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Objective: The purpose of this study is to compare diagnostic reference levels from a local European CT dose registry, using radiation-tracking software from a large patient sample, with preexisting European and North American diagnostic reference levels., Materials and Methods: Data (n = 43,761 CT scans obtained over the course of 2 years) for the European local CT dose registry were obtained from eight CT scanners at six institutions. Means, medians, and interquartile ranges of volumetric CT dose index (CTDI vol ), dose-length product (DLP), size-specific dose estimate, and effective dose values for CT examinations of the head, paranasal sinuses, thorax, pulmonary angiogram, abdomen-pelvis, renal-colic, thorax-abdomen-pelvis, and thoracoabdominal angiogram were obtained using radiation-tracking software. Metrics from this registry were compared with diagnostic reference levels from Canada and California (published in 2015), the American College of Radiology (ACR) dose index registry (2015), and national diagnostic reference levels from local CT dose registries in Switzerland (2010), the United Kingdom (2011), and Portugal (2015)., Results: Our local registry had a lower 75th percentile CTDI vol for all protocols than did the individual internationally sourced data. Compared with our study, the ACR dose index registry had higher 75th percentile CTDI vol values by 55% for head, 240% for thorax, 28% for abdomen-pelvis, 42% for thorax-abdomen-pelvis, 128% for pulmonary angiogram, 138% for renal-colic, and 58% for paranasal sinus studies., Conclusion: Our local registry had lower diagnostic reference level values than did existing European and North American diagnostic reference levels. Automated radiation-tracking software could be used to establish and update existing diagnostic reference levels because they are capable of analyzing large datasets meaningfully.

Objective: The purpose of this article is to investigate the magnitude of dose optimization for a manufacturer-recommended urolithiasis protocol in a second-generation dual-source CT scanner., Materials and Methods: Custom renal phantoms with 24 stones were scanned using the manufacturer-provided dual-energy CT protocol (tube A, 100 kVp and 210 reference mAs; tube B, 140 kVp and 162 reference mAs) and seven dose-optimized protocols in which the reference tube current-time product setting of tube A was reduced stepwise by 20 mAs. Detection and characterization of the stones was assessed. In the patient study, 25 patients underwent the manufacturer-provided dual-energy protocol and 25 patients underwent imaging with a dose-optimized protocol (tube A, 100 kVp and 90 reference mAs; tube B, 140 kVp and 70 reference mAs). Dose-length product (DLP), image noise, and contrast-to-noise ratio (CNR) were assessed. Subjective image quality was analyzed by three independent radiologists., Results: In the phantom study, the reference tube current-time product of tube A could be reduced from 210 to 90 mAs without losing the accuracy of detection or characterization of the calculi. In the patient study, the dose-optimized protocol resulted in a significant reduction of the average DLP by 51% compared with the standard protocol (219.4 vs 443.5 mGy·cm, respectively; p = 0.0001). The image noise was higher, and the CNR was lower, in the dose-optimized group than in the standard-dose group (p < 0.05). The subjective overall image quality of the dose-optimized CT examinations was rated as good, and that of the standard-dose CT examinations was rated as excellent (p = 0.001)., Conclusion: The in vitro and in vivo assessment revealed a potential for a 51% dose reduction of the manufacturer-recommended dual-energy CT protocol for urolithiasis without compromising the accuracy.

Objective: The purpose of this study was to assess the impact of a noise reduction technique on image quality, radiation dose, and low-contrast detectability in abdominal CT for obese patients., Materials and Methods: A liver phantom with 12 different tumors was designed, and fat rings were added to mimic intermediately sized and large patients. The intermediate and large phantoms were scanned with our standard abdominal CT protocol (image noise level of 15 HU and filtered back projection [FBP]). The large phantom was scanned with five different noise levels (10, 12.5, 15, 17.5, and 20 HU). All datasets for the large phantom were reconstructed with FBP and the noise reduction technique. The image noise and the contrast-to-noise ratio (CNR) were assessed. Tumor detection was independently performed by three radiologists in a blinded fashion., Results: The application of the noise reduction method to the large phantom decreased the measured image noise (range, -14.5% to -37.0%) and increased the CNR (range, 26.7-70.6%) compared with FBP at the same noise level (p < 0.001). However, noise reduction was unable to improve the sensitivity for tumor detection in the large phantom compared with FBP at the same noise level (p > 0.05). Applying a noise level of 15 HU, the overall sensitivity for tumor detection in the intermediate and large phantoms with FBP measured 75.5% and 87.7% and the radiation doses measured 42.0 and 23.7 mGy, respectively., Conclusion: Although noise reduction significantly improved the quantitative image quality in simulated large patients undergoing abdominal CT compared with FBP, no improvement was observed for low-contrast detectability.

