Equivalent number of doses of radiation for most commonly requested investigations. Dose for chest x ray used as single unit dose of radiation. Figures are numbers (percentage) of doctors with correct answer for each investigation

Radiological investigation
Equivalent No of chest x rays
No of correct answers (n=130)

Abdominal x ray
75
2 (1.5)

Lumbar spine x ray
120
3 (2)

Thoracic spine x ray
50
4 (3)

Barium swallow
100
6 (5)

Peroperative cholangiogram
65
3 (2)

Fixation of fractured neck of femur
45
10 (8)

Ultrasound of abdomen
0
124 (95)

CT of abdomen
400
8 (6)

Spiral CT of abdomen
300
9 (7)

MRI of abdomen
0
119 (92)

MRI of knee
0
119 (92)

MRI of spine
0
119 (92)

Leg arteriogram
400
0

Renal arteriogram
80
1 (1)

Thyroid isotope scan
50
8 (6)

White cell scan
150
2 (1.5)