JC13 (Surgery) - CXR Flashcards
Define size cut-off for lung mass
<3cm = nodule >3cm = mass
One nodule in one location = solitary pulmonary nodule (SPN)
Investigations for solitary pulmonary nodule (SPN)
Refer to previous CXR
1) SPN present in previous CXR:
- No growth over 2 year = likely Benign
- Interval growth = suspect malignant, proceed to CT scan
2) SPN not present in previous CXR:
- CT scan
- Bronchoscopy
- Sputum analysis
Imaging features of benign lung nodules
Benign: Round shape, well-circumscribed, smooth margin, uniform/ central calcification, Fat-containing, Minimal enhancement
Ddx infective cavitating lesion in lung (5)
Infections:
- Pulmonary Abscess: intermediate to thick wall, peripheral contrast enhancement, necrotizing center, +/- fluid level
- Septic Emboli (pathogens cause thrombosis in peripheral pulmonary capillaries): multiple peripheral nodular or wedge-shaped opacities with a broad base against the pleura
- Mycobacterium tuberculosis infection: upper lobe cavitary disease (immunocompetent) or lower lung zone disease, adenopathy, and pleural effusions (immunocompromised/ children)
- Non-tuberculous Mycobacterial (NTMB) Infection (e.g. M. avium-intracelluare and M. kansaii): similar upper zone TB but no hemoptysis
- Aspergillosis/ Aspergillus fumigatus: ground glass halo, fungal ball lesions that appear cavitary, crescent-shape air collection
CT Lung:
- Types
- Section width
- Function
Volumetric/ Helical/Spiral CT scan
- Used with IV contrast to enhance nodule characteristics
- Timing of IV contrast is determined by different pathologies (e.g. timing to contrast for PE is different from lung cancer
- Used for examining lung mass (no section width that can miss lesions)
High resolution CT scan
- No contrast used
- Used for interstitial lung disease
- 1-2mm slices taken 10mm apart
Use Hounsfield units to define nodule malignancy in contrast CT thorax.
Contrast CT:
- Nodule enhanced:
a) >25HU = malignant
b) Between 15 and 25 HU = Indeterminate
c) <15HU = Benign - Nodule not enhanced: Benign
Imaging features of malignant lung nodules
Malignant: Lobulated shape, spiculated margins (due to rapid growth) eccentric/ speckled calcification Pleural retraction Marked enhancement Heterogeneous
An solitary lung nodule has enhancement of 20HU in contrast CT. Is this malignant or benign?
Indeterminate
- Nodule enhanced:
a) >25HU = malignant
b) Between 15 and 25 HU = Indeterminate
c) <15HU = Benign
Plan of action after finding indeterminate nodule in lung
Close follow-up with CXR/ CT (3-6 months)
Percutaneous or transbronchial biopsy/ Resection to find cause
Investigations for suspected lung carcinoma
Contrast CT scan: TNM staging +/- biopsy at thorax and upper abdomen
Bronchoscopy: biopsy + BAL
Post-bronchoscopy sputum analysis
Name of lung tumor that is associated with upper limb motor deficit?
Structures that may be invaded?
Pancoast tumor
brachial plexus
Erosion of rib and left transverse process
soft tissue of back
3 uses of CT in management of lung cancer?
1) Staging, determine operability
2) Radiation planning, find disease extent, location and limit collateral damage
3) Re-evaluate treatment response
Limitation of contrast CT in examining mediastinal LN
Hard to assess:
Size
Cause of LN enlargement (inflammation or metastasis?)
Microscopic metastasis
Indeterminate chest wall or mediastinal invasion
List 5 ancillary investigations for lung cancer
Flexible bronchoscopy
Mediastinoscopy + biopsy
Transesophageal USG + biopsy
Thoracotomy + nodal sampling
PET scan (18-FDG)
Biopsy techniques for proximal vs peripheral lung lesions
Proximal lesion (close to hilum):
- Saline washing and brushing for microscopy and cytology
- Biopsy under direct vision for histology
Peripheral lesion: not visualized directly
- BAL for microscopy and cytology
- Transbronchial biopsy for histology
Indication for MRI in imaging lung cancer
Superior sulcus lung tumors* specific use **
Chest wall and brachial plexus invasion (e.g. Pancoast tumor)
1 advantage and 1 disadvantage of PET/CT scan for lung cancer
18-FDG for hypermetabolic lesions:
Adv: detect occult metastasis with high sensitivity
Disadv.
High sensitivity but low specificity, false positive rate high (e.g. TB nodules)
3 advantages of CT as first-line imaging for lung cancer
Favorable cost
Quick
Allow simultaneous exam intrathoracic and abdominal organs
Ddx diffuse lung nodules* (categorize into miliary, cavitory and calcific nodules)
miliary nodules:
- miliary tuberculosis
- silicosis
- pulmonary sarcoidosis
- diffuse pulmonary metastases
- diffuse panbronchiolitis
cavitatory nodules
- septic pulmonary emboli
- cavitating metastases
- multiple cavitating infections
calcific nodules
- tuberculosis
- silicosis
- calcified pulmonary metastases
Interstitial lung disease
- Type of scan indicated
- Interval width
High resolution CT, no contrast - High spatial resolution, reduced radiation
1mm sections at 10mm intervals
Functions of HRCT in evaluation of diffusion lung lesions?
