Cold pressor gel test: A safe alternative to the cold pressor test in fMRI

Purpose: This study describes a new methodology-the cold pressor gel test (CPGT)-for delivering an accessible experimental pain stimulus, which is reproducible and safe for functional MRI (fMRI).

Methods: The cold pressor test was modified to put safety precautions into the CPGT. The material used is cool gelled water with a thickening product, which provides a stable temperature at 0.2 °C. Thirteen women with chronic pelvic pain were scanned using a 3 Tesla (T) MR scanner equipped with a 12-channel head coil. Changes in BOLD activation during cold-induced pain were estimated.

Results: The results have demonstrated that gel substances maintain a stable temperature during the experiment, resulting in an insignificant variation. Before the experiment, the mean temperature was 0.2 ± 0.11 °C, and at the end it was 0.7 ± 0.15 °C. The time taken by participants to reach the maximum level of pain during the CPGT was 56.92 ± 11.09 s. The pain intensity during the experiments was 6.92 ± 1.66 on the visual analog scale (VAS). The fMRI analysis showed significant BOLD activation in the main brain regions involved in chronic pain processing.

Conclusion: The CPGT is an experimental tool to deliver pain that is easily reproducible, particularly in brain functional imaging studies. Moreover, it is cost-effective, safe, and compatible with fMRI. Magn Reson Med 78:1464-1468, 2017. © 2016 International Society for Magnetic Resonance in Medicine.