Editing CT scan (section)

== Types ==
On the basis of image acquisition and procedures, various type of scanners are available in the market.

===Sequential CT===
Sequential CT, also known as step-and-shoot CT, is a type of scanning method in which the CT table moves stepwise. The table increments to a particular location and then stops which is followed by the [[X-ray tube]] rotation and acquisition of a slice. The table then increments again, and another slice is taken. The table movement stops while taking slices. This results in an increased time of scanning.<ref>{{Cite book |last1=Terrier |first1=F. |url=https://books.google.com/books?id=AV3wCAAAQBAJ&dq=Sequential+CT+scan&pg=PA4 |title=Spiral CT of the Abdomen |last2=Grossholz |first2=M. |last3=Becker |first3=C. D. |date=2012-12-06 |publisher=Springer Science & Business Media |isbn=978-3-642-56976-0 |page=4}}</ref>

=== Spiral CT ===
[[File:Drawing of CT fan beam (left) and patient in a CT imaging system.gif|thumb|Drawing of CT fan beam and patient in a CT imaging system]]
[[File:Axial plane CT scan of the thorax illustrative image.jpg|thumb|CT scan of the thorax. The axial slice (right) is the image that corresponds to number 2/33 on the coronal slice (left).]]
Spinning tube, commonly called [[Spiral computed tomography|spiral CT]], or helical CT, is an imaging technique in which an entire [[X-ray tube]] is spun around the central axis of the area being scanned. These are the dominant type of scanners on the market because they have been manufactured longer and offer a lower cost of production and purchase. The main limitation of this type of CT is the bulk and inertia of the equipment (X-ray tube assembly and detector array on the opposite side of the circle) which limits the speed at which the equipment can spin. Some designs use two X-ray sources and detector arrays offset by an angle, as a technique to improve temporal resolution.<ref>{{Cite book |last1=Fishman |first1=Elliot K. |url=https://books.google.com/books?id=aWlrAAAAMAAJ&q=spiral+ct |title=Spiral CT: Principles, Techniques, and Clinical Applications |last2=Jeffrey |first2=R. Brooke |date=1995 |publisher=Raven Press |isbn=978-0-7817-0218-8}}</ref><ref>{{Cite book |last=Hsieh |first=Jiang |url=https://books.google.com/books?id=JX__lLLXFHkC&q=spiral+ct&pg=PA265 |title=Computed Tomography: Principles, Design, Artifacts, and Recent Advances |date=2003 |publisher=SPIE Press |isbn=978-0-8194-4425-7 |page=265}}</ref>

=== Electron beam tomography ===
{{Main|Electron beam computed tomography}}
[[Electron beam tomography]] (EBT) is a specific form of CT in which a large enough X-ray tube is constructed so that only the path of the [[electron]]s, travelling between the [[cathode]] and [[anode]] of the X-ray tube, are spun using [[Deflection yoke|deflection coils]].<ref>{{Cite book |last=Stirrup |first=James |url=https://books.google.com/books?id=SarDDwAAQBAJ&q=ebct&pg=PA6 |title=Cardiovascular Computed Tomography |date=2020-01-02 |publisher=Oxford University Press |isbn=978-0-19-880927-2}}</ref> This type had a major advantage since sweep speeds can be much faster, allowing for less blurry imaging of moving structures, such as the heart and arteries.<ref>{{Cite journal |last1=Talisetti |first1=Anita |last2=Jelnin |first2=Vladimir |last3=Ruiz |first3=Carlos |last4=John |first4=Eunice |last5=Benedetti |first5=Enrico |last6=Testa |first6=Giuliano |last7=Holterman |first7=Ai-Xuan L. |last8=Holterman |first8=Mark J. |date=December 2004 |title=Electron beam CT scan is a valuable and safe imaging tool for the pediatric surgical patient |journal=Journal of Pediatric Surgery |volume=39 |issue=12 |pages=1859–1862 |doi=10.1016/j.jpedsurg.2004.08.024 |issn=1531-5037 |pmid=15616951}}</ref> Fewer scanners of this design have been produced when compared with spinning tube types, mainly due to the higher cost associated with building a much larger X-ray tube and detector array and limited anatomical coverage.<ref>{{Cite journal |last=Retsky |first=Michael |date=31 July 2008 |title=Electron beam computed tomography: Challenges and opportunities |journal=Physics Procedia |volume=1 |issue=1 |pages=149–154 |bibcode=2008PhPro...1..149R |doi=10.1016/j.phpro.2008.07.090 |doi-access=free}}</ref>

