More math, less "math war".

A false "equity versus excellence" debate over mathematics curricula has long disrupted education in the United States.

Patient Radiation Doses in IR Procedures: The American College of Radiology Dose Index Registry-Fluoroscopy Pilot.

PURPOSE: To update normative data on fluoroscopy dose indices in the United States for the first time since the Radiation Doses in Interventional Radiology study in the late 1990s. MATERIALS AND METHODS: The Dose Index Registry-Fluoroscopy pilot study collected data from March 2018 through December 2019, with 50 fluoroscopes from 10 sites submitting data. Primary radiation dose indices including fluoroscopy time (FT), cumulative air kerma (Ka,r), and kerma area product (PKA) were collected for interventional radiology fluoroscopically guided interventional (FGI) procedures. Clinical facility procedure names were mapped to the American College of Radiology (ACR) common procedure lexicon. Distribution parameters including the 10th, 25th, 50th, 75th, 95th, and 99th percentiles were computed. RESULTS: Dose indices were collected for 70,377 FGI procedures, with 50,501 ultimately eligible for analysis. Distribution parameters are reported for 100 ACR Common IDs. FT in minutes, Ka,r in mGy, and PKA in Gy-cm2 are reported in this study as (n; median) for select ACR Common IDs: inferior vena cava filter insertion (1,726; FT: 2.9; Ka,r: 55.8; PKA: 14.19); inferior vena cava filter removal (464; FT: 5.7; Ka,r: 178.6; PKA: 34.73); nephrostomy placement (2,037; FT: 4.1; Ka,r: 39.2; PKA: 6.61); percutaneous biliary drainage (952; FT: 12.4; Ka,r: 160.5; PKA: 21.32); gastrostomy placement (1,643; FT: 3.2; Ka,r: 29.1; PKA: 7.29); and transjugular intrahepatic portosystemic shunt placement (327; FT: 34.8; Ka,r: 813.0; PKA: 181.47). CONCLUSIONS: The ACR DIR-Fluoro pilot has provided state-of-the-practice statistics for radiation dose indices from IR FGI procedures. These data can be used to prioritize procedures for radiation optimization, as demonstrated in this work.

Patient Radiation Doses in Interventional Radiology Procedures: Comparison of Fluoroscopy Dose Indices between the American College of Radiology Dose Index Registry-Fluoroscopy Pilot and the Radiation Doses in Interventional Radiology Study.

PURPOSE: To compare radiation dose index distributions for fluoroscopically guided interventions in interventional radiology from the American College of Radiology (ACR) Fluoroscopy Dose Index Registry (DIR-Fluoro) pilot to those from the Radiation Doses in Interventional Radiology (RAD-IR) study. MATERIALS AND METHODS: Individual and grouped ACR Common identification numbers (procedure types) from the DIR-Fluoro pilot were matched to procedure types in the RAD-IR study. Fifteen comparisons were made. Distribution parameters, including the 10th, 25th, 50th, 75th, and 95th percentiles, were compared for fluoroscopy time (FT), cumulative air kerma (Ka,r), and kerma area product (PKA). Two derived indices were computed using median dose indices. The procedure-averaged reference air kerma rate (Ka,r¯) was computed as Ka,r / FT. The procedure-averaged x-ray field size at the reference point (Ar) was computed as PKA / (Ka,r × 1,000). RESULTS: The median FT was equally likely to be higher or lower in the DIR-Fluoro pilot as it was in the RAD-IR study, whereas the maximum FT was almost twice as likely to be higher in the DIR-Fluoro pilot than it was in the RAD-IR study. The median Ka,r was lower in the DIR-Fluoro pilot for all procedures, as was median PKA. The maximum Ka,r and PKA were more often higher in the DIR-Fluoro pilot than in the RAD-IR study. Ka,r¯ followed the same pattern as Ka,r, whereas Ar was often greater in DIR-Fluoro. CONCLUSIONS: The median dose indices have decreased since the RAD-IR study. The typical Ka,r rates are lower, a result of the use of lower default dose rates. However, opportunities for quality improvement exist, including renewed focus on tight collimation of the imaging field of view.

Structure-Guided Insight into the Specificity and Mechanism of a Parasitic Nucleoside Hydrolase.

