MRI evaluation of tissue iron burden in patients with beta-thalassaemia major

Abstract

beta-Thalassaemia major is a hereditary haemolytic anaemia that is treated with multiple blood transfusions. A major complication of this treatment is iron overload, which leads to cell death and organ dysfunction. Chelation therapy, used for iron elimination, requires effective monitoring of the body burden of iron, for which serum ferritin levels and liver iron content measured in liver biopsies are used as markers, but are not reliable. MRI based on iron-induced T2 relaxation enhancement can be used for the evaluation of tissue siderosis. Various MR protocols using signal intensity ratio and mainstream relaxometry methods have been used, sometimes with discrepant results. Relaxometry methods using multiple echoes achieve better sampling of the time domain in which relaxation mechanisms take place and lead to more precise results. In several studies the MRI parameters of liver siderosis have failed to correlate with those of other affected organs, underlining the necessity for MRI iron evaluation in individual organs. Most studies have included children in the evaluated population, but MRI data on very young children are lacking. Wider application of relaxometry methods is indicated, with the establishment of universally accepted MRI protocols, and further studies, including young children, are needed.

Fig. 1

A 15-year-old male with β-thalassaemia major. Axial scan with a multiecho gradient-echo sequence (TR/TE 150/1.07, 2.14, 3.21, 4.28, 5.35, 6.42, 7.49, 8.56, 9.63, 10.7, 11.77, 12.84, 13.91, 14.98, 16.05, 17.12, 18.19, 19.26, 20.33, 21.4 ms; flip angle 35°). a Second echo shows pixel annulation (arrows) due to out-of-phase phenomena, at the interfaces of abdominal organs and muscles with fat. b Fourth echo: no pixel annulation is observed because water and fat protons are in phase (courtesy of Dr. M. Douskou)

Fig. 2

A 17-year-old male with β-thalassaemia major. Axial scan, fourth echo of a multiecho spin-echo sequence (TR/TE: 2000/20, 40, 60, 80, 100, 120, 140, 160 ms), shows low-signal intensity in the liver, bone marrow of the spinal body and the pancreas suggesting iron overload

Fig. 3

A 16-year-old male with β-thalassaemia major. a T2 map of the short axis of the heart shows low values of the left ventricle (arrow) and the septum (arrowhead). b R2* (=1/T2*) map of the short axis of the heart shows high signal of the septum (asterisk). Note the reduction of motion artefacts and better delineation of the heart boundary in the R2* image (courtesy of Dr. M. Douskou)

Fig. 4

The pituitary. a A 12-year-old male with β-thalassaemia major. Midsagittal T1-weighted (TR/TE 500/20 ms) scan shows low-signal intensity of the anterior pituitary lobe (arrow) and the bone marrow (asterisks) suggesting iron overload. The pituitary gland is small measuring 3.5 mm (normal for age 5.3±0.8 mm) [112]. This patient developed hypogonadotropic hypogonadism. b An 11-year-old male with β-thalassaemia major. Mid-sagittal T1-weighted (TR/TE 500/20 ms) scan shows normal signal intensity of the anterior pituitary lobe (arrow) along with normal pituitary gland height (6 mm). The bone marrow (asterisk) shows low-signal intensity suggesting iron overload

Fig. 5

Siderosis of the spleen, pancreas and adrenals. a A 14-year-old male with β-thalassaemia major. Axial scan, fourth echo of a multiecho sequence (TR/TE 2,000/20, 40, 60, 80, 100, 120, 140, 160 ms) shows low-signal intensity of the liver, pancreas (arrow) and spleen suggesting increased iron deposition. b A 27-year-old-male with β-thalassaemia major and diabetes. Axial T2-W (TR/TE 1,800/80 ms) scan shows low-signal intensity of the liver and adrenals suggesting siderosis. High signal intensity of the pancreas (arrow) suggests tissue damage and fatty degeneration