Kate A. Feinstein

Observer variability assessing US scans of the preterm brain: the ELGAN study

BackgroundNeurosonography can assist clinicians and can provide researchers with documentation of brain lesions. Unfortunately, we know little about the reliability of sonographically derived diagnoses.ObjectiveWe sought to evaluate observer variability among experienced neurosonologists.Materials and methodsWe collected all protocol US scans of 1,450 infants born before the 28th postmenstrual week. Each set of scans was read by two independent sonologists for the presence of intraventricular hemorrhage (IVH) and moderate/severe ventriculomegaly, as well as hyperechoic and hypoechoic lesions in the cerebral white matter. Scans read discordantly for any of these four characteristics were sent to a tie-breaking third sonologist.ResultsVentriculomegaly, hypoechoic lesions and IVH had similar rates of positive agreement (68–76%), negative agreement (92–97%), and kappa values (0.62 to 0.68). Hyperechoic lesions, however, had considerably lower values of positive agreement (48%), negative agreement (84%), and kappa (0.32). No sonologist identified all abnormalities more or less often than his/her peers. Approximately 40% of the time, the tie-breaking reader agreed with the reader who identified IVH, ventriculomegaly, or a hypoechoic lesion in the white matter. Only about 25% of the time did the third party agree with the reader who reported a white matter hyperechoic lesion.ConclusionObtaining concordance seems to be an acceptable way to assure reasonably high-quality of images needed for clinical research.

Reader Variability in the Use of Diagnostic Terms to Describe White Matter Lesions Seen on Cranial Scans of Severely Premature Infants: The ELGAN Study

To evaluate reader variability of white matter lesions seen on cranial sonographic scans of extreme low gestational age neonates (ELGANs).

Effect of comfort pads and incubator design on neonatal radiography

BackgroundThere has been increasing interest in patient dose reduction in neonatal intensive care units. Removing comfort pads for radiography has been identified as a potential means to decrease patient dose.ObjectiveTo assess the effect of comfort pads and support trays on detector entrance exposure (DEE) and image quality for neonatal radiography, and its implication for patient dose.Materials and methodsComfort pads and support trays from three incubator and warmer systems were examined. The attenuation of the primary beam by these structures was measured using a narrow beam geometry. Their effect on DEE and image quality was then assessed using typical neonatal chest radiography techniques with three configurations: 1) both the comfort pad and support included in the beam, 2) only the support tray included and 3) both the comfort pad and support tray removed.ResultsComfort pads and support trays were found to attenuate the primary beam by 6–15%. Eliminating these structures from the X-ray beam’s path was found to increase the detector entrance exposure by 28–36% and increase contrast-to-noise ratio by more than 21%, suggesting room for patient dose reduction when the same image quality is maintained.ConclusionComfort pads and tray support devices can have a considerable effect on DEE and image quality, with large variations among different incubator designs. Positioning the image detector directly underneath neonatal patients for radiography is a potential means for patient dose reduction. However, such benefit should be weighed against the risks of moving the patient.

SU-G-IeP3-09: Investigating the Interplay of Antiscatter Grids with Modern Detectors and Image Processing in Digital Radiography

PURPOSE To use phantom and simulation experiments to relate technique factors, patient size and antiscatter grid use to image quality in portable digital radiography (DR), in light of advancements in detector design and image processing. METHODS Image contrast-to-noise ratio (CNR) on a portable DR system (MobileDaRt Evolution, Shimadzu) was measured by imaging four aluminum inserts of varying thickness, superimposed on a Lucite slab phantom using a pediatric abdominal protocol. Three thicknesses of Lucite were used: 6.1cm, 12cm, and 18.2cm, with both 55 and 65 kVp beams. The mAs was set so that detector entrance exposure (DEE) was matched between kVp values. Each technique and phantom was used with and without an antiscatter grid (focused linear grid embedded in aluminum with an 8:1 ratio). The CNR-improvement-factor was then used to determine the thickness- and technique-dependent appropriateness of grid use. Finally, the same experiment was performed via Monte Carlo simulation, integrating incident energy fluence at each detector pixel, so that effects of detector design and image processing could be isolated from physical factors upstream of the detector. RESULTS The physical phantom experiment demonstrated a clear improvement for the lower tube voltage (55kVp), along with substantial CNR benefits with grid use for 12-18cm phantoms. Neither trend was evident with Monte Carlo, suggesting that suboptimal quantum-detection-efficiency and automated grid-removal could explain trends in kVp and grid use, respectively. CONCLUSION Physical experiments demonstrate marked improvement in CNR when using a grid for phantoms of 12 and 18cm Lucite thickness (above ∼10cm soft-tissue equivalent). This benefit is likely due to image processing, as this result was not seen with Monte Carlo. The impact of image processing on image resolution should also be investigated, and the CNR benefit of low kVp and grid use should be weighed against the increased exposure time necessary to achieve adequate DEE.

WE-E-18A-06: To Remove Or Not to Remove: Comfort Pads From Beneath Neonates for Radiography

PURPOSE To obtain an analytical empirical formula for the photon dose source term in forward direction from bremsstrahlung generated from laser-plasma accelerated electron beams in aluminum solid targets, with electron-plasma temperatures in the 10-100 keV energy range, and to calculate transmission factors for iron, aluminum, methacrylate, lead and concrete and air, materials most commonly found in vacuum chamber labs. METHODS Bremsstrahlung fluence is calculated from the convolution of thin-target bremsstrahlung spectrum for monoenergetic electrons and the relativistic Maxwell-Juettner energy distribution for the electron-plasma. Unattenuatted dose in tissue is calculated by integrating the photon spectrum with the mass-energy absorption coefficient. For the attenuated dose, energy dependent absorption coefficient, build-up factors and finite shielding correction factors were also taken into account. For the source term we use a modified formula from Hayashi et al., and we fitted the proportionality constant from experiments with the aid of the previously calculated transmission factors. RESULTS The forward dose has a quadratic dependence on electron-plasma temperature: 1 joule of effective laser energy transferred to the electrons at 1 m in vacuum yields 0,72 Sv per MeV squared of electron-plasma temperature. Air strongly filters the softer part of the photon spectrum and reduce the dose to one tenth in the first centimeter. Exponential higher energy tail of maxwellian spectrum contributes mainly to the transmitted dose. CONCLUSION A simple formula for forward photon dose from keV range temperature plasma is obtained, similar to those found in kilovoltage x-rays but with higher dose per dissipated electron energy, due to thin target and absence of filtration.

Progression-free survival of two cases of high-risk neuroblastoma with refractory/relapsed disease following surgery alone.

Outcome for the vast majority of high‐risk neuroblastoma patients with refractory or relapsed disease is dismal. We report two high‐risk patients who remain progression‐free for more than 113 and 18 months following the diagnosis of refractory/relapsed disease who were treated with surgery alone. Complete resolution of a refractory thoracic mass and relapsed liver nodules was observed in one patient. The refractory/relapsed disease in the second patient has remained stable. In both cases, the tumor showed histologic evidence of neuroblastoma maturation. These cases demonstrate that refractory/relapsed neuroblastoma is clinically heterogeneous and highlight the need for better biomarkers to optimize patient care. Pediatr Blood Cancer 2013; 60: 512–514.