Trichomonas vaginalis is the causative parasitic protozoan of the disease trichomoniasis, the most prevalent, nonviral sexually transmitted disease in the world. T. vaginalis is a parasite that scavenges nucleosides from the host organism via catalysis by nucleoside hydrolase (NH) enzymes to yield purine and pyrimidine bases. One of the four NH enzymes identified within the genome of T. vaginalis displays unique specificity toward purine nucleosides, adenosine and guanosine, but not inosine, and atypically shares greater sequence similarity to the pyrimidine hydrolases. Bioinformatic analysis of this enzyme, adenosine/guanosine-preferring nucleoside ribohydrolase (AGNH), was incapable of identifying the residues responsible for this uncommon specificity, highlighting the need for structural information. Here, we report the X-ray crystal structures of holo, unliganded AGNH and three additional structures of the enzyme bound to fragment and small-molecule inhibitors. Taken together, these structures facilitated the identification of residue Asp231, which engages in substrate interactions in the absence of those residues that typically support the canonical purine-specific tryptophan-stacking specificity motif. An altered substrate-binding pose is mirrored by repositioning within the protein scaffold of the His80 general acid/base catalyst. The newly defined structure-determined sequence markers allowed the assignment of additional NH orthologs, which are proposed to exhibit the same specificity for adenosine and guanosine alone and further delineate specificity classes for these enzymes.

CT, US and MRI of xanthine urinary stones: in-vitro and in-vivo analyses.

BACKGROUND: Xanthine urinary stones are a rare entity that may occur in patients with Lesch-Nyhan syndrome receiving allopurinol. There is little literature describing imaging characteristics of these stones, and the most appropriate approach to imaging these stones is therefore unclear. We performed in-vitro and in-vivo analyses of xanthine stones using computed tomography (CT) at different energy levels, ultrasound (US), and magnetic resonance imaging (MRI). METHODS: Five pure xanthine stones from a child with Lesch-Nyhan were imaged in-vitro and in-vivo. CT of the stones was performed at 80 kVp, 100 kVp, 120 kVp and 140 kVp and CT numbers of the stones were recorded in Hounsfield units (HU). US of the stones was performed and echogenicity, acoustic shadowing and twinkle artifact were assessed. MRI of the stones was performed and included T2-weighted, ultrashort echo-time-weighted and T2/T1-weighted 3D bFFE sequences and signal was assessed. RESULTS: In-vitro analysis on CT demonstrated that xanthine stones were radiodense and the average attenuation coefficient did not differ with varying kVp, measuring 331.0 ± 51.7 HU at 80 kVp, 321.4 ± 63.4 HU at 100 kVp, 329.7 ± 54.2 HU at 120 kVp and 328.4 ± 61.1 HU at 140 kVp. In-vivo analysis on CT resulted in an average attenuation of 354 ± 35 HU. On US, xanthine stones where echogenic with acoustic shadowing and twinkle artifact. On MRI, stones lacked signal on all tested sequences. CONCLUSION: Xanthine stone analyses, both in-vitro and in-vivo, demonstrate imaging characteristics typical of most urinary stones: dense on CT, echogenic on US, and lacking signal on MRI. Therefore, the approach to imaging xanthine stones should be comparable to that of other urinary stones.

Computational Thinking Is More about Thinking than Computing.

Computational thinking is widely recognized as important, not only to those interested in computer science and mathematics but also to every student in the twenty-first century. However, the concept of computational thinking is arguably complex; the term itself can easily lead to direct connection with "computing" or "computer" in a restricted sense. In this editorial, we build on existing research about computational thinking to discuss it as a multi-faceted theoretical nature. We further present computational thinking, as a model of thinking, that is important not only in computer science and mathematics, but also in other disciplines of STEM and integrated STEM education broadly.

The American College of Radiology Fluoroscopy Dose Index Registry Pilot: Technical Considerations and Dosimetric Performance of the Interventional Fluoroscopes.

