Contrast behavior and relaxation effects of conventional and hyperecho-turbo spin echo sequences at 1.5 and 3 T.

To overcome specific absorption rate (SAR) limitations of spin-echo-based MR imaging techniques, especially at (ultra) high fields, rapid acquisition relaxation enhancement/TSE (turbo spin echo)/fast spin echo sequences in combination with constant or variable low flip angles such as hyperechoes and TRAPS (hyperTSE) have been introduced. Due to the multiple spin echo and stimulated echo pathways involved in the signal formation, the contrast behavior of such sequences depends on both T2 and T1 relaxation times. In this work, constant and various variable flip angle sequences were analyzed in a volunteer study. It is demonstrated that a single effective echo time parameter TE(eff) can be calculated that accurately describes the overall T2 weighted image contrast. TE(eff) can be determined by means of the extended phase graph concept and is practically independent of field strength. Using the described formalism, the contrast of any TSE sequence can be predicted. HyperTSE sequences are demonstrated to show a robust and well-defined T2 contrast allowing clinical routine MRI to be performed with SAR reductions of typically at least 70%.     

Consensus statement on the bio-safety of urinary-derived gonadotrophins with respect to Creutzfeldt-Jakob disease

Human transmissible spongiform encephalopathies (TSE) encompass a group of rare neurodegenerative diseases. In April 2004, a group of international experts and regulators met in Buenos Aires, Argentina, to review the safety and to reach consensus on the use of urinary-derived gonadotrophins with respect to TSE. Iatrogenic transmission of Creutzfeldt-Jakob Disease (CJD) from pituitary-derived gonadotrophins has been reported, no infectivity in urine has been demonstrated, and no definite cases of transmission via urine have been reported. It is currently not possible to monitor donor urine or finished product for the presence of prions. Therefore the assessment of risk has to be based on the likelihood of infection in urine, the source of the urine, and the capacity of the manufacturing process to remove any adventitious infection. Urine for the production of medicinal products should be obtained from sources that minimize the possible presence of materials derived from subjects suffering from human TSE. As no strong evidence for TSE infectivity in urine exists, it can be concluded that the risk of disease-generating prions and TSE infectivity being present in donor urine is low. Current evidence indicates that, with respect to the risk of TSE infection, urinary-derived gonadotrophins appear to be safe.     

Constant Transmission Properties of Variant Creutzfeldt-Jakob Disease in 5 Countries

Variant Creutzfeldt-Jakob disease (vCJD) has been reported in 12 countries. We hypothesized that a common strain of agent is responsible for all vCJD cases, regardless of geographic origin. To test this hypothesis, we inoculated strain-typing panels of wild-type mice with brain material from human vCJD case-patients from France, the Netherlands, Italy, and the United States. Mice were assessed for clinical disease, neuropathologic changes, and glycoform profile; results were compared with those for 2 reference vCJD cases from the United Kingdom. Transmission to mice occurred from each sample tested, and data were similar between non-UK and UK cases, with the exception of the ranking of mean clinical incubation times of mouse lines. These findings support the hypothesis that a single strain of infectious agent is responsible for all vCJD infections. However, differences in incubation times require further subpassage in mice to establish any true differences in strain properties between cases.     

Post-contrast 3D T1-weighted TSE MR sequences (SPACE,CUBE, VISTA/BRAINVIEW,isoFSE, 3D MVOX): Technical aspects and clinical applications

Post-contrast three-dimensional T1-weighted imaging of the brain is widely used for a broad range of vascular, inflammatory or tumoral diseases. The variable flip angle 3D TSE sequence is now available from several manufacturers (CUBE, General Electric; SPACE, Siemens; VISTA/BRAINVIEW, Philips; isoFSE, Itachi; 3D MVOX, Canon). Compared to gradient-echo (GRE) techniques, 3D TSE offers the advantages of useful image contrasts and reduction of artifacts from static field inhomogeneity. However, the respective role of 3D TSE and GRE MR sequences remains to be elucidated, particularly in the setting of post-contrast imaging. The purpose of this review was (1) to describe the technical aspects of 3D TSE sequences, (2) to illustrate the main clinical applications of the post-contrast 3D T1-w TSE sequence through clinical cases, (3) to discuss the respective role of post-contrast 3D TSE and GRE imaging in the field of neuroimaging.     

