Positron emission tomography (PET) is a nuclear imaging technology (also referred to as molecular imaging) that enables visualization of metabolic processes in the body. The basics of PET imaging is that the technique detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (also called radiopharmaceuticals, radionuclides or radiotracer). The tracer is injected into a vein on a biologically active molecule, usually a sugar that is used for cellular energy. PET systems have sensitive detector panels to capture gamma ray emissions from inside the body and use software to plot to triangulate the source of the emissions, creating 3-D computed tomography images of the tracer concentrations within the body.
After radiosurgery concurrent with nivolumab in 59-year-old patient with melanoma BM (patient 1; Supplemental Tables 3 and 5), F-18 FET PET at follow-up 12 weeks after treatment initiation (bottom row) shows significant decrease of metabolic activity (TBRmean, ?28%) compared with baseline (top row), although MRI changes were consistent with progression according to iRANO criteria. Reduction of metabolic activity was associated with stable clinical course over 10 mo. CE = contrast-enhanced. Image created by N. Galldiks et al., Research Center Juelich, Juelich, Germany.
Axial fused PET/CT image shows intense uptake (arrowhead) in the deep pelvis corresponding to the left lobe of the prostate in a 62-year-old with a history of prostate cancer treated with radiation therapy. The CT scan does not show the tumor. Image courtesy of the the Radiological Society of North America.
F-18 FES PET images of patients with ER+/PR+/HER2- invasive ductal carcinoma. Left panel: Progressive disease seen at the 8-week time-point in a patient on sequential therapy. Right panel: Stable disease through all 3 time-points, remaining on study therapy for 6.7 months until disease progression on combined vorinostat aromatase inhibitor therapy. Image created by Lanell M Peterson, Research Scientist, University of Washington Medical Oncology, Seattle WA.
Bright spots indicate that cancer cells have responded to a one-day challenge with estrogen in this positron emission tomography (PET) scan of a woman with breast cancer. In a small study, researchers at Washington University School of Medicine in St. Louis found that only women whose tumors responded to estrogen challenge benefited from hormone therapy. The findings could help doctors choose the treatments most likely to help their patients. Image courtesy of Farrokh Dehdashti
Differences in brain activity between connected and disconnected states of consciousness studied with positron emission tomography (PET) imaging. Activity of the thalamus, anterior (ACC) and posterior cingulate cortices (PCC), and bilateral angular gyri (AG) show the most consistent associa-tions with the state of consciousness (A = general anesthesia, B = sleep). The same brain struc-tures, which are deactivated when the state of consciousness changes to disconnected in general anesthesia or natural sleep (cool colors in the left columns), are reactivated when regaining a con-nected state upon emergence from anesthesia (warm colors in the right columns). Graphic courtesy of University of Turku
CXCR4-directed PET correlates with MRI-determined lymphoma lesions. Depicted are representative MR images (T1c- and FLAIR- sequences), and the corresponding CXCR4- directed PET images and fusion images (MRI-FLAIR and PET), of two patients with PCNSL and SCNSL, respectively. Images created by Department of Nuclear Medicine, School of Medicine, Technische Universität München, Munich, Germany.
Pre-treatment (A-C) and post-treatment (D-F) images after eight cycles of systemic FOLFIRINOX and consolidative chemoradiation. Baseline CA 19-9 was 145 U/ml. Pre-treatment whole body axial fused PET/MRI showed FDG avid lesion in body of pancreas (arrow, A) with SUVmax 7.1 and SUVgluc 8.0. Lesion was hypo-enhancing on axial contrast-enhanced T1-weighted (T1W) MR image (arrow, B) from focused abdominal PET/MRI and on CT (arrow, C). Pre-treatment CT tumor volume was 10.3 cm3. Post-treatment whole body axial fused PET/MRI showed complete metabolic response (arrow D) with SUVmax 1.9 and SUVgluc 1.9. Lesion was indistinct on axial contrast-enhanced T1W MRI (arrow, E) and CT (arrow, F), and there was upstream pancreatic parenchymal atrophy. Post-treatment CT tumor volume was 0.46 cm3. There was normalization of CA 19-9. Relative change in SUVmax (ΔSUVgluc) was -73%, and relative change in SUVgluc (ΔSUVgluc) was -76%. Based on change in tumor size, response was categorized as partial response per RECIST. Relative change in tumor volume (ΔTvol) was -96%. Pathology showed major pathologic response (College of American Pathologists score 1.) Images courtesy of American Roentgen Ray Society (ARRS), American Journal of Roentgenology (AJR)