Members of the Pediatric Molecular Imaging Program at Stanford (Peds-MIPS) are presenting insights on the use of new imaging technologies for children with cancer at the Annual Meeting of the Radiological Society of North America (RSNA) 2018.
Dr. Anne Muehe received an RSNA Travel Award for presenting her work on using the iron supplement ferumoxytol (Feraheme) "off-label" as a contrast agent for integrated 18F-FDG PET/MR imaging of children with cancer. Ferumoxytol nanoparticles can be detected with MRI, leading to strong positive (bright) contrast enhancement on T1-weighted MR images and negative (dark) contrast enhancement on T2-weighted images. Compared to standard small molecular gadolinium chelates, ferumoxytol nanoparticles have the advantage of providing long lasting vessel and tissue enhancement, which allows for whole body staging and local tumor staging in one session (abstract PD191-ED-WEB7). Primary administration of ferumoxytol nanoparticles (without obtaining unenhanced images first) did not negatively affect attenuation correction of 18F-FDG PET data (abstract SSE21-05). This is important for the acquisition of integrated 18F-FDG PET/MR scans as unenhanced scans can be omitted, leading to accelerated whole body MRI staging within 30 minutes or less.
In addition, medical student Ketan Yerneni showed that the radiotracer dose for integrated 18F-FDG PET/MR scans could be substantially reduced as well. Ketan used a novel machine learning algorithm (Subtle Medical Inc.) to augment 18F-FDG PET/MR data with 25% reduced radiotracer dose (0.75 MBq) compared to standard scans (3 Mbq/kg; abstract PD218-SD-MOB4; Fig. 1).
Dr. Ashok Theruvath reported the value of using ferumoxytol nanoparticles "off-label" as an MRI contrast agent for the diagnosis of joint infiltrations of bone tumors. Dr. Theruvath's pilot study in 13 patients with primary bone tumors (Ewing's sarcoma and osteosarcoma) suggested that ferumoxytol nanoparticles leak into a joint effusion if the tumor infiltrates the joint (abstract SSE21-04). Ferumoxytol nanoparticles did not leak into a joint effusion if the tumor did not infiltrate the joint. These results could provide a powerful new biomarker for the diagnosis of neoplastic joint infiltrations.
Dr. Hossein Najadnik used ferumoxytol nanoparticles to label stem cells and track the labeled cells with magnetic particle imaging (abstract SSK12-04). Magnetic particle imaging is a new ionizing radiation-free technology, which provides substantially improved sensitivity for the detection of nanoparticles compared to MRI.
Dr. Daldrup-Link presented educational lectures on the use of iron oxide nanoparticles as an alternative MRI contrast agent to gadolinium chelates, including applications for imaging cancer immunotherapies (abstracts SPSH54C and MSMI21C). Dr. Kristen Yeom investigated whether there was any evidence for deposition of ferumoxytol nanoparticles in the brain (abstract RC613-14). The team found that ferumoxytol nanoparticles do not accumulate in the brain of pigs (with histopathological correlation) or patients. While ferumoxytol can induce serious allergic reactions, the above studies did not encounter serious adverse events. Collectively, the team found many advantages of iron oxide nanoparticles for clinical MRI and translational magnetic particle imaging applications.
Fig. 1) 18F-FDG PET scan of a patient with malignant lymphoma: (A) PET scan at 60 minutes after intravenous injection of 18F-FDG at standard dose (3 MBq/kg), (B) Reconstructed PET scan at 25% of the original 18F-FDG dose (0.75 MBq), AI augmented low dose scan provides equal images quality compared to standard dose scan.