Differentiation Of Adrenal Adenoma From Adrenal Metastasis With Intravoxel Incoherent Motion Model

Abstract

Background:<br /> Intravoxel incoherent motion is a diffusion weighted imaging method which can characterize the relation between signal intensity and b value. Regarding to this bi-exponential model, IVIM would separate the diffusion of water molecules from micro capillary perfusion of tissues. This technique may estimate the perfusion of tissues without intravenous contrast application.<br /> Objectives:<br /> To investigate the value of IntraVoxel Incoherent Motion (IVIM) diffusion perfusion model for differentiation between adrenal adenomas and adrenal metastasis.<br /> Materials and Methods:<br /> We retrospectively evaluated thirty five adrenal lesions. According to conventional MRI findings, 25 lesions were incidentally detected adenomas and 10 lesions were adrenal metastasis of previously known primary oncologic malignancies. Mean age of all subjects was 61 years (range: 43-81). All patients were examined by 1.5T MRI (Siemens, Magneton Symphony, Erlangen, Germany) with the use of four-channel phased array body coil. In addition to routine pre- and post-contrast sequences, IVIM (16 dif ferent b factors of 0, 50, 100, 150, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300 s/mm2) and conventional DWI (3 different b factors of 50, 400, 800 s/mm2) were obtained using a free breath single-shot echo planar spin echo (EPI) sequence. The mean D (true diffusion coefficient), D* (pseudo-diffusion coefficient associated with blood flow) and f (perfusion fraction) values also calculated from IVIM. ADC, D, D* and f values were compared between adenoma and metastasis groups by Mann-Whitney U test.<br /> Results:<br /> The f and D values were significantily higher in metastasis group (p<0,05). ADC and D* values of metastatic lesions were significantly lower than those of adenomas (p<0,05).<br /> Conclusion:<br /> IVIM parameters such as f, ADC and D* values can provide significant diagnostic information regarding differentiation of adrenal adenomas and adrenal metastasis, based on different perfusion characteristics.