Donald A. Tracy

Comparison of Standard-Dose and Reduced-Dose Expiratory MDCT Techniques for Assessment of Tracheomalacia in Children

RATIONALE AND OBJECTIVES The aim of this study was to assess the effects of radiation dose reduction on the assessment of the tracheal lumen on expiratory multidetector computed tomographic (MDCT) images of pediatric patients referred for evaluation for tracheomalacia (TM). MATERIALS AND METHODS The hospital information system was used to retrospectively identify 20 standard-dose and 20 reduced-dose paired inspiratory and expiratory MDCT studies performed for the evaluation of suspected TM in pediatric patients (aged <or= 18 years). The reduced-dose technique used a 50% reduction of the tube current for the expiratory portion of the study compared to the standard-dose technique. Two experienced pediatric radiologists, who were blinded to the tube current of the study, reported their levels of confidence for measuring the tracheal lumen using a four-point scale ranging from zero (no confidence) to three (highest level of confidence). The difference in confidence level between the two groups of studies was analyzed using the Mann-Whitney U test. The percentage of radiation dose reduction using the reduced-dose technique in comparison to the standard-dose technique was estimated using anthropomorphic thorax phantoms. The presence or absence of TM (>or=50% expiratory reduction in tracheal cross-sectional luminal area) on MDCT imaging was compared to bronchoscopic results for the subset of 32 patients who underwent both procedures. RESULTS A high level of confidence was reported for measuring the tracheal lumen on MDCT imaging for both standard-dose (median, 3.0) and reduced-dose (median, 3.0) expiratory sequences (P = .80). The total radiation dose of the paired inspiratory-expiratory computed tomographic (CT) exam was decreased by 23% with the reduced-dose technique. TM was diagnosed by CT imaging in seven patients who underwent standard-dose and six patients who underwent reduced-dose paired inspiratory and expiratory MDCT studies. CT results for the presence or absence of TM were concordant with the results of bronchoscopy in all 32 patients who underwent both procedures. CONCLUSION The radiation dose of paired inspiratory-expiratory CT imaging can be reduced by 23% while maintaining similar diagnostic confidence for assessment of the tracheal lumen compared to a standard-dose technique in pediatric patients. Thus, a reduced-dose technique is recommended for evaluating TM in children.

Preoperative MDCT evaluation of congenital lung anomalies in children: comparison of axial, multiplanar, and 3D images.

OBJECTIVE The objective of our study was to compare the preoperative diagnostic accuracy of axial, multiplanar, and 3D MDCT images for evaluating congenital lung anomalies in pediatric patients and to assess the potential added diagnostic value of multiplanar and 3D MDCT images in this setting. MATERIALS AND METHODS We used our hospital information system to identify all consecutive pediatric patients younger than 18 years who had undergone preoperative MDCT angiography and had a pathologically proven congenital lung anomaly between June 2005 and February 2010. Each MDCT examination was reviewed independently by two experienced pediatric radiologists for the types, location, associated mass effect, and associated anomalous vessels of congenital lung anomalies on axial, multiplanar, and 3D MDCT images. The final diagnosis was determined by surgical and pathologic findings. Diagnostic accuracy, confidence level of diagnosis (scale of 1-3: 1 = highest confidence and 3 = lowest), perceived added diagnostic value of multiplanar or 3D MDCT images (scale of 1-5: 5 = highest added diagnostic value and 1 = lowest), and interobserver kappa agreement were evaluated. RESULTS The final study cohort consisted of 46 pediatric patients (28 males and 18 females; mean age, 5.6 ± 6 [SD] months; range, 1 day-50 months). Histopathologic diagnoses included congenital pulmonary airway malformation (n = 19, 41%), sequestration (n = 15, 33%), congenital lobar emphysema (n = 7, 15%), and bronchogenic cyst (n = 5, 11%). Both independent reviewers correctly diagnosed types, location, associated mass effect, and associated anomalous arteries of all congenital lung anomalies with high accuracy (100%) and confidence level (mean confidence level < 1.2) on each type of image display (axial, multiplanar, and 3D). However, for the detection of anomalous veins, multiplanar and 3D images were associated with greater diagnostic accuracy and higher confidence level than axial images alone. Specifically, diagnostic accuracy for the detection of anomalous veins (n = 15; 33%) was 60% (9/15 cases) for axial MDCT images, 80% (12/15) for multiplanar MDCT images, and 100% (15/15) for 3D MDCT images (Friedman test, p = 0.011). Confidence levels for the detection of anomalous veins were significantly higher with 3D MDCT images (mean level = 1.0) and multiplanar MDCT images (mean level = 1.5) compared with axial MDCT images alone (mean level = 2.6) (Friedman test, p < 0.01). Both multiplanar and 3D MDCT images were found to provide added diagnostic value for accurately detecting anomalous veins associated with congenial lung anomalies (paired Student t tests, p < 0.012). CONCLUSION Axial MDCT images allow accurate diagnosis of the types, location, associated mass effect, and anomalous arteries of congenital lung anomalies, but supplemental multiplanar and 3D MDCT images add diagnostic value for the evaluation of congenital lung lesions associated with anomalous veins.

