[Quality of findings, interpretation, and self-assessment of readers of chest x-rays acquired in one plane depending on the use of an anatomical viewing scheme and reader expertise]. / Qualität von Befunderstellung, Beurteilung und Selbsteinschätzung bei der Auswertung von Radiographien des Thorax in einer Ebene in Abhängigkeit von der Verwendung eines anatomischen Betrachtungsschemas und der Auswerterexpertise.

PURPOSE: To objectify effects of an anatomical viewing scheme on the respective correctness of (a) findings, (b) interpretations, and (c) self-assessments of readers in chest radiographs acquired in one plane and the assessment of other influencing factors. MATERIALS AND METHODS: In all, 20 radiologists with 3-60 months of full-time radiography experience evaluated 12 chest radiographs of varying difficulty: once with and once without using an anatomical viewing scheme with at least 1 month in between (n = 480). In consensus of 3 radiological experts (a) and (b) were determined by means of a current computed tomography. The self-assessment (c) of readers was queried. RESULTS: (a) Findings were either missed or not described in 21%. Another 20% were recognized, but incorrectly described, (b) 62% of interpretations and 31% of derived clinical consequences were wrong and (c) in 39% of items the readers overestimated themselves. Experts were faster and better than novices, but for the scheme usage no further significant differences were detected (p > 0.5, respectively). The most pronounced effect was found in comparison with the routine report produced by the joint evaluation of novices and experts being clearly superior even to the expert study results (a), (b) and (c) alone (p < 0.001, respectively). CONCLUSION: Reporting of chest X­rays acquired in one plane was often incomplete or even wrong, and the evaluators overestimated themselves, which was not influenced by the use of the anatomical viewing scheme. Since errors between the evaluators sometimes differed greatly, duplicate evaluation of the radiographs by two different radiologists, which is already the case in many training facilities, may possibly be advisable in general.

Detection of pulmonary embolism with free-breathing dynamic contrast-enhanced MRI.

PURPOSE: To evaluate the use of dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) during free breathing for the detection of acute pulmonary embolism (PE). MATERIALS AND METHODS: Eighteen subjects underwent free-breathing DCE MRI at 1.5T, eight of whom were patients with acute PE, as confirmed by routine computed tomography pulmonary angiography (CTPA). The remaining 10 subjects were healthy volunteers with no history or signs of pulmonary disease. From all DCE MRI data, maps of relative signal enhancement were calculated and assessed for the presence or absence of perfusion defects in each lung by two readers. Interreader variability, sensitivity, and specificity of free-breathing DCE MRI for the detection of PE were calculated using CTPA as the gold standard. RESULTS: Of the 16 patient's lungs, 15 were affected by acute PE according to CTPA. In patients and volunteers, DCE MRI sensitivity was 93% and 87% for readers 1 and 2, with specificities of 95% and 90%, respectively. Interreader agreement was substantial, with κ = 0.77 (95% confidence interval: 0.44-1.0). CONCLUSION: Free-breathing DCE MRI may have potential use for the assessment of PE, and does not require patient cooperation in breath-holding.

Reduction of CT beam hardening artefacts of ethylene vinyl alcohol copolymer by variation of the tantalum content: evaluation in a standardized aortic endoleak phantom.

OBJECTIVES: Our aim was to develop an aortic stent graft phantom to simulate endoleak treatment and to find a tantalum content (TC) of ethylene-vinyl-alcohol-copolymer that causes fewer computed tomography (CT) beam hardening artefacts, but still allows for fluoroscopic visualization. METHODS: Ethylene-vinyl-alcohol-copolymer specimens of different TC (10-50 %, and 100 %) were injected in an aortic phantom bearing a stent graft and endoleak cavities with simulated re-perfusion. Fluoroscopic visibility of the ethylene-vinyl-alcohol-copolymer specimens was analyzed. In addition, six radiologists analyzed endoleak visibility, and artefact intensity of ethylene-vinyl-alcohol-copolymer in CT. RESULTS: Reduction of TC significantly decreased CT artefact intensity of ethylene-vinyl-alcohol-copolymer and increased visibility of endoleak re-perfusion (p < 0.000). It also significantly decreased fluoroscopic visibility of ethylene-vinyl-alcohol-copolymer (R = 0.883, p ≤ 0.01), and increased the active embolic volumes prior to visualization (Δ ≥ 40 µl). Ethylene-vinyl-alcohol-copolymer specimens with a TC of 45-50 % exhibited reasonable visibility, a low active embolic volume and a tolerable CT artefact intensity. CONCLUSIONS: The developed aortic stent graft phantom allows for a reproducible simulation of embolization of endoleaks. The data suggest a reduction of the TC of ethylene-vinyl-alcohol-copolymer to 45 -50 % of the original, to interfere less with diagnostic imaging in follow-up CT examinations, while still allowing for fluoroscopic visualization.

