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Hounsfield scaleFrom Wikipedia, the free encyclopedia

The Hounsfield scale/h an zfild/or CT numbers, named after SirGodfrey Newbold Hounsfield,is a

uantitati!e scale for describin" radiodensity#

Contents

$hide%

& 'efinition

o & (ationale

) The H* of common substances

+ History

(eferences

- Notes

. 0ternal links

'efinition$edit%

The Hounsfield unit 1H*2 scale is a linear transformation of the ori"inal linear attenuation coefficient

measurement into one in which the radiodensityofdistilled waterat standard pressureandtemperature1ST32

is defined as zero Hounsfield units 1H*2, while the radiodensity ofairat ST3 is defined as 4&555 H*# 6n

a !o0elwith a!era"elinear attenuation coefficient , the correspondin" H* !alue is therefore "i!en by7

Where is the linear attenuation coefficients of water#

Thus, a chan"e of one Hounsfield unit 1H*2 represents a chan"e of 5#&8 of the attenuation coefficient ofwater since the attenuation coefficient of air is nearly zero#

6t is the definition for 9T scanners that are calibrated with reference to water#

Rationale$edit%

http://en.wikipedia.org/wiki/Help:IPA_for_Englishhttp://en.wikipedia.org/wiki/Help:IPA_for_Englishhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_Englishhttp://en.wikipedia.org/wiki/Godfrey_Newbold_Hounsfieldhttp://en.wikipedia.org/wiki/Godfrey_Newbold_Hounsfieldhttp://en.wikipedia.org/wiki/Godfrey_Newbold_Hounsfieldhttp://en.wikipedia.org/wiki/Radiodensityhttp://en.wikipedia.org/wiki/Hounsfield_scalehttp://en.wikipedia.org/wiki/Hounsfield_scalehttp://en.wikipedia.org/wiki/Hounsfield_scalehttp://en.wikipedia.org/wiki/Hounsfield_scale#Definitionhttp://en.wikipedia.org/wiki/Hounsfield_scale#Rationalehttp://en.wikipedia.org/wiki/Hounsfield_scale#The_HU_of_common_substanceshttp://en.wikipedia.org/wiki/Hounsfield_scale#Historyhttp://en.wikipedia.org/wiki/Hounsfield_scale#Referenceshttp://en.wikipedia.org/wiki/Hounsfield_scale#Noteshttp://en.wikipedia.org/wiki/Hounsfield_scale#External_linkshttp://en.wikipedia.org/w/index.php?title=Hounsfield_scale&action=edit&section=1http://en.wikipedia.org/wiki/Radiodensityhttp://en.wikipedia.org/wiki/Radiodensityhttp://en.wikipedia.org/wiki/Distilled_waterhttp://en.wikipedia.org/wiki/Distilled_waterhttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Standard_conditions_for_temperature_and_pressurehttp://en.wikipedia.org/wiki/Airhttp://en.wikipedia.org/wiki/Airhttp://en.wikipedia.org/wiki/Voxelhttp://en.wikipedia.org/wiki/Linear_attenuation_coefficienthttp://en.wikipedia.org/wiki/Linear_attenuation_coefficienthttp://en.wikipedia.org/wiki/Linear_attenuation_coefficienthttp://en.wikipedia.org/w/index.php?title=Hounsfield_scale&action=edit&section=2http://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_English#Keyhttp://en.wikipedia.org/wiki/Help:IPA_for_Englishhttp://en.wikipedia.org/wiki/Godfrey_Newbold_Hounsfieldhttp://en.wikipedia.org/wiki/Radiodensityhttp://en.wikipedia.org/wiki/Hounsfield_scalehttp://en.wikipedia.org/wiki/Hounsfield_scale#Definitionhttp://en.wikipedia.org/wiki/Hounsfield_scale#Rationalehttp://en.wikipedia.org/wiki/Hounsfield_scale#The_HU_of_common_substanceshttp://en.wikipedia.org/wiki/Hounsfield_scale#Historyhttp://en.wikipedia.org/wiki/Hounsfield_scale#Referenceshttp://en.wikipedia.org/wiki/Hounsfield_scale#Noteshttp://en.wikipedia.org/wiki/Hounsfield_scale#External_linkshttp://en.wikipedia.org/w/index.php?title=Hounsfield_scale&action=edit&section=1http://en.wikipedia.org/wiki/Radiodensityhttp://en.wikipedia.org/wiki/Distilled_waterhttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Standard_conditions_for_temperature_and_pressurehttp://en.wikipedia.org/wiki/Airhttp://en.wikipedia.org/wiki/Voxelhttp://en.wikipedia.org/wiki/Linear_attenuation_coefficienthttp://en.wikipedia.org/w/index.php?title=Hounsfield_scale&action=edit&section=2http://en.wikipedia.org/wiki/Help:IPA_for_English