PURPOSE: To characterize the accuracy and consistency of fluoroscope dose index reporting and report rates of occupational radiation safety hardware availability and use, trainee participation in procedures, and optional hardware availability at pilot sites for the American College of Radiology (ACR) Fluoroscopy Dose Index Registry (DIR). MATERIALS AND METHODS: Nine institutions participated in the registry pilot, providing fluoroscopic technical and clinical practice data from 38 angiographic C-arm-type fluoroscopes. These data included measurements of the procedure table and mattress transmission factors and accuracy measurements of the reference-point air kerma (Ka,r) and air kerma-area product (PKA). The accuracy of the radiation dose indices were analyzed for variation over time by 1-way analysis of variance (ANOVA). Sites also self-reported information on availability and use of radiation safety hardware, hardware configuration of fluoroscopes, and trainee participation in procedures. RESULTS: All Ka,r and PKA measurements were within the ±35% regulatory limit on accuracy. The mean absolute difference between correction factors for a given system in fluoroscopic and acquisition mode was 0.03 (95% confidence interval, 0.03-0.03). For the 28 fluoroscopic imaging planes that provided data for 3 time points, ANOVA yielded an F value of 0.134 with an F-critical value of 3.109 (P = .875). CONCLUSIONS: This publication provides the technical and clinical framework pertaining to the ACR Fluoroscopy DIR pilot and offers necessary context for future analysis of the clinical procedure radiation-dose data collected.

Percutaneous Coronary Intervention in Pregnancy: Modeling of the Fetal Absorbed Dose.

There is a gap in the literature regarding fetal radiation exposure from interventional cardiac procedures. With an increasingly large and complex cohort of pregnant cardiac patients, it is necessary to evaluate the safety of invasive cardiac procedures and interventions in this population. Here we present a case of a patient with multiple medical comorbidities and non-ST elevation myocardial infarction (NSTEMI) at 15 weeks' gestation, managed with percutaneous coronary intervention (PCI). We were able to minimize the maternal and estimated fetal absorbed radiation dose to <1 milliGray (mGy), significantly less than the threshold dose for fetal adverse effects at this gestational age.

Radiation dose monitoring in pediatric fluoroscopy: comparison of fluoroscopy time and dose-area product thresholds for identifying high-exposure cases.

BACKGROUND: Fluoroscopy time has been used as a surrogate for radiation dose monitoring in pediatric fluoroscopy; however it does not account for factors such as magnification or collimation. Dose-area product (DAP) is a more accurate measure of radiation exposure but its dependence on patient weight and body-part thickness is a challenge in children of varying ages. OBJECTIVE: To determine whether fluoroscopy time and DAP produce concurrent results when they are used to identify high-exposure cases, and to establish radiation dose thresholds for our institution. MATERIALS AND METHODS: During a 2-year period we prospectively monitored pediatric fluoroscopy studies performed at the Children's Hospital at Montefiore. We recorded study type, fluoroscopy time, DAP, patient age, weight and height. We then calculated 90th percentile fluoroscopy time and DAP thresholds for weight and age. RESULTS: We evaluated 1,011 cases (453 upper gastrointestinal [UGI] series, 266 voiding cystourethrograms [VCUGs], 120 contrast enemas, 108 speech studies, and 64 esophagrams). Fluoroscopy time demonstrated moderate correlation with DAP (rs=0.45, P<0.001, Spearman rank). DAP strongly correlated with patient weight (rs=0.71, P<0.001) and age (rs=0.70, P<0.001). Concordance of cases exceeding 90th percentile thresholds for fluoroscopy time and DAP were κ=0.27 for UGI series and κ=0.49 for VCUG for weight-based cutoffs, and κ=0.36 for UGI series and κ=0.40 for VCUG for age-based cutoffs. CONCLUSION: The limited correlation of fluoroscopy time with DAP suggests these methods are not equivalent for dose monitoring. However, the strong correlation of DAP with patient weight and age presents a challenge for establishing DAP thresholds in children, who range widely in size. Despite controlling for weight or age, there was limited overlap of cases exceeding the 90th percentile threshold for fluoroscopy time and DAP. This further reinforces the non-overlapping outcome of these two methods and indicates that fluoroscopy time might be inadequate for dose monitoring.

Arginine refolds, stabilizes, and restores function of mutant pVHL proteins in animal model of the VHL cancer syndrome.

