CT dose reduction in practice

Assessment of radiation exposure among pediatric patients referred for CT imaging at three government hospitals in Addis Ababa, Ethiopia

Background

Due to the high sensitivity of their growing tissues to ionizing radiation, pediatric patients are at a greater risk of cancer development.

Objective

This study aimed to evaluate the level of radiation exposure experienced by pediatric patients undergoing a common CT examination at the three government hospitals in Addis Ababa, Ethiopia.

Materials and methods

Structured formats were designed for data collection at three government hospitals, and then information about pediatric patients' demography, CT protocols, and CT systems was retrieved and recorded from March 2018 up to July 2018. CT dose indicators: CTDIvol (mGy) and DLP (mGy.cm) values for abdomen, chest, and head CT scans were recorded based on pediatric patients' age ⩽1, (1-5], (5-10], and (10-15] years old. The data were analyzed through SPSS version 25 software. Finally, the third quartile values of CTDIvol and DLP were determined and compared with other international DRLs.

Results

The third quartile values of radiation dose descriptors for abdomen, chest, and head CT scans, respectively, in terms of CTDIvol (mGy): 58, 10, 17, 51; 23, 23, 34, 51; 62, 41, 50, 51; and in terms of DLP (mGy.cm), 377, 314, 624, 664; 523, 571, 406, 739; 927, 806, 929, and 1197 corresponded to pediatric patients of age ⩽1, (1-5], (5-10], and (10-15] years old, respectively.

Conclusion

There were significant differences in the radiation dosage of some CT examinations between the same age groups, indicating a need for dose optimization. Therefore, this study recommends the need for enhancing radiation safety, ensuring appropriate imaging practices, and prioritizing the well-being of pediatric patients who visit CT examinations in Addis Ababa, Ethiopia.

How Can Specialist Advice Influence the Neuroimaging Practice for Childhood Headache in Emergency Department?

Differentiating between primary and secondary headaches can be challenging, especially in the emergency department (ED). Since symptoms alone are inadequate criteria for distinguishing between primary and secondary headaches, many children with headaches undergo neuroimaging investigations, such as brain CT and MRI. In various studies, the frequency of neuroimaging utilization is influenced by several factors, including teaching status, ownership, metropolitan area, insurance status, and ethnicity of patients. However, only a few studies have considered the role of specialist consultations in ordering neuroimaging studies on childhood headaches. We report the contributions of different specialists to the evaluation of children with headaches admitted to the ED and their influence on neuroimaging decisions. We retrospectively reviewed the medical reports of paediatric patients who presented with headaches to the paediatric ED of the Ospedale Maggiore Policlinico of Milano between January 2017 and January 2022. Overall, 890 children with headaches were evaluated (mean age: 10.0 years; range: 1 to 17 years). All patients were examined by the ED paediatricians, while specialist consultations were required for 261 patients, including 240 neurological (92.0%), 46 ophthalmological (17.6%), and 20 otorhinolaryngological (7.7%) consultations. Overall, 173 neuroimaging examinations were required, of which 51.4 and 48.6% were ordered by paediatricians and neurologists, respectively. In particular, paediatricians required 61.4% of brain CT scans, and neurologists required 92.0% of brain MRI scans. In conclusion, paediatricians were responsible for the management of most children with headaches admitted to the ED, while specialist consultations were required only in about a third of the cases. Although there was no significant difference in the number of neuroimaging studies ordered by specialists, brain CT scans were most often used by paediatricians, and MRI scans by neurologists.

Reconsidering pregnancy screening policies for minors: patient-specific estimate of fetus and effective dose for potentially pregnant minors undergoing optimized dose CT of the pelvis

BACKGROUND

Only verbal pregnancy screening is recommended for post-menarcheal females undergoing pelvic radiographs. In contrast, usually, a urine/serum pregnancy test for pelvic computed tomographic (CT) exams is required out of concern for higher radiation exposure.

OBJECTIVE

To estimate patient-specific fetus absorbed dose to a potentially pregnant minor from an optimized dose CT of the pelvis for femoral version and surgical planning and provide evidence that such examinations of the pelvis can be performed with only verbal pregnancy screening.

METHODS AND METHODS

A retrospective study was performed on 102 female patients between 12-18 years of age (15.4 ± 2.1 years) who underwent optimized dose CT of the pelvis for orthopedic evaluation of femoral version and surgical planning. Optimized CT exams were performed with weight-adjusted kVp and tube current modulation. Patient-specific dose from the optimized dose CT was calculated using the National Cancer Institute Dosimetry System for CT (NCICT) database by matching each patient to a phantom from the NCI non-reference phantom library based on patient sex, weight, and height. The calculated absorbed uterus dose was used as a surrogate for the fetus dose. Furthermore, patient-specific organ doses were used to estimate the effective dose. The strengths of the linear relationships between the dose metrics and patient characteristics were assessed using Pearson correlation coefficients through linear regression.

RESULTS

The mean patient-specific effective dose for an optimized dose CT of the pelvis was 0.54 ± 0.20 mSv (range: 0.15-1.22 mSv). The mean estimated absorbed uterine dose was 1.57 ± 0.67 mGy (range: 0.42-4.81 mGy). Both effective dose and estimated uterine dose correlated poorly with patient physical characteristics (R = -0.26; 95% CI: [-0.43, -0.007] for age, R = 0.03; 95% CI: [-0.17, 0.22] for weight) but correlated strongly (R = 0.79, 95% CI: [0.7, 0.85]) with CTDIvol.

CONCLUSION

The estimated fetus dose in case of pregnancy was significantly lower than 20 mGy for urine/serum pregnancy screening, suggesting that the pregnancy screening protocols in minors undergoing optimized dose CT require reassessment and may be safely performed by verbal attestation only.

