[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.

Submillisievert Computed Tomography of the Chest Using Model-Based Iterative Algorithm: Optimization of Tube Voltage With Regard to Patient Size.

OBJECTIVE: The aim of this study was to define optimal tube potential for soft tissue and vessel visualization in dose-reduced chest CT protocols using model-based iterative algorithm in average and overweight patients. METHODS: Thirty-six patients receiving chest CT according to 3 protocols (120 kVp/noise index [NI], 60; 100 kVp/NI, 65; 80 kVp/NI, 70) were included in this prospective study, approved by the ethics committee. Patients' physical parameters and dose descriptors were recorded. Images were reconstructed with model-based algorithm. Two radiologists evaluated image quality and lesion conspicuity; the protocols were intraindividually compared with preceding control CT reconstructed with statistical algorithm (120 kVp/NI, 20). Mean and standard deviation of attenuation of the muscle and fat tissues and signal-to-noise ratio of the aorta were measured. RESULTS: Diagnostic images (lesion conspicuity, 95%-100%) were acquired in average and overweight patients at 1.34, 1.02, and 1.08 mGy and at 3.41, 3.20, and 2.88 mGy at 120, 100, and 80 kVp, respectively. Data are given as CT dose index volume values. CONCLUSIONS: Model-based algorithm allows for submillisievert chest CT in average patients; the use of 100 kVp is recommended.

Endoleak and in-stent thrombus detection with CT angiography in a thoracic aortic aneurysm phantom at different tube energies using filtered back projection and iterative algorithms.

PURPOSE: To determine the lower limit of dose reduction with hybrid and fully iterative reconstruction algorithms in detection of endoleaks and in-stent thrombus of thoracic aorta with computed tomographic (CT) angiography by applying protocols with different tube energies and automated tube current modulation. MATERIALS AND METHODS: The calcification insert of an anthropomorphic cardiac phantom was replaced with an aortic aneurysm model containing a stent, simulated endoleaks, and an intraluminal thrombus. CT was performed at tube energies of 120, 100, and 80 kVp with incrementally increasing noise indexes (NIs) of 16, 25, 34, 43, 52, 61, and 70 and a 2.5-mm section thickness. NI directly controls radiation exposure; a higher NI allows for greater image noise and decreases radiation. Images were reconstructed with filtered back projection (FBP) and hybrid and fully iterative algorithms. Five radiologists independently analyzed lesion conspicuity to assess sensitivity and specificity. Mean attenuation (in Hounsfield units) and standard deviation were measured in the aorta to calculate signal-to-noise ratio (SNR). Attenuation and SNR of different protocols and algorithms were analyzed with analysis of variance or Welch test depending on data distribution. RESULTS: Both sensitivity and specificity were 100% for simulated lesions on images with 2.5-mm section thickness and an NI of 25 (3.45 mGy), 34 (1.83 mGy), or 43 (1.16 mGy) at 120 kVp; an NI of 34 (1.98 mGy), 43 (1.23 mGy), or 61 (0.61 mGy) at 100 kVp; and an NI of 43 (1.46 mGy) or 70 (0.54 mGy) at 80 kVp. SNR values showed similar results. With the fully iterative algorithm, mean attenuation of the aorta decreased significantly in reduced-dose protocols in comparison with control protocols at 100 kVp (311 HU at 16 NI vs 290 HU at 70 NI, P ≤ .0011) and 80 kVp (400 HU at 16 NI vs 369 HU at 70 NI, P ≤ .0007). CONCLUSION: Endoleaks and in-stent thrombus of thoracic aorta were detectable to 1.46 mGy (80 kVp) with FBP, 1.23 mGy (100 kVp) with the hybrid algorithm, and 0.54 mGy (80 kVp) with the fully iterative algorithm.

Emergency CT head and neck imaging: effects of swimmer's position on dose and image quality.

