cone beam computed tomography

File:Cone Beam CT principle.png

In the late 1990s, Dr Yoshinori Arai in Japan and Dr Piero Mozzo in Italy independently developed Cone Beam Computed Technology for oral and maxillofacial radiology.{{Cite journal|last1=Venkatesh|first1=Elluru|last2=Elluru|first2=Snehal Venkatesh|date=2017-12-02|title=Cone beam computed tomography: basics and applications in dentistry|journal=Journal of Istanbul University Faculty of Dentistry|volume=51|issue=3 Suppl 1|pages=S102–S121|doi=10.17096/jiufd.00289|issn=2149-2352|pmc=5750833|pmid=29354314}} The first commercial system (the NewTom 9000) was introduced in the European market in 1996 and into the US market in 2001, by Italian company Quantitative Radiology.{{cite book |last1=Molteni |first1=R |editor1-last=Budinger |editor1-first=Thomas |editor2-last=Brahme |editor2-first=Anders |title=Comprehensive Biomedical Physics |date=2014 |publisher=Elsevier |location=Amsterdam |isbn=9780444536327 |page=112 |chapter-url=https://books.google.com/books?id=9RR0AwAAQBAJ&pg=RA1-PA112 |language=en |chapter=Oral and Maxillofacial Radiology}}

File:Prima Immagine Cone-Beam-1994-07-01 -1.jpg | Axial image obtained from the first Cone-Beam 3D Scan performed on July 1, 1994{{cite web|url=http://www.newtom.it/it/news-ed-eventi/eventi/2014/20deg-anniversary-of-the-1deg-dental-cbct-complete-scan|title=20st Anniversary of the 1st dental CBCT complete scan — NewTom|website=www.newtom.it|access-date=2014-07-11|archive-date=2014-07-14|archive-url=https://web.archive.org/web/20140714202051/http://www.newtom.it/it/news-ed-eventi/eventi/2014/20deg-anniversary-of-the-1deg-dental-cbct-complete-scan|url-status=dead}}

File:Prima Immagine Cone-Beam-1994-07-02.jpg | Axial image obtained from the first Cone-Beam 3D Scan performed on July 1, 1994

File:Prima Immagine Cone-Beam-1994-07-01-3.jpg | Axial image obtained from the first Cone-Beam 3D Scan performed on July 1, 1994

File:Prima acquisizione totale 1994-07-01-pag1.jpeg | Original notes about the first Cone-Beam 3D Scan performed on July 1, 1994

Cone beam CT using kilovoltage X-rays (as used for diagnostic, rather than therapeutic purposes) attached to a linear accelerator treatment machine was first developed in the late 1990s and early 2000s.{{cite journal |last1=Thwaites |first1=David I |last2=Tuohy |first2=John B |title=Back to the future: the history and development of the clinical linear accelerator |journal=Physics in Medicine and Biology |date=2006-07-07 |volume=51 |issue=13 |pages=R343–R362 |doi=10.1088/0031-9155/51/13/R20 |pmid=16790912 |s2cid=7672187 |url=https://www.sprmn.pt/pdf/pmb6_13_r20_LINACs_(Thwaites&Tuohy).pdf}} Such systems have since become common on latest generation linacs.{{cite journal |last1=Shepherd |first1=Justin |title=Applications of linac-mounted kilovoltage Cone-beam Computed Tomography in modern radiation therapy: A review |journal=Polish Journal of Radiology |date=2014 |volume=79 |pages=181–193 |doi=10.12659/PJR.890745 |pmid=25006356 |pmc=4085117}} In the late 2010s CBCT also started to become available on-board particle therapy delivery systems.{{cite journal |last1=Herrmann |first1=H. |last2=Seppenwoolde |first2=Y. |last3=Georg |first3=D. |last4=Widder |first4=J. |title=Image guidance: past and future of radiotherapy |journal=Der Radiologe |date=December 2019 |volume=59 |issue=S1 |pages=21–27 |doi=10.1007/s00117-019-0573-y |pmid=31346650 |pmc=6914710}}

