Pulmonary Diagnostic Imaging Flashcards
What 3 types of pulmonary imaging do NOT emit ionizing radiation?
Ultrasound
MRI/MRA
Bronchoscopy
Almost 50% of the ionizing radiation the US population is exposed to comes from _________
Medical imaging
Which imaging type is usually the initial study to evaluate respiratory symptoms?
Chest x ray
What is inherent contrast?
Air in the lungs providing a contrast to surrounding soft tissue and bones
What are the 4 most common views for a chest x ray?
PA
AP
Lateral
Decubitus
Which one do we use more for CXR: AP or PA view
PA
Why don’t we use AP view for CXRs very much?
It makes the heart look bigger than it actually is.
AP usually only done if the pt cant get out of bed for whatever reason
We look at the structures in a chest x ray in a certain order:
ABCDEF
What do they each stand for?
A-airway (trachea, foreign bodies)
B- bones (clavicles, ribs)
C- cardiac (borders, size)
D- diaphragm
E- edges (edges of lungs: effusions, plaques, costophrenic angles)
F- fields (lung fields…looking for nodules etc)
Can you see the lower lobes from the PA view?
Not very well. Must do lateral to really see them
The R atria of the heart is next to this lung lobe______
RML
So if R atria border isn’t crisp, you might suspect that there’s some sort of infiltrate in the RML
What is the apical lordotic view used for?
When you’re trying to see something in the apex of the lungs.
(Its the one where the patient leans back)
Why would we use a decubitus view?
You compare the PA and the decubitus X rays to see if fluid/effusions move when the pt lays down
What does a “Hampton’s Hump” look like?
A wedge shaped opacity with its base against the pleural surface of the lung
What does a Hamptoms hump indicate?
A Pulmonary Embolism/Infarct
Is the radiation exposure from a chest x ray a lot?
It is minimal BUT cumulative
Idk she had it bolded and underlined
What are some of the risks and limitations of CXR/
Radiation (minimal but cumulative)
Pregnancy
Some conditions cant be detected (very small cancers, pulmonary emboli)
When reading a CT scan, whaere should you imagine you are looking in relation to the patient
Looking up from the patients feet
Why would you order a chest CT?
Clarify abnormal CXR (most common)
Help diagnosis
Characterize pulmonary nodules
Staging of primary and metastatic cancer
Screening for lung cancer
Evaluate mediastinal/hilar masses
Who needs to have a chest CT done to screen for lung cancer?
55-80 yr olds with a 30 pack year smoking history who currently smoke or quit in the last 15 yrs
What are the 2 types of CT scan “slicing patterns”?
Conventional- “step and shoot”
Helical/spiral- continuous
Which takes longer: a conventional CT or a helical/Spiral CT?
Conventional CT takes longer 25-30 min
Helical CT takes less than 5 min
What is the difference between High Resolution CT and Low Dose CT?
HRCT- better detail and 1mm slices
Low Dose CT- less detail, used for screening
What kind of CT do we use to screen for lung cancers’?
Low Dose CT
What is a multidetector/multislice CT?
It takes multiple slices at each step and is 64 times faster than single slices. BUT it has higher radiation
What is the most common reason we order chest CTs
To clarify an abnormal CXR
Can you see subcutaneous emphysema on a chest CT?
Yes
Looks like marbling under skin
Which is more sensitive to patient movement:
CT or MRI
MRI
Can CTs be done if pt has an implanted device?
Yes
Can CT be used for real time imaging when doing biopsies?
Yes
What are the risks of CT?
Radiation- A LOT
Increased cancer risk
Fetal exposure during pregnancy (avoid)
Problems with contrast
What is the weight limit of CT?
450 lbs
1 chest CT = _____ CXRs
80
1 CT pulmonary embolism protocol = ________ CXRs
150
Why are we so cautious with doing CT scans on children?
They are more radiosensitive
Their radiation risk is compounded by a longer lifespan
Increased risk of leukemia and brain tumors
You have a 32 yo female patient who has a weird CXR. You decide you need to investigate further with a chest CT. What do you NEED TO DO before you proceed?
