Detection of Monosodium Urate Crystals for Gout Diagnosis Using Magnetic Fields and Near-Infrared Light

Gouty arthritis is caused by hyperuricemia, and it can develop even when the serum urate level is controlled. Methods to recognize and identify symptoms include polarization microscopy, X-ray imaging, dual-energy computed tomography, magnetic resonance imaging, and ultra-sonography. However, each method has disadvantages, such as not meeting the need for early diagnosis. Hence, no satisfactory method has been established, and alternatives to measuring serum urate levels are desired. Because monosodium urate (MSU) crystals can be rotated by applied magnetic fields, we investigated a method to noninvasively detect the crystals in vivo using magnetic fields and near-infrared light. Because near-infrared light passes through the human body, diagnosis of gout can be performed noninvasively from outside the body. MSU crystals that are equal in size to those accumulated in the human body were prepared in calf serum. Magnetically induced changes in reflected near-infrared light intensity were measured with a spectrophotometer. Specifically, 800-850 nm reflected light intensity changed 5% at 300 mT. Therefore, it may be possible to detect the existence of MSU crystals for the diagnosis of gout by using near-infrared light and a magnetic field.