Developmental effects of multiple looks in speech sound discrimination.

PURPOSE: The change/no-change procedure (J. E. Sussman & A. E. Carney, 1989), which assesses speech discrimination, has been used under the assumption that the number of stimulus presentations does not influence performance. Motivated by the tenets of the multiple looks hypothesis (N. F. Viemeister & G. H. Wakefield, 1991), work by R. F. Holt and A. E. Carney (2005) called this assumption into question (at least for adults): Nonsense syllable discrimination improved with more stimulus presentations. This study investigates the nature of developmental differences and the effects of multiple stimulus presentations in the change/no-change procedure. METHOD: Thirty normal-hearing children, ages 4.0-5.9 years, were tested on 3 consonant-vowel contrasts at various signal-to-noise ratios using combinations of 2 and 4 standard and comparison stimulus repetitions. RESULTS: Although performance fell below that which is predicted by the multiple looks hypothesis in most conditions, discrimination was enhanced with more stimulus repetitions for 1 speech contrast. The relative influence of standard and comparison stimulus repetitions varied across the speech contrasts in a manner different from that of adults. CONCLUSION: Despite providing no additional sensory information, multiple stimulus repetitions enhanced children's discrimination of 1 set of nonsense syllables. The results have implications for models of developmental speech perception and assessing speech discrimination in children.     

Heterogeneous splenic enhancement patterns on spiral CT images in children: minimizing misinterpretation

PURPOSE: To (a) determine the appearances and timing of heterogeneous splenic enhancement at spiral computed tomography (CT) and (b) identify variables influencing heterogeneous splenic enhancement. MATERIALS AND METHODS: Sequential isolevel (24-mAs) CT images of the spleen obtained at 6-second intervals after initiation of contrast material injection in 112 children (mean age, 4.5 years) were reviewed. Heterogeneity characteristics assessed included type, onset, maximum, and resolution. Relationship to variables (injection rate, age, splenomegaly) was assessed with the Fisher exact test. RESULTS: Eighty-one of the 112 patients (72%) had transient heterogeneity: archiform (45 patients), diffuse (25 patients), and focal (11 patients). Mean times were as follows: initial visualization after onset of contrast material injection, 19.2 seconds; maximum heterogeneity, 27.3 seconds; and resolution, 47.4 seconds. Statistically significant relationships were seen between frequency of heterogeneity and injection rate (> or = 1 mL/sec, 82%; < 1 mL/sec, 50% [P = .001]), age (> 1 year, 76%; < or = 1 year, 46% [P = .04]), and splenomegaly (present, 20%; absent, 77% [P = .048]). CONCLUSION: Heterogeneous splenic contrast enhancement is common, has several patterns of appearance, and is predictably encountered during the 70 seconds after the initiation of contrast material injection. Injection rate, age, and presence of splenic disease influence the frequency with which these artifacts are encountered.     

Optimizing contrast-enhanced abdominal CT in infants and children using bolus tracking

OBJECTIVE: Manual administration of IV contrast material results in unpredictable injection rates. Our purpose was to determine the effect of bolus tracking on overall abdominal helical CT scan quality, particularly on hepatic enhancement, in children with manually administered contrast media. MATERIALS AND METHODS: We compared 33 abdominal helical CT scans of 29 children in whom bolus tracking was used with 22 CT scans of a control group of 21 children in whom bolus tracking was not used. All contrast material was administered by manual injection. Qualitative assessment was made of organ and vessel enhancement and overall scan appearance. Quantitative assessment using region-of-interest cursors was performed at three anatomic levels, and the results for the two groups of children were compared. RESULTS: Qualitative comparison of enhancement parameters between the bolus tracking group (number given first) and the control group (number given second) yielded the following: splenic artifact in 9% versus 23% (p = .24); inferior vena cava flow artifact in 3% versus 27% (p = .01); scanning during the nephrographic phase in 89% versus 59% (p = .02); and good quality grade in 79% versus 64% (p = .23). Significantly greater hepatic enhancement (as measured in mean Hounsfield units) was achieved in the bolus tracking group than in the control group at the superior (48.5 versus 28.6; p < .001), middle (47.9 versus 32.3; p < .001), and inferior (48.2 versus 36.5; p = .01) levels. Hepatic enhancement increased significantly from the superior to the inferior level in the control group (p < .02), whereas enhancement was homogeneous in the bolus tracking group (p > .50). CONCLUSION: Bolus tracking provides improved contrast enhancement, including significantly greater hepatic enhancement, during abdominal helical CT in children in whom the rate of injection of contrast material is unpredictable.     

