GlutamineGlutamate Metabolism Studied with Magnetic Resonance Spectroscopic Imaging for the Characterization of Adrenal Nodules and Masses

Abstract EN

Purpose.

To assess glutamine/glutamate (Glx) and lactate (Lac) metabolism using proton magnetic resonance spectroscopic imaging (1H-MRS) in order to differentiate between adrenal gland nodules and masses (adenomas, pheochromocytomas, carcinomas, and metastases).

Materials and Methods.

Institutional review board approval and informed consent were obtained.

A total of 130 patients (47 men) with 132 adrenal nodules/masses were prospectively assessed (54±14.8 years).

A multivoxel system was used with a two-dimensional point-resolved spectroscopy/chemical-shift imaging sequence.

Spectroscopic data were interpreted by visual inspection and peak amplitudes of lipids (Lip), choline (Cho), creatine (Cr), Lac, and Glx.

Lac/Cr and Glx/Cr were calculated.

Glx/Cr was assessed in relation to lesion size.

Results.

Statistically significant differences were observed in Glx/Cr results between adenomas and pheochromocytomas (P<0.05), however, with a low positive predictive value (PPV).

Glx levels were directly proportional to lesion size in carcinomas.

A cutoff point of 1.44 was established for the differentiation between carcinomas larger versus smaller than 4 cm, with 75% sensitivity, 100% specificity, 100% PPV, and 80% accuracy.

Lac/Cr results showed no differences across lesions.

A cutoff point of −6.5 for Lac/Cr was established for carcinoma diagnosis.

Conclusion.

Glx levels are directly proportional to lesion size in carcinomas.

A cutoff point of −6.5 Lac/Cr differentiates carcinomas from noncarcinomas.