Objective: The objective of our study was to compare the effect of dual-energy subtraction and bone suppression software alone and in combination with computer-aided detection (CAD) on the performance of human observers in lung nodule detection., Materials and Methods: One hundred one patients with from one to five lung nodules measuring 5-29 mm and 42 subjects with no nodules were retrospectively selected and randomized. Three independent radiologists marked suspicious-appearing lesions on the original chest radiographs, dual-energy subtraction images, and bone-suppressed images before and after postprocessing with CAD. Marks of the observers and CAD marks were compared with CT as the reference standard. Data were analyzed using nonparametric tests and the jackknife alternative free-response receiver operating characteristic (JAFROC) method., Results: Using dual-energy subtraction alone (p = 0.0198) or CAD alone (p = 0.0095) improved the detection rate compared with using the original conventional chest radiograph. The combination of bone suppression and CAD provided the highest sensitivity (51.6%) and the original nonenhanced conventional chest radiograph alone provided the lowest (46.9%; p = 0.0049). Dual-energy subtraction and bone suppression provided the same false-positive (p = 0.2702) and true-positive (p = 0.8451) rates. Up to 22.9% of lesions were found only by the CAD program and were missed by the readers. JAFROC showed no difference in the performance between modalities (p = 0.2742-0.5442)., Conclusion: Dual-energy subtraction and the electronic bone suppression program used in this study provided similar detection rates for pulmonary nodules. Additionally, CAD alone or combined with bone suppression can significantly improve the sensitivity of human observers for pulmonary nodule detection.

Objective: The purpose of this study was to simulate pulmonary emboli (PE) and image quality at low tube energy and reduced contrast material volume in normal-dose pulmonary CT angiography (CTA) images and to analyze the diagnostic accuracy with normal- and low-dose pulmonary CTA., Materials and Methods: Normal-dose pulmonary CTA examinations using 120 kVp and 100 mL of contrast material in 10 patients with no PE were retrospectively selected. The image characteristics of an 80-kVp low-dose pulmonary CTA protocol (patient exposure reduction, 57%) with 75 mL of contrast material were simulated. Four different sets of filling defects were computer simulated in identical locations in each normal-dose and corresponding low-dose examination, equaling 783 PE in 40 normal-dose and 40 low-dose datasets. Ten normal-dose and 10 low-dose examinations contained no emboli and were used as controls. The 100 pulmonary CTA studies were randomly assessed by three readers blinded to PE location and image quality. The results were assessed by nonparametric tests and Student t tests., Results: No difference was found between the CT protocols in terms of sensitivity, specificity, and positive and negative diagnostic likelihood ratios at all ramification levels of the pulmonary arteries (p = 0.343-1). The overall sensitivity and specificity with the normal and simulated low-dose protocols were 79.9% versus 81.3% and 98.0% versus 98.2% (p = 0.444 and 0.702), respectively. The diagnostic confidence (2.81 ± 0.39 vs 2.77 ± 0.47; p = 0.297) and overall image quality (3.92 ± 0.52 vs 3.83 ± 0.54; p = 0.216) were similar at 120 kV and 80 kV., Conclusion: The intraindividual comparison of diagnostic accuracy with normal-dose and simulated low-dose pulmonary CTA protocols revealed no difference under experimental conditions.

Objective: The purpose of this article is to assess the impact of large patient size on the detection of hypovascular liver tumors with MDCT and the effect of a noise filter on image quality and lesion detection in obese patients., Materials and Methods: A liver phantom with 45 hypovascular tumors (diameters of 5, 10, and 15 mm) was placed into two water containers mimicking intermediate and large patients. The containers were scanned with a 64-MDCT scanner. The CT dataset from the large phantom was postprocessed using a noise filter. The image noise was measured and the contrast-to-noise ratio (CNR) of the tumors was calculated. Tumor detection was independently performed by three radiologists in a blinded fashion., Results: The application of the noise filter in the large phantom yielded a reduction of image noise by 42% (p < 0.0001). The CNR values of the tumors in the nonfiltered and filtered large phantom were lower than that in the intermediate phantom (p < 0.05). In the non-filtered and filtered large phantom, 25% and 19% fewer tumors, respectively, were detected on average compared with the intermediate phantom (p < 0.01)., Conclusion: The risk of missing hypovascular liver tumors with CT is substantially increased in large patients. A noise filter improves image quality in obese patients.

