Validation of T2* in-line analysis for tissue iron quantification at 1.5 T

Accurate and robust measurement of myocardial iron stores is essential for preventing cardiac disease and managing chelation treatment in patients with thalassemia, sickle cell disease, aplastic anemia, myelodysplasia, and other transfusion-dependant anemias [1–3]. T2* cardiovascular magnetic resonance (CMR) is effective and robust for tissue iron measurement in myocardial siderosis [4–8]; it is non-invasive and now considered the method of choice for myocardial and liver iron quantification [1, 9]. The underlying mechanism is that MR relaxation time of hydrogen nuclei falls with increasing amounts of storage iron. In recent studies, it has been demonstrated that tissue iron is the dominant determinant of myocardial relaxation, indicating that T2* CMR can measure the iron content accurately [10, 11].

The development of T2* CMR has made a great impact on patient management and survival, as no alternative method (e.g., serum ferritin, myocardial biopsy, liver biopsy or susceptometry) gives reliable information about cardiac iron loading. In the UK where it was first introduced clinically, 70 % reductions in cardiac mortality for thalassemia major (TM) have been documented [12]. However, barriers to using T2* CMR exist. Despite the successful T2* development, a recent international survey [13] indicates that the adoption of this technique is heterogeneous and that cases of high liver/myocardial iron concentration are still abundant, especially in developing countries where most of the patients are located. Apart from sequence and practical imaging issues, one particular challenge is that a post-processing step of T2* measurement using special software and training is required, resulting in some centers being unable to offer this lifesaving technique on a routine basis, or using locally developed software which has not been validated.

After a decade of development, the single breath-hold multi-echo gradient CMR T2* sequence is available from the major vendors, including Siemens, Philips and GE. One recent approach to further increasing T2* access is the vendors’ attempt to develop an in-line processing algorithm to generate T2* maps immediately after the scan. This obviates the need for third-party software, with users being able to simply draw a region-of-interest (ROI) on the map generated in the scanner console. This may streamline clinical workflow with the additional advantage of decreased user interaction. One such product is provided by Siemens Healthcare (Erlangen, Germany), named the Works in Progress T2* package (WIP). However, there are little validation data on this type of potentially useful product. In this study therefore, we aimed to directly compare WIP T2* with the established T2* technique at Royal Brompton Hospital (RBH) on a population of healthy volunteers and patients with iron overload conditions.