Double Aortic Arch with Aortic Atresia and Left-Sided Type B Interruption

Aortic valve atresia with interruption of the aortic arch is an extremely rare anomaly; only eleven cases of this anomaly have been reported to date. In the absence of additional sources of blood flow to the ascending aorta, aortic valve atresia with interruption of the aortic arch is fatal. We present, to the best of our knowledge, the first case of a live birth with aortic valve atresia and interrupted left aortic arch (type B) without evidence of an aorticopulmonary communication or ductal supply to the native ascending aorta. Instead, blood flow to the native aortic root was derived from a persistent right embryonic dorsal aorta.     

Minimizing radiation dose for pediatric body applications of single-detector helical CT: strategies at a large Children's Hospital

Adjustments of the standard helical CT protocols for adults can result in reduced radiation dose when imaging children. It is the radiologist's responsibility to critically evaluate the CT techniques used at their institution. Adjustments to CT protocols should be made to choose the appropriate mA and pitch when imaging children.     

Improved pediatric multidetector body CT using a size-based color-coded format

OBJECTIVE: CT technique should be adjusted while scanning infants and children. One format that has proven successful in simplifying pediatric care and reducing medical error is the size-based, color-coded Broselow-Luten pediatric system. This color-coded system can serve as a format for CT protocols. The purpose of this investigation was to compare variation (or error) occurrence and technologist preference for conventional and color-coded formats for pediatric multidetector body CT protocols. MATERIALS AND METHODS: Multidetector CT examinations were set up using either a conventional or a color-coded format for a period of 6 weeks each. Variations (errors) from protocol parameters (including tube current, detector configuration, table speed, and IV contrast media dose) were tabulated. Qualitative assessment consisted of a survey of CT technologists (n = 20) for preference in six areas related to ease of use and clarity of the formats. RESULTS: There were 44 CT examinations (n = 30 infants and children) in the conventional group and 55 CT examinations (n = 31 infants and children) in the color-coded protocol format group. Overall, the number of errors was significantly less in the color-coded group (p < 0.01), with a significantly lower error percentage in individual parameters affecting radiation dose, including tube current, detector configuration, and table speed (p < 0.05). In all areas, the color-coded format was preferred over the conventional format (p < 0.0003). CONCLUSION: Color-coded CT formatting is an extension of a clinical color-coded system. This system provides an easy, expeditious, consistent, and preferable format for general pediatric body CT protocols. Most importantly, the color-coded system can reduce variations (errors) in the radiology department.     

Reduced frequency of sedation of young children with multisection helical CT

PURPOSE: To determine whether the use of multisection helical computed tomography (CT) can decrease the need for sedation compared with single-section helical CT. MATERIALS AND METHODS: The number of children who required sedation to undergo body CT with a multisection helical scanner was recorded. The authors noted the type of examination and whether contrast material was used. The children were categorized according to age (< or = 17 years, < or = 6 years, < or = 1 year). RESULTS: In 219 CT examinations, only three children required sedation (1.4%). The sedation rate was 3% (three of 90) for children aged 6 years or younger and 8% (three of 37) for those aged 1 year or younger. Examinations were of the chest, abdomen, and pelvis in 68 patients, of the abdomen and pelvis in 112, and of the chest alone in 39. Contrast material was intravenously administered in 186 (85%) examinations. All scans were of diagnostic quality. CONCLUSION: The rate of sedation was reduced threefold with multisection helical CT compared with standard helical CT, and the need for sedation was eliminated in some age groups.     

Helical CT of the body: are settings adjusted for pediatric patients?

OBJECTIVE: Our objective was to determine whether adjustments related to patient age are made in the scanning parameters that are determinants of radiation dose for helical CT of pediatric patients. SUBJECTS AND METHODS: This prospective investigation included all body (chest and abdomen) helical CT examinations (n = 58) of neonates, infants, and children (n = 32) referred from outside institutions for whom radiologic consultation was requested. Information recorded included tube current, kilovoltage, collimation, and pitch. Examinations were arbitrarily grouped on the basis of the individual's age: group A, 0-4 years; group B, 5-8 years; group C, 9-12 years; and group D, 13-16 years old. RESULTS: Thirty-one percent (18/58) of the CT examinations were of the chest and 69% (40/58) were of the abdomen. Sixteen percent (9/58) of the CT examinations were combined chest and abdomen. In 22% (2/9) of these combined examinations, tube current was adjusted between the chest and abdomen CT; in one (11%) of these examinations, the tube current was higher for the chest than for the abdomen portion of the CT examination. The mean tube current setting for chest was 213 mA and was 206 mA for the abdomen, with no evident adjustment in tube current based on the age of the patient. Fifty-six percent of the examinations of neonates, infants, or children 8 years old or younger were performed at a collimation of greater than 5 mm and 53% of these examinations were performed using a pitch of 1.0. CONCLUSION: Pediatric helical CT parameters are not adjusted on the basis of the examination type or the age of the child. In particular, these results suggest that pediatric patients may be exposed to an unnecessarily high radiation dose during body CT.