While CBCT with X-ray image intensifiers was experimented with in the late 1990s, it was not until the adoption of flat-panel X-ray detectors, with improved contrast and spatial resolution, that CBCT became practical for clinical use in interventional radiology procedures.{{cite journal |last1=Orth |first1=Robert C. |last2=Wallace |first2=Michael J. |last3=Kuo |first3=Michael D. |title=C-arm Cone-beam CT: General Principles and Technical Considerations for Use in Interventional Radiology |journal=Journal of Vascular and Interventional Radiology |date=June 2008 |volume=19 |issue=6 |pages=814–820 |doi=10.1016/j.jvir.2008.02.002 |pmid=18503894}}{{cite journal |last1=Wallace |first1=Michael J. |last2=Kuo |first2=Michael D. |last3=Glaiberman |first3=Craig |last4=Binkert |first4=Christoph A. |last5=Orth |first5=Robert C. |last6=Soulez |first6=Gilles |title=Three-Dimensional C-arm Cone-beam CT: Applications in the Interventional Suite |journal=Journal of Vascular and Interventional Radiology |date=June 2008 |volume=19 |issue=6 |pages=799–813 |doi=10.1016/j.jvir.2008.02.018 |pmid=18503893}} Many fixed, and even mobile, C-arm fluoroscopy systems are now capable of CBCT acquisitions, in addition to traditional planar fluoroscopy.{{cite book |last1=Siewerdsen |first1=Jeffrey |editor1-last=Samei |editor1-first=Ehsan |editor2-last=Pelc |editor2-first=Norbert |title=Computed Tomography: Approaches, Applications, and Operations |date=2019 |publisher=Springer Nature Switzerland |location=Cham |isbn=9783030269562 |page=20 |chapter-url=https://books.google.com/books?id=saO-DwAAQBAJ&pg=PA20 |language=en |chapter=Cone-Beam CT Systems}}{{cite journal |last1=Floridi |first1=Chiara |last2=Radaelli |first2=Alessandro |last3=Abi-Jaoudeh |first3=Nadine |last4=Grass |first4=Micheal |last5=De Lin |first5=Ming |last6=Chiaradia |first6=Melanie |last7=Geschwind |first7=Jean-Francois |last8=Kobeiter |first8=Hishman |last9=Squillaci |first9=Ettore |last10=Maleux |first10=Geert |last11=Giovagnoni |first11=Andrea |last12=Brunese |first12=Luca |last13=Wood |first13=Bradford |last14=Carrafiello |first14=Gianpaolo |last15=Rotondo |first15=Antonio |title=C-arm cone-beam computed tomography in interventional oncology: technical aspects and clinical applications |journal=La Radiologia Medica |date=July 2014 |volume=119 |issue=7 |pages=521–532 |doi=10.1007/s11547-014-0429-5 |pmid=25012472 |pmc=4209965}} CBCT aids image guidance during interventional radiology procedures treating various medical conditions including knee osteoarthritis, benign prostatic hyperplasia, and hepatocellular carcinoma.{{Cite journal |last1=Cusumano |first1=Lucas R. |last2=Callese |first2=Tyler E. |last3=Redwood |first3=Karen |last4=Genshaft |first4=Scott |last5=Plotnik |first5=Adam N. |last6=Stewart |first6=Jessica K. |last7=Padia |first7=Siddharth A. |date=2023-08-11 |title=Added Value of Cone-Beam CT to Identify Arterial Supply during Genicular Artery Embolization for Knee Osteoarthritis |url=https://www.sciencedirect.com/science/article/pii/S1051044323005717 |journal=Journal of Vascular and Interventional Radiology |volume=34 |issue=11 |pages=1861–1867 |doi=10.1016/j.jvir.2023.07.033 |pmid=37573000 |s2cid=260856660 |issn=1051-0443}}{{Cite journal |last=Angle |first=John F. |date=September 2013 |title=Cone-beam CT: vascular applications |url=https://pubmed.ncbi.nlm.nih.gov/23993076/ |journal=Techniques in Vascular and Interventional Radiology |volume=16 |issue=3 |pages=144–149 |doi=10.1053/j.tvir.2013.02.009 |issn=1557-9808 |pmid=23993076}}{{Cite journal |last1=Cadour |first1=F. |last2=Tradi |first2=F. |last3=Habert |first3=P. |last4=Scemama |first4=U. |last5=Vidal |first5=V. |last6=Jacquier |first6=A. |last7=Bartoli |first7=J.-M. |last8=Moulin |first8=G. |last9=Bessayah |first9=A. |date=November 2020 |title=Prostatic artery embolization using three-dimensional cone-beam computed tomography |journal=Diagnostic and Interventional Imaging |volume=101 |issue=11 |pages=721–725 |doi=10.1016/j.diii.2020.05.002 |issn=2211-5684 |pmid=32532575|doi-access=free }}{{Cite journal |last1=Pung |first1=Leland |last2=Ahmad |first2=Moiz |last3=Mueller |first3=Kerstin |last4=Rosenberg |first4=Jarrett |last5=Stave |first5=Christopher |last6=Hwang |first6=Gloria L. |last7=Shah |first7=Rajesh |last8=Kothary |first8=Nishita |date=March 2017 |title=The Role of Cone-Beam CT in Transcatheter Arterial Chemoembolization for Hepatocellular Carcinoma: A Systematic Review and Meta-analysis |url=https://pubmed.ncbi.nlm.nih.gov/28109724/ |journal=Journal of Vascular and Interventional Radiology |volume=28 |issue=3 |pages=334–341 |doi=10.1016/j.jvir.2016.11.037 |issn=1535-7732 |pmid=28109724}}

