Spiral CT scanning technique in the detection of aspiration of LEGO foreign bodies.

BACKGROUND: Radiolucent foreign bodies (FBs) such as plastic objects and toys remain difficult to identify on conventional radiographs of the neck and chest. Children may present with a variety of respiratory complaints, which may or may not be due to a FB. OBJECTIVE: To determine whether radiolucent FBs such as plastic LEGOs and peanuts can be seen in the tracheobronchial tree or esophagus using low-dose spiral CT, and, if visible, to determine the optimal CT imaging technique. MATERIALS AND METHODS: Multiple spiral sequences were performed while varying the CT parameters and the presence and location of FBs in either the trachea or the esophagus first on a neck phantom and then a cadaver. Sequences were rated by three radiologists blinded to the presence of a FB using a single scoring system. RESULTS: The LEGO was well visualized in the trachea by all three readers (both lung and soft-tissue windowing: combined sensitivity 89 %, combined specificity 89 %) and to a lesser extent in the esophagus (combined sensitivity 31 %, combined specificity 100 %). The peanut was not well visualized (combined sensitivity < 35 %). The optimal technique for visualizing the LEGO was 120 kV, 90 mA, 3-mm collimation, 0.75 s/revolution, and 2.0 pitch. This allowed for coverage of the cadaver tracheobronchial tree (approximately 11 cm) in about 18 s. Although statistical power was low for detecting significant differences, all three readers noted higher average confidence ratings with lung windowing among 18 LEGO-in-trachea scans. CONCLUSION: Rapid, low-dose spiral CT may be used to visualize LEGO FBs in the airway or esophagus. Peanuts were not well visualized.

Power injection of contrast media using central venous catheters: feasibility, safety, and efficacy.

OBJECTIVE: This study evaluates the feasibility, safety, and efficacy of power-injecting IV contrast media through central venous catheters for CT examinations. SUBJECTS AND METHODS: Two hundred ninety-five CT examinations were performed during an 18-month period in 225 patients with indwelling central venous catheters. Patients were randomized to power injection either through peripheral IV catheter or through central venous catheter. Feasibility was defined as the percentage of patients with contrast material injected successfully through the randomized access route. Safety was evaluated by comparing patients with complications. Efficacy was evaluated by comparing contrast enhancement of the thoracic aorta, pulmonary artery, abdominal aorta, and liver. RESULTS: Two hundred nine patients had randomization data recorded. One hundred three (94%) of 109 patients were successfully injected through their indwelling catheter compared with 42 (42%) of 100 through a peripherally placed IV catheter (p < 0.001). After reassignment for unsuccessful access, 174 patients underwent central venous catheter injection, and 51, peripheral IV catheter injection. No statistically significant difference was noted in the complications between the central venous catheter and peripheral IV catheter groups. Enhancement was greater in the thoracic aorta, pulmonary artery, and liver for the peripheral IV catheter group (p < 0.03). CONCLUSION: Power injection of contrast media through central venous catheters for CT examinations is feasible and safe when set hospital guidelines and injection protocols are followed. This technique provides an acceptable alternative in patients without adequate peripheral IV access when bolus contrast enhancement is desired.

Data analysis for detection and localization of multiple abnormalities with application to mammography.

RATIONALE AND OBJECTIVES: In assessing diagnostic accuracy it is often essential to determine the reader's ability both to detect and to correctly locate multiple abnormalities per patient. The authors developed a new approach for the detection and localization of multiple abnormalities and compared it with other approaches. MATERIALS AND METHODS: The new approach involves partitioning the image into multiple regions of interest (ROIs). The reader assigns a confidence score to each ROI. Statistical methods for clustered data are used to assess and compare reader accuracy. The authors applied this new method to a reader-performance study of conventional film images and digitized images used to detect and locate malignant breast cancer lesions. RESULTS: The ROI-based approach, the free-response receiver operating characteristic (FROC) curve, and the patient-based approach handle the estimation of the false-positive rate (FPR) quite differently. These differences affect the measures of the respective areas under the curves. In the ROI-based approach the denominator is the number of ROIs without a malignant lesion. In the FROC approach the average number of false-positive findings per patient is plotted on the x axis of the curve. In contrast, the patient-based approach mishandles the FPR by ignoring multiple detection and/or localization errors in the same patient. The FROC approach does not lend itself easily to statistical evaluations. CONCLUSION: The ROI-based approach appropriately captures both the detection and localization tasks. The interpretation of the ROI-based accuracy measures is simple and clinically relevant. There are statistical methods for estimating and comparing ROI-based estimates of accuracy.

