Question

The dose of radiation required for development of the haematological (bone marrow) syndrome is?

• A. 2 to 5 Gy
• B. 10 Gy
• C. 100 Gy
• D. 200 Gy

Hint:

Bone marrow stem cells are highly radiosensitive, so this syndrome needs the lowest dose.

Answer 1

The Correct Option is A

Step 1: Recall the acute radiation syndromes.
Acute radiation syndrome occurs in dose-dependent stages: the haematopoietic (bone marrow) syndrome at lower doses, the gastrointestinal syndrome at intermediate doses, and the cerebrovascular (central nervous system) syndrome at the highest doses.

Step 2: Dose threshold for the haematological syndrome.
The haematopoietic syndrome appears with whole-body doses in the range of roughly 2 to 5 Gy (up to about 10 Gy). At these doses the radiosensitive bone marrow stem cells are depleted, leading to pancytopenia with anaemia, infection and bleeding.

Step 3: Compare with the higher-dose syndromes.
The gastrointestinal syndrome occurs at higher doses (about 5 to 10 Gy and above), and the cerebrovascular or CNS syndrome occurs at very high doses (above roughly 20 to 50 Gy, far higher than 100 to 200 Gy in the older teaching frameworks). The lowest threshold among the listed options corresponds to the marrow syndrome.

Step 4: Conclusion.
The haematological syndrome develops at a whole-body dose of about 2 to 5 Gy.

Correct answer: 2 to 5 Gy.