Does a PET Scan Use a CT Scanner?
Yes, modern PET scanners are typically integrated with CT scanners in a combined PET/CT system, where both modalities are mounted together in a single gantry to provide co-registered anatomical and functional imaging. 1, 2
Technical Configuration of PET/CT Systems
PET/CT scanners combine a multidetector helical CT scanner (located proximally in the gantry) with a dedicated PET ring (located distally in the gantry), allowing automatic and exact fusion of both modalities. 1
The CT component serves dual purposes: it provides anatomical localization and is used for attenuation correction of PET images, replacing traditional transmission scanning with radioactive sources. 2, 3
These are physically integrated devices sharing a common patient bed, not separate machines—the patient moves through both scanners sequentially during a single examination session. 3
Clinical Adoption and Current Practice
By 2003, PET/CT scanners comprised more than 80% of total PET scanner sales, with over 450 units sold worldwide within 3 years of commercial availability. 1
The first prototype PET/CT scanner was developed in 1998, with commercial availability beginning in 2001 in the United States and Europe. 1
For oncology applications, dedicated PET or PET/CT systems should be used for response assessment—standalone PET scanners without CT integration are strongly discouraged in favor of integrated systems. 1
Important Distinction: PET Can Exist Without CT
While integrated PET/CT is now the standard, PET scanners can operate independently without CT, using radioactive transmission sources (such as Germanium-68) for attenuation correction. 1, 3
Some facilities use standalone PET scanners with separate CT scans performed on different machines, though this approach has limitations in image co-registration accuracy, particularly outside the brain. 3, 4
Alternative Hybrid Configuration: PET/MRI
PET can also be combined with MRI instead of CT (PET/MRI), where PET detectors are integrated directly into the MRI scanner for simultaneous acquisition. 5
PET/MRI offers advantages of superior soft tissue contrast and no radiation exposure from CT, though this technology is less widely adopted than PET/CT. 5
For patients with pacemakers, PET/MRI requires special MR-conditional devices, whereas standard PET/CT poses no contraindication related to the pacemaker itself. 6