Prospective evaluation of optical coherence tomography in lower limb arteries compared with intravascular ultrasound.

PURPOSE: To compare in a prospective noninferiority study optical coherence tomography (OCT) and intravascular ultrasound (IVUS) in popliteal and infrapopliteal vessels. MATERIALS AND METHODS: OCT and IVUS images of 112 popliteal and infrapopliteal arterial segments were prospectively obtained from 16 patients with peripheral arterial occlusive disease. Three observers evaluated the corresponding OCT and IVUS images for image quality, artifact frequency, discriminability of vessel wall layers, and plaque composition. Measurements of the lumen, vessel, and plaque areas were compared for both modalities. RESULTS: The intrareader and interreader reproducibility of plaque tissue discrimination (0.88 vs 0.75), overall image quality, and vessel wall layer discriminability were significantly higher for OCT (all P < .001). Artifact frequency was higher in OCT, constraining the imaging of the tibioperoneal trunk. The results of measurements of the lumen and vessel area were comparable for both modalities (correlation > 0.9, P < .001). Plaque area measurements differed (correlation 0.8, P < .01) because OCT underestimated it. The OCT procedure caused vessel spasms in two patients. CONCLUSIONS: OCT imaging of infrapopliteal arteries is feasible and safe and provides high image quality. It enables an accurate assessment of vessel lumen, wall, and plaque. Compared with IVUS, OCT images provide excellent image quality and superior visualization of vessel wall layers and different plaque components. The penetration depth of OCT restricts its use to suitable vessel regions.

Value of oxygen-enhanced MRI of the lungs in patients with pulmonary hypertension: a qualitative and quantitative approach.

PURPOSE: To assess the clinical value of oxygen-enhanced magnetic resonance imaging (oeMRI) in patients with pulmonary hypertension (PH) by correlation with ventilation/perfusion (V/Q) scintigraphy. MATERIALS AND METHODS: In all, 33 patients with known PH underwent V/Q scintigraphy and oeMRI. oeMRI was used to assess the regional pulmonary function based on relative-signal-enhancement (RSE) and cross-correlation-coefficient (CCC) maps, evaluating mean RSE (mRSE), fraction of oxygen-activated pixels (fOAP), and mean CCC (mCCC). Two reviewers, blinded to the results of scintigraphy, performed visual detection of diseased lung areas. RESULTS: In 26 of the 33 patients (79%) the image quality of oeMRI reached a diagnostic level. In total, 150 lung areas were analyzed and compared. Sensitivities/specificities of oeMRI for detecting these defects were: RSE vs. ventilation scintigraphy 92%/73%; RSE vs. perfusion scintigraphy 60%/87%; CCC vs. ventilation scintigraphy 89%/81%; CCC vs. perfusion scintigraphy 50%/87%. The number of diseased lung areas in oeMRI correlated significantly with the number in V/Q scintigraphy (P < 0.01). mRSE showed a significant correlation with the number of diseased lung areas in ventilation scintigraphy (P < 0.05). CONCLUSION: oeMRI is feasible in PH patients, yielding an overall moderate agreement between oeMRI and V/Q scans, with a good sensitivity of oeMRI for the detection of ventilation defects as compared with ventilation scintigraphy.

Severity assessment of pulmonary embolism using dual energy CT - correlation of a pulmonary perfusion defect score with clinical and morphological parameters of blood oxygenation and right ventricular failure.

