Acupuncture is a therapy based on sensory stimulation of the human body by means of metal needles. Functional magnetic resonance imaging (fMRI) has become an important tool in acupuncture research. Standard acupuncture needles, which are made of ferromagnetic steel, however, are problematic in acupuncture-fMRI studies for several reasons, such as attraction by the scanner's magnetic field, significant image distortions and signal-dropouts, when positioned close to the head or even heating due to absorption of radio frequency (RF). The aim of this study was to compare two novel types of acupuncture needles with a standard needle for their effect on MRI image quality. The standard needle severely reduced image quality, when located inside the RF coil. The nonferromagnetic metal needle may pose a risk due to RF heating, while the plastic needle has a significantly larger diameter. In conclusion, our recommendations are: (1) standard needles should not be used in MRI; (2) Nonferromagnetic metal needles seem to be the best choice for acupoints outside of the transmitter coil; and (3) only plastic needles are suited for points inside the coil. Laser acupuncture may be a safe alternative, too.
In summary, among the three needle types tested, the non-ferromagnetic model seems to be the best choice for the application in acupuncture-fMRI studies, if stimulation acupuncture points are situated on the torso or neck but outside of the RF transmitter coil. For points inside the RF coil, we recommend to use the modified catheter approach. Laser acupuncture may be a safe alternative, too.
In conclusion, we hope that the approaches described in this study will lead to new fMRI studies of acupuncture points on the torso as well as on the microsystems on the head.