Variation in Pediatric Head CT Imaging Protocols in Washington State

Prevalence of "One-Off Events" in Radiology: Implications for Radiology in Episode-Based Alternative Payment Models

OBJECTIVE

As reimbursement mechanisms become more value-based, there are questions about the applicability of these mechanisms for nonepisodic care, particularly care provided by nonpatient-facing specialists, for example, radiologists. Accordingly, this study examined the prevalence of nonepisodic care-one-off events-in diagnostic radiology.

METHODS

We conducted a multiyear (2015-2019) retrospective study of diagnostic imaging using a large commercial payer database including commercial insurance and Medicare Advantage. Using a 12-month evaluation period starting with the day of the initial imaging study/studies, we categorized imaging studies as one-off events if there were no additional studies (beyond the first day of the evaluation period) for the next 12 months in the same body region. We also evaluated an alternative, more stringent definition of a one-off event: the only imaging study during the 12-month evaluation period. We computed the percentage of one-off events overall and by body region.

RESULTS

We found that one-off events comprised 33.2%-45.8% of imaging studies depending on whether one-off events are defined as the only study in the evaluation period or imaging only on the first day of the evaluation period, respectively. This share varied widely by body region: highest for cardiac (80.9%-87.7%) and lower for chest (26.8%-35.2%). By place-of-service, the proportion was lowest for the inpatient (12.9%-29.1%) and long-term care settings (18.6%-30%).

DISCUSSION

Given the sizeable share of imaging studies categorized as one-off events, much of radiologists' workload falls outside of the framework of episodic measurement tools and value-based payment models.

Pitfalls in the interpretation of pediatric head CTs: what the emergency radiologist needs to know

Pediatric radiology studies can be some of the most anxiety-inducing imaging examinations encountered in practice. This can be in part due to the wide range of normal anatomic appearances inherent to the pediatric population that create potential interpretive pitfalls for radiologists. The pediatric head is no exception; for instance, the inherent greater water content within the neonatal brain compared to older patients could easily be mistaken for cerebral edema, and anatomic variant calvarial sutures can be mistaken for skull fractures. This article reviews potential pitfalls emergency radiologists may encounter in practice when interpreting pediatric head CTs, including trauma, extra-axial fluid collections, intra-axial hemorrhage, and ventriculoperitoneal shunt complications.

Variability in image quality and radiation dose within and across 97 medical facilities

Purpose: To characterize variability in image quality and radiation dose across a large cohort of computed tomography (CT) examinations and identify the scan factors with the highest influence on the observed variabilities. Approach: This retrospective institutional-review-board-exempt investigation was performed on 87,629 chest and abdomen-pelvis CT scans acquired for 97 facilities from 2018 to 2019. Images were assessed in terms of noise, resolution, and dose metrics (global noise, frequency in which modulation transfer function is at 0.50, and volumetric CT dose index, respectively). The results were fit to linear mixed-effects models to quantify the variabilities as affected by scan parameters and settings and patient characteristics. A list of factors, ranked by t -value with p < 0.05 , was ascertained for each of the six mixed effects models. A type III p -value test was used to assess the influence of facility. Results: Across different facilities, image quality and dose were significantly different ( p < 0.05 ), with little correlation between their mean magnitudes and consistency (Pearson's correlation coefficient < 0.34 ). Scanner model, slice thickness, recon field-of-view and kernel, mAs, kVp, patient size, and centering were the most influential factors. The two body regions exhibited similar rankings of these factors for noise (Spearman's correlation coefficient = 0.76 ) and dose (Spearman's correlation coefficient = 0.86 ) but not for resolution (Spearman's correlation coefficient = 0.52 ). Conclusions: Clinical CT scans can vary in image quality and dose with broad implications for diagnostic utility and radiation burden. Average scan quality was not correlated with interpatient scan-quality consistency. For a given facility, this variability can be quite large, with magnitude differences across facilities. The knowledge of the most influential factors per body region may be used to better manage these variabilities within and across facilities.

Noncontrast Head CT in Children: National Variation in Radiation Dose Indices in the United States

BACKGROUND AND PURPOSE

Radiologists should manage the radiation dose for pediatric patients to maintain reasonable diagnostic confidence. We assessed the variation in estimated radiation dose indices for pediatric noncontrast head CT in the United States.