=== Dual energy CT ===
Dual energy CT, also known as spectral CT, is an advancement of computed Tomography in which two energies are used to create two sets of data.<ref>{{Cite book |last1=Johnson |first1=Thorsten |url=https://books.google.com/books?id=Etvcnz0mjF4C&q=dual+energy+ct |title=Dual Energy CT in Clinical Practice |last2=Fink |first2=Christian |last3=Schönberg |first3=Stefan O. |last4=Reiser |first4=Maximilian F. |date=2011-01-18 |publisher=Springer Science & Business Media |isbn=978-3-642-01740-7}}</ref> A dual energy CT may employ dual source, single source with dual detector layer, single source with energy switching methods to get two different sets of data.<ref>{{Cite book |last1=Johnson |first1=Thorsten |url=https://books.google.com/books?id=Etvcnz0mjF4C&q=dual+energy+ct |title=Dual Energy CT in Clinical Practice |last2=Fink |first2=Christian |last3=Schönberg |first3=Stefan O. |last4=Reiser |first4=Maximilian F. |date=2011-01-18 |publisher=Springer Science & Business Media |isbn=978-3-642-01740-7 |page=8}}</ref>  

* '''Dual source CT''' is an advanced scanner with a two X-ray tube detector system, unlike conventional single tube systems.<ref>{{Cite book |last1=Carrascosa |first1=Patricia M. |url=https://books.google.com/books?id=wJ2oCgAAQBAJ&q=dual+source+ct |title=Dual-Energy CT in Cardiovascular Imaging |last2=Cury |first2=Ricardo C. |last3=García |first3=Mario J. |last4=Leipsic |first4=Jonathon A. |date=2015-10-03 |publisher=Springer |isbn=978-3-319-21227-2}}</ref><ref>{{Cite journal |last1=Schmidt |first1=Bernhard |last2=Flohr |first2=Thomas |date=2020-11-01 |title=Principles and applications of dual source CT |journal=Physica Medica |series=125 Years of X-Rays |volume=79 |pages=36–46 |doi=10.1016/j.ejmp.2020.10.014 |issn=1120-1797 |pmid=33115699 |s2cid=226056088|doi-access=free}}</ref> These two detector systems are mounted on a single gantry at 90° in the same plane.<ref name="auto1">{{Cite book |last1=Seidensticker |first1=Peter R. |url=https://books.google.com/books?id=oUtHea3ZnJ0C&q=dual+source+ct |title=Dual Source CT Imaging |last2=Hofmann |first2=Lars K. |date=2008-05-24 |publisher=Springer Science & Business Media |isbn=978-3-540-77602-4}}</ref> Dual source CT scanners allow fast scanning with higher temporal resolution by acquiring a full CT slice in only half a rotation. Fast imaging reduces motion blurring at high heart rates and potentially allowing for shorter breath-hold time. This is particularly useful for ill patients having difficulty holding their breath or unable to take heart-rate lowering medication.<ref name="auto1"/><ref>{{Cite journal |last1=Schmidt |first1=Bernhard |last2=Flohr |first2=Thomas |date=2020-11-01 |title=Principles and applications of dual source CT |url=https://www.physicamedica.com/article/S1120-1797(20)30257-X/abstract |journal=Physica Medica: European Journal of Medical Physics |volume=79 |pages=36–46 |doi=10.1016/j.ejmp.2020.10.014 |issn=1120-1797 |pmid=33115699 |s2cid=226056088|doi-access=free}}</ref>
* '''Single source with energy switching''' is another mode of dual energy CT in which a single tube is operated at two different energies by switching the energies frequently.<ref>{{Cite journal |last1=Mahmood |first1=Usman |last2=Horvat |first2=Natally |last3=Horvat |first3=Joao Vicente |last4=Ryan |first4=Davinia |last5=Gao |first5=Yiming |last6=Carollo |first6=Gabriella |last7=DeOcampo |first7=Rommel |last8=Do |first8=Richard K. |last9=Katz |first9=Seth |last10=Gerst |first10=Scott |last11=Schmidtlein |first11=C. Ross |last12=Dauer |first12=Lawrence |last13=Erdi |first13=Yusuf |last14=Mannelli |first14=Lorenzo |date=May 2018 |title=Rapid Switching kVp Dual Energy CT: Value of Reconstructed Dual Energy CT Images and Organ Dose Assessment in Multiphasic Liver CT Exams |journal=European Journal of Radiology |volume=102 |pages=102–108 |doi=10.1016/j.ejrad.2018.02.022 |issn=0720-048X |pmc=5918634 |pmid=29685522}}</ref><ref>{{Cite journal |last=Johnson |first=Thorsten R.C. |date=November 2012 |title=Dual-Energy CT: General Principles |url=https://www.ajronline.org/doi/10.2214/AJR.12.9116 |journal=American Journal of Roentgenology |volume=199 |issue=5_supplement |pages=S3–S8 |doi=10.2214/AJR.12.9116 |pmid=23097165 |issn=0361-803X}}</ref>

