Children, computed tomography radiation dose, and the As Low As Reasonably Achievable (ALARA) concept

Spontaneous pneumomediastinum on bedside ultrasound: case report and review of the literature

Spontaneous pneumomediastinum is a rare disease process with no clear etiology, although it is thought to be related to changes in intrathoracic pressure causing chest pain and dyspnea. We present a case of a 17-year-old male with acute chest pain evaluated initially by bedside ultrasound, which showed normal lung sliding but poor visualization of the parasternal and apical cardiac views due to significant air artifact, representing air in the thoracic cavity. The diagnosis was later verified by chest radiograph. We present a case report on ultrasound-diagnosed pneumomediastinum, and we review the diagnostic modalities to date.

Evidence-based assessment of severe pediatric traumatic brain injury and emergent neurocritical care

Pediatric traumatic brain injury accounts for approximately 474,000 emergency department visits, 37,000 hospitalizations, and 3,000 deaths in children 14 years and younger annually in the United States. Acute neurocritical care in children has advanced with specialized pediatric trauma centers and emergency medical services. This article reviews pediatric-specific diagnosis, management, and medical decision making related to the neurocritical care of severe traumatic brain injury.

Lower radiation exposure from body CT imaging for trauma at a dedicated pediatric hospital

PURPOSE

We compare radiation exposure from body CT imaging for blunt trauma performed at outside hospitals (OH) versus our children's hospital (CH).

METHODS

We performed a retrospective chart review of all children transferred to our facility for management of trauma after undergoing a body CT scan at an OH from June 2011 to August 2013. Radiation from OH images was compared to our CH by matching to age, gender, and nearest date. Radiation measures included dose length product (DLP), computed tomography dose index (CTDI), and size-specific dose estimate (SSDE).

RESULTS

Fifty-one children were transferred from 39 OH. Abdomen/pelvis and chest/abdomen/pelvis imaging was performed in 30 and 21 children, respectively. Demographics are shown in Table 1. Results are illustrated in Tables 2 and 3. Contrast was utilized in 45 (1 oral, 41 IV, 3 both) and 51 (49 IV, 2 both). CT scans were performed at OH and CH, respectively (P=0.03).

CONCLUSIONS

Children receive significantly less radiation exposure with body CT imaging for blunt trauma when performed at our dedicated CH. CT scans were significantly more likely to be ordered with appropriate contrast at our CH.

Statistical model based iterative reconstruction (MBIR) in clinical CT systems: experimental assessment of noise performance

PURPOSE

To reduce radiation dose in CT imaging, the statistical model based iterative reconstruction (MBIR) method has been introduced for clinical use. Based on the principle of MBIR and its nonlinear nature, the noise performance of MBIR is expected to be different from that of the well-understood filtered backprojection (FBP) reconstruction method. The purpose of this work is to experimentally assess the unique noise characteristics of MBIR using a state-of-the-art clinical CT system.

METHODS

Three physical phantoms, including a water cylinder and two pediatric head phantoms, were scanned in axial scanning mode using a 64-slice CT scanner (Discovery CT750 HD, GE Healthcare, Waukesha, WI) at seven different mAs levels (5, 12.5, 25, 50, 100, 200, 300). At each mAs level, each phantom was repeatedly scanned 50 times to generate an image ensemble for noise analysis. Both the FBP method with a standard kernel and the MBIR method (Veo(®), GE Healthcare, Waukesha, WI) were used for CT image reconstruction. Three-dimensional (3D) noise power spectrum (NPS), two-dimensional (2D) NPS, and zero-dimensional NPS (noise variance) were assessed both globally and locally. Noise magnitude, noise spatial correlation, noise spatial uniformity and their dose dependence were examined for the two reconstruction methods.

RESULTS

(1) At each dose level and at each frequency, the magnitude of the NPS of MBIR was smaller than that of FBP. (2) While the shape of the NPS of FBP was dose-independent, the shape of the NPS of MBIR was strongly dose-dependent; lower dose lead to a "redder" NPS with a lower mean frequency value. (3) The noise standard deviation (σ) of MBIR and dose were found to be related through a power law of σ ∝ (dose)(-β) with the component β ≈ 0.25, which violated the classical σ ∝ (dose)(-0.5) power law in FBP. (4) With MBIR, noise reduction was most prominent for thin image slices. (5) MBIR lead to better noise spatial uniformity when compared with FBP. (6) A composite image generated from two MBIR images acquired at two different dose levels (D1 and D2) demonstrated lower noise than that of an image acquired at a dose level of D1+D2.

CONCLUSIONS

The noise characteristics of the MBIR method are significantly different from those of the FBP method. The well known tradeoff relationship between CT image noise and radiation dose has been modified by MBIR to establish a more gradual dependence of noise on dose. Additionally, some other CT noise properties that had been well understood based on the linear system theory have also been altered by MBIR. Clinical CT scan protocols that had been optimized based on the classical CT noise properties need to be carefully re-evaluated for systems equipped with MBIR in order to maximize the method's potential clinical benefits in dose reduction and/or in CT image quality improvement.

Trends in the utilization of computed tomography and cardiac catheterization among children with congenital heart disease

Background/Purpose

Pediatric cardiac computed tomography (CT) is a noninvasive imaging modality used to clearly demonstrate the anatomical detail of congenital heart diseases. We investigated the impact of cardiac CT on the utilization of cardiac catheterization among children with congenital heart disease.

Methods

The study sample consisted of 2648 cardiac CT and 3814 cardiac catheterization from 1999 to 2009 for congenital heart diseases. Diagnoses were categorized into 11 disease groups. The numbers of examination, according to the different modalities, were compared using temporal trend analyses. The estimated effective radiation doses (mSv) of CT and catheterization were calculated and compared.

Results

The number of CT scans and interventional catheterizations had a slight annual increase of 1.2% and 2.7%, respectively, whereas that of diagnostic catheterization decreased by 6.2% per year. Disease groups fell into two categories according to utilization trend differences between CT and diagnostic catheterization. The increased use of CT reduces the need for diagnostic catheterization in patients with atrioventricular connection disorder, coronary arterial disorder, great vessel disorder, septal disorder, tetralogy of Fallot, and ventriculoarterial connection disorder. Clinicians choose either catheterization or CT, or both examinations, depending on clinical conditions, in patients with semilunar valvular disorder, heterotaxy, myocardial disorder, pericardial disorder, and pulmonary vein disorder. The radiation dose of CT was lower than that of diagnostic cardiac catheterization in all age groups.