Establishment of local diagnostic reference levels for common adult CT examinations: a multicenter survey in Addis Ababa

BACKGROUND

In medical imaging, a computed tomography (CT) scanner is a major source of ionizing radiation. All medical radiation exposures should be justified and optimized to meet the clinical diagnosis. Thus, to avoid unnecessary radiation doses for patients, diagnostic reference levels (DRLs) have been used. The DRLs are used to identify unusually high radiation doses during CT procedures, which are not appropriate for the clinical diagnosis. It has been successfully implemented in Europe, Canada, Australia, the United States, several industrialized countries, and a few underdeveloped countries. The present study aimed to establish DRLs for the head, chest, and abdominopelvic (AP) CT procedures in Addis Ababa, Ethiopia.

METHODS

A pilot study identified the most frequent CT examinations in the city. At the time of the pilot, eighteen CT scan facilities were identified as having functioning CT scanners. Then, on nine CT facilities (50% of functional CT scanners), a prospective analysis of volume CT dose index (CTDI_vol) and dose length product (DLP) was performed. We collected data for 838 adult patients' head, chest, and AP CT examinations. SPSS version 25 was used to compute the median values of the DLP and CTDI_vol dose indicators. The rounded 75th percentile of CTDI_vol and DLP median values were used to define the DRLs. The results are compared to DRL data from the local, regional, and international levels.

RESULT

The proposed DRLs using CTDI_vol (mGy) are 53, 13, and 16 for the head, chest, and AP examinations respectively, while the DLP (mGy.cm) for the respective examinations were 1210, 635, and 822 mGy.cm.

CONCLUSION

Baseline CT DRLs figures for the most frequently performed in Addis Ababa were provided. The discrepancies in dose between CT facilities and as well as between identical scanners suggests a large potential for dose optimization of examinations. This can be actually achieved through appropriate training of CT technologists and continuous dose audits.

Intraorbital self-inflating hydrogel expander implantation with a modified technique in congenital microphthalmia

PURPOSE

To investigate the long-term outcomes of intraorbital self-inflating hydrogel expander implantation with optic nerve transection in children with congenital microphthalmia.

METHODS

The medical records of unilaterally blind microphthalmic pediatric patients undergoing intraconal hydrogel expander implantation with optic nerve transection were reviewed retrospectively. For each patient, the microphthalmic eye was preserved. The orbital volume and globe volume were measured and analyzed based on computed tomography scans taken preoperatively and 36 months postoperatively. The palpebral length was measured between the medial and lateral canthus at every follow-up. Surgical complications were also recorded.

RESULTS

Twelve patients were included (median age, 44.25 ± 17.5 months). At 36 months postoperatively, the microphthalmic and contralateral orbital volumes increased by 3.07 ± 0.77 ml and 2.03 ± 0.67 ml, respectively. The mean microphthalmic/contralateral ratio (MCR) of the orbital volume increased significantly from 76.60% ± 5.46% to 83.81% ± 5.41% (P < 0.001). The microphthalmic palpebral length increased by 6.17 ± 1.85 mm, whereas the contralateral palpebral length increased by 2.67 ± 1.44 mm. Significant changes were observed in the palpebral length MCR (68.00% ± 4.83% vs 85.07% ± 3.87%; P < 0.001). There was no significant change in the microphthalmic globe volume at 36 months postoperatively (P = 0.215). For the fellow eye, the globe volume increased significantly by 0.53 ± 0.34 ml (P < 0.001). During the follow-up period, 2 patients developed a sunken prosthesis. One patient had difficulty opening the eye after wearing the conformer. There were no cases of expander rejection or extrusion.

CONCLUSIONS

In this small cohort of patients with congenital microphthalmia, intraorbital self-expanding hydrogel expander implantation with optic nerve transection led to excellent osseous and eyelid growth throughout the 36-month follow-up period.

Orbital Volume and Axial Length Development in Individuals Ages 12 to 60 Years With Congenital Microphthalmia: A Retrospective Cohort Study

OBJECTIVE

To analyze the stimulating effect of axial length development on orbital volume development in patients (ages 12-60 years) with congenital microphthalmia.

METHODS

This retrospective cohort study included 43 patients (86 eyes) with congenital microphthalmia. Three-dimensional images of the orbit were generated from past computed tomography scans, and digital orbital volume and axial length measurements were taken. The patients were divided into four age groups for analyses. Paired t tests and one-way analysis of variance tests were used to compare orbital volume and axial length between the affected and unaffected eyes. Pearson correlation analyses and scatter plots were used to investigate the correlations between age, orbital volume, and axial length in the affected and unaffected eyes. Linear regression analysis was used to determine the association between orbital volume and axial length.

RESULTS

The mean orbital volume in the affected and unaffected eyes was 17.08 ± 2.88 and 20.80 ± 2.55 cm3, respectively. The mean axis length in the affected and the unaffected groups was 12.73 ± 3.54 and 23.84 ± 1.43 mm, respectively. Significant differences were observed among orbital (t = 13.538, P < 0.001) volume and axial length (t = 21.339, P < 0.001) in the affected and the unaffected groups. There were no significant differences in affected orbital volume (F = 0.527, P > 0.05), unaffected orbital volume (F = 1.628, P > 0.05), affected axial length (F = 0.946, P > 0.05), and unaffected axial length (F = 2.217, P > 0.05) among the four age groups. According to the Pearson correlations, there were no significant correlations between age and affected volume, unaffected volume, affected axis, and unaffected axis (r = 0.095, 0.097, 0.084, and 0.022, respectively; all P > 0.05). Orbital volume was moderately correlated with axial length in the affected and unaffected groups (r = 0.470 and 0.410, respectively; both P < 0.01). Linear regression analysis revealed that a 1 mm change in axis length was associated with a 0.38 cm3 and 0.73 cm3 change in orbital volume in the affected and unaffected groups, respectively.

CONCLUSIONS

In individuals ages 12 to 60 years old with congenital microphthalmia, the effect of axis length on the orbital volume growth of the affected eye is only half that of the unaffected eye. The eyeball, orbital tissue, and craniofacial development all play an important role in the growth of orbital volume.

