Biexponential R2* relaxometry for estimation of liver iron concentration in children: A better fit for high liver iron states.

BACKGROUND: R2* relaxometry's capacity to calculate liver iron concentration (LIC) is limited in patients with severe overload. Hemosiderin increases in these patients, which exhibits a non-monoexponential decay that renders a failed R2* analysis. PURPOSE/HYPOTHESIS: To evaluate a biexponential R2* relaxometry model in children with different ranges of iron overload. STUDY TYPE: Retrospective. POPULATION: In all, 181 children with different conditions associated with iron overload. FIELD STRENGTH/SEQUENCE: 1.5T, T2 *-weighted gradient echo sequence. ASSESSMENT: Bi- and monoexponential R2* relaxometry were measured in the liver using two regions of interest (ROIs) using a nonproprietary software: one encompassing the whole liver parenchyma (ROI-1) and the other only the periphery (ROI-2). These were drawn by a single trained observer. The residuals for each fitting model were estimated. A ratio between the residuals of the mono- and biexponential models was calculated to identify the best fitting model. Patients with 1) residual ratio ≥1.5 and 2) R2*fast ≥R2*slow were considered as having a predominant biexponential behavior. STATISTICAL TESTS: Nonparametric tests, Bland-Altman plots, linear correlation, intraclass correlation coefficient. Patients were divided according to their LIC into stable (n = 23), mild (n = 58), moderate (n = 61), and severe (n = 39). RESULTS: The biexponential model was more suitable for patients with severe iron overload when compared with the other three LIC categories (P < 0.001) for both ROIs. For ROI-1, 37 subjects met criteria for a predominant biexponential behavior. The slow component (5.7%) had a lower fraction than the fast component (94.2%). For ROI-2, 22 subjects met criteria for a predominant biexponential behavior. The slow component (4.7%) had a lower fraction than the fast component (95.2%). The intraobserver variability between both ROIs was excellent. DATA CONCLUSION: The biexponential R2* relaxometry model is more suitable in children with severe iron overload. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:1191-1198.

Protocol optimization for cardiac and liver iron content assessment using MRI: What sequence should I use?

OBJECTIVE: To determine the optimal MRI protocol and sequences for liver and cardiac iron estimation in children. METHODS: We evaluated patients ≤18 years with cardiac and liver MRIs for iron content estimation. Liver T2 was determined by a third-party company. Cardiac and Liver T2* values were measured by an observer. Liver T2* values were calculated using the available liver parenchyma in the cardiac MRI. Linear correlations and Bland-Altman plots were run between liver T2 and T2*, cardiac T2* values; and liver T2* on dedicated cardiac and liver MRIs. RESULTS: 139 patients were included. Mean liver T2 and T2* values were 8.6 ±â€¯5.4 ms and 4.5 ±â€¯4.1 ms, respectively. A strong correlation between liver T2 and T2* values was observed (r = 0.96, p < 0.001) with a bias (+4.1 ms). Mean cardiac bright- and dark-blood T2* values were 26.5 ±â€¯12.9 ms and 27.2 ±â€¯11.9 ms, respectively. Cardiac T2* values showed a strong correlation (r = 0.81, p < 0.001) with a low bias (-1.0 ms). The mean liver T2* on liver and cardiac MRIs were 4.9 ±â€¯4.7 ms and 4.6 ±â€¯3.9 ms, respectively. A strong correlation between T2* values was observed (r = 0.96, p < 0.001) with a small bias (-0.2 ms). CONCLUSION: MRI protocols for iron concentration in the liver and the heart can be simplified to avoid redundant information and reduce scan time. In most patients, a single breath-hold GRE sequence can be used to evaluate the iron concentration in both the liver and heart.

Severe hemolytic transfusion reaction due to anti-D in a D+ patient with sickle cell disease.

A 5-year-old male with sickle cell disease presented with pain, dark urine, and fatigue 10 days after a red blood cell (RBC) transfusion. Laboratory evaluation demonstrated severe anemia, blood type O+, and anti-D in the serum. Anti-D in a D+ patient led to RH genotyping, which revealed homozygosity for RHD*DAU4 that encodes partial D antigen. Anti-D in this patient whose RBCs exclusively express partial D caused a delayed hemolytic transfusion reaction after exposure to D+ RBCs. The finding of anti-D in a D+patient should be investigated by molecular methods to help distinguish an alloantibody from an autoantibody.

Acquired aplastic anemia in children.

This article provides a practice-based and concise review of the etiology, diagnosis, and management of acquired aplastic anemia in children. Bone marrow transplantation, immunosuppressive therapy, and supportive care are discussed in detail. The aim is to provide the clinician with a better understanding of the disease and to offer guidelines for the management of children with this uncommon yet serious disorder.