Conclusion

The use of noninvasive CT in children with selected heart conditions might reduce the use of diagnostic cardiac catheterization. This may release time and facilities within the catheterization laboratory to meet the increasing demand for cardiac interventions.

Radiation exposure from head computed tomography scans in pediatric trauma

BACKGROUND

We have previously reported that children receive significantly less radiation exposure after abdominal and/or pelvis computed tomography (CT) scanning for acute appendicitis when performed at our children's hospital (CH) rather than at outside hospitals (OH). In this study, we compare the amount of radiation children receive from head CTs for trauma done at OH versus those at our CH.

METHODS

A retrospective chart review was performed on all children transferred to our hospital after receiving a head CT for trauma at an OH between July 2012 and December 2012. These children were then blindly case matched based on date, age, and gender to children at our CH.

RESULTS

There were 50 children who underwent head CT scans for trauma at 28 OH. There were 21 females and 29 males in each group. Average age was 7.01 ± 0.5 y at the OH and 7.14 ± 6.07 at our CH (P = 0.92). Average weight was 30.81 ± 4.69 kg at the OH and 32.69 ± 27.21 kg at our CH (P = 0.81). Radiation measures included dose length product (671.21 ± 22.6 mGycm at OH versus 786.28 ± 246.3 mGycm at CH, P = 0.11) and CT dose index (53.4 ± 2.26 mGy at OH versus 49.2 ± 12.94 mGy at CH, P = 0.56).

CONCLUSIONS

There is no significant difference between radiation exposure secondary to head CTs for traumatic injuries performed at OH and those at a dedicated CH.

Burden of diagnostic radiation exposure in children with sickle cell disease

Children with sickle cell disease (SCD) are repeatedly exposed to diagnostic radiation. We identified 938 children with SCD who had 9,246 radiographic tests. Mean number of tests/patient was 9.9 (95% CI: 8.9-10.9) over 8,817 patient-years. Mean rate was 1.5 tests/year (95% CI: 1.3-1.6). On average, a child with SCD will have 26.7 (95% CI: 24.1-29.3) radiographic tests by 18 years of age, and 5% will have ≥100 tests. Six percent have ≥3 CT scans, which may be associated with an increased risk of cancer. Strong consideration should be given to limiting the exposure of children with SCD to radiation.

Radiation exposure - how do CT scans for appendicitis compare between a free standing children's hospital and non-dedicated pediatric facilities?

BACKGROUND

We compare the amount of radiation children receive from CT scans performed at non-dedicated pediatric facilities (OH) versus those at a dedicated children's hospital (CH).

METHODS

Using a retrospective chart review, all children undergoing CT scanning for appendicitis at an OH were compared to children undergoing CT imaging for appendicitis at a CH between January 2011 and November 2012.

RESULTS

One hundred sixty-three children underwent CT scans at 42 different OH. Body mass index was similar between the two groups (21.00±6.49kg/m(2), 19.58±5.18kg/m(2), P=0.07). Dose length product (DLP) was 620±540.3 at OH and 253.78±211.08 at CH (P < 0.001). OH CT scans accurately diagnosed appendicitis in 81%, while CT scans at CH were accurate in 95% (P=0.026). CTDIvol was recorded in 65 patients with subset analysis showing CTDIvol of 16.98±15.58 and 4.89±2.64, a DLP of 586.25±521.59 and 143.54±41.19, and size-specific dose estimate (SSDE) of 26.71±23.1 and 3.81±2.02 at OH and CH, respectively (P<0.001).

CONCLUSION

Using SSDE as a marker for radiation exposure, children received 86% less radiation and had improved diagnostic accuracy when CT scans are performed at a CH.

Cervical spine computed tomography utilization in pediatric trauma patients

BACKGROUND

Guidelines for evaluating the cervical spine in pediatric trauma patients recommend cervical spine CT (CSCT) when plain radiographs suggest an injury. Our objective was to compare usage of CSCT between a pediatric trauma center (PTC) and referral general emergency departments (GEDs).

METHODS

Patient data from a pediatric trauma registry from 2002 to 2011 were analyzed. Rates of CSI and CSCT of patients presenting to the PTC and GED were compared. Factors associated with use of CSCT were assessed using multivariate logistic regression.

RESULTS

5148 patients were evaluated, 2142 (41.6%) at the PTC and 3006 (58.4%) at the GED. Groups were similar with regard to age, gender, GCS, and triage category. GED patients had a higher median ISS (14 vs. 9, p<0.05) and more frequent ICU admissions (44.3% vs. 26.1% p<0.05). CSI rate was 2.1% (107/5148) and remained stable. CSCT use increased from 3.5% to 16.1% over time at the PTC (mean 9.6% 95% CI=8.3, 10.9) and increased from 6.8% to 42.0% (mean 26.9%, CI=25.4, 28.4) at the GED. Initial care at a GED remained strongly associated with CSCT.

CONCLUSIONS

Despite a stable rate of CSI, rate of CSCT increased significantly over time, especially among patients initially evaluated at a GED.

The use of computed tomography in pediatrics and the associated radiation exposure and estimated cancer risk

IMPORTANCE

Increased use of computed tomography (CT) in pediatrics raises concerns about cancer risk from exposure to ionizing radiation.

OBJECTIVES

To quantify trends in the use of CT in pediatrics and the associated radiation exposure and cancer risk.

DESIGN

Retrospective observational study.

SETTING

Seven US health care systems.

PARTICIPANTS

The use of CT was evaluated for children younger than 15 years of age from 1996 to 2010, including 4 857 736 child-years of observation. Radiation doses were calculated for 744 CT scans performed between 2001 and 2011.

MAIN OUTCOMES AND MEASURES

Rates of CT use, organ and effective doses, and projected lifetime attributable risks of cancer. RESULTS The use of CT doubled for children younger than 5 years of age and tripled for children 5 to 14 years of age between 1996 and 2005, remained stable between 2006 and 2007, and then began to decline. Effective doses varied from 0.03 to 69.2 mSv per scan. An effective dose of 20 mSv or higher was delivered by 14% to 25% of abdomen/pelvis scans, 6% to 14% of spine scans, and 3% to 8% of chest scans. Projected lifetime attributable risks of solid cancer were higher for younger patients and girls than for older patients and boys, and they were also higher for patients who underwent CT scans of the abdomen/pelvis or spine than for patients who underwent other types of CT scans. For girls, a radiation-induced solid cancer is projected to result from every 300 to 390 abdomen/pelvis scans, 330 to 480 chest scans, and 270 to 800 spine scans, depending on age. The risk of leukemia was highest from head scans for children younger than 5 years of age at a rate of 1.9 cases per 10 000 CT scans. Nationally, 4 million pediatric CT scans of the head, abdomen/pelvis, chest, or spine performed each year are projected to cause 4870 future cancers. Reducing the highest 25% of doses to the median might prevent 43% of these cancers.

