# CT (computed tomography)

Source: https://onco.cc/technologies/ct/  
OnCo record `ct` (Technology). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A CT scan is a fast 3D X-ray that shows the size and shape of tumours and whether they have spread.

## Summary

Computed tomography rotates an X-ray source and detector around the body and reconstructs the measured attenuation into cross-sectional images, with iodinated contrast highlighting vasculature. In use since 1971, it is the workhorse of staging and response assessment and the standard measurement tool for RECIST. It is fast, ubiquitous, offers sub-millimetre resolution and is excellent for lung, liver, bone and lymph nodes. Its limits are that it shows anatomy only, so it cannot distinguish scar from live tumour or give biological information, it has limited soft-tissue contrast, it performs poorly for brain, marrow and small peritoneal disease, and it delivers ionising radiation. Photon-counting CT improves resolution at lower dose, while PET/CT and MRI fill the gaps in biology and soft tissue. CT is the quick 3D X-ray that most cancer decisions are measured against.

## Fields

- Kind: Technology
- Status: standard-of-care
- Last checked: 2026-09-04
- Also known as: CT scan; computed tomography; CAT scan; CT scanning; contrast-enhanced CT
- Principle: A rotating X-ray source and detector measure attenuation, which is reconstructed into cross-sectional images. Iodinated contrast highlights vasculature.
- Since: 1971
- Strengths: Fast, ubiquitous; Sub-millimetre resolution; Standard for RECIST response
- Limitations: Anatomic only; cannot distinguish scar from live tumour; Radiation dose; Poor for brain, marrow, and small peritoneal disease

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/CT_scan
- Wikipedia: https://en.wikipedia.org/wiki/CT_scan

