Inter-model comparison of simulated Gulf of Mexico hypoxia in response to reduced nutrient loads: effects of phytoplankton and organic matter parameterization.

Complex simulation models are a valuable tool to inform nutrient management decisions aimed at reducing hypoxia in the northern Gulf of Mexico, yet simulated hypoxia response to reduced nutrients varies greatly between models. We compared two biogeochemical models driven by the same hydrodynamics, the Coastal Generalized Ecosystem Model (CGEM) and Gulf of Mexico Dissolved Oxygen Model (GoMDOM), to investigate how they differ in simulating hypoxia and their response to reduced nutrients. Different phytoplankton nutrient kinetics produced 2-3 times more hypoxic area and volume on the western shelf in CGEM compared to GoMDOM. Reductions in hypoxic area were greatest in the western shelf, comprising 72% (~4,200 km2) of the total shelfwide hypoxia response. The range of hypoxia responses from multiple models suggests a 60% load reduction may result in a 33% reduction in hypoxic area, leaving an annual hypoxic area of ~9,000 km2 based on the latest 5-yr average (13,928 km2).

Contiguous Low Oxygen Waters between the Continental Shelf Hypoxia Zone and Nearshore Coastal Waters of Louisiana, USA: Interpreting 30 Years of Profiling Data and Three-Dimensional Ecosystem Modeling.

The multidecadal expansion of northern Gulf of Mexico continental shelf hypoxia is a striking example of the adverse effects of anthropogenic nutrient enrichment on coastal oceans. Increased nutrient inputs and widespread shelf hypoxia have resulted in numerous dissolved oxygen (DO) water quality problems in nearshore coastal waters of Louisiana. A large hydrographic dataset compiled from research programs spanning 30 years and the three-dimensional hydrodynamic-biogeochemical model CGEM (Coastal Generalized Ecosystem Model) were integrated to explore the interconnections of low DO waters across the continental shelf to nearshore coastal waters of Louisiana. Cross-shelf vertical profiles showed contiguous low DO bottom waters extending from the shelf to coastal waters nearly every year in the 30+ year time series, which were concurrent with strong cross-shelf pycnoclines. A threshold Brunt-Väisälä frequency of 40 cycles h-1 was critical to maintaining the cross-shelf subpycnocline layers and facilitating the formation of a contiguous low DO water mass. Field observations and model simulations identified periods of wind-driven bottom water upwelling lasting between several days to several weeks, resulting in both physical advection of oxygen-depleted offshore waters to the nearshore and enhanced nearshore stratification. Both the upwelling of low DO bottom waters and in situ respiration were of sufficient temporal and spatial extent to drive DO below Louisiana's DO water quality criteria. Basin-wide nutrient management strategies aimed at reducing nutrient inputs and shelf hypoxia remain essential to improving the nearshore coastal water quality across the northern Gulf of Mexico.

Modeling Spatiotemporal Patterns of Ecosystem Metabolism and Organic Carbon Dynamics Affecting Hypoxia on the Louisiana Continental Shelf.

The hypoxic zone on the Louisiana Continental Shelf (LCS) forms each summer due to nutrient enhanced primary production and seasonal stratification associated with freshwater discharges from the Mississippi/Atchafalaya River Basin (MARB). Recent field studies have identified highly productive shallow nearshore waters as an important component of shelf-wide carbon production contributing to hypoxia formation. In this study we present results from a three-dimensional hydrodynamic-biogeochemical model named CGEM (Coastal Generalized Ecosystem Model) applied to quantify the spatial and temporal patterns of hypoxia, carbon production, respiration, and transport between nearshore and middle shelf regions where hypoxia is most prevalent. We first demonstrate that our simulations successfully reproduced spatial and temporal patterns of carbon production, respiration, and bottom-water oxygen gradients compared to field observations. We then used interannual simulations to identify transport of particulate organic carbon (POC) from nearshore areas where riverine organic matter and phytoplankton carbon production are greatest. The spatial disconnect between carbon production and respiration in our simulations was driven by westward and offshore POC flux, a pattern that supported heterotrophic respiration on the middle shelf where hypoxia is frequently observed. These results validate the importance of offshore carbon flux to hypoxia formation, particularly on the west shelf where hypoxic conditions are more variable.

The impact of alternative nutrient kinetics and computational grid size on model predicted primary production and hypoxic area in the northern Gulf of Mexico.