OBJECTIVE: To correlate a Dual Energy (DE)-based visual perfusion defect scoring system with established CT-based and clinical parameters of pulmonary embolism (PE) severity. METHODS: In 63 PE patients, DE perfusion maps were visually scored for perfusion defects (P-score). Vascular obstruction was quantified using the Mastora score. Both scores were correlated with short-axis diameters of the right and left ventricle, their ratio (RV/LV ratio), width of the pulmonary trunk, a number of clinical parameters and each other. Univariate and multivariate analyses were performed. Times to generate both scores were recorded. RESULTS: After univariate and multivariate analysis, a significant (p < 0.05) correlation with the P-score was shown for the Mastora score (r = 0.65), RV/LV ratio (r = 0.47), width of the pulmonary trunk (r = 0.26), troponin I (r = 0.43) and PaO(2) (r = -0.50). For the left ventricular diameter, only univariate analysis showed a significant correlation. Mastora score correlated significantly with RV/LV ratio (r = 0.36), width of the pulmonary trunk (r = 0.27), PaO(2) (r = -0.41) and troponin I (r = 0.37). Mean time for generating the P-score was significantly shorter than for the Mastora score. CONCLUSIONS: A DE-based P-score correlates with a number of parameters of PE severity. It might be easier and faster to perform than some traditional CT scoring methods for vascular obstruction.

Evaluation of the 6-F ExoSeal vascular closure device in antegrade femoral artery punctures.

PURPOSE: To evaluate the safety, comfort, and efficacy of an extravascularly deployed bioabsorbable plug-based vascular closure device (VCD) for sealing 6-F antegrade access sites in patients requiring peripheral endovascular intervention. METHODS: A single-center, single-arm, prospective study to evaluate the 6-F ExoSeal VCD in terms of technical success, adverse events, and patient comfort enrolled 59 unselected symptomatic patients (42 men; mean age 72.1 ± 9.3 years) suffering from peripheral artery disease in an 11-month period. Patients with high body mass index (BMI) or calcification at the access site were not excluded. Calcifications of the access vessel were scored as grades 1-4 from fluoroscopic images. The pain level during implantation was evaluated after the procedure using a visual rating scale. RESULTS: Technical success rate was 98.3%; 1 primary device failure was converted to manual compression. In addition, 1 (1.7%) pseudoaneurysm, 2 (3.4%) minor hematomas, and 1 (1.7%) minor secondary bleeding were observed. There was no intravascular application of the device detected. Neither BMI, calcification of the access vessel (present in 74.6%, mean score 1.4 ± 1.1), age, nor blood clotting had any statistically significant influence on adverse events. In total, 55 (93.2%) patients felt no pain during the VCD implantation. CONCLUSION: The tested VCD was safe, with an excellent technical success rate even in cases with severe access vessel calcification.

Pulmonary ventilation and perfusion imaging with dual-energy CT.

OBJECTIVE: To evaluate the feasibility of dual-energy CT (DECT) ventilation imaging in combination with DE perfusion mapping for a comprehensive assessment of ventilation, perfusion, morphology and structure of the pulmonary parenchyma. METHODS: Two dual-energy CT acquisitions for xenon-enhanced ventilation and iodine-enhanced perfusion mapping were performed in patients under artificial respiration. Parenchymal xenon and iodine distribution were mapped and correlated with structural or vascular abnormalities. RESULTS: In all datasets, image quality was sufficient for a comprehensive image reading of the pulmonary CTA images, lung window images and pulmonary functional parameter maps and led to expedient results in each patient. CONCLUSION: With dual-source CT systems, DECT of the lung with iodine or xenon administration is technically feasible and makes it possible to depict the regional iodine or xenon distribution representing the local perfusion and ventilation.

Intraosseous needles in pediatric cadavers: Rate of malposition.

AIM OF THE STUDY: Intraosseous vascular access is a commonly conducted procedure especially in pediatric resuscitation. Very high success rates for intraosseous (IO) devices are reported. Aim of the study was to describe the rates of malposition of intraosseous needles (ION) in pediatric cadavers via post-mortem computed tomography (PMCT). METHODS: 212 consecutive pediatric cadavers underwent PMCT, of which 38 cadavers had visible ION and were included in the study. They were divided into two subgroups depending on their age (n = 22 infant cadavers (age <1 year) and n = 16 child cadavers (age ≥1 year)). Two independent readers evaluated the number and position of ION. RESULTS: In 22 infant cadavers 34 ION were found. Malposition of at least one ION was visible in 14 subjects (64%), among which 7 cadavers (32%) even had no correctly placed ION, thus being without established vascular access. Overall, 16 of the 34 used ION devices (47%) were in malposition. 23 ION were found in 16 child cadavers. In 8 subjects (50%) at least one ION was malpositioned, among which 3 cadavers (19%) had no correctly placed ION, resulting in a complete absence of vascular access. Overall, 9 of the 23 ION devices (39%) were malpositioned. CONCLUSION: Our study showed relatively high malposition rates for ION devices in pediatric cadavers which was not to be assumed regarding the success rates of 80% and higher in previous literature. This should be clarified by further studies in living patients.

