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PURPOSE: We present a novel silent echo-planar spectroscopic imaging (EPSI) readout, which uses an ultrasonic gradient insert to accelerate MRSI while producing a high spectral bandwidth (20 kHz) and a low sound level.METHODS: The ultrasonic gradient insert consisted of a single-axis (z-direction) plug-and-play gradient coil, powered by an audio amplifier, and produced 40 mT/m at 20 kHz. The silent EPSI readout was implemented in a phase-encoded MRSI acquisition. Here, the additional spatial encoding provided by this silent EPSI readout was used to reduce the number of phase-encoding steps. Spectroscopic acquisitions using phase-encoded MRSI, a conventional EPSI-readout, and the silent EPSI readout were performed on a phantom containing metabolites with resonance frequencies in the ppm range of brain metabolites (0-4 ppm). These acquisitions were used to determine sound levels, showcase the high spectral bandwidth of the silent EPSI readout, and determine the SNR efficiency and the scan efficiency.RESULTS: The silent EPSI readout featured a 19-dB lower sound level than a conventional EPSI readout while featuring a high spectral bandwidth of 20 kHz without spectral ghosting artifacts. Compared with phase-encoded MRSI, the silent EPSI readout provided a 4.5-fold reduction in scan time. In addition, the scan efficiency of the silent EPSI readout was higher (82.5% vs. 51.5%) than the conventional EPSI readout.CONCLUSIONS: We have for the first time demonstrated a silent spectroscopic imaging readout with a high spectral bandwidth and low sound level. This sound reduction provided by the silent readout is expected to have applications in sound-sensitive patient groups, whereas the high spectral bandwidth could benefit ultrahigh-field MR systems.

We estimate the degree and scope of PM2.5-induced negative price shock in Korea’s local housing markets, taking a two-stage hedonic approach. For the analysis, Korea’s local PM2.5 levels are treated as endogenous and are instrumented with regional air pollutants from China. We find that a unit µg/m3 PM2.5 level increase in a Korean city is associated with a 3.7% decline in local residential property value. Long-range transboundary pollution has significant effects on Korea’s local PM2.5 levels with an elasticity of 0.05. These results enrich the sparse hedonic literature on local air-quality valuation in connection to long-range transboundary pollution in East Asia. The advanced methodological features presented in our two-staged identification strategy with a novel instrument is another contribution of this paper.

In this study, we examine pollution effects on urban housing prices in China, using a fixed effects 2SLS model on a 13-year (2005–2017) panel dataset of 237 prefecture-level cities. We find that urban housing prices are negatively associated with PM2.5 levels, presenting an elasticity of – 0.32 for the entire sample. In large cities with an urban population of ≥ 5 million, the elasticity further increases in absolute value to – 0.34, reflecting greater marginal benefit associated with a unit percentage PM2.5 reduction in a higher pollution band. In addition, PM2.5’s effects on housing markets present temporal variations, and the base elasticity of – 0.29 for earlier periods increases to – 0.33 in the post-2008 period, reflecting increased public awareness of pollution-caused health risk after the Beijing Olympic Games. In the post-2014 period, however, the elasticity declines to – 0.24 with stricter pollution regulations introduced in late 2013 as part of the 12th Five Year Plan. Rational expectations regarding continued air-quality improvement in the future may underlie this trend.