CONCLUSIONS AND RELEVANCE

The increased use of CT in pediatrics, combined with the wide variability in radiation doses, has resulted in many children receiving a high-dose examination. Dose-reduction strategies targeted to the highest quartile of doses could dramatically reduce the number of radiation-induced cancers.

Current attitudes of Turkish anesthesiologists to radiation exposure

PURPOSE

The aim of this study was to investigate the attitudes of anesthesiologists to radiation exposure and current safety practice in Turkey.

METHODS

The study enrolled anesthesiologists from all over Turkey, including all levels of academic degrees and all types of different institutions. Questionnaire forms were sent via e-mail to 505 anesthesiologists. The survey collected demographic data such as age, gender, position, and the institution at which the participant worked, and data about the frequency of radiation exposure during procedures and the participant's attitudes concerning radiation safety measures during these procedures.

RESULTS

The questionnaire forms were delivered to 491 anesthesiologists, and 301 (61.3 %) of these were returned. Of these, 9 had not completed the questionnaire because of a lack of exposure to radiation. Among the remaining 292 personnel, the weekly frequencies of radiation exposure were more than five times (36.7 %), one to five times (50.3 %), and less than once (13 %) per week, respectively. Only a few anesthesiologists regularly wore a lead apron (30.11 %) and a thyroid shield (11.3 %) during procedures involving radiation exposure.

CONCLUSIONS

This study demonstrated that nearly all anesthesiologists are regularly exposed to radiation and that few anesthesiologists in Turkey wear protective clothing, which is essential for radiation protection. Therefore, if it is not, increasing awareness about radiation protection should be an integral part of medical training and education.

Preliminary investigation of the diagnosis of neonatal congenital esophageal atresia using high-resolution ultrasonography: a report of three cases

OBJECTIVE

To investigate the clinical value of high-resolution ultrasonography (US) in the diagnosis of neonatal congenital esophageal atresia.

MATERIALS AND METHODS

Longitudinal or oblique mediastinal and abdominal scans were performed using a high-frequency, linear array Philip IU22 probe of 5-13MHz to measure the length and diameter of the upper and lower esophageal pouches, as well as the gap length.

RESULTS

Three neonates with esophageal atresia received surgical treatment. For each case, the length and diameter of the blind upper and/or lower esophageal pouches were measured by ultrasonography. The gaps in two of three cases were long (>3cm), and in one case, it was short (<2cm).

CONCLUSIONS

High-resolution ultrasonography can demonstrate clearly the upper and lower pouches, as well as wall features, and has a clear advantage in measuring the length of the lower esophageal pouch and the gap, which is impossible with plain radiography and esophagography. The drawback is that ultrasonography failed to clearly demonstrate the fistula between the esophagus and the trachea. Despite this, high-resolution ultrasonography is a promising modality in the clinical diagnosis of esophageal atresia.

Effective radiation dose in computed tomographic angiography of the chest and diagnostic cardiac catheterization in pediatric patients

Computed tomographic angiography (CTA) and cardiac catheterization are useful adjuncts to echocardiography for delineating cardiovascular anatomy in pediatric patients. These studies require ionizing radiation, and it is paramount to understand the amount of radiation pediatric patients receive when these tests are performed. Modern dosimetry methods facilitate the conversion of radiation doses of varying units into an effective radiation dose. To compare the effective radiation dose between nongated CTA of the chest and diagnostic cardiac catheterization in pediatric patients. This is a retrospective cohort study of patients of patients who underwent either nongated CTA of the chest or diagnostic cardiac catheterization between July 2009 and April 2010. Fifty patients were included in each group as consecutive samples at a single tertiary care center. An effective radiation dose (mSv) was formulated using conversion factors for each group. The median effective dose (ED) for the CTA group was 0.74 mSv compared with 10.8 mSv for the catheterization group (p < 0.0001). The median ED for children <1 year of age in the CTA group was 0.76 mSv compared with 13.4 mSv for the catheterization group (p < 0.0001). Nongated CTA of the chest exposes children to 15 times less radiation than diagnostic cardiac catheterization. Unless hemodynamic data are necessary, CTA of the chest should be considered in lieu of diagnostic cardiac catheterization in patients with known or presumed cardiac disease who need additional imaging beyond echocardiography.

Chest CT in infants and children

Computed tomography (CT) is a powerful and irreplaceable imaging technique in the evaluation of thoracic disease in infants and children. Recent advances in CT technology, with multi-detector equipment now widely available in most institutions, allowing a highly detailed evaluation of the chest in a short time period has resulted in expanding indications of chest CT in paediatric patients. Its improved diagnostic yield along with a widespread availability has also resulted in an increased number of CT examinations in children, not always with beneficial impact on patient management and outcome. Accordingly with the ALARA concept, a judicious and correct use of CT is strongly advisable in order to reduce unnecessary high dose radiation exposure. The objective of this paper is to review the use of chest CT in paediatric patients focused mainly on basic technical aspects and clinical applications in the evaluation of the lungs, mediastinum and chest wall.

Utility of plain radiographs in detecting traumatic injuries of the cervical spine in children

OBJECTIVE

The objective of this study was to estimate the sensitivity of plain radiographs in identifying bony or ligamentous cervical spine injury in children.

METHODS

We identified a retrospective cohort of children younger than 16 years with blunt trauma-related bony or ligamentous cervical spine injury evaluated between 2000 and 2004 at 1 of 17 hospitals participating in the Pediatric Emergency Care Applied Research Network. We excluded children who had a single or undocumented number of radiographic views or one of the following injuries types: isolated spinal cord injury, spinal cord injury without radiographic abnormalities, or atlantoaxial rotary subluxation. Using consensus methods, study investigators reviewed the radiology reports and assigned a classification (definite, possible, or no cervical spine injury) as well as film adequacy. A pediatric neurosurgeon, blinded to the classification of the radiology reports, reviewed complete case histories and assigned final cervical spine injury type.

