Radiation exposure in multi-slice versus single-slice spiral CT: results of a nationwide survey

Multi-slice (MS) technology increases the efficacy of CT procedures and offers new promising applications. The expanding use of MSCT, however, may result in an increase in both frequency of procedures and levels of patient exposure. It was, therefore, the aim of this study to gain an overview of MSCT examinations conducted in Germany in 2001. All MSCT facilities were requested to provide information about 14 standard examinations with respect to scan parameters and frequency. Based on this data, dosimetric quantities were estimated using an experimentally validated formalism. Results are compared with those of a previous survey for single-slice (SS) spiral CT scanners. According to the data provided for 39 dual- and 73 quad-slice systems, the average annual number of patients examined at MSCT is markedly higher than that examined at SSCT scanners (5500 vs 3500). The average effective dose to patients was changed from 7.4 mSv at single-slice to 5.5 mSv and 8.1 mSv at dual- and quad-slice scanners, respectively. There is a considerable potential for dose reduction at quad-slice systems by an optimisation of scan protocols and better education of the personnel. To avoid an increase in the collective effective dose from CT procedures, a clear medical justification is required in each case.     

Validation of a Monte Carlo tool for patient-specific dose simulations in multi-slice computed tomography

Estimating the dose delivered to the patient in X-ray computed tomography (CT) examinations is not a trivial task. Monte Carlo (MC) methods appear to be the method of choice to assess the 3D dose distribution. The purpose of this work was to extend an existing MC-based tool to account for arbitrary scanners and scan protocols such as multi-slice CT (MSCT) scanners and to validate the tool in homogeneous and heterogeneous phantoms. The tool was validated by measurements on MSCT scanners for different scan protocols under known conditions. Quantitative CT Dose Index (CTDI) measurements were performed in cylindrical CTDI phantoms and in anthropomorphic thorax phantoms of various sizes; dose profiles were measured with thermoluminescent dosimeters (TLD) in the CTDI phantoms and compared with the computed dose profiles. The in-plane dose distributions were simulated and compared with TLD measurements in an Alderson-Rando phantom. The calculated dose values were generally within 10% of measurements for all phantoms and all investigated conditions. Three-dimensional dose distributions can be accurately calculated with the MC tool for arbitrary scanners and protocols including tube current modulation schemes. The use of the tool has meanwhile also been extended to further scanners and to flat-detector CT.     

Establishment of CT diagnostic reference levels in Ireland

Objective To propose Irish CT diagnostic reference levels (DRLs) by collecting radiation doses for the most commonly performed CT examinations. Methods A pilot study investigated the most frequent CT examinations. 40 CT sites were then asked to complete a survey booklet to allow the recording of CT parameters for each of 9 CT examinations during a 12-week period. Dose data [CT volume index (CTDI(vol)) and dose-length product (DLP)] on a minimum of 10 average-sized patients in each category were recorded to calculate a mean site CTDI(vol) and DLP value. The rounded 75th percentile was used to calculate a DRL for each site and the country by compiling all results. Results are compared with international DRL data. Results Data were collected for 3305 patients. 30 sites responded with data for 34 scanners, representing 54% of the national total. All equipment had multislice capability (2-128 slices). DRLs are proposed using CTDI(vol) (mGy) and DLP (mGy cm) for CT head (66/58 and 940, respectively), sinuses (16 and 210, respectively), cervical spine (19 and 420, respectively), thorax (9/11 and 390, respectively), high resolution CT (7 and 280, respectively), CT pulmonary angiography (13 and 430, respectively), multiphase abdomen (13 and 1120, respectively), routine abdomen/pelvis (12 and 600, respectively) and trunk examinations (10/12 and 850, respectively). These values are lower than current DRLs and comparable to other international studies. Wide variations in mean doses are noted across sites. Conclusions Baseline figures for Irish CT DRLs are provided on the most frequently performed CT examinations. The variations in dose between CT departments as well as between identical scanners suggest a large potential for optimisation of examinations.     

