亨氏單位

亨氏單位（英語：Hounsfield unit，縮寫：HU），為亨氏量表（Hounsfield scale）阻射率（英语：Radiodensity）的數量尺度單位，命名自X射線電腦斷層掃描的發明人高弗雷·豪斯費爾德（Godfrey Newbold Hounsfield）。亨氏單位常用於X射線電腦斷層掃描，因此又稱為CT值（CT number）。

定義

亨氏單位為其所測量之介質的線性衰減係數的線性映射，其定義將蒸餾水與空氣在標準溫度與標準壓力下的阻射率（英语：Radiodensity）分別設為0 HU和-1,000 HU。因此，在線性衰減係數介於平均值間的體素中，其亨氏單位為：^[1]

${\displaystyle HU=1000\times {\frac {\mu -\mu _{\textrm {water}}}{\mu _{\textrm {water}}-\mu _{\textrm {air}}}}}$ 

其中${\displaystyle \mu _{\textrm {water}}}$ 與${\displaystyle \mu _{\textrm {air}}}$ 分別為水與空氣的線性衰減係數。^[2]

由於空氣的線性衰減係數趨近於0，一個HU的變化相當於水線性衰減係數0.1%的變化。^[2]

原理

由於X射線電腦斷層掃描的功能在於將生物（主要是陸上生物，如人類）的體內結構成像化，因此採納上述標準作為所有介質的參照依據。^[2]

人體內各介質的亨氏單位值

亨氏單位僅適用於常見的雙能電腦斷層掃描（dual-energy CT scan），而不適用於錐狀射束電腦斷層掃描（cone beam CT scan）。^[3]

介質		亨氏單位
空氣		−1,000
脂肪		−120至−90^[4]
造影劑電腦斷層掃描（英语：Contrast CT）下的軟組織		+100至+300
骨骼	鬆質骨	+300至+400^[5]
	密質骨	+1,800至+1,900^[5]
頭部外傷	前數小時	+75至+100^[6]
	3日後	+65至+85^[6]
	10-14日後	+35至+40^[7]
其他血液	非凝血	+13^[8]至+50^[9]
	凝血	+50^[10]至+75^[8]^[10]
胸腔積液	漏出液（英语：Transudate）	+2至+15 ^[11]
	滲出液（英语：Exudate）	+4至+33^[11]
其他體液	乳糜	−30^[12]
	水	0
	尿液	−5至+15^[4]
	膽汁	−5至+15^[4]
	腦脊液	+15
	膿瘍/膿	0^[13]至+20^[14] 或 +40^[14]至+45^[13]
	黏液	0^[15] - 130^[16]（超過70HU時進入高衰減）^[17]^[18]
薄壁組織	肺	−700至−600^[19]
	腎	+20至+45^[4]
	肝	60 ± 6^[20]
	淋巴結	+10至+20^[21]
	肌肉	+35至+55^[4]
	胸腺	+20至+40（兒童）^[22]
		+20至+120（成人）^[22]
	白質	+20至+30
	灰質	+37至+45
膽結石	膽固醇石	+30至+100^[23]
	色素性膽結石	+90至+120^[23]
異物（英语：Foreign body）^[24]	一般窗戶玻璃	+500
	鋁、瀝青、車窗玻璃、玻璃瓶與其他石類	+2,100至+2,300
	石灰岩	+2,800
	銅	+14,000
	銀	+17,000
	鋼	+20,000
	金、鋼與黃銅	+30,000（可測量之上限）
耳垢		<0

亨氏單位常用於辨識腫瘤，以腎上腺腺瘤（英语：Adrenal adenoma）為例，當該腫瘤的阻射率（英语：Radiodensity）小於10 HU，則其脂肪成分偏高，代表該腫瘤有較大機率為良性腫瘤^[25]。