Expiratory Volumetric MDCT Evaluation of Air Trapping in Pediatric Patients With and Without Tracheomalacia

OBJECTIVE The purpose of this study was to use paired inspiratory-expiratory volumetric MDCT to compare the frequency, severity, and pattern of air trapping in pediatric patients with tracheomalacia with the findings in children without tracheomalacia. MATERIALS AND METHODS The study group consisted of 15 consecutively registered pediatric patients (younger than 18 years) who had tracheomalacia, defined as 50% or greater reduction in tracheal cross-sectional luminal area between end inspiration and end expiration, diagnosed with MDCT and confirmed with bronchoscopy. The comparison group consisted of 15 consecutively registered pediatric patients without evidence of tracheomalacia at MDCT and bronchoscopy. Two blinded pediatric radiologists working in consensus interpreted the randomly viewed end-expiratory thin-section CT images of both groups of children for the presence, severity, and pattern of air trapping at three anatomic levels (upper, middle, and lower lung zones). The severity of air trapping was graded visually on a 5-point scale. The total air trapping scores, obtained by summing the values for the three anatomic levels for the study and comparison groups, were compared by Wilcoxons rank sum test. The pattern of air trapping was categorized as lobular, segmental, lobar, diffuse, or mixed, and the patterns in the two study groups were compared by Pearsons chi-square test. RESULTS The study cohort with tracheomalacia consisted of 15 patients (10 boys, five girls; mean age, 2.4 +/- 2.8 years; range, 1 month-11.8 years). The comparison group without tracheomalacia consisted of 15 patients (nine boys, six girls; mean age, 2.7 +/- 2.4 years; range, 1 month-8.1 years). Air trapping was identified in all 15 patients with tracheomalacia (median score, 5.0; range, 3-11) and in 10 of 15 children (67%) in the comparison group (median score, 3.0; range, 1-4). The median total air trapping score was significantly higher in the study cohort than in the comparison group (p = 0.002), but there were no significant differences in the air trapping patterns between the study groups (p = 0.53). CONCLUSION Pediatric patients with tracheomalacia have a higher frequency and greater severity of air trapping than do children without tracheomalacia.

Motion artifact on high-resolution CT images of pediatric patients: comparison of volumetric and axial CT methods.