Model structure uncertainty is seldom calculated because of the difficulty and time required to perform such analyses. Here we explore how a coastal model using the Monod versus Droop formulations and a 6 km × 6 km versus 2 km 2 × km computational grid size predict primary production and hypoxic area in the Gulf of Mexico. Results from these models were compared to each other and to observations, and sensitivity analyses were performed. The different models fit the observations almost equally well. The 6k-model calculated higher rates of production and settling, and especially a larger hypoxic area, in comparison to the 2k-model. The Monod-based model calculated higher production, especially close to the river delta regions, but smaller summer hypoxic area, than the model using the Droop formulation. The Monod-based model was almost twice as sensitive to changes in nutrient loads in comparison to the Droop model, which can have management implications.

Parameter sensitivity and identifiability for a biogeochemical model of hypoxia in the northern Gulf of Mexico.

Local sensitivity analyses and identifiable parameter subsets were used to describe numerical constraints of a hypoxia model for bottom waters of the northern Gulf of Mexico. The sensitivity of state variables differed considerably with parameter changes, although most variables were responsive to changes in parameters that influenced planktonic growth rates and less sensitive to physical or chemical parameters. Variation in sensitivity had a direct correspondence with identifiability, such that only small subsets of the complete parameter set had unique effects on the model output. Selecting parameters by decreasing sensitivity demonstrated that only eight of 51 total parameters had a sufficiently unique effect on model output for accurate calibration. As a result, parameter selection heuristics were used to identify parameters for model calibration that depended on combined effects on output, relative sensitivity of each parameter, and ecological categories for the biogeochemical equations. The calibrated zero-dimensional (0-D) unit of the hypoxia model had improved fit to the observed data if sensitive phytoplankton parameters were included in an identifiable subset. Extension of results to a three-dimensional grid of the Gulf of Mexico showed that sensitive parameters for the 0-D model translated to non-trivial changes in the areal estimates of hypoxia.

The New Interventional Radiology Pathways: Options for Implementation.

The new interventional radiology (IR) pathways have generated much discussion with articles and editorials pointing out perceived advantages and disadvantages compared to the current pathways. To briefly review, under the new system, there are three pathways to enter IR: the integrated (INT) IR residency, the independent (IND) IR residency, and the early specialization in interventional radiology (ESIR) program. The pathways have been designed to provide maximum flexibility to programs for implementation and to radiology residents for planning their subspecialty training. As a result, there are many potential permutations for these training programs, and understanding the variety of options can be a challenge at first. We offer three potential solutions, based on the different circumstances or requirements a department might face. The first two solutions involve integrated programs created through newly funded and converted diagnostic radiology slots, respectively. The third involves establishing ESIR and IND programs only. Hopefully, the examples provided will be useful for those currently planning for the future of their IR training programs.

Neuroradiologic characteristics of astroblastoma and systematic review of the literature: 2 new cases and 125 cases reported in 59 publications.

BACKGROUND: Astroblastoma is a rare tumor of uncertain origin most commonly presenting in the cerebrum of children and young adults. The literature contains only case reports and small series regarding its radiologic features. This systematic review is the largest study of imaging findings of astroblastoma to date and serves to identify features that might differentiate it from other neoplasms. OBJECTIVE: This study describes the imaging features of astroblastoma based on a systematic review of the literature and two new cases. MATERIALS AND METHODS: We conducted a PubMed and Google Scholar database search that identified 59 publications containing 125 cases of pathology-confirmed astroblastoma, and we also added two new cases from our own institution. Data collected include patient age, gender, tumor location, morphology, calcifications and calvarial changes. We recorded findings on CT, MRI, diffusion-weighted imaging (DWI), MR spectroscopy, positron emission tomography (PET) and catheter angiography. RESULTS: Age at diagnosis ranged 0-70 years (mean 18 years; median 14 years). Female-to-male ratio was 8:1. Of 127 cases, 66 reported CT, 78 reported MRI and 47 reported both findings. Not all authors reported all features, but the tumor features reported included supratentorial in 96% (122/127), superficial in 72% (48/67), well-demarcated in 96% (79/82), mixed cystic-solid in 93% (79/85), and enhancing in 99% (78/79). On CT, 84% (26/31) of astroblastomas were hyperattenuated, 73% (27/37) had calcifications and 7 cases reported adjacent calvarial erosion. Astroblastomas were hypointense on T1-W in 58% (26/45) and on T2-W in 50% (23/46) of MRI sequences. Peritumoral edema was present in 80% (40/50) of cases but was typically described as slight. Six cases included DWI findings, with 100% showing restricted diffusion. On MR spectroscopy, 100% (5/5) showed nonspecific tumor spectra with elevated choline and decreased N-acetylaspartate (NAA). PET revealed nonspecific reduced uptake of [F-18] 2-fluoro-2-deoxyglucose ((18)F-FDG) and increased uptake of [11C]-Methionine in 100% (3/3) of cases. Catheter angiography findings (n=12) were variable, including hypervascularity in 67%, arteriovenous shunting in 33% and avascular areas in 25%. CONCLUSION: Astroblastomas occur most often in adolescent girls. Imaging often shows a supratentorial, superficial, well-defined, cystic-solid enhancing mass. On CT, most are hyperattenuated, have calcifications, and may remodel adjacent bone if superficial. MRI characteristically reveals a hypointense mass on T1-W and T2-W sequences with restricted diffusion. MR spectroscopy, PET and catheter angiography findings are nonspecific.