## Connected records

- technologies: [AFP, hCG and LDH in germ cell tumours (IGCCCG risk groups)](https://onco.cc/technologies/germ-cell-tumour-markers/), [AI in radiology](https://onco.cc/technologies/radiology-ai-screening/), [CEA surveillance after colorectal cancer surgery](https://onco.cc/technologies/cea-surveillance-colorectal/), [Cryoablation systems](https://onco.cc/technologies/cryoablation-systems/), [CT body composition and sarcopenia measurement](https://onco.cc/technologies/ct-body-composition-sarcopenia/), [CT-FM (whole-body CT foundation model)](https://onco.cc/technologies/ct-fm/), [CT, MRI and PET scanner manufacturing](https://onco.cc/technologies/medical-imaging-scanner-manufacturing/), [Dual-energy and spectral CT](https://onco.cc/technologies/dual-energy-spectral-ct/), [Imaging core labs and central review](https://onco.cc/technologies/imaging-core-labs/), [IMRT / IGRT (modern external beam)](https://onco.cc/technologies/imrt-igrt/), [In-room imaging for radiotherapy (cone-beam CT, ExacTrac, CT-on-rails, HyperSight)](https://onco.cc/technologies/in-room-imaging-systems/), [Intraoperative MRI and CT](https://onco.cc/technologies/intraoperative-mri-ct/), [Low-dose CT lung screening](https://onco.cc/technologies/low-dose-ct-screening/), [Merlin (Stanford abdominal CT vision-language model)](https://onco.cc/technologies/merlin-ct/), [Microwave and radiofrequency ablation systems](https://onco.cc/technologies/microwave-rf-ablation/), [NHS Targeted Lung Health Check (lung cancer screening programme)](https://onco.cc/technologies/nhs-targeted-lung-health-check/), [PET/CT](https://onco.cc/technologies/pet-ct/), [Photon-counting CT](https://onco.cc/technologies/photon-counting-ct/), [Proton therapy](https://onco.cc/technologies/proton-therapy/), [Quantitative imaging biomarkers (RECIST, PERCIST, SUV, ADC)](https://onco.cc/technologies/quantitative-imaging-biomarkers/), [Radiotherapy treatment planning and QA software](https://onco.cc/technologies/treatment-planning-systems/), [Robotic and navigational bronchoscopy](https://onco.cc/technologies/robotic-bronchoscopy/), [SPECT/CT](https://onco.cc/technologies/spect-ct/), [Sybil (MIT/MGH lung cancer risk from CT)](https://onco.cc/technologies/sybil/), [X-ray radiography and fluoroscopy](https://onco.cc/technologies/x-ray-radiography-fluoroscopy/)
- fronts: [Imaging](https://onco.cc/fronts/imaging/)
- companies: [Canon Medical Systems](https://onco.cc/companies/canon-medical/), [FUJIFILM Healthcare](https://onco.cc/companies/fujifilm/), [GE HealthCare](https://onco.cc/companies/ge-healthcare/), [Leo Cancer Care](https://onco.cc/companies/leo-cancer-care/), [Nucleo](https://onco.cc/companies/nucleo-research/), [Onc.AI](https://onco.cc/companies/onc-ai/), [P-Cure](https://onco.cc/companies/p-cure/), [Philips](https://onco.cc/companies/philips/), [Quantum Surgical](https://onco.cc/companies/quantum-surgical/), [Siemens Healthineers](https://onco.cc/companies/siemens-healthineers/), [United Imaging](https://onco.cc/companies/united-imaging/), [XACT Robotics](https://onco.cc/companies/xact-robotics/)
- terms: [Body composition (lean mass, fat mass, visceral fat)](https://onco.cc/terms/body-composition/), [Emergency presentation (route to diagnosis)](https://onco.cc/terms/emergency-presentation/), [Endobronchial ultrasound (EBUS-TBNA)](https://onco.cc/terms/ebus-tbna/), [High-risk stigmata and worrisome features of pancreatic cysts (IPMN and MCN surgical criteria)](https://onco.cc/terms/pancreatic-cyst-high-risk-stigmata/), [Lesion](https://onco.cc/terms/lesion/), [Liver-limited metastatic bowel cancer](https://onco.cc/terms/liver-limited-metastatic-colorectal/), [Lung-RADS and nodule reporting](https://onco.cc/terms/lung-rads/), [Mediastinal lymph node stations](https://onco.cc/terms/mediastinal-lymph-node-stations/), [Obstruction and T4 disease in bowel cancer](https://onco.cc/terms/obstructing-colorectal-cancer/), [Pancoast (superior sulcus) tumour](https://onco.cc/terms/pancoast-tumour/), [Pancreas protocol CT (pancreatic protocol CT, dual-phase thin-slice CT with structured reporting)](https://onco.cc/terms/pancreas-protocol-ct/), [Peritoneal cancer index](https://onco.cc/terms/peritoneal-carcinomatosis-index/), [Peritoneal metastases from bowel cancer](https://onco.cc/terms/colorectal-peritoneal-metastases/), [Pneumonitis](https://onco.cc/terms/pneumonitis/), [Pulmonary nodule](https://onco.cc/terms/pulmonary-nodule/), [RECIST](https://onco.cc/terms/recist/), [Resectability classes for pancreatic cancer (NCCN anatomical criteria and the 2017 international consensus)](https://onco.cc/terms/nccn-resectability-criteria-pancreatic/), [Resectability in lung cancer](https://onco.cc/terms/resectability-lung-cancer/), [Sarcopenia](https://onco.cc/terms/sarcopenia/), [Targeted lung health check](https://onco.cc/terms/targeted-lung-health-check/), [TNM 9: what changed in lung cancer staging](https://onco.cc/terms/tnm-9-lung-cancer/)