OBJECTIVE The purpose of this study was to address the controversy whether the quality of volumetric high-resolution CT (HRCT) images is as good as that of axial nonvolumetric HRCT images by assessing the degree of motion artifact on images acquired with the two methods at MDCT of pediatric patients with known or suspected lung disease. MATERIALS AND METHODS A search of the hospital information system was conducted to identify the cases of pediatric patients with clinically suspected or known interstitial lung disease who underwent 16-MDCT of the chest with both volumetric and axial HRCT acquisitions (both 1.25-mm slice thickness) from March 2005 to July 2008. Two pediatric radiologists reviewed the images for the presence of motion artifacts at three anatomic levels (upper, middle, and lower lung zones). Motion artifacts were given numerical grades representing no artifact to severe artifact, and the paired Students t test was used to compare the scores for the two acquisition methods. A total motion score for each acquisition was calculated by summing the scores for each of the three lung zones, and the scores for the two imaging methods were compared. Correlation between degree of motion artifact and age was evaluated. Effective radiation doses were estimated for volumetric and axial CT acquisitions. RESULTS The study population consisted of 54 children (28 boys, 26 girls; mean age, 11.7 +/- 3.8 years; range, 5-18 years; eight inpatients, 46 outpatients) who underwent a total of 54 MDCT chest studies with volumetric and axial HRCT acquisitions. Motion artifact scores were higher for axial than for volumetric HRCT images of the upper (1.2 vs 1.0), middle (1.6 vs 1.2), and lower (2.2 vs 1.5) lung zones (p < 0.05 at each level). The total motion score of the axial HRCT images (mean, 5; range, 1-9) was higher than that of the volumetric HRCT images (mean, 3.6; range, 1-8) (p < 0.05). Younger age correlated with higher motion artifact score on axial HRCT images (r = -0.36, p < 0.01), whereas no correlation was found between age and motion artifact score on volumetric HRCT images (r = -0.12, p = 0.38). The effective radiation doses were 0.57 mSv for axial HRCT acquisition and 7.6 mSv for volumetric acquisition. The addition of axial acquisition increased the total radiation dose of the MDCT examination 7.1%. CONCLUSION At CT of pediatric patients, reconstructed HRCT images from volumetric MDCT acquisition have significantly less motion artifact than images obtained with traditional axial acquisition.

Tracheobronchomalacia in pediatric patients with esophageal atresia: Comparison of diagnostic laryngoscopy/bronchoscopy and dynamic airway multidetector computed tomography

PURPOSE Diagnostic laryngoscopy and bronchoscopy (DLB) has been the traditional preoperative diagnostic modality for evaluating presence and severity of tracheobronchomalacia (TBM), and requires anesthesia. Alternatively, multidetector computed tomography (MDCT) is potentially a noninvasive modality that provides high-resolution, 3-dimensional (3D) imaging of the thorax providing preoperative guidance for pediatric surgeons. This study compares MDCT with intraoperative DLB in the assessment of TBM in symptomatic pediatric patients with esophageal atresia (EA). METHODS Following IRB approval all pediatric patients (≤18 years) who had EA and who underwent an MDCT study as a preoperative evaluation of TBM prior to aortopexy were retrospectively reviewed. Patients with incomplete reports on intraoperative DLB or MDCT studies were excluded. Two pediatric radiologists independently evaluated all MDCT studies in a blinded fashion. On both DLB and MDCT studies, TBM was scored as present or absent in five anatomic segments: upper, middle, and lower trachea, as well as right and left main stem bronchi. Operative reports including DLB findings were reviewed and compared to findings from MDCT study using the chance corrected kappa (κ) coefficient. Diagnostic accuracy of dynamic MDCT for detecting TBM was determined by sensitivity and specificity, and interobserver agreement between two radiology reviewers was measured by the kappa statistic. RESULTS The final study population included 18 patients (8 males and 10 females) with ages ranging from 1month to 11years (median: 7 months). Their presenting clinical symptoms included apneic spells (n=15, 83%) and failure to extubate (n=3, 17%). The overall diagnostic accuracy of dynamic airway MDCT compared to DLB was 91% (82/90 possible segments for TBM) with excellent overall agreement across all 5 anatomic segments (κ=0.82, p<0.001). The agreements for upper, mid, lower trachea, and right and left trachea were 89% (κ=0.73, p<0.001), 94% (κ=0.85, p<0.001), 89% (κ=0.76, p<0.001), 94% (κ=0.82, p<0.001), and 89% (κ=0.61, p=0.005); respectively. Interobserver agreement between two radiologists was excellent (κ=0.98, 95% confidence interval: 0.94-1.00, p<0.001) with only 1 disagreement between two radiologists that was found for the left main bronchus. Fifteen (83.3%) of the patients clinically improved after the aortopexy. CONCLUSION MDCT with 3D imaging is a highly accurate and reliable preoperative noninvasive imaging modality for evaluating TBM in pediatric patients with EA providing anatomic information consistent with and complimentary to bronchoscopy.