A witnessed case of a classic metaphyseal fracture caused during IV line placement in a child: Insight into mechanism of injury.

Recent publications argue that classic metaphyseal fractures are caused by rickets as opposed to trauma. Previous case reports of accidental traumatic classic metaphyseal fractures have been discounted due to lack of identification of the fracture at the time of the traumatic event, and lack of an evaluation for boney metabolic disorders. We report a case of a 20 day old male with a diagnosis of congenital vertical talus who sustained a classic metaphyseal fracture of the distal tibia during manipulation in preparation for intravenous line placement. The mechanics of the event causing the classic metaphyseal fracture were witnessed and accompanied by an audible "pop". Prior x-rays of the tibia demonstrate normal osseous morphology, and an evaluation for boney metabolic disorders was normal. This case identifies a traumatic classic metaphyseal fracture and provides insight into the types of forces necessary to cause such a fracture.

Implementation of a competency check-off in diagnostic fluoroscopy for radiology trainees: impact on reducing radiation for three common fluoroscopic exams in children.

BACKGROUND: Fluoroscopy is an important tool for diagnosis in the pediatric population, but it carries the risk of radiation exposure. Because radiology resident education and experience in the use of fluoroscopy equipment in children vary, we implemented an intervention to standardize fluoroscopy training. OBJECTIVE: The purpose of this study is to determine the impact of implementing a fluoroscopy competency check-off for radiology resident trainees aimed at decreasing radiation exposure in three common pediatric fluoroscopic studies. MATERIALS AND METHODS: A fluoroscopy competency check-off form was developed for radiology resident trainees performing pediatric procedures. Techniques used to limit radiation exposure for common pediatric radiologic studies were reviewed as part of the check-off process. Pediatric radiologists supervised each trainee until they demonstrated competence to independently perform three specified procedures. Radiation dose was recorded for the three procedures, upper GI (UGI), voiding cystourethrogram (VCUG) and oropharyngeal (OPM) exams, over 6 months preceding and 6 months following implementation of the competency check-off. The mean cumulative dose for each procedure was compared before and after implementation of competency check-off using a Kruskal-Wallis test. RESULTS: During the 12-month study period doses from 909 fluoroscopic procedures were recorded. In the 6 months preceding competency check-off implementation, procedures were performed by 24 radiology resident trainees including 171 UGI, 176 VCUG and 171 OPM exams. In the 6 months following competency check-off, 23 trainees performed 114 UGI, 145 VCUG and 132 OPM exams. After competency check-off implementation, a statistically significant reduction in average radiation dose was found for all three studies (P < 0.001). Median cumulative doses (mGy) were decreased by 33%, 36% and 13% for UGIs, VCUGs and OPMs, respectively. CONCLUSION: Implementation of a competency check-off for radiology resident trainees can reduce average radiation doses in pediatric patients undergoing three common fluoroscopic studies.

Biopsy-proven case of childhood primary angiitis of the central nervous system presenting with bilateral panuveitis and anisocoria.

Childhood primary angiitis of the central nervous system (cPACNS) is a rare and poorly understood immune-mediated vasculitis that preferentially affects blood vessels of the central nervous system (CNS). It must be distinguished from other disorders to initiate prompt treatment and improve the patient's prognosis. The presentation of cPACNS is highly variable, making a clinical diagnosis challenging. However, MRI may be helpful in showing typical findings including perivascular space inflammation and enhancement. Identification of these imaging features allows the radiologist to specifically suggest this rare diagnosis. The purpose of this manuscript is to present a biopsy-confirmed case of cPACNS in a 9-year-old girl who presented uniquely with panuveitis and anisocoria, and emphasize the MRI features that should prompt the radiologist to suggest this rare diagnosis.