Prostatic Artery Embolization with 250-μm Spherical Polyzene-Coated Hydrogel Microspheres for Lower Urinary Tract Symptoms with Follow-up MR Imaging

Purpose

To evaluate clinical outcomes and possible MR imaging predictors of clinical success after prostatic artery embolization (PAE) with 250-μm hydrogel particles.

Quality comparison between three-dimensional T2-weighted SPACE and two-dimensional T2-weighted turbo spin echo magnetic resonance images for the brachytherapy planning evaluation of prostate and periprostatic anatomy

PurposeThe purpose of this study was to compare an isotropic three-dimensional (3D) T2-weighted sequence sampling perfection with application-optimized contrasts by using flip angle evolution (SPACE) with an axial two-dimensional T2-weighted turbo spin echo (TSE) sequence with regard to overall image quality and the delineation of normal prostate and periprostatic anatomy for low-dose-rate prostate cancer brachytherapy planning evaluation.Methods and MaterialsPatients (n = 69) with prostate cancer who had pelvic magnetic resonance imaging (MRI) for low-dose-rate brachytherapy treatment planning were included. Three radiologists independently assessed the visibility of nine anatomic structures on each sequence by using a 5-point scale and overall image quality by using a 4-point scale. The significance of the differences in diagnostic performance was tested with a Wilcoxon signed rank test.ResultsNo significant intersequence differences were found for most (7/9) anatomical structures and overall image quality. The mean scores for visibility of anatomical structures on the 3D SPACE and 2D TSE sequences, respectively, were as follows: the zonal anatomy (3.7; 3.9, p = 0.05), prostate capsule (3.9; 4.0, p = 0.08), neurovascular bundle (2.9; 2.9, p = 0.9), rectoprostatic angle (3.8; 3.8, p = 0.35), rectum (4.2; 4.3, p = 0.26), urethra (3.8; 3.9, p = 0.12), urinary bladder (4.6; 4.6, p = 0.61), and overall image quality (2.9; 2.9, p = 0.33). 3D SPACE was superior for delineation of the genitourinary diaphragm (3.8; 3.6, p = 0.003), whereas 2D TSE was superior for delineation of the seminal vesicles (3.5; 4.0, p < 0.0001).ConclusionsAnatomic delineation of the prostatic and periprostatic anatomy provided by the 3D SPACE sequence is as robust in quality as that provided by a conventional 2D TSE sequence with superior delineation of the genitourinary diaphragm. For MRI-based brachytherapy treatment planning, the 3D SPACE sequence with subcentimeter isotropic resolution can replace the 2D TSE sequence and be incorporated into standard MRI protocols.     

Environmental sources of prion transmission in mule deer

Whether transmission of the chronic wasting disease (CWD) prion among cervids requires direct interaction with infected animals has been unclear. We report that CWD can be transmitted to susceptible animals indirectly, from environments contaminated by excreta or decomposed carcasses. Under experimental conditions, mule deer (Odocoileus hemionus) became infected in two of three paddocks containing naturally infected deer, in two of three paddocks where infected deer carcasses had decomposed in situ =1.8 years earlier, and in one of three paddocks where infected deer had last resided 2.2 years earlier. Indirect transmission and environmental persistence of infectious prions will complicate efforts to control CWD and perhaps other animal prion diseases.     

Barriers to Creutzfeldt-Jakob disease autopsies, California

Creutzfeldt-Jakob disease (CJD) surveillance relies on autopsy and neuropathologic evaluation. The 1990-2000 CJD autopsy rate in California was 21%. Most neurologists were comfortable diagnosing CJD (83%), but few pathologists felt comfortable diagnosing CJD (35%) or performing autopsy (29%). Addressing obstacles to autopsy is necessary to improve CJD surveillance.