File:3D CT impacted wisdom tooth.Gif

The most significant advantage of the CBCT in Endodontics is that it can show critical root canal anatomical features that conventional intraoral or panoramic images cannot.{{Cite journal|last1=Scarfe|first1=William C.|last2=Levin|first2=Martin D.|last3=Gane|first3=David|last4=Farman|first4=Allan G.|date=2009|title=Use of Cone Beam Computed Tomography in Endodontics|journal=International Journal of Dentistry|volume=2009|page=634567|doi=10.1155/2009/634567|issn=1687-8728|pmc=2850139|pmid=20379362|doi-access=free}}

According to the American Association of Endodontics, there are numerous specific situations in which 3D images produced by CBCT enhance diagnosis and influence treatment, and its use cannot be disputed over conventional intraoral radiology based on ALARA principles.{{Cite web|url=https://www.aae.org/specialty/wp-content/uploads/sites/2/2017/07/ecfe-summer-11-final.pdf|title=Cone Beam-Computed Tomography in Endodontics|date=Summer 2011|website=www.aae.org|access-date=October 21, 2019}}

A dental cone beam scan offers useful information when it comes to the assessment and planning of surgical implants. The American Academy of Oral and Maxillofacial Radiology (AAOMR) suggests cone-beam CT as the preferred method for presurgical assessment of dental implant sites.New AAOMR [http://blog.gendex.com/bloggendexcom/bid/168633/New-AAOMR-Guidelines-for-3D-Imaging-Use-in-Implant-Planning Guidelines on CBCT Use in Implant Planning] {{Webarchive|url=https://web.archive.org/web/20170205221049/http://blog.gendex.com/bloggendexcom/bid/168633/New-AAOMR-Guidelines-for-3D-Imaging-Use-in-Implant-Planning |date=2017-02-05 }}

As a 3D rendition, CBCT offers an undistorted view of the dentition that can be used to accurately visualize both erupted and non-erupted teeth, tooth root orientation and anomalous structures, that conventional 2D radiography cannot.{{cite journal |vauthors=Mah JK, Huang JC, Choo H |title=Practical applications of cone-beam computed tomography in orthodontics |journal=Journal of the American Dental Association |volume=141 |issue=Suppl 3 |pages=7S–13S |date=October 2010 |pmid=20884934 |url=http://jada.ada.org/cgi/pmidlookup?view=long&pmid=20884934 |url-status=dead |archive-url=https://archive.today/20140718023206/http://jada.ada.org/cgi/pmidlookup?view=long&pmid=20884934 |archive-date=2014-07-18 |doi=10.14219/jada.archive.2010.0361 }}

Processing example using x-ray data from a tooth model:

