1 Pulmonary Diagnostic Imaging

Question 1

Pulmonary diagnostic imaging that exposes the patient to ionizing radiation

Answer 1

Chest Radiography (CXR)

Computed Tomography (CT)

Pulmonary Angiography (CTPA/Direct)

Nuclear Scanning
• V/Q scan
• PET scan

Question 2

Pulmonary diagnostic imaging that DOESN’T expose the patient to ionizing radiation

Answer 2

Ultrasound

Magnetic Resonance Imaging (MRI/MRA)

Bronchoscopy

Question 3

CTs account for ____% of average ionizing radiation exposure each year

Answer 3

24%

Question 4

Often the initial study to evaluate respiratory symptoms

Answer 4

Chest X-Ray

X-ray beam penetrates through the body and provides images of structures in and around the thorax (lung parenchyma, pleura, chest wall, diaphragm, mediastinum, and hilum)

Question 5

On CXR, air appears ____, fat ______, and bone ______.

Answer 5

Air = black
Far = dark gray
Bone = nearly white

Question 6

Indications for chest x-ray

Answer 6

Shortness of breath

Persistent cough

Hemoptysis

Chest pain or injury

Fever

Question 7

What views are utilized when taking chest x-rays?

Answer 7

Posterior-anterior (PA)
Anterior-posterior (AP)
Lateral
Decubitus

Question 8

Combo of CXR views most often used

Answer 8

PA and lateral

AP is used if bedridden (but may make heart look bigger than it actually is)

Question 9

The ABCDEFs of viewing chest X-rays

Answer 9

Airway (trachea, bronchi)
Bones (ribs, clavicle)
Cardiac (borders, cardiomegaly)
Diaphragm
Edges (look for pneumothorax or effusion)
Fields of lungs (look for infiltrates, nodes)

Question 10

Which CXR view allows for best visualization of the right lower lobe?

Answer 10

Lateral

Because the RLL is mostly posterior, very little of it can be visualized from a PA view

Question 11

What is an Apical Lordotic view?

Answer 11

Variation on an AP view, where patient’s feet are some distance from the film and the lean back upon it.

Indicated when TB is suspected because it gives the best view of the apex of the lungs, where TB typically starts

Question 12

Example of use of the lateral decubitus view on CXR

Answer 12

Subpulmonic effusion

The PA film shows an apparently elevated right diaphragm

On the decubitus view, the effusion flows up along the side of the lung

Question 13

What are the primary benefits of CXRs?

Answer 13

Non-invasive

Low radiation exposure

Inexpensive

Convenient - Imaging is fast, easy, and particularly useful in emergency Dx and Tx

Widely available (esp with portable units)

Question 14

Though uncommon to see, a Hampton’s Hump on CXR indicates…

Answer 14

PE - it’s an area of ischemia due to the infarct

Question 15

Risks and Limitations of CXR

Answer 15

Radiation exposure
• 0.1 mSv, minimal but cumulative
• PA/LAT, about what you receive from background radiation in 10 days

Pregnancy - some exposure but smaller risk than CT

Some conditions of the chest cannot be detected (ie very small cancers, pulmonary emboli)

Question 16

Why might you order a CT?

Answer 16

Clarify an abnormal CXR

Help diagnose the cause of clinical SSx (SOB, cough, CP, fever)

Characterize pulmonary nodules

Detection and staging of primary and metastatic lung neoplasms

Evaluate suspected mediastinal or hilar masses

Question 17

Who should get a CT screening for lung cancer?

Answer 17

55-80 year olds with a 30 pack year history and currently smoke or quit within the past 15 years

Question 18

Types of CT scans

Answer 18

Conventional - 10 mm slice, “step-and-shoot”, 25-30 min

Helical - aka spiral CT, faster, continuous, <5 min

High Resolution (HRCT) - better detail, 1mm slice

Low Dose CT - usually used for lung cancer screening, but less detail

CT Angiography

“Multidetector” or “multislice CT” - capable of conventional and helical scans, but 64x faster (though with higher radiation)

Question 19

How does bronchiectasis appear on CT?

Answer 19

Thickening/dilation of airways

Question 20

What does subcutaneous emphysema sound like?

Answer 20

Rice crispiest

Question 21

Benefits of CT

Answer 21

Fast, widely available

Detailed images

Real-time imaging useful for biopsies

Can be performed even if patient has an implanted device

Less expensive and less sensitive to patient movement than MRI

Question 22

Risks/Limitations of CT

Answer 22

Radiation exposure (~8 mSv or 80 times that of Xray) - about the same a person receives from background radiation in three years

Increased CA risk

Fetal exposure during pregnancy

Problems associated with contrast (allergy, renal problems)

Body habitus >450lbs may not fit in machine

Question 23

What’s special about kids and CTs?