MATERIALS AND METHODS

Radiation dose indices for single-phase noncontrast head CT examinations in patients 18 years of age and younger were retrospectively reviewed between July 2011 and June 2016 using the American College of Radiology CT Dose Index Registry. We used the reported volume CT dose index stratified by patient demographics and imaging facility characteristics.

RESULTS

The registry included 295,296 single-phase pediatric noncontrast head CT studies from 1571 facilities (56% in male patients and 53% in children older than 10 years of age). The median volume CT dose index was 33 mGy (interquartile range = 22-47 mGy). The volume CT dose index increased as age increased. The volume CT dose index was lower in children's hospitals (median, 26 mGy) versus academic hospitals (median, 32 mGy) and community hospitals (median, 40 mGy). There was a lower volume CT dose index in level I and II trauma centers (median, 27 and 32 mGy, respectively) versus nontrauma centers (median, 40 mGy) and facilities in metropolitan locations (median, 30 mGy) versus those in suburban and rural locations (median, 41 mGy).

CONCLUSIONS

Considerable variation in the radiation dose index for pediatric head CT exists. Median dose indices and practice variations at pediatric facilities were both lower compared with other practice settings. Decreasing dose variability through proper management of CT parameters in pediatric populations using benchmarks generated by data from registries can potentially decrease population exposure to ionizing radiation.

Report of the ACR's Economics Committee on Value-Based Payment Models

A major outcome of the current health care reform process is the move away from unrestricted fee-for-service payment models toward those that are based on the delivery of better patient value and outcomes. The authors' purpose, therefore, is to critically evaluate and define those components of the overall imaging enterprise that deliver meaningful value to both patients and referrers and to determine how these components might be measured and quantified. These metrics might then be used to lobby providers and payers for sustainable payment solutions for radiologists and radiology services. The authors evaluated radiology operations and services using the framework of the imaging value chain, which divides radiology service into a number of discrete value-added activities, which ultimately deliver the primary product, most often the actionable report for diagnostic imaging or an effective outcome for interventional radiology. These value activities include scheduling and imaging appropriateness and stewardship, patient preparation, protocol design, modality operations, reporting, report communication, and clinical follow-up (eg, mammography reminder letters). Two further categories are hospital or health care organization citizenship and examination outcome. Each is discussed in turn, with specific activities highlighted.

Targeted CT Dose Reduction Using a Novel Dose Metric and the American College of Radiology Dose Index Registry: Application to Thoracic CT Angiography

OBJECTIVE

The purpose of this article is to illustrate the use of the American College of Radiology Dose Index Registry data with a novel measurement of exposure to guide quality improvement efforts.

MATERIALS AND METHODS

Using information from the Dose Index Registry report covering July through December 2012, we examined our relative ranking compared with the national median CT dose for the 20 most frequently performed examinations at our institution. The total exposure variance, defined as the difference between institutional and median national dose multiplied by the local examination frequency and expressed in units of mGy-persons, was calculated. Using this metric, two examinations were selected for investigation: pulmonary and thoracic CT angiography (CTA). Protocol modifications were implemented, and postintervention dose data were assessed from the report 1 year later.

RESULTS

As indicated by size-specific dose estimates (SSDEs), the 2012 pulmonary CTA was within the national interquartile range; however, total exposure variance analysis showed that it presented the greatest opportunity for improvement on a population basis. Thoracic CTA was a top quartile examination and offered the second highest potential savings. After protocol modification, the average pulmonary CTA SSDEs decreased by 16%, for a population exposure savings of 1776 mGy-persons in the 2013 report. Average thoracic CTA SSDEs decreased by 44%, for a population exposure savings of 1050 mGy-persons.

CONCLUSION

Total exposure variance analysis can increase the usefulness of Dose Index Registry data by relating per-examination dose differences to the local examination frequency. This study exhibited reduction of dose metrics for two commonly performed examinations.

Variation in Pediatric Cervical Spine Computed Tomography Radiation Dose Index

OBJECTIVES

The objective was to evaluate variation in the current estimated radiation dose index for pediatric cervical spine (c-spine) computed tomography (CT) examinations.