File:DVT-scan-MagoCut-bild1-singlesample.jpg|single sampled (noisy) image

File:DVT-scan-MagoCut-bild2-oversamplefocus.jpg|several samples overlay

File:DVT-scan-MagoCut-bild3-panoramiomodejoined.jpg|joined images to panoramic

File:DVT-scan-MagoCut-bild4-dvtreconstructed.jpg|algorithmic reconstruction

File:CBCT image 03.png|in-vivo image

The CBCT scanner offers undistorted views of the extremities. One advantage of orthopedic CBCT is the ability to take weight bearing images of the lower extremities. In the realm of the foot and ankle particularly, weight bearing CBCT is gaining momentum due to its ability to combine 3 dimensional and weight bearing information which are of the utmost importance in diagnosis and surgical planning.{{cite journal|last1=Barg|first1=Alexej|last2=Bailey|first2=Travis|last3=Richter|first3=Martinus|last4=Netto|first4=Cesar|last5=Lintz|first5=François|last6=Burssens|first6=Arne|last7=Phisitkul|first7=Phinit|last8=Hanrahan|first8=Christopher J.|last9=Saltzman|first9=Charles L.|title=Weightbearing Computed Tomography of the Foot and Ankle: Emerging Technology Topical Review|journal=Foot & Ankle International|volume=39|issue=3|pages=376–386|date=24 November 2017|doi=10.1177/1071100717740330|pmid=29171283|s2cid=3743675}} The preferred term used for CBCT in the lower limb is thus WBCT for Weight Bearing CT following the first scientific publications on the subject.{{Cite journal|last1=Tuominen|first1=Esa K. J.|last2=Kankare|first2=Jussi|last3=Koskinen|first3=Seppo K.|last4=Mattila|first4=Kimmo T.|date=2013-01-01|title=Weight-Bearing CT Imaging of the Lower Extremity|journal=American Journal of Roentgenology|volume=200|issue=1|pages=146–148|doi=10.2214/AJR.12.8481|pmid=23255755|issn=0361-803X}}{{Cite journal|last1=Colin|first1=Fabrice|last2=Horn Lang|first2=Tamara|last3=Zwicky|first3=Lukas|last4=Hintermann|first4=Beat|last5=Knupp|first5=Markus|date=2014-07-11|title=Subtalar Joint Configuration on Weightbearing CT Scan|journal=Foot & Ankle International|language=en-US|volume=35|issue=10|pages=1057–1062|doi=10.1177/1071100714540890|pmid=25015393|s2cid=24240090|issn=1071-1007}}{{Cite journal|last1=Richter|first1=Martinus|last2=Seidl|first2=Bernd|last3=Zech|first3=Stefan|last4=Hahn|first4=Sarah|date=September 2014|title=PedCAT for 3D-imaging in standing position allows for more accurate bone position (angle) measurement than radiographs or CT|journal=Foot and Ankle Surgery|volume=20|issue=3|pages=201–207|doi=10.1016/j.fas.2014.04.004|pmid=25103709|issn=1268-7731}}{{Cite journal|last1=Lintz|first1=François|last2=Welck|first2=Matthew|last3=Bernasconi|first3=Alessio|last4=Thornton|first4=James|last5=Cullen|first5=Nicholas P.|last6=Singh|first6=Dishan|last7=Goldberg|first7=Andy|date=2017-02-09|title=3D Biometrics for Hindfoot Alignment Using Weightbearing CT|journal=Foot & Ankle International|language=en-US|volume=38|issue=6|pages=684–689|doi=10.1177/1071100717690806|pmid=28183212|s2cid=7828393|issn=1071-1007|url=https://discovery.ucl.ac.uk/id/eprint/1544650/}}

Image-guided radiation therapy is a form of external beam radiotherapy where the patient is positioned with the organs to be treated accurately matched in position to the treatment field, to reduce the dose to nearby organs which are not being treated. Many organs inside the body move by millimeters relative to the external skin surfaces, and a CBCT scanner mounted on the head of the radiotherapy unit is used immediately before treatment (and sometimes again during treatment) to ensure the patient's organs are in exactly the right position to match the treatment field, and to adjust the position of the treatment table if necessary. The images may also be used to check for other requirements of some types of treatment, such as full or empty bladder, empty rectum, etc.{{cite journal |last1=Sterzing |first1=Florian |last2=Engenhart-Cabillic |first2=Rita |last3=Flentje |first3=Michael |last4=Debus |first4=Jürgen |title=Image-Guided Radiotherapy |journal=Deutsches Ärzteblatt Online |date=22 April 2011 |volume=108 |issue=16 |pages=274–280 |doi=10.3238/arztebl.2011.0274 |pmid=21603562 |pmc=3097488}} The same cone beam beam source and detector can alternatively be used to take simple X-ray positioning images if the organ shows particularly well on X-ray or if Fiducial markers have been inserted into the organ.{{cite journal |last1=O'Neill |first1=Angela G M |last2=Jain |first2=Suneil |last3=Hounsell |first3=Alan R |last4=O'Sullivan |first4=Joe M |title=Fiducial marker guided prostate radiotherapy: a review |journal=The British Journal of Radiology |date=December 2016 |volume=89 |issue=1068 |pages=20160296 |doi=10.1259/bjr.20160296 |pmid=27585736 |pmc=5604907}}

