Development of a portable pneumomagnetic measurement device.

For some time, we have been using a large device, in our laboratory, to measure the remanent field from magnetic contaminants in the human lung (magnetopneumography, or MPG). But this device is too large and cumbersome to transport to worksites to assess the magnetic contaminants in the lungs of workers. Further, it is inconvenient and expensive for workers of small or medium-sized companies to come to our campus to be magnetically examined. To solve this problem, we have developed a succession of portable devices which can easily be transported to worksites to perform MPG measurements. We here describe our most recent portable MPG device, and present a typical result of the MPG measurements. The lungs of many workers have so far been measured, and we find that the device can produce accurate measurements at the worksites, beyond our expectation. One reason, we find, is that the background magnetic noise at worksites usually is much less than that at our Kanda campus, located in the center of Tokyo, where the level of magnetic noise caused by subways is high. Therefore, some measurements, which are unable to be done at our campus,can be successfully completed at worksites by using this portable device. We note that the level of the magnetic noise during the recordings greatly depends on the exact location of the workplace measuring site.