METHODS

This was a retrospective analysis of pediatric (age younger than 19 years) c-spine CT examinations from the American College of Radiology Dose Index Registry, July 2011 through December 2014. We used the volume CT dose index (CTDIvol) as the radiation dose estimate and used summary statistics to describe patient and hospital characteristics.

RESULTS

There were 12,218 pediatric CT c-spine examinations performed across 296 participating hospitals. Fifty-six percent were in male patients, and 79% were in children older than 10 years. Most hospitals (55%) were community hospitals without trauma designations, and the largest proportion of examinations (41%) were performed at these hospitals. The median CTDIvol was 15 mGy (interquartile range = 9 to 23 mGy) representing a more than 2.5-fold difference between the 25th and 75th percentiles. Pediatric hospitals (both trauma and nontrauma centers) delivered the lowest CTDIvol across all age groups and showed the least amount of variability in dose.

CONCLUSIONS

There is significant variation in the radiation dose index for pediatric c-spine CT examinations. Pediatric hospitals practice at lower CT dose estimates than other hospitals. Individual hospitals should examine their practices in an effort to ensure standardization and optimization of CT parameters to minimize radiation exposures to pediatric patients.

Establishment of diagnostic reference levels in computed tomography for paediatric patients in Sudan: a pilot study

Paediatric patients are recognised to be at higher risk of developing radiation-induced cancer than adults. The purpose of this pilot study was to evaluate the radiation doses to paediatric patients during computed tomography (CT) procedures in order to propose local diagnostic reference levels (DRLs). A total of 296 patients (aged 6-10 y) were investigated in 8 hospitals equipped with 64-, 16- and dual-slice CT machines. The mean dose length product values were 772, 446 and 178 mGy cm for head, abdomen and chest, respectively. Imaging protocols were not adapted to the patient's weight in certain CT machines. The results confirmed that paediatric patients are exposed to an unnecessary radiation dose. The established DRLs were higher than those available in other countries. This study showed the need for harmonisation of the practice in CT departments and radiation dose optimisation.

Variation in CT pediatric head examination radiation dose: results from a national survey

OBJECTIVE. The purpose of this article is to examine the variation in radiation dose, CT dose index volume (CTDIvol), and dose-length product (DLP) for pediatric head CT examinations as a function of hospital characteristics across the United States. MATERIALS AND METHODS. A survey inquiring about hospital information, CT scanners, pediatric head examination protocol, CTDIvol, and DLP was mailed to a representative sample of U.S. hospitals. Follow-up mailings were sent to nonrespondents. Descriptive characteristics of respondents and nonrespondents were compared using design-based Pearson chi-square tests. Dose estimates were compared across hospital characteristics using Bonferroni-adjusted Wald test. Hospital-level factors associated with dose estimates were evaluated using multiple linear regressions and modified Poisson regression models. RESULTS. Surveys were sent out to 751 hospitals; 292 responded to the survey, of which 253 were eligible (35.5% response rate, calculated as number of hospitals who completed surveys [n = 253] divided by sum of number who were eligible and initially consented [n = 712] plus estimated number who were eligible among those who refused [n = 1]). Most respondents reported using MDCT scanners (99.2%) and having a dedicated pediatric head CT protocol (93%). Estimated mean reported CTDIvol values were 27.3 mGy (95% CI, 24.4-30.1 mGy), and DLP values were 390.9 mGy × cm (95% CI, 346.6-435.1 mGy × cm). These values did not vary significantly by region, trauma level, teaching status, CT accreditation, number of CT scanners, or report of a dedicated pediatric CT protocol. However, estimated CTDIvol reported by children's hospitals was 19% lower than that reported by general hospitals (p < 0.01). CONCLUSION. Most hospitals (82%) report doses that meet American College of Radiology accreditation levels. However, [corrected] the mean CTDI(vol) at children's hospitals was approximately 7 mGy (21%, adjusted for covariates), lower than that at nonchildren's hospitals.

Hospital-level factors associated with use of pediatric radiation dose-reduction protocols for head CT: results from a national survey

OBJECTIVES

To examine hospital-level factors associated with the use of a dedicated pediatric dose-reduction protocol and protective shielding for head CT in a national sample of hospitals.

