Right adrenal vein identification using unenhanced magnetic resonance imaging

Abstract

Purpose: Unenhanced magnetic resonance imaging (MRI) is known to be useful in characterizing adrenal adenomas through the implementation of in-phase (IPI) and opposed-phase imaging (OPI) based on chemical shift artifacts. However, whether unenhanced MRI can contribute to the identification of right adrenal vein (RAV) remains unclear. The aim of this study was to evaluate the feasibility of unenhanced MRI for the identification of RAV.

Material and methods: This retrospective study reviewed 30 patients (16 men; median age 60 years; range 34-76 years) who underwent MRI and subsequent adrenal venous sampling (AVS). Chemical shift MRI was acquired using echo times of 2.3 ms (OPI) and 4.6 ms (IPI) with a slice thickness of 3 mm and a gap of 1 mm. T2-weighted imaging (T2WI) was also performed. Identification of RAVs was performed by 2 independent radiologists. Inter-observer agreement on a 3-point rating scale was evaluated using κ statistics. The identification rate of RAVs was compared between OPI, IPI, and T2WI using McNemar's test.

Results: Good inter-observer agreement was found for the OPI (κ = 0.744), whereas fair agreement was obtained for both other sequences (IPI: κ = 0.375; T2WI: 0.348). For both raters, the identification rate of RAVs was higher with OPI (36/60; 60.0%) than with other sequences (IPI: 16/60, 26.7%; T2WI: 9/60, 15.0%; p < 0.05, each).

Conclusions: OPI may play a screening role in the identification of RAVs preceding AVS, which could reduce the required radiation exposure and doses of contrast agent.

Keywords: adrenal glands; blood specimen collection; magnetic resonance imaging; veins.

Figure 1

Flow chart of the inclusion and exclusion criteria

Figure 2

Chemical shift magnetic resonance (MR) imaging with in-phase (IPI; A and D) and opposed-phase imaging (OPI; B and E), and fat-suppressed T2-weighted imaging (T2WI; C) on 3.0-T MR imaging of a 74-year-old female with left aldosterone-producing adenoma (APA). The right adrenal vein (RAV) is clearly identifiable on OPI (A; rated as 3 by both observers; arrow) but is not visualized on IPI or fat-suppressed T2WI (rated as 1 by both observers). The left adrenal adenoma appears slightly hyperintense on IPI (D; arrowhead) and hypointense on OPI (E; arrowhead). Fluoroscopic imaging shows the RAV draining into the inferior vena cava (IVC; F)

Figure 3

Chemical shift magnetic resonance (MR) imaging with in-phase (IPI; A and D), opposed-phase imaging (OPI; B and E), and fat-suppressed T2-weighted imaging (T2WI; C) on 3.0-T MR imaging of a 56-year-old female with left aldosterone-producing adenoma (APA). The right adrenal vein (RAV) is clearly identifiable on OPI (A; rated as 3 by both observers; arrow). The RAV is scored as 2 on IPI by both observers (B) but is not visualized on fat-suppressed T2WI (C; rated as 1 by both observers). Caudal slices on IPI (D) and OPI (E) confirm the RAV (arrow in B). Fluoroscopic imaging depicts the RAV draining into the IVC (F)