Andrew W. Bowman

Characterization of myocardial iron overload by dual-energy computed tomography compared to T2∗ MRI. A phantom study

Iron toxicity plays a key role in tissue damage in patients with iron overload, with induced heart failure being the main cause of death. T2*-weighted magnetic resonance imaging (MRI) has been established for evaluating myocardial iron overload with strong correlation with biopsy. The recently introduced dual-energy computed tomography (DECT) has the potential for evaluating iron overload without energy-dependent CT attenuation or tissue fat effects. This study investigates the performance of DECT for evaluating myocardial iron overload (based on images acquired at four different diagnostic imaging energies of 80, 100, 120, and 140 kVp) and compare the results to MRI T2* measurements based on DECT and MRI experiments on phantoms with calibrated iron concentrations. DECT showed high accuracy for evaluating iron overload compared to MRI T2* imaging, which might help in patient staging based on the degree of iron overload and independent of the implemented imaging energy.

The effects of the analysis technique on hepatic iron evaluation using T2∗ mapping with magnetic resonance imaging

Iron toxicity is the major factor for tissue damage and organ failure in patients with iron overload. T2* measurement with magnetic resonance imaging (MRI) has been established as an effective and non-invasive technique for evaluating iron content in the liver. However, different factors related to the adopted image processing criterion affect the resulting measurements. These factors include the exponential fitting model (single exponential, bi-exponential, or exponential + constant) and the size and location of the selected region of interest and whether it includes vasculature, susceptibility artifacts, or is close to the liver boundary. In this study, we investigate the effects of these various factors on T2* measurement using calibrated phantoms with different amounts of iron as well as on patients with different degrees of iron overload. The results show various degrees of similarities and differences between different processing techniques, which should be known by the operator for better selection of the image processing parameters and proper interpretation of the resulting measurements.

Evaluation of iron overload: dual-energy computed tomography versus magnetic resonance imaging

Figures 1 &2 show the phantoms, T2*-map, CT images, plots of R2* and HU versus iron-content, T2* curves fitting, and DECT iron-map. T2* ranged from 6 ms to 36 ms. There were strong correlations between iron-content and R2*, HU values and HU differences at different energy levels (r > 0.95 and P < 0.0001). There were moderate correlations between iron-content and HU ratios (except 80/140) with 0.42 < |r| < 0.76 and 0.02 < P < 0.2. The T2* relaxation curves of the 21 ms and 10 ms tubes were used to differentiate between normal, overloaded, and severely-overloaded iron (Figure 1d). The HU values of these two tubes showed perfect linear relationships with energy-level (E) over diagnostic levels 80-140 kVp: HU = -0.29E +56.3 and HU = -0.76E+151.8 for the 21 ms and 10 ms T2*-values. The resulting CT-map (Figure 2d) is used to identify three regions: normal, overloaded, and severely-overloaded iron. Conclusions DECT can be used for iron quantification with high accuracy similar to MRI, which might help in patient staging, independent of the energy level. New DECT scanners with low radiation-exposure, much shorter scan-time, and higher capability of measuring large iron-contents compared to MRI, may provide promising approach for evaluating myocardial iron overload.

Diagnosis and Management of Genetic Iron Overload Disorders

Iron overload disorders lead to excess iron deposition in the body, which can occur as a result of genetic or secondary causes. Genetic iron overload, referred to as hereditary hemochromatosis, may present as a common autosomal recessive mutation or as one of several uncommon mutations. Secondary iron overload may result from frequent blood transfusions, exogenous iron intake, or certain hematological diseases such as dyserythropoietic syndrome or chronic hemolytic anemia. Iron overload may be asymptomatic, or may present with significant diseases of the liver, heart, endocrine glands, joints, or other organs. If treated appropriately prior to end-organ damage, life expectancy has been shown to be similar compared to matched populations. Alongside clinical assessment, diagnostic studies involve blood tests, imaging, and in some cases liver biopsy. The mainstay of therapy is periodic phlebotomy, although oral chelation is an option for selected patients.

MRI evaluation of pancreatic ductal adenocarcinoma: diagnosis, mimics, and staging

The radiologist’s role in the evaluation of pancreatic ductal adenocarcinoma remains critical in the management of this deadly disease. Imaging plays a vital role in the diagnosis and staging of pancreatic cancer. Although CT is more commonly used for staging pancreatic cancer, MR is increasingly playing an important role in this regard. In our institution, all pancreatic malignancies undergo staging with MRI. In this pictoral essay, we illustrate the MR imaging features of pancreatic ductal adenocarcinoma and its mimics, and we also discuss pearls and pitfalls in MR staging of pancreatic carcinoma.

Dual-energy computed tomography versus magnetic resonance imaging for the assessment of iron overload

Iron toxicity is a key factor for tissue damage in iron-overloaded patients, with induced heart failure being the main cause of death. T2*-weighted magnetic resonance imaging (MRI) has been established as the method of choice for evaluating iron content with strong correlation with biopsy, where T2* <; 20 ms and T2* <; 10 ms at 1.5T indicate iron overload and severe iron overload, respectively. Recently introduced dual-energy computed tomography (DECT) has the potential for evaluating iron overload without energy-dependent CT attenuation or tissue fat effects. This study investigates the performance of DECT for iron mapping in scans of calibrated iron phantoms, and compare the results to MRI T2* imaging. The results show that DECT has high accuracy for evaluating iron overload, comparable to that of MRI T2* imaging, which might help in patient staging based on the severity of iron overload, independent of the implemented imaging energy.