16-slice CT: achievable effective doses of common protocols in comparison with recent CT dose surveys

The aim of the study was to investigate achievable dose levels in 16-slice CT by evaluating CT dose indices (CTDI) and effective doses of dose-optimized protocols compared with 4-slice dose surveys. Normalized CTDI free in air and in 16 cm and 32 cm diameter phantoms were measured on four different 16-slice CT scanners in the Netherlands. All collimation and tube potential settings were analysed. Volume CTDI was calculated for adult protocols for brain, chest, pulmonary angiography (CTPA), abdomen and biphasic liver CT. Effective doses were calculated first using volume CTDI with conversion factors and second from CTDIair values using the ImPACT dose calculator. Average results of the 16-slice scanners were correlated to results of dose surveys with predominantly 4-slice scanners. Statistical analysis was done with Student t-tests with a Bonferroni correction; therefore p < 0.017 was significant. The results of CTDIair and weighted CTDI were documented for all scanners. Effective doses averaged over four scanners for brain, chest, CTPA, abdomen and biphasic liver protocols were 1.9+/-0.4, 3.8+/-0.4, 3.0+/-0.2, 7.2+/-0.9 and 10.2+/-1.3 mSv, respectively. Compared with dose surveys achievable effective doses were equal (p = 0.069) to significantly lower (p < 0.017) for chest and abdomen protocols. For 16-slice spiral brain CT there was a trend of equal doses compared with sequential brain CT in the dose surveys. Thus, with dose-optimized protocols 16-slice CT can achieve equal to lower effective doses in examinations of the chest and abdomen compared with 4-slice CT, while doses can remain stable in the brain.     

Variations in radiation dose between the same model of multislice CT scanner at different hospitals

The variation in exposure factors and patient dose, between seven centres using identical multislice CT scanners, was investigated for six standard examinations. Dose values were compared with each other and the relevant diagnostic reference level (DRL) for each examination. The range in weighted CT dose index (CTDI(w)) values between the seven centres was small for abdominal scans and head scans. For other scans however, such as functional endoscopic sinonasal surgery (FESS) the variations in CTDI(w) were as high as a factor of seven between the lowest and the highest values. At one centre a program of dose optimization had been undertaken and this centre had CTDI(w) values ranging from 3% to 64% lower than the average value for the seven centres. This demonstrates that significant dose reduction can be achieved through close collaboration between medical physicists, radiologists and radiographers.     

Effect of multislice scanners on patient dose from routine CT examinations in East Anglia

As part of the dose optimization process, the Ionising Radiation (Medical Exposure) Regulations 2000 include requirements relating to the assessment of patient dose, and the setting and subsequent review of diagnostic reference levels. In East Anglia, audits of effective dose in CT have been carried out in 1996, 1999 and 2002. In the 2002 audit, nine of the 14 scanners assessed had been replaced since the previous audit. Eight of the new scanners were multislice scanners, acquiring up to 16 slices in a single rotation. The objective of the 2002 audit was to investigate the effect of the introduction of these multislice scanners on patient doses from routine CT examinations. Exposure parameters were collected for 10 different types of routine CT examination. In excess of 550 sets of patient data were obtained. For each of these, effective doses were calculated using the results of Monte Carlo simulations published by the National Radiological Protection Board. Averaged across all 10 examinations, regional mean effective doses are 34% higher than in 1999. The multislice scanners in the region give, on average, 35% more effective dose than the single-slice scanners. The effect of collimation in multislice scanners makes these effective dose differences most notable for examinations that use narrow slice widths. Further optimization of exposures on multislice scanners has the potential to reduce the differences observed between single-slice and multislice doses. However, when taken in combination with the increased use of CT in many hospitals, the effective dose increases observed are likely to result in a significant increase in the already substantial collective radiation dose from CT.     

多层面CT和单层面CT对颅后窝结构显示的对比评价

对多层面CT和单层面CT在颅后窝产生的伪影情况进行分析。材料和方法;用2例头颅标本分别行平行于眶耳线平面的多层面CT 和单层面CT扫描,扫描范围包括从枕骨大孔到颞骨岩部上缘的整个颅后窝区。单层面CT分别采用120kV和135kV两种电压,多层面CT采用120kV ,其他扫描参数均相同。所有图像质量均由三位有经验的放射医师采用盲法进行独立评分,并按图像质量予以记分3、2、1分（3分为伪影很少,2分为有部分伪影,1分伪影较重）。统计结果采用SPSS软件分析。结果：将三位放射医师的评分结果进行统计学处理并分析。结果显示：在相同的扫描条件下,多层面CT图像的质量明显优于单层面CT（p＜0．01）。多层面CT中,3分43．3％,2分50％,1分6．7％,单层面CT的120kV中3分26．7％,2分43．3％,1分30％;135kV中3分30％,2分46．7％,1分23．3％。在单层面螺旋CT120KV和135KV之间图像质量无明显差异（P＞0．05）。结论：多层面CT能明显减少颅后窝伪影,提供优质的CT图像。     

