Editing Orthovoltage X-rays

{{Use American English|date = February 2019}}
{{Short description|High energy (100–500 KeV) X-rays}}
{{Infobox medical intervention |
  Name        = Orthovoltage X-rays |
  Image       = File:Radiumhemmet röntgenapparat 1938.jpg |
  Caption     = A 200&nbsp;kV orthovoltage X-ray tube used for radiation therapy, 1938. Orthovoltage X-ray machines are similar to diagnostic ([[radiography]]) [[X-ray machines]], except that higher voltages are used and the X-ray tube is longer, to prevent the high voltages from arcing across the tube.
  ICD10       = |
  ICD9unlinked = {{ICD9proc|92.22}}  |
  MeshID      = |
  OPS301      = {{OPS301|8-521}} |
  OtherCodes  = |
}}

'''Orthovoltage X-rays''' are produced by [[X-ray tube]]s operating at [[voltage]]s in the 100&ndash;500 [[kilovolt|kV]] range, and therefore the X-rays have a peak [[energy]] in the 100&ndash;500 [[kiloelectronvolt|keV]] range.<ref name="IAEAradonc">{{cite book|last1=Podgorsak|first1=E. B.|title=Radiation oncology physics: a handbook for teachers and students|date=2005|publisher=International Atomic Energy Agency|location=Vienna|isbn=978-92-0-107304-4|page=125|chapter-url=http://www-pub.iaea.org/books/IAEABooks/7086/Radiation-Oncology-Physics|chapter=Treatment Machines for External Beam Radiotherapy}}</ref> Orthovoltage X-rays are sometimes termed '''"deep" X-rays''' (DXR).<ref>{{cite book|last1=Cerry|first1=Pam|last2=Duxbury|first2=Angela|title=Practical Radiotherapy: Physics and Equipment|date=1998|publisher=Greenwich Medical Media|location=London|isbn=9781900151061|page=107|url=https://books.google.com/books?id=5WIBbmmDm-gC&pg=PA107|language=en}}</ref> They cover the upper limit of energies used for diagnostic [[radiography]], and are used in [[external beam radiotherapy]] to treat [[cancer]] and [[tumor]]s.  They penetrate tissue to a useful depth of about 4&ndash;6&nbsp;cm.<ref>{{cite journal|last1=Hill|first1=Robin|last2=Healy|first2=Brendan|last3=Holloway|first3=Lois|last4=Kuncic|first4=Zdenka|last5=Thwaites|first5=David|last6=Baldock|first6=Clive|title=Advances in kilovoltage x-ray beam dosimetry|journal=Physics in Medicine and Biology|date=21 March 2014|volume=59|issue=6|pages=R183–R231|doi=10.1088/0031-9155/59/6/R183|pmid=24584183|doi-access=|bibcode=2014PMB....59R.183H}}</ref> This makes them useful for treating [[skin]], superficial tissues, and ribs, but not for deeper structures such as [[lungs]] or pelvic organs.<ref>{{cite book|last1=Hansen|first1=Eric|last2=Roach III|first2=Mack|title=Handbook of Evidence-based Radiation Oncology|date=2007|publisher=Springer|location=New York|isbn=9780387306476|url=https://books.google.com/books?id=8mtpTqetJlQC&pg=PA5|language=en|page=5}}</ref> The relatively low energy of orthovoltage X-rays causes them to interact with matter via different physical mechanisms compared to higher energy [[megavoltage X-rays]] or radionuclide [[γ-rays]], increasing their [[relative biological effectiveness]]. <ref>{{cite journal |last1=Bell |first1=Brett I. |last2=Vercellino |first2=Justin |last3=Brodin |first3=N. Patrik |last4=Velten |first4=Christian |last5=Nanduri |first5=Lalitha S.Y. |last6=Nagesh |first6=Prashanth K.B. |last7=Tanaka |first7=Kathryn E. |last8=Fang |first8=Yanan |last9=Wang |first9=Yanhua |last10=Macedo |first10=Rodney |last11=English |first11=Jeb |last12=Schumacher |first12=Michelle M. |last13=Duddempudi |first13=Phaneendra K. |last14=Asp |first14=Patrik |last15=Koba |first15=Wade |last16=Shajahan |first16=Shahin |last17=Liu |first17=Laibin |last18=Tomé |first18=Wolfgang A. |last19=Yang |first19=Weng-Lang |last20=Kolesnick |first20=Richard |last21=Guha |first21=Chandan |title=Orthovoltage X-Rays Exhibit Increased Efficacy Compared with γ-Rays in Preclinical Irradiation |journal=Cancer Research |date=3 August 2022 |volume=82 |issue=15 |pages=2678–2691 |doi=10.1158/0008-5472.CAN-22-0656|pmid=35919990 |pmc=9354647 }}</ref>

==History==
The energy and penetrating ability of the X-rays produced by an X-ray tube increases with the [[voltage]] on the tube.  External beam radiotherapy began around the turn of the 20th century with ordinary diagnostic X-ray tubes, which used voltages below 150&nbsp;kV.<ref>{{cite book|last1=Zaidi|first1=Zohra|last2=Walton|first2=Shernaz|title=A Manual of Dermatology|date=2013|publisher=JP Brothers Medical|location=New Delhi|isbn=9789350904589|page=872|url=https://books.google.com/books?id=Mgm8K94t0N4C&pg=PA872|language=en}}</ref> Physicians found that these were adequate for treating superficial tumors, but not tumors inside the body. Since these low energy X-rays were mostly absorbed in the first few centimeters of tissue, to deliver a large enough radiation dose to buried tumors would cause severe skin burns.<ref>{{cite book|last1=Khan|first1=Faiz M.|last2=Gibbons|first2=John P.|title=Khan's The Physics of Radiation Therapy|date=2014|publisher=Lippincott Williams & Wilkins|location=Philadelphia|isbn=9781469881263|page=41|edition=5th|url=https://books.google.com/books?id=nSNBAwAAQBAJ&pg=PA41|language=en}}</ref>

Therefore beginning in the 1920s "orthovoltage" 200&ndash;500 kV X-ray machines were built.<ref>{{cite book|last1=Linz|first1=Ute|title=Ion Beam Therapy|volume=320|date=2011|publisher=Springer|location=Berlin|isbn=978-3-642-21413-4|page=6|edition=1st|chapter=From X-Rays to Ion Beams: A Short History of Radiation Therapy|chapter-url=http://media.axon.es/pdf/98285_1.pdf|doi=10.1007/978-3-642-21414-1_1|series=Biological and Medical Physics, Biomedical Engineering}}</ref> These were found to be able to reach shallow tumors, but to treat tumors deep in the body more voltage was needed.   By the 1930s and 1940s [[megavoltage X-rays]] produced by huge machines with 3–5 million volts on the tube, began to be employed.  With the introduction of [[linear accelerator]]s in the 1970s, which could produce 4–30&nbsp;MV beams, orthovoltage X-rays are now considered quite shallow.<ref>{{cite book|last1=Cognetta|first1=Armand B.|last2=Mendenhall|first2=William M.|title=Radiation Therapy for Skin Cancer|date=2013|publisher=Springer|location=New York|isbn=9781461469865|page=33|url=https://books.google.com/books?id=sX9DAAAAQBAJ&pg=PA33|language=en}}</ref>

==See also==
* [[Megavoltage X-rays]]

==References==
{{Reflist}}

{{Radiation oncology}}

[[Category:Radiation therapy]]
[[Category:X-rays]]