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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§ion=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§ion=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§ion=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§ion=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§ion=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§ion=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§ion=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§ion=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