L9: Pulmonary Diagnostic Imaging Flashcards
List 5 indications for ordering chest x-ray.
- SOB
- Persistent cough
- Hemoptysis
- Chest pain or injury
- Fever
Describe the systematic approach to reading a CXR.
A: Airways (trachea midline?) B: Bones (good inspiration, fractures?) C: Cardiac silhouette/CPA (are they clear?) D: Diaphragms (is there free air?) E: Edges (pleural plaques, effusion?) F: Fields (infiltrates, nodules?)
What are the 2 most basic views that should be ordered for a CXR?
PA and Lateral
What benefits does a lateral view have?
Pts lay on L side
Helps to not significantly magnify the heart
Allows us to see posterior structures
When would an apical lordotic view be useful?
When trying to visualize the apices of the lungs (such as with TB)
*Pt positioned at 30 degrees forward
A Hampton’s Hump seen on CXR is indicative of a:
Pulmonary infarct
What conditions cannot be seen on a CXR?
Very small cancers
Pulmonary emboli
List 5 indications for ordering a CT scan of the lungs.
- To clarify ABNORMAL CXR
- Characterize PULMONARY NODULES
- Assist in DIAGNOSIS of clinical signs/sxs (cough, SOB, CP, fever)
- DETECTION and STAGING of 1*/metastatic lung neoplasms (including SCREENING for lung CA)
- Evaluate suspected MEDIASTINAL or HILAR MASSES
1mm slice, better detail
This type of CT scan is a:
High resolution (HRCT)
10mm slice, “step and shoot”, takes 25-30 minutes
This type of CT scan is a:
Conventional scan
Less detail, used for screening
This type of CT scan is a:
Low dose (LDCT)
Faster, continuous, takes <5 minutes
This type of CT scan is a;
Helical (spiral) CT
What type of CT scan helps to visualize blood vessels?
CT angiography
What 2 populations should we avoid giving CT scans to if possible? Why?
Peds: more radiosensitive, increased risk for leukemia and brain tumors with CT scans
Pregnant women: In utero exposure linked to pediatric CA mortality; ALWAYS ASK LMP PRIOR TO IMAGING!
What type of radiocontrast is used with CT? What are 3 scenarios we would use contrast for?
Iodine
Visualization of:
- Vessels
- Malignancies
- Chest trauma
What are the potential risks to consider when giving a patient radiocontrast for a CT?
- Allergic reaction (minor to severe)
- Contrast induced nephropathy (CIN)
- Development of lactic acidosis if taking glucophage (Metformin) - may require holding for 48 hrs after imaging
What are the risk factors for a pt developing an allergic contrast after receiving radiocontrast? How can you treat this prophylactically?
Risk factors: Prior rxn, hx of asthma or atopy (NOT SHELLFISH!)
Pre-treat with prednisone and diphenhydramine (Benadryl)
What are the lab values seen in a patient with radiocontrast induced nephropathy? When do sxs start presenting and when do they peak?
Increase in serum Cr >/= 0.5 mg/dL or >/= 25% from baseline
- sxs appear 24-48 hrs post exposure
- Peaks at 3-5 days
A pt with decreased kidney function should not be given radiocontrast if their:
Creatinine > 1.5 mg/dL or GFR <60
You should assess renal function prior to giving contrast if a patient presents with any 5 of the following indications:
Age > 60 yrs Hx of renal disease Hx of HTN treated with medication Hx of diabetes Taking Metformin
What has largely replaced conventional (catheter directed) pulmonary angiography?
CT Pulmonary Angiography (CTPA)
*Less invasive, less expensive, less time-consuming
What are 4 things a CTPA is useful in detecting?
- PE
- Aortic dissection
- Superior vena cava syndrome
- Identifying vascular malformations and arterial invasion by a neoplasm
What are 5 risks and limitations of a CTPA?
- May miss sub-segmental PE
- Allergy risk to contrast
- CIN from contrast
- Radiation exposure
- Body habitus >450lbs
What is the gold standard for an evaluation of a PE?
Catheter-Directed Pulmonary Angiography (“Direct PA”)
- Needle/catheter inserted into R femoral or internal jugular vein; into R side heart and pulm. arteries
- Dye injected, x-rays taken
A catheter-directed pulmonary angiography is useful when a ____ or ____ is inconclusive.
V/Q scan
CTPA
What are 5 risks of a direct pulmonary angiography?
- Bleeding or hematoma at insertion site
- Heart arrhythmia
- Allergic reaction to contrast material
- CIN from contrast
- Radiation exposure
Does a CT or MRI show a more detailed view of lung parenchyma?
CT
But MRI has no bone artifact and no ionizing radiation
What is the contrast used for MRI?
Gadolinium
You should avoid use of gadolinium if the pt’s GFR is _____, as this may cause _____.
if GFR <30ml/min
Risk of nephrogenic systemic fibrosis (skin fibrosis +/- systemic involvement); irreversible
What are 4 contraindications for use of MRI?
Implanted pacemaker or defibrillator
Metal in eye
Aneurysm clips
Cochlear implant
What are the 2 types of nuclear imaging used for evaluation of the chest?
Ventilation-perfusion scan (V/Q)
PET scan
What are 2 indications for the use of a V/Q scan?
Eval of pulmonary embolisms (best in pts with normal CXR but high suspicion for PE)
Pre-op assessment prior to lung resection (estimates post-op reserve capacity)
What does a V/Q mismatch mean?
Imbalance of blood flow and ventilation
What is the test of choice for diagnosis of a PE in pregnant women?
V/Q scan (very low dose radiation exposure)
What is one downside to V/Q scans? (think specificity, sensitivity)
Sensitive for PE but poor specificity (few false negatives, high number of false positives)
What are PET scans most useful in detecting?
- Cancer and metastases
- Effects of CA therapy
- Mediastinal imaging (superior to CT; can identify tumor in normal sized LN)
What is the radioactive substance used in a PET scan?
Fluorodeoxyglucose (FDG)
- Injected into patient
- Accumulates in tissues/organs with high metabolic activity (like cancer cells)
During a PET scan, measurements of uptake are made in SUVs (standardized uptake values). What SUV level raises possibility of malignancy?
SUV > 2.5
What are 2 major benefits to using a PET scan?
- Can detect biochemical changes BEFORE they are apparent on CT or MRI
- Radioactivity is short-lived
What is a limitation of PET scans in regards to false + and -?
False results occur with metabolic imbalances:
False (+): occur with inflammatory lesions/granulomas
False (-): occur with slow growing tumor
What are 3 indications of a thoracic ultrasound?
- Bedside detection of pleural fluid, hemothorax, or pneumothorax
- Guidance for thoracentesis
- Guidance for placement of thoracostomy tubes
What are 3 diagnostic indications for a bronchoscopy?
- Eval of pneumonia, hemoptysis, cough
- Dx of tracheoesophageal fistulas/tracheobronchomalacia
- Tissue sampling
What are 2 therapeutic indications for a bronchoscopy?
- Removal of excess mucus or foreign bodies
- ET tube placement
What are the 2 types of bronchoscopy? Which is commonly used in pts with obstruction of the trachea or a proximal bronchus?
Rigid vs Flexible
Rigid used in that scenario
What are 5 contraindications for bronchoscopy?
- Severe hypoxia
- Risk of bleeding
- Pulmonary HTN
- Severe coughing/gagging
- Tracheal stenosis
