Editing CT scan (section)

=== Cancer ===
{{Main|Radiation-induced cancer}}
The [[ionizing radiation|radiation]] used in CT scans can damage body cells, including [[DNA molecule]]s, which can lead to [[radiation-induced cancer]].<ref name="Brenner2007">{{Cite journal |vauthors=Brenner DJ, Hall EJ |date=November 2007 |title=Computed tomography – an increasing source of radiation exposure |url=http://www.columbia.edu/~djb3/papers/nejm1.pdf |url-status=live |journal=N. Engl. J. Med. |volume=357 |issue=22 |pages=2277–84 |doi=10.1056/NEJMra072149 |pmid=18046031 |archive-url=https://web.archive.org/web/20160304060542/http://www.columbia.edu/~djb3/papers/nejm1.pdf |archive-date=2016-03-04 |s2cid=2760372}}</ref> The radiation doses received from CT scans is variable. Compared to the lowest dose X-ray techniques, CT scans can have 100 to 1,000 times higher dose than conventional X-rays.<ref name="Redberg">Redberg, Rita F., and Smith-Bindman, Rebecca. [https://www.nytimes.com/2014/01/31/opinion/we-are-giving-ourselves-cancer.html "We Are Giving Ourselves Cancer"] {{webarchive|url=https://web.archive.org/web/20170706163542/https://www.nytimes.com/2014/01/31/opinion/we-are-giving-ourselves-cancer.html?nl=opinion&emc=edit_ty_20140131&_r=0 |date=2017-07-06 }}, ''New York Times'', January 30, 2014</ref> However, a lumbar spine X-ray has a similar dose as a head CT.<ref>{{Cite web |last=Health |first=Center for Devices and Radiological |title=Medical X-ray Imaging – What are the Radiation Risks from CT? |url=https://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm115329.htm |url-status=live |archive-url=https://web.archive.org/web/20131105050317/https://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm115329.htm |archive-date=5 November 2013 |access-date=1 May 2018 |website=www.fda.gov}}</ref> Articles in the media often exaggerate the relative dose of CT by comparing the lowest-dose X-ray techniques (chest X-ray) with the highest-dose CT techniques. In general, a routine abdominal CT has a radiation dose similar to three years of average [[background radiation]].<ref>{{Cite web |last1=Radiological Society of North America |last2=American College of Radiology |date=February 2021 |title=Patient Safety – Radiation Dose in X-Ray and CT Exams |url=https://www.acr.org/-/media/ACR/Files/Radiology-Safety/Radiation-Safety/Dose-Reference-Card.pdf |url-status=dead |archive-url=https://web.archive.org/web/20210101161039/https://www.acr.org/-/media/ACR/Files/Radiology-Safety/Radiation-Safety/Dose-Reference-Card.pdf |archive-date=1 January 2021 |access-date=6 April 2021 |website=acr.org |author1-link=Radiological Society of North America |author2-link=American College of Radiology }}</ref>

Large scale population-based studies have consistently demonstrated that low dose radiation from CT scans has impacts on cancer incidence in a variety of cancers.<ref name="MathewsForsythe2013">{{Cite journal |last1=Mathews |first1=J. D. |last2=Forsythe |first2=A. V. |last3=Brady |first3=Z. |last4=Butler |first4=M. W. |last5=Goergen |first5=S. K. |last6=Byrnes |first6=G. B. |last7=Giles |first7=G. G. |last8=Wallace |first8=A. B. |last9=Anderson |first9=P. R. |last10=Guiver |first10=T. A. |last11=McGale |first11=P. |last12=Cain |first12=T. M. |last13=Dowty |first13=J. G. |last14=Bickerstaffe |first14=A. C. |last15=Darby |first15=S. C. |year=2013 |title=Cancer risk in 680 000 people exposed to computed tomography scans in childhood or adolescence: data linkage study of 11 million Australians |journal=BMJ |volume=346 |issue=may21 1 |pages=f2360 |doi=10.1136/bmj.f2360 |issn=1756-1833 |pmc=3660619 |pmid=23694687}}</ref><ref name="pearce_ctscans">{{cite journal |last1=Pearce |first1=MS |last2=Salotti |first2=JA |last3=Little |first3=MP |last4=McHugh |first4=K |last5=Lee |first5=C |last6=Kim |first6=KP |last7=Howe |first7=NL |last8=Ronckers |first8=CM |last9=Rajaraman |first9=P |last10=Sir Craft |first10=AW |last11=Parker |first11=L |last12=Berrington de González |first12=A |title=Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study. |journal=Lancet |date=4 August 2012 |volume=380 |issue=9840 |pages=499–505 |doi=10.1016/S0140-6736(12)60815-0 |pmid=22681860|pmc=3418594 }}</ref><ref name="meulepas2019">{{cite journal |last1=Meulepas |first1=Johanna M |last2=Ronckers |first2=Cécile M |last3=Smets |first3=Anne M J B |last4=Nievelstein |first4=Rutger A J |last5=Gradowska |first5=Patrycja |last6=Lee |first6=Choonsik |last7=Jahnen |first7=Andreas |last8=van Straten |first8=Marcel |last9=de Wit |first9=Marie-Claire Y |last10=Zonnenberg |first10=Bernard |last11=Klein |first11=Willemijn M |last12=Merks |first12=Johannes H |last13=Visser |first13=Otto |last14=van Leeuwen |first14=Flora E |last15=Hauptmann |first15=Michael |title=Radiation Exposure From Pediatric CT Scans and Subsequent Cancer Risk in the Netherlands |journal=JNCI: Journal of the National Cancer Institute |date=1 March 2019 |volume=111 |issue=3 |pages=256–263 |doi=10.1093/jnci/djy104|pmid=30020493 |pmc=6657440 }}</ref><ref name="berrington2016">{{cite journal |last1=de Gonzalez |first1=Amy Berrington |last2=Salotti |first2=Jane A |last3=McHugh |first3=Kieran |last4=Little |first4=Mark P |last5=Harbron |first5=Richard W |last6=Lee |first6=Choonsik |last7=Ntowe |first7=Estelle |last8=Braganza |first8=Melissa Z |last9=Parker |first9=Louise |last10=Rajaraman |first10=Preetha |last11=Stiller |first11=Charles |last12=Stewart |first12=Douglas R |last13=Craft |first13=Alan W |last14=Pearce |first14=Mark S |title=Relationship between paediatric CT scans and subsequent risk of leukaemia and brain tumours: assessment of the impact of underlying conditions |journal=British Journal of Cancer |date=February 2016 |volume=114 |issue=4 |pages=388–394 |doi=10.1038/bjc.2015.415|pmid=26882064 |pmc=4815765 }}</ref> For example, in a large population-based Australian cohort it was found that up to 3.7% of brain cancers were caused by CT scan radiation.<ref name="nrsCT1">{{cite journal |last1=Smoll |first1=Nicolas R |last2=Brady |first2=Zoe |last3=Scurrah |first3=Katrina J |last4=Lee |first4=Choonsik |last5=Berrington de González |first5=Amy |last6=Mathews |first6=John D |title=Computed tomography scan radiation and brain cancer incidence |journal=Neuro-Oncology |date=14 January 2023 |volume=25 |issue=7 |pages=1368–1376 |doi=10.1093/neuonc/noad012|pmid=36638155 |pmc=10326490 }}</ref> Some experts project that in the future, between three and five percent of all cancers would result from medical imaging.<ref name="Redberg" /> An Australian study of 10.9&nbsp;million people reported that the increased incidence of cancer after CT scan exposure in this cohort was mostly due to irradiation. In this group, one in every 1,800 CT scans was followed by an excess cancer. If the lifetime risk of developing cancer is 40% then the absolute risk rises to 40.05% after a CT. The risks of CT scan radiation are especially important in patients undergoing recurrent CT scans within a short time span of one to five years.