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Computer tomography dose index for head CT in northern Nigeria
Author(s)
Garba, Idris
Date Issued
2014
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
Aim: The aim of this study was to record the values of CTDIw and DLP displayed on
the Computed Tomography (CT) scanner monitors of patients undergoing CT
examinations of the head as Diagnostic Reference Levels (DRL) for dose
optimisation in Northern Nigeria.
Background: A brain CT scan is the most common CT examination performed, and
this modality is recognized as delivering a high dose. CT, therefore, contributes
significantly to the total collective effective dose to the population. Elimination of
unnecessary or unproductive radiation exposure is necessary. To achieve this,
practitioners must adhere to the principles of the justification of practices, and
optimisation of radiation protection. Furthermore, the development of DRLs for the
local context is advised. These reference doses are a guide to the expected exposure
dose from a procedure and are useful as an investigation tool to identify incidences
where patient doses are unusually high.
Methodology: The study was conducted in three radiology departments with CT
centres in Northern Nigeria. Data was collected, using a purposive sampling
technique, from 60 consenting adult participants (weighing 70 ±3 kg) that had brain
CT scans on seventh generations 4&16-slice GE and 16-slice Philips CT scanners.
Prior to commencement of the study the CT scanners were certified by the medical
physicists. For each brain scan, patient information, exposure factors, weighted
computed tomography dose index (CTDIw), volume computed tomography dose
index (CTDIvol) and dose length product (DLP) values were recorded. The data were
analysed using SPSS version (16) statistical software. The mean, standard deviation
and third quartile values of the CTDIw and DLP were calculated. An inter-comparison
of the measured doses from the three research sites was conducted. A combined dose
for the three centres was calculated, and compared with the reported data from the
international communities where there are established DRLs.
Results: The mean CTDIw and DLP values were: centre A (88 mGy and 713
mGy.cm), centre B (68 mGy and 1098 mGy.cm), and centre C (70 mGy and 59
mGy.cm). Comparison of CTDIw and DLP for the scanners of the same
manufacturers showed statistically significant differences (p=0.003) and (p=0.03)
respectively. In the case of the scanners of a different model but the same number of
slices, the comparison of DLP was statistically significant (p=0.005) while no
significant difference was noted in the measured CTDIw. Third quartile values of the
cumulative doses of CTDIw and DLP, for Northern Nigeria were determined as 77
mGy and 985 mGy.cm respectively.
Conclusion: The study has established Local DRLs (LDRLs) which are significantly
higher than most of the reported data in the literature. Also dose variation between
centres was noted. Optimization is thus recommended.
Keywords: Head Imaging, Radiation Dose, Dose optimization, Computed
Tomography, Local Diagnostic Reference Levels, Radiation Protection
the Computed Tomography (CT) scanner monitors of patients undergoing CT
examinations of the head as Diagnostic Reference Levels (DRL) for dose
optimisation in Northern Nigeria.
Background: A brain CT scan is the most common CT examination performed, and
this modality is recognized as delivering a high dose. CT, therefore, contributes
significantly to the total collective effective dose to the population. Elimination of
unnecessary or unproductive radiation exposure is necessary. To achieve this,
practitioners must adhere to the principles of the justification of practices, and
optimisation of radiation protection. Furthermore, the development of DRLs for the
local context is advised. These reference doses are a guide to the expected exposure
dose from a procedure and are useful as an investigation tool to identify incidences
where patient doses are unusually high.
Methodology: The study was conducted in three radiology departments with CT
centres in Northern Nigeria. Data was collected, using a purposive sampling
technique, from 60 consenting adult participants (weighing 70 ±3 kg) that had brain
CT scans on seventh generations 4&16-slice GE and 16-slice Philips CT scanners.
Prior to commencement of the study the CT scanners were certified by the medical
physicists. For each brain scan, patient information, exposure factors, weighted
computed tomography dose index (CTDIw), volume computed tomography dose
index (CTDIvol) and dose length product (DLP) values were recorded. The data were
analysed using SPSS version (16) statistical software. The mean, standard deviation
and third quartile values of the CTDIw and DLP were calculated. An inter-comparison
of the measured doses from the three research sites was conducted. A combined dose
for the three centres was calculated, and compared with the reported data from the
international communities where there are established DRLs.
Results: The mean CTDIw and DLP values were: centre A (88 mGy and 713
mGy.cm), centre B (68 mGy and 1098 mGy.cm), and centre C (70 mGy and 59
mGy.cm). Comparison of CTDIw and DLP for the scanners of the same
manufacturers showed statistically significant differences (p=0.003) and (p=0.03)
respectively. In the case of the scanners of a different model but the same number of
slices, the comparison of DLP was statistically significant (p=0.005) while no
significant difference was noted in the measured CTDIw. Third quartile values of the
cumulative doses of CTDIw and DLP, for Northern Nigeria were determined as 77
mGy and 985 mGy.cm respectively.
Conclusion: The study has established Local DRLs (LDRLs) which are significantly
higher than most of the reported data in the literature. Also dose variation between
centres was noted. Optimization is thus recommended.
Keywords: Head Imaging, Radiation Dose, Dose optimization, Computed
Tomography, Local Diagnostic Reference Levels, Radiation Protection
Additional information
Thesis (MTech (Diagnostic Radiography))--Cape Peninsula University of Technology, 2014
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