Effective doses in standard protocols for multi-slice CT scanning

The purpose of this study was to assess the radiation exposure of patients in several standard protocols in multi-slice CT (MSCT). Scanning protocols for neck, chest, abdomen, and spine were examined on a Somatom Plus 4 Volume Zoom MSCT (Siemens, Erlangen, Germany) with changing slice collimation (4×1, 4×2.5, and 4×5 mm), and pitch factors (1, 1.5, and 2). Effective doses were calculated from LiF–TLD measurements at several organ sites using an Alderson-Rando phantom and compared with calculations using the weighted CTDI. Effective dose for MSCT of the neck was 2.8 mSv. For different protocols for MSCT of the chest, 7.5–12.9 mSv were found. In abdominal MSCT protocols, effective dose varied between 12.4 and 16.1 mSv. The MSCT of the spine may lead to 12 mSv. An excellent correlation between the effective dose as determined by LiF–TLD and the calculated effective dose using the weighted CTDI could be demonstrated; however, a difference of up to 30% (mean 14.3%) was noted. Standard protocols for MSCT as measured in this study showed effective doses of up to16 mSv. Phantom measurement data show a good correlation to estimations using the weighted CTDI. Electronic Publication     

A contribution to the establishment of diagnostic reference levels in CT

CT has become the major source of population exposure to diagnostic X-rays. CT dose index (CTDI) and dose-length product (DLP) have been proposed as the appropriate dose quantities for the establishment of diagnostic reference levels for optimizing patient exposure. Dose measurements on 27 CT scanners in Northern Greece involving six routine CT examinations have been performed in order to compare their performance with the currently proposed European reference dose values and to produce a preliminary set of data for the establishment of local diagnostic reference levels. All measurements were performed using a pencil shaped ionization chamber introduced into polymethyl methacrylate cylindrical head and body phantoms. The results revealed significant discrepancies in dose values among the CT scanners, which can be mainly attributed to variations in the examination protocols and the different kinds of scanners. Significant overdosing compared with the European reference levels has not been observed, with the exception of the routine head examination, where 47% of the scanners exceeded the corresponding CTDI(w) value. CT scans in the trunk region result in the higher effective doses, which can reach estimated maximal values of the order of 15 mSv.     

Ultra-low-dose coronary artery calcium screening using multislice CT with retrospective ECG gating

The aim of this study was to reduce radiation exposure in multislice CT (MSCT) coronary artery calcium screening using different tube settings, and to determinate its impact on the detection and quantification of coronary artery calcification. Forty-eight patients underwent routine MSCT coronary artery calcium scoring (Somatom VolumeZoom, Siemens, Forchheim, Germany) with retrospective ECG-gated data acquisition. Scanning was performed with a 4×2.5-mm collimation. In each patient data acquisition was performed twice using tube settings of 120 kVp with 133 mAs (protocol 1) and of 80 kVp with 300 mAs (protocol 2). Together with the 80-kVp protocol additional online ECG-related tube current modulation (ECG pulsing) was used. Three-millimeter overlapping slices (increment 1.5 mm) were calculated for each data set. Semi-automated calcium quantification was performed calculating absolute Ca-hydroxylapatite mass. In addition to patient examinations, the radiation exposure for both protocols was evaluated using computed tomography dose index (CTDI) phantom measurements. Protocol 2 showed a significantly lower patient radiation exposure than protocol 1 (0.72 vs 2.04 mSv; p<0.0001). The CTDI phantom measurements revealed a 65% reduction of radiation dose. Calcium scoring results of both protocols showed a high correlation (r=0.99; p<0.0001) for absolute Ca-Hydroxylapatite mass measurements. Using 80-kVp protocols patient radiation exposure can be significantly reduced in MSCT coronary artery calcium screening without affecting the detection and quantification of coronary artery calcification; therefore, this technique should be used with retrospective ECG-gated cardiac CT examinations in patients with regular sinus rhythm.     