參見

參考資料

1. Lev, Michael; Gonzalez, Rodolfo. CT Angiography and CT Perfusion Imaging. ScienceDirect. 2002 [2020-12-20]. （原始内容于2020-11-12） （英语）. 
2. DenOtter, Tami; Schubert, Johanna. Hounsfield Unit. 美國國家衛生院. 2020-05-11 [2020-12-20]. （原始内容于2021-12-06） （英语）. 
3. De Vos, W.; Casselman, J.; Swennen, G.R.J. Cone-beam computerized tomography (CBCT) imaging of the oral and maxillofacial region: A systematic review of the literature. International Journal of Oral and Maxillofacial Surgery. 2009-06, 38 (6): 609–625. PMID 19464146. doi:10.1016/j.ijom.2009.02.028. 
4. Page 83 in: Herbert Lepor. Prostatic Diseases. W.B. Saunders Company. 2000. ISBN 9780721674162. 
5. Birur, NPraveen; Patrick, Sanjana; Gurushanth, Keerthi; Raghavan, AShubhasini; Gurudath, Shubha. Comparison of gray values of cone-beam computed tomography with hounsfield units of multislice computed tomography: An in vitro study. Indian Journal of Dental Research. 2017年, 28 (1): 66–70. ISSN 0970-9290. PMID 28393820. doi:10.4103/ijdr.IJDR_415_16. 
6. Fig 3 in: Rao, Murali Gundu. Dating of Early Subdural Haematoma: A Correlative Clinico-Radiological Study. Journal of Clinical and Diagnostic Research. 2016, 10 (4): HC01–5. ISSN 2249-782X. PMC 4866129  . PMID 27190831. doi:10.7860/JCDR/2016/17207.7644. 
7. Dr Rohit Sharma; A.Prof Frank Gaillard. Subdural haemorrhage. Radiopaedia. [2018-08-14]. （原始内容于2011-03-23）. 
8. Page 263 in: Robert Fosbinder; Denise Orth. Essentials of Radiologic Science. Lippincott Williams & Wilkins. 2011. ISBN 9780781775540. 
9. page 20.17 in: F W Wright. Radiology of the Chest and Related Conditions. CRC Press. 2001. ISBN 9780415281416. 
10. page 17 in: Dr. Avital Fast; Dorith Goldsher. Navigating the Adult Spine: Bridging Clinical Practice and Neuroradiology. Demos Medical Publishing. 2006. ISBN 9781934559741. 
11. Cullu, Nesat; Kalemci, Serdar; Karakas, Omer; Eser, Irfan; Yalcin, Funda; Boyaci, Fatma Nurefsan; Karakas, Ekrem. Efficacy of CT in diagnosis of transudates and exudates in patients with pleural effusion. Diagnostic and Interventional Radiology. 2013, 20 (2): 116–20. ISSN 1305-3825. PMC 4463296  . PMID 24100060. doi:10.5152/dir.2013.13066. 
12. Page 342 in: Luca Saba; Jasjit S. Suri. Multi-Detector CT Imaging: Principles, Head, Neck, and Vascular Systems, Volume 1. CRC Press. 2013. ISBN 9781439893845. 
13. P. Sanchez de Medina Alba; C. Santos Montón; N. Calvo; K. El Karzazi; T. González de la Huebra Labrador; R. Corrales; N. Alegre Borge; Salamanca/ES. Liver abscesses: where do they come from?A review of the main types of liver abscesses and the correlation between their causes and the radiologic findings. ECR 2014. 2014 [2020-12-17]. doi:10.1594/ecr2014/C-1927. （原始内容于2019-01-12）. 
14. Sasaki, Toru; Miyata, Rie; Hatai, Yoshiho; Makita, Kohzoh; Tsunoda, Koichi. Hounsfield unit values of retropharyngeal abscess-like lesions seen in Kawasaki disease. Acta Oto-Laryngologica. 2014, 134 (4): 437–440. ISSN 0001-6489. PMID 24512428. doi:10.3109/00016489.2013.878475. 
15. K SAGGAR, A AHLUWALIA; P SANDHU, V KALIA. Mucocoele Of The Appendix (PDF). Ind J Radiol Imag. 2006, 16 (2). ^{[失效連結]}