=== CT perfusion imaging ===
{{main|CT Perfusion}}
[[File:CT perfusion in M1 artery occlusion.png|thumb|CT Perfusion scan of the brain]]
CT perfusion imaging is a specific form of CT to assess flow through [[blood vessel]]s whilst injecting a [[contrast agent]].<ref name=":0">{{Cite journal |last1=Wittsack |first1=H.-J. |last2=Wohlschläger |first2=A.M. |last3=Ritzl |first3=E.K. |last4=Kleiser |first4=R. |last5=Cohnen |first5=M. |last6=Seitz |first6=R.J. |last7=Mödder |first7=U. |date=2008-01-01 |title=CT-perfusion imaging of the human brain: Advanced deconvolution analysis using circulant singular value decomposition |journal=Computerized Medical Imaging and Graphics |volume=32 |issue=1 |pages=67–77 |doi=10.1016/j.compmedimag.2007.09.004 |issn=0895-6111 |pmid=18029143}}</ref> Blood flow, blood transit time, and organ blood volume, can all be calculated with reasonable [[sensitivity and specificity]].<ref name=":0" /> This type of CT may be used on the [[heart]], although sensitivity and specificity for detecting abnormalities are still lower than for other forms of CT.<ref>{{Cite journal |last1=Williams |first1=M.C. |last2=Newby |first2=D.E. |date=2016-08-01 |title=CT myocardial perfusion imaging: current status and future directions |journal=Clinical Radiology |volume=71 |issue=8 |pages=739–749 |doi=10.1016/j.crad.2016.03.006 |issn=0009-9260 |pmid=27091433}}</ref> This may also be used on the [[brain]], where CT perfusion imaging can often detect poor brain perfusion well before it is detected using a conventional spiral CT scan.<ref name=":0" /><ref name=":1">{{Cite journal |last1=Donahue |first1=Joseph |last2=Wintermark |first2=Max |date=2015-02-01 |title=Perfusion CT and acute stroke imaging: Foundations, applications, and literature review |journal=Journal of Neuroradiology |volume=42 |issue=1 |pages=21–29 |doi=10.1016/j.neurad.2014.11.003 |issn=0150-9861 |pmid=25636991}}</ref> This is better for [[stroke]] diagnosis than other CT types.<ref name=":1" />

=== PET CT ===
{{main|PET-CT}}
[[File:Petct1.jpg|thumb|left|PET-CT scan of chest]]
Positron emission tomography–computed tomography is a hybrid CT modality which combines, in a single gantry, a [[positron emission tomography]] (PET) scanner and an X-ray computed tomography (CT) scanner, to acquire sequential images from both devices in the same session, which are combined into a single superposed ([[Image registration|co-registered]]) image. Thus, [[functional imaging]] obtained by PET, which depicts the spatial distribution of metabolic or biochemical activity in the body can be more precisely aligned or correlated with anatomic imaging obtained by CT scanning.<ref>{{Cite journal |last1=Blodgett |first1=Todd M. |last2=Meltzer |first2=Carolyn C. |last3=Townsend |first3=David W. |date=February 2007 |title=PET/CT: form and function |url=https://pubmed.ncbi.nlm.nih.gov/17255408/#:~:text=CT%20is%20complementary%20in%20the,identify%20and%20localize%20functional%20abnormalities. |journal=Radiology |volume=242 |issue=2 |pages=360–385 |doi=10.1148/radiol.2422051113 |issn=0033-8419 |pmid=17255408}}</ref>

PET-CT gives both anatomical and functional details of an organ under examination and is helpful in detecting different type of cancers.<ref>{{Cite journal |last1=Ciernik |first1=I.Frank |last2=Dizendorf |first2=Elena |last3=Baumert |first3=Brigitta G |last4=Reiner |first4=Beatrice |last5=Burger |first5=Cyrill |last6=Davis |first6=J.Bernard |last7=Lütolf |first7=Urs M |last8=Steinert |first8=Hans C |last9=Von Schulthess |first9=Gustav K |date=November 2003 |title=Radiation treatment planning with an integrated positron emission and computer tomography (PET/CT): a feasibility study |url=https://doi.org/10.1016/S0360-3016(03)00346-8 |journal=International Journal of Radiation Oncology, Biology, Physics |volume=57 |issue=3 |pages=853–863 |doi=10.1016/s0360-3016(03)00346-8 |pmid=14529793 |issn=0360-3016}}</ref><ref>{{Cite journal |last1=Ul-Hassan |first1=Fahim |last2=Cook |first2=Gary J |date=August 2012 |title=PET/CT in oncology |journal=Clinical Medicine |volume=12 |issue=4 |pages=368–372 |doi=10.7861/clinmedicine.12-4-368 |issn=1470-2118 |pmc=4952129 |pmid=22930885}}</ref>