The CBCT scanner is mounted on a C-arm fluoroscopy unit in the interventional radiology (IR) suite, which offers real time imaging with a stationary patient. This eliminates the time needed to transfer a patient from the angiography suite to a conventional computed tomography scanner and facilitates a broad spectrum of applications of CBCT during IR procedures. The clinical applications of CBCT in IR include treatment planning, device or implant positioning and assessment, intra-procedural localization, and assessment of procedure endpoints. CBCT is useful as a primary and supplemental form of imaging. It is an excellent adjunct to DSA and fluoroscopy for soft tissue and vascular visibility during complex procedures. The use of CBCT before fluoroscopy potentially reduces patient radiation exposure.

• Chemoembolization for Hepatocellular Carcinoma: CBCT with contrast confirms that the proper artery is selected to deliver the therapy. The contrast enhances the parenchyma supplied by the selected artery and therefore reveals if the vasculature also supplies the tumor. Post-treatment non-contrast CBCT confirms lipiodol staining of the tumor, which improves operator confidence of complete tumor coverage or further treatment.{{cite journal |vauthors=Wallace MJ, Kuo MD, Glaiberman C, Binkert CA, Orth RC, Soulez G |title=Three-dimensional C-arm cone-beam CT: applications in the interventional suite |journal=Journal of Vascular and Interventional Radiology |volume=19 |issue=6 |pages=799–813 |date=June 2008 |pmid=18503893 |doi=10.1016/j.jvir.2008.02.018}}
• Prostatic artery embolization for benign prostatic hyperplasia: CBCT provides the soft tissue detail needed to visualize prostatic enhancement, identify duplicated prostatic arteries, and avoid nontarget embolization. CBCT is superior to DSA for this therapy since the enhancement patterns on DSA can be difficult to discern due to the overlapping pelvic structures and variable arterial anatomy.{{cite journal |vauthors=Bagla S, Rholl KS, Sterling KM |title=Utility of cone-beam CT imaging in prostatic artery embolization |journal=Journal of Vascular and Interventional Radiology |volume=24 |issue=11 |pages=1603–7 |date=November 2013 |pmid=23978461 |doi=10.1016/j.jvir.2013.06.024|display-authors=etal}}
• Abscess drainage: CBCT confirms needle tip location after placement under ultrasound and confirms drain placement by revealing contrast injection into the desired location.
• Adrenal Vein sampling for an adenoma: contrast-enhanced CBCT shows perfusion of the adrenal gland to confirm catheter placement for obtaining a satisfactory sample.{{cite journal |vauthors=Georgiades CS, Hong K, Geschwind JF |title=Adjunctive use of C-arm CT may eliminate technical failure in adrenal vein sampling |journal=Journal of Vascular and Interventional Radiology |volume=18 |issue=9 |pages=1102–5 |date=September 2007 |pmid=17804771 |doi=10.1016/j.jvir.2007.06.018|display-authors=etal}}
• Stent placement: CBCT improves the visualization of intracranial and extracranial stents compared to conventional DSA and digital radiography by providing a better depiction of the relationship of the stents to nearby structures (i.e. vascular walls and aneurysm lumen).{{cite journal |vauthors=Benndorf G, Claus B, Strother CM, Chang L, Klucznik RP |title=Increased cell opening and prolapse of struts of a neuroform stent in curved vasculature: value of angiographic computed tomography: technical case report |journal=Neurosurgery |volume=58 |issue=4 Suppl 2 |pages=ONS–E380; discussion ONS–E380 |date=April 2006 |pmid=16575290 |doi=10.1227/01.NEU.0000205287.06739.E1|s2cid=13168780 }}
• Lung nodule percutaneous transthoracic needle biopsy: CBCT guides needle placement and demonstrated a diagnostic accuracy, sensitivity, and specificity of 98.2%, 96.8%, and 100%, respectively. Diagnostic accuracy was unaffected by technically challenging conditions.{{cite journal |vauthors=Choi JW, Park CM, Goo JM |title=C-arm cone-beam CT-guided percutaneous transthoracic needle biopsy of small (≤ 20 mm) lung nodules: diagnostic accuracy and complications in 161 patients |journal=American Journal of Roentgenology |volume=199 |issue=3 |pages=W322–30 |date=September 2012 |pmid=22915422 |doi=10.2214/AJR.11.7576|display-authors=etal}}
• Vascular Anomalies: After correction of arteriovenous malformations with coiling, CBCT sensitively detects small infarcts in tissue that has been "sacrificed" during the procedure to prevent further shunting. The infarcted tissue appears as a small area of contrast retention.
• Peripheral Vascular Interventions{{citation needed|date=July 2024}}
• Biliary Interventions{{citation needed|date=July 2024}}
• Spinal Interventions{{citation needed|date=July 2024}}
• Enterostomy Interventions{{citation needed|date=July 2024}}