Utilization of CT imaging in minor pediatric head, thoracic, and abdominal trauma in the United States

BACKGROUND

Liberal use of CT scanning in children with blunt trauma risks unnecessary radiation exposure and cost. Recent literature questions the utility of whole-body CT in stable children without clinical evidence of significant injury, but this is often done based on injury mechanism. The purpose of this study is to quantify the utilization of CT scans of the head, chest, abdomen, and pelvis based on injury severity in these body regions and to assess the impact of American College of Surgeons (ACS) pediatric trauma center designation on CT utilization in children with minor or no injuries.

METHODS

We queried the National Trauma Databank for 2014, 2015, and 2016 to identify all patients 14 years and younger. Using Abbreviated Injury Scale (AIS) score as a proxy for injury severity, we analyzed the number of head, thoracic, and abdominal CT scans done for patients at low levels of injury severity (AIS 0-2) in each of these body regions and according to trauma center level designation (ACS I, II, III, standalone pediatric I or II, and non ACS accredited).

RESULTS

Of 257,661 children who were entered into the database for any reason, overall CT utilization was 20% for head, 5% for the chest and 9% for the abdomen and pelvis. Children with no injuries or minimal injury to the head were scanned 7% and 46% of the time, respectively, for the chest 3% and 13% and for the abdomen 6% and 30%. For all body regions and all levels of injury severity, level 1 stand-alone pediatric centers displayed significantly lower CT utilization rates than others.

CONCLUSION

CT scan rates for children with minimal or no injuries to the head, chest, abdomen and pelvis are significant. Level 1 stand-alone pediatric trauma centers are least likely to perform these studies. Widespread education and acceptance of clinical guidelines for imaging in stable patients throughout trauma systems could alleviate this disparity.

LEVEL OF EVIDENCE

Level III retrospective comparative study.

Strategies for dose reduction with specific clinical indications during computed tomography

Increasing integration of computed tomography (CT) into routine patient care has escalated concerns regarding associated radiation exposure. Specific patient cohorts, particularly those with cystic fibrosis (CF) and Crohn's disease, have repeat exposures and thus have an increased risk of high lifetime cumulative effective dose exposures. Thoracic CT is the gold standard imaging method in the diagnosis, assessment and management of pulmonary disease. In the setting of CF, CT demonstrates increased sensitivity compared with pulmonary function tests and chest radiography. Furthermore, in specific cases of Crohn's disease, CT demonstrates diagnostic superiority over magnetic resonance imaging (MRI) for radiological evaluation. Low dose CT protocols have proven beneficial in the evaluation of CF, Crohn's disease and renal calculi, and in the follow up of testicular cancer patients. For individuals with chronic conditions warranting frequent radiological follow up, the focus must continue to be the incorporation of appropriate CT use into patient care. This is of particular importance for the paediatric population who are most susceptible to potential radiation induced malignancy. CT technological developments continue to focus on radiation dose optimisation. This article aims to highlight these advancements, which prioritise the acquisition of diagnostically satisfactory images with the least amount of radiation possible.

Development of a computational tool for estimating computed tomography dose parameters

BACKGROUND

Computed Tomographic (CT) imaging procedures have been reported as the main source of radiation in diagnostic procedures compared to other modalities. To provide the optimal quality of CT images at the minimum radiation risk to the patient, periodic inspections and calibration tests for CT equipment are required. These tests involve a series of measurements that are time consuming and may require specific skills and highly-trained personnel.

OBJECTIVE

This study aims to develop a new computational tool to estimate the dose of CT radiation outputs and assist in the calibration of CT scanners. It may also provide an educational resource by which radiological practitioners can learn the influence of technique factors on both patient radiation dose and the produced image quality.

METHODS

The computational tool was developed using MATLAB in order to estimate the CT radiation dose parameters for different technique factors. The CT radiation dose parameters were estimated from the calibrated energy spectrum of the x-ray tube for a CT scanner.

RESULTS

The estimated dose parameters and the measured values utilising an Adult CT Head Dose Phantom showed linear correlations for different tube voltages (80 kVp, 100 kVp, 120 kVp, and 140 kVp), with R2 nearly equal to 1 (0.99). The maximum differences between the estimated and measured CTDIvol were under 5 %. For 80 kVp and low tube currents (50 mA, 100 mA), the maximum differences were under 10%.

CONCLUSIONS

The prototyped computational model provides a tool for the simulation of a machine-specific spectrum and CT dose parameters using a single dose measurement.

Protecting sensitive patient groups from imaging using ionizing radiation: effects during pregnancy, in fetal life and childhood

The frequency of imaging examinations requiring radiation exposure in children (especially CT) is rapidly increasing. This paper reviews the current evidence in radiation protection in pediatric imaging, focusing on the recent knowledge of the biological risk related to low doses exposure. Even if there are no strictly defined limits for patient radiation exposure, it is recommended to try to keep doses as low as reasonably achievable (the ALARA principle). To achieve ALARA, several techniques to reduce the radiation dose in radiation-sensitive patients groups are reviewed. The most recent recommendations that provide guidance regarding imaging of pregnant women are also summarized, and the risk depending on dose and phase of pregnancy is reported. Finally, the risk-benefit analysis of each examination, and careful communication of this risk to the patient, is emphasized.

Management of congenital microphthalmos and anophthalmos with orbital cyst

PURPOSE

To study the effects of an individualized treatment approach to children with congenital microphthalmos and anophthalmos.

METHODS

Patients with congenital microphthalmos or anopthalmos with orbital cysts who were referred to Beijing Tongren Hospital between July 2009 and July 2017 were included in this retrospective case series study. For patients ≤6 years of age, the cyst was retained to promote orbital development unless a prosthesis could not be fitted at all or disproportionate orbital growth was detected. Hydrogel orbit expanders were implanted initially if orbital volume was poor. For patients >6 years of age, the cyst was removed if it caused cosmetic problems or unsatisfactory prosthesis fitting. Eyelid procedures were performed after puberty to improve appearance.