Utility of Salivagram in Pulmonary Aspiration in Pediatric Patients: Comparison of Salivagram and Chest Radiography

OBJECTIVE The purpose of our study was to correlate the results of the radionuclide salivagram with the corresponding chest radiography findings on patients being evaluated for salivary aspiration to determine the utility of the salivagram. MATERIALS AND METHODS We identified 222 patients younger than 21 years who underwent salivagram and chest radiography within 3 months of each other. Salivagrams were blindly interpreted by two readers and chest radiographs were blindly interpreted by two other readers. The kappa coefficient with 95% CI was used to measure the level of interobserver agreement. Multivariate logistic regression was applied to determine whether age, sex, and neurologic diagnosis were predictors of a positive salivagram, with the odds ratio used to estimate association. RESULTS Interobserver agreement on salivagram interpretation was excellent (κ = 0.988; p < 0.0001; 95% CI, 0.968-1.000). Interobserver agreement on chest radiography interpretation was excellent (κ = 0.905; p < 0.0001; 95% CI, 0.845-0.965). The salivagram was positive for aspiration in 55 patients (25%). Chest radiography was positive in 54 patients (24%). When the interpretations of the salivagram (normal or abnormal) were compared with interpretations of the chest radiograph (normal or abnormal), there were 213 agreements and nine disagreements (intermethod agreement κ = 0.891; p < 0.0001; 95% CI, 0.831-0.952). Independent of age (p = 0.80) and sex (p = 0.31), patients with a neurologic diagnosis had odds of a positive salivagram 5.6 times higher than other diagnoses (odds ratio = 5.6; 95% CI, 2.5-13.1; p < 0.0001). CONCLUSION Infants with abnormal findings on salivagrams also had a high rate of abnormal findings on chest radiographs, which may indicate that some of the lung disease may be due to aspirated saliva. Salivagrams may be useful in children at risk of aspiration to identify those in whom intervention may help minimize the consequences of aspiration.

Pulmonary MDCT Angiography: Value of Multiplanar Reformatted Images in Detecting Pulmonary Embolism in Children

OBJECTIVE The purpose of this study was to determine whether the use of multiplanar reformatted (MPR) MDCT images in the diagnosis of pulmonary embolism (PE) in children by faculty pediatric radiologists and radiology residents affects reader performance parameters and adds diagnostic value compared with the use of axial MDCT images alone. MATERIALS AND METHODS This retrospective study was conducted with the images of 60 children (28 boys, 32 girls; mean age, 14.7 ± 3.5 years; range, 3.2-18 years) who consecutively underwent pulmonary CT angiography (CTA) for clinically suspected PE. Two faculty pediatric radiologists and two radiology residents independently reviewed images from each study initially using only axial MDCT images and later using MPR MDCT images in any x-, y-, or z-axis. Diagnostic accuracy, confidence level (1-5 ordinal scale), and interpretation time for MPR MDCT images were compared with those for axial MDCT images by use of the McNemar test and paired Student t test. The kappa coefficient was calculated to assess interobserver agreement. Diagnostic accuracy was compared between faculty pediatric radiologists and radiology residents by logistic regression analysis, and confidence level, interpretation time, and added diagnostic value were evaluated by analysis of variance. RESULTS Nine of 60 pulmonary CTA studies (15%) were found to show PE. Diagnostic accuracy in detection of PE ranged from 91.7% to 100% (mean, 96.7%) with no significant differences between axial and MPR MDCT images (McNemar test for matched binary pairs, p > 0.50 for each reviewer). Logistic regression showed no significant difference between faculty pediatric radiologists and radiology residents in diagnostic accuracy in detection of PE on axial MDCT images (p = 0.48) or MPR MDCT images (p = 0.24). Confidence level and interobserver agreement were significantly higher and average interpretation time was longer in the evaluation of PE with MPR MDCT images than with axial MDCT images for all reviewers (p < 0.001). Compared with faculty pediatric radiologists, radiology residents had significantly greater increases in confidence level, interobserver agreement, interpretation time, and added diagnostic value using MPR MDCT images than they did using axial MDCT images to diagnose PE (p < 0.001). CONCLUSION Use of MPR MDCT images for pulmonary CTA in the diagnosis of PE in children significantly increases confidence, interobserver agreement, and interpretation time among faculty pediatric radiologists and radiology residents. Because use of MPR MDCT images results in significantly greater improvements in reading parameters for residents than for faculty members, the routine use of this technique by trainees should be encouraged.