Ask LMP!!!!
****
Was Red and big and had exclamation point
What happens if you do a CT scan on a pregnant woman?
The kid can get cancer and die
What kind of contrast in used in CT
Iodine
Why do we use contrast?
Enhances differences in densities of various structures
(Ex: would be good for a large blood vessel encased in and constricted by a tumor)
CT w/o contrast: vessel and tumor will appear as one homogenous mass
CT w/ contrast: narrowing of vessel will be apparent
What are some times you do use contrast when doing a CT?
Masses
Cancer
Obstructive processes
PE
Dissection
When are the only 2 times you would NOT use contrast in a CT?
High resolution CT
Follow up on known pulmonary nodules
*****
What are the risks of using contrast?
Allergic reaction
Kidney damage
Developing lactic acidosis if taking Metformin
If someone is on Metformin and they need a CT with contrast, what do you need to do to prevent them from developing lactic acidosis?
Stop taking metformin for 48 hours after the imaging
How long after giving the contrast would it take for an allergic reaction to happen
5-60min
Is shellfish allergy a contraindication to contrast?
NO*****
What kinds of things should make you nervous before giving contrast to a patient?
Prior reaction (itchy, SOB, flushed, etc)
Asthma
Atopy
If someon had a mild reaction to contrast before and you REALLY need to use it, what should you do?
Pre treat them with prednisone and Benadryl
How much of a change in serum creatinine will indicate that the patient has suffered contrast induced kidney damage?
25% or more from baseline
OR
0.5mg+
Is contrast induced kidney damage reversible?
Usually yes
What is the best treatment for contrast induced nephropathy?
Prevention 🙄
What Creatinine levels and GFRs should make you say “I’m not OK giving this person contrast”
Creatinine: 1.5 or higher
GFR less than 60
What are some alternate imaging methods you can use in patient whose kidneys cant handle contrast (Creat >1.5 or GFR <60)
CT w/o contrast
MRI w/o gadolinium
Ultrasound
What patients need to have their renal function checked before giving them iodine contrast?
> 60 yrs
History of renal problems/dialysis
HTN treated w medication
Diabetes
Taking metformin
Do you use contrast in a patient when you’re doing a 3 month follow up of a lung nodule
No
What does lateral decubitus position help you see
Effusions
When can a patient on Metformin get contrast CT and keep taking their Metformin
If their eGFR is 30 or more
If a patient is on Metformin and their GFR is less than 30, or their kidneys just suck, what do you need to do when you give them contrast?
Hold metformin for 48 hrs after contrast
Resume only after re-checking renal function
What does angiography do?
Allows you to assess vasculature
Do you ever inject contrast and then just do nothing else
No you will always do some sort of imaging lol
When do you use CT Pulmonary angiography (CTPA)?
PE
Aortic dissection
Superior vena cava syndrome
Pulmonary arterial invasion by neoplasm
What is the difference between CTPA and conventional pulmonary angiography?
CTPA involves a CT scan and dye is injected in a peripheral vein
Conventional pulmonary angiography involves a catheter directed through the R femoral or internal jugular vein right to the pulmonary arteries, shoots dye right at the target, and then an X RAY is taken
What is the gold standard in evaluation of PE?
Direct Pulmonary Angiography
aka Catheter/Conventional Pulmonary angiography *******
**BOARD QUESTION**
When would you use Direct Pulmonary angiography to evaluate PE?
If you did a VQ scan or CTPA and they were inconclusive, but you still have a high clinical suspicion of PE.
This will show a really small PE, where the other two imagings might not
Is direct pulmonary angiography expensive?
yes
Are there any risks of direct pulmonary angiography?
Yes
Bleeding/hematoma at catheter insertion site
Heart arrhythmia- you’re guiding the catheter THROUgh the heart
Allergy to contrast
Impaired kidney function
Radiation exposure
The usefulness of MRI is limited in pulmonary disease. When would we use it?