Multiple cutaneous and hepatic hemangiomas in infants.

OBJECTIVES: The objectives of the study were to determine the rate of hepatic hemangiomas in infants with cutaneous infantile hemangiomas that were screened by abdominal ultrasound; identify morphological subtypes and number of cutaneous infantile hemangiomas that are likely to suggest the presence of hepatic hemangiomas; and identify clinical history, physical findings, or laboratory abnormalities that may predict hepatic involvement. METHODS: A retrospective study was conducted between 2000 and 2007 on 37 infants with cutaneous hemangiomas who underwent abdominal ultrasound for hepatic hemangiomas. Infants were classified into subgroups based upon the morphology of their cutaneous hemangioma(s). Data collected included clinical history, physical examination findings, sonographic findings, laboratory results, treatment(s) rendered, and clinical outcome. RESULTS: Eight of 37 infants (22%) had hepatic hemangiomas. Infants with miliary (30-100 pinpoint/small cutaneous hemangiomas), six or more small cutaneous hemangiomas, and one large with one or more small cutaneous hemangiomas were more likely to have concurrent hepatic hemangiomas. No other clinical findings were associated with hepatic involvement. CONCLUSIONS: Similar to other studies, our study found clinically asymptomatic hepatic hemangiomas in 22% of infants with multiple cutaneous infantile hemangiomas. No clinical findings studied were predictive of hepatic involvement.

Improvement in reporting skills of radiology residents with a structured reporting curriculum.

RATIONALE AND OBJECTIVES: Radiology residents must acquire dictation and reporting skills to meet Accreditation Council for Graduate Medical Examination requirements and provide optimal patient care. Historically, these skills have been taught informally and vary between institutions and among radiologists. A structured curriculum improves resident report quality when using a quantitative grading scheme. This study describes the implementation of such a curriculum and evaluates its utility in tracking resident progress. MATERIALS AND METHODS: We implemented a three-stage reporting curriculum in our diagnostic radiology residency program in 2009. Stages 1 and 2 involve instruction and formative feedback composed of suggestions for improvement in a 360° format from faculty, peers, and others within the resident's sphere of influence. The third stage involves individual, biannual, written feedback with scored reports specifically assessing four categories: succinctness, spelling/grammar, clarity, and responsible referral. Biannual scores were collected from 2009 to 2013, sorted by year of residency training (R1 to R4), and average training level scores were statistically compared. RESULTS: Review of 1500 reports over a 4-year period yielded a total of 153 scores: 54, 36, 29, and 34 from R1, R2, R3, and R4 residents, respectively. The mean (standard deviation) scores for R1, R2, R3, and R4 residents were 10.20 (1.06), 10.25 (0.81), 10.5 (0.74), and 10.75 (0.69), respectively. Post hoc analysis identified significant differences between R1 and R4 residents (P = .012) and R2 and R4 residents (P = .009). CONCLUSIONS: Residents' reporting scores showed significant improvement over the course of their residency training. This indicates that there may be a benefit in using an organized reporting curriculum to track resident progress in producing reports that may improve patient care.

Magnetic resonance imaging of the pediatric liver: benign and malignant masses.

Hepatic neoplasms constitute approximately 5% to 6% of all pediatric intra-abdominal masses, most of which are malignant. When compared with traditional multiphase computed tomography protocols that are often used in adults, magnetic resonance (MR) imaging is particularly desirable for evaluating liver lesions in children because of the lack of ionizing radiation and superb soft tissue contrast resolution. The goal of this article is to discuss common benign and malignant pediatric hepatic lesions and their key MR imaging findings. Particular emphasis is placed on the utility of new hepatocyte-specific contrast agents to narrow the differential diagnosis.

Current classification and terminology of pediatric vascular anomalies.

OBJECTIVE: The purpose of this article is to review new terminology to diagnose, classify, and refer patients with vascular anomalies for additional imaging, intervention, and treatment. CONCLUSION: In recent decades, much has been learned regarding the histopathology, cause, and treatment of vascular anomalies. As information has been gleaned, a new classification system has emerged that divides vascular anomalies into neoplasms and malformations. Its utility is based on accurate initial diagnosis that correlates consistently with clinical presentation, disease course, and treatment.

Vascular anomalies in pediatric patients: updated classification, imaging, and therapy.

