computerized tomography (CT)
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Indications
- examination of intracranial structures (MRI is the imaging modality of choice)
- skeletal trauma
- head injury
- fractures of the vertebral column
- fractures of pelvic bones
- especially fracture-dislocation of the acetabulum
- localization & staging of tumors
- localization of brain tumors
- staging of tumors of the larynx
- staging of GI tumors
- pelvic tumors (MRI may be imaging modality of choice)
- high-resolution CT is the imaging modality of choice for bronchiectasis
- helical CT may be useful diagnosis of pulmonary embolism
- assessment of ectopic/dystrophic calcification
- non-invasive coronary artery imaging (CT angiography)[5]
Contraindications
- caution for procedures using contrast agent
- presence of insulin pump, cardiac implantable electronic device*, or neurostimulator should NOT preclude performance of an appropriate, medically indicated CT scan[15]
* pacemaker, implantable cardioverter defibrillator
Procedure
- CT images are obtained by computed reconstruction from measurements of differential X-ray absorbtion obtained through an angle of 360 degrees.
- these measurements obtained by electronic detection allow calculation of radiographic densities at any point in plane represented as pixels in the CT software
- radiographic densities are measured in Hounsfield units
- conventional CT examines 8-10 mm slices obtained at 10 mm intervals
- high-resolution CT (HRCT) examines 1-2 mm slices & delineates detail that convention CT does not
- helical or spiral CT allows 3-dimensional data acquistion & reduces motion artifact
- contrast is generally used to identify vasculature or the gastrointestinal tract
- Naeotom Alpha CT utilizes photon-counting detectors that can count individual x-ray photons that pass through a patient & discriminate their energy[18]
- current CT imaging systems are capable of measuring cumulative energy from numerous x-rays at once
- photon-counting CT scan can reduce radiation exposure for patients & the need for contrast agents.
- photon-counting CT scan can work with images that visualize even very fine tissue structures, such as the smaller bronchi of the lungs or metastases in bones[18]
Complications
- radiation exposure:
- head CT delivers > 100 mGy of X-rays[3]
- abdominal CT delivers 50-fold more radiation than plain films[6]
- exposure to about 9-10 mSv of radiation with CT of the neck, chest, abdomen, or pelvis[8]; 5-7 mSv[2]
- 1 cancer per 1000 patients receiving 10 mSv of radiation[8]
- radiation exposure from CT may cause 1.5-2% of cancers in USA[6]
- 30 solid tumors per 10,000 scans in girls & about 14 in boys[12]
- radiation from childhood CT increase risk for brain tumors & leukemia[9]
- 2-3 head CTs in children under age 15 years may triple risk for brain tumors
- 5-10 CTs may triple risk for leukemias
- absolute risk is small
- 1 excess leukemia & 1 excess brain tumor per 10,000 head CTs before age 10[9]
- relative risk = 1.24[11]
- higher rates of cancer in children who underwent computed tomography than in those who did not[17]
- x-rays used during CT examinations may cause some implanted & external electronic medical devices to malfunction (most patients with electronic medical devices undergo CT scans without any adverse consequences)[7]
- patients rarely warned about radiation hazzards from CT scans[13]
- use of CT in children is diminishing[14]
- no evidence of contrast nephropathy from contrast agents used in computed tomography[16]
More general terms
More specific terms
- cardiac computed tomography angiography; coronary computed tomography angiography; CT angiography (CCTA)
- computed tomography angiography (CT angiography)
- CT enterography; computed tomography enterography
- CT for placement of radiation therapy fields
- CT guidance for procedure
