Oral Exam - Thoracic Flashcards
Proposed PE categories
- PE likely/present: High probability scan, with inclusion of a single-segmental VQ mismatch in the high probability category
- PE unlikely/absent: Normal and very low probability scans
- Non diagnostic for PE: All others
PCP findings
Ga-67
– Early infection: Intense diffuse pulmonary uptake of Ga-67; no nodal uptake; may precede radiographic and physiologic abnormalities
TB findings/MAC findings
Patchy/lobar pulmonary plus hilar nodal Ga-67 uptake
Kaposi sarcoma
No Ga67 uptake
Tl-201 and Ga-67 combined imaging
○ PJP: Thallium negative/gallium positive; diffuse
pulmonary uptake
○ Mycobacterial infection: Thallium negative/gallium
positive; mediastinal uptake
○ Bacterial pneumonia: Thallium negative/gallium positive;
focal pulmonary uptake
- Kaposi sarcoma: Thallium positive/gallium negative;
○ Lymphoma: Thallium positive/gallium positive; pulmonary and mediastinal uptake
Ga-67 protocol
□ Physical t1/2: 78 hours
□ Principal photopeaks: 93 keV (40%), 184 keV (24%),
296 keV (22%), and 388 keV (7%)
□ Excretion: 10-25% by kidneys in first 24 hours,
followed by gastrointestinal tract
– Dose: 4-6 mCi IV
– Image acquisition
□ Large field-of-view multipeak gamma camera with medium-energy parallel hole collimator
□ Anterior and posterior projections obtained 24-72 hours after injection
□ 250k-1miltotalcountsforchest
Lambda sign
Ga-67 or F-18 FDG PET/CT
symmetric hilar and right paratracheal activity
Panda sign
Ga-67 or F-18 FDG PET/CT
symmetric lacrimal and parotid gland activity
Defect size on VQ
– Large: > 75% of segment
– Moderate: 26-74% of segment
– Small:<25%ofsegment
2 moderates = large
Concentric pleural uptake
Asbestos related pleural disease Mesothelioma Metastases Primary pleural malinancy Pleurodesis
FDG avid effusion
80% chance malignancy
HOA cause
Bronchogenic carcinoma Pulmonary metastases Other benign thoracic tumours Mesothelioma Bronchiectasis Lung abscess
Unilateral large matched defect
Low probability
Ddx: Central PE Hilar mass Severe unilateral parenchymal disease Swyer james Hypoplastic PA
Bilateral upper lobe large mismatched perfusion defects
Consider artifact from MAA injection - patient should be supine
High prob PE
Asthma/COPD
Kidney activity on MAA perfusion study
R-L shunt
Free pertechnetate
Recent study
Causes R-> Shunt
Intracardiac (PDA, ASD)
Pulmonary AVMs
Cirrhosis resulting in intrapulmonary shunts
Ddx high prob study
2 large or equivalent mismatched perfusion defects
Ddx:
Pulmonary vasculitis
Mediastinal adenopathy
Triple match defect (PIOPED II)
Low prob in upper and mid lung
Intermediate prob in lower lung
pneumothorax on ventilation scan
Activity on periphery of pleuaral cavity
Ddx pleural fluid/thickened fissures on ventilation scan
Tumour microemboli
Lymphangitic disease
Pleural fluid
Small subsegmental mismatched defecgt
Low probabilitiy Ddx: Atelectasis Bronchitis Asthma Pleural fluid Pneumonia
Large matched defects
Obstruction from: Neoplasm Mucous plugging Foreign body Pneumonectomy Pulmonary atresia
Reactive from: CHF COPD Asthma Pneumonia Swyer James
