Characterization of ureteral stents by dual-energy computed tomography: Clinical implications

Abstract

Dual-energy computed-tomography (DECT) has been suggested as the method of choice for imaging urinary calculi due to the modality's high sensitivity for detecting stones and its capability of accurately differentiating between uric-acid (UA) and non-UA (predominantly calcium) stones. The clinical significance of the latter feature relates to the differences in management of UA vs non-UA calculi. Like calculi, ureteral stents are assigned color by the dual-energy post-processing algorithm, which may lead to improved or worsened stone visualization based on the resulting stent/stone contrast. Herein we depict the case of a nephrolithiasis patient with bilateral stents, each with different color, clearly displaying the effect of stent color on stone visualization. Further, three-dimensional reconstruction of the DECT images illustrates advantages of this enhancement compared to conventional two-dimensional computed tomography. The resulting stent/stone contrast produces an unanticipated potential advantage of DECT in patients with urolithiasis and stents and may promote improved management decision-making.

Keywords: Dual-energy computed-tomography; Kidney stones; Nephrolithiasis; Ureteral stent.

Figure 1

Conventional and dual-energy computed tomography images of kidney stones and ureteral stents. Conventional computed tomography (top) and dual-energy computed-tomography (DECT, bottom) images showing the advantage of DECT for stone visualization and identification of composition. The solid and dashed arrows point to stones and stents, respectively. The different stent and stone colors in the left kidney enhanced stone visualization, while the visualization of the stone in the right kidney is compromised because it has the same color as the stent. The small cubes in the bottom show the view orientation in the 3D [Anterior (A); and Foot (F)].

Figure 2

Three-dimensional reconstruction of dual-energy computed tomography images of kidney stones and different types of ureteral stents. Different views of the stent/stone boundary from three-dimensional reconstruction of the dual-energy computed-tomography images. The left and right stents appear red and blue, respectively, while all stones appear blue due to their non-uric-acid composition. The different colors of the stent and stone in the left kidney allow for better stone visualization (arrows) than in the right kidney where both the stent and stone have the same color. [Anterior (A)-Posterior (P); and Left (L)]