Abdominal spiral CT in children: which radiation exposure is required?

Greek dose reference levels in pediatric pelvis computed tomography examinations

The fact that children do undergo computed tomography (CT) examinations similar to those for adults adults has been a research issue, especially since the former are exposed to greater risk levels (developing stochastic late effects, such as cancer) due to their increased radiosensitivity compared to the latter. In a previous research paper (), the values of dose levels were recorded, analyzed, and compared with the reference values for groups of 0, 1, 5 and 10 y-old children for the regions of head, chest, and abdomen. In this paper, the same age group has been considered for measuring dose levels of the pelvic region. Scanning the pelvic region has been one of the most important CT examination procedures, in which unfortunately part of the lower abdomen region is included without adapting any pediatric protocols. Furthermore, the study determines whether the adjustment of the scanning parameters results in any possible reduction in the radiation dose levels to which the patient is being exposed during the examination. The present work also includes the Greek reference levels for the pelvic CT examination for the 5- and 10-y-old children that have been used for comparison against the European ones.

Effective dose variation in pediatric computed tomography: dose reference levels in Greece

Computed tomography provides high-resolution imaging of the human body. However, it contributes mainly to the doses on the population. Additionally, the fact that children are two to three times more sensitive to the x rays compared to the adults results in the increased need of taking action for the reduction of the dose regarding the computed tomography examinations. The first part of this paper presents the results of an investigation on the variation of doses to children while the second part compares those results with the European standards. This project took place in twelve hospitals distributed throughout the country. The weighted computed dose-index and the dose length product were calculated for four different age-categories (namely 0, 1, 5 and 10-year-old) and for the three most often examinations (brain, thorax and abdomen). Effective dose values were estimated using coefficients and patients' data. The measurements showed that only a few hospitals are taking into account the protocols regarding the age of the children. As a result, many patients receive high doses without this being necessary. Thus, reducing dose methods should be adapted in order to improve the optimization of this high dose modality.

The relevance of image quality indices for dose optimization in abdominal multi-detector row CT in children: experimental assessment with pediatric phantoms

This study assessed and compared various image quality indices in order to manage the dose of pediatric abdominal MDCT protocols and to provide guidance on dose reduction. PMMA phantoms representing average body diameters at birth, 1 year, 5 years, 10 years and 15 years of age were scanned in a four-channel MDCT with a standard pediatric abdominal CT protocol. Image noise (SD, standard deviation of CT number), noise derivative (ND, derivative of the function of noise with respect to dose) and contrast-to-noise ratio (CNR) were measured. The 'relative' low-contrast detectability (rLCD) was introduced as a new quantity to adjust LCD to the various phantom diameters on the basis of the LCD(1%) assessed in a Catphan phantom and a constant central absorbed dose. The required variations of CTDIvol(16) with respect to phantom size were analyzed in order to maintain each image quality index constant. The use of a fixed SD or CNR level leads to major dose ratios between extreme patient sizes (factor 22.7 to 44 for SD, 31.7 to 51.5 for CNR(2.8%)), whereas fixed ND and rLCD result in acceptable dose ratios ranging between factors of 2.9 and 3.9 between extreme phantom diameters. For a 5-9 mm rLCD1(%), adjusted ND values range between -0.84 and -0.11 HU mGy(-1). Our data provide guidance on dose reduction on the basis of patient dimensions and the required rLCD (e.g., to get a constant 7 mm rLCD(1%) for abdominal diameters of 10, 13, 16, 20 and 25 cm, tube current-time product should be adjusted in order to obtain CTDIvol(16) values of 6.2, 7.2, 8.8, 11.6 and 17.7 mGy, respectively).

Dose reduction in paediatric MDCT: general principles

The number of multi-detector array computed tomography (MDCT) examinations performed per annum continues to increase in both the adult and paediatric populations. Estimates from 2003 suggested that CT contributed 17% of a radiology department's workload, yet was responsible for up to 75% of the collective population dose from medical radiation. The effective doses for some CT examinations today overlap with those argued to have an increased risk of cancer. This is especially pertinent for paediatric CT, as children are more radiosensitive than adults (and girls more radiosensitive than boys). In addition, children have a longer life ahead of them, in which radiation induced cancers may become manifest. Radiologists must be aware of these facts and practise the ALARA (as low as is reasonably achievable) principle, when it comes to deciding CT protocols and parameters.

Management of patient dose and image noise in routine pediatric CT abdominal examinations

The aim was to propose a strategy for finding reasonable compromises between image noise and dose as a function of patient weight. Weighted CT dose index (CTDI(w)) was measured on a multidetector-row CT unit using CTDI test objects of 16, 24 and 32 cm in diameter at 80, 100, 120 and 140 kV. These test objects were then scanned in helical mode using a wide range of tube currents and voltages with a reconstructed slice thickness of 5 mm. For each set of acquisition parameter image noise was measured and the Rose model observer was used to test two strategies for proposing a reasonable compromise between dose and low-contrast detection performance: (1) the use of a unique noise level for all test object diameters, and (2) the use of a unique dose efficacy level defined as the noise reduction per unit dose. Published data were used to define four weight classes and an acquisition protocol was proposed for each class. The protocols have been applied in clinical routine for more than one year. CTDI(vol) values of 6.7, 9.4, 15.9 and 24.5 mGy were proposed for the following weight classes: 2.5-5, 5-15, 15-30 and 30-50 kg with image noise levels in the range of 10-15 HU. The proposed method allows patient dose and image noise to be controlled in such a way that dose reduction does not impair the detection of low-contrast lesions. The proposed values correspond to high- quality images and can be reduced if only high-contrast organs are assessed.

Common tasks and problems in paediatric trauma radiology

Scope of this article is to give practical hints for the most common, typical and important topics of trauma radiology in children to those radiologists who are not exclusively occupied with paediatric imaging. Due to the increased radiation sensitivity of children compared with adults balancing radiation protection and necessary image quality is of utmost importance. Outlines for this optimisation process are given. Especially in imaging of the extremities perhaps the greatest difficulties are posed by the dynamically changing face of the immature, growing, only partially ossified skeleton. Lack of experience must be compensated by meticulous comparison with the normal skeletal development as shown in standard textbooks, and by knowledge of the radiological image of the developmental variants. Besides general remarks about paediatric trauma radiology, some important topics are discussed into more detail. Especially the elbow joint poses a challenge for those less experienced with its radiological appearance in children. More than in adults, ultrasound should remain the primary imaging modality of choice especially in the assessment of abdominal trauma, and CT be tailored to radiological and clinical findings. Imaging and diagnosis of non-accidental injury (NAI) may be a less common task for the general radiologist, however, the severe social implications of physical child abuse mandate a basic knowledge about the radiological symptoms and the imaging management of this problem for all physicians occupied with paediatric radiology.