Characterize disease for diagnosis
Define location and extent
Localize site for biopsy
Post-treatment evaluation
Typical Hounsfield Units of air, water, fat, soft tissue, and calcified matter
Air = -1000 Water = 0 Fat = 20 Soft tissue = 30-50 Calcification = >150
Ddx systemic diseases that cause cavitating lung nodules
Granulomatosis polyangiitis: autoimmune vasculitis in respiratory tract and kidneys
Rheumatic nodules: necrobiotic nodule at periphery or subpleural space
Sarcoidosis (rare <1%): round/ oval nodules in peri-hilar/ peripheral areas
Malignancies: Pulmonary metastasis from SCC (e.g. from GIT, breast CA, sarcomas, Adenocarcinomas…)
Cystic lung diseases by pneumocystis jirovecii: Langerhgans cell histiocytosis, lymphangioleiomyomatosis (LAM), lymphocytic interstitial pneumonia (LIP)
Ddx Solitary Pulmonary Nodules
Neoplastic - Benign:
- pulmonary hamartoma
- pulmonary chondroma
- primary pulmonary meningioma: rare
malignant
- bronchogenic carcinoma
- solitary pulmonary metastasis
- lymphoma
- carcinoid tumors
inflammatory
- granuloma
- lung abscess
- rheumatoid nodule
- pulmonary inflammatory pseudotumor
- small focus of pneumonia: round pneumonia
congenital
- arteriovenous malformation
- lung cyst
- bronchial atresia with mucoid impaction
miscellaneous
- pulmonary infarct
- intrapulmonary lymph node
- mucoid impaction
- pulmonary hematoma
- pulmonary amyloidosis
Mimics of solitary pulmonary nodules
nipple shadow
cutaneous lesion (e.g. wart, mole)
rib fracture or other bone lesion
vanishing pseudotumor of congestive heart failure
summation of markings
radiological artifact
CXR Technical Quality checklist
Projection: AP or PA, check for marking for AP, check if scapulae overlies the lungs in AP, Cardiac shadow might appear magnified in AP
Orientation: Check L/R markings, beware of dextrocardia and lung pathologies with mediastinal shift
Rotation: Check medial ends of both clavicles are equidistant from the vertebral spinous process. If one end is nearer than the other, that side will appear whiter
Penetration: Vertebral body just seen through the lower cardiac shadow
Degree of inspiration: Check right hemidiaphragm is between 5th and 7th rib, count 6 anterior ribs and 10 posterior ribs above the diaphragm
CXR basic anatomical structure checklist - AP/ PA film
Lung fields
- Equal transradiancy
- Horizontal fissure should from from 6th rib in the axillary line to the hilum
- Check for volume loss in one or both sides of the lungs
- Check for discreet or generalized shadows
Hilum
- Left hilum should be lower than right hilum
- Difference <2.5cm
- Compare shape, density, concavity of each side
Heart
- Check cardio-thoracic ratio <0.5
Mediastinum
- Clear edge
- Fuzzy edge indicates nearby consolidation or collapse
Diaphragm
- Right hemidiaphragm higher than left, <3cm
- Outline smooth
- Below diaphragm: any free gas, dilated bowels
Costophrenic angle
- Clear, well-defined
Trachea
- Central, slight deviation to right at aortic knuckle
Bones
- Scapulae, vertebrae, ribs
- Check for density changes and fractures
Soft tissue: any enlargement
CXR anatomical structure checklist - Lateral film
Diaphragm
- Right hemidiaphragm streched across whole throax, passes through heart border
- Left hemidiaphragm disappear towards posterior border of heart
- Double check with AP/PA film, check if gastric air bubble is the same distance from left hemidiaphragm on lateral film
- Check costophrenic angles (e.g. pleural effusion blunting angles)
Lung fields
- Check equal transradiancy, check lesions
Retrosternal space
- Anterior mediastinal mass will obliterate the space and turn it white
Position of horizontal fissure
- Normally passes from midpoint of the hilum to anterior chest wall
- Displaced fissure indicate SOL
- Oblique fissure should pass from T4/5 vertebral through hilum to anterior third of diaphragm
Hilum density, check lesion
Vertebral bodies
- Normally more translucent more caudally
- Check same size, shape, density, outline
- Check collapse, lesion
Localizing lesion on CXR
Right lung:
Zones:
- Upper = above right anterior border of 2nd rib
- Middle = between 2nd and 4th rib
- Lower = between 4th rib to diaphragm
Silhouette sign
- Obscures cardiac shadow = right middle lobe
- Obscures diaphragm = right lower lobe
Fissure
- Posterior to oblique fissure = right lower lobe
- Anterior to oblique fissure = right middle or upper lobe
- Above horizontal fissure = right upper lobe
Left lung:
- Posterior to oblique fissure = Left lower lobe
- Anterior to oblique fissure = Left upper lobe