Improvement of Radiological Teaching - Effects of Focusing of Learning Targets and Increased Consideration of Learning Theory Knowledge.

PURPOSE: Based on evaluation and examination results of students, a necessity for improvement of so far purely instructor-based radiological teaching at the local institution was determined. Aim of our study was to use one out of eight seminars to exemplify adaptation of the teaching concept according to learning theory knowledge, to determine the resulting effects and to interpret them. MATERIALS AND METHODS: The institutional review board approved the prospective study of the seminar conversion, which was performed after the end of the winter semester 2015/2016. Didactically, this included a course split into online preparation, attendance phase and online follow-up with integration of interactive scaffolding, practice-oriented clinical teaching according to Stanford, Peyton skills transfer and extensive feedback into the attendance phase. At the beginning and at the end of each course, each student filled in identical, standardized questionnaires (n = 256 before and after conversion) using a 5-point Likert scale (1: very good; to 5: deficient) and additionally answered two randomly chosen written examination questions from a content-adapted questionnaire pool of the last five years. For statistical evaluation, the Mann-Whitney U-Test was used for evaluation data and Fisher's Exact test for exam questions. RESULTS: Before/after conversion, the subjective total evaluation score of students was 3.22 (mean value) ±â€Š1.51 (standard deviation) / 1.66 ±â€Š0.78 (p < 0.001) and the objective proportion of correctly answered examination questions in the respective cohort at the beginning of the seminar 37.7/53.9 % and at the end of the seminar 55.1/84.6 % (p < 0.001). CONCLUSION: The conversion of the test seminar resulted in both a better evaluation of the teaching unit by the students (evaluation) and a considerably higher rate of correctly answered examination questions from past state examinations (learning success). This supports transferring the concept to comparable teaching units. KEY POINTS: · Radiological teaching allows integration of current learning theory concepts with reasonable effort.. · In a test seminar this improved the evaluation results of the teaching unit by the students.. · In addition, this also led to a higher rate of correctly answered examination questions from past state examinations.. · This supports further steps towards excellent radiological teaching.. CITATION FORMAT: · Wirth S, William Y, Paolini M et al. Improvement of Radiological Teaching - Effects of Focusing of Learning Targets and Increased Consideration of Learning Theory Knowledge. Fortschr Röntgenstr 2018; 190: 161 - 174.

How low can we go in contrast-enhanced CT imaging of the chest?: A dose-finding cadaver study using the model-based iterative image reconstruction approach.

RATIONALE AND OBJECTIVES: Dose reduction may compromise patients because of a decrease of image quality. Therefore, the amount of dose savings in new dose-reduction techniques needs to be thoroughly assessed. To avoid repeated studies in one patient, chest computed tomography (CT) scans with different dose levels were performed in corpses comparing model-based iterative reconstruction (MBIR) as a tool to enhance image quality with current standard full-dose imaging. MATERIALS AND METHODS: Twenty-five human cadavers were scanned (CT HD750) after contrast medium injection at different, decreasing dose levels D0-D5 and respectively reconstructed with MBIR. The data at full-dose level, D0, have been additionally reconstructed with standard adaptive statistical iterative reconstruction (ASIR), which represented the full-dose baseline reference (FDBR). Two radiologists independently compared image quality (IQ) in 3-mm multiplanar reformations for soft-tissue evaluation of D0-D5 to FDBR (-2, diagnostically inferior; -1, inferior; 0, equal; +1, superior; and +2, diagnostically superior). For statistical analysis, the intraclass correlation coefficient (ICC) and the Wilcoxon test were used. RESULTS: Mean CT dose index values (mGy) were as follows: D0/FDBR = 10.1 ± 1.7, D1 = 6.2 ± 2.8, D2 = 5.7 ± 2.7, D3 = 3.5 ± 1.9, D4 = 1.8 ± 1.0, and D5 = 0.9 ± 0.5. Mean IQ ratings were as follows: D0 = +1.8 ± 0.2, D1 = +1.5 ± 0.3, D2 = +1.1 ± 0.3, D3 = +0.7 ± 0.5, D4 = +0.1 ± 0.5, and D5 = -1.2 ± 0.5. All values demonstrated a significant difference to baseline (P < .05), except mean IQ for D4 (P = .61). ICC was 0.91. CONCLUSIONS: Compared to ASIR, MBIR allowed for a significant dose reduction of 82% without impairment of IQ. This resulted in a calculated mean effective dose below 1 mSv.

