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11 May 1994 Importance of ray pathlengths when measuring objects in maximum intensity projection images
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It is important to understand any process that affects medical data. Once the data has changed from its original form, one must consider the possiblity that the information contained in the data has also changed. In general, false negative and false positive diagnoses caused by this post-processing must be minimized. Medical imaging is one area in which post-processing is commonly performed, but often there is little or no discussion of how these algorithms affect the data. This study uncovers some interesting properties of maximum intensity projection (MIP) algorithms that are commonly used in the post-processing of magnetic resonance angiographic data. Of particular interst to clinicians is the appearance of the width of vessels and the extent of malformations such as aneurysms. This study will show how MIP algorithms interact with the shape of the object being projected. MIPs can make objects appear thinner in the projection than in the original data set and also alter the shape of the profile of the object seen in the original data. These effects have consequences for width measuring algorithms which will be discussed. In addition to the computer generated model, a static MR phantom was imaged. The phantom verified that Equation (1) predicts the projection plane intensities well (r=.98) for a constant-intensity object.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Steven Schreiner, Benoit M. Dawant, Cynthia B. Paschal, and Robert L. Galloway Jr. "Importance of ray pathlengths when measuring objects in maximum intensity projection images", Proc. SPIE 2167, Medical Imaging 1994: Image Processing, (11 May 1994);

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