Pulmonary Embolism Detected by Pulmonary MDCT Angiography in Older Children and Young Adults: Risk Factor Assessment

OBJECTIVE The purpose of this article is to determine the risk factors for pulmonary embolism (PE) among older children and young adults who underwent pulmonary CT angiography (CTA) for evaluation of clinically suspected PE. MATERIALS AND METHODS We used our hospital information system to retrospectively identify all consecutive patients 19-25 years old who underwent pulmonary CTA for evaluation of clinically suspected PE between July 2004 and March 2011. Two experienced pediatric radiologists retrospectively and independently reviewed a series of 116 consecutive pulmonary CTA studies from this population. Each examination was reviewed for the presence of PE. Seven possible risk factors (immobilization, prior PE or deep venous thrombosis [DVT], cardiac disease, malignancy, hypercoagulable state, excess estrogen, and central venous line placement) were compared between patients with and without PE using univariate statistics, including Student t test and Pearson chi-square test. Multiple logistic regression modeling was used to identify independent risk factors for PE. Receiver operating characteristic curve analysis was applied to determine the optimal cutoff number of risk factors for predicting a pulmonary CTA result positive for PE. RESULTS The study population consisted of 116 patients (34 men and 82 women; mean age, 20.7 ± 1.8 years; range, 18.6-25.4 years) who underwent a total of 116 pulmonary CTA studies. Sixteen (14%) of 116 patients were found to have PE on pulmonary CTA. The level of involvement of PE was segmental in 16 of 31 PEs (52%), lobar in eight (26%), subsegmental in five (16%), and main or central in two (6%). Three risk factors--immobilization (p < 0.001), history of prior PE or DVT (p = 0.001), and cardiac disease (p = 0.004)--were found to be significant independent risk factors for the presence of PE detected by pulmonary CTA. When two or more risk factors were used as the clinical threshold, the sensitivity for positive PE was 75% (12/16 patients) and the specificity was 99% (99/100 patients). CONCLUSION The use of risk factor assessment as a first-line triage tool has the potential to guide more appropriate use of pulmonary CTA in this population, with potential associated reductions in radiation exposure and costs.

Screening of Asymptomatic Children for Tuberculosis: Is a Lateral Chest Radiograph Routinely Indicated?