Optimisation of multislice computed tomography protocols in angio–CT examinations

PURPOSE: The aim of this paper is to explain a general procedure for the optimisation of multislice computed tomography (MSCT) protocols. MATERIALS AND METHODS: Four angio-CT protocols with a GE LightSpeed Plus 4-slice CT scanner were considered. Effective doses were computed for a sample of patients. First the dose was optimised for arterial-phase scans on a standard patient and adapted to the weight of individual patients with a scaling factor. RESULTS: The mean effective dose for an angio-CT examination ranged from 18.8 mSv to 28.8 mSv, depending on the protocol adopted. Following the optimisation procedure, we drew up a table indicating tube current values for each patient weight. Calculation of the effective dose before and after the optimisation procedure revealed a dose reduction of about 40%. CONCLUSIONS: Angio-CT examinations deliver high doses, but these doses can be reduced without affecting image quality.     

多层螺旋ＣＴ在脊柱病变检查中的应用

目的　比较脊柱多层螺旋CT(MSCT)与单层螺旋CT(SSCT)图像质量的差异 ,探讨MSCT在脊柱病变检查中的应用价值。材料与方法　选择分别行MSCT和SSCT扫描的腰椎退行性病变者各 10例进行图像质量比较。应用LightSpeedQX/i型MSCT检查和诊断 3 1例脊椎病者。结果　在相同扫描条件下 ,腰椎MSCT图像质量明显优于SSCT ,MSCT所需扫描时间明显短于SSCT(均为P <0 .0 5 )。MSCT可为 3 1例脊椎病患者的临床诊断提供更多信息。结论　MSCT在脊柱病变检查中具有明显优势。     

Radiation dose evaluation in 64-slice CT examinations with adult and paediatric anthropomorphic phantoms

The objective of this study was to evaluate the organ dose and effective dose to patients undergoing routine adult and paediatric CT examinations with 64-slice CT scanners and to compare the doses with those from 4-, 8- and 16-multislice CT scanners. Patient doses were measured with small (<7 mm wide) silicon photodiode dosemeters (34 in total), which were implanted at various tissue and organ positions within adult and 6-year-old child anthropomorphic phantoms. Output signals from photodiode dosemeters were read on a personal computer, from which organ and effective doses were computed. For the adult phantom, organ doses (for organs within the scan range) and effective doses were 8–35 mGy and 7–18 mSv, respectively, for chest CT, and 12–33 mGy and 10–21 mSv, respectively, for abdominopelvic CT. For the paediatric phantom, organ and effective doses were 4–17 mGy and 3–7 mSv, respectively, for chest CT, and 5–14 mGy and 3–9 mSv, respectively, for abdominopelvic CT. Doses to organs at the boundaries of the scan length were higher for 64-slice CT scanners using large beam widths and/or a large pitch because of the larger extent of over-ranging. The CT dose index (CTDI_vol), dose–length product (DLP) and the effective dose values using 64-slice CT for the adult and paediatric phantoms were the same as those obtained using 4-, 8- and 16-slice CT. Conversion factors of DLP to the effective dose by International Commission on Radiological Protection 103 were 0.024 mSv⋅mGy⁻¹⋅cm⁻¹ and 0.019 mSv⋅mGy⁻¹⋅cm⁻¹ for adult chest and abdominopelvic CT scans, respectively.X-ray CT scanners have made remarkable advances over the past few years, contributing to the improvement of diagnostic image quality and the reduction of examination time. CT scanners with 64 slices, the clinical use of which started quite recently in many medical facilities, has enabled a large number of thin slices to be acquired in a single rotation. 64-slice CT technology accelerated the practical use of three-dimensional body imaging techniques such as coronary CT angiography and CT colonography with an increasing number of CT examinations. The increase in CT examination frequency not only for adults but also for children and the higher doses in CT examinations compared with other X-ray diagnostic procedures have raised concerns about patient doses and safety. An understanding of patient doses requires the evaluation of organ and effective doses for patients undergoing CT examinations, although these dose values in 64-slice CT scans have seldom been reported.One common method for estimating organ and effective doses is dose calculation from the CT dose index (CTDI) or dose–length product (DLP), which are both used as readily available indicators of radiation dose in CT examinations. Organ and effective doses can be estimated from the CTDI or DLP, and conversion factors derived from Monte Carlo simulation of photon interactions within a simplified mathematical model of the human body [1]. Another method is based on measurement using thermoluminescence dosemeters (TLDs) implanted in various organ positions within an anthropomorphic phantom [2–6]. Although TLD dosimetry is considered to be the standard method for measuring absorbed doses in a phantom, the dose measurement is laborious and time consuming. Hence, we devised an in-phantom dosimetry system using silicon photodiode dosemeters implanted in various organ positions, where absorbed dose at each position could be read electronically. In the present study, we evaluated organ and effective doses with 64-slice CT scan protocols used clinically for adult and paediatric patients undergoing chest and abdominopelvic CT examinations. We compared the doses with published dose values for 4-, 8- and 16-slice CT, and indicated the conversion factor of DLP to the effective dose in each examination of the chest and abdomen–pelvis for 64-slice CT scanners.     