METHODS

A mixed-mode (online and paper) survey was administered to a stratified random sample of US community hospitals (N = 751). Respondents provided information on pediatric head CT scanning practices, including use of a dose-reduction protocol. Modified Poisson regression analyses describe the relative risk (RR) of not reporting the use of a pediatric dose-reduction protocol or protective shielding; multivariable analyses adjust for census region, trauma level, children's hospital status, and bed size.

RESULTS

Of hospitals that were contacted, 38 were ineligible (no CT scanner, hospital closed, do not scan infants), 1 refused, and 253 responded (35.5% response rate). Across all hospitals, 92.6% reported using a pediatric dose-reduction protocol. Modified Poisson regression showed that small hospitals (0-50 beds) were 20% less likely to report using a protocol than large hospitals (>150 beds) (RR: 0.80, 95% confidence interval [CI]: 0.65-0.99; adjusted for covariates). Teaching hospitals were more likely to report using a protocol (RR: 1.10, 95% CI: 1.02-1.19; adjusted for covariates). After adjusting for covariates, children's hospitals were significantly less likely to report using protective shielding than nonchildren's hospitals (RR: 0.64, 95% CI: 0.56-0.73), though this may be due to more advanced scanner type.

CONCLUSION

Results from this study provide guidance for tailored educational campaigns and quality improvement interventions to increase the adoption of pediatric dose-reduction efforts.

Toward Large-Scale Process Control to Enable Consistent CT Radiation Dose Optimization

OBJECTIVE

This article reviews the concepts of CT radiation dose optimization and process control, discusses how to achieve optimization and how to verify that it is consistently accomplished, and proposes strategies to move toward large-scale application.

CONCLUSION

CT dose optimization is achieved when the least amount of radiation necessary is used to achieve adequate image quality. The key to consistent optimization is minimization of unnecessary variation. This minimization is accomplished through local process control mechanisms.

Cumulative medical radiation exposure throughout staged palliation of single ventricle congenital heart disease

Patients with single ventricle heart disease undergoing staged palliation are exposed to ionizing radiation from multiple medical sources. We sought to quantify typical radiation burden in this population and identify risk factors for increased exposure. A retrospective review was performed of single ventricle patients surgically palliated at our institution, in which all studies utilizing ionizing radiation occurring from birth through Fontan completion were compiled. Thirty-eight patients were followed for a median of 33 months. A median of 59 radiation events occurred during follow-up, with a median cumulative effective dose of 25.7 milliSieverts (mSv). On average, cardiac catheterization accounted for 4% of radiation encounters but comprised 78% of total radiation exposure. In a multivariate model, factors associated with increased total radiation exposure included pulmonary artery (PA) stenosis requiring intervention (p = 0.005) and systemic right ventricle (p = 0.02). Risk factors for increased exposure from catheterization included heterotaxy syndrome (p = 0.007), re-coarctation (p = 0.003), and PA stenosis (p = 0.02). At our institution, many single ventricle patients are exposed to substantial radiation throughout staged palliation, most of which derives from cardiac catheterization. PA stenosis was identified as a risk factor for increased total and catheterization-based exposure. As patient survival improves, awareness of this scale of radiation exposure at a vulnerable period is imperative.

Diagnostic yield of computed tomography scan for pediatric hearing loss: a systematic review

BACKGROUND

Computed tomography (CT) has been used in the assessment of pediatric hearing loss, but concern regarding radiation risk and increased utilization of magnetic resonance imaging (MRI) have prompted us toward a more quantitative and sophisticated understanding of CT's potential diagnostic yield.

OBJECTIVE

To perform a systematic review to analyze the diagnostic yield of CT for pediatric hearing loss, including subgroup evaluation according to impairment severity and laterality, as well as the specific findings of enlarged vestibular aqueduct and narrow cochlear nerve canal.

DATA SOURCES

PubMed, EMBASE, and the Cochrane Library were assessed from the date of their inception to December 2013. In addition, manual searches of bibliographies were performed and topic experts were contacted.

REVIEW METHODS

Data from studies describing the use of CT in the diagnostic evaluation of pediatric patients with hearing loss of unknown etiology were evaluated, according to a priori inclusion/exclusion criteria. Two independent evaluators corroborated the extracted data. Heterogeneity was evaluated according to the I(2) statistic.