RESULTS

The study included 26 orbits of 24 patients. Of the 14 patients ≤6 years, 3 underwent cyst excision, 8 were treated with conformers only, and 3 had hydrogel orbit expander implantation initially. Of the 10 patients >6 years, 1 had the cyst removed, 5 had eyelid surgeries without removing the cyst, 3 wore an artificial eye without any surgery, and 1 used no prosthesis. During the follow-up period (range, 6 months to 8 years), 23 patients had a good cosmetic outcome and were eventually able to retain an ocular prosthesis; 1 patient could not wear prostheses but refused further treatment. No procedure-related complications were noted.

CONCLUSIONS

The individualized treatment of congenital microphthalmos and anophthalmos with orbital cysts depends on the patient's age at presentation, the growth pattern of the cyst, and the volume of the affected orbit.

Agreement between magnetic resonance imaging and computed tomography in the postnatal evaluation of congenital lung malformations: a pilot study

OBJECTIVES

To compare postnatal magnetic resonance imaging (MRI) with the reference standard computed tomography (CT) in the identification of the key features for diagnosing different types of congenital lung malformation (CLM).

METHODS

Respiratory-triggered T2-weighted single-shot turbo spin echo (ss-TSE), respiratory-triggered T1-weighted turbo field echo (TFE), balanced fast field echo (BFFE), and T2-weighted MultiVane sequences were performed at 1.5 T on 20 patients prospectively enrolled. Two independent radiologists examined the postnatal CT and MRI evaluating the presence of cysts, hyperinflation, solid component, abnormal arteries and/or venous drainage, and bronchocele. Diagnostic performance of MRI was calculated and the agreement between the findings was assessed using the McNemar-Bowker test. Interobserver agreement was measured with the kappa coefficient.

RESULTS

CT reported five congenital pulmonary airway malformations (CPAMs), eight segmental bronchial atresias, five bronchopulmonary sequestrations (BPS), one congenital lobar overinflation, one bronchogenic cyst, and three hybrid lesions. MRI reported the correct diagnosis in 19/20 (95%) patients and the malformation was correctly classified in 22/23 cases (96%). MRI correctly identified all the key findings described on the CT except for the abnormal vascularization (85.7% sensitivity, 100% specificity, 100% PPV, 94.1% NPV, 95% accuracy for arterial vessels; 57.1% sensitivity, 100% specificity, 100% PPV, 84.2% NPV, 87% accuracy for venous drainage).

CONCLUSIONS

MRI can represent an effective alternative to CT in the postnatal assessment of CLM. In order to further narrow the gap with CT, the use of contrast material and improvements in sequence design are needed to obtain detailed information on vascularization, which is essential for surgical planning.

KEY POINTS

• Congenital lung malformations (CLMs) can be effectively studied by MRI avoiding radiation exposure. • Crucial features of CLM have similar appearance when comparing CT with MRI. • MRI performs very well in CLM except for aberrant vessel detection and characterization.

Conical ultrashort echo time (UTE) MRI in the evaluation of pediatric acute appendicitis

PURPOSE

Magnetic resonance imaging (MRI) sequences with conical k-space trajectories are able to decrease motion artifacts while achieving ultrashort echo times (UTE). We assessed the performance of free-breathing conical UTE MRI in the evaluation of the pediatric pelvis for suspected appendicitis.

METHODS

Our retrospective review of 84 pediatric patients who underwent MRI for suspected appendicitis compared three contrast-enhanced sequences: free-breathing conical UTE, breath-hold three-dimensional (3D) spoiled gradient echo (BH-SPGR), and free-breathing high-resolution 3D SPGR (FB-SPGR). Two radiologists performed blinded and independent evaluations of each sequence for image quality (four point scale), anatomic delineation (four point scale), and diagnostic confidence (five point scale). Subsequently, the three sequences were directly compared for overall image quality (- 3 to + 3 scale). Scores were compared using Kruskal-Wallis and Wilcoxon signed-rank tests.

RESULTS

UTE demonstrated significantly better perceived signal-to-noise ratio (SNR) and fewer artifacts than BH-SPGR and FB-SPGR (means of 3.6 and 3.4, 3.4 and 3.2, 3.1 and 2.7, respectively; p < 0.0006). BH-SPGR and FB-SPGR demonstrated significantly better contrast than UTE (means of 3.6, 3.4, and 3.2, respectively; p < 0.03). In the remaining categories, UTE performed significantly better than FB-SPGR (p < 0.00001), while there was no statistical difference between UTE and BH-SPGR. Direct paired comparisons of overall image quality demonstrated the readers significantly preferred UTE over both BH-SPGR (mean + 0.5, p < 0.00001) and FB-SPGR (mean + 1.2, p < 0.00001).

CONCLUSIONS

In the evaluation of suspected appendicitis, free-breathing conical UTE MRI performed better in the assessed metrics than FB-SPGR. When compared to BH-SPGR, UTE demonstrated superior perceived SNR and fewer artifacts.

Influence of gantry rotation time and scan mode on image quality in ultra-high-resolution CT system

OBJECTIVES

To investigate the image quality of helical scan (HS) mode and non-helical scan (non-HS) mode on ultra-high-resolution CT in different gantry rotation time.

METHODS

non-HS with 0.35 s/rot (non-HS200 mA/0.35 s). Three observers compared each non-HS image with HS image, and scored non-HS images by using 3-point scale, paying attention to normal findings, abnormal findings, noise, streak artifact, and overall image quality. Statistical analysis was performed with Steel-Dwass test.

RESULTS

Overall image quality (score: 2.45) and noise (score: 2.42) of non-HS 200 mA/1.5s was statistically best (p < 0.0005). Overall Image quality and noise of non-HS200 mA/0.75 s (score: 2.0) was comparable to that of HS200 mA/1.5 s. CTDIvol of HS200 mA/1.5 s is 23.2 mGy. CTDIvol of non-HS200 mA/1.5 s, non-HS200 mA/0.75 s, non-HS200 mA/0.35 s is 19.2 mGy, 9.8 mGy, 4.7 mGy.