- cancers: [Appendiceal adenocarcinoma (mucinous and non-mucinous, including signet ring cell)](https://onco.cc/cancers/appendiceal-adenocarcinoma/), [Appendiceal cancer and pseudomyxoma peritonei](https://onco.cc/cancers/appendiceal/), [Bladder & urothelial cancer](https://onco.cc/cancers/urothelial/), [Borderline resectable pancreatic ductal adenocarcinoma](https://onco.cc/cancers/borderline-resectable-pdac/), [Breast cancer (all types)](https://onco.cc/cancers/breast-cancer/), [Cancer of unknown primary, favourable subsets](https://onco.cc/cancers/cup-favourable-subsets/), [Childhood lung and airway tumours (pleuropulmonary blastoma, tracheobronchial tumours)](https://onco.cc/cancers/pleuropulmonary-blastoma/), [Colorectal cancer](https://onco.cc/cancers/colorectal/), [Epithelioid haemangioendothelioma](https://onco.cc/cancers/epithelioid-haemangioendothelioma/), [Esthesioneuroblastoma (olfactory neuroblastoma)](https://onco.cc/cancers/esthesioneuroblastoma/), [Extrahepatic cholangiocarcinoma (perihilar and distal)](https://onco.cc/cancers/extrahepatic-cholangiocarcinoma/), [Extrapulmonary neuroendocrine carcinoma](https://onco.cc/cancers/extrapulmonary-nec/), [Gallbladder cancer](https://onco.cc/cancers/gallbladder/), [Goblet cell adenocarcinoma of the appendix](https://onco.cc/cancers/goblet-cell-adenocarcinoma/), [HER2-low and HER2-ultralow metastatic breast cancer](https://onco.cc/cancers/her2-low-metastatic-breast-cancer/), [Hereditary pheochromocytoma and paraganglioma (SDHx, VHL, RET, NF1, MAX and TMEM127)](https://onco.cc/cancers/hereditary-ppgl/), [High-risk gestational trophoblastic neoplasia (FIGO score 7 or more, including ultra-high-risk)](https://onco.cc/cancers/high-risk-gtn/), [Intraductal papillary mucinous neoplasm and other pancreatic cystic precursors](https://onco.cc/cancers/ipmn-cystic-precursors/), [Intrahepatic cholangiocarcinoma](https://onco.cc/cancers/intrahepatic-cholangiocarcinoma/), [KIT exon 11-mutant GIST](https://onco.cc/cancers/gist-kit-exon-11/), [Large cell neuroendocrine carcinoma of the lung](https://onco.cc/cancers/lung-lcnec/), [Localised adrenocortical carcinoma (ENSAT stage I to III, resectable)](https://onco.cc/cancers/localised-adrenocortical-carcinoma/), [Localised small bowel adenocarcinoma (stage I to III, resected)](https://onco.cc/cancers/localised-small-bowel-adenocarcinoma/), [Low-grade appendiceal mucinous neoplasm and pseudomyxoma peritonei](https://onco.cc/cancers/low-grade-appendiceal-mucinous-neoplasm/), [Lung cancer (all types)](https://onco.cc/cancers/lung-cancer/), [Lung neuroendocrine tumours (typical and atypical carcinoid)](https://onco.cc/cancers/lung-net/), [Mesothelioma](https://onco.cc/cancers/mesothelioma/), [Non-small-cell lung cancer](https://onco.cc/cancers/nsclc/), [Pancreatic acinar cell carcinoma](https://onco.cc/cancers/pancreatic-acinar-cell-carcinoma/), [Pancreatic ductal adenocarcinoma](https://onco.cc/cancers/pancreatic/), [Pancreatoblastoma](https://onco.cc/cancers/pancreatoblastoma/), [Placental-site trophoblastic tumour and epithelioid trophoblastic tumour](https://onco.cc/cancers/placental-site-trophoblastic-tumour/), [Resectable pancreatic ductal adenocarcinoma](https://onco.cc/cancers/resectable-pdac/), [Resectable stage I to III non-small-cell lung cancer](https://onco.cc/cancers/resectable-nsclc/), [Retroperitoneal sarcoma](https://onco.cc/cancers/retroperitoneal-sarcoma/), [Sinonasal undifferentiated carcinoma (SNUC) and SWI/SNF-deficient sinonasal carcinoma](https://onco.cc/cancers/sinonasal-undifferentiated-carcinoma/), [Small-cell lung cancer](https://onco.cc/cancers/sclc/), [Solid pseudopapillary neoplasm of the pancreas](https://onco.cc/cancers/solid-pseudopapillary-neoplasm/), [Thymoma (WHO types A, AB, B1, B2 and B3)](https://onco.cc/cancers/thymoma/), [Triple-negative breast cancer (TNBC)](https://onco.cc/cancers/tnbc/)
- trials: [NLST & NELSON (low-dose CT screening)](https://onco.cc/trials/nlst-nelson/)
