Qualitative Heterogeneous Signal Drop on Chemical Shift (CS) MR Imaging: Correlative Quantitative Analysis between CS Signal Intensity Index and Contrast Washout Parameters Using T1-Weighted Sequences.

Arnaldo Stanzione,Raffaele Liuzzi,Valeria Romeo,Francesco Verde,Simone Maurea,Pier Paolo Mainenti,Michele Klain,Elia Guadagno,Roberta Galatola,Marialaura Del Basso De Caro,Giovanni Aprea

doi:10.3390/tomography7040079

Abstract

The aim of this study was to calculate MRI quantitative parameters extracted from chemical-shift (CS) and dynamic contrast-enhanced (DCE) T1-weighted (T1-WS) images of adrenal lesions (AL) with qualitative heterogeneous signal drop on CS T1-WS and compare them to those of AL with homogeneous or no signal drop on CS T1-WS. On 3 T MRI, 65 patients with a total of 72 AL were studied. CS images were qualitatively assessed for grouping AL as showing homogeneous (Group 1, n = 19), heterogeneous (Group 2, n = 23), and no (Group 3, n = 30) signal drop. Histopathology or follow-up data served as reference standard to classify AL. ROIs were drawn both on CS and DCE images to obtain adrenal CS signal intensity index (ASII), absolute (AWO), and relative washout (RWO) values. Quantitative parameters (QP) were compared with ANOVA analysis and post hoc Dunn’s test. The performance of QP to classify AL was assessed with receiver operating characteristic analysis. CS ASII values were significantly different among the three groups (p < 0.001) with median values of 71%, 53%, and 3%, respectively. AWO/RWO values were similar in Groups 1 (adenomas) and 2 (benign AL) but significantly (p < 0.001) lower in Group 3 (20 benign AL and 10 malignant AL). With cut-offs, respectively, of 60% (Group 1 vs. 2), 20% (Group 2 vs. 3), and 37% (Group 1 vs. 3), CS ASII showed areas under the curve of 0.85, 0.96, and 0.93 for the classification of AL, overall higher than AWO/RWO. In conclusion, AL with qualitative heterogeneous signal drop at CS represent benign AL with QP by DCE sequence similar to those of AL with homogeneous signal drop at CS, but different to those of AL with no signal drop at CS; ASII seems to be the only quantitative parameter able to differentiate AL among the three different groups.

Highlights

Licensee MDPI, Basel, Switzerland.In adrenal imaging, T1-weighted chemical shift (CS) sequence using magnetic resonance imaging (MRI) has shown to be effective to characterize adrenal lesions (AL) and, to identify adrenal adenomas
40 lesions were classified as adenomas as they proved stable in terms of both size and imaging characteristics at imaging follow-up
The results of the present study suggest that AL with heterogeneous signal drop on CS sequence mostly represent benign AL, such as adenomas, as supported by the values of wash-out quantitative parameters extracted from dynamic contrast-enhanced (DCE) sequence as well as by clinical-imaging follow-up data or pathology used as standard of reference

Summary

Introduction

Licensee MDPI, Basel, Switzerland.In adrenal imaging, T1-weighted chemical shift (CS) sequence using magnetic resonance imaging (MRI) has shown to be effective to characterize adrenal lesions (AL) and, to identify adrenal adenomas. Its diagnostic imaging ability depends on the presence of a large amount of intracytoplasmic lipids in adrenal adenomas cells which reflects in homogeneous signal drop on CS out-of-phase images. As a rule, these adenomas are defined as “lipid-rich” [1,2,3]. A substantial amount of cytoplasmatic lipids, no signal drop on CS out-of-phase images occurs, and usually these lesions are defined as non-adenomas [1,2,3]. Malignant adrenal tumors, such as primary carcinoma or metastases by renal cell (RCC) and hepatocellular (HCC) carcinomas, may contain small amounts of intracytoplasmic lipids, resulting in heterogeneous signal drop on CS sequence [4]

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