Question:easy
The Hounsfield unit (HU) is a measure used in which imaging modality?
The Hounsfield unit (HU) is a measure used in which imaging modality?
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Hounsfield scale measures X-ray attenuation in one cross-sectional modality.
Updated On: Jun 24, 2026
- CT
- MRI
- PET
- USG
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The Correct Option is A
Solution and Explanation
Step 1: The question tests which scanner expresses tissue density numerically. The relevant unit, the Hounsfield unit, was introduced by Godfrey Hounsfield, the developer of computed tomography.
Step 2: In CT, each pixel is given a number proportional to how strongly that tissue attenuates the X-ray beam relative to water. Water is fixed at 0 HU as the reference point, air sits near -1000 HU, and compact bone is strongly positive. These numbers map directly onto the displayed greyscale.
Step 3: Ruling out the rest: MRI is reported as signal intensity, PET is read as standardised uptake values of an injected tracer, and ultrasound is based on echogenicity of reflected sound. None of these adopts the Hounsfield scale.
Step 4: Hence the Hounsfield unit belongs to CT scanning.
\[\boxed{\text{CT}}\]
Step 2: In CT, each pixel is given a number proportional to how strongly that tissue attenuates the X-ray beam relative to water. Water is fixed at 0 HU as the reference point, air sits near -1000 HU, and compact bone is strongly positive. These numbers map directly onto the displayed greyscale.
Step 3: Ruling out the rest: MRI is reported as signal intensity, PET is read as standardised uptake values of an injected tracer, and ultrasound is based on echogenicity of reflected sound. None of these adopts the Hounsfield scale.
Step 4: Hence the Hounsfield unit belongs to CT scanning.
\[\boxed{\text{CT}}\]
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