RESULTS

In 50 criteria-meeting studies, the overall diagnostic yield of CT ranged from 7% to 74%, with the strongest and aggregate data demonstrating a point estimate of 30%. This estimate corresponded to a number needed to image of 4 (range, 2-15). The most commonly identified findings were enlarged vestibular aqueduct and cochlear anomalies. The largest studies showed a 4% to 7% yield for narrow cochlear nerve canal.

CONCLUSION

These data, along with similar analyses of radiation risk and risks/benefits of sedated MRI, may be used to help guide the choice of diagnostic imaging.

Dose reduction efforts for pediatric head CT imaging in Washington State trauma centers: follow-up survey results

PURPOSE

To examine variation in pediatric trauma head CT imaging protocols in Washington State trauma centers (TCs) in 2012 and compare to a previous survey conducted in 2008-2009.

METHODS

A mixed-mode (online and paper) survey was sent to all adult and pediatric Washington State TCs (levels 1-5). Respondents provided information about the CT scanner used for pediatric head scans and technical information about pediatric dose reduction protocols. Mean head effective dose and organ dose for a female baby were estimated. Results were compared with previous data.

RESULTS

Sixty-one of 76 TCs responded to the 2012 survey (response rate, 80.3%, versus 76% for 2008-2009 survey). In 2012, 91.7% reported having a dedicated pediatric protocol (87.7% in 2008-2009). Protective shielding use ranged from 80% to 100% across both survey years. In 2012, 2.5 times more TCs provided sufficient information to conduct dose calculations than in 2008-2009. Estimated mean CT dose index was 23.1 milliGray (mGy) in 2012, compared with 34.8 mGy in 2008-2009 (P = .01). Estimated mean dose length product was also significantly lower in 2012 than 2008-2009 (307.6 mGy × cm versus 430.1 mGy × cm, respectively; P = .04). Wide variation in mean effective dose was observed for level 3 and 4 TCs in 2012, similar to variation observed in 2008-2009 among level 4 TCs. Mean organ dose was significantly lower in 2012 for eye lens and brain, but higher for thyroid than in 2008-2009 (P < .05).

CONCLUSIONS

Although most Washington State TCs employ dose reduction protocols for pediatric head CTs, and some measures were lower in 2012, variation in protocols use and estimated dose continues to exist. More complete responses in 2012 suggest improved understanding of the importance of pediatric dose reduction efforts. Education and institutional protocols are necessary to reduce pediatric radiation dose from head CTs.

National variation of technical factors in computed tomography of the head

OBJECTIVE

The objectives of this study were to describe head computed tomography (CT) technical factors used in the United States; assess guideline compliance and variability by sex, geographic region, institution, and manufacturer; and compare with NEXT (Nationwide Evaluation of X-ray Trends) survey.

METHODS

Two thousand thirty-five head CT studies from 895 sites were analyzed. Peak kilovoltage, exposure, slice and image number, slice thickness, field of view, interslice gap, reformations, examination inclusiveness, use of contrast, and reconstruction filter were compared by sex, geographic region, institution type, and manufacturer.

RESULTS

One hundred twenty to 140 kVp (peak kilovoltage) was used by 99.8% of the sites. There was no correlation between mAs and kVp. There was a 30-fold increase in number of images and nearly 9-fold increase in number of slices from least to most. Nearly 4% use slice thickness and interslice gap greater than guidelines. There were significant regional differences in field of view, image number, and slice thickness. Some variation related to manufacturers was found. Minor difference was also found between academic and nonacademic institutions. There were significant differences in kVp and mAs compared with NEXT.

CONCLUSIONS

Significant variations in head CT technique exist in the United States.

System for verifiable CT radiation dose optimization based on image quality. part II. process control system

PURPOSE

To evaluate the effect of an automated computed tomography (CT) radiation dose optimization and process control system on the consistency of estimated image noise and size-specific dose estimates (SSDEs) of radiation in CT examinations of the chest, abdomen, and pelvis.

MATERIALS AND METHODS

This quality improvement project was determined not to constitute human subject research. An automated system was developed to analyze each examination immediately after completion, and to report individual axial-image-level and study-level summary data for patient size, image noise, and SSDE. The system acquired data for 4 months beginning October 1, 2011. Protocol changes were made by using parameters recommended by the prediction application, and 3 months of additional data were acquired. Preimplementation and postimplementation mean image noise and SSDE were compared by using unpaired t tests and F tests. Common-cause variation was differentiated from special-cause variation by using a statistical process control individual chart.

