A comparison of patient entrance skin exposure for videofluoroscopic and functional plain x-ray techniques used in cervical spine kinematics

Functional radiography has long been used to observe the kinematic behaviour of the vertebral segments of the cervical spine, especially under the influence of spinal injury and other mechanical problems. Potentially high patient entrance skin exposures have been suggested by some authors as one reason for not utilising videofluoroscopy in cervical spine kinematics despite mathematical estimates that dose rates, when compared with plain film radiography, should be lower. This study compared actual skin entry exposure measurements for a 5-second videofluoroscopic scan with 3 plain film x-ray exposures of the lateral cervical spine. Measurements were made using LiF-100 thermoluminescent dosimetry on an anthropomorphic model. The thermoluminescent dosimeter chips directly exposed to the primary beams at C1, C4 and C7 recorded approximately twice the skin exposure during plain radiography (mean: 4551.03 mGy) than when compared with the 5-second videofluoroscopy (mean: 2242.24 mGy). These results indicated, therefore, that the patient skin entrance radiation dose is significantly less during a 5-second videofluoroscopic scan of the cervical spine than that experienced during the 3 plain x-ray neutral lateral, flexion and extension views. This study has demonstrated that concerns over possible high radiation doses associated with functional videofluoroscopic screening for determining cervical spine kinematics are unfounded. The development of the use of videofluoroscopy for cervical spine kinematics should not be limited due to concerns that the procedures produce high patient skin entrance exposure.