Estimation of exposure dose on MDCT examination--the measurement of organ dose and effective dose by anthropomorphic phantom

In order to evaluate the exposure dose in CT examinations, we measured the tissue and organ doses by test site in 4-row, 16-row, and 64-row multi detector CT by using an anthropomorphic phantom and fluorescent glass dosimeters. Furthermore, we calculated the effective dose by using the tissue weighting factor recommended by the ICRP in 2007. The effective dose in the head and neck examinations was 1.4-3.1 mSv, whereas the maximum skin dose was 278.9 mGy in head perfusion CT. The effective dose in examinations of the body trunk was 10.1-35.2 mSv. In addition, the organ dose and skin dose in the scanning range was similar to the CTDI(vol) in head and neck examinations, while it was higher than the CTDI(vol) in examinations of the body trunk. The exposure dose of patients undergoing CT is high in comparison to other radiological examinations. As a result, due to consecutive examinations, an absorbed dose of more than 100 mGy is possible. A future problem therefore remains how to lower the overall exposure dose with the introduction of new radiographic diagnostic modalities, such as phase scan or coronary CT angiography.     

降低儿童16层螺旋CT检查辐射剂量的研究

目的论证CT扫描参数kVp和mAs与剂量和图像噪声的关系,在不影响临床诊断的基础上,修正并验证一种基于成人扫描参数的安全可行的儿童16层螺旋CT检查的扫描参数。方法利用16层螺旋CT,采用标准CT剂量指数(CTDI)测试仪、100mm笔型电离室,分别测量16cm和32cm直径模体在2mm×5mm准直宽度时不同kVp和mAs的CTDI;采用20cm标准水模,测量单一感兴趣区域(ROI)标准偏差值SD代表噪声水平。以成人扫描参数的不同百分比修正为不同年龄段儿童CT扫描的参数供临床验证。结果随着kVp和mAs的增加,CTDI随之增加,并与mAs呈线性关系;16cm直径模体的表面CTDI要高于32cm模体58%;实际的加权CTDIw值高于CT扫描仪显示的CTDIw;mAs相同时,kVp越高,图像噪声SD值越低,在kVp固定时,随着mAs的增加,图像噪声SD随之减少,当mAs增加到一定程度后,图像噪声趋向平稳。结论在不影响临床诊断的图像噪声水平下,根据年龄和体型特点,儿童16层CT检查mAs可以比成人降低10%～85%。     

Current CT practice in Germany: Results and implications of a nationwide survey

PurposeTo assess patient doses and relative frequencies of standard CT examinations performed in Germany in 2013/14 as well as the effect of modern CT technology on patient exposure.MethodsAll known CT facilities in Germany were requested to complete a questionnaire on the frequency of 34 examinations and the respective parameter settings used. Taking into account type-specific properties of each scanner, effective doses were estimated for each reported examination. The mean and the percentiles of the CT dose index, scan length, dose length product, and effective dose were determined for each type of examination.ResultsAccording to the data provided for about 11% of all medical CT scanners operated in 2013/14, the effective dose was 4.6/5.9 mSv per scan/examination. The effective dose was significantly reduced by about 15% compared to the CT practice before 2010. Modern CT technology, such as tube current modulation and iterative image reconstruction reduced the effective dose significantly by 6% and 13%, respectively. The mean effective dose applied at scanners produced by different manufacturers differed by 25%, at maximum.ConclusionPatient exposure was reduced substantially in recent years. There is, however, still a considerable potential for further dose reduction by adapting scan protocols to the medical purpose and by a consequent exploitation of modern CT technologies.     