CONCLUSION

Overall image quality and noise of non-helical scan is better than that of helical scan in the same rotation time. Overall Image quality of non-HS200 mA/0.75 s is comparable to that of HS200 mA/1.5 s, though the radiation dose of non-HS200 mA/0.75 s is lower than that of HS200 mA/1.5 s.

Computed tomography localization of the appendix in the pediatric population relative to the lumbar spine

BACKGROUND

Computed tomography (CT) is commonly used to evaluate suspected acute appendicitis. Although very effective, CT uses ionizing radiation, exposing patients to an increased risk of cancer.

OBJECTIVE

This study assessed the potential for decreasing the field of view of the CT (and therefore the dose to the patient) in the evaluation of suspected acute appendicitis in children.

MATERIALS AND METHODS

This study was a retrospective review of prospectively collected data from 212 consecutive patients who underwent CT for suspected acute appendicitis. The most superior aspect of the appendix with respect to vertebral bodies was recorded. Age, gender and diagnosis (negative, acute appendicitis or alternative diagnosis) were noted.

RESULTS

The appendix was visualized in 190 of 212 subjects (89.6%). Overall, all visualized appendixes were located at or below the level of L1. Sixty-three of the subjects (29.7%) were diagnosed with acute appendicitis via CT imaging. All appendixes in patients with acute appendicitis were located at or below the level of the L3 vertebral body, predominating at the level of L5. Six subjects (3.1%) received alternative diagnoses, including pneumonia, pyelonephritis, small bowel obstruction and infected urachal cyst. There were no differences in appendix location with regard to diagnosis, gender, or age (P=0.664, 0.748 and 0.705, respectively).

CONCLUSION

CT field of view may be decreased to the level of L1 or L3 superiorly, decreasing radiation dose without affecting the rate of appendix visualization.

Quantitative CT characterization of pediatric lung development using routine clinical imaging

BACKGROUND

The use of quantitative CT analysis in children is limited by lack of normal values of lung parenchymal attenuation. These characteristics are important because normal lung development yields significant parenchymal attenuation changes as children age.

OBJECTIVE

To perform quantitative characterization of normal pediatric lung parenchymal X-ray CT attenuation under routine clinical conditions in order to establish a baseline comparison to that seen in pathological lung conditions.

MATERIALS AND METHODS

We conducted a retrospective query of normal CT chest examinations in children ages 0-7 years from 2004 to 2014 using standard clinical protocol. During these examinations semi-automated lung parenchymal segmentation was performed to measure lung volume and mean lung attenuation.

RESULTS

We analyzed 42 CT examinations in 39 children, ages 3 days to 83 months (mean ± standard deviation [SD] = 42 ± 27 months). Lung volume ranged 0.10-1.72 liters (L). Mean lung attenuation was much higher in children younger than 12 months, with values as high as -380 Hounsfield units (HU) in neonates (lung volume 0.10 L). Lung volume decreased to approximately -650 HU by age 2 years (lung volume 0.47 L), with subsequently slower exponential decrease toward a relatively constant value of -860 HU as age and lung volume increased.

CONCLUSION

Normal lung parenchymal X-ray CT attenuation decreases with increasing lung volume and age; lung attenuation decreases rapidly in the first 2 years of age and more slowly thereafter. This change in normal lung attenuation should be taken into account as quantitative CT methods are translated to pediatric pulmonary imaging.

Novel control of gel fraction and enhancement of bonding strength for constructing 3D architecture of tissue engineering scaffold with alginate tubular fiber

Alginate tubular fiber has been successfully prepared via coaxial fluid crosslink mode, which is potentially used for the construction of vascularized tissue engineering scaffolds (VTES). However, its elastic and smooth surface is negative for the adhesion of fibers. In this study, the gel fractions were controlled in a novel way of two-step crosslink process in order to meet the needs of each processing link. Based on such consideration, an appropriate formulation was selected to direct write single fiber, which ensured the tubular structure with enough gel portion as well as adhesion between fibers with the reserved sol. Finally, the integrity of the scaffolds had a further development within the 2nd crosslink bath process, which would help to solve the question of poor shear resistance for hydrogel scaffolds.

Digital Evaluation of Orbital Cyst Associated with Microphthalmos: Characteristics and Their Relationship with Orbital Volume

Purpose

To study the characteristics of orbital cyst associated with microphthalmos in a group of Chinese patients, and to analyze the relationship between orbital cyst and orbital volume.

Design

Cross-sectional comparative study.

Participants

120 patients who were diagnosed as unilateral clinical blind microphthalmos, in which 20 patients had orbital cyst in the affected eye.

Method

Participants had computed tomography (CT) scan. CT images were analyzed with a computer-aided software.

Main Outcome Measures

Volume and position of orbital cyst, microphthalmic to contralateral ratio (MCR) of orbital volume, height and depth and orbital rim displacement.

Results

38.1% of the cysts located anterior to or at the equator of the globe, 75% of which located infratemporally and all of which were outside the muscle cone. Most (84.6%) of the posterior cysts were inside the muscle cone. The anterior cysts were larger than the posterior cysts (p = 0.005). MCR of orbital volume (p<0.001), height (p = 0.004) and width (p = 0.043) were significantly higher in patients with orbital cyst than controls. For patients with orbital cyst, larger cyst-plus-globe volume of the affected eye was associated with higher MCR of orbital volume (r = 0.630, p = 0.003). Patients with large cyst-plus-globe volume had higher MCR of orbital volume (p = 0.002), height (p = 0.014), width (p = 0.005) and depth (p = 0.002) and less displacement in inferior (p = 0.004) orbital rim, compared with patients with small cyst-plus-globe volume, but the differences between patients with small cyst-plus-globe volume and patients without cyst were not significant.

Conclusions

Microphthalmic eyes with large cyst-plus-globe volume showed better similarity with the contralateral eyes, comparing with microphthalmic eyes without orbital cyst or with small cyst-plus-globe volume. It suggested that the existence of orbital cysts (especially large cysts) in microphthalmic eyes might play a positive role in the orbital development.

