Lectures are interspersed with discussion so that students can apply the theoretical concepts to practice.
The nature of the study-unit requires students enrolling into this unit to have a strong sense of self-directed learning abilities in order to be successful in completing the study unit requirements. Study-unit Aims: This study-unit enables radiographers to analyse, discuss and evaluate CT scanning protocols and be aware of their correct application in body imaging.
Radiographers use the learnt applications to address the needs of patients through good quality and efficient cost effective services. The aim of this study-unit is to allow radiographers develop knowledge and skills that will assist them to optimise CT scanning protocol variables accordingly, depending on the clinical indication as well as the innovative CT imaging techniques and advanced protocols available.
Learning Outcomes: 1. Skills By the end of the study-unit the student will be able to: - Discuss the use of various CT scanning protocols and techniques for body imaging, compare these to other modes of imaging and be able to optimise imaging protocols to address specific clinical questions. Hofer, M. Durham, D. Sutton, D. Grainger, R. The number of CT examinations has been increasingly performed in the paediatric population in the United States and European countries [ 1 — 3 ].
The growth of CT use in children is mainly due to the decrease in the time needed to complete a scan, which is currently less than 1 second, largely eliminating the need for sedation or anaesthesia to prevent the child from moving during image acquisition. Although MSCT provides excellent opportunities for imaging children, scanning techniques have become more complicated due to great variability in body size in the paediatric population, and radiologists are faced with challenges of tailoring the scanning protocols to the small-sized paediatric patients.
Increasing use of CT becomes more problematic if the ALARA as low as reasonably achievable principle is not followed and CT techniques are not adjusted according to the age and size of the child [ 4 , 5 ]. Although it offers improved diagnostic image quality, MSCT contributes more radiation dose than single-slice CT scans for various body regions.
Recently, the practice of paediatric CT has been under increasing scrutiny due to the linkage between cancer and levels of childhood radiation [ 6 ]. Efforts to reduce and minimise radiation dose associated with paediatric CT have been made with significant progress since articles appeared in the February issue of American Journal of Roentgenology [ 6 — 8 ].
Protocols for Multislice CT by Roland Bruening
These articles discussed the potential risks associated with paediatric CT imaging, and highlighted a lack of attention to the radiation risks in children by paediatric CT protocols within the radiology community, while proposing suggestions or recommendations for adjusting CT technical parameters to minimise radiation dose. It has been reported that there is a greater use of age-adjusted body CT examinations [ 9 ], however, CT radiation awareness in paediatric imaging continues to be an important topic that should be given attention by both radiologists and clinicians.
Although there is still adequate room for improvement, the change signals a dramatic and positive direction compared with the near-universal lack of such practices as early as [ 8 ]. CT dose reduction in paediatric imaging requires a combination of different approaches or strategies. These include optimisation of scanning protocols for children according to age- or weight-based adjustments, justification of paediatric CT use in paediatric clinics and emergency departments, decrease of unnecessary examinations, development of automatic exposure control devices by manufacturers, and user education for paediatricians and radiological technologists.
Adjustments of CT scanning protocols based on age and weight have been reported to be convenient and effective in clinical practice, according to early studies [ 11 — 13 ]. However, to our knowledge, very few reports are available in Saudi Arabia with regard to the investigation of paediatric CT scanning protocols.
There are no standardised procedures for paediatric CT imaging across hospitals in Saudi Arabia, as each hospital has its own specific procedures, which are not necessarily optimised in terms of dose reduction. The purpose of this study was to assess the paediatric CT practice, analyse CT scanning parameters used in routine head, chest and abdomen imaging, and investigate whether the CT protocols are appropriately adjusted according to the age of the children in major hospitals in Jeddah, Saudi Arabia.
It is expected that the study results could be used by radiologists and medical imaging technologists to modify their existing practice and serve as a basis for optimisation of paediatric CT imaging. The study population consisted of all paediatric patients seen at three major public hospitals in Jeddah, Saudi Arabia from May to May MSCT examination records were retrospectively reviewed for paediatric patients undergoing head, chest and abdomen MSCT scans during this one-year period. Inclusion criteria included patients 16 years old or younger; routine head CT and head trauma scans; routine chest CT; routine abdominal CT and abdominal trauma scans.
These parameters included tube current mA , tube kilovoltage and slice thickness. All CT scans were performed with slice CT scanners in these three hospitals. The scanning parameters for these CT scanners were variable, depending on the age of the patients, and details are summarised in Table 1. A spiral CT scanning mode was used on both types of CT scanners for acquisition of better images with minimal artefacts. For routine and trauma paediatric CT protocols, the slice thickness was 4. Based on the categories by different ages, the patients were categorised into the following age groups: less than 4 years, 5—8 years, 9—12 years and 13—16 years.
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A total of patient records comprising a combination of head, chest and abdomen CT scans among the three hospitals were assessed. The number of abdominal and chest CT scans was and , respectively. Figure 1 shows the distribution of CT scans corresponding to the anatomic regions at these three hospitals. Distribution of the number of CT scans corresponding to different anatomic regions among the three hospitals.
