Article Summary
A two-center study found that chromosome damage detected after PET/CT scans is driven almost entirely by the CT component rather than the FDG radiotracer, supporting the use of reduced-dose CT protocols when clinically appropriate.
- CT dose, not FDG radiotracer, is the primary driver of chromosomal aberrations in PET/CT imaging
- Reduced-dose CT protocols (3.4 mSv) caused no significant chromosome damage, while standard-dose CT (9.2 mSv) increased aberrations significantly
- Study enrolled 157 patients across two Japanese university hospitals using different CT dose protocols
- FDG administration did not significantly increase chromosomal aberrations at either center
- Previous chemotherapy and increasing age were independently associated with higher chromosome aberration counts
A prospective two-center study found that the chromosome damage detected after PET/CT is driven almost entirely by the CT scan rather than the FDG radiotracer, supporting wider use of reduced-dose CT protocols when clinically appropriate.
The findings, published in European Radiology, suggest that standard-dose CT should be reserved for clearly justified diagnostic indications, particularly in screening examinations.
While the European Association of Nuclear Medicine (EANM) provides recommendations for FDG activity, no comparable consensus exists for CT dose in PET/CT, and CT exposures in routine practice often match or exceed those of diagnostic CT.
Sampling before and after each exposure
The prospective observational study enrolled patients undergoing clinically indicated FDG-PET/CT at two Japanese university hospitals between April 2019 and January 2022. Hiroshima University Hospital routinely uses a reduced-dose CT protocol, while Nagasaki University Hospital uses a standard-dose protocol.
Blood samples were collected immediately before FDG administration, 50 to 60 minutes after injection, and 30 to 60 minutes after CT acquisition, allowing the researchers to separate the biological effects of the radiotracer from those of the CT scan.
Unstable chromosomal aberrations, specifically dicentric and ring chromosomes, were measured in peripheral blood lymphocytes using peptide nucleic acid fluorescence in situ hybridization.
The study enrolled 101 patients at the reduced-dose center and 56 at the standard-dose center. Median dose-length product was 260 mGy·cm versus 706 mGy·cm, corresponding to median CT effective doses of 3.4 mSv and 9.2 mSv, respectively.
CT, not FDG, was linked to chromosome damage
FDG administration did not significantly increase chromosomal aberrations at either center. After CT acquisition, aberrations increased significantly only in patients scanned using the standard-dose protocol (p = 0.016).
In a multivariable mixed-effects model including 151 patients, CT effective dose was independently associated with chromosomal aberration frequency (p = 0.008), whereas FDG effective dose was not (p = 0.38).
Previous chemotherapy approximately doubled chromosomal aberration frequency (rate ratio 2.04, p < 0.001), while increasing age was also independently associated with higher aberration counts.
Small biological effect, clear clinical message
The authors emphasized that the observed increase was modest, with approximately one to two additional chromosomal aberrations per 1,000 cells, and within the expected range of biological variability, suggesting limited relevance at the population level.
The results nevertheless provide biological support for using reduced-dose CT protocols when a full diagnostic-quality CT examination is not required.
The full article can be found here.
