Introduction
fatty liver disease, cancers, cancer, cirrhosis, overload, 7.0–15.0 mg/g dw, hereditary haemochromatosis, thalassemia
CANCERS, CANCER, CIRRHOSIS, LIVER FIBROSIS, HEREDITARY HAEMOCHROMATOSIS, THALASSEMIA, IRON OVERLOAD, DISEASES
Elevation of liver iron concentration (LIC) occurs in patients with diseases such as hereditary haemochromatosis and fatty liver disease. LIC elevation can also result from having multiple blood transfusions, such as in patients with thalassemia. Increased LIC can lead to liver fibrosis, cirrhosis and cancer [Multi-echo gradient echo sequences in MRI can be used to measure R2*, from which LIC can be estimated, using calibration curves from previous studies [Assessing the agreement between 3 T-R2* LIC and 1.5 T-R2* LIC is important for several reasons. Firstly, given that 1.5 T-R2* LIC is used clinically, it is important that 3 T-R2* LIC is consistent with 1.5 T-R2* LIC so clinicians can confidently use 3 T-R2* LIC to diagnose iron overload.Secondly, R2* to LIC conversion methods that work both at 3 T and 1.5 T would allow more flexibility at sites that would be able to use different scanners for the same indication. This is particularly the case in the treatment of diseases which involve patients receiving multiple transfusions such as thalassemia and certain cancers, which result in increasing iron content in the body. Sometimes chelation is administered to reduce the iron level. It is important therefore to monitor the impacts of transfusion and chelation on iron content in the body. Measuring LIC on an annual basis using MRI is the recommended method for monitoring the impact of chelation therapy [The level of agreement required between 1.5 T LIC and 3 T LIC depends on the application. For categorising iron overload, the categories are quite broad (e.g. 3.2–7.0 mg/g dry weight (dw) is mild overload, 7.0–15.0 mg/g dw is moderate overload and > 15.0 mg/g dw is severe)[However, for monitoring treatment in the same patient across different scanners at both 1.5 T and 3 T, a closer agreement between 1.5 T and 3 T LIC may be required. For example, in a study of patients receiving the iron chelator Deferasirox, the change in least squares mean LIC was 1.95 mg/g dw over 52 weeks [In terms of the methods available for calculating 3 T-R2* LIC, there is one calibration curve available to convert R2* to LIC at 3 T [One way to test this hypothesis is to scan patients at both 3 T and 1.5 T and convert R2* to LIC at both field strengths and assess the agreement. The aim of this study was therefore to compare paired 1.5 T and 3 T R2* data that were converted to LIC, using a number of different LIC conversion methods. The agreement between the results at 1.5 T and 3 T was then assessed.