 Figure 1. Small field of view T1-weighted spoiled gradient magnetic resonance image shows a dilated appendix in a retrocecal position with mild surrounding inflammation (white arrows). Note the distended gravid uterus (red arrows). |  Figure 2. Three-dimensional magnetic resonance cholangiopancreatography image without contrast shows a mildly dilated common bile duct (white arrows) and a small round intraluminal filling defect (red arrow), representing a biliary stone. |
Conclusion
The use of MRI for evaluation of abdominal pain continues to increase. While currently limited to specific vulnerable populations (eg, pregnant patients) or for specific conditions (eg, biliary disease), improving technology and availability will allow this technique to expand to more patients and conditions, including evaluation for inflammatory bowel conditions.
References
1. Saini S, Seltzer SE, Bramson RT, et al. Technical cost of radiologic examinations: Analysis across imaging modalities. Radiology. 2000; 216(1):269-272.
2. Appropriateness criteria. American College of Radiology Web site. http://www.acr.org/Quality-Safety/Appropriateness-Criteria. Accessed September 17, 2013.
3. Pedrosa I, Levine D, Eyvazzadeh AD, Siewert B, Ngo L, Rofsky NM. MR imaging evaluation of acute appendicitis in pregnancy. Radiology. 2006;238(3):891-899.
When a Picture Is Worth a Thousand Images:
3D Reconstruction in Emergency and Trauma Imaging
Jamlik-Omari Johnson, MD; Waqas Shuaib, MD
Dr Johnson is assistant professor of radiology and division director of radiology in the department of radiology and imaging services, division of emergency medicine at Emory University School of Medicine, Atlanta, Georgia. Dr Shuaib is a research associate in the department of radiology and imaging services, division of emergency medicine at Emory University School of Medicine, Atlanta, Georgia.
Three-dimensional (3D) reconstruction creates a digital image of a real-life object, capturing both its original shape and appearance. These techniques simulate reality through the use of lighting, color, and motion.1 Advantages of 3D reconstruction in the emergency and trauma setting include enhanced views of anatomy, making pathology that may be difficult to see in the axial plane easily visible (eg, rib fractures). 3D images may also increase interpretation efficiency, allowing rapid review of the large data sets associated with multidetector computed tomography (MDCT) of trauma patients. Since these images can be attached to the radiology report, this modality also enhances service to referring physicians. In addition, as 3D images succinctly illustrate a diagnosis, the treating physician may share them with patients to demonstrate a condition and explain treatment recommendations.
MDCT technology evolved rapidly over the past 25 years. Between 1992 and 2004, MDCT made quantum leaps from dual detectors to 64-slice scanners, and over the last decade, dual-energy source technology and 128-slice scanners have become integrated into clinical practice. These newer devices, along with technical enhancements, provide high temporal and superior spatial resolution, considerably improved image quality, and expanded clinical applications. With MDCT, scans are performed quickly, resulting in improved temporal resolution and reduced motion artifacts. Leverage of this technology in the emergency and trauma setting has expanded the spectrum of indications for use and increased the utility of CT in urgent care. Newer algorithms allow rapid and detailed examinations of the musculoskeletal and the vascular systems in submillimeter slices, without limitation of scan volume. The high-resolution source images are the basis for high quality 3D reconstructions.
The 3D reconstruction toolbox may benefit the surveillance of anatomy, detection of pathology, and planning of therapy. Examples of three such commonly used techniques are shaded surface display (SSD), maximum intensity projection (MIP), and volume rendering (VR).2
Figure 1. Surface shaded display image showing an anterior communicating artery aneurysm.
SSD provides a realistic 3D view of the surface of a structure within the acquired volume data set and is good at depicting aneurysms and other focal disease (Figure 1). This is particularly useful for evaluating long and tortuous structures, such as the arterial and venous structures. MIP is often used to detect lung nodules by making them stand-out from bronchi and vasculature (Figure 1). Adapted from the computer graphics field, VR creates a 2D image from a 3D model. VR is employed in the exploration of hollow structures, such as the airways or the colon (Figure 2).
Figure 2. Surface shaded display image of a virtual colonoscopy.
Emergency and trauma environments are often fast-paced and high-stakes, and timely and accurate diagnosis is paramount. Therefore, to be useful, advanced 3D-processing tools should be embedded into the diagnostic viewing application (eg, PACS) to allow efficient reconstruction of images, simultaneous comparison of 2D and 3D images, and referencing of historical data in real time.
References
1. Blank M, Kalender WA. Medical volume exploration: gaining insights virtually. Eur J Radiol. 2000;33(3):161-169.
2. Philipp MO, Kubin K, Mang T, Hörmann M, Metz VM. Three-dimensional volume rendering of multidetector-row CT data: applicable for emergency radiology. Eur J Radiol. 2003;48(1):33-38.