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The purpose of this article is to assess radiation dose reduction, image quality, and diagnostic confidence using low tube voltage in combination with hybrid iterative reconstruction in contrast-enhanced pediatric abdominal CT.CT examinations of 133 patients (median age, 10 years) were performed at sequentially reduced doses. The first group (group 1) was scanned using dimension-based protocols at 120 kV for all patient sizes. The optimized group (group 5) was scanned at 80 kV for less than 18 cm in the lateral dimension and 100 kV in the 19-30 cm lateral dimension. CT examinations reconstructed with filtered back projection (FBP) and four levels of hybrid iterative reconstruction were reviewed by four blinded readers for subjective image quality and diagnostic confidence. Objective noise, volume CT dose index (CTDIvol), and size-specific dose estimate (SSDE) were recorded. Data were analyzed using t tests, one and two-way ANOVA, and the intraclass correlation coefficient.Compared with group 1, the radiation dose was reduced for group 5 by 63% measured by SSDE (4.69 vs 10.00 mGy; p0.001). Subjective image noise was increased for FBP images (p0.001) but not was statistically significantly different for all levels of hybrid iterative reconstruction; artifacts were reduced and visibility of small structures was improved (both p0.001). Diagnostic confidence was improved for solid organ injury and metastatic disease (both p0.001) and was not statistically significantly different for appendicitis (p = 0.306).Use of hybrid iterative reconstruction with low-tube-voltage protocols enables substantial radiation dose reduction for pediatric abdominal CT with equivalent to improved subjective image quality and diagnostic confidence.

A potential advantage of pulmonary CT angiography (CTA) is its ability to show alternative diagnoses in patients without evidence of pulmonary embolism (PE), but the frequency and spectrum of alternative diagnoses have yet to be determined in the pediatric population. Our purpose was to determine the frequency and types of alternative diagnoses identified in children with clinically suspected but excluded PE.We used our hospital information system to identify all consecutive pediatric patients (18 years old) with clinically suspected PE who underwent pulmonary CTA from July 2004 to March 2008. Two experienced pediatric radiologists reviewed by consensus a series of 96 consecutive diagnostic-quality pulmonary CTA studies without evidence of PE from 89 patients. Each study was systematically reviewed by consensus for a possible alternative diagnosis in the lungs, mediastinum, central airways, cardiovascular system, pleura, and skeleton.The study population consisted of 89 children (28 boys and 61 girls; mean age 13.4 +/- 4.7 years; range, 2 months-18 years; 34 inpatients, 62 outpatients) who underwent a total of 96 pulmonary CTA studies without evidence of PE. Thirty-nine (41%) of 96 pulmonary CTA studies were normal. Alternative diagnoses were identified for each of the remaining 57 (59%) studies, including: pneumonia (n = 22), atelectasis (n = 22), malignancy (n = 3), congenital heart disease (n = 2), pulmonary hypertension (n = 2), pericardial effusion (n = 2), pulmonary nodules (n = 1), rib fractures (n = 1), right atrial thrombus (n = 1), and fat embolism (n = 1). Seventeen patients showed pleural effusions that were associated with coexisting pneumonia (n = 8), atelectasis (n = 8), or rib fractures (n = 1).Among children with clinically suspected but excluded PE, pulmonary CTA frequently shows positive findings. Although pneumonia and atelectasis are most common, a variety of other alternative diagnoses may be detected throughout the thorax.