- key papers: [Model to Determine Risk of Pancreatic Cancer in Patients With New-Onset Diabetes](https://onco.cc/key-papers/paper-sharma-endpac-model-new-onset-diabetes-gastroenterology-2018/), [NELSON: volume-based CT screening reduces lung cancer deaths with fewer false alarms](https://onco.cc/key-papers/paper-nelson-nejm-2020/), [NLST: yearly low-dose CT scans cut lung cancer deaths in heavy smokers](https://onco.cc/key-papers/paper-nlst-nejm-2011/), [Risk of Neoplastic Progression in Individuals at High Risk for Pancreatic Cancer Undergoing Long-term Surveillance](https://onco.cc/key-papers/paper-canto-caps-long-term-surveillance-gastroenterology-2018/)
- ideas: [A fast-track pathway from suspicion to treatment for pancreatic cancer in the NHS, measured from first scan to first treatment](https://onco.cc/ideas/idea-pdac-uk-fast-track-diagnosis-to-treatment-pathway/), [A ten-year cohort of incidental findings to calibrate follow-up guidelines](https://onco.cc/ideas/idea-prev-incidentaloma-natural-history-cohort/), [AI clears the normal lung screening scans so radiologists read only the suspicious ones](https://onco.cc/ideas/idea-prev-ldct-ai-negative-triage/), [AI malignancy scores to end repeat scans and biopsies for benign lung nodules](https://onco.cc/ideas/idea-prev-lung-nodule-ai-discharge/), [AI that spots pancreatic cancer on scans taken a year before diagnosis](https://onco.cc/ideas/idea-prev-pancreas-ai-prediagnostic-ct/), [AI-assisted central imaging reads to cut endpoint cost and variability](https://onco.cc/ideas/idea-tr1-ai-central-imaging-reads/), [Biopsy the one lesion that is growing while the others shrink](https://onco.cc/ideas/idea-bio1-outlier-lesion-biopsy/), [Dose chemotherapy by muscle mass, not body surface area](https://onco.cc/ideas/idea-bio2-lean-mass-dosing/), [Every lung screening visit includes stop-smoking medicine, opt-out](https://onco.cc/ideas/idea-prev-opt-out-cessation-in-lung-screening/), [Every routine CT scan checked by AI for early cancer signs, with a tracked follow-up pathway](https://onco.cc/ideas/idea-prev-opportunistic-ct-ai-registry/), [Find peritoneal spread while it is still small, and run complete cytoreduction through networks rather than adding heated chemotherapy](https://onco.cc/ideas/idea-crc-peritoneal-disease-found-early-and-treated-in-networks/), [Lung screening eligibility by risk score, not pack-years, including high-risk never-smokers](https://onco.cc/ideas/idea-prev-lung-screening-risk-model-eligibility/), [New diabetes after 50 plus weight loss triggers a pancreatic cancer check](https://onco.cc/ideas/idea-prev-new-onset-diabetes-pancreas-pathway/), [No clinical claims for imaging-derived biomarkers without phantom and standards compliance](https://onco.cc/ideas/idea-tr2-radiomics-ibsi-mandate/), [One certified open-source de-identification pipeline for scans and slides](https://onco.cc/ideas/idea-data-open-deidentification-pipeline/), [Read muscle loss automatically from scans patients already have](https://onco.cc/ideas/idea-bio2-ai-sarcopenia-from-ct/), [Run the ENDPAC score on every new diabetes diagnosis after 50 and scan the high scorers](https://onco.cc/ideas/idea-pdac-new-onset-diabetes-risk-score-pathway/), [Structured, coded radiology reports for cancer response instead of free text](https://onco.cc/ideas/idea-data-structured-radiology-response/), [Take lung screening scanners to supermarket car parks in the poorest areas](https://onco.cc/ideas/idea-prev-mobile-lung-screening-deprived-areas/), [Watch small kidney tumours rather than remove them, with a national registry](https://onco.cc/ideas/idea-prev-small-renal-mass-surveillance/)
- roadmaps: [Early detection roadmap: organ screening → blood tests for many cancers](https://onco.cc/roadmaps/early-detection-roadmap/)
- people: [Denise R. Aberle](https://onco.cc/people/denise-aberle/), [Harry J. de Koning](https://onco.cc/people/harry-de-koning/)
- institutions: [Erasmus MC Cancer Institute](https://onco.cc/institutions/erasmus-mc/), [International Association for the Study of Lung Cancer](https://onco.cc/institutions/iaslc/), [National Cancer Center Korea](https://onco.cc/institutions/ncc-korea/), [Shanghai Pulmonary Hospital](https://onco.cc/institutions/shanghai-pulmonary-hospital/)
- drugs: [Optellum Virtual Nodule Clinic](https://onco.cc/drugs/optellum-virtual-nodule-clinic/)

---
JSON: https://onco.cc/api/v1/entities/ct.json