Gradient-echo magnetic resonance imaging study of pancreatic iron overload in young Egyptian beta-thalassemia major patients and effect of splenectomy

Abstract

Background: Thalassemic patients suffer from diabetes mellitus secondary to hemosiderosis.

Aims: The study aimed to evaluate pancreatic iron overload by T2*-weighted Gradient-echo magnetic resonance imaging (MRI) in young beta-thalassemia major patients and to correlate it with glucose disturbances, hepatic hemosiderosis, serum ferritin and splenectomy.

Methods: Forty thalassemic patients (20 non diabetic, 10 diabetic, and 10 with impaired glucose tolerance) were recruited from Pediatric Hematology Clinic, in addition to 20 healthy controls. All patients underwent clinical assessment and laboratory investigations included complete blood count, liver function tests, serum ferritin and oral glucose tolerance test (OGTT). A T2*-weighted gradient-echo sequence MRI was performed with 1.5 T scanner and signal intensity ratio (SIR) of the liver and the pancreas to noise were calculated.

Results: Significant reduction in signal intensity ratio (SIR) of the liver and the pancreas was shown in thalassemic patients compared to controls (P < 0.0001), Thalassemic patients with abnormal glucose tolerance; including diabetics and thalassemics with impaired glucose tolerance; displayed a higher degree of pancreatic and hepatic siderosis compared to thalassemics with normal glucose tolerance or controls (P < 0.001, P < 0.0001). Splenectomized thalassemic patients had significantly lower SIR of pancreas compared to non splenectomized patients (P < 0.05). A strong correlation was present between hepatic and pancreatic siderosis in studied patients (P < 0.001).

Conclusions: pancreatic siderosis can be detected by T2* gradient-echo MRI since childhood in thalassemic patients, and is more evident in patients with abnormal glucose tolerance. After splenectomy, iron deposition may be accelerated in the pancreas. Follow up of thalassemic patients using pancreatic MRI together with intensive chelation therapy may help to prevent the development of overt diabetes.

Figure 1

T2*-weighted GRE image of (A) normal subject and (B) β-thalassemia major patient with adequate chelation: (A) T2*-weighted GRE image (TR/TE/FA 120/15/20) of 18 yr-old normal male subject with normal signal intensity in the liver and the pancreas. (B) T2*-weighted GRE image (TR/TE/FA 120/15/20) of 13 yr-old male with β-thalassemia major with adequate chelation showing normal signal intensity in the liver and the pancreas (TR, repetition time; TE, echo time; FA, flip angle).

Figure 2

T2*-weighted GRE image of (A) splenectomized and (B) non splenectomized diabetic β-thalassemia major patients: (A) T2*-weighted GRE image (TR/TE/FA 120/15/20) of 12 yr-old female splenectomized β-thalassemia major with newly diagnosed diabetes showing low-signal intensity in the liver and the pancreas suggesting severe iron overload. (B) T2*-weighted GRE image (TR/TE/FA 120/15/20) of 16 yr-old female non splenectomized diabetic β-thalassemia major patient showing low-signal intensity in the liver and the spleen and normal signal intensity in the pancreas (TR, repetition time; TE, echo time; FA, flip angle).

Figure 3

Box and Whisker plot of signal intensity ratio of the pancreas (A), and the liver (B) of controls, thalassemic patients with normal and abnormal glucose tolerance. The lines in the box represent the median, the boxes are the 25-75^th percentile range, and the whiskers are the 10-90^th percentile range.