Dynamic Contrast-Enhanced MR Imaging in the Evaluation of Patients with Prostate Cancer
Prostate cancer is a common tumor among men, with increasing diagnosis at an earlier stage and a lower volume of disease because of screening with prostate-specific antigen (PSA). The need for imaging of the prostate stems from a desire to optimize treatment strategy on a patient and tumor-specific level. The major goals of prostate imaging are (1) staging of known cancer, (2) determination of tumor aggressiveness, (3) diagnosis of cancer in patients who have elevated PSA but a negative biopsy, (4) treatment planning, and (5) the evaluation of therapy response. This article concentrates on the role of dynamic contrast-enhanced MR imaging in the evaluation of patients who have prostate cancer and how it might be used to help achieve the above goals. Various dynamic contrast enhancement approaches (quantitative/semiquantitative/qualitative, high temporal versus high spatial resolution) are summarized with reference to the relevant strengths and compromises of each approach.
Available from: Philippe Puech
- "The MRI evaluation of the seminal vesicles is facilitated by contrast-enhanced sequences that improve their visualization and study in approximately 23% of cases, especially for inexperienced readers . As for direct extraprostatic extension, these results are debatable in certain series  . Evidence for seminal vesicle invasion is based on two signs, whose reliability is even better when combined : filling of the seminal lumen and presence of asymmetrical or nodular seminal enhancement (Fig. 4). "
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ABSTRACT: Multiparametric MRI (mp-MRI) of the prostate currently provides stable and reproducible performances. The usefulness of dynamic contrast-enhanced (DCE) sequences is currently challenged, as they sometimes only confirm what has already been observed on diffusion-weighted imaging (DWI) and require the additional purchase of a contrast agent. Eliminating these sequences may help accelerate the use of MRI in addition to, or in lieu of, prostate biopsies in selected patients. However, many studies show that these sequences can detect lesions invisible on T2-weighted and diffusion-weighted images, better assess cancer extension and aggressiveness, and finally help detecting recurrence after treatment. We present the various applications of dynamic MRI and discuss the possible consequences of its omission from the current protocol.
Available from: hig.diva-portal.org
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ABSTRACT: A series of traveling-wave amplifier tubes which employ lightweight permanent-magnet periodic focusing are described. These tubes have a combined frequency coverage from 1.0 to 11.0 kmc. The tubes employ parallel flow focusing of the electron beam and thereby avoid the complications of convergent flow magnetically-shielded electron gun construction. This type of focusing has the further advantage of using the same tubes as those where focusing is accomplished by solenoidal magnetic field. Control of the electron beam in the gun and the entrance conditions of the beam into the periodic helix field is accomplished by shaping of a magnetic field over the gun region.
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