The von Hippel-Lindau (VHL) syndrome is a rare inherited cancer, caused by mutations in the VHL gene, many of which render the VHL protein (pVHL) unstable. pVHL is a tumor-suppressor protein implicated in a variety of cellular processes, most notably in response to changes in oxygen availability, due to its role as part of an E3-ligase complex which targets the hypoxia-inducible factor (HIF) for degradation. Previously we reported, using in silico and in vitro analyses, that common oncogenic VHL mutations render pVHL less stable than the wild-type protein, distort its core domain and as a result reduce the ability of the protein to bind its target HIF-1α. Among various chemical chaperones tested, arginine was the most effective in refolding mutant of pVHL. Here we examined the consequences of administering L- or D-arginine to a Drosophila VHL model and to human renal carcinoma cells, both expressing misfolded versions of human pVHL. Arginine treatment increased pVHL solubility in both models and increased the half-life of the mutant pVHL proteins in the cell culture. In both models, L- as well as D-arginine enhanced the ability of wild-type pVHL and certain misfolded mutant versions of pVHL to bind ODD, the HIF-derived target peptide, reflecting restoration of pVHL function. Moreover, continuous feeding of Drosophila expressing misfolded versions of pVHL either L- or D-arginine rich diet rescued their lethal phenotype. Collectively, these in vivo results suggest that arginine supplementation should be examined as a potential novel treatment for VHL cancer syndrome.

Evaluating an Image Gently and Image Wisely Campaign in a Multihospital Health Care System.

PURPOSE: The efficacy of an Image Gently(®)/Image Wisely(®) radiology departmental campaign consisting of the optimization of CT protocols to reduce dose while maintaining quality, and an educational effort to alter the ordering patterns of referring physicians at a multihospital academic center, was evaluated. METHODS: The numbers of CT, MR, and ultrasound studies performed at inpatient, outpatient, and emergency facilities in the hospital system before and after the initiation of the departmental campaign (2010) were obtained for a 10-year period (2004-2014) using a radiology information system. For the same time period, dose per scan (volumetric CT dose index) was obtained through the Dose Index Registry(®)/National Radiology Data Registry for frequently performed studies. Descriptive statistics were used to analyze temporal trends in radiation dose and utilization across differing age groups: <20, 20 to 39, and 40 to 59 years. RESULTS: The radiology information system yielded 865,879 imaging examinations and 4,508,030 patients. Although patient and imaging volume grew annually over the study period (by 6.8% and 4.9%, respectively), CT utilization as a percentage of total imaging decreased, compensated for by an increase in ultrasound use. This was most marked in the youngest age group. MR use as a percentage of total imaging was unchanged. The median volumetric CT dose index for each study protocol was reduced or stabilized. CONCLUSIONS: The campaign resulted in a reduction in CT utilization, a reduction in radiation dose per study, and a compensatory rise in ultrasound use. An interactive aggressive educational campaign directed toward referring providers combined with protocol dose reduction efforts can be successful in reducing patient exposure from medical radiation.

CT versus ultrasound guidance for percutaneous drainages in the pediatric population: an institutional review meant to limit radiation.

Computed tomography (CT)-guided percutaneous drainage is a minimally invasive procedure that allows for accurate diagnosis and therapy with minimal complications. The drawback is that CT guidance carries a significant amount of radiation exposure. CT-guided percutaneous drainages have been widely used in adults and have been gaining momentum within the pediatric population. Through a thorough review of our institution's (Montefiore Medical Center) CT-guided percutaneous drainages within our pediatric patients, we assessed the radiation exposure per study as well as which studies were deemed possible under ultrasound guidance as a possible alternative.

Differential effects of HIF-α isoforms on apoptosis in renal carcinoma cell lines.

BACKGROUND: Germline mutations in the von Hippel-Lindau (VHL) tumor suppressor gene predispose individuals to clear cell renal carcinomas, hemangioblastomas, and pheochromocytomas. The VHL gene product forms an ubiquitin E3 ligase complex, with regulation of hypoxia-inducible factor alpha (HIF-α) as its best known function. Lack of VHL expression has been shown previously to sensitize renal cells to apoptosis caused by certain cellular stresses. In this report, the role of HIF-α in apoptosis was investigated using two parent VHL-null renal carcinoma cell lines. METHODS: 786-O and RCC10 renal carcinoma cell lines with manipulated levels of VHL, HIF-1α, or HIF-2α were subjected to cellular stresses and analyzed by western blotting for the abundance of apoptotic markers. RESULTS: Cell lines expressing mutant VHL proteins that were unable to regulate HIF-α had increased levels of apoptosis when irradiated with ultraviolet (UV) light. The influences of the two major isoforms of HIF-α, HIF-1α and HIF-2α, on apoptosis, were compared by creating cell lines in which levels of each isoform were modulated via short hairpin RNA interference. In UV-irradiated cells, HIF-2α expression was determined to promote apoptosis, whereas HIF-1α was anti-apoptotic. In cells deprived of either glucose or serum, HIF-1α expression was generally anti-apoptotic, while HIF-2α expression was observed to either promote apoptosis or have less of an influence on apoptosis, depending on the cell line used. CONCLUSIONS: HIF-1α and HIF-2α exerted distinct effects in each of the conditions tested, with expression of HIF-1α largely blocking apoptosis and HIF-2α generally promoting apoptosis. These results reinforce that HIF-1α and HIF-2α have distinct biological roles and that their relative expression levels may influence some therapeutic interventions that are dependent on apoptosis.