<ref name="SasieniShelton2011">{{Cite journal |last1=Sasieni |first1=P D |last2=Shelton |first2=J |last3=Ormiston-Smith |first3=N |last4=Thomson |first4=C S |last5=Silcocks |first5=P B |year=2011 |title=What is the lifetime risk of developing cancer?: the effect of adjusting for multiple primaries |journal=British Journal of Cancer |volume=105 |issue=3 |pages=460–465 |doi=10.1038/bjc.2011.250 |issn=0007-0920 |pmc=3172907 |pmid=21772332}}</ref><ref name="Patients undergoing recurrent CT sc">{{Cite journal |last1=Rehani |first1=Madan M. |last2=Yang |first2=Kai |last3=Melick |first3=Emily R. |last4=Heil |first4=John |last5=Šalát |first5=Dušan |last6=Sensakovic |first6=William F. |last7=Liu |first7=Bob |year=2020 |title=Patients undergoing recurrent CT scans: assessing the magnitude |journal=European Radiology |volume=30 |issue=4 |pages=1828–1836 |doi=10.1007/s00330-019-06523-y |pmid=31792585 |s2cid=208520824}}</ref><ref name="Multinational data on cumulative ra">{{Cite journal |last1=Brambilla |first1=Marco |last2=Vassileva |first2=Jenia |last3=Kuchcinska |first3=Agnieszka |last4=Rehani |first4=Madan M. |year=2020 |title=Multinational data on cumulative radiation exposure of patients from recurrent radiological procedures: call for action |journal=European Radiology |volume=30 |issue=5 |pages=2493–2501 |doi=10.1007/s00330-019-06528-7 |pmid=31792583 |s2cid=208520544}}</ref>

Some experts note that CT scans are known to be "overused," and "there is distressingly little evidence of better health outcomes associated with the current high rate of scans."<ref name="Redberg" /> On the other hand, a recent paper analyzing the data of patients who received high [[cumulative dose]]s showed a high degree of appropriate use.<ref name="Patients undergoing recurrent CT ex">{{Cite journal |last1=Rehani |first1=Madan M. |last2=Melick |first2=Emily R. |last3=Alvi |first3=Raza M. |last4=Doda Khera |first4=Ruhani |last5=Batool-Anwar |first5=Salma |last6=Neilan |first6=Tomas G. |last7=Bettmann |first7=Michael |year=2020 |title=Patients undergoing recurrent CT exams: assessment of patients with non-malignant diseases, reasons for imaging and imaging appropriateness |journal=European Radiology |volume=30 |issue=4 |pages=1839–1846 |doi=10.1007/s00330-019-06551-8 |pmid=31792584 |s2cid=208520463}}</ref> This creates an important issue of cancer risk to these patients. Moreover, a highly significant finding that was previously unreported is that some patients received >100 mSv dose from CT scans in a single day,<ref name="Patients undergoing recurrent CT sc" /> which counteracts existing criticisms some investigators may have on the effects of protracted versus acute exposure.

There are contrarian views and the debate is ongoing. Some studies have shown that publications indicating an increased risk of cancer from typical doses of body CT scans are plagued with serious methodological limitations and several highly improbable results,<ref>{{Cite journal |last1=Eckel |first1=Laurence J. |last2=Fletcher |first2=Joel G. |last3=Bushberg |first3=Jerrold T. |last4=McCollough |first4=Cynthia H. |date=2015-10-01 |title=Answers to Common Questions About the Use and Safety of CT Scans |url=https://www.mayoclinicproceedings.org/article/S0025-6196(15)00591-1/fulltext |journal=Mayo Clinic Proceedings |volume=90 |issue=10 |pages=1380–1392 |doi=10.1016/j.mayocp.2015.07.011 |issn=0025-6196 |pmid=26434964 |doi-access=free}}</ref> concluding that no evidence indicates such low doses cause any long-term harm.<ref>{{Cite web |title=Expert opinion: Are CT scans safe? |url=https://www.sciencedaily.com/releases/2015/10/151005151507.htm |access-date=2019-03-14 |website=ScienceDaily}}</ref><ref>{{Cite journal |last1=McCollough |first1=Cynthia H. |last2=Bushberg |first2=Jerrold T. |last3=Fletcher |first3=Joel G. |last4=Eckel |first4=Laurence J. |date=2015-10-01 |title=Answers to Common Questions About the Use and Safety of CT Scans |url=https://www.mayoclinicproceedings.org/article/S0025-6196(15)00591-1/abstract |journal=Mayo Clinic Proceedings |volume=90 |issue=10 |pages=1380–1392 |doi=10.1016/j.mayocp.2015.07.011 |issn=0025-6196 |pmid=26434964 |doi-access=free}}</ref><ref>{{Cite web |date=4 February 2016 |title=No evidence that CT scans, X-rays cause cancer |url=https://www.medicalnewstoday.com/articles/306067.php |access-date=2019-03-14 |website=Medical News Today}}</ref>
