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KEY TERMS

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Key Terms

  1. Volumetric (three-dimensional) imaging: recording and interacting with images that reproduce a structure’s dimensions of length, width, and height, rather than individual tomographic slices. It is obtained by integrating many two-dimensional (2D) acquisitions into a volume to form a multiplanar reconstruction.

  2. Four-dimensional imaging: volumetric images obtained over a period of time.

  3. Coronal plane: the plane perpendicular to the sagittal and transverse planes that demarcates anterior and posterior portions of three-dimensional (3D) structures.

  4. Three-dimensional inversion display: a “cast” is formed of the cystic areas within a volume while the solid areas are made “lucent.” This forms a positive display of anechoic structures, which can be combined with color Doppler data to also visualize fluid or blood flow within.

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INTRODUCTION

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Three-dimensional (3D) volume imaging of the female pelvis is one of the most important advances in women’s imaging within the last decade.1,2 Volume imaging is not new to radiology, as it has been used extensively as part of computed tomography (CT) and magnetic resonance (MR) imaging for several decades. Sonographic imaging, however, has been relegated for more than 30 years to individual acquisitions of thin two-dimensional (2D) tomographic image slices that are operator dependent and time consuming to obtain.3 The quality of the individual 2D images are largely dependent on the expertise of the operator that produces them, and even a careful review of these individual “snapshots” will often fail to demonstrate pathology if the operator did not perceive the abnormal finding.

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More recently, 3D sonography has enabled us to move sonographic imaging into a new era of rapid, automated, and comprehensive imaging and displays.1-4 Images of the entire pelvis can be accomplished with only three volume acquisitions: one of the uterus and one of each ovary.4 These volume acquisitions typically contain all of the sonographic anatomic information within the pelvis, thus affording improved perception of the overall global anatomy. They can subsequently be rescanned electronically in any plane by a different operator who may be off site.1-4

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TECHNICAL CONSIDERATIONS

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The earliest 3D ultrasound probes required manual sweeps through a volume of interest, typically in the sagittal plane (Figures 49-1 and 49-2). This “freehand” method collects a series of consecutive 2D slices. The current methods of sonographic volume acquisition utilize automated transducers, which have a dedicated 3D probe within their housing, mechanized to gather 2D sonographic information from one side of the probe to the other. The operator holds the transducer still while the probe sweeps from one side of the housing to the other, thus acquiring the volume in a smoother, more systematic and reproducible fashion in less than 15 seconds. However, the faster the speed of this mechanical acquisition, the lower the resolution of the images. Different types of processing can also modify the quality and appearance of the volume data, such as the ...

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