RESULTS

We identified 206 children who met inclusion criteria, of which 127 had definite and 41 had possible cervical spine injury identified by plain radiograph. Of the 186 children with adequate cervical spine radiographs, 168 had definite or possible cervical spine injury identified by plain radiograph for a sensitivity of 90% (95% confidence interval, 85%-94%). Cervical spine radiographs did not identify the following cervical spine injuries: fracture (15 children) and ligamentous injury alone (3 children). Nine children with normal cervical spine radiographs presented with 1 or more of the following: endotracheal intubation (4 children), altered mental status (5 children), or focal neurologic findings (5 children).

CONCLUSIONS

Plain radiographs had a high sensitivity for cervical spine injury in our pediatric cohort.

Whole tumour first-pass perfusion using a low-dose method with 64-section multidetector row computed tomography in oesophageal squamous cell carcinoma

PURPOSE

To propose a low-dose method at tube current-time product of 50 mAs for whole tumour first-pass perfusion of oesophageal squamous cell carcinoma using 64-section multidetector row computed tomography (MDCT), and to assess the original image quality and accuracy of perfusion parameters.

MATERIALS AND METHODS

Fifty-nine consecutive patients with confirmed oesophageal squamous cell carcinomas were enrolled into our study, and underwent whole tumour first-pass perfusion scan with 64-section MDCT at 50 mAs. Image data were statistically reviewed focusing on original image quality demonstrated by image-quality scores and signal-to-noise (S/N) ratios; and perfusion parameters including perfusion (PF, in ml/min/ml), peak enhanced density (PED, in HU), time to peak (TTP, in seconds) and blood volume (BV, in ml/100 g) for the tumour. To test the interobserver agreement of perfusion measurements, perfusion analyses were repeatedly performed.

RESULTS

Original image-quality scores were 4.71±0.49 whereas S/N ratios were 5.21±2.05, and the scores were correlated with the S/N ratios (r=0.465, p<0.0001). Mean values for PF, PED, TTP and BV of the tumour were 33.27±24.15 ml/min/ml, 24.06±9.87 HU, 29.42±8.61 s, and 12.45±12.22 ml/100 g, respectively. Intraclass correlation coefficient between the replicated measurements of each perfusion parameter was greater than 0.99, and mean difference of the replicated measurements of each parameter was close to zero.

CONCLUSION

Whole tumour first-pass perfusion with 64-section MDCT at low-dose radiation could be reproducible to assess microcirculation in oesophageal squamous cell carcinoma without compromising subjective original image quality of the tumour.

Multislice CT in congenital bronchopulmonary malformations in children

Congenital bronchopulmonary malformations encompass a wide spectrum of pathologies involving the lungs, trachea and bronchi, pulmonary vessels, and oesophagus. These developmental lesions are often isolated, but the association of two or more anomalies is not infrequent. Contrast-enhanced multidetector computed tomography (MDCT), thanks to multiplanar and 3D reconstructions, allows for detailed studies of these malformations, achieving better accuracy compared with conventional techniques such as chest X-ray, fluoroscopy, ventilation and perfusion scintigraphy and ultrasonography. MDCT is characterised by fast data acquisition and does not require sedation in the majority of cases. The main drawbacks of MDCT are the use of ionising radiation and - in many cases -contrast media. Recently, improved CT scanners and optimised CT protocols have made available to children all the benefits of MDCT, thanks to a significant reduction in radiation dose and an improved risk-benefit ratio. The aim of our paper was to evaluate MDCT in children with bronchopulmonary malformations by reporting our experience (about 2,400 studies in 30 months with a 64-slice MDCT scanner) and comparing it with the available literature.

A pictorial review of imaging of abdominal tumours in adolescence

Neoplastic abdominal tumours, particularly those originating from embryonal tissue (such as hepatoblastoma and nephroblastoma) and neural crest cells (such as neuroblastoma), are well-documented in young children. Neoplasms of adulthood, most commonly carcinoma of different visceral organs, are also well-documented. Abdominal tumours in adolescence constitute a distinct pathological group. The radiological features of some of these tumours have been described only in isolated reports. The purpose of this pictorial essay was to review the imaging findings of various kinds of abdominal tumours in adolescent patients (with an age range of 10-16 years) who presented to the Children Cancer Center of our institution in the past 15 years. Some tumours, though rare, have characteristic imaging appearances (especially in CT) that enable an accurate diagnosis before definite histological confirmation.

Radiation exposure from pediatric head CT: a bi-institutional study

BACKGROUND

Medical radiation from CT should be kept as low as reasonably achievable (ALARA), particularly in young patients.

OBJECTIVE

To examine radiation dose from head CT in children in a trauma center (TC) and a regional children's hospital (RCH).

MATERIALS AND METHODS

A random sample of 240 children (0-3, 4-9, 10-14 years of age) from the TC were compared with a similar cohort from the RCH. All children had undergone at least one head CT scan without contrast enhancement; data from PACS and Department of Radiology Information System were used to estimate normalized effective dose (ED). Lifetime attributable risk of cancer incidence was estimated using the Biologic Effects of Ionizing Radiation (BEIR) VII report.

RESULTS

The mean normalized ED was significantly higher in the youngest children at the TC (2.74 mSv in those aged 0-3 years vs. 2.23 mSv in those aged 10-14 years; P<0.001) and at the RCH (2.44 mSv in those aged 0-3 years vs. 1.71 mSv in those aged 10-14 years; P<0.001). Each decreasing year of age was independently associated with a 0.06 mSv higher mean normalized ED (P<0.001). After adjusting for the age difference between the institutions, the mean normalized ED was 0.44 mSv lower at the RCH than at the TC across all ages (95% CI 0.31-0.58, P<0.001). A higher lifetime attributable risk of cancer was associated with younger age.

CONCLUSION

The radiation dose from head CT in children as defined by the normalized ED was highest in the youngest children and varied significantly between institutions in this bi-institutional study.

Slitlike ventricle syndrome: a life-threatening presentation

Severely increased intracranial pressure can be life-threatening in shunted children who do not experience ventricular enlargement. This condition is termed normal ventricular hydrocephalus and represents the most severe form of slit ventricle syndrome.