Optimization of patient dose and image quality with z-axis dose modulation for computed tomography (CT) head in acute head trauma and stroke

The purpose of this study is to retrospectively analyze the effect of z-axis modulation for CT head protocols on patient dose and image quality in patients with acute head trauma and stroke. The study was approved by the Institutional Review Board. We retrospectively evaluated the effect of dose modulation on unenhanced CT head examinations in patients with acute head trauma and stroke. Two series of 100 consecutive studies were reviewed: 100 studies performed without dose modulation, 100 studies performed with z-axis dose modulation. Multidetector 16-section CT was performed sequentially and axial 5-mm-thick slices were obtained from base of skull to vertex. With z-axis dose modulation, the same tube current range was maintained, but a computer algorithm altered the tube current applied to each CT section. For each examination, the weighted volume CT dose index (CTDI (vol)) and dose-length product (DLP) were recorded and noise was measured. Each study was also reviewed for image quality by two independent, blinded readers. The variables (CTDI (vol) and DLP, image quality, and noise) in the two groups were compared by using student t test and Wilcoxon rank-sum test. For unenhanced CT head examinations, the CTDI (vol) and DLP, respectively, were reduced by 35.8% and 35.2%, respectively, by using z-axis dose modulation. Image quality and noise were unaffected by the use of this dose modulation technique (P?<?0.004). Utilization of z-axis modulation technique for CT head examination in patients with acute head trauma and stroke offers significant radiation dose reduction while image quality is optimally maintained.     

Survey of pediatric MDCT radiation dose from university hospitals in Thailand: a preliminary for national dose survey

Background Increasing pediatric CT usage worldwide needs the optimization of CT protocol examination. Although there are previous published dose reference level (DRL) values, the local DRLs should be established to guide for clinical practice and monitor the CT radiation. Purpose To determine the multidetector CT (MDCT) radiation dose in children in three university hospitals in Thailand in four age groups using the CT dose index (CTDI) and dose length product (DLP). Material and Methods A retrospective review of CT dosimetry in pediatric patients (<15 years of age) who had undergone head, chest, and abdominal MDCT in three major university hospitals in Thailand was performed. Volume CTDI (CTDI(vol)) and DLP were recorded, categorized into four age groups: <1 year, 1-< 5 years, 5-<10 years, and 10-<15 years in each scanner. Range, mean, and third quartile values were compared with the national reference dose levels for CT in pediatric patients from the UK and Switzerland according to International Commission on Radiological Protection (ICRP) recommendation. Results Per age group, the third quartile values for brain, chest, and abdominal CTs were, respectively, in terms of CTDI(vol): 25, 30, 40, and 45 mGy; 4.5, 5.7, 10, and 15.6 mGy; 8.5, 9, 14, and 17 mGy; and in terms of DLP: 400, 570, 610, and 800 mGy cm; 80, 140, 305, and 470 mGy cm; and 190, 275, 560,765 mGy cm. Conclusion This preliminary national dose survey for pediatric CT in Thailand found that the majority of CTDI(vol) and DLP values in brain, chest, and abdominal CTs were still below the diagnostic reference levels (DRLs) from the UK and Switzerland regarding to ICRP recommendation.     

Comparative evaluation of organ and effective doses for paediatric patients with those for adults in chest and abdominal CT examinations

Patient doses in paediatric and adult CT examinations were investigated for modern multislice CT scanners by using specially constructed in-phantom dose measuring systems. The systems were composed of 32 photodiode dosemeters embedded in various tissue and organ sites within anthropomorphic phantoms representing the bodies of 6-year-old children and adults. Organ and the effective doses were evaluated from dose values measured at these sites. In chest CT examinations, organ doses for organs within the scanning area were 2-21 mGy for children and 7-26 mGy for adults. Thyroid doses for children were frequently the highest with a maximum of 21 mGy. In abdominal CT examinations, organ doses for organs within the scanning area were 3-16 mGy for children and 10-34 mGy for adults. Effective doses evaluated for children and adults were found to be proportional to the effective mAs of CT scanners, where linear coefficients were specific to the types of CT examinations and to the manufacturers of CT scanners. Effective doses in paediatric chest CT and abdominal CT examinations were lower than those in adult examinations by a factor of two or greater on average for the same CT scanners because of the lower effective mAs adopted in paediatric examinations.     

Single- and multi-slice spiral computed tomography of the paediatric kidney

Single- and multi-slice computed tomography (CT) is regarded as the primary imaging tool in traumatology, both in adults and children. For complicated infectious disease and renal tumours, these techniques are recommended only as secondary diagnostic tools. Specifically, multi-slice CT (MSCT) provides excellent spatial resolution, which is a particular advantage for the evaluation of small structures as they are typical in children. However, MSCT offers more information than is required for diagnosis. Therefore, low-dose protocols are necessary for paediatric examinations. The CT dose-index (CTDI(vol)) should not exceed 2 mGy for newborns, 4 mGy for toddlers, 5 mGy for elementary school children, and 8 mGy for adolescents.