Medical imaging allows a view inside the human body, but different scans provide different information. Fusion imaging combines the data from two or more scans into a single, more complete image. This technique merges separate results to create a composite view, providing a more comprehensive understanding for medical assessment than any single scan could alone.
How Fused Images Are Created
The principle of fusion imaging is combining anatomical and functional scans. Anatomical imaging, like Computed Tomography (CT) or Magnetic Resonance Imaging (MRI), provides a detailed structural map of the body. These scans show the precise size, shape, and location of organs and tissues.
Functional scans reveal how parts of the body are working on a metabolic or cellular level. Technologies like Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) track processes like blood flow or metabolic activity. For example, a PET scan can show areas where cells consume glucose at a high rate, which can be a sign of disease.
The fusion is a digital process where specialized software performs co-registration to carefully align the separate images. To ensure accurate alignment, medical centers often use hybrid scanners that perform both scans during the same session. A common example is a PET/CT scanner, which captures both functional PET and anatomical CT data sequentially, allowing the software to overlay them with precision.
Applications in Medical Diagnosis
Fusion imaging has applications across several medical specialties, especially oncology, where it allows for a more precise diagnosis and staging of cancer. A CT scan’s anatomical detail combined with a PET scan’s metabolic information helps doctors pinpoint a tumor’s location and size. This also helps assess its activity level to distinguish cancerous tissue from benign growths and determine if cancer has metastasized, or spread.
This technology also helps manage cancer treatment. Oncologists compare fused images taken before and after therapy to assess a tumor’s response. For radiation therapy planning, PET/CT scans ensure radiation targets cancerous cells while minimizing damage to healthy tissue.
In neurology, fusion imaging helps diagnose brain disorders. For epilepsy, combining MRI and PET scans can identify the specific area where seizures originate by showing metabolic abnormalities, which is helpful for surgical planning. The technique is also applied in the early diagnosis of Alzheimer’s disease and other dementias, as it can reveal changes in brain metabolism before structural changes are visible on an MRI.
Cardiology uses fused images to assess heart muscle damage after a heart attack. A PET/MRI fusion can distinguish between permanently damaged tissue and tissue that is temporarily dysfunctional but still viable. This information guides decisions about treatments like angioplasty or bypass surgery to restore blood flow to recoverable areas of the heart.
The Patient Experience During a Fusion Scan
For a patient, undergoing a fusion scan like a PET/CT is a non-invasive, multi-step process. The procedure begins with the injection of a radiotracer, a substance like a radioactive sugar. After this injection, there is a waiting period of about an hour to allow the tracer to circulate and be absorbed by the body’s cells.
Once the tracer has circulated, the patient lies on a table that moves through the doughnut-shaped scanner. The machine performs both the CT and PET scans sequentially in the same session. The process is painless but requires the patient to remain still for clear, alignable images. The time inside the scanner is under an hour.