Head computed tomography protocol audit and correction in two tertiary health institutions in Anambra State of Nigeria
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Abstract
Background and Objective: The optimization of patient protection in computed tomography (CT) requires the application of examination-specific protocols to ensure that the dose to each patient is as low as reasonably achievable. Appropriateness of a protocol reflects in the output of the volume CT dose index (CTDIvol) and dose-length product (DLP). This work aims to review and correct the likely weaknesses in default head CT protocols as a quality control measure.
Materials and Methods: Departmental and Ethical Committee approvals were obtained. This retrospective study was undertaken between March and April 2016. The 75th percentile of the CTDIvol and DLP was calculated for 50 consecutive patients of both genders who were ≥18 years of age. On the CT console, radiographer (s)’ manipulation of each of the ten common components of default protocols was scrutinized and compared with predetermined standard values from literature. Observed deviations necessitated appropriate interventional measures. A second calculation of the 75th percentile of CTDIvol and DLP was done for another group of 50 patients. Both pre- and post-interventional values were compared with the 60 mGy (CTDIvol) and 1050 mGy-cm (DLP) recommended by the European Commission.
Results: The pre - interventional CTDIvol and DLP outputs were 65 mGy/1634 mGy-cm (Center A) and 86 mGy/1786 mGy-cm (Center B) whereas the post - interventional values were 58 mGy/986 mGy-cm (Center A) and 60 mGy/1030 mGy-cm (Center B), respectively. Weaknesses noted in protocols were excessive scan range (≥15 cm), <1 helical pitch, >1 s gantry rotation time, absence of gap, erratic manual mA manipulation, and neglect of prospective dose chart. Some posteroanterior scanograms were also wrongly acquired at an azimuth of 0° (anteroposterior).
Conclusion: CT dose output in our locality could be compared to the values of the European Commission if meticulous and regular dose audit and correction is implemented.
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