16. Gaeta, Michele; Vinci, Sergio; Minutoli, Fabio; Mazziotti, Silvio; Ascenti, Giorgio; Salamone, Ignazio; Lamberto, Salvatore; Blandino, Alfredo. CT and MRI findings of mucin-containing tumors and pseudotumors of the thorax: pictorial review. European Radiology. 2001, 12 (1): 181–189. ISSN 0938-7994. PMID 11868096. doi:10.1007/s003300100934. 
17. Subash S Phuyal; Mandeep Kumar MK Garg; Ritesh R Agarwal; Pankaj P Gupta; Arunaloke A Chakrabarti; Manavjit Singh MS Sandhu; Niranjan N Khandelwal. High-Attenuation Mucus Impaction in Patients With Allergic Bronchopulmonary Aspergillosis: Objective Criteria on High-Resolution Computed Tomography and Correlation With Serologic Parameters. Current Problems in Diagnostic Radiology. 2015-09-02. 
18. Agarwal, Ritesh; Sehgal, Inderpaul Singh; Dhooria, Sahajal; Aggarwal, Ashutosh. Radiologic Criteria for the Diagnosis of High-Attenuation Mucus in Allergic Bronchopulmonary Aspergillosis. Chest. 2016, 149 (4): 1109–1110. ISSN 0012-3692. PMID 27055707. doi:10.1016/j.chest.2015.12.043. 
19. Page 379 in: Ella A. Kazerooni; Barry H. Gross. Cardiopulmonary Imaging 4. Lippincott Williams & Wilkins. 2004. ISBN 9780781736558. 
20. page 210 in: Erwin Kuntz; Hans-Dieter Kuntz. Hepatology, Principles and Practice: History, Morphology, Biochemistry, Diagnostics, Clinic, Therapy. Springer Science & Business Media. 2006. ISBN 9783540289777. 
21. Page 58 in: G. Maatman. High-Resolution Computed Tomography of the Paranasal Sinuses and Pharynx and Related Regions: Impact of CT identification on diagnosis and patient management. Volume 12 of Series in Radiology. Springer Science & Business Media. 2012. ISBN 9789400942776. 
22. Page 488 （页面存档备份，存于互联网档案馆） in: Jean-Claude Givel; Marco Merlini; David B. Clarke; Michael Dusmet. Surgery of the Thymus: Pathology, Associated Disorders and Surgical Technique. Springer Science & Business Media. 2012. ISBN 9783642710766. 
23. Rambow A, Staritz M, Wosiewitz U, Mildenburger P, Thelen M, Meyer zum Büschenfelde KH. Analysis of radiolucent gallstones by computed tomography for in vivo estimation of stone components. Eur J Clin Invest. 1990, 20 (4): 475–8. PMID 2121509. doi:10.1111/j.1365-2362.1990.tb01887.x. 
24. Bolliger, Stephan A.; Oesterhelweg, Lars; Spendlove, Danny; Ross, Steffen; Thali, Michael J. Is Differentiation of Frequently Encountered Foreign Bodies in Corpses Possible by Hounsfield Density Measurement?. Journal of Forensic Sciences. 2009, 54 (5): 1119–1122. ISSN 0022-1198. PMID 19627414. doi:10.1111/j.1556-4029.2009.01100.x. 
25. Perry J Horwich. Adrenal Adenoma Imaging. 2011-04-21 [2020-12-19] （英语）. 

參考書籍

• Feeman, Timothy G. The Mathematics of Medical Imaging: A Beginner's Guide. Springer Undergraduate Texts in Mathematics and Technology. Springer. 2010. ISBN 978-0387927114. 

外部連結

• Hounsfield unit. Medcyclopaedia. GE. [2020-12-17]. （原始内容存档于2012-04-04）. 
• Hounsfield Unit （页面存档备份，存于互联网档案馆） - fpnotebook.com
• Introduction to CT physics (PDF). elsevierhealth.com. [2020-12-17]. （原始内容 (PDF)于2007-09-26）. 
• Imaging of deep brain stimulation leads using extended Hounsfield unit CT. Stereotact Funct Neurosurg. 2009;87(3):155-60. doi: 10.1159/000209296 （页面存档备份，存于互联网档案馆）