Triphasic helical CT of the kidneys: contribution of vascular phase scanning in patients before urologic surgery.

OBJECTIVE: The purpose of this study was to evaluate the potential benefits of performing vascular phase scanning of the kidneys in addition to unenhanced and parenchymal phase contrast-enhanced CT in patients being examined for urologic surgery. MATERIALS AND METHODS: Parenchymal and vascular phase images from triphasic renal helical CT of 50 patients were sequentially evaluated in a randomized, retrospective fashion by two independent observers. The number of renal arteries and veins and the presence of vein or collecting system anomalies were recorded for each scan phase along with a subjective 10-point-scale score of the visibility of the vasculature and collecting system. Correlation of these findings was made with surgical or angiographic findings in 67 of the 87 kidneys and was made by consensus review in the remaining 20 kidneys. RESULTS: Accessory renal arteries were seen significantly more often (p < .05, chi-square test) on the vascular phase scans. The subjective scores for the visibility of the renal arteries and renal veins were significantly higher on the vascular phase scans (p < .0001, Wilcoxon's rank sum test). The subjective scores for the visibility of the filling of the collecting system and renal pelvis were significantly higher for the parenchymal phase scans, despite the use of a small contrast bolus before each scan (p < .0001, Wilcoxon's rank sum test). CONCLUSION; Triphasic renal CT better reveals the artery and vein anatomy of the kidney than does parenchymal phase imaging only. Triphasic helical CT is indicated in patients undergoing planning for urologic surgery when vascular anatomy is clinically important.

Postoperative anal canal length predicts outcome in patients having sphincter repair for fecal incontinence.

PURPOSE: Controversy exists in regard to the prognostic value of clinical data and physiological tests in patients undergoing sphincter repair for fecal incontinence. The aim of this study was to identify prognostic factors. METHODS: Between 1986 and 1996, 405 consecutive patients had a sphincter repair for fecal incontinence. Preoperative and postoperative manometric data were available on 51 of these patients, and these patients' charts were reviewed retrospectively. Preoperative and postoperative continence was scored using the four-level scale of Browning and Parks. Mean follow-up was 16.2 (median, 6; range, 1-96) months. Mean age was 41 (median, 36; range, 21-80) years, and 46 (90 percent) patients were female. RESULTS: Twenty-three (45 percent) patients had perfect continence postoperatively, whereas 41 (80 percent) patients demonstrated improvement in continence score after sphincter repair. Using univariate analysis, various clinical and anal physiologic data were analyzed for an association with postoperative continence score. Postoperative mean resting pressure and postoperative anal canal length were both significantly related to postoperative continence (r(s)B for Spearman correlation coefficient to differentiate from r for the Pearson coefficient. = 0.442; P = 0.0012; and r(s) = 0.440; P = 0.0012, respectively), whereas postoperative mean squeeze pressure was not (r(s) = 0.273; P = 0.0529). Postoperative mean resting pressure and anal canal length were entered into a logistic regression model. Postoperative mean resting pressure was not significant (P = 0.6643), and when it was dropped from the model, postoperative anal canal length was highly significant (estimated odds ratio, 3.2; 95 percent confidence interval, 1.1-9.3; P = 0.0047) in predicting postoperative continence. CONCLUSIONS: No preoperative data predicted functional outcome, and in contrast to other studies, postoperative anal canal length provides the best prediction of postoperative continence.

Confidence intervals for the receiver operating characteristic area in studies with small samples.