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The abo!e standards were chosen as they are uni!ersally a!ailable references and suited to the key

application for which computed a0ial tomo"raphy was de!eloped7 ima"in" the internal anatomy of li!in"

creatures based on or"anized water structures and mostly li!in" in air, e.g.humans#

The H* of common substances$edit%

The Hounsfield scale applies to medical "rade 9T scans but not to cone beam computed tomo"raphy

19:9T2scans#$&%

Substance HU

Air 1000

Lung 500

Fat 100 to 50

Water 0

CSF 15

Kidney 30

Blood +30 to +45

Muscle +10 to +40

rey !atter +3" to +45

W#ite !atter +$0 to +30

Li%er +40 to +&0

http://en.wikipedia.org/wiki/Humanhttp://en.wikipedia.org/wiki/Humanhttp://en.wikipedia.org/wiki/Humanhttp://en.wikipedia.org/w/index.php?title=Hounsfield_scale&action=edit&section=3http://en.wikipedia.org/wiki/Cone_beam_computed_tomographyhttp://en.wikipedia.org/wiki/Cone_beam_computed_tomographyhttp://en.wikipedia.org/wiki/Cone_beam_computed_tomographyhttp://en.wikipedia.org/wiki/Hounsfield_scale#cite_note-DEVOS-1http://en.wikipedia.org/wiki/Hounsfield_scale#cite_note-DEVOS-1http://en.wikipedia.org/wiki/Cerebrospinal_fluidhttp://en.wikipedia.org/wiki/Humanhttp://en.wikipedia.org/w/index.php?title=Hounsfield_scale&action=edit&section=3http://en.wikipedia.org/wiki/Cone_beam_computed_tomographyhttp://en.wikipedia.org/wiki/Cone_beam_computed_tomographyhttp://en.wikipedia.org/wiki/Hounsfield_scale#cite_note-DEVOS-1http://en.wikipedia.org/wiki/Cerebrospinal_fluid

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'() Blast +$0 to +30

So*t issue, Contrast +100 to +300

Bone +"00 -cancellous .one/ to +3000 -dense .one/

; practical application of this is in e!aluation of tumors, where, for e0ample, anadrenal tumorwith a

radiodensity of less than &5 H* is rather fatty in composition and almost certainly a beni"nadrenal

adenoma#$)%

History$edit%

9T machines were the first ima"in" de!ices for detailed !isualization of the internal three4dimensionalanatomyof li!in" creatures, initially only astomo"raphicreconstructions of slice !iews or

sections# Since the early &ections of the true three4dimensional anatomy,

i#e#radiodensityshadows#6t was established by Sir Godfrey Newbold Hounsfield, one of the

principalen"ineersand de!elopers of computed a0ial tomo"raphy19;T, or 9T scans2#

http://en.wikipedia.org/wiki/Adrenal_tumorhttp://en.wikipedia.org/wiki/Adrenal_tumorhttp://en.wikipedia.org/wiki/Adrenal_adenomahttp://en.wikipedia.org/wiki/Adrenal_adenomahttp://en.wikipedia.org/wiki/Hounsfield_scale#cite_note-2http://en.wikipedia.org/wiki/Hounsfield_scale#cite_note-2http://en.wikipedia.org/w/index.php?title=Hounsfield_scale&action=edit&section=4http://en.wikipedia.org/wiki/Anatomyhttp://en.wikipedia.org/wiki/Anatomyhttp://en.wikipedia.org/wiki/Tomographyhttp://en.wikipedia.org/wiki/Tomographyhttp://en.wikipedia.org/wiki/Computed_axial_tomographyhttp://en.wikipedia.org/wiki/Computed_axial_tomographyhttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/Radiodensityhttp://en.wikipedia.org/wiki/Shadowhttp://en.wikipedia.org/wiki/Shadowhttp://en.wikipedia.org/wiki/Godfrey_Newbold_Hounsfieldhttp://en.wikipedia.org/wiki/Engineerhttp://en.wikipedia.org/wiki/Engineerhttp://en.wikipedia.org/wiki/Computed_axial_tomographyhttp://en.wikipedia.org/wiki/Adrenal_tumorhttp://en.wikipedia.org/wiki/Adrenal_adenomahttp://en.wikipedia.org/wiki/Adrenal_adenomahttp://en.wikipedia.org/wiki/Hounsfield_scale#cite_note-2http://en.wikipedia.org/w/index.php?title=Hounsfield_scale&action=edit&section=4http://en.wikipedia.org/wiki/Anatomyhttp://en.wikipedia.org/wiki/Tomographyhttp://en.wikipedia.org/wiki/Computed_axial_tomographyhttp://en.wikipedia.org/wiki/Computed_axial_tomographyhttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/Radiodensityhttp://en.wikipedia.org/wiki/Shadowhttp://en.wikipedia.org/wiki/Godfrey_Newbold_Hounsfieldhttp://en.wikipedia.org/wiki/Engineerhttp://en.wikipedia.org/wiki/Computed_axial_tomography