# SPECT/CT

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

## TL;DR

A gamma camera with a CT scanner bolted on, so a hot spot on a bone scan or a sentinel-node scan is pinned to the exact bone or lymph node, and the dose from a radioactive drug can be measured after treatment.

## Summary

SPECT/CT acquires a rotating gamma-camera study and a CT scan on one gantry. The CT corrects the SPECT for attenuation and places each focus of tracer anatomically, turning an ambiguous spot on a planar bone scan into a rib fracture or a metastasis and mapping a sentinel node to the correct basin before surgery. In oncology it is used for technetium bone scans in prostate and breast cancer, sentinel lymph node mapping in melanoma and breast cancer, radioiodine scans in thyroid cancer, MIBG in neuroblastoma, somatostatin-receptor scans where PET is not available and, increasingly, for quantitative imaging of lutetium-177 after radioligand therapy so the absorbed dose to tumour and kidneys can be calculated. Newer cameras replace sodium iodide crystals with cadmium zinc telluride detectors arranged in a ring (GE StarGuide, Siemens Symbia Pro.specta with digital detectors), which are faster and more quantitative.

SPECT is cheaper and far more widely available than PET, and the tracers are generator-produced without a cyclotron, but its resolution and sensitivity are lower and scans are slower.

## Fields

- Kind: Technology
- Status: standard-of-care
- Last checked: 2026-09-17
- Tags: machines-wave
- Principle: Rotating gamma cameras record single photons from technetium-99m, iodine-123 or lutetium-177 tracers; a co-registered CT provides attenuation correction and anatomical localisation for a quantitative three-dimensional map.
- Since: 1999
- Strengths: Widely available and cheaper than PET; Tracers from generators, no cyclotron needed; Dosimetry after lutetium-177 therapy
- Limitations: Lower resolution and sensitivity than PET; Slower acquisitions; Fewer targeted tracers than PET

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Single-photon_emission_computed_tomography
- Wikipedia: SPECT: https://en.wikipedia.org/wiki/Single-photon_emission_computed_tomography
- GE HealthCare: SPECT/CT systems: https://www.gehealthcare.com/products/molecular-imaging/spect-ct

## Connected records

- technologies: [CT (computed tomography)](https://onco.cc/technologies/ct/), [Gamma probes, handheld gamma cameras and dose calibrators](https://onco.cc/technologies/gamma-probes-dose-calibrators/), [PET/CT](https://onco.cc/technologies/pet-ct/), [Radioligand dosimetry](https://onco.cc/technologies/radioligand-dosimetry/), [Radioligand therapy (beta emitters)](https://onco.cc/technologies/radioligand-therapy/), [Sentinel lymph node biopsy](https://onco.cc/technologies/sentinel-node/), [SPECT & bone scan](https://onco.cc/technologies/spect/)
- cancers: [Breast cancer (all types)](https://onco.cc/cancers/breast-cancer/), [Melanoma](https://onco.cc/cancers/melanoma/), [Neuroblastoma (paediatric)](https://onco.cc/cancers/neuroblastoma/), [Neuroendocrine tumours](https://onco.cc/cancers/neuroendocrine/), [Prostate cancer](https://onco.cc/cancers/prostate/), [Thyroid cancer](https://onco.cc/cancers/thyroid/)
- fronts: [Imaging](https://onco.cc/fronts/imaging/), [Radiopharmaceuticals & Theranostics](https://onco.cc/fronts/radiopharma/)
- companies: [GE HealthCare](https://onco.cc/companies/ge-healthcare/), [Mediso](https://onco.cc/companies/mediso/), [Siemens Healthineers](https://onco.cc/companies/siemens-healthineers/)

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