- CT of abdomen
- CT of abdomen & pelvis
- CT of ankle
- CT of calcaneus
- CT of cervical & lumbar spine
- CT of cervical & thoracic spine
- CT of cervical spine
- CT of chest & abdomen & pelvis
- CT of chest; CT of thorax
- CT of clavicle
- CT of elbow
- CT of face & neck (soft tissues)
- CT of facial bones & maxilla
- CT of facial bones & sinuses
- CT of femur
- CT of foot
- CT of forearm
- CT of hand
- CT of head
- CT of head & cervical spine
- CT of head & mandible
- CT of head & maxillofacial region
- CT of head & neck
- CT of head & temporal bone
- CT of hip
- CT of kidney
- CT of knee
- CT of liver
- CT of lower extremity
- CT of lower leg
- CT of lumbar spine
- CT of lumbar spine & sacrum
- CT of neck & superior mediastinum
- CT of neck (soft tissues)
- CT of orbit, sella, posterior fossa, or ear
- CT of pancreas
- CT of pelvis
- CT of pelvis & lower extremity
- CT of posterior fossa
- CT of sacroiliac joint
- CT of sacrum
- CT of sacrum & coccyx
- CT of scapula
- CT of sella turcica
- CT of shoulder
- CT of sinus
- CT of sinuses & mandible
- CT of spine; CT of vertebral column
- CT of spleen
- CT of temporomandibular joint (TMJ)
- CT of thoracic & lumbar spine
- CT of thoracic spine
- CT of thumb
- CT of toe
- CT of upper extremity
- CT of wrist
- electromagnetic navigation
- MRI of temporomandibular joint (TMJ)
- optical coherence tomography (OCT)
- single photon emission computed tomography (SPECT)
- virtual (CT) colonoscopy (CT colonography)
- whole-body computerized tomography (CT)
Additional terms
References
- ↑ Introduction to Clinical Imaging, Radiology Syllabus, UCSF, 1993
- ↑ Jump up to: 2.0 2.1 Medical Knowledge Self Assessment Program (MKSAP) 11, 16. American College of Physicians, Philadelphia 1998, 2012
- ↑ Jump up to: 3.0 3.1 3.2 Journal Watch 24(4):34, 2004 Hall P et al, Effect of low doses of ionising radiation in infancy on cognitive function in adulthood: Swedish population based cohort study. BMJ 328:19, 2004 PMID: https://www.ncbi.nlm.nih.gov/pubmed/14703539
Hall P et al http://bmj.bmjjournals.com/cgi/content/full/328/7430/19 - ↑ Jump up to: 4.0 4.1 Journal Watch 24(5):37, 2004 Greenland P et al, Coronary artery calcium score combined with Framingham score for risk prediction in asymptomatic individuals. JAMA 291:210, 2004 PMID: https://www.ncbi.nlm.nih.gov/pubmed/14722147
- ↑ Jump up to: 5.0 5.1 van Mieghem CAG et al, Multislice spiral computed tomography for the evaluation of stent patency after left main coronary artery stenting: A comparison with conventional coronary angiography and intravascuscular ultrasound. Circulation 2006, 114:645 PMID: https://www.ncbi.nlm.nih.gov/pubmed/16894038
Kimmelstiel C, Multislice computed tomography after left main drug-eluting stenting: Are we putting the CarT before the horse? Circulation 2006, 114:616 PMID: https://www.ncbi.nlm.nih.gov/pubmed/16908783 - ↑ Jump up to: 6.0 6.1 6.2 Brenner DJ and Hall EJ Computed tomography - An increasing source of radiation exposure. N Engl J Med 2007, 357:2277 PMID: https://www.ncbi.nlm.nih.gov/pubmed/18046031
- ↑ Jump up to: 7.0 7.1 FDA MedWatch http://www.fda.gov/medwatch/safety/2008/safety08.htm#ElectronicMedical
- ↑ Jump up to: 8.0 8.1 8.2 Griffey RT and Sodickson A. Cumulative radiation exposure and cancer risk estimates in emergency department patients undergoing repeat or multiple CT. AJR Am J Roentgenol 2009 Apr; 192:887. PMID: https://www.ncbi.nlm.nih.gov/pubmed/19304691
- ↑ Jump up to: 9.0 9.1 9.2 Pearce MS et al Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study The Lancet, Early Online Publication, 7 June 2012 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/22681860 <Internet> http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(12)60815-0/abstract