Point-of-care ultrasonography by pediatric emergency physicians. Policy statement

Point-of-care ultrasonography is increasingly being used to facilitate accurate and timely diagnoses and to guide procedures. It is important for pediatric emergency physicians caring for patients in the emergency department to receive adequate and continued point-of-care ultrasonography training for those indications used in their practice setting. Emergency departments should have credentialing and quality assurance programs. Pediatric emergency medicine fellowships should provide appropriate training to physician trainees. Hospitals should provide privileges to physicians who demonstrate competency in point-of-care ultrasonography. Ongoing research will provide the necessary measures to define the optimal training and competency assessment standards. Requirements for credentialing and hospital privileges will vary and will be specific to individual departments and hospitals. As more physicians are trained and more research is completed, there should be one national standard for credentialing and privileging in point-of-care ultrasonography for pediatric emergency physicians.

Successful Dose Reduction Using Reduced Tube Voltage With Hybrid Iterative Reconstruction in Pediatric Abdominal CT

OBJECTIVE

The purpose of this article is to assess radiation dose reduction, image quality, and diagnostic confidence using low tube voltage in combination with hybrid iterative reconstruction in contrast-enhanced pediatric abdominal CT.

MATERIALS AND METHODS

CT examinations of 133 patients (median age, 10 years) were performed at sequentially reduced doses. The first group (group 1) was scanned using dimension-based protocols at 120 kV for all patient sizes. The optimized group (group 5) was scanned at 80 kV for less than 18 cm in the lateral dimension and 100 kV in the 19-30 cm lateral dimension. CT examinations reconstructed with filtered back projection (FBP) and four levels of hybrid iterative reconstruction were reviewed by four blinded readers for subjective image quality and diagnostic confidence. Objective noise, volume CT dose index (CTDIvol), and size-specific dose estimate (SSDE) were recorded. Data were analyzed using t tests, one and two-way ANOVA, and the intraclass correlation coefficient.

RESULTS

Compared with group 1, the radiation dose was reduced for group 5 by 63% measured by SSDE (4.69 vs 10.00 mGy; p < 0.001). Subjective image noise was increased for FBP images (p < 0.001) but not was statistically significantly different for all levels of hybrid iterative reconstruction; artifacts were reduced and visibility of small structures was improved (both p < 0.001). Diagnostic confidence was improved for solid organ injury and metastatic disease (both p < 0.001) and was not statistically significantly different for appendicitis (p = 0.306).

CONCLUSION

Use of hybrid iterative reconstruction with low-tube-voltage protocols enables substantial radiation dose reduction for pediatric abdominal CT with equivalent to improved subjective image quality and diagnostic confidence.

Computed tomography-related radiation exposure in children transferred to a Level I pediatric trauma center

PURPOSE

Pediatric trauma patients presenting to referring facilities (RF) often undergo computed tomography (CT) scans to identify injuries before transfer to a Level I pediatric trauma center (PTC). The purpose of our study was to evaluate RF compliance with the American College of Radiology (ACR) guidelines to minimize ionizing radiation exposure in pediatric trauma patients and to determine the frequency of additional or repeat CT imaging after transfer to a PTC.

METHODS

After institutional review board approval, a retrospective review of all pediatric trauma admissions from January 2010 to December 2011 at our American College of Surgeons Level I PTC was performed. Patient demographics, means of arrival, Injury Severity Score, and disposition were analyzed. Patients who underwent CT were grouped by means of arrival: those who were transferred from an RF versus those who presented primarily to the PTC. Compliance with ACR guidelines and need for additional or repeat CT scans were assessed for both groups.

RESULTS

Six hundred ninety-seven children (aged <18 years) were identified, with a mean age of 10.6 years. Three hundred twenty-one (46%) patients presented primarily to the PTC. Three hundred seventy-six (54%) were transferred from an RF, of which 90 (24%) patients underwent CT imaging before transfer. CT radiation dosing information was available for 79 (88%) of 90 patients. After transfer, 8 (9%) of 90 of children imaged at an RF required additional CT scans. In comparison, 314 (98%) of 321 patients who presented primarily to the PTC and underwent CT received appropriate pediatric radiation dosing. Mean radiation dose at PTC was approximately half of that at RF for CT scans of the head, chest, and abdomen/pelvis (p < 0.01).

CONCLUSION

Pediatric trauma patients transferred from RF often undergo CT scanning with higher than recommended radiation doses, potentially placing them at an increased carcinogenic risk. Fortunately, few RF patients required additional CT scans after PTC transfer. Finally, compliance with ACR radiation dose limit guidelines is better achieved at a PTC.

LEVEL OF EVIDENCE

Care management study, level IV.

Dose reduction in pediatric abdominal CT: use of iterative reconstruction techniques across different CT platforms

Dose reduction in children undergoing CT scanning is an important priority for the radiology community and public at large. Drawbacks of radiation reduction are increased image noise and artifacts, which can affect image interpretation. Iterative reconstruction techniques have been developed to reduce noise and artifacts from reduced-dose CT examinations, although reconstruction algorithm, magnitude of dose reduction and effects on image quality vary. We review the reconstruction principles, radiation dose potential and effects on image quality of several iterative reconstruction techniques commonly used in clinical settings, including 3-D adaptive iterative dose reduction (AIDR-3D), adaptive statistical iterative reconstruction (ASIR), iDose, sinogram-affirmed iterative reconstruction (SAFIRE) and model-based iterative reconstruction (MBIR). We also discuss clinical applications of iterative reconstruction techniques in pediatric abdominal CT.

Pediatric CT dose reduction for suspected appendicitis: a practice quality improvement project using artificial Gaussian noise--part 1, computer simulations

OBJECTIVE

The purpose of this study was to develop a departmental practice quality improvement project to systematically reduce CT doses for the evaluation of suspected pediatric appendicitis by introducing computer-generated gaussian noise.

