Imaging of lung cancer

Question 1

Diagnostic pathway of lung cancer

Answer 1

Discover lung nodule/mass (X-ray, CT)
Characterize abnormal tissue (CT)
Determine if surgically removable (CT, MRI, PET)
Search for distant metastatic lesions

Question 2

X-ray detection of lung cancer

Answer 2

Soft tissue displaces air

iv contrast enhancement
identifies encasement, invasion or clot in vessels 3 mm in diameter / larger
microscopic (<3mm)
- separate lung lesions that are vascular (active inflammation/cancer) from avascular (post-inflammatory)

Question 3

Limitations of chest radiographs (lung cancer)

Answer 3

projection image - cannot be read reliably
characterize density of lesion
identify enlarged lymph nodes
detect chest wall, mediastinal or cardiac invasion
detect metastasis

Question 4

CT imaging in lung cancer

Answer 4

10x contrast resolution > X-ray

Question 5

X-ray definitely benign lesions

Answer 5

Unchanging in size over 5 years
< 2 cm in diameter AND
completely calcified using CT (previous infection)
Focal areas of fat using CT (hamartoma, common fat-containing lesion in parenchyma)

Question 6

X-ray: probably benign lesions

Answer 6

<2cm in diameter AND
smooth margins, solitary nodule (previous granuloma)
Satellite nodules (likely previous/active infection)

Question 7

X-ray: probably malignant

Answer 7

> 2 cm in diameter
spiculated margins
bubbles/central lucency, airways running through lesions

Question 8

Staging using CT

Answer 8

Unresectable cancer: IIIb or higher

• mediastinal invasion
• contra-lateral lung mass or nodes
• malignant pleural effusion
• spinal cord invasion
• distant mestatic lesions

Question 9

MRI imaging of lung cancer - advantages

Answer 9

enhanced contrast sensitivity > CT

• T1, T2 relaxation, proton densitiy, flow
• imaging in coronal, sagittal and oblique planes

Question 10

MRI imaging in lung cancer- disadvantages

Answer 10

Noisy - limited signal to noise ratio
Minimal signal from normal lung
Motion artefact

Question 11

Chest wall invasion criteria (imaging)

Answer 11

CT criteria:
- bone destruction
- mass extension into chest wall
- pleural thickening
BUT many lung cancers invade focally and do not cause above changes
pleural thickening may be reactive and not cancerous

CT may be misleading - MRI useful

Question 12

Metastatic nodes in lung cancer (imaging)

Answer 12

CT/MRI same

PET better

Question 13

PET attributes

Answer 13

fluorodeoxyglucose (FDG) -metabolically active regions
active inflammation - false positive
low grade tumours - false negative
fuse with CT for PET/CT

good for distant metastases