Radiation dose measurement of abdominal CT and categorisation according to referral origin and design of CT study in adult patients

Abstract

INTRODUCTION: Abdominal CT scan remains the biggest culprit of man-made radiation affecting humans. With the increase in medical litigation and evolvement of CT technology, there has also been an increased utilisation of CT scanning. It is the radiologist’s responsibility to keep radiation to patients As Low As Reasonably Achievable (ALARA) while still obtaining an image adequate enough for correct interpretation. To do this effectively, radiologists and referring clinicians need to know the doses received by patients during CT procedures, and if dosages are above recommended acceptable reference levels, measures need to be taken to reduce the potentially detrimental dosages at the health facility.

AIM: The aim of this study was to determine adult radiation dose measurements from abdominal CT scans in diagnostic radiology at Helen Joseph and Rahima Moosa Mother and Child Hospital Complex and to compare our results to internationally recommended Diagnostic Reference Levels (DRLs) for abdominal CT scans. The radiation dosages between the number of abdominal CT scan phases performed, the referral origin and the hospitalisation status of the patient was also compared.

METHOD: Records of adult patients who underwent abdominal CT scans were obtained from the radiology department patient registration books. The department of origin of the patient and whether the patient was an inpatient or outpatient, as well as the phases of the scans performed, the dosimetry (DLP and CTDIvol) values were all retrieved from the patient’s archived scan which is stored in the department of radiology.

RESULTS: Using the European Commission guidelines for DLP and CTDIvol as our reference levels, which applies to single phase scans, we found that adult patients who had had CT abdominal scans at Helen Joseph and Rahima Moosa Mother and Child Hospital Complex received radiation doses which were below the recommended diagnostic reference levels. When assessing the overall radiation doses, regardless of the number of phases done per patient, we found the the radiation doses received by patients is dependent on the number of abdominal CT scan phases performed, with a linear increase in the DLP and CTDIvol values as the number of phases increases. This was further confirmed by the coefficient of linear 6 regression. Radiation doses received by patients differed significantly depending on the referral origin with hepatobiliary patients receiving the overall highest total radiation dose. Analysis of single phase scans demonstrated the urology patients receiving the least radiation dose. Inpatients were found to receive higher radiation doses than outpatients. This difference, however, lacked statistical significance.

CONCLUSIONS: Our study emphasises the continuous need for periodic radiation dose audits within our institution and rigid implementation of CT dose optimisation techniques in an attempt to further curb the detrimental stochastic and deterministic biological effects of ionising radiation.