Imaging the lung

Question 1

Strengths of CT scans

Answer 1

Cross sectional

Great spatial resolution

Widely available

Question 2

Weaknesses of CT scans

Answer 2

Ionising radiation

Limited soft tissue contrast

Question 3

CT scans

Answer 3

Computed tomography- A type of X-ray machine

An X-ray beam is rotated around a patient and the beams are detected by detectors around the patient.

Allows greater detail that normal X-rays

X-rays taken in ‘slices’. The thinner the sections, the greater the resolution- usually 5-8mm.

Question 4

Primary lobule of lung

Answer 4

Smallest unit of the lung: 6-10 mm.

Question 5

Secondary pulmonary lobule

Answer 5

Functional unit of the lung: 5-20 mm.
Composed of a number of acini.

Contains:
Pulmonary veins and lymphatics within the connective tissue septum.

Acinus which arises from the terminal bronchiole.

Primary lobule arises from last respiratory bronchiole.

Question 6

Radioactive isotopes used to obtain ventilation distribution images in lungs.

Answer 6

Gas: Xenon-133, Krypton-81m.

Aerosol: Tc99m-DTPA

Radioactive dry carbon particles.

Question 7

Producing an image of lung blood flow.

Answer 7

Injection UV of 200-500k particles, 16-90 microns in diameter.

Does not affect pulmonary circulation massively, only occludes <1%.

Question 8

Hilar point

Answer 8

The ‘V’ shaped point where the lower lobe pulmonary arteries cross with upper lobe pulmonary veins.

When it is asymmetrical, indicates a pathology.

Question 9

What does a raised hilum indicate?

Answer 9

Upper lobe collapse/ fibrosis.

Question 10

What does an obscured hilum indicate?

Answer 10

Lymphadenopathy

Tumour

Mediastinal mass

Question 11

Hyperexpansion

Answer 11

This happens in the chest wall.

In a CXR there will be more than 6 anterior ribs above the dome of the diaphragm.

Seen in:
Young children
Asthmatics
COPD
Emphysema

Question 12

Cardiomegaly

Answer 12

Enlarged heart.

In CXR, cardiac-thoracic ratio is >0.5

Causes:
LVHF
Pericardial effusion

Dilated cardiomyopathy.

Question 13

Interventricular septum

Answer 13

Receive blood mainly from circumflex branch of LCA

Therefore occlusion in circumflex causes MI in this septum.

Question 14

Red and white cell scanning

Answer 14

Scans for the distribution of red or wbc in the body- uses radioactive markers.

Red scan- mainly concentrated in the heart, liver and kidneys

White scan: Spleen, bone marrow, RE system.

Question 15

Branches of the arch of aorta

Answer 15

Right brachiocephalic trunk

Left common carotid artery

Left subclavian artery

Question 16

Branches of the left subclavian artery

Answer 16

L. internal thoracic artery.

L. vertebral artery

L. thyrocervical artery

Costocervical artery