Purpose

T1 hyperintense dentate nuclei (HDN) and globus pallidi (HGP) has been recently established as markers ofGadolinium deposition in the brain. This has triggered many studies and a safety alert. We aimed to re-validatethe safety of a macrocyclic Gadolinium contrast agent in pediatric patients and present an update in view ofcurrent literature.

Material & methods

Retrospective selection of pediatric patients who received at least 3 intravenous injections of GadoterateMeglumine for MRI studies with at least 12 months of retention time. Age matched controls were used. Contouredregion of interest (ROI) signal intensity ratios for dentate to pons (DN/P) and globus pallidi to thalami (GP/T)were measured. The difference of ratios from initial to last MRI examination and between case and controls were tested using paired t-test.

Results

21 out of 49 cases qualified the inclusion & exclusion criteria. The average cumulative contrast injectionsreceived by cases was about 6.8. Most of the cases received at least 4 injections and 19 was the greatestnumber of injections received by one case. The average chronologic age of the cases was about 5 years. Nostatistical difference of signal intensity ratios from initial to last MRI study (P=0.57 & P=0.40) as well as comparedto the controls (P=39 & P=21).

Conclusions

Multiple contrast enhanced MRI studies can be safely administered macrocyclic Gadolinium agents with norisk of Gadolinium deposition in the brain. Currently, the consensus recommendation is of caution and preventionwhile favoring macrocyclic agents specifically for pediatric patients. No clear evidence for associated clinicalsequela related to Gadolinium deposition.

Our case demonstrates the classic imaging features of IgG4-related kidney disease, autoimmune pancreatitis, and sclerosing cholangitis through endoscopic retrograde cholangio-pancreatography (ERCP), ultrasound, CT, and MRI. Immunoglobulin G4 (IgG4) disease is gaining increasing recognition in the medical community as a result of its multi-system involvement. The pancreas remains the most common organ involved in autoimmune pancreatitis (AIP) although, pancreatic involvement is not necessary in order to have extrapancreatic manifestations. Due to its tumefactive nature, accurate diagnosis of IgG4 multi-organ related disease is vital in ensuring appropriate treatment and reduced morbidity associated with unnecessary investigation and intervention.

Monte Carlo simulation modeling is one of the newest approaches to helping biomedical imaging professionals measure, model, and analyze how noise and instrument dead-time works and negatively affects the great capability of Positron Emission Tomography with a Discovery Simulation Tomography camera. Dr. Bastein Guerin and Dr. Georges El Fakhri used and modified Simulation System for Emission Tomography (SimSET) software and Geant Analysis for Tomography Emission (GATE) simulation software to create a  NEMA image quality phantom The NEMA image quality phantom helped replicate how noise and instrument dead time is created and functions during Positron Emission Tomography scans in the 2D and 3D operation modes. Using the SimSET and Geant Analysis for Tomography Emission software, Dr. Guerin and Dr. Fakhri were able to generate and validate data results that illustrated how modeling dead-time can help account for other non-uniform dead-time behaviour in multiple structures of blocks that are not geometrically cylindrical or symmetrical.By applying statistical weights using a variance reduction technique in the SimSET and Geant Analysis for Tomography Emission simulation software, single coincidence circuitry can also process all detected coincidences with the object and scanner. Their approach using Monte Carlo simulation modeling can help create more capable PET scanners can better reduce noise and instrument dead time in the future.