Magnetic Resonance Imaging Assessment of Excess Iron in Thalassemia, Sickle Cell Disease and Other Iron Overload Diseases

Abstract

Patients with transfusion-dependent anemia develop cardiac and endocrine toxicity from iron overload. Classically, serum ferritin and liver biopsy have been used to monitor patient response to chelation therapy. Recently, magnetic resonance imaging (MRI) has proven effective in detecting and quantifying iron in the heart and liver. Tissue iron is paramagnetic and increases the MRI relaxation rates R2 and R2* in a quantifiable manner. This review outlines the principles and validation of non invasive iron estimation by MRI, as well as discussing some of the technical considerations necessary for accurate measurements. Specifically, the use of R2 or R2* methods, choice of echo times, appropriate model for data fitting, the use of a pixel-wise or region-based measurement, and the choice of field strength are discussed.

R2 and R2* are equally effective in evaluating chronic response to iron chelation

“…Thus prior studies using these endpoints can be compared to one another. Going forward, the choice of MRI assessment technique for clinical trials and for clinical management depends on many logistical considerations, including cost, the expected dynamic range of iron burden [2], and the availability of trained, experienced personnel for image quality control and analysis. In the present study, both liver R2 and R2* assessments were performed by dedicated core laboratories, but performance of these metrics in the community depends upon the integrity of the local analyses.…”

“…Two MRI relaxometry methods have come to dominate clinical trials and clinical practice [1]. Relaxometry is the quantitative assessment of MRI image darkening produced as protons excited by radiowaves relax toward their equilibrium magnetic state [2]. Magnetic relaxation follows exponential decay and is described by three characteristic time constants, T1, T2, and T2* or by their mathematical inverses, the relaxation rates R1, R2, and R2*.…”

Different forms of iron accumulation in the liver on MRI

“…T2 or T2* values are inversely related with iron concentration. However, R2 or R2* values (1000/T2 or T2*) are directly related to the iron concentration and increase linearly with iron concentration determined by liver biopsy (13). Calculation of R2* and T2* plays an important role in diagnosing the degree of iron overload for planning the treatment with iron chelating agents.…”

Çocukluk Çağı Kanserlerinde Tedaviye Bağlı Demir Yükü

“…Ancak çalışmaların çoğu hemoglobinopatili hastalarda yapılmış olup, MRG'nin KC'deki demir birikimini göstermesiyle ilgili veriler daha çok bu çalışmalardan elde edilmiştir 43,[72][73][74] . Wood'un çalışmasında orak hücre anemili hastalarda demir yükünü belirlemek amacıyla serolojik yöntemler ve MRG bulguları birlikte değerlendirilmiştir.…”