Recent advances in knowledge regarding histopathology, cause, and treatment of pediatric vascular anomalies have led to substantial changes in classification and terminology. Over the past two decades, various subspecialists have adopted a new classification system proposed by the International Society for the Study of Vascular Anomalies (ISSVA). The ISSVA classification of vascular anomalies divides vascular anomalies into two categories: vascular neoplasms and malformations. It has been widely adopted by various pediatric subspecialists, because it reliably correlates patient presentation and disease progression, with more accurate histology, diagnosis, imaging, and treatment.

Findings and patterns on MRI and MR spectroscopy in neonates after therapeutic hypothermia for hypoxic ischemic encephalopathy treatment.

OBJECTIVES: The purpose of this study is to describe the findings and patterns of injury on magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) after whole-body hypothermia treatment for neonatal hypoxic ischemic encephalopathy. METHODS: A retrospective review of consecutive term neonates treated with whole-body hypothermia was performed. Data recorded included demographics and MRI and MRS findings, and day of life (DOL) studies were performed. Injury patterns were classified on MRI as deep, cortical, mixed, or diffuse. The relative apparent diffusion coefficient (rADC) was plotted against DOL scanned and the presence of lactate was recorded. RESULTS: MRI was performed in 44 infants, 34 of whom also underwent MRS. MRI was abnormal in 32% of neonates, 29.5% of whom were imaged at DOL 4 to 8. rADC values were lowest in neonates scanned on DOL 4 and 5 and remained low up to DOL 8. The deep brain nuclei were involved in hypoxic ischemic encephalopathy in 93% of neonates with abnormal MRIs and lactate was identified on MRS in 18% of neonates between DOL 4 and 8. CONCLUSIONS: MRI performed after therapeutic cooling was abnormal in 29.5% of neonates scanned on DOL 4 to 8. Deep nuclear injury was identified in 93% of neonates. Lactate was present on MRS in 18% of neonates, and rADC values were most reduced on MRI between DOL 4 and 8.

Spectrum of radiological manifestations of paediatric cat-scratch disease.

Cat-scratch disease (CSD) is usually a self-limiting condition that may mimic more serious disorders due to its variable clinical and imaging presentations. Many cases are diagnosed throughout the United States annually, with the majority occurring in children and adolescents who have had contact with a cat, usually in the form of a scratch or bite. This manuscript will discuss the spectrum of radiologic manifestations of CSD emphasising key imaging findings of lymphadenopathy, hepatosplenic lesions, osteomyelitis, discitis, encephalitis, neuroretinitis and cranial neuritis.

Congenital midline nasofrontal masses.

Congenital midline nasal masses are uncommon anomalies including nasal dermoids/epidermoids, nasal glial heterotopias and encephaloceles. These lesions can occur at the nasal bridge, extend intranasally and have intracranial extension with communication to the subarachnoid space. Therefore, accurate diagnosis of these lesions is critically important for presurgical planning and prevention of potentially fatal complications. Neuroimaging is essential in the evaluation of congenital midline nasal masses to identify the specific type of lesion, evaluate for the presence of intracranial extension and allow for appropriate presurgical planning.

Impact of ABR changes on pediatric radiology residency training.

PURPOSE: The aim of this study was to assess the impact of new ABR changes on pediatric radiology residency training in terms of the number, timing, availability, and funding of pediatric radiology rotations. METHODS: Participants were selected by using the ACGME's list of accredited American radiology residency programs, and data were collected via a survey. Program directors or persons designated by the program directors filled out the surveys. RESULTS: Of 186 programs, 84 (45%) responded. Three months of pediatric radiology were required in 61.0% of programs, with most having their residents complete one pediatric rotation during postgraduate years 2, 3, and 4. In 46% of training programs, pediatric radiology rotations were completed at the home institution. Seven percent of the programs plan to decrease the number of required pediatric rotations, while 75% plan no changes. Additional rotations in areas of interest are planned for 82% of programs. Only 54% could provide additional rotations in all 10 subspecialties, and 57% indicated that it was "very unlikely" or "impossible" that residents could acquire ≥12 months in a single area. Pediatric radiology is among the top 3 most frequent subspecialty areas that cannot be accommodated, along with obstetric and gynecologic (women's) and cardiac imaging. Funding limitations for pediatric rotations were not considered a barrier at 51% of programs. CONCLUSIONS: Seven percent of residency programs plan to cut back the overall number of pediatric radiology core rotations and move them to earlier in training (20%). Although 82% of programs said that they plan to provide more time in areas of interest, 57% said that it is very unlikely or impossible that residents could accumulate ≥12 months in an area of interest. It is possible that funding may limit access to additional pediatric rotations in up to 44% of programs. Seventeen of the programs did not know how their institution funded pediatric radiology rotations.