Einstein AJ Beyond the bombs: cancer risks of low-dose medical radiation The Lancet, Early Online Publication, 7 June 2012 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/22681861 <Internet> http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(12)60897-6/fulltext - ↑ Smith-Bindman R, Lipson J, Marcus R et al Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer. Arch Intern Med. 2009 Dec 14;169(22):2078-86 PMID: https://www.ncbi.nlm.nih.gov/pubmed/20008690
- ↑ Jump up to: 11.0 11.1 Mathews JD et al Cancer risk in 680,000 people exposed to computed tomography scans in childhood or adolescence: data linkage study of 11 million Australians. BMJ 2013;346:f2360 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/23694687 <Internet> http://www.bmj.com/content/346/bmj.f2360
Sodickson A CT radiation risks coming into clearer focus. BMJ 2013;346:f3102 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/23694689 <Internet> http://www.bmj.com/content/346/bmj.f3102 - ↑ Jump up to: 12.0 12.1 Miglioretti DL et al The Use of Computed Tomography in Pediatrics and the Associated Radiation Exposure and Estimated Cancer Risk. JAMA Pediatr. 2013;():1-8. June 10, 2013 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/23754213 <Internet> http://archpedi.jamanetwork.com/article.aspx?articleid=1696279
Schroeder AR and Redber RF The Harm in Looking JAMA Pediatr. 2013;():1-3. June 10, 2013 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/23753832 <Internet> http://archpedi.jamanetwork.com/article.aspx?articleid=1696281 - ↑ Jump up to: 13.0 13.1 Young K, Fairchild DG, Di Francesco L Patients Rarely Warned About Radiation Hazards from CT Imaging Physician's First Watch, Jan 28, 2015 David G. Fairchild, MD, MPH, Editor-in-Chief Massachusetts Medical Society http://www.jwatch.org
Consumer Reports. Jan 27, 2015 The surprising dangers of CT scans and X-rays. Patients are often exposed to cancer-causing radiation for little medical reason, a Consumer Reports investigation finds. http://www.consumerreports.org/cro/magazine/2015/01/the-surprising-dangers-of-ct-sans-and-x-rays/index.htm - ↑ Jump up to: 14.0 14.1 Parker MW et al Computed Tomography and Shifts to Alternate Imaging Modalities in Hospitalized Children. Pediatrics. August 24, 2015. <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/26304828 <Internet> http://pediatrics.aappublications.org/content/early/2015/08/18/peds.2015-0995
- ↑ Jump up to: 15.0 15.1 FDA Safety Alert. April 1, 2016 Interference between Computed Tomography (CT) and Electronic Medical Devices: Notification - Current Understanding of Potential Risk. http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm493739.htm
FDA, Radiation-Emitting Products Interference between CT and Electronic Medical Devices. - ↑ Jump up to: 16.0 16.1 Hinson JS, Ehmann MR, Fine DM et al. Risk of acute kidney injury after intravenous contrast media administration. Ann Emerg Med 2017 Jan 19 PMID: https://www.ncbi.nlm.nih.gov/pubmed/28131489
Aycock RD et al. Acute kidney injury after computed tomography: A meta-analysis. Ann Emerg Med 2017 Aug 12 PMID: https://www.ncbi.nlm.nih.gov/pubmed/28811122 - ↑ Jump up to: 17.0 17.1 Hong JY, Han K, Jung JH, Kim JS. Association of exposure to diagnostic low-dose ionizing radiation with risk of cancer among youths in South Korea. JAMA Netw Open 2019 Sep 4; 2:e1910584. PMID: https://www.ncbi.nlm.nih.gov/pubmed/31483470 https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2749234
- ↑ Jump up to: 18.0 18.1 18.2 Ingram I FDA Clears 'Major Advancement' in CT Imaging. New Siemens; CT scanner is first allowed by agency with photon-counting detectors. MedPage Today September 30, 2021 https://www.medpagetoday.com/radiology/diagnosticradiology/94793
FDA News Release. September 30, 2021 FDA Clears First Major Imaging Device Advancement for Computed Tomography in Nearly a Decade. https://www.fda.gov/news-events/press-announcements/fda-clears-first-major-imaging-device-advancement-computed-tomography-nearly-decade