MATERIALS AND METHODS

Two hundred MDCT abdominopelvic examinations of patients younger than 20 years performed with girth-based scanning parameters for suspected appendicitis were reviewed. Two judges selected 45 examinations in which the diagnosis of appendicitis was excluded (14, appendix not visualized; 31, normal appendix visualized). Gaussian noise was introduced into axial image series, creating five additional series acquired at 25-76% of the original dose. Two readers reviewed 270 image series for appendix visualization (4-point Likert scale and arrow localization). Volume CT dose index (CTDIvol) and size-specific dose estimate (SSDE) were calculated by use of patient girth. Confidence ratings and localization accuracy were analyzed with mixed models and nonparametric bootstrap analysis at a 0.05 significance level.

RESULTS

The mean baseline SSDE for the 45 patients was 16 mGy (95% CI, 12-20 mGy), and the corresponding CTDIvol was 10 mGy (95% CI, 4-16 mGy). Changes in correct appendix localization frequencies were minor. There was no substantial trend with decreasing simulated dose level (p = 0.46). Confidence ratings decreased with increasing dose reduction (p = 0.007). The average decreases were -0.27 for the 25% simulated dose (p = 0.01), -0.17 for 33% (p = 0.03), and -0.03 for 43% (p = 0.65).

CONCLUSION

Pediatric abdominal MDCT can be performed with 43% of the original dose (SSDE, 7 mGy; CTDIvol, 4.3 mGy) without substantially affecting visualization of a normal appendix.

Intra-abdominal sepsis--epidemiology, aetiology and management

Peritonitis is a progressive disease leading inexorably from local peritoneal irritation to overwhelming sepsis and death unless this trajectory is interrupted by timely and effective therapy. In children peritonitis is usually secondary to intraperitoneal disease, the nature of which varies around the world. In rich countries, appendicitis is the principal cause whilst in poor countries diseases such as typhoid must be considered in the differential diagnosis. Where resources are limited, the clinical diagnosis of peritonitis mandates laparotomy for diagnosis and source control. In regions with unlimited resources, radiological investigation, ultrasound, CT scan or MRI may be used to select patients for non-operative management. For patients with appendicitis, laparoscopic surgery has achieved results comparable to open operation; however, in many centres open operation remains the standard. In complicated peritonitis "damage control surgery" may be appropriate wherein source control is undertaken as an emergency with definitive repair or reconstruction awaiting improvement in the patient's general condition. Awareness of abdominal compartment syndrome is essential. Primary peritonitis in rich countries is seen in high-risk groups, such as steroid-dependent nephrotic syndrome patients, whilst in poor countries the at-risk population is less well defined and the diagnosis is often made at surgery.

Imaging of pediatric head injury in the emergency department

OBJECTIVES

Computed tomography (CT) is the standard for immediate imaging of head-injured children, but it uses radiation that predisposes to malignancy. The study goals were to describe imaging practices in this population and to identify barriers to rapid magnetic resonance imaging (MRI) use.

METHODS

A cross-sectional survey of physicians who care for pediatric patients in emergency departments was conducted. Survey questions included hospital characteristics, access to imaging technology, use of imaging studies, and use of radiation reduction practices.

RESULTS

A total of 459 eligible respondents completed the questionnaire, which represented a response rate of 24.1%. Almost all the respondents (97.7%) reported that radiation concerns influence clinical management of children and adolescents with head trauma. Head CT use was more frequently reported than MRI (55.3% vs 1.5% reported use in more than 10% of patients, respectively). Frequent CT use was associated with practice in community hospitals (P = 0.005), whereas pediatric residency training and pediatric volumes greater than 30,000 visits per year were associated with less frequent use (P = 0.015 and P = 0.028, respectively). In 94.5% of the respondents, reported CT was always available compared with 24.3% reporting MRI as always available (P < 0.001). Reported obstacles to MRI as a screening tool for head-injured children included limited scanner availability (93.5%), patient intolerance of MRI (87.2%), and longer acquisition times (83.3%).

CONCLUSIONS

Concerns about radiation exposure motivate change of practice in the management of head-injured children and adolescents. Head CT use is greater at hospitals with lower pediatric volumes, community hospitals, and by providers without pediatric residency training. Obstacles to increased use of MRI or head-injured children include availability, patient intolerance, and long scan acquisition times.

Optimizing the balance between radiation dose and image quality in pediatric head CT: findings before and after intensive radiologic staff training

OBJECTIVE

The purpose of this study was to assess the radiation dose and image quality of pediatric head CT examinations before and after radiologic staff training.

MATERIALS AND METHODS

Outpatients 1 month to 14 years old underwent 215 unenhanced head CT examinations before and after intensive training of staff radiologists and technologists in optimization of CT technique. Patients were divided into three age groups (0-4, 5-9, and 10-14 years), and CT dose index, dose-length product, tube voltage, and tube current-rotation time product values before and after training were retrieved from the hospital PACS. Gray matter conspicuity and contrast-to-noise ratio before and after training were calculated, and subjective image quality in terms of artifacts, gray-white matter differentiation, noise, visualization of posterior fossa structures, and need for repeat CT examination was visually evaluated by three neuroradiologists.

RESULTS

The median CT dose index and dose-length product values were significantly lower after than before training in all age groups (27 mGy and 338 mGy ∙ cm vs 107 mGy and 1444 mGy ∙ cm in the 0- to 4-year-old group, 41 mGy and 483 mGy ∙ cm vs 68 mGy and 976 mGy ∙ cm in the 5- to 9-year-old group, and 51 mGy and 679 mGy ∙ cm vs 107 mGy and 1480 mGy ∙ cm in the 10- to 14-year-old group; p < 0.001). The tube voltage and tube current-time values after training were significantly lower than the levels before training (p < 0.001). Subjective posttraining image quality was not inferior to pretraining levels for any item except noise (p < 0.05), which, however, was never diagnostically unacceptable.