Cone beam CT is used for material analysis, metrology, and nondestructive testing in the manufacturing sector. Cone beam CT is also inspect and detect defects of tiny sizes, such as internal pitting corrosion or cracks of an object in quality control.{{Cite journal |last1=B. N. |first1=Ha |last2=T. K. |first2=Tuan |last3=T. N. |first3=Toan |last4=T. T. |first4=Duong |last5=T. M. |first5=Anh |last6=B. T. |first6=Hung |last7=M. D. |first7=Thuy |date=2021-12-30 |title=Research and manufacture of cone-beam computed tomography (CBCT) system for industrial use |url=http://jnst.vn/index.php/nst/article/view/393 |journal=Nuclear Science and Technology |volume=11 |issue=4 |pages=41–50 |doi=10.53747/nst.v11i4.393 |s2cid=255823465 |issn=1810-5408}}

{{main|Cone beam reconstruction}}

Cone beam reconstruction algorithms are similar to typical tomographic reconstruction algorithms, and methods such as filtered backprojection or iterative reconstruction may be used. However, since the reconstruction is three-dimensional, modifications such as the FDK algorithm{{Cite journal|last1=Feldkamp|first1=L. A.|last2=Davis|first2=L. C.|last3=Kress|first3=J. W.|date=1984-06-01|title=Practical cone-beam algorithm|url=https://www.osapublishing.org/josaa/abstract.cfm?uri=josaa-1-6-612|journal=JOSA A|language=EN|volume=1|issue=6|pages=612–619|doi=10.1364/JOSAA.1.000612|issn=1520-8532|bibcode=1984JOSAA...1..612F|citeseerx=10.1.1.331.8312}} may be needed.

{{see also|Ionizing radiation}}

Total radiation doses from 3D dental CBCT exams are 96% lower than conventional CT exams, but deliver 5-16x more radiation than standard dental 2D x-ray (OPG). The time of exposure in CBCT is also comparatively less when compared to conventional CT.

{{cite web|url=https://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm315011.htm|title=Medical X-ray Imaging - Dental Cone-beam Computed Tomography|first=Center for Devices and Radiological|last=Health|website=www.fda.gov|date=28 September 2020}}{{cite web|url=http://www.sedentexct.eu/content/radiation-doses-and-risks-cbct|title=Radiation doses and risks of CBCT - SEDENTEXCT|website=www.sedentexct.eu}}{{cite journal |vauthors=Signorelli L, Patcas R, Peltomäki T, Schätzle M |title=Radiation dose of cone-beam computed tomography compared to conventional radiographs in orthodontics |journal=Journal of Orofacial Orthopedics |volume=77 |issue=1 |pages=9–15 |date=January 2016 |pmid=26747662 |doi= 10.1007/s00056-015-0002-4|s2cid=11664989 }}{{cite journal |vauthors=Grünheid T, Kolbeck Schieck JR, Pliska BT, Ahmad M, Larson BE |title=Dosimetry of a cone-beam computed tomography machine compared with a digital x-ray machine in orthodontic imaging |journal=American Journal of Orthodontics and Dentofacial Orthopedics |volume=141 |issue=4 |pages=436–43 |date=April 2012 |pmid=22464525 |doi=10.1016/j.ajodo.2011.10.024}}{{Cite journal |last1=Yeh |first1=Jih-Kuei |last2=Chen |first2=Chia-Hui |date=2018-08-03 |title=Estimated radiation risk of cancer from dental cone-beam computed tomography imaging in orthodontics patients |journal=BMC Oral Health |volume=18 |issue=1 |pages=131 |doi=10.1186/s12903-018-0592-5 |issn=1472-6831 |pmc=6091080 |pmid=30075771 |doi-access=free }}

