559 IMAGING & THERAPEUTIC TECHNOLOGY Clinical Utility of Three-dimensional US 1 Dónal B. Downey, MB, BCh, MSc • Aaron Fenster, PhD • Jacqueline C. Williams, MA Three-dimensional (3D) ultrasonography (US) is rapidly gaining popu- larity as it moves out of the research environment and into the clinical setting. This modality offers several distinct advantages over conven- tional US, including 3D image reconstruction with a single pass of the US beam, virtually unlimited viewing perspectives; accurate assess- ment of long-term effects of treatment; and more accurate, repeatable evaluation of anatomic structures and disease entities. In obstetric im- aging, 3D US provides a novel perspective on the fetal anatomy, makes anomalies easier to recognize, facilitates maternal-fetal bonding, and helps families better understand fetal abnormalities. Three-dimensional pelvic US allows volume data sets to be acquired with both transvagi- nal and transabdominal probes. Viewing multiple 3D power Doppler US images in a fast cine loop has proved useful in angiographic appli- cations. Three-dimensional prostate US can help make accurate vol- ume assessments for dosimetry planning or for estimating prostate- specific antigen levels. In breast imaging, 3D US has the capacity to demonstrate lesion margins and topography, thereby helping differen- tiate benign from malignant masses. Three-dimensional US can also help determine the need for biopsy and help facilitate needle localiza- tion and guidance during biopsy. With recent advances in computer technology and display techniques, 3D US will likely play an increas- ingly important role in medicine. Introduction Conventional radiography merges three-dimensional (3D) data into two-dimensional (2D) summation images. Radiologists mentally reverse this process by forming 3D im- pressions of the underlying anatomy and disease. Tomographic data from ultrasonog- raphy (US), computed tomography (CT), and magnetic resonance (MR) imaging have made this mental reformatting process easier and more accurate. Recent advances in com- puter technology and display techniques promise to make medical imaging data even more accessible and clinically useful. Real-time 3D display, reformatting, and manipu- lation of US, CT, and MR images are now possible on inexpensive desktop computers. Abbreviations: 3D = three-dimensional, 2D = two-dimensional Index terms: Ultrasound (US), technology • Ultrasound (US), three-dimensional, .1298 2 • Ultrasound (US), utilization RadioGraphics 2000; 20:559–571 1 From the Department of Diagnostic Radiology and Nuclear Medicine, London Health Sciences Centre, 339 Windermere Rd, London, Ontario, Canada N6A 5A5 (D.B.D., A.F., J.C.W.), and the John P. Robarts Research Institute, London, Ontario, Canada (D.B.D., A.F.). Presented as a scientific exhibit at the 1998 RSNA scientific assembly. Received April 13, 1999; revision requested May 17 and final revision received November 3; accepted November 3. Supported in part by grants from the Medical Research Council of Canada and the University Hospital (London) Re- search Foundation. Address reprint requests to D.B.D. (e-mail: ddowney@irus.rri.on.ca). 2 . indicates multiple body systems. © RSNA, 2000