RESULTS

A total of 817 CT examinations, 490 acquired before and 327 acquired after the initial protocol changes, were included in the study. Mean patient age and water-equivalent diameter were 12.0 years and 23.0 cm, respectively. The difference between actual and target noise increased from -1.4 to 0.3 HU (P < .01) and the standard deviation decreased from 3.9 to 1.6 HU (P < .01). Mean SSDE decreased from 11.9 to 7.5 mGy, a 37% reduction (P < .01). The process control chart identified several special causes of variation.

CONCLUSION

Implementation of an automated CT radiation dose optimization system led to verifiable simultaneous decrease in image noise variation and SSDE. The automated nature of the system provides the opportunity for consistent CT radiation dose optimization on a broad scale.

System for verifiable CT radiation dose optimization based on image quality. part I. Optimization model

PURPOSE

To develop and validate a mathematical radiation dose optimization model for computed tomography (CT) of the chest, abdomen, and pelvis.

MATERIALS AND METHODS

This quality improvement project was determined not to constitute human subject research. A model for measuring water-equivalent diameter (DW) based on the topogram was developed and validated on each axial section in eight CT examinations of the chest, abdomen, and pelvis (500 images). A model for estimating image noise and size-specific dose estimates (SSDEs) using image and metadata was developed and validated in 16 examinations of anthropomorphic phantoms. A model to quantify radiologist image quality preferences was developed and applied to evaluations of 32 CT examinations of the abdomen and pelvis by 10 radiologists. The scanners' dose modulation algorithms were modeled and incorporated into an application capable of prediction of image noise and SSDE over a range of patient sizes. With use of the application, protocol techniques were recommended to achieve specific image noise targets. Comparisons were evaluated by using two-tailed nonpaired and paired t tests.

RESULTS

The mean difference between topogram- and axial-based DW estimates was -3.5% ± 2.2 (standard deviation). The mean difference between estimated and measured image noise and volume CT dose index on the anthropomorphic phantoms was -6.9% ± 5.5 and 0.8% ± 1.8, respectively. A three-dimensional radiologist image quality preference model was developed. For the prediction model validation studies, mean differences between predicted and actual effective tube current-time product, SSDE, and estimated image noise were -0.9% ± 9.3, -1.8% ± 10.6, and -0.5% ± 4.4, respectively.

CONCLUSION

CT image quality and radiation dose can be mathematically predicted and optimized on the basis of patient size and radiologist-specific image noise target curves.

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.

The use of adaptive statistical iterative reconstruction in pediatric head CT: a feasibility study

BACKGROUND AND PURPOSE

Iterative reconstruction techniques facilitate CT dose reduction; though to our knowledge, no group has explored using iterative reconstruction with pediatric head CT. Our purpose was to perform a feasibility study to assess the use of ASIR in a small group of pediatric patients undergoing head CT.

MATERIALS AND METHODS

An Alderson-Rando head phantom was scanned at decreasing 10% mA intervals relative to our standard protocol, and each study was then reconstructed at 10% ASIR intervals. An intracranial region of interest was consistently placed to estimate noise. Our ventriculoperitoneal shunt CT protocol was subsequently modified, and patients were scanned at 20% ASIR with approximately 20% mA reductions. ASIR studies were anonymously compared with older non-ASIR studies from the same patients by 2 attending pediatric neuroradiologists for diagnostic utility, sharpness, noise, and artifacts.

RESULTS

The phantom study demonstrated similar noise at 100% mA/0% ASIR (3.9) and 80% mA/20% ASIR (3.7). Twelve pediatric patients were scanned at reduced dose at 20% ASIR. The average CTDI(vol) and DLP values of the 20% ASIR studies were 22.4 mGy and 338.4 mGy-cm, and for the non-ASIR studies, they were 28.8 mGy and 444.5 mGy-cm, representing statistically significant decreases in the CTDI(vol) (22.1%, P = .00007) and DLP (23.9%, P = .0005) values. There were no significant differences between the ASIR studies and non-ASIR studies with respect to diagnostic acceptability, sharpness, noise, or artifacts.

CONCLUSIONS

Our findings suggest that 20% ASIR can provide approximately 22% dose reduction in pediatric head CT without affecting image quality.