One study estimated that as many as 0.4% of cancers in the United States resulted from CT scans, and that this may have increased to as much as 1.5 to 2% based on the rate of CT use in 2007.<ref name="Brenner2007" /> Others dispute this estimate,<ref>{{Cite journal |last1=Kalra |first1=Mannudeep K. |last2=Maher |first2=Michael M. |last3=Rizzo |first3=Stefania |last4=Kanarek |first4=David |last5=Shephard |first5=Jo-Anne O. |date=April 2004 |title=Radiation exposure from Chest CT: Issues and Strategies |journal=Journal of Korean Medical Science |volume=19 |issue=2 |pages=159–166 |doi=10.3346/jkms.2004.19.2.159 |issn=1011-8934 |pmc=2822293 |pmid=15082885}}</ref> as there is no consensus that the low levels of radiation used in CT scans cause damage. Lower radiation doses are used in many cases, such as in the investigation of renal colic.<ref>{{Cite journal |last1=Rob |first1=S. |last2=Bryant |first2=T. |last3=Wilson |first3=I. |last4=Somani |first4=B.K. |year=2017 |title=Ultra-low-dose, low-dose, and standard-dose CT of the kidney, ureters, and bladder: is there a difference? Results from a systematic review of the literature |journal=Clinical Radiology |volume=72 |issue=1 |pages=11–15 |doi=10.1016/j.crad.2016.10.005 |pmid=27810168}}</ref>

<!--Effect of age  -->
A person's age plays a significant role in the subsequent risk of cancer.<ref name="Furlow2010" /> Estimated lifetime cancer mortality risks from an abdominal CT of a one-year-old is 0.1%, or 1:1000 scans.<ref name="Furlow2010" /> The risk for someone who is 40 years old is half that of someone who is 20 years old with substantially less risk in the elderly.<ref name="Furlow2010" /> The [[International Commission on Radiological Protection]] estimates that the risk to a fetus being exposed to 10 [[mGy]] (a unit of radiation exposure) increases the rate of cancer before 20 years of age from 0.03% to 0.04% (for reference a CT pulmonary angiogram exposes a fetus to 4&nbsp;mGy).<ref name="Risk2011" /> A 2012 review did not find an association between medical radiation and cancer risk in children noting however the existence of limitations in the evidences over which the review is based.<ref>{{Cite journal |vauthors=Baysson H, Etard C, Brisse HJ, Bernier MO |date=January 2012 |title=[Diagnostic radiation exposure in children and cancer risk: current knowledge and perspectives] |journal=Archives de Pédiatrie |volume=19 |issue=1 |pages=64–73 |doi=10.1016/j.arcped.2011.10.023 |pmid=22130615}}</ref> CT scans can be performed with different settings for lower exposure in children with most manufacturers of CT scans as of 2007 having this function built in.<ref name="Semelka2007" /> Furthermore, certain conditions can require children to be exposed to multiple CT scans.<ref name="Brenner2007" /> 

Current recommendations are to inform patients of the risks of CT scanning.<ref name="pmid17646450">{{Cite journal |vauthors=Larson DB, Rader SB, Forman HP, Fenton LZ |date=August 2007 |title=Informing parents about CT radiation exposure in children: it's OK to tell them |journal=Am J Roentgenol |volume=189 |issue=2 |pages=271–5 |doi=10.2214/AJR.07.2248 |pmid=17646450 |s2cid=25020619}}</ref> However, employees of imaging centers tend not to communicate such risks unless patients ask.<ref>{{Citation |last1=Emmerson |first1=Benjamin |title=Radiology Patient Safety and Communication |date=2023 |url=https://www.ncbi.nlm.nih.gov/books/NBK567713 |work=StatPearls |access-date=2023-11-24 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=33620790 |last2=Young |first2=Michael}}</ref>