CASE REPORT

A 7-year-old girl with a repaired lumbosacral myelomeningocele and shunted at birth who presented with headache, vomiting, seizure, and deterioration of level of consciousness was admitted to the pediatric intensive care unit. Because her ventricles were small to slitlike on cranial computed tomographic (CT) scan, the shunt was presumed to be working. Although the cerebrospinal fluid analysis was normal, she received initial empirical treatment of viral encephalitis. Twenty-four hours after admission, she evolved with apnea and bradycardia, requiring ventilatory support. Repeated CT scans were unchanged from one study to the next. After 48 hours, her condition worsened, and cerebrospinal pressure during lumbar puncture reached more than 30 mm Hg despite the serial CT scan disclosing no ventricular enlargement. She underwent a shunt revision that showed that the catheter was occluded and had adhered to the ventricular wall. The shunt was replaced, resulting in dramatic neurological improvement. This report highlights a life-threatening condition involving chronically shunted children who present severe intracranial hypertension without ventriculomegaly and may often be neglected or unrecognized by emergency physicians or general neurosurgeons.

Pediatric liver tumors--a pictorial review

Hepatic masses constitute about 5-6% of all intra-abdominal masses in children. The majority of liver tumors in children are malignant; these malignant liver tumors constitute the third most common intra-abdominal malignancy in the pediatric age group after Wilms' tumor and neuroblastoma. Only about one third of the liver tumors are benign. A differential diagnosis of liver tumors in children can be obtained based on the age of the child, clinical information (in particular AFP) and imaging characteristics. The purpose of this review is to report typical clinical and imaging characteristics of benign and malignant primary liver tumors in children.

ALARA: is there a cause for alarm? Reducing radiation risks from computed tomography scanning in children

PURPOSE OF REVIEW

Radiation exposure from computed tomography is associated with a small but significant increase in risk for fatal cancer over a child's lifetime. This review aims to heighten awareness and spearhead efforts to reduce unnecessary computed tomography scans in children.

RECENT FINDINGS

The use of pediatric computed tomography continues to grow despite evidence on known risks of computed tomography-related radiation and induction of fatal cancers in children. More than 60 million computed tomography scans are estimated to be performed annually in the USA, with 7 million in children. Pediatric radiologists apply the practice of ALARA ('as low as reasonably achievable') to reduce radiation exposure. Education and advocacy directed to the referring clinician reinforce these principles. Radiation exposure may be further reduced by developing clinical pathways limiting computed tomography scanning and encourage alternate, nonradiation imaging modalities, such as ultrasound and magnetic resonance imaging. Although individual risk estimates are small, widespread use of computed tomography in the population may implicate a future public health issue.

SUMMARY

Advocacy by pediatric healthcare providers to promote intelligent dose reduction based on the principles of ALARA and the judicious use of computed tomography scanning is essential to foster the safest possible care of children.

Paediatric CT: the effects of increasing image noise on pulmonary nodule detection

BACKGROUND

A radiation dose of any magnitude can produce a detrimental effect manifesting as an increased risk of cancer. Cancer development may be delayed for many years following radiation exposure. Minimizing radiation dose in children is particularly important. However, reducing the dose can reduce image quality and may, therefore, hinder lesion detection.

OBJECTIVE

We investigated the effects of reducing the image signal-to-noise ratio (SNR) on CT lung nodule detection for a range of nodule sizes.

MATERIALS AND METHODS

A simulated nodule was placed at the periphery of the lung on an axial CT slice using image editing software. Multiple copies of the manipulated image were saved with various levels of superimposed noise. The image creation process was repeated for a range of nodule sizes. For a given nodule size, output images were read independently by four Fellows of The Royal College of Radiologists.

RESULTS

The overall sensitivities in detecting nodules for the SNR ranges 0.8-0.99, 1-1.49, and 1.5-2.35 were 40.5%, 77.3% and 90.3%, respectively, and the specificities were 47.9%, 73.3% and 75%, respectively. The sensitivity for detecting lung nodules increased with nodule size and increasing SNR. There was 100% sensitivity for the detection of nodules of 4-10 mm in diameter at SNRs greater than 1.5.

CONCLUSION

Reducing medical radiation doses in children is of paramount importance. For chest CT examinations this may be counterbalanced by reduced sensitivity and specificity combined with an increased uncertainty of pulmonary nodule detection. This study demonstrates that pulmonary nodules of 4 mm and greater in diameter can be detected with 100% sensitivity provided that the perceived image SNR is greater than 1.5.

Unintentional exposure of neonates to conventional radiography in the Neonatal Intensive Care Units

OBJECTIVE

To evaluate the extent of unintentional exposure to X-rays performed during routine diagnostic procedures in the Neonatal Intensive Care Units (NICUs).

STUDY DESIGN

During a 1-month period, 157 consecutive neonates from five level-III NICUs were recruited for this study. The mean birth weight was 1747+/-911 g (range: 564-4080 g), and gestational age was 31.6+/-3.6 weeks (range: 24-41 weeks). A total of 500 radiographs were performed including chest (68%), abdomen (17%) and combined chest and abdomen (15%). The average number of radiographs taken per infant was 4.2+/-3.6 (range: 1-21). Unintentional inclusion of body regions other than those ordered was determined by comparing the areas that should be included in the radiation field according to International recommendations, to those that appeared in the actual radiograph.

RESULT

A comparison of the recommended borders to the actual boundaries of the radiographs taken show an additional exposure to radiation in all three procedures: 85% of chest radiographs also included the whole abdomen, 64% of abdomen radiographs included both thigh and upper chest and 62% of chest and abdomen radiograph included the thigh. (The range in all procedures was from ankle to upper head.) Between 2 and 20% of the relevant targeted body tissues were not included in the exposed fields resulting in missing data. The gonads of both sexes were exposed in 7% in all chest X-rays. Among male infants, the testes were exposed in 31% of plain abdomen radiographs and 34% of chest and abdomen radiographs.

CONCLUSION

In the NICUs participating in the study, neonates are currently being exposed to X-ray radiation in nonrelevant body regions. Higher awareness and training of the medical teams and radiographers are required to minimize unnecessary exposure of newborns to ionizing radiation.