Answer 23

Kids are more radiosensitive than adults

CT has increased risk of leukemia and brain tumors

Radiation risk compounded by longer lifespan

Question 24

What do we need to know about pregnant women and CTs?

Answer 24

In uterine exposure linked to pediatric cancer mortality - always ask LMP prior to imaging

Question 25

What type of contrast does CT use?

Answer 25

Iodine Used to enhance differences in densities of various structures - ie a large blood vessel with a tumor encasing/constricting it

Question 26

When is CT with contrast needed?

Answer 26

Masses, cancer, metastatic disease, obstructive processes, PE or dissection (CT angiography)

Question 27

When do we want a CT WITHOUT contrast

Answer 27

High resolution CT for evaluation of diffuse lung disease and to follow up known pulmonary nodules

Question 28

Special risks of CT with contrast

Answer 28

Allergic reaction (mild-moderate vs major) Potential for contrast induced nephropathy Development of lactic acidosis if taking Glucophage (Metformin) - consider holding metformin for 48 hours after imaging

Question 29

Tell me more about iodine contrast allergies...

Answer 29

Reaction develops within 5-60 min of administration of contrast SSx - flushing, Pruitt is, urticaria, angioedema, bronchospasm and wheezing, stridor, hypotension, loss of consciousness Risk factors - prior reaction, asthma, atopy Can pre-treat with prednisone and diphenhydramine (Benadryl)

Question 30

Is a shellfish allergy a contraindication for CT contrast?

Answer 30

Nope.

Question 31

Contrast induced nephropathy is defined as ...

Answer 31

Serum creatinine >25% from baseline or >0.5 mg/dL Usually reversible Best treatment is prevention Caution using contrast in patients with impaired kidney function

Question 32

In whom should we be concerned for development of contrast induced nephropathy

Answer 32

If Creatinine >1.5 mg/dL or GFR <60 Age >60 Hx of renal disease, HTN treated with meds, DM (esp if taking metformin) Use alternative - either CT w/o contrast, MRI w/o gadolinium, or U/S

Question 33

Patients taking metformin and CT contrast...

Answer 33

If eGFR ≥ 30 ml/min, metformin does not need to be withheld If Acute kidney injury or severe CKD with eGFR <30 ml/min - temporarily hold metformin when contrast administered x 48 hours, resume only after re-evaluation of renal function

Question 34

When do we use angiography?

Answer 34

To assess vasculature in the body • Brain, kidneys, pelvis, legs, lungs, heart, neck • Injection/timing controlled, dye is where you want it during the scan Performed in conjunction with imaging modalities • CT —> CTA • MRI —> MRA • X-ray with catheter (direct/conventional)

Question 35

Imaging procedure that provides anatomical detail of blood vessels and is useful for suspected pulmonary embolism, aortic dissection, and superior vena cava syndrome

Answer 35

CT Pulmonary Angiography (CTPA) Identifies vascular malformations and assesses pulmonary arterial invasion by a neoplasm

Question 36

Benefits of CTPA

Answer 36

Has largely replaced conventional (catheter-directed) pulmonary angiography If surgery is warranted, can provide precise anatomical guidance Less invasive, less expensive, and safer compared to conventional angiography

Question 37

Risks/Limitations of CTPA

Answer 37

Can miss sub-segmental PEs Allergy to contrast material (iodine) Nephrotoxicity from contrast Radiation exposure (10-15 mSv) Body habitus (>450lbs)

Question 38

Gold standard in the evaluation of PE

Answer 38

Direct pulmonary angiography CTA is more useful now but this is still the gold standard

Question 39

How is direct pulmonary angiography performed

Answer 39

Needle/catheter inserted into right femoral or internal jugular vein —> R side heart —> pulmonary arteries Dry injected, x-rays taken Used if V/Q scan or CTPA inconclusive and still a high clinical suspicion Invasive and expensive

Question 40

Risks of direct pulmonary angiography

Answer 40

Bleeding or hematoma at insertion site Heart arrhythmia Allergic reaction to contrast Impaired kidney function (though usually reversible) Radiation exposure (5 mSv)

Question 41

How are MRIs used in pulmonary disease?

Answer 41

Limited usefulness Hilar or mediastinal densities, sulcus tumors, possible cysts and lesions of the chest wall

Question 42

Who cannot receive an MRI?