Hilar/mediastinal densities, sulcus tumors, cysts/lesions of chest wall
Allergy to contrast
Extreme kidney disease (GFR<60)
What are the benefits of MRI over CT
No bone artifact
No ionizing radiation
What kind of imaging would be useful to evaluate a Pancoast (sulcus) tumor?
MRI
What kind of contrast material is used for MRI and MRA exams?
Gadolinium
Compared to a chest CT, MRI gives you a (more/less) detailed view of lung parenchyma
Less
What is nephrogenic systemic fibrosis?
Irreversible fibrosis of the kidney
What can cause nephrogenic systemic fibrosis?
If the pt has a GFR<30 and you give them gadolinium!!!
So don’t freakin do an MRI with gadolinium contrast! IRREVERSIBLE FIBROSIS OF KIDNEY
What are the contraindications of doing MRI/MRA?
Pacemaker or defibrillator
Metal in eye
Aneurysm clip
Cochlear implant
***** must know
What is the most common use of a VQ scan?
To evaluate for pulmonary embolism
What does a V/Q mismatch mean?
There is an imbalance of blood flow and ventilation
Does VQ scan expose you to radiation?
Yes.
2 types of radiation!
Technetium-99 for circulation
Xenon gas for ventilation
What are the 2 phases of a VQ scan?
IV phase- technetium-99 is injected to see PERFUSION
Inhalation phase- radio-labeled Xenon gas is inhaled to see VENTILATION
What is the test of choice for diagnosing PE in pregnant women?
V/Q scan**
They can do just the perfusion phase and/or cut the radiation in half
Is a VQ scan best used in someone with a normal or abnormal CXR?
Normal**
What should you do if your pt has a normal CXR, but you have a high suspicion for PE?
VQ scan**
VQ scans have a high number of false (positives/negatives) when evaluating PE
Many false positives
Sensitive for PE but not specific
What kind of images are acquired from a PET scan?
Physiologic Images***
This was in red
What is injected into the patient when doing a PET scan?
fluorodeoxyglucose (FDG)
This is radioactively labeled glucose
Where does FDG accumulate in the patient?
Tissues/organs with high metabolic activity LIKE CANCER CELLS
How is the uptake of FDG measured when doing a PET scan?
Measurements of the uptake are made in standardized uptake value (SUV)
When doing a PET scan, what SUV raises the suspicion for malignancy?
Over 2.5
What is PET most often used for?
Used to detect cancer/metastasis from primary site
What imaging might you use to examine the effects of cancer therapy?
PET scan
(Chemo might have killed the tumor, but the scarring will still be there, so on CT, it might look like the chemo didn’t do anything. A PET scan will show you its dead)
What kind of imaging is PET scan often combined with?
CT scan.
So you can see anatomic and physiologic information at the same time
What is one of the major benefits of a PET scan?
You can detect biochemical changes of anatomy BEFORE they can be seen with CT or MRI
What causes false results in PET scans?
Metabolic imbalances.
False Positive- inflammatory lesions
False Negative- slow growing tumors
When would you see a “seashore sign” and is it good or bad?
When doing a thoracic ultrasound.
It is good 🏝
When would you see a “barcode” or “stratosphere” sign, and is it good or bad?
When doing a Thoracic ultrasound
It is bad :(
When is Rigid Bronchoscopy most often used?
Tracheal or Bronchus Obstruction
Foreign Body Removal
True or False:
Bronchoscopy can be diagnostic and therapeutic
True
Can evaluate lung conditions and can also sample tissues, place ET tubes, and remove excess mucus or FBs
What are the 2 types of bronchoscope?
Flexible
Rigid
What kind of complications does bronchoscopy have?
MINOR COMPLICATIONS
Hemmorhage, pneumothorax, hypotension, arrhythmia
What are the contraindications to bronchoscopy?
Severe hypoxia (can’t go without O2 for long)
Bleeding risk (anticoagulants)
Risk of cardio/pulm decompensation (MI, asthma or COPD exacerbation, CHF, Major arrhythmias)
***she said to know these
