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OBJECTIVE: To externally validate two prediction models for pediatric radiographic pneumonia. METHODS: We prospectively evaluated the performance of two prediction models (Pneumonia Risk Score [PRS] and CARPE DIEM models) from a prospective convenience sample of children 90 days - 18 years of age from a pediatric emergency department undergoing chest radiography for suspected pneumonia between January 1, 2022, to December 31st, 2023. We evaluated model performance using the original intercepts and coefficients and evaluated for performance changes when performing recalibration and re-estimation procedures. RESULTS: We included 202 patients (median age 3 years, IQR 1-6 years), of whom radiographic pneumonia was found in 92 (41.0%). The PRS model had an area under the receiver operator characteristic curve of 0.72 (95% confidence interval [CI] 0.64-0.79), which was higher than the CARPE DIEM (0.59; 95% CI 0.51-0.67) (P<0.01). Using optimal cutpoints, the PRS model showed higher sensitivity (65.2%, 95% CI 54.6-74.9) and specificity (72.7%, 95% CI 63.4-80.8) compared to the CARPE DIEM model (sensitivity 56.5 [95% CI 45.8-66.8]; specificity 60.9 [95% CI 50.2-69.2]). Recalibration and re-estimation of models improved performance, particularly for the CARPE DIEM model, with gains in sensitivity and specificity, and improved calibration. CONCLUSION: The PRS model demonstrated better performance than the CARPE DIEM model in predicting radiographic pneumonia. Among children with a high rate of pneumonia, these models did not reach a level of performance sufficient to be used independently of clinical judgement. These findings highlight the need for further validation and improvement of models to enhance their utility.

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PURPOSE: The usage of PET/computed tomography (CT) to monitor hepatocellular carcinoma patients following yttrium-90 (Y) radioembolization has increased. Respiratory motion causes liver movement, which can be corrected using gating techniques at the expense of added noise. This work examines the use of amplitude-based gating on Y-PET/CT and its potential impact on diagnostic integrity. PATIENTS AND METHODS: Patients were imaged using PET/CT following Y radioembolization. A respiratory band was used to collect respiratory cycle data. Patient data were processed as both standard and motion-corrected images. Regions of interest were drawn and compared using three methods. Activity concentrations were calculated and converted into dose estimates using previously determined and published scaling factors. Diagnostic assessments were performed using a binary scale created from published Y-PET/CT image interpretation guidelines. RESULTS: Estimates of radiation dose were increased (P<0.05) when using amplitude-gating methods with Y PET/CT imaging. Motion-corrected images show increased noise, but the diagnostic determination of success, using the Kao criteria, did not change between static and motion-corrected data. CONCLUSION: Amplitude-gated PET/CT following Y radioembolization is feasible and may improve Y dose estimates while maintaining diagnostic assessment integrity.

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The usage of PET/CT to monitor patients with hepatocellular carcinoma following Y radioembolization has increased; however, image quality is often poor because of low count efficiency and respiratory motion. Motion can be corrected using gating techniques but at the expense of additional image noise. Amplitude-based gating has been shown to improve quantification in FDG PET, but few have used this technique in Y liver imaging. The patients shown in this work indicate that amplitude-based gating can be used in Y PET/CT liver imaging to provide motion-corrected images with higher estimates of activity concentration that may improve posttherapy dosimetry.

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New developments in PET/CT technology have enabled the commercial availability of continuous bed motion (CBM) acquisition methods. This technology has some potential performance benefits compared to standard step and shoot (SS) imaging, however, this technology has not been assessed with regard to quantitative and image quality parameters compared to traditional SS techniques. This study seeks to compare clinically relevant quantitative and image quality parameters using CBM and SS data collection methods with the intent of providing assistance in making educated decisions regarding imaging protocol development when using CBM technology versus SS imaging.

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Patellofemoral instability is related to anatomy. Magnetic resonance imaging (MRI) provides anatomic detail, but spoiled gradient echo (SPGR) imaging during isometric quadriceps contraction provides objective functional data for diagnosing patellofemoral laxity. Knee MRI studies and medical charts of 398 patients were retrospectively reviewed. Two independent blinded observers evaluated the knee MRI studies for patellofemoral morphology and patellar position on axial SPGR images during relaxation and isometric quadriceps contraction for lateral patellar migration. Charts were reviewed for history of patellofemoral instability or dislocation. Patients were divided into 2 groups: group 1 comprised patients with 2.5 mm or more of lateral patellar migration on axial SPGR images, and group 2 comprised patients with less than 2.5 mm of patellar subluxation. Logistic regression models were used to determine relationships between patellofemoral subluxation of 2.5 mm or more and (1) history of dislocation or clinical patellofemoral instability, (2) grade 4 chondromalacia on MRI, (3) corrected central trochlear height, and (4) differential trochlear height (corrected for lateral condylar height). Statistically significant associations were found between patellar subluxation and each of the above 4 clinical/morphologic measures. Lateral patellar migration of 2.5 mm or more on SPGR obtained during quadriceps contraction had statistically significant associations with the above 4 measures. Evaluation of SPGR of quadriceps contraction provides objective functional information about patellofemoral instability for management decisions.

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