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You have accessJournal of UrologyStone Disease: Evaluation & Medical Management1 Apr 2011

2227 IMAGING NEPHROLITHIASIS: AN PHANTOM MODEL COMPARING DIGITAL TOMOSYNTHESIS TO NON-CONTRAST CT

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    INTRODUCTION AND OBJECTIVES

    Non-contrast computed tomography (NCCT) is the gold standard in imaging of nephrolithiasis. It provides the most accurate dimension measurements and is able to visualize stones that may be obscured by artifact in other imaging modalities. However, its high sensitivity and specificity comes at a cost of a higher radiation dose. Digital tomosynthesis has been developed to improve upon traditional KUB with tomograms while minimizing radiation exposure. We compared digital tomosynthesis to NCCT for accuracy in detecting and measuring stone size in a phantom stone model.

    METHODS

    A 6.5cm x 7cm cylindrical gel phantom model was constructed of 200 bloom pork hide (Gelatin Innovations, Inc) customized with graphite (4239 vein, ∼17 μm, Superior Graphite) evenly distributed in the gel. The graphite scatterers simulate tissue density. A Begostone phantom was cast in a conical shape, measuring 7.5mm long and 5.7mm in diameter, and placed into the gel phantom. A radiology attending was blinded to the true physical size of the phantom stone, and measured phantom size by NCCT and digital tomosynthesis. CT reconstructions were performed at conventional 5mm slice thickness and finer 3mm slices. The phantom was imaged from AP and lateral projections by digital tomosynthesis.

    RESULTS

    CT settings were 120kVp and 100mA and performed on a 64-slice GE Healthcare VCT scanner. By conventional CT, the phantom was 7.5mm long and 6mm in diameter. With finer cuts at 3mm, the phantom measured 7.4mm and 6.3mm in diameter by CT (Figure 1). The phantom was easily seen by digital tomosynthesis. From a lateral view, the phantom was 7.6mm long and 6.7mm in diameter (Figure 2). From an AP view, the phantom was 7.5mm long and 5mm in diameter.

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    CONCLUSIONS

    In this in vitro model, digital tomosynthesis provides excellent image quality and stones can be easily identified. It closely approximates CT for measuring stone dimension, while minimizing radiation exposure. More in vivo experimentation is needed to determine its most optimal clinical utilization.

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