Optimising Conventional Radiographic Imaging of the Odontoid Process

Abstract

Introduction Plain conventional radiography of the cervical spine involves special attention to the upper most portion of the cervical spine. The attention is directed towards an anatomical feature found in this specific upper most region of the cervical spine, the odontoid process. The reason for the odontoid process being the centre of attention for radiographers and reporting radiologists when it comes to radiographic imaging of the cervical spine is due to its known susceptibility to injury. Background The open-mouth view is used as the first preferential method for demonstrating the odontoid process optimally and free of superimposition where specialised modalities are unavailable. This comment is based on the observed practice from several radiology departments in South Africa. When optimal radiographic images of the open-mouth view cannot be achieved after multiple attempts, a conventional tomogram of the odontoid process is performed as an alternative imaging technique of preference; thus, resulting in a questionable radiation dose to the patient. Aim of study This research study intended to optimise conventional radiographic imaging of the odontoid process with reference to two specific conventional radiographic imaging methods: the open-mouth view and the conventional radiographic tomogram of the odontoid process. The research study focuses on improving conventional radiography as one of the most homogeneously available radiological imaging modalities in South Africa and the African continent.

Objectives The objectives that had to be met included respectively evaluating each one of the methods for image quality, repeat rate, reasons for repeat rates and the radiation dose (effective dose) associated with the repeat rates. Establishing a checklist that would help capture all the date during the evaluations. The last objective was to use the results from each of the conventional radiographic methods that were assessed to compare their eligibility in the overall goal for optimising the conventional radiographic imaging of the odontoid process.

Methodology The research study was conducted in the Free State, Bloemfontein, at two radiology departments. Data was retrospectively collected from three X-ray machines for X-ray images of patients between the ages of 15 to 75 years. The patients included in the study had both the open-mouth view and the conventional tomogram of the odontoid process, or either one of the two methods as part of the neck examination. 385 examinations, adding up to 421 X-ray images, were evaluated for image quality, repeat rate and radiation dose (effective dose). Data was collected from the computer systems and the radiology information systems to successfully complete a checklist for each examination. The checklist was specifically designed for capturing data on image quality evaluation, repeat rates and technical exposure factors used on a dedicated software programme called PCMXC20 Monte Carlo software© for effective dose calculations.

Findings The open-mouth view had the highest repeat rate of 71.7% between the two methods with tilt being the most common error observed throughout. There was a significant difference for tilt (p=0.0019) and motion (p= 0.0001) between the two conventional radiographic methods. The upper spine received the highest effective dose mean (0.875797 mSv) for imaging of the open-mouth view, while the thyroid received the lowest effective dose mean (0.248419 mSv) for conventional tomography imaging.

Limitations Limitations to the study included the availability of patients adhering to the inclusion criteria and accessing the PCMXC20 Monte Carlo software© for the effective dose calculations. There were no previous studies precisely associated with the current research study, including any effective dose baselines that could be referenced when reporting back on the effective dose for the research study, nor studies investigating the radiation dose associated with the high repeat rates from the open-mouth view. The age of the participants was not reported on. This addition could have added more depth to the results. The checklist did not capture gender, which places a limitation for it to be used for studies aiming to report back on gender. Lastly, the data collection process was only performed by the researcher.

Conclusions Conventional tomography can be recommended as the first method of preference for optimised conventional radiographic imaging of the odontoid process in the absence of special modalities. This approach aligns with literature findings.

Recommendations A study comparing the effective dose to existing standard effective dose references for the listed tissues reflected on in the current study, can also be conducted. Furthermore, studies investigating the positioning lines that can be used for different patients to overcome tilt as a common positioning error for the open-mouth view, can be conducted. Lastly, a similar study can be done, but with a higher conventional tomography examination sample size. Although outside the context of this research study, a future study dedicated to investigating the conversion efficiency (as a contributing factor to varying exposure factors) for similar examinations, for different X-ray units with similar specifications can be explored.