CONCLUSION

Radiologic staff training can be effective in reducing radiation dose while preserving diagnostic image quality in pediatric head CT examinations.

Pediatric computed tomography imaging guideline

The use of computed tomography (CT) in pediatric diagnostic imaging is demanding generally, but when coupled with an awareness to limit the radiation dose associated with this imaging modality, the procedure becomes challenging. Although new techniques have been developed in line with the introduction of faster multidetector computed tomography (MDCT) scanners to aid radiation reduction, it still remains the responsibility of the clinical practitioner to ensure each examination request is justified and the scanning protocol and parameters selected are optimized to the individual patient's requirement. It is the purpose of this article to outline the basic principle of CT radiation dose optimization based on modification of scanning parameters and application of different imaging techniques.

Analysis of radiation exposure among pediatric trauma patients at national trauma centers

BACKGROUND

Injured children undergo radiologic studies as part of trauma evaluations. Children are more sensitive than adult patients to the effects of ionizing radiation. Few studies have described the radiation exposure to pediatric patients during trauma evaluations. We sought to describe the rate of use of radiology studies and to estimate the effective dose of radiation delivered to pediatric trauma patients presenting to trauma centers within the United States.

METHODS

We performed an analysis of pediatric patients younger than 19 years who presented to an American College of Surgery-verified trauma center in 2010 (National Trauma Data Bank). We excluded patients who were transferred from another facility, patients who died at the scene or those who presented to the emergency department dead on arrival. We examined the use of computed tomography (CT) and standard radiographs (x-ray). Radiologic studies were identified through common procedure codes (CPT). Using published criteria, we estimated the effective radiation dose per trauma patient.

RESULTS

Among the 84,863 eligible pediatric trauma patients, 26,360 (31.1%) underwent imaging with x-ray or CT. Of these patients, 17,321 (65.7%) were male, median age was 13.0 years (interquartile range, 6.0-17.0), and 20,965 (79.5%) had an Injury Severity Score (ISS) of less than 16. A total of 23,148 (27.4%) underwent CT. X-ray studies accounted for a small amount of exposure to radiation as compared with CT. Mean (SD) effective radiation exposure of patients imaged with CT was 12.0 (8.2) mSv. Younger children and those with increasing injury severity were exposed to higher doses of radiation (β = -0.04, p < 0.001).

CONCLUSION

The majority of radiation exposure to pediatric trauma patients is secondary to CT. Younger children and those with more severe injuries are exposed to higher doses of radiation. Pediatric trauma patients are exposed to levels of radiation, which could potentially lead to long-term harm.

LEVEL OF EVIDENCE

Epidemiologic study, level III.

Pediatric CT: strategies to lower radiation dose

OBJECTIVE

The introduction of MDCT has increased the utilization of CT in pediatric radiology along with concerns for radiation sequelae. This article reviews general principles of lowering radiation dose, the basic physics that impact radiation dose, and specific CT integrated dose-reduction tools focused on the pediatric population.

CONCLUSION

The goal of this article is to provide a comprehensive review of the recent literature regarding CT dose reduction methods, their limitations, and an outlook on future developments with a focus on the pediatric population. The discussion will initially focus on general considerations that lead to radiation dose reduction, followed by specific technical features that influence the radiation dose.

Pediatric traumatic brain injury and radiation risks: a clinical decision analysis

OBJECTIVE

To determine the optimal imaging strategy for young children with minor head injury considering health-related quality of life and radiation risk. In children with minor head trauma, the risk of missing a clinically important traumatic brain injury (ciTBI) must be weighed against the risk of radiation-induced malignancy from computed tomography (CT) to assess impact on public health.

STUDY DESIGN

We included children <2 years old with minor blunt head trauma defined by a Glasgow Coma Scale score of 14-15. We used decision analysis to model a CT-all versus no-CT strategy and assigned values to clinical outcomes based on a validated health-related quality of life scale: (1) baseline health; (2) non-ciTBI; (3) ciTBI without neurosurgery, death, or intubation; and (4) ciTBI with neurosurgery, death, or intubation >24 hours with probabilities from a prospective study of 10000 children. Sensitivity analysis determined the optimal management strategy over a range of ciTBI risk.

RESULTS

The no-CT strategy resulted in less risk with the expected probability of a ciTBI of 0.9%. Sensitivity analysis for the probability of ciTBI identified 4.8% as the threshold above which CT all becomes the preferred strategy and shows that the threshold decreases with less radiation. The CT all strategy represents the preferred approach for children identified as high-risk.

CONCLUSION

Among children <2 years old with minor head trauma, the no-CT strategy is preferable for those at low risk, reserving CT for children at higher risk.

"Black bone" MRI: a potential alternative to CT when imaging the head and neck: report of eight clinical cases and review of the Oxford experience

OBJECTIVE

The potential risks associated with ionising radiation are well documented. We have previously reported the "black bone" MRI sequence, useful when imaging cortical bone. The objective of this paper is to report our initial experience of this technique in patients undergoing imaging of the head and neck region.

METHODS

Using the departmental database those patients having had "black bone" sequences of the head and neck performed as part of their MRI examination in the preceding 5 years were identified. The radiological reports were reviewed to identify those cases where "black bone" or conventional MRI sequences had been performed in place of the requested CT, and the patient medical records for these cases were reviewed. Medical record review was also conducted for those cases where it was considered that the pathological condition requiring imaging would ordinarily be investigated with CT.

RESULTS

The "black bone" sequence had been performed in 69 patients as part of routine MRI of the head and neck. Of these, 67% (n=46) were performed in combination with CT imaging, the majority of cases being primary tumours. In four cases, an MRI was performed in place of the requested CT scan. We present eight clinical cases illustrating the potential benefits of the "black bone" sequence.

CONCLUSIONS

"Black bone" MRI offers a radiation-free method of imaging the head and neck, and has been successfully utilised in a range of benign and malignant conditions affecting this region. Advances in knowledge Adoption of this approach, where feasible, would be a significant advance in radiation protection.