Objectives: Digital tomosynthesis is a new digital technique based on conventional Xray tomography. It acquires multiple low-dose projections during a single sweep of the X-ray tube, which are reassembled to provide high-resolution slices at different depths. Suggested uses include visualisation of pulmonary nodules, mammography, angiography, dental imaging and delineation of fractures. This study aims to evaluate its potential role as part of an intravenous urogram (IVU) by assessing the diagnostic quality in imaging the kidneys in clinical practice. Methods: 100 renal units from consecutive traditional IVU studies were retrospectively compared with 101 renal units imaged using digital tomosynthesis. These were scored for visualisation of the renal outline and collecting system, presence of a renal cyst or mass and overall diagnostic quality. Radiation doses were calculated. Results: 46.5% of traditional IVUs were found to be of diagnostic quality. The IVUs with digital tomosynthesis were of diagnostic quality in 95.5%. This represents a highly statistically significant difference (p,0.0001). There was also a statistically significant dose reduction, with a mean reduction of 56%, for the samples studied. Conclusion: Digital tomosynthesis offers a significant increase in the percentage of diagnostic quality tests for assessing renal pathology, compared with traditional IVU, and significantly reduces radiation. It also offers considerable advantages in ease and speed of imaging. For these reasons, in any situation where IVU is still being used to assess the kidneys, digital tomosynthesis is likely to be of considerable benefit in improving diagnostic quality.

ABSTRACT. Recent advances in technology have led to the realisation of digital tomosynthesis (DT) imaging in routine investigations such as intravenous pyelogram (IVP). The major advantage this technology has over other technologies is its ability to perform a retrospective reconstruction of an arbitrary number of coronal image planes from a single data set consisting of a series of low dose discrete projections acquired over a limited angular range using a stationary detector. It is well documented that because DT relies on an angular limited acquisition, the data set is incomplete. This, in combination with the image reconstruction algorithm, results in reconstructed images containing non-focused information from outside the immediate focal plane. This article describes and suggests the cause of two artefacts unique to DT that cannot be explained by blurring alone. We believe the two artefacts are caused by breathing during data acquisition together with a combination of other factors, including the anatomy of the renal system, the method of data acquisition and the reconstructive algorithm used. This could lead to the unaware reporting radiologist falsely diagnosing a duplex collecting system. To avoid these artefacts, we recommend DT IVP should only be used in patients who can adequately perform a breath-hold for the duration of the data acquisition. In addition, we suggest that the study should be performed with breath-held following expiration. Tomosynthesis relies on a series of two-dimensional (2D) radiographs acquired at varying angles to the object of interest. A coronal image plane may then be reconstructed from the 2D data by spatially translating each 2D image and superimposing each radiograph to an arbitrary reference. The magnitude of the translation of the 2D radiograph determines the height of the reconstructed coronal image plane. This relies on the fact that all objects at a particular height will suffer the same amount of parallax, while objects outside the plane of interest suffer varying degrees of parallax and contribute only noise to the image. This noise evidences itself as a series of discrete blurred versions of objects from out-ofplane structures, repeated at regular spatial intervals along the y-axis. The degree of blurring increases the further away from the plane of interest the object is. Furthermore, the magnitude and spread of these artefacts has been quantified using the artefact spread function (ASF) [1]. Much of the reported work has been in the attempt to reduce these artefacts with varying degrees of success. For example, Chekraborty et al [2], Van der Stelt et al [3], Lui et al [4] and Sone et al [5] in 1996 used high pass filters, and Sone et al [6] in 1991 used band pass filters to refine the resultant image.For the sake of the article we will assume that the xaxis is a horizontal line on an anteroposterior (AP) radiograph and the z-axis is a vertical line, i.e. perpendicular and parallel to the spine, respectively. The y-axis is the depth in or out of the plane of the A...