The Hounsfield unit (HU) scale is a linear transformation of the original linear attenuation coefficient measurement in one in which the radiodensity of distilled water at standard pressure and temperature (STP) is defined as zero Hounsfield units (HU), while the radiodensity of air at STP is defined as -1000 HU.

For a material X with linear attenuation coefficient μX, the corresponding HU value is therefore given by where is the linear attenuation coefficient of water.

Thus, a change of one Hounsfield unit (HU) represents a change of 0.1% of the attenuation coefficient of water since the attenuation coefficient of air is nearly zero.

It is the definition for CT scanners that are calibrated with reference to water.

+1000 = Bone

+80 = Liver

+55 = Muscle

0 = water (cyst)

-1000 = Air

For a material X with linear attenuation coefficient μX, the corresponding HU value is therefore given by where is the linear attenuation coefficient of water.

Thus, a change of one Hounsfield unit (HU) represents a change of 0.1% of the attenuation coefficient of water since the attenuation coefficient of air is nearly zero.

It is the definition for CT scanners that are calibrated with reference to water.

+1000 = Bone

+80 = Liver

+55 = Muscle

0 = water (cyst)

-1000 = Air

value below is slightly different. taken from this website

Bone | 1000 |

Liver | 40 - 60 |

White matter | ~20-30 HU |

Grey matter | ~37-45 HU |

Blood | 40 |

Muscle | 10 - 40 |

Kidney | 30 |

Cerebrospinal fluid | 15 |

Water | 0 |

Fat | -50 - -100 |

Air | -1000 |

HU ni sangat berguna jugak untuk kesan ade abnormality tak kat organ, for eg: brain CT.

ReplyDeletejust gerak2 kan cursor kat seluruh brain dalam CT images, die akan automatically bg reading for HU at any places where we put the cursor.

best kan HU ni walaupun sangat physics :)

cik As:

ReplyDeleteya betul tu saudari... i'm sure u're more expert than me since u're involving with radiology a lot

feel free to give more enlightenment on radiology issue.