ovoid during inspiration and partially flattens with exhalation?
trachea
What is thin-walled and can be hard to see as they move toward the periphery?
bronchi and bronchioles
What are the steps in evaluation of a CT scan?
step 1: right pt, right scan, right date
step 2: review pts history and physical
step 3: review all windows on CT using systematic approach