Expression of PKC iota affects neuronal differentiation of PC12 cells at least partly independent of kinase function.

Atypical PKC (aPKC) plays a role in establishing cell polarity and has been indicated in neuronal differentiation and polarization, including neurite formation in rat pheochromocytoma PC12 cells, albeit by unclear mechanisms. Here, the role of the aPKC isoform, PKC iota (PKCι), in the early neuronal differentiation of PC12 cells was investigated. NGF-treated PC12 cells with stably expressed exogenous wild-type PKCι showed decreased expression of a neuroendocrine marker, increased expression of a neuronal marker, and increased neurite formation. Stable expression of a kinase- inactive PKCι, but not constitutively active PKCι lacking a regulatory domain, had similar although less potent effects. Pharmacological inhibition of endogenous aPKC kinase activity in parental PC12 cells did not inhibit neurite formation, suggesting that some of the observed effects of PKCι expression on neuronal differentiation are kinase- independent. Interestingly, exogenous expression of wild-type and kinase-inactive PKCι had little effect on overall PKCι activity, but caused a decrease in PKC zeta (PKCζ) kinase activity, suggesting an interplay between the two isoforms that may underlie the observed results. Overall, these findings suggest that in PC12 and perhaps other neuroendocrine precursor cells, PKCι influences an early differentiation decision between the neuroendocrine (chromaffin) and sympathetic neuron cell lineages, potentially by affecting PKCζ function.

Expression of VHL Causes Three-Dimensional Morphological Changes in Renal Cells Indicative of Proximal Tubule Differentiation.

Mutations in the von Hippel-Lindau (VHL) tumor suppressor gene are responsible for the VHL hereditary cancer syndrome, and are associated with the majority of clear cell renal cell carcinomas. In this study, scanning electron microscopy of VHL-negative renal carcinoma cells was utilized to examine the effects of VHL re-expression on the morphology of these cells. Significant differences were observed between the morphology of VHL-negative control cells and those with reintroduced VHL, with VHL expression mediating an apical surface that mounded upward, as opposed to the flat surfaces seen with VHL-negative cells. In long term cultures, rounded VHL-expressing cells grew in clusters on top the monolayer, and microvilli were observed on the apical face of these cells, in a manner suggestive of proximal tubule differentiation. In contrast, VHL-negative cells remained flat and did not develop microvilli in long-term cultures. Since VHL is a key member of an ubiquitin E3 ligase complex whose best known target is hypoxia-inducible factor alpha (HIF-α), we looked at the effects of HIF-α expression on cell morphology. Knockdown of HIF-2α in cells that only express this isoform had no effect on the morphology of the cells. These results indicate that VHL expression directs three dimensional morphological changes in renal cells indicative of differentiation, and while dysregulation of HIF-α may be necessary for tumorigenesis following VHL loss, it is not the major determinant of these VHL-mediated morphological changes.

Feasibility of using single-slice MDCT to evaluate visceral abdominal fat in an urban pediatric population.

