CT radiation dose optimization and reduction for routine head, chest and abdominal CT examination

Abstract

The purpose of this study is to find an optimization approach to minimize the absorbed dose to adult patients undergoing CT examination, while maintain the diagnostic image quality. A single detector CT was considered, to represent typical practice in King Hamad University Hospital. We included 626 patients in this study and investigated radiation dose for three anatomical regions, head, chest and abdomen and pelvis. For each type of CT examination, two groups of patients were considered. 383 patients in Group I: were imaged according to the protocols set by the manufacturer. Group II: 243 patients were imaged according to the protocols set by our team after optimization. We were able to adjust the adjustable factors such as noise index, scan time, pitch, rotation time and slice thickness. For each examination the weighted volume CT dose index (CTDIvol) and dose length product (DLP) were recorded and noise is measured. Each study was also reviewed for image quality. Measured (CTDIvol, DLP) were compared to international reference levels. For Group I, the CTDIvol and DLP values were higher than the reference levels. After Dose optimization the CTDIvol and DLP values were significantly reduced to have lower values than the reference levels. The results of our study showed that the CTDIvol and DLP values taken from images done using the protocols set by the Ct machine developers are higher than the reference levels which indicate that manufacturers are focusing their efforts toward improving image quality rather than the minimizing the dose that can be given to the patient. Correspondence to: Lama Sakhnini, Department of Physics, College of Science, University of Bahrain, Sakhir, Kingdom of Bahrain; E-mail: l_ sakhnini@yahoo.com Received: November 1, 2017; Accepted: December 12, 2017; Published: December 15, 2017 Introduction The use of helical, multislice CT (MSCT) is rapidly growing due to technological improvements in the modern machines. Advances in CT imaging techniques have resulted in a significant increase in the frequency of CT examinations in both adult and children, replacing more and more radiographic examinations. However, CT can be responsible for the increase of carcinogenesis [1-4]. But we have to accept the fact that with the vast improvement of technology, patients benefited from a quicker and more accurate diagnosis and precise anatomic information for planning therapeutic procedures. This lead to a substantial increase in the collective dose, as reported by international organizations (ICRP 2000 and United Nations Scientific Committee 2000) [5]. In spite of this constructive contributions of CT to modern healthcare, attention must also be given to the health risk associated with the ionizing radiation received during a CT exam. Because of this potential radiation risk from this increased use of CT makes it important that CT doses be kept as low as reasonably achievable. However, modern CT scanners have a wide variety of exposure factors and involve techniques that allow dose optimization to the patient [6-9]. Guidelines to optimize the protection of patients during CT procedures have been provided by various international organizations [10-13]. All implemented guidelines include reference doses that are defined as diagnostic reference levels (DRLs) or guidance levels. These guidelines assist in the optimization and reduction of patient protection and allow comparisons between the different CT scanners and techniques. The dose parameters suggested in the guidelines are the volume CT dose index (CTDIvol) and dose length product (DLP) for the entire examination. Although there is still adequate room for improvement, CT dose reduction requires a combination of different approaches or strategies. These include optimization of scanning protocols according to ageor weight-based adjustments, justification of CT use by referring physicians and emergency departments, decrease of unnecessary examinations, development of better exposure protocols by manufacturers, and better training and education for radiological technologists. However, to our knowledge, no reports are available in Bahrain with regard to the investigation of CT scanning protocols. There are no standardized procedures for CT imaging across hospitals in Bahrain, as each hospital has its own specific protocol, which are not necessarily optimized in terms of dose reduction. The purpose of this study was to assess the adult CT practice, analyze CT scanning parameters used in routine head, chest and abdomen and pelvis imaging in the radiology department at King Hamad University Hospital. Moreover, our practical goal was to find an optimization approach to minimize the absorbed dose to adult patients undergoing CT examination, while maintain the diagnostic image quality. We hope that the results of this study could be used by radiologists and medical imaging technologists to modify their existing practice and serve as one of the basis for optimization of CT imaging. Additionally, the medical community in Bahrain needs to better educate the public to the risks and benefits associated with CT, such that they can make conscience decisions based on scientific facts regarding their healthcare. Materials and methods Patient examinations In this study, medical images taken by Optima CT660 system (GE Health Care, WI, USA) are considered. Adult head, chest, and Sakhnini L (2017) CT radiation dose optimization and reduction for routine head, chest and abdominal CT examination Volume 2(1): 2-4 Radiol Diagn Imaging, 2017 doi: 10.15761/RDI.1000120 abdominal and pelvis CT examinations were chosen for the evaluations because they are most common procedures performed in the radiology department. The hospital ethics committees of King Hamad University Hospital approved the study protocol.