RATIONALE AND OBJECTIVES: The authors performed this study to address two practical questions. First, how large does the sample size need to be for confidence intervals (CIs) based on the usual asymptotic methods to be appropriate? Second, when the sample size is smaller than this threshold, what alternative method of CI construction should be used? MATERIALS AND METHODS: The authors performed a Monte Carlo simulation study where 95% CIs were constructed for the receiver operating characteristic (ROC) area and for the difference between two ROC areas for rating and continuous test results--for ROC areas of moderate and high accuracy--by using both parametric and nonparametric estimation methods. Alternative methods evaluated included several bootstrap CIs and CIs with the Student t distribution. RESULTS: For the difference between two ROC areas, CIs based on the asymptotic theory provided adequate coverage even when the sample size was very small (20 patients). In contrast, for a single ROC area, the asymptotic methods do not provide adequate CI coverage for small samples; for ROC areas of high accuracy, the sample size must be large (more than 200 patients) for the asymptotic methods to be applicable. The recommended alternative (bootstrap percentile, bootstrap t, or bootstrap bias-corrected accelerated method) depends on the estimation approach, format of the test results, and ROC area. CONCLUSION: Currently, there is not a single best alternative for constructing CIs for a single ROC area for small samples.

Comparison of examination times between CT scanners: are the newer scanners faster?

OBJECTIVE: The purpose of this study was to determine if a newer technology helical CT scanner can reduce CT examination times. MATERIALS AND METHODS: Data from 1049 CT examinations were recorded prospectively during a 5-week period. "Room time" was defined as the time each patient spent in the CT room (time patient exited minus time patient entered) and "scanner time" was defined as the time a scanner was dedicated to a specific patient (longer of either time that image processing was complete minus time patient entered room, or total time that patient spent in the scanner room). Data to calculate the room and scanner times were recorded along with the scanner type, examination protocol, and five other covariates. Both times were calculated for the 10 most common examination protocols (n = 769 patients) and compared between the older and newer model CT scanner using analysis of covariance models. The most common protocols were abdomen and pelvis (n = 211); head (n = 146); chest (n = 99); simple sinus (n = 99); and chest, abdomen, and pelvis (n = 68). RESULTS: The mean room and scanner times, adjusted for covariates, were both significantly shorter for the newer scanner (p = .0001). The results for room time were statistically significant for six of the 10 examination protocols (84% of examinations). Likewise, the results for scanner time were statistically significant for four examination protocols (68% of examinations). Examination times were longer for inpatients (p = .0001) and when problems occurred during the examination (p = .0001). Sex and age did not significantly affect examination times (p > .08). CONCLUSION: The newer helical CT scanner we studied significantly reduced the time for many types of examinations.

Intramural hematoma of the thoracic aorta: MR image findings and their prognostic implications.

PURPOSE: To evaluate magnetic resonance (MR) imaging findings of intramural hematoma of the thoracic aorta and their relationship to prognosis. MATERIALS AND METHODS: MR images of 22 patients with intramural hematoma of the thoracic aorta were reviewed retrospectively. Site, thickness, degree of mural involvement, and signal intensity on spin-echo (SE) and cine gradient-echo (GRE) images of the hematoma were noted. MR findings of patients who did and those who did not develop complications were compared. RESULTS: Hematoma site was the only MR finding that correlated significantly with patient outcome. Complication frequencies in four (80%) of five patients with hematoma of the ascending aorta (type A) and in two (12%) of 17 patients with hematoma of the descending aorta (type B) were significantly different (P = .009). There were moderately strong correlations between days after symptom onset and signal intensity of the hematoma on SE (r = 0.78) and GRE (r = 0.72) images. MR images of two of three patients who developed early-subacute complications showed signal intensity changes of the hematoma that were consistent with recurrent bleeding. CONCLUSION: Patients with MR findings consistent with type A intramural hematoma of the thoracic aorta should undergo surgery. In cases of type B intramural hematoma of the thoracic aorta, MR imaging can be useful for detecting complete resolution or impending complications of the hematoma.

Multiple recurrences of acute tumor lysis syndrome in an indolent non-Hodgkin's lymphoma.

Acute tumor lysis syndrome (ATLS) is an entity consisting of combinations of hyperuricemia, lactic acidosis, hyperkalemia, hyperphosphatemia, and hypocalcemia and occurring generally in aggressive, rapidly proliferating lymphoproliferative disorders with high tumor burdens. A patient is described with a diffuse intermediately differentiated lymphocytic lymphoma, considered by most an indolent B-cell non-Hodgkin's lymphoma, in whom developed multiple recurrences of ATLS after treatment when tumor regrowth occurred between cycles of therapy. The mitotic rate of this lymphoma was relatively high (30-80 mitoses/ten high-power fields). Lymph proliferative disorders with a high mitotic rate, and large tumor burden, regardless of histologic features, should be treated prophylactically against tumor lysis if regrowth between cycles occurs.