OBJECTIVE: Obesity is a growing clinical problem, especially among children of low socioeconomic status. Increased visceral abdominal fat is implicated in the metabolic syndrome and its health consequences. The purpose of this study is to validate measurement of a single MDCT slice as a predictor of total visceral abdominal fat and to correlate over a wide range of body mass indexes (BMIs). MATERIALS AND METHODS: A two-phase retrospective analysis was performed. For validation, MDCTs of 21 consecutive healthy children (8-14 years old) were reviewed. In these cases, visceral abdominal fat and subcutaneous abdominal fat area were calculated using a body fat analysis function from single 0.625-mm MDCT slices at the umbilicus and were compared with total visceral abdominal fat area as measured from T11 to the coccyx. Subsequently, visceral abdominal fat area was obtained from single slices at the umbilicus from abdominal MDCT scans of 146 consecutive healthy children (age range, 6-14 years; 80 boys and 66 girls; 77 Hispanic, 41 African American, 15 white, and 13 multiracial or other race) for whom BMI was available. Associations between visceral abdominal fat area and sex, race, and BMI were determined. Effective radiation dose for a 1.25-mm axial MDCT slice was calculated using a mathematic model that uses derived scaling factors for pediatric patients. RESULTS: Visceral abdominal fat area obtained from a 0.625-mm slice at the umbilicus was highly correlated with total visceral abdominal fat area (r = 0.96; p < 0.0001). Visceral abdominal fat area from single slices at the umbilicus was significantly correlated with BMI (r = 0.72; p < 0.0001). Umbilical visceral abdominal fat area was significantly lower in African American children compared with others (median, 14 vs 22 cm(2); p = 0.02) and was not associated with sex. In our population, the effective radiation dose from the smallest obtainable slice was 0.015-0.019 mSv/37-54 kg of patient weight. CONCLUSION: Visceral abdominal fat area calculated from a single abdominal MDCT slice obtained in children is highly correlated with total visceral abdominal fat and with BMI and involves limited radiation exposure.

Radiation exposure from medical imaging in patients with chronic and recurrent conditions.

PURPOSE: Advances in medical imaging have been associated with increased utilization and increased radiation exposure, especially for patients with chronic and recurrent conditions. The authors estimated the cumulative radiation doses from medical imaging for specific cohorts with chronic and recurrent conditions. METHODS: All patients diagnosed with hydrocephalus (n = 1,711), pulmonary thromboembolic disease (n = 3,220), renal colic (n = 5,855), and cardiac disease (n = 11,072) from January 1, 2000, to December 31, 2005, were retrospectively identified. Each imaging examination that used ionizing radiation from 2000 to 2008 was incorporated into an estimate of total effective dose and organ-specific doses. Patients with high levels of radiation exposure after 3 years (total effective dose > 50 mSv; dose to the ocular lens > 150 mSv) were identified. RESULTS: The mean estimated effective doses for the surviving diagnostic cohorts after 3 years were 12.3 mSv for patients with hydrocephalus, 21.7 mSv for those with pulmonary thromboembolic disease, 18.7 mSv for those with renal colic, and 14.0 mSv for those with cardiac disease. Among patients with hydrocephalus, 26.3% (339 of 1,291) had radiation doses > 150 mSv to the ocular lens within 3 years. In all cohorts, the proportion of patients with total effective doses > 50 mSv within 3 years was significantly higher for those diagnosed in 2004 and 2005 than for those diagnosed in 2000 and 2001. CONCLUSION: Patients with hydrocephalus, pulmonary thromboembolic disease, renal colic, and cardiac disease received radiation exposures that may put them at increased risk for cancer. Moreover, the proportion who received estimated total effective doses > 50 mSv within 3 years was significantly higher for those diagnosed most recently. It is the responsibility of institutions and physicians to critically evaluate their infrastructures, diagnostic strategies, and imaging techniques for each individual patient, with an eye toward minimizing cumulative medical radiation exposure.

Scatter radiation from chest radiographs: is there a risk to infants in a typical NICU?

OBJECTIVE: To evaluate the dose of scatter radiation to infants in a NICU in order to determine the minimal safe distance between isolettes. MATERIALS AND METHODS: Dose secondary to scattered radiation from an acrylic phantom exposed to vertical and horizontal beam exposures at 56 kVp was measured at 93 cm and 125 cm from the center of the phantom. This corresponds to 2 and 3 ft between standard isolettes, respectively. For horizontal exposures, the dosimeter was placed directly behind a CR plate and scatter dose at 90-degrees and 135-degrees from the incident beam was also measured. Exposures were obtained at 160 mAs and the results were extrapolated to correspond to 2.5 mAs. Four measurements were taken at each point and averaged. RESULTS: At 125 cm and 93 cm there was minimal scatter compared to daily natural background radiation dose (8.493 microGy). Greatest scatter dose obtained from a horizontal beam exposure at 135 degrees from the incident beam was still far below background radiation. CONCLUSION: Scatter radiation dose from a single exposure as well as cumulative scatter dose from numerous exposures is significantly below natural background radiation. Infants in neighboring isolettes are not at added risk from radiation scatter as long as the isolettes are separated by at least 2 ft.