OBJECTIVES: To compare the effects of different arm positions on dose exposure and image quality (IQ) in cervical spine CT after trauma in different patient groups. METHODS: Patients in standard (STD = 126) and in swimmer's position (SWIM = 254) were included. Body mass index (BMI subgroup 1 = underweight to subgroup 4 = obese), anterior-posterior diameter (AP), left-right diameter (LR), area of an ellipse (AoE) and angle between the humeral heads (optimal STD < 3°, optimal SWIM > 10°) were used as grouping criteria. Computed tomography dose index (CTDI) was documented. Two radiologists rated the IQ at three levels (CV1/2, CV4/5, CV7/T1) using a semi-quantitative scale (0 = not diagnostic, 1 = diagnostic with limitations, 2 = diagnostic without limitations). The Mann-Whitney U test correlations of grouping criteria with dose effects and intra-class correlation (ICC) were calculated. RESULTS: ICC was 0.87. BMI grouping showed the strongest correlation with dose effects: CTDI of optimal STD versus optimal SWIM positioning was 3.17 mGy versus 2.46 mGy (subgroup 1), 5.47 mGy versus 3.97 mGy (subgroup 2), 7.35 mGy versus 5.96 mGy (subgroup 3) and 8.71 mGy versus 8.18 mGy (subgroup 4). Mean IQ at CV7/T1 was 1.65 versus 1.23 (subgroup 1), 1.27 versus 1.46 (subgroup 2), 1.06 versus 1.46 (subgroup 3), 0.79 versus 1.5 (subgroup 4). CONCLUSION: Patients with a BMI > 20 kg/m(2) benefited from both potential dose reduction and improved image quality at the critical cervicothoracic junction when swimmer's position was used. KEY POINTS: • BMI is a useful metric for personalized optimization in CT for the c-spine. • Using swimmer's position, patients can benefit from dose reduction. • In some patients a superior image quality can be achieved with swimmer's position. • For swimmer's positioning an angle of more than 10° is optimal.

Polytrauma: optimal imaging and evaluation algorithm.

Traumatic injuries are the leading cause of death in adults < 45 years of age. Musculoskeletal trauma accounts for a substantial number of injuries in patients sustaining polytrauma. The diagnostic work-up of those patients is challenging, complex, and requires a structured and interdisciplinary workflow. Multidetector CT (MDCT) is considered the imaging modality of choice due to remarkable technical developments in recent years. Besides the evaluation of cranial, chest, and abdominal injuries, MDCT allows for integrated imaging of musculoskeletal trauma within a single CT examination. In this context, CT angiography facilitates the detection of coexisting vascular injuries after trauma of the skeleton. In addition, recent technologies (e.g., dual-energy CT) provide promising applications such as metal artifact reduction. This article summarizes the basic principles of interdisciplinary management of polytrauma patients, reviews recent advances of CT technology that have enabled comprehensive trauma imaging, provides appropriate scan protocols, and discusses the radiologic evaluation of musculoskeletal findings.

CT Marker in Emergency Imaging of Acute Basilar Artery Occlusion: Thrombosis vs. Embolism.

Purpose: Acute basilar artery occlusion, a neurovascular emergency leading to high rates of morbidity and mortality, is usually diagnosed by CT imaging. The outcome is partly dependent on etiology, with a worse outcome in occlusions with underlying basilar artery stenosis. As this occlusion type requires a more complex angiographic therapy, this study aimed to develop new CT markers in emergency admission imaging to rapidly identify underlying stenosis. Methods: A total of 213 consecutive patients (female n = 91, age in years (mean/SD/range): 72/13/28−97), who received endovascular treatment at a single comprehensive stroke center for acute basilar artery occlusion, were included in this study. After applying strict inclusion criteria for imaging analyses, novel CT imaging markers, such as 'absolute density loss' (ADL) and relative thrombus attenuation (CTA-index), that measure perviousness, were assessed for n = 109 patients by use of CT-angiography and correlated to different occlusion patterns (thrombotic vs. embolic). Inter-observer agreement was assessed using an intraclass correlation coefficient for independent measures of a radiologist and a neuroradiologist. Associations between the imaging markers and clinical and interventional parameters were tested. Results: CT markers differ between the subgroups of basilar artery occlusions with and without underlying stenosis (for ADL: 169 vs. 227 HU (p = 0.03), for CTA-index: 0.55 vs. 0.70 (p < 0.001)), indicating a higher perviousness in the case of stenosis. A good inter-rater agreement was observed for ADL and CTA-index measures (ICC 0.92/0.88). For the case of embolic occlusions, a more pervious thrombus correlates to shorter time intervals, longer procedure times, and worse reperfusion success (p-values < 0.05, respectively). Conclusions: ADL and CTA-index are easy to assess in the emergency setting of acute basilar artery occlusion with the use of routinely acquired CT-angiography. They show a high potential to differentiate thrombotic from embolic occlusions, with an impact on therapeutic decisions and angiographic procedures. Measurements can be quickly performed with good reliability, facilitating implementation in clinical practice.

Dose reduction in mammography by using imaging plate technology: A retrospective analysis.