CBCT use is only lightly regulated in the US. The recommended standard of care is to use the smallest possible field of view (FOV), the smallest voxel size, the lowest mA setting and the shortest exposure time in conjunction with a pulsed exposure mode of acquisition.{{cite web |author1=American Association of Endodontists |author2=American Academy of Oral and Maxillofacial Radiology |title=Use of Cone-Beam Computed Tomography in Endodontics |url=https://www.aaomr.org/assets/Journal_Publications/Position_Papers/aaomr-aae_position_paper_cb.pdf |access-date=26 May 2021 |date=2010}} International organisations such as the World Health Organization and ICRP, as well as many local bodies and legislation, encourage the idea of justification for all medical exposures, where risks and benefits must be weighed up before a procedure goes ahead.{{cite web|title=Justification of medical exposures|url=https://www.who.int/ionizing_radiation/medical_radiation_exposure/justification/en/|archive-url=https://web.archive.org/web/20160702020002/http://www.who.int/ionizing_radiation/medical_radiation_exposure/justification/en/|url-status=dead|archive-date=July 2, 2016|website=World Health Organization|access-date=31 January 2018}}

There are a number of drawbacks of CBCT technology over that of CT scans, such as increased susceptibility to movement artifacts (in first generation machines) and to the lack of appropriate bone density determination.{{cite journal |vauthors=De Vos W, Casselman J, Swennen GR |title=Cone-beam computerized tomography (CBCT) imaging of the oral and maxillofacial region: a systematic review of the literature |journal=International Journal of Oral and Maxillofacial Surgery |volume=38 |issue=6 |pages=609–25 |date=June 2009 |pmid=19464146 |doi=10.1016/j.ijom.2009.02.028}}

The Hounsfield scale is used to measure radiodensity and, in reference to CT scans, can provide an accurate absolute density for the type of tissue depicted. The radiodensity, measured in Hounsfield Units (HU, also known as CT number) is inaccurate in CBCT scans because different areas in the scan appear with different greyscale values depending on their relative positions in the organ being scanned, despite possessing identical densities, because the image value of a voxel of an organ depends on the position{{clarify|date=March 2016}} in the image volume.{{cite journal |vauthors=Swennen GR, Schutyser F |title=Three-dimensional cephalometry: spiral multi-slice vs cone-beam computed tomography |journal=American Journal of Orthodontics and Dentofacial Orthopedics |volume=130 |issue=3 |pages=410–6 |date=September 2006 |pmid=16979502 |doi=10.1016/j.ajodo.2005.11.035}} HU measured from the same anatomical area with both CBCT and medical-grade CT scanners are not identical{{cite journal |author=Armstrong RT |title=Acceptability of cone beam ct vs. multi-detector CT for 3D Anatomic model construction |journal=Journal of Oral and Maxillofacial Surgery|year=2006 |volume=64 |issue=9 |page=37 |doi=10.1016/j.joms.2006.06.086}} and are thus unreliable for determination of site-specific, radiographically-identified bone density for purposes such as the placement of dental implants, as there is "no good data to relate the CBCT HU values to bone quality."{{cite web |vauthors=Miles DA, Danforth RA |title=A clinician's guide to understanding cone beam volumetric imaging (CBVI) |year=2007 |publisher=INeedCE |url=http://www.ineedce.com/courses/1413/PDF/A_Clin_Gde_ConeBeam.pdf}}

Although some authors have supported the use of CBCT technology to evaluate bone density by measuring HU,{{cite journal |author=Ganz SD |title=Conventional CT and cone beam CT for improved dental diagnostics and implant planning |journal=Dental Implantology Update |volume=16 |issue=12 |pages=89–95 |date=December 2005 |pmid=16422471}}{{cite journal |vauthors=Lee S, Gantes B, Riggs M, Crigger M |title=Bone density assessments of dental implant sites: 3. Bone quality evaluation during osteotomy and implant placement |journal=The International Journal of Oral & Maxillofacial Implants |volume=22 |issue=2 |pages=208–12 |year=2007 |pmid=17465345}} such support is provided erroneously because scanned regions of the same density in the skull can have a different grayscale value in the reconstructed CBCT dataset.{{cite journal |vauthors=Katsumata A, Hirukawa A, Noujeim M |title=Image artifact in dental cone-beam CT |journal=Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics |volume=101 |issue=5 |pages=652–7 |date=May 2006 |pmid=16632279 |doi=10.1016/j.tripleo.2005.07.027|display-authors=etal}}