Answer 42

Patients with allergy to iodinated contrast or renal disease (GFR <60)

Question 43

Benefits to MRI

Answer 43

No bone artifact as with CT No ionizing radiation

Question 44

Compared to Chest CT, MRI has _______ detailed view of lung parenchyma and __________ special resolution

Answer 44

Less detailed, diminished special resolution

Question 45

Contrast material used for MRI and MRA

Answer 45

Gadolinium

Question 46

Limitations of MRI/MRA

Answer 46

Patient must remain still Claustrophobia Body habitus Risk of nephrogenic systemic fibrosis (irreversible scarring) - avoid use of gadolinium if GFR < 60

Question 47

Contraindications of MRI/MRA

Answer 47

Pacemaker or defibrillator Metal in eye Aneurysm clip Cochlear implant Joint replacements aren’t ferrous and are generally safe

Question 48

Nuclear imaging study used to evaluate for PE

Answer 48

Ventilation-Perfusion (V/Q) scan Also used for pre-op assessment prior to lung resection

Question 49

Imbalance of blood flow and ventilation is called

Answer 49

V/Q mismatch

Question 50

Radioactive material used in V/Q scans

Answer 50

Technicium-99 and Xenon gas

Question 51

The two phases of V/Q scans

Answer 51

IV Phase - Technetium-99m (labeled to human albumin) is injected and follows distribution of blood flow (PERFUSION) Inhalation Phase - radio-labeled Xenon gas demonstrates distribution of VENTILATION

Question 52

If a patient has a high probability of PE but a normal CXR, you should...

Answer 52

Perform V/Q scan to assess for mismatch. Absence of perfusion with normal ventilation indicates PE.

Question 53

Benefits of V/Q scan

Answer 53

Allergic reaction to radiopharmaceutical is rare Low-dose radiation (2-2.5 mSv) Remains test of choice for diagnosis of PE in pregnant women Useful in estimating post-op reserve capacity for patients undergoing lung resection

Question 54

Limitations of V/Q scan

Answer 54

Sensitive for Dx of PE but poorly specific (PNA or asthmas might be positive too) Few false negatives but high number of false-positives Best utilized in those with a normal CXR w/ high suspicion of PE No absolute contraindications

Question 55

Acquisition of physiologic images based on the detection of radiation emitted from fluorodeoxyglucose (FDG)

Answer 55

Positron Emission Tomography (PET) FDG - radioactively labeled glucose injected into patient and accumulates in tissues/organs with high metabolic activity (ie cancer cells)

Question 56

In PET scans, measurements of the uptake of FDG are made in ________.

Answer 56

Standardized Uptake Value (SUV) SUV > 2.5 raises possibility of malignancy

Question 57

Uses of PET scan

Answer 57

Most often used to detect cancer Useful to evaluate for metastasis from primary site Used to examine the effects of cancer therapy (can detect recurrence in previously irradiated, scarred areas of the lung)

Question 58

Benefits of PET scans

Answer 58

Can detect biochemical changes of anatomy before they are apparent with CT/MRI However, now being combined with CT or MRI to give anatomic and metabolic info Radioactivity is short lived

Question 59

Limitations of PET scans

Answer 59

Radiation exposure ~14 mSv False results occur with metabolic imbalances • False (+) inflammatory lesions - granulomas from Cocci and Histo • False (-) with slow growing tumors Time-sensitive - radioactive substance decays quickly High cost

Question 60

How is ultrasound used in pulmonary diagnostics?

Answer 60

Limited use in evaluation of lung parenchyma Indications include: • Bedside detection of pleural fluid or PNA • Guidance for thoracentesis • Guidance for placement of thoracostomy tubes Benefits - no ionizing radiation, portable

Question 61

What is the FAST exam?

Answer 61

Focused Assessment using Sonography in Trauma

Question 62

“Seashore sign” on thoracic ultrasound indicates...

Answer 62

Normal condition - Positive lung motion

Question 63

“Barcode” or “stratosphere sign” on thoracic ultrasound indicates

Answer 63

Abnormal finding - no lung motion

Question 64

Diagnostic and therapeutic indications for bronchoscopy

Answer 64

Evaluation of PNA, hemoptysis, cough Dx of tracheoesophageal fistulas and tracheobronchomalacia Tissue sampling Removal of excess mucus or FBs ET tube placement

Question 65

___________ is most commonly used in patients with obstruction of trachea or a proximal bronchus (for removal of FB)

Answer 65

Rigid bronchoscopy

Question 66

Benefits of bronchoscopy

Answer 66

Safe procedure with very low complication rates (0.08-6.8%) • Nasal discomfort, sore throat, mild hemoptysis • Complications are usually minor (hemorrhage, pneumothorax, hypotension, arrhythmia) • Most occur during or within first few hours post-procedure

Question 67

Contraindications for bronchoscopy

Answer 67

Severe refractory hypoxia Risk of bleeding (anticoagulants, coagulopathy) Risk of respiratory and CV decompensation (asthma or COPD exacerbation, current or recent MI, poorly controlled CHF, life threatening arrhythmias)