Utility of computed tomography of the head following head trauma in boys with haemophilia

The most serious site of bleeding for patients with haemophilia is the central nervous system. Intracranial haemorrhage (ICH) in patients with haemophilia can occur spontaneously or following mild head trauma however no guidelines exist for the approach to these patients. The goal of this review was to determine the utility of screening computed tomography (CT) of the head for patients with haemophilia who experience head trauma and to determine if the use of clinical criteria could allow a selective approach to radiographic imaging. In a retrospective study we reviewed the management of head trauma in a cohort of paediatric patients with haemophilia in a single institution. The cohort included males, ages birth to 18 years with haemophilia A or B who were followed at the haemophilia treatment center at The Children's Hospital of Philadelphia from 1994 to 2005. Between the years of 1994 and 2005, 97 patients were evaluated for head trauma for a total of 374 emergency department visits. There were 295 head CT scans performed to identify 9 (3%) episodes of intracranial bleeding. Fifty-six per cent of the patients with intracranial bleeding had no clinical signs or symptoms. The clinical outcome was excellent in all cases with no deaths or reported morbidity. In this cohort, a lack of symptoms and a normal neurological exam did not exclude ICH, especially in patients with severe haemophilia who were evaluated soon after a mild head trauma event suggesting the utility of early head CT imaging.

Pediatric Cardiac-Gated CT Angiography: Assessment of Radiation Dose

OBJECTIVE

The purpose of our study was to determine a dose range for cardiac-gated CT angiography (CTA) in children.

MATERIALS AND METHODS

ECG-gated cardiac CTA simulating scanning of the heart was performed on an anthropomorphic phantom of a 5-year-old child on a 16-MDCT scanner using variable parameters (small field of view; 16 x 0.625 mm configuration; 0.5-second gantry cycle time; 0.275 pitch; 120 kVp at 110, 220, and 330 mA; and 80 kVp at 385 mA). Metal oxide semiconductor field effect transistor (MOSFET) technology measured 20 organ doses. Effective dose calculated using the dose-length product (DLP) was compared with effective dose determined from measured absorbed organ doses.

RESULTS

Highest organ doses included breast (3.5-12.6 cGy), lung (3.3-12.1 cGy), and bone marrow (1.7-7.6 cGy). The 80 kVp/385 mA examination produced lower radiation doses to all organs than the 120 kVp/220 mA examination. MOSFET effective doses (+/- SD) were as follows: 110 mA: 7.4 mSv (+/- 0.6 mSv), 220 mA: 17.2 mSv (+/- 0.3 mSv), 330 mA: 25.7 mSv (+/- 0.3 mSv), 80 kVp/385 mA: 10.6 mSv (+/- 0.2 mSv). DLP effective doses for diagnostic runs were as follows: 110 mA: 8.7 mSv, 220 mA: 19 mSv, 330 mA: 28 mSv, 80 kVp/385 mA: 12 mSv. DLP effective doses exceeded MOSFET effective doses by 9.7-17.2%.

CONCLUSION

Radiation doses for a 5-year-old during cardiac-gated CTA vary greatly depending on parameters. Organ doses can be high; the effective dose may reach 28.4 mSv. Further work, including determination of size-appropriate mA and image quality, is important before routine use of this technique in children.

Multidetector row CT for imaging the paediatric tracheobronchial tree

The introduction of multidetector row computed tomography (MDCT) scanners has altered the approach to imaging the paediatric thorax. In an environment where the rapid acquisition of CT data allows general hospitals to image children instead of referring them to specialist paediatric centres, it is vital that general radiologists have access to protocols appropriate for paediatric applications. Thus a dramatic reduction in the delivered radiation dose is ensured with optimal contrast bolus delivery and timing, and inappropriate repetition of the scans is avoided. This article focuses on the main principles of volumetric CT imaging that apply generically to all MDCT scanners. We describe the reconstruction techniques for imaging the paediatric thorax and the low-dose protocols used in our institution on a 16-slice detector CT scanner. Examples of the commonest clinical applications are also given.

High-frequency ultrasound confirmation of positional plagiocephaly

OBJECT

Positional plagiocephaly has become an increasing problem for pediatricians and craniofacial specialists. Diagnosis is commonly based on history and clinical features, but may be difficult in some cases when characteristic features are missing and radiographic studies seem to be necessary. Near-field high-frequency ultrasound has been used to evaluate the sonographic findings of suture anatomy and confirm the diagnosis of positional plagiocephaly as well as provide information of prognostic value.

METHODS

The authors report on 100 pediatric patients between the ages of 2 and 13 months, who were admitted to their department since 2004 with an abnormal head shape suggesting nonsynostotic plagiocephaly (NSP). Suture anatomy was examined using a 7.5-MHz linear transducer and a Siemens Elegra ultrasound scanner by two independent investigators. Measurements of suture width and bone thickness were obtained, and the findings were correlated with clinical data as well as sonographic and histopathological findings in both normal and fused cranial sutures. Interobserver variability was assessed by means of paired t-tests. Linear regression analyses were used for correlating patient age with suture width and bone thickness. Patency of lambdoid sutures was confirmed in 99 cases in which the clinical findings suggested NSP. Morphological characteristics of the sutures--interosseous hypoechoic areas between hyperechoic bone plates--were comparable to those of normal cranial sutures. In one patient, partial synostosis was diagnosed. Overlapping hyperechoic bone plates were found in 51 patients on the affected side of the skull and in 36 patients on the unaffected side. Suture width decreased over time from 6.5 to 2 mm, and thickness of bone in the affected area increased from 0.6 to 1.2 mm until the age of 13 months. The method was found to be limited by age (upper limit 13 months) and anatomical variations but did not show any interobserver variability (p < 0.05).

CONCLUSIONS

High-frequency ultrasound is a relatively inexpensive, safe, and easy-to-use tool for confirming the diagnosis of positional plagiocephaly and excluding true synostosis. Overlapping bone plates may be seen on the affected side of the skull in a majority of plagiocephalic patients, but this finding seems to have no prognostic value regarding early fusion of sutures and therefore should not affect treatment decisions. With its lack of interobserver variability and the advantage of not involving ionizing radiation, sonography has the potential to be a standard modality for investigating plagiocephaly in infants and should be offered in craniofacial outpatient clinics.

Pediatric ophthalmic computed tomographic scanning and associated cancer risk

PURPOSE

To review pediatric neuroimaging studies of the head and orbit and the radiation-induced cancer risk associated with computed tomography in light of recent attention to pediatric radioimaging by the US Food and Drug Administration, the National Cancer Institute, pediatricians, and radiologists.

DESIGN

Perspective.

METHODS

Literature review.

SETTING

Institutional.

PATIENT POPULATION

Pediatric ophthalmic patients requiring neuroimaging studies. INTERVENTION/PROCEDURE: Review of the current literature.