{{blockquote|X-ray attenuation of CBCT acquisition systems currently produces different HU values for similar bony and soft tissue structures in different areas of the scanned volume (e.g. dense bone has a specific image value at the level of the menton, but the same bone has a significantly different image value at the level of the cranial base).}}

Dental CBCT systems do not employ a standardized system for scaling the grey levels that represent the reconstructed density values and, as such, they are arbitrary and do not allow for assessment of bone quality.{{cite journal |vauthors=Norton MR, Gamble C |title=Bone classification: an objective scale of bone density using the computerized tomography scan |journal=Clinical Oral Implants Research |volume=12 |issue=1 |pages=79–84 |date=February 2001 |pmid=11168274 |doi=10.1034/j.1600-0501.2001.012001079.x}} In the absence of such a standardization, it is difficult to interpret the grey levels or impossible to compare the values resulting from different machines. While there is a general acknowledgment that this deficiency exists with CBCT systems (in that they do not correctly display HU), there has been little research conducted to attempt to correct this deficiency.{{cite journal |vauthors=Mah P, Reeves TE, McDavid WD |title=Deriving Hounsfield units using grey levels in cone beam computed tomography |journal=Dentomaxillofacial Radiology |volume=39 |issue=6 |pages=323–35 |date=September 2010 |pmid=20729181 |pmc=3520236 |doi=10.1259/dmfr/19603304}} See also this linear method adapted to different machines (in {{PMID|29076750}} & citations); and a comparatively unusual neural network approach (in {{PMID|34301984}} & citations).

With time, further advancements in CBCT reconstruction algorithms will allow for improved area detectors,{{cite journal |author=Vannier MW |title=Craniofacial computed tomography scanning: technology, applications and future trends |journal=Orthodontics & Craniofacial Research |volume=6 |pages=23–30; discussion 179–82 |year=2003 |issue=Suppl 1 |pmid=14606531 |doi=10.1034/j.1600-0544.2003.232.x}} and this, together with enhanced postprocessing, will likely solve or reduce this problem. A method for establishing attenuation coefficients with which actual HU values can be derived from CBCT "HU" values was published in 2010 and further research is currently underway to perfect this method in vivo.

While the practicality of CBCT fosters its increasing application in IR, technical limitations hinder its integration into the field. The two most significant factors that affect successful integration are image quality and time (for set up, image acquisition, and image reconstruction). Compared to multidetector computed tomography (MDCT), the wider collimation in CBCT leads to increased scatter radiation and degradation of image quality as demonstrated by artifacts and decreased contrast-to-noise ratio. The temporal resolution of cesium iodide detectors in CBCT slows data acquisition time to approximately 5 to 20 seconds, which increases motion artifacts. The time required for image reconstruction takes longer for CBCT (1 minute) compared to MDCT (real time) due to the computationally demanding cone beam reconstruction algorithms.

• Computed tomography
• Cone beam reconstruction

{{Reflist}}

• Flat-panel volume CT: fundamental principles, technology, and applications. Gupta R, Cheung AC, Bartling SH, Lisauskas J, Grasruck M, Leidecker C, Schmidt B, Flohr T, Brady TJ. Radiographics. 2008 Nov-Dec;28(7):2009-22. {{PMID|19001655}}
• Ultra-high resolution flat-panel volume CT: fundamental principles, design architecture, and system characterization. Gupta R, Grasruck M, Suess C, Bartling SH, Schmidt B, Stierstorfer K, Popescu S, Brady T, Flohr T. Eur Radiol. 2006 Jun;16(6):1191-205. Epub 2006 Mar 10. {{PMID|16528556}}

{{Medical imaging}}

{{DEFAULTSORT:Cone Beam Computed Tomography}}

Category:Dentistry branches

Category:Diagnostic dentistry

Category:Diagnostic radiology

Category:X-ray computed tomography