Percutaneous microballoon compression (PMC) is a well-established technique for treatment of trigeminal neuralgia (TN). However, direct puncture of the foramen ovale (FO) is sometimes difficult and there have been well-reported complications from cannulating the FO. We describe our experiences in using Dyna-CT for cannulating the FO and determining balloon position and volume. Dyna-CT was used to perform image reconstruction in 21 cases. The optimal working projection was generated and further fluoroscopic data were used to determine the needle's relationship to the foramen during puncture. Furthermore, the balloon position and three-dimensional shape were verified by Dyna-CT during balloon compression. The balloon volume and puncture angle were further calculated. Patients' prognosis was further discussed. Dyna-CT allowed quick, safe, and easy cannulation of the FO. It provided three-dimensional images which were more elaborate than the classic 'pear-shaped' images for determining correct positioning in 21 cases. The volume of the flattened balloon ranged from 568.2 mm(3) to 891.4 mm(3) with an average of 775.9 mm(3). The angle of introducing the cannula ranged from 15.17°-35.48° rotation to the midline with an average of 26.24° and 38.47°-51.89° angulation to the Reid line with an average of 46.09°. All the patients were pain free after PMC. Four patients had resolvable masseter weakness and fine touch loss. There was no recurrence of TN during follow-up. Dyna-CT demonstrated three advantages in assisting PMC. Firstly, the FO can be better visualized irrespective of the patient's position. Secondly, needle correction or insertion can be performed much more easily because of the direct fluoroscopic control. Thirdly, the needle position, balloon position, balloon configuration and the volume of the inflated balloon are more reliably determined. The use of dyna-CT provided an assisted method to PMC with a low incidence of complications and good prognosis.