Direct MR arthrography at 1.5 and 3.0 T: signal dependence on gadolinium and iodine concentrations--phantom study

PURPOSE: To prospectively quantify in vitro the influence of gadopentetate dimeglumine and ioversol on the magnetic resonance (MR) imaging signal observed with a variety of musculoskeletal pulse sequences to predict optimum gadolinium concentrations for direct MR arthrography at 1.5 and 3.0 T. MATERIALS AND METHODS: In an in vitro study, T1 and T2 relaxation times of three dilution series of gadopentetate dimeglumine (concentration, 0-20.0 mmol gadolinium per liter) at ioversol concentrations with iodine concentration of 0, 236.4, and 1182 mmol iodine per liter (corresponding to 0, 30, and 150 mg of iodine per milliliter) were measured at 1.5 and 3.0 T. The relaxation rate dependence on concentrations of gadolinium and iodine was analytically modeled, and continuous profiles of signal versus gadolinium concentration were calculated for 10 pulse sequences used in current musculoskeletal imaging. After fitting to experimental discrete profiles, maximum signal-to-noise ratio (SNR), gadolinium concentration with maximum SNR, and range of gadolinium concentration with 90% of maximum SNR were derived. The overall influence of field strength and iodine concentration on these parameters was assessed by using t tests. The deviation of simulated from experimental signal-response profiles was assessed with the autocorrelation of the residuals. RESULTS: The model reproduced relaxation rates of 0.37-38.24 sec(-1), with a mean error of 4.5%. Calculated SNR profiles matched the discrete experimental profiles, with autocorrelation of the residuals divided by the mean of less than 5.0. Admixture of ioversol consistently reduced T1 and T2, narrowed optimum gadolinium concentration ranges (P = .004-.006), and reduced maximum SNR (P < .001 to not significant). Optimum gadolinium concentration was 0.7-3.4 mmol/L at both field strengths. At 3.0 T, maximum SNR was up to 75% higher than at 1.5 T. CONCLUSION: Admixture of ioversol to gadopentetate dimeglumine solutions results in a consistent additional relaxation enhancement, which can be analytically modeled to allow a near-quantitative a priori optimized match of contrast media concentrations and imaging protocol for a broad variety of pulse sequences.

Communicating Severity of Hazard with the Signal Word on a Safety Sign

An experiment examined five signal words on safety signs for effectiveness at communicating information about severity of a hazard. Perceived severity was rated by 59 college students for the signal words Deadly, Danger, Warning, Caution, and Notice. Results indicated that Deadly communicated the highest ratings for severity. Danger was second. Warning and Caution were tied for third. The lowest ratings were for Notice.

Comparison of Student Versus Employee Test Populations for Warning Sign Research Based on Severity Ratings for Signal Words

Most studies of warning signs involve undergraduate students as subjects. This paper reports a direct comparison of findings from an undergraduate population and an employed population. The 48 employed subjects from this study were compared with 59 undergraduate subjects from a companion study. Subjects from both populations were shown the same signs and asked to rate the severity level connoted by each sign. The signs differed only in signal word. Results for each population indicated that signal word had a highly significant effect on severity ratings. When the two populations were compared for ratings of each signal word, the only significant difference was for Caution. Median ratings of each population were the same: Deadly (4), Danger (3), Warning (2), Caution (1), and Notice (0).

Photonics Crystals: The Future of Microwave Signal Processing

The ability of cryogenic photonic crystals to carry out high performance microwave signal processing operations has been developed into systems that can: rapidly record broadband microwave spectra with fine resolution and high dynamic range; search for patterns in 40 gigabits per second data streams; and communicate via spread- spectrum signals that are well below the noise floor. The basic concepts of the technology and its many applications, along with an overview of university-industry partnerships and the growing photonics industry in Bozeman, will be presented.

TV Signal Delivery to Cable Operators and DTH Platform Operators

The paper discusses new business models of transmission of television programs in the context of definitions of broadcasting and retransmission. Typically the whole process of supplying content to the end user has two stages: a media service provider supplies a signal assigned to a given TV channel to the cable operators and satellite DTH platform operators (dedicated transmission), and cable operators and satellite DTH platform operators transmit this signal to end users. In each stage the signals are encoded and are not available for the general public without the intervention of cable/platform operators. The services relating to the supply and transmission of the content are operated by different business entities: each earns money separately and each uses the content protected by copyright. We should determine how to define the actions of the entity supplying the signal with the TV program directly to the cable/digital platform operator and the actions of the entity providing the end user with the signal. The author criticizes the approach presented in the Chellomedia and Norma rulings, arguing that they lead to a significant level of legal uncertainty, and poses the basic questions concerning the notion of “public” in copyright.

Simulating the temperature and precipitation signal in an Alpine ice core

Accumulation and delta O-18 data from Alpine ice cores provide information on past temperature and precipitation. However, their correlation with seasonal or annual mean temperature and precipitation at nearby sites is often low. This is partly due to the irregular sampling of the atmosphere by the ice core (i.e. ice cores almost only record precipitation events and not dry periods) and the possible incongruity between annual layers and calendar years. Using daily meteorological data from a nearby station and reanalyses, we replicate the ice core from the Grenzgletscher (Switzerland, 4200m a.s.l.) on a sample-by-sample basis by calculating precipitation-weighted temperature (PWT) over short intervals. Over the last 15 yr of the ice core record, accumulation and delta O-18 variations can be well reproduced on a sub-seasonal scale. This allows a wiggle-matching approach for defining quasi-annual layers, resulting in high correlations between measured quasi-annual delta O-18 and PWT. Further back in time, the agreement deteriorates. Nevertheless, we find significant correlations over the entire length of the record (1938-1993) of ice core delta O-18 with PWT, but not with annual mean temperature. This is due to the low correlations between PWT and annual mean temperature, a characteristic which in ERA-Interim reanalysis is also found for many other continental mid-to-high-latitude regions. The fact that meteorologically very different years can lead to similar combinations of PWT and accumulation poses limitations to the use of delta O-18 from Alpine ice cores for temperature reconstructions. Rather than for reconstructing annual mean temperature, delta O-18 from Alpine ice cores should be used to reconstruct PWT over quasi-annual periods. This variable is reproducible in reanalysis or climate model data and could thus be assimilated into conventional climate models.