Signal Processing

Harnessing the power of fast digital computers to US has resulted in a number of important improvements in imaging and in convenience and reproducibility (3). The discovery that sound propagates through the tissue in a nonlinear fashion to produce overtones of the transmitted signal (harmonics) has improved contrast resolution and reduced artifacts that result from beam imperfections (4). The principle is simple tissue is slightly compressed during the positive pressure phase of the ultrasonic...

Differences Between Single Detector and Multidetector CT

On a single detector CT (SDCT) scanner, the detector consists of a single slab of ceramic material and the slice thickness is simply determined by the collimator (Fig. 2). In comparison, on a multidetector CT (MDCT) scanner the detector has a matrix array, which consists of a ceramic detector divided into small individual pieces separated by thin metallic septae (29,30). With these scanners, the slice thickness is determined not only by the collimator but also by the detector configuration...

Mr Imaging Imaging Plane

Although axial imaging is often adequate, additional or alternative imaging planes may be warranted depending on the anatomic region that is being studied. For Figure 1 Malignant portal adenopathy in a patient with colon cancer. (A) Unenhanced T2-weighted image shows enlarged, hyperintense nodes (arrow) surrounding the portal vein. (B) Postferumoxtran-10 image shows a heterogeneous uptake (arrow) in medial nodes with the areas of darkening representing preserved nodal macrophages the areas of...

Contributors

Alger Department of Radiological Sciences, Ahmanson-Lovelace Brain Mapping Center, Brain Research Institute, Jonsson Comprehensive Cancer Center, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California, U.S.A. Jelle Barentsz Department of Radiology, Radboud University Medical Center Nijimegen, Nijimegen, The Netherlands Martin Blomley Imaging Sciences Department, Imperial College, Hammersmith Hospital, London, U.K. John Butman Diagnostic Radiology...

References

Overview and fundamentals of medical image segmentation. In Bankman IN, ed. Handbook of Medical Imaging, Processing and Analysis, Academic Press, 2000. 2. Rosenfeld A, Kak AC. Digital image processing. Academic Press, 1982. 3. Adams R, Bischof L. Seeded region growing. IEEE Trans Pattern Anal Mach Intell 1994 16 641-647. 4. Vince L, Soille P. Watersheds in digital spaces an efficient algorithm based on immersion simulations. IEEE Trans Pattern Anal Mach Intell 1991 13(6) 583-598. 5....

Principles Of

PET is a functional imaging modality that employs radiotracers to exploit altered metabolic and biochemical function in vivo. Until the early 1990s, because of a limited axial field of view within the scanner, the technique was reserved almost exclusively for neuropsychiatric and cardiac research. With the advent of a simple change in scanner design, which allowed passage of the scanning couch through the gantry, it became possible to perform whole-body PET. Subsequently oncological imaging has...

A

Figure 4 Pathologically proved benign lymph node in a patient with prostate cancer. Axial MR images, obtained with a 3 mm section thickness before (A) and after (B) administration of ferumoxtran-10 show a node (circle) with peripheral uptake of contrast material and a prominent central fatty hilum. Thin sections allow robust nodal characterization. Source From Ref. 12. Figure 4 Pathologically proved benign lymph node in a patient with prostate cancer. Axial MR images, obtained with a 3 mm...

Fundamental Advantages of MDCT

Undersampling

The first advantage of MDCT is the ability to scan a lot faster while acquiring a dataset with similar slice thickness and image quality to that of SDCT. Faster table speeds are particularly advantageous in patients with reduced breath-holding capacity since table speeds on the order of 50 to 70 mm per second are achievable. Fast table speeds are often chosen in the setting of trauma, in patients with dyspnea, in young children or in those patients in whom there are communication difficulties...