Medical Physics Research Today is a free monthly online journal that collates and summarizes the latest research about Medical Physics, including details on medicine, radiotherapy, biomechanics, medical imaging.

Neuro MR: Protocols.

Mikulis DJ, Roberts TP

Department of Medical Imaging, The University Health Network, The Toronto Western Hospital, Toronto, ON, Canada.

Clinical MRI depends on a symbiosis between MR physics and clinical requirements. The imaging solutions are based on a balance between the "palette" of available image contrasts derived from nuclear spin physics and tissue biophysics, and clinical determinants such as the anticipated pathology and efficient use of imaging time. Imaging is therefore optimized to maximize diagnostic sensitivity and specificity through the development of protocols organized along the lines of major disease categories. In the other part of this two-part review, the primary determinants of image contrast, including T1, T2, and T2*, were highlighted. The development of pulse sequences designed to optimize each of these image contrasts was discussed and the impact of technological innovation (parallel imaging and high-field systems) on the manner in which these sequences could be modified to improve clinical efficacy was further emphasized. The scope of that discussion was broadened to include the application of: 1) water diffusion imaging used primarily for detection of pathologies that restrict the free movement of water in the tissues and for defining fiber tracts in the brain; 2) the intravenous administration of exogenous contrast agents (gadolinium-diethylene triamine pentaacetic acid [GdDTPA]) for assessment of blood-brain-barrier (BBB) defects and brain blood flow; and 3) MR spectroscopy (MRS) for assessment of brain metabolites. The goal of this part is to discuss how these acquisitions are combined into specific protocols that can effectively detect and characterize, or in keeping with our artistic analogy, "paint" each of the major diseases affecting the central nervous system (CNS). This work concludes with a discussion of image artifacts and pitfalls in image interpretation, which, in spite our best efforts to minimize or eliminate them, continue to occur. Much of the ensuing discussion is based on our own institutional experience. Protocols, therefore, do not necessarily match those from other institutions due to variability in clinical emphasis, MR instruments, and available software. An attempt was made to focus on basic clinical sequences that are available on most modern MR systems, with protocols employing generally accepted clinical imaging philosophies. J. Magn. Reson. Imaging 2007;26:838-847. (c) 2007 Wiley-Liss, Inc.

Published 26 September 2007 in J Magn Reson Imaging, 26(4): 838-847.
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Articles on Medical Physics published 26 September 2007:

Absolute quantification of cerebral blood flow in normal volunteers: Correlation between Xe-133 SPECT and dynamic susceptibility contrast MRI.   J Magn Reson Imaging, 26(4): 913-920.

PURPOSE: To compare absolute cerebral blood flow (CBF) estimates obtained by dynamic susceptibility contrast MRI (DSC-MRI) and Xe-133 SPECT. MATERIALS AND METHODS: CBF was measured in 20 healthy volunteers using DSC-MRI at 3T and Xe-133 SPECT. DSC-MRI was accomplished by gradient-echo EPI and CBF was calculated using a time-shift-insensitive deconvolution algorithm and regional arterial input functions (AIFs). To improve the reproducibility of AIF registration the time integral was rescaled by ... [Abstract] [Full-text]

Articles on Medical Physics published 20 September 2007:

Dynamic Contrast-Enhanced Magnetic Resonance Imaging for Localization of Recurrent Prostate Cancer after External Beam Radiotherapy.   Int J Radiat Oncol Biol Phys.

PURPOSE: To compare the performance of T2-weighted (T2w) imaging and dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) of the prostate gland in the localization of recurrent prostate cancer in patients with biochemical failure after external beam radiotherapy (EBRT). METHODS AND MATERIALS: T2-weighted imaging and DCE MRI were performed in 33 patients with suspected relapse after EBRT. Dynamic contrast-enhanced MRI was performed with a temporal resolution of 95 s. Voxels enhancing ... [Abstract] [Full-text]

Structural Effects on the Biodistribution and Positron Emission Tomography (PET) Imaging of Well-Defined (64)Cu-Labeled Nanoparticles Comprised of Amphiphilic Block Graft Copolymers.   Biomacromolecules.

The synthesis of poly(methyl methacrylate-co-methacryloxysuccinimide-graft-poly(ethylene glycol)) (PMMA-co-PMASI-g-PEG) via living free radical polymerization provides a convenient route to well-defined amphiphilic graft copolymers having a controllable number of reactive functional groups, variable length PEG grafts, and low polydispersity. These copolymers were shown to form PMMA-core/PEG-shell nanoparticles upon hydrophobic collapse in water, with the hydrodynamic size being defined by the ... [Abstract] [Full-text]

Articles on Medical Physics published 17 September 2007:

Switching benchmarks in cancer of unknown primary: From autopsy to microarray.   Eur J Cancer, 43(14): 2026-36.

INTRODUCTION: Cancer of unknown primary (CUP) is associated with unknown biology and dismal prognosis. Information on the primary site of origin is scant and has never been analysed. We systematically reviewed all published evidence on the CUP primary site identified by two different approaches, either autopsy or microarray gene expression profiling. METHODS: Published reports on identification of CUP primary site by autopsy or microarray-based multigene expression platforms were retrieved and ... [Abstract] [Full-text]

Articles on Medical Physics published 14 September 2007:

A path algorithm for the support vector domain description and its application to medical imaging.   Med Image Anal, 11(5): 417-28.

The support vector domain description is a one-class classification method that estimates the distributional support of a data set. A flexible closed boundary function is used to separate trustworthy data on the inside from outliers on the outside. A single regularization parameter determines the shape of the boundary and the proportion of observations that are regarded as outliers. Picking an appropriate amount of regularization is crucial in most applications but is, for computational ... [Abstract] [Full-text]

Articles on Medical Physics published 13 September 2007:

Will haptic feedback speed up medical imaging? An application to radiation treatment planning.   Acta Oncol.

Haptic technology enables us to incorporate the sense of touch into computer applications, providing an additional input/output channel. The purpose of this study was to examine if haptic feedback can help physicians and other practitioners to interact with medical imaging and treatment planning systems. A haptic application for outlining target areas (a key task in radiation therapy treatment planning) was implemented and then evaluated via a controlled experiment with ten subjects. Even ... [Abstract] [Full-text]

Articles on Medical Physics published 12 September 2007:

Volume rendering based on magnetic resonance imaging: advances in understanding the three-dimensional anatomy of the human knee.   J Anat, 211(3): 399-406.

The choice of medical imaging techniques, for the purpose of the present work aimed at studying the anatomy of the knee, derives from the increasing use of images in diagnostics, research and teaching, and the subsequent importance that these methods are gaining within the scientific community. Medical systems using virtual reality techniques also offer a good alternative to traditional methods, and are considered among the most important tools in the areas of research and teaching. In our work ... [Abstract] [Full-text]

Primary gastrointestinal lymphoma: spectrum of imaging findings with pathologic correlation.   Radiographics, 27(5): 1371-88.

Gastrointestinal lymphoma is an uncommon disease but is the most frequently occurring extranodal lymphoma and is almost exclusively of non-Hodgkin type. Primary gastrointestinal lymphoma most commonly involves the stomach but can involve any part of the gastrointestinal tract from the esophagus to the rectum. Risk factors for the development of gastrointestinal lymphoma include Helicobacter pylori infection, immunosuppression after solid organ transplantation, celiac disease, inflammatory bowel ... [Abstract] [Full-text]

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