Objective: We assessed the diagnostic accuracy and time effectiveness of the Statscan low-dose full-body digital x-ray machine in the evaluation of ventriculoperitoneal (VP) shunt dysfunction., Subjects and Methods: Twenty-five consecutive adults scheduled for a radiographic shunt series with the Statscan were prospectively selected (group 1). Another 21 consecutive patients who underwent conventional x-ray scanning served as controls (group 2) for blinded analysis., Results: Image quality was sufficient for diagnosis in both groups (95.6% vs 95.1%). The quality of VP shunt delineation and contrast of anatomic structures was good or optimal in both groups (p > 0.05). The scan time was significantly lower for group 1 (p < 0.001). All images for group 2 exhibited overlapping of anatomic structures (25% of total coverage), whereas no technically determined overlapping occurred in group 1., Conclusion: The Statscan digital x-ray machine allows accurate assessment of VP shunt continuity at lower radiation dosages and in less time than conventional x-ray techniques.

Objective: The objective of our study was to compare the performance of low-dose linear slit digital radiography (DR) with computed radiography (CR) for the detection of trauma sequelae in the chest including rib fractures, pneumothorax, and lung contusion., Materials and Methods: Eighty trauma victims (62 males, 18 females; mean age, 51.5 years) with a total of 612 rib fractures and 80 consecutive patients without rib fractures (59 males, 21 females; mean age, 39.5 years) were retrospectively analyzed. All patients had undergone whole-body linear slit DR and consecutive chest CT, and 87 patients underwent follow-up CR of the chest within 24 hours of DR and CT. Four blinded readers assessed image quality, rib fracture localization with diagnostic confidence, and the presence of pneumothorax and lung contusion on linear slit DR and CR images. Sensitivity for rib fractures and image quality were compared using the Wilcoxon's test. For the detection of pneumothorax and lung contusion, the difference in the areas under the receiver operating characteristic curves were calculated., Results: The rate of correctly identified rib fractures was higher (true-positive findings per image, 2.55 vs 2.21, respectively; p = 0.02), the rate of missed fractures was lower (false-negative findings per image, 4.98 vs 6.19; p = 0.02), and the diagnostic confidence was greater (2.03 vs 1.73 on a 3-point scale; p = 0.01) with linear slit DR than with CR, respectively. Image quality and performance for detecting pneumothorax and lung contusion with both techniques were not statistically different (p = 0.22, 0.85, and 0.55, respectively)., Conclusion: Linear slit DR is a reliable substitute for CR in the initial evaluation of chest trauma, with better sensitivity for detecting rib fractures and similar performance in assessing pneumothorax and lung contusion.

Objective: In this experimental study we assessed the diagnostic performance of digital linear slit scanning radiography compared with computed radiography (CR) for the detection of urinary calculi in an anthropomorphic phantom imitating patients weighing approximately 58-88 kg., Conclusion: Compared with CR, linear slit scanning radiography is superior for the detection of urinary stones and may be used for pretreatment localization and follow-up at a lower patient exposure.

Objective: The objective of this study was to find the most appropriate, accurate, and convenient muscle parameter that can be used as a substitute for volume in monitoring the effectiveness of therapy of patients with Graves' ophthalmopathy., Subjects and Methods: The four rectus muscles in 110 orbits (35 patients and 20 control subjects) were evaluated with MR imaging. The diameter at the largest extent of the muscle belly, as well as the long and the short diameters and the cross-sectional areas in a preselected coronal scan, were measured for each muscle and were compared with the corresponding muscle volume measured on contiguous T1-weighted transverse slices., Results: The measured coronal area correlated well with the volume of the superior (r = 0.694, p < 0.0001) and inferior (r = 0.783, p < 0.0001) recti, and the largest transverse diameter showed strong correlation with the volume of the lateral (r = 0.868, p < 0.0001) and medial (r = 0.869, p < 0.0001) recti. For the latter muscle, the coronal area also exhibited a good correlation with the volume (r = 0.838, p < 0.0001). Coronal cross-sectional areas can be well estimated by measuring both the short and long coronal muscle diameters (r values were between 0.914 and 0.966; p < 0.0001)., Conclusion: In Graves' ophthalmopathy, the volume of three of the rectus muscles can be well estimated by simple measurements on a single coronal slice, and the largest transverse diameter of the lateral rectus is suitable for the same purpose.