Basics of Radiology of Thorax

Question 1

Introduction to Radiology
Q: What is radiology?
Q: Who discovered X-rays and when?

Answer 1

A: A branch of medical science that deals with radiant energy to visualize internal structures.
A: Wilhelm Roentgen in 1895.

Question 2

Relative Densities in X-rays
Q: What are the five main densities seen on an X-ray?

Answer 2

A:

-Air/Gas – Black (e.g., lungs, bowel)
-Fat – Dark grey (e.g., subcutaneous fat)
-Soft Tissue/Water – Light grey (e.g.,
heart, muscles, blood vessels)
-Bone – Off-white (most dense)
-Metal/Contrast Material – Bright
white (e.g., foreign bodies, contrast dye)

Question 3

Chest X-ray Views
Q: What are the three main views of a chest X-ray?
Q: How many ribs should be visible on a good inspiration chest X-ray?

Answer 3

A:
Anteroposterior (AP) – Used for immobilized/non-cooperative patients
Posteroanterior (PA) – Standard position with full inspiration
A: 6 anterior ribs or 10 posterior ribs.

Question 4

How to Read an X-ray
Q: What are the key steps to reading a chest X-ray?

Answer 4

A:

-Check patient details – Name, age,
sex
-Identify the view – AP, PA, or lateral
-Examine the trachea – Midline or
deviated
-Assess the lungs – Masses,
infiltrates, costophrenic angles
-Check pulmonary vessels –
Enlarged?
-Examine the hilum – Masses or
abnormalities
-Assess the heart – Size and shape
-Check pleura – Effusion,
calcifications
-Assess bones – Fractures or masses

Question 5

Abnormalities in Chest X-ray
Q: What does an increased liquid density indicate?
Q: What does increased air density suggest?
Q: What is the “Silhouette Sign”?

Answer 5

A:
Generalized: Diffuse alveolar fluid
Localized: Consolidation, mass
A: Localized or diffuse airway obstruction.
A: The loss of a normal border of an intrathoracic structure due to an adjacent pulmonary density.

Question 6

Trachea & Lungs
Q: What are the possible tracheal positions on an X-ray?
Q: What structures are found in the lung hilum?

Answer 6

A:

Normal – Midline
Deviated to the left – Possible right lung collapse or mass
Deviated to the right – Possible left lung collapse or mass
A: Pulmonary arteries and veins.

Question 7

Heart in Chest X-ray
Q: How should the heart be positioned in a normal chest X-ray?
Q: What forms the borders of the heart?

Answer 7

A:

2/3 on the left side
1/3 on the right side
A:

Left border: Left atrium & left ventricle
Right border: Right atrium
Anterior heart (not seen in PA view): Right ventricle

Question 8

Cardio-Thoracic Ratio (CTR)
Q: What is the normal cardio-thoracic ratio (CTR)?
Q: How is CTR measured?

Answer 8

A: Less than 50% (Heart width should be less than half of the thoracic width).

A:
Cardiac width: Measured at the widest points of the heart.
Thoracic width: Measured at the widest inner rib points.

Question 9

Soft Tissues & Bones in X-ray
Q: What soft tissue structures should be examined in a chest X-ray?
Q: What bones are visible in a chest X-ray?

Answer 9

A:

Breast shadows
Supraclavicular areas (for enlarged nodes)
Axillae
Surgical emphysema under the skin
A: Ribs, clavicle, lower cervical and thoracic spine, scapula, humerus (if included).

Question 10

Mach Band Effect
Q: What is the Mach band effect?

Answer 10

A: An optical illusion where a thin black line appears around the lateral heart margins.

Question 11

Evaluation of Abnormalities
Q: What steps are taken to evaluate an abnormal chest X-ray?

Answer 11

A:

Identify abnormal shadow
Locate the lesion
Identify the pathology
Determine the cause
Confirm with further imaging (e.g., contrast, MRI)