Tables 2 — 5 show the number of CT scans with use of different mA ranges performed at each hospital corresponding to different age groups and anatomic locations. As shown in the tables, age-based adjusted CT protocols were used in most of the scans. The trend is to use a higher tube current setting with increasing age and slightly higher current setting for head and abdominal CT than for chest CT.
None of the hospitals used more than mA for these CT scans. In children 5—8 years old, the most commonly used tube currents were between — mA and — mA. When scanning the children 9—12 years old, increased tube current was used in most of the CT scans in Hospital A and B, while in Hospital C, a low tube current was still applied. In contrast, a tube current of 50—99 mA was used in all of the head CT scans, and tube currents of — mA and — mA were used in chest and abdomen CT scans in hospital C.
In Hospital B, there is an unknown tube current of routine head CT in scans. A scan delay of 25—30 sec and 50—60 sec was used in the chest and abdomen CT scans, while in head CT scans, the scan delay was shown to be dependent on the patients. Figures 2 — 4 show the number of CT scans in each age group corresponding to different tube current ranges in hospital A, B and C, while figure 5 is the distribution of CT scans in each age group among all of the three hospitals.
Protocols for Multislice CT 4 and 16-row Applications
Tube current settings used for paediatric head, chest and abdominal CT scans in hospital A. High tube current is used with increasing age of patients, with a tube current of more than mA being applied in patients older than 9 years old. Tube current settings used for paediatric head, chest and abdominal CT scans in hospital C. High tube current is used with increasing age of patients, with a tube current of more than mA being applied only in patients older than 13 years old.
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Tube current settings used for paediatric head, chest and abdominal CT scans among three hospitals. High tube current is used with increasing age of patients, however, a tube current of — mA was still used in a number of CT scans in the patients less than 5 years old. Tube current settings used for paediatric head, chest and abdominal CT scans in hospital B. A high tube current of — mA was used in the age group of 0—4 years old, although a tube current of more than mA was only applied in the patients older than 9 years old. This study was designed to investigate the current practice of MSCT for routine head and body scans in paediatric patients among three public hospitals in Saudi Arabia.
There are three major findings arising from this study, which are considered valuable from a clinical perspective. Second, variable scanning protocols are used in different age groups, in particular, a high tube current is applied in paediatric patients from younger age groups. This reflects the fact that reduction in radiation dose and radiation protection needs to be increased in clinical practice, especially when scanning paediatric patients.
Third, patients might be exposed to high radiation dose due to use of fixed scan delay in the contrast-enhanced CT scans, thus, optimisation of paediatric CT protocols is necessary in these hospitals. Radiation dose in children from CT has increased significantly since the imaging modality has progressed from single-slice to helical CT and multislice CT examinations that are widely available today. Children are at greater risk than adults from a given dose of radiation, because they are inherently more radiosensitive to radiation exposure due to the increased number of dividing cells in growing children and the higher remaining years of life ahead of them, which indicates that they have more time to develop a radiation-induced cancer [ 11 ].
It is estimated that children are 10 times more sensitive to the effects of radiation than middle-aged adults [ 12 , 13 ].
Brenner et al. Their estimates suggested that the risk of dying from cancer is approximately 1 in for a single abdominal CT examination and 1 in for a head CT examination if the scan is performed in a 1-year-old child. However, it is necessary to point out that these estimates were based on the assumption that the same CT scanning protocols used in adult examinations were applied in children without adjustments.
Thus, the risk would be lower if paediatric CT protocols were adopted and the paediatricians were aware of applying specific protocols in imaging children. Different approaches can be used to optimise the tube current settings [ 2 , 3 , 17 — 19 ]. Adjustments of CT scanning protocols based on weight and age are found to be convenient approaches for dose reduction in clinical practice, according to early studies [ 17 , 18 ]. For head CT scans, tube current should be modified according to different age groups because the attenuation in the head largely depends on the thickness of the skull, which changes with age [ 18 ].
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Suess and Chen suggested that after the age of 6 years, adult tube current settings can be used since the size of the head and the ossification of the skull would have almost reached the adult levels [ 18 ]. The results from this study showed that age-based scanning is practised in two out of three hospitals, while in another hospital hospital B , a tube current of more than mA was still used for both routine and trauma head CT scans in children between 0 and 4 years old.
A tube current of more than mA was used in the age group of 9—12 years for head, chest and abdomen CT scans, and more than mA for all of these body regions in children more than 13 years old.
This is much higher than the recommended ranges of 91— mA for cranial and 76—90 mA for thoracic, abdominal and pelvic CT examinations by Shah et al. Thus, optimisation of these paediatric CT protocols is necessary for dose reduction. This indicates the possibility of exposure of the paediatric patients to higher radiation dose. Adjustment of tube current is not only based on the age or the weight of patients, it is also controlled by using automatic current modulation techniques to reduce radiation dose in paediatric CT examination without affecting diagnostic image quality [ 21 ].
This helps to reduce radiation exposure in all types of patients and body regions. Clinical studies have confirmed very efficient dose reduction based on online tube current modulation [ 22 — 26 ].