RATIONALE AND OBJECTIVES The aim of this study was to determine whether a lateral chest radiograph provides additional diagnostic information to a posteroanterior (PA) radiograph in the screening of asymptomatic children with positive purified protein derivative (PPD) skin tests in a nonendemic area. MATERIALS AND METHODS This was an Institutional Review Board-approved, Health Insurance Portability and Accountability Act-compliant, retrospective study of 605 consecutive pediatric patients (294 males, 311 females; mean age, 10.8 ± 5.2 years) with positive PPD skin test results, who underwent PA and lateral chest radiographs between July 2003 and May 2009 at a tertiary care pediatric hospital in a nonendemic area for tuberculosis (TB). Two pediatric radiologists independently reviewed each chest radiograph for evidence of abnormalities that may be indicative of acute or chronic TB infection. The reviewers first analyzed the PA radiograph alone and subsequently evaluated the PA and the lateral radiograph together to determine whether any observed abnormality was identified only on the lateral radiograph. When an abnormality was detected on both PA and lateral radiographs, the reviewers determined whether the abnormality on the lateral radiograph changed the reviewers decision based on the PA radiograph alone. Assessment of nonconcordance between PA and lateral chest radiographs for each reviewer was evaluated by the McNemar test of matched binary pairs. Agreement between reviewers for detecting abnormalities on radiographs was evaluated by using the kappa (κ) statistic. RESULTS The frequency of an abnormal chest radiograph related to TB was 1.8% (11/605). The PA radiograph showed abnormalities in all 11 (100%) children with radiographic abnormalities. Lateral radiographs showed abnormalities related to TB in 2 (18.2%) of 11 cases found to be abnormal on PA radiographs. Nine (81.8%) of 11 abnormalities on PA radiographs were not detected on the lateral chest radiographs. There was statistical evidence of nonconcordance between PA and lateral chest radiographs in detecting TB-related abnormalities for reviewer 1 (P < .001) and reviewer 2 (P = .004). In cases with abnormalities observed on both PA and lateral radiographs, there were no cases in which information obtained from the lateral chest radiograph resulted in a change in interpretation based on the PA radiograph alone. A high level of agreement was observed between the two independent reviewers in detecting TB-related abnormalities on PA radiographs (κ = 0.84, P < .001). CONCLUSIONS A PA radiograph alone is sufficient for TB screening of asymptomatic pediatric patients with positive PPD skin test results in an area non-endemic for TB.

Image Quality of Thoracic 64-MDCT Angiography: Imaging of Infants and Young Children With or Without General Anesthesia

OBJECTIVE The purpose of this study was to compare the image quality of thoracic CT angiography (CTA) studies performed with two techniques--with general anesthesia and without general anesthesia--for infants and for children younger than 5 years. MATERIALS AND METHODS All consecutively registered infants and young children (age, ≤ 5 years) who underwent contrast-enhanced thoracic CTA from November 2005 to October 2010 were categorized into two groups: general anesthesia and awake (i.e., no general anesthesia). Two radiologists independently evaluated image quality by quantifying the degree of motion artifact at three anatomic levels (upper, middle, and lower lung zones). Motion artifacts were graded on an ordinal scale (0, no motion; 1, mild; 2, moderate; 3, severe), and the Pearson chi-square test was used to assess whether the degree of motion artifact differed between the general anesthesia and awake groups in the upper, middle, and lower lung zones. Logistic regression analysis was performed to determine whether image quality based on the presence or absence of motion artifact in any lobe was related to general anesthesia versus the awake state; age and sex were covariates. Interobserver agreement between two reviewers was evaluated with kappa statistics. RESULTS There were a total of 135 patients (mean age 1.0 year), 95 in the awake group (70%) and 40 in the general anesthesia group (30%). No significant difference was found between the two groups in percentage of studies with motion artifact detected in each lung zone and the total motion artifact score. Results of multivariable logistic regression analysis indicated that image quality was not influenced by age (p = 0.52) or sex (p = 0.20). There was excellent interobserver kappa agreement between reviewers for detecting motion artifact in the upper, middle, and lower lung zones (all κ > 0.90, p < 0.001). CONCLUSION There is no significant difference in image quality of thoracic CTA with 64-MDCT assessed by degree of motion artifact with and without general anesthesia. The results of this study support use of thoracic CTA without general anesthesia in the care of young pediatric patients who meet screening criteria for awake imaging studies.