MAIN OUTCOME MEASURES

After review of the current literature and discussion of the related issues, recommendations are made for pediatric neuroimaging studies of the head and orbit.

RESULTS

Computed tomography (CT) of the head and orbit may be performed in children with the appropriate indications as long as the radiation exposure is minimized.

CONCLUSIONS

Information obtained from CT scans of the head and orbit may determine or affect management in the pediatric ophthalmic population. Because of the concern of cancer induced by radiation exposure in children, neuroimaging modalities without radiation exposure, such as magnetic resonance imaging or ultrasound, may be considered. However, when CT is indicated, it is reasonable and acceptable to perform CT of the head and orbit while minimizing the radiation exposure, thereby adhering to the "ALARA" (as low as reasonably achievable) policy recommended by the US Food and Drug Administration. Further studies of the actual radiation dose delivered during pediatric CT of the head and orbit and the true incidence of radiation-induced cancers after scans are warranted.

Progress in sinonasal imaging

Imaging of sinonasal structures has evolved from standard radiographs to the much more complicated and informative techniques used today. The plain radiograph was useful when the surgical techniques practiced were primarily aimed at the maxillary and frontal sinuses. With a better understanding of the mucociliary clearance of the nasal cavity and the paranasal sinuses, the surgical technique was shifted to the ethmoid sinuses and became more focal, thus needing a better understanding and display of the intricate morphology of the nasal cavity and paranasal sinuses. Polytomography was a step above plain radiographs and was first used in the display of the regional anatomy for the development of functional endoscopic sinus surgery. Polytomography was quickly replaced by computed tomography, as this imaging technique provides a much more detailed view of the sinonasal architecture than does polytomography. Magnetic resonance imaging has also shown usefulness in imaging this morphological area, as it provides better soft tissue resolution, but it does not allow good visualization of bony structures. Newer computer systems with software capable of reconstructing the digitized information into a 3-dimensional display further enhance our understanding of the regional morphology and afford an improved means of correlating the imaging and endoscopic information. Furthermore, stereotactic navigation systems allow surgeons the ability to visualize the endoscope-instrument tip position, as instruments are actively being used during surgery, on the computed tomographic and/or magnetic resonance images. There is a persistent trend toward reducing the size of the imaging equipment to render it more mobile (computed tomography) and adapt it for operating room use.

Ultrasound in the Diagnosis of Craniosynostosis

Diagnosis of craniosynostosis is based on clinical aspects but may be difficult in some cases where characteristic features are missing and radiographic imaging is necessary. In this context near-field high-frequency ultrasound has been used to evaluate the sonographic characteristics of synostotic sutures and its potential confirming the correct diagnosis. Sutures of 26 infants, aged 2-7 months, were investigated by ultrasound (Siemens Elegra, 7.5 MHz linear scanner). Sonographic features of synostotic sutures were correlated to CT imaging and compared to the sonographic and histopathological findings of normal cranial sutures. Hyperechogenic bridging of sutures with or without ridging were the characteristic aspects of synostotic sutures. All 26 patients could be reliable diagnosed showing partial (n = 21) or total fusion (n = 5) of one or more sutures consisting with craniosynostosis. Length of synostosis was identified exactly by sonography and imaging found to enable a classification of ultrastructural details of bony and soft tissue next to the synostotic suture. Ultrasound is a less expensive, nonradiating and easy-to-handle tool ensuring the diagnosis of craniosynostosis. Sonography offers the potential to be a standard investigation for infants with head deformities suspecting a suture pathology and has been therefore integrated in our craniofacial outpatient clinic as a daily routine method.

Paediatric and adult computed tomography practice and patient dose in Australia

The current practice for CT scanning of paediatric patients in Australia has been assessed through a survey sent to the site of all CT scanners licensed in New South Wales and all dedicated children's hospitals in Australia. The survey addressed demographic details, CT scanner details and scanning parameters for four imaging scenarios (brain CT, chest CT, abdomen/pelvis CT and high-resolution chest CT for three different age groups (8 weeks, 5-7 years and adult patients). The effective dose for each imaging scenario and age group was calculated and compared for 52 sites representing 53 CT scanners. For any age group and imaging scenario, there was a large spread of effective dose. For comparable CT examinations, the effective dose varied by up to 36-fold between centres. There was a clear trend for centres that frequently carry out CT scans on paediatric patients to have the lowest radiation doses. Four age group/imaging scenarios showed significantly lower effective doses for hospital-based CT than for nonhospital sites. There was also a trend for doses to be lower at dedicated paediatric centres. Effective dose was closely associated with mAs, with most centres using lower mAs for younger patients, but few centres reduced the kVp for paediatric patients. The results of the survey emphasize the need for continuing education and protocol review, particularly in paediatric CT examinations, in a complex and fast changing environment.

Appendicitis in Children: Low-Dose CT with a Phantom-based Simulation Technique—Initial Observations

PURPOSE

To retrospectively determine the accuracy of low-dose (20-mAs) computed tomography (CT) in the diagnosis of acute appendicitis in children by using a technique that enables the simulation of human CT scans acquired at a lower tube current given the image acquired at a standard dose.

MATERIALS AND METHODS

Institutional review board approval was obtained, informed consent was not required, and the study was HIPAA compliant. The authors reviewed 100 standard-dose pediatric abdominal-pelvic CT scans (50 positive and 50 negative scans) obtained in 100 patients and corresponding simulated low-dose (20-mAs) scans. The standard-dose scans were obtained for evaluation in patients suspected of having appendicitis. Scans were reviewed in randomized order by four experienced pediatric radiologists. The patients with positive findings included 21 girls (mean age, 9.2 years) and 29 boys (mean age, 8.4 years). The patients with negative findings included 28 girls (mean age, 9.2 years) and 22 boys (mean age, 8.4 years). Simulation was achieved by adding noise patterns from repeated 20-mAs scans of a pediatric pelvis phantom to the original scans obtained with a standard tube current. Observers recorded their confidence in the diagnosis of appendicitis by using a six-point scale. Dose-related changes were analyzed with generalized estimating equations and the nonparametric sign test.

RESULTS

There was a statistically significant (P < .001, sign test) decrease in both sensitivity and accuracy with a lower tube current, from 91.5% with the original tube current to 77% with the lower tube current. A low dose was the only statistically significant (P < .001) risk factor for a false-negative result. The specificity was unchanged at 94% for both the images obtained with the original tube current and the simulated low-dose images. The overall accuracy decreased from 92% with the original dose to 86% with the low dose.