Assessment of pulmonary perfusion with breath-hold and free-breathing dynamic contrast-enhanced magnetic resonance imaging: quantification and reproducibility.

OBJECTIVES: The purpose of this study was to investigate whether quantification of pulmonary perfusion from dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) yields more reproducible results with data acquired during free breathing than with data from conventional breath-hold measurements. MATERIAL AND METHODS: Ten healthy male volunteers underwent 2 imaging sessions at a clinical 1.5-T MRI system, separated by a week±1 day. Each of these sessions comprised 2 DCE MRI acquisitions: one performed during breath-hold and one during free, shallow breathing; both acquisitions were separated by at least 20 minutes. For all DCE MRI measurements, a standard dose of gadobutrol was used. Breath-hold measurements lasted 53 seconds; free-breathing acquisitions were performed in a total acquisition time of 146 seconds.Lung tissue was segmented automatically to minimize user influence, and pulmonary plasma flow (PPF) and volume (PPV) were quantified on a per-pixel basis with a 1-compartment model. Free-breathing measurements were analyzed twice, (a) including data from the entire acquisition duration and (b) after truncation to the duration of the breath-hold measurements. For further statistical analysis, median values of the resulting parameter maps were determined. To assess intraindividual reproducibility, intraclass correlation coefficients and coefficients of variation between the first and second measurements were calculated for breath-hold, truncated, and full free-breathing measurements, respectively. Differences in the coefficients of variation were assessed with a nonparametric 2-sided paired Wilcoxon signed rank test. RESULTS: All 40 measurements were completed successfully. Maps of PPF and PPV could be calculated from both measurement techniques; PPF and PPV in the breath-hold measurements were significantly lower (P < 0.001) than in truncated and full free-breathing measurements. Both evaluations of the free-breathing measurements yielded higher intraclass correlation coefficients and lower coefficients of variation between the first and second measurements than the breath-hold measurements. CONCLUSIONS: Besides offering substantially higher patient comfort, free-breathing DCE MRI acquisitions allow for pixelwise quantification of pulmonary perfusion and hence generation of parameter maps. Moreover, quantitative perfusion estimates derived from free-breathing DCE MRI measurements have better reproducibility than estimates from the conventionally used breath-hold measurements.

Analysis of signal dynamics in oxygen-enhanced magnetic resonance imaging.

OBJECTIVES: Oxygen-enhanced MRI (O2-MRI) is frequently based on a block paradigm consisting of a series of consecutive T1-weighted scans acquired during alternating blocks with inhalation of room air and of pure oxygen. This design results in a complex signal-time course for each pixel, which displays the oxygen wash-in and wash-out processes and provides spatially resolved information about the lung function. The purpose of the present study was to optimize the signal-time-course analysis to extract (pixelwise) the maximum amount of information from the acquired data, and to introduce an appropriate cross-correlation approach for data sets containing the oxygen wash-in and wash-out periods. MATERIALS AND METHODS: O2-MRI data of 11 healthy volunteers were acquired with a multislice inversion-recovery single-shot turbo-spin-echo sequence at 1.5 Tesla; lung and spleen were manually segmented on all 44 acquired slices. Six different model functions were pixelwise fitted to the data and compared using the Akaike information criterion. Four different reference functions were compared for cross-correlation analysis. RESULTS: The optimal model function is a piecewise exponential function (median enhancement in lung/spleen: 16.3%/14.8%) with different time constants for wash-in (29.4 seconds/72.7 seconds) and wash-out (25.1 seconds/29.6 seconds). As a new parameter, it contains the delay between switching the gas supply and the onset of the signal change (4.8 seconds/24.5 seconds). Optimal cross-correlation results were obtained with a piecewise exponential reference function, which was temporally shifted to maximize the correlation, yielding median correlation coefficients of 0.694 and 0.878, median time delays of 7.5 seconds and 38.6 seconds, and median fractions of oxygen-activated pixels of 83.6% and 92.2% in the lung and the spleen, respectively. CONCLUSIONS: It was demonstrated that the pixelwise assessment of O2-MRI data are optimally performed with piecewise exponential functions. Cross-correlation analysis with a piecewise exponential reference function results in significantly higher fractions of oxygen-activated pixels than with rectangular functions.