PURPOSE: Conventional mammography is a decisive tool in detecting breast cancer. Continuous efforts are undertaken in order to further improve the image quality as well as to reduce the applied doses. The purpose of our study was to compare diagnostic image quality of dose reduced computed mammography with a new needle-based detector system to full dose powder imaging plates. METHODS: We retrospectively compared 360 randomly chosen mammographies performed on a GE Senographe DMR running the Agfa DX-M needle-based imaging plate system (NIP) with their preliminary examinations which were acquired at standard dose with the same GE mammography device and an Agfa CR85-X powdered storage phosphor imaging plate system (PIP). NIP-based mammographies were about 29.8 % dose-reduced. The preliminary examinations had to be performed not earlier than 2 years before the recent investigations. Exclusion criteria were changes in ACR level and appearance of the scored targets and not optimally positioned and exposed mammographies. The images were blinded and read separately twice by 2 mammography experts according to a 3-point score on diagnostic image quality and the visualization of parenchyma, cysts, fibroadenomas, physiologic lymph nodes, solitary microcalcifications and macrocalcifications. RESULTS: Dose reduced NIPs showed a significantly better visualization of parenchyma at ACR II/III and solitary microcalcifications at ACR I-III mammographies (p < 0.001) whereas the difference in scoring macrocalcifications, cysts, fibroadenomas and physiologic lymph nodes was not significant. The reading showed an excellent intra- (r = 0.97/0.94) and interobserver agreement (r = 0.92). CONCLUSION: With computed mammography using the needle-based detector system a significant dose reduction is possible without loss of diagnostic image quality.

Dose reduction in 64-row whole-body CT in multiple trauma: an optimized CT protocol with iterative image reconstruction on a gemstone-based scintillator.

OBJECTIVE: Evaluation of potential dose savings by implementing adaptive statistical iterative reconstruction (ASiR) on a gemstone-based scintillator in a clinical 64-row whole-body CT (WBCT) protocol after multiple trauma. METHODS: Dose reports of 152 WBCT scans were analysed for two 64-row multidetector CT scanners (Scanners A and B); the main scanning parameters were kept constant. ASiR and a gemstone-based scintillator were used in Scanner B, and the noise index was adjusted (head: 5.2 vs 6.0; thorax/abdomen: 29.0 vs 46.0). The scan length, CT dose index (CTDI) and dose-length product (DLP) were analysed. The estimated mean effective dose was calculated using normalized conversion factors. Student's t-test was used for statistics. RESULTS: Both the mean CTDI (mGy) (Scanner A: 53.8 ± 2.0, 10.3 ± 2.5, 14.4 ± 3.7; Scanner B: 48.7 ± 2.2, 7.1 ± 2.3, 9.1 ± 3.6; p < 0.001, respectively) and the mean DLP (mGy cm) (Scanner A: 1318.9 ± 167.8, 509.3 ± 134.7, 848.8 ± 254.0; Scanner B: 1190.6 ± 172.6, 354.6 ± 128.3, 561.0 ± 246.7; p < 0.001, respectively) for the head, thorax and abdomen were significantly reduced with Scanner B. There was no relevant difference in scan length. The total mean effective dose (mSv) was significantly decreased with Scanner B (24.4 ± 6.0, 17.2 ± 5.8; p < 0.001). CONCLUSION: The implementation of ASiR and a gemstone-based scintillator allows for significant dose savings in a clinical WBCT protocol. ADVANCES IN KNOWLEDGE: Recent technical developments can significantly reduce radiation dose of WBCT in multiple trauma. Dose reductions of 10-34% can be achieved.

Radiological mass casualty incident (MCI) workflow analysis: single-centre data of a mid-scale exercise.

OBJECTIVE: The aim of the study was to analyse and interpret radiological mass casualty incident workflow data. METHODS: In a mid-scale mass casualty incident exercise, the on-site triage assigned 12 cases to the investigated institution (11 included in the study). Two out of five institutional multislice-CT-scanners were used and the whole CT workflow and radiological service process chain were simulated as close to realistic as possible. The respective time intervals for reaching defined milestones were measured. RESULTS: The average CT in-room time, i.e. from entering to leaving the CT room was 9.43 min [(standard deviation) SD: 2.27 min; 95% (confidence interval) CI: 7.90-10.95 min]. Time spent on CT table was 6.75 min (SD: 1.67; CI: 5.63-7.87), and the pure scan time was 4.22 min (SD: 0.64; CI: 3.79-4.65). The first images after entering the CT room were available at a dedicated CT workstation after 5.85 min (SD: 2.20; CI: 4.37-7.32) and institution wide via picture archiving system (PACS) after 7.85 min (SD: 1.27; CI: 7.00-8.71). However, the PACS archiving process, that is, transfer of standard reconstruction set of CT images into the PACS was finished after 20.85 min (SD: 2.97; CI: 18.85-22.84). CONCLUSION: Up to six patients may be served per hour and per CT scanner by using a standard whole body CT polytrauma protocol. Dedicated CT triage protocols may even increase this number. The time portion until images were available at end points was relatively long. A solution has to be developed in order to avoid scenarios of patients being faster at end points than their images.

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.