CONCLUSION

Preliminary findings indicate that it is feasible to optimize the CT dose used to evaluate appendicitis in children by using phantom-based computer simulations.

Lack of radiological awareness among physicians working in a tertiary-care cardiological centre

BACKGROUND

Medical irradiation is the most important artificial source of exposure to ionising radiations in Europe and implies biorisks.

AIM

To assess the level of radiological awareness in a tertiary-care referral centre of adult-pediatric cardiological excellence.

METHODS

One hundred physicians (31 women, age=41+/-8 years) were polled with a simple, one-page, multiple choice questionnaire. Twenty-five physicians worked in a pediatric, 75 in an adult cardiology centre.

RESULTS

Eighty-nine of the polled physicians wrongly estimated the contribution of nuclear and radiological tests in overall radiation exposure of average US inhabitant as <0.01% (36% of physicians) or <1% (31%) or <10% (22%) (correct answer given by 11% of physicians: >10%). Ninety-five physicians wrongly estimated the risk of fatal cancer associated with a stress myocardial perfusion scintigraphy procedure as "zero" (48%) or "<1 in 10 million"(19%) or "<1 in 1 million" (28%) (correct answer given by 5%: >1 in 10,000 tests). Seventy-one wrongly estimated the dose exposure of a myocardial stress perfusion scintigraphy as equal to one (13%), or one-half (9%), or three times (49%) that of a chest X-ray (correct answer given by 29%: 500 times). The average level of radiological awareness was not correlated to the number of radiological-nuclear exams performed/prescribed per year and to the type of (adult or pediatric) working environment.

CONCLUSION

Physicians working in an adult and pediatric cardiological environment of excellence are largely unaware of environmental impact, biorisks and dose exposure of the ionising exams they prescribe and/or perform daily.

CT dose reduction in children

World wide, the number of CT studies in children and the radiation exposure by CT increases. The same energy dose has a greater biological impact in children than in adults, and scan parameters have to be adapted to the smaller diameter of the juvenile body. Based on seven rules, a practical approach to paediatric CT is shown: Justification and patient preparation are important steps before scanning, and they differ from the preparation of adult patients. The subsequent choice of scan parameters aims at obtaining the minimal signal-to-noise ratio and volume coverage needed in a specific medical situation; exposure can be divided in two aspects: the CT dose index determining energy deposition per rotation and the dose-length product (DLP) determining the volume dose. DLP closely parallels the effective dose, the best parameter of the biological impact. Modern scanners offer dose modulation to locally minimise exposure while maintaining image quality. Beyond the selection of the physical parameters, the dose can be kept low by scanning the minimal length of the body and by avoiding any non-qualified repeated scanning of parts of the body. Following these rules, paediatric CT examinations of good quality can be obtained at a reasonable cost of radiation exposure.

Magnetic Resonance Imaging of Abdominal Masses in the Pediatric Patient

Magnetic resonance (MR) plays a unique role in the diagnosis and management of pediatric abdominal masses. The "as low as reasonably achievable" (ALARA) radiation dose of CT is zero when substituted by MR. Whole body MR may also compete with PET imaging to stage abdominal tumors. Specific advantages of MR include determination of resectability of hepatic tumors using MRI and MRA; staging of neuroblastoma in the bone marrow, lymph nodes, liver, and spinal canal; response of bilateral Wilms tumor and nephroblastomatosis; detection of pelvic tumors with sagittal sectioning, and peritoneal tumors with contrast enhancement.

Electron beam CT scan is a valuable and safe imaging tool for the pediatric surgical patient

PURPOSE

Electron beam computed tomography (EBCT) is a relatively new technology that has been used primarily to detect coronary artery calcification in adult patients. EBCT has several potential advantages over traditional CT: (1) fast acquisition times resulting in less need for sedation, (2) decreased radiation exposure, and (3) robust software enabling real-time interactive 3-dimensional visualization of anatomic relationships. In this series of case reports, the authors describe their initial experience with the use of EBCT in pediatric noncardiac imaging.

METHODS

Children with a variety of thoracic and abdominal disease processes were evaluated by EBCT.

RESULTS

All patients underwent EBCT scanning without the need for sedation, and 3-dimensional images of the data sets were rendered in minutes after their acquisition. The diagnostic images provided equivalent spatial resolution to the multislice CT scanner but without motion artifacts and lower radiation exposure.

CONCLUSIONS

EBCT is a safe, effective, and user- and patient-friendly alternative to traditional CT in the care of pediatric surgical diseases. The diagnostic yield of EBCT will continue to improve with new technologic advances and clinical experience.

Low-dose chest CT: optimizing radiation protection for patients

OBJECTIVE

The aim of our study was to evaluate CT scanning protocols to determine how best to minimize patient exposure to ionizing radiation while maintaining sufficient image quality to detect pulmonary diseases.

SUBJECT AND METHODS

The CT dose index (CTDI) was determined by scanning an acrylic phantom at various tube current-time products (7.5-115 mAs). Image quality was evaluated by comparing the homogeneity and noise level of CT scans obtained in the acrylic phantom with those obtained in a water-equivalent phantom. The CT scans obtained at various milliampere-second settings in patients with nodules or diffuse opacifications were assessed. The relationships between the CTDI and the image quality of the CT scans (noise level and artifacts) were established.

RESULTS

The reduction of a conventional tube current-time product (115 mAs) by 65%, 78%, or 93.5% can decrease the CTDI by 60%, 70%, or 85%, respectively. In correlating the image quality of each CT scan to the milliampere-second settings used to obtain it, we found that homogeneity decreased as milliampere-second settings decreased, whereas the noise level increased as milliampere-second settings decreased. For both 8- and 3-mm slice thicknesses, the homogeneity of CT scans acquired at 7.5 mAs or greater was within the acceptable range (< 4 H). However, the noise level of CT scans remained within the acceptable range (< 0.35%) when 25 mAs or greater was used. The evaluation of the image quality of the patients' CT scans indicated no statistical significance in image quality rating between the scans obtained at 25 mAs and those obtained at 115 mAs (p > 0.01).

CONCLUSION

Low-dose (i.e., 40 or 25 mAs) helical chest CT produced satisfactory image quality and reduced the CTDI, thereby maximally protecting patients from radiation exposure.