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Objectives: The aim was to measure the effective dose of flat-detector CT (FDCT) whole-brain imaging, biphasic FDCT angiography (FDCT-A), and FDCT perfusion (FDCT-P) protocols and compare it to previously reported effective dose values of multidetector CT (MDCT) applications., Materials: We measured effective dose according to the IRCP 103 using an anthropomorphic phantom equipped with thermoluminescent dosimeters (TLDs). Placement was according to anatomical positions of each organ. In total, 60 TLDs (≥ 4 TLDs/organ) were placed into and onto the phantom to account for all relevant organs. Organs within the primary beam were covered with more TLDs. Additionally, we measured dose to the eye lens with two TLDs per eye. Protocols which we routinely use in clinical practice were measured on a biplane angiography system., Results: The effective dose of the 20-s protocol/7-s protocol for whole-brain imaging was 2.6 mSv/2.4 mSv. The radiation dose to the eye lens was 24/23 mGy. For the biphasic high-/low-dose FDCT-A protocol, the effective dose was 8.9/2.8 mSv respectively. The eye lens dose was 60/14 mGy. The contribution of bolus tracking to the effective dose was 0.66 mSv (assuming average duration of 14 s). The multisweep FDCT-P protocol had an effective dose of 5.9 mSv and an eye lens dose of 46 mGy., Conclusion: Except for the high-dose biphasic FDCT-A protocol, FDCT applications used in neuroradiology have effective doses, which do not deviate more than 1 mSv from previously reported values for MDCT applications. However, the effective dose to the eye lens in commonly used stroke paradigms exceeds the recommended annual dose twofold., Key Points: • Flat-detector computed tomography (FDCT) can be used for acute and periinterventional imaging of acute stroke patients and in neurointerventions. • Except for the high-dose FDCT angiography protocol, the effective doses do not deviate more than 1 mSv from previously reported values for multidetector CT applications. • Strategies to decrease the effective lens dose especially in younger patients should be evaluated in the future.

Aim: The purpose of our study was to compare the agreement of both the total Alberta Stroke Program Early CT Score (ASPECTS) and region-based scores from two automated ASPECTS software packages and an expert consensus (EC) reading with final ASPECTS in a selected cohort of patients who had prompt reperfusion from endovascular thrombectomy (EVT)., Methods: ASPECTS were retrospectively and blindly assessed by two software packages and EC on baseline non-contrast-enhanced computed tomography (NCCT) images. All patients had multimodal CT imaging including NCCT, CT angiography, and CT perfusion which demonstrated an acute anterior circulation ischemic stroke with a large vessel occlusion. Final ASPECTS on follow-up scans in patients who had EVT and achieved complete reperfusion within 100 min from NCCT served as ground truth and were compared to total and region-based scores., Results: Fifty-two patients met our study criteria. Moderate agreement was obtained between both software packages and EC for total ASPECTS and there was no significant difference in overall performance. However, the software packages differed with respect to regional contribution. In this cohort, the majority of infarcted regions were deep structures. Package A was more sensitive in cortical areas than the other methods, but at a cost of specificity. EC and software package B had greater sensitivity, but lower specificity for deep brain structures., Conclusion: In this cohort, using the final ASPECTS as ground truth, no clinically significant difference was observed for total ASPECT score between human or automated packages, but there were differences in the characteristics of the regions scored., Key Points: • Some national stroke guidelines have incorporated ASPECTS in their recommendations for selecting patients for endovascular therapy. • Computer-aided diagnosis is a promising tool to aid the evaluation of early ischemic changes identified on CT. • Software packages for automated ASPECTS assessment differed significantly with respect to regional contribution without any significant difference in the overall ASPECT score.

Purpose: Invasive aspergillosis usually affects immunocompromised patients. It carries a high risk of morbidity and mortality and usually has a nonspecific clinical presentation. Early diagnosis is essential in order to start effective treatment and improve clinical outcome., Materials and Methods: In a retrospective search of the PACS databases from two medical centers, we identified 9 patients with histologically proven cerebral aspergilloma. We systematically analyzed CT and MRI imaging findings to identify typical imaging appearances of cerebral aspergilloma., Results: CT did not show a typical appearance of the aspergillomas. In 100 % (9/9) there was a rim-attenuated diffusion restriction on MRI imaging. Multiple hypointense layers in the aspergillus wall, especially on the internal side, were detected in 100 % on T2-weighted imaging (9/9). Aspergillomas were T1-hypointense in 66 % of cases (6/9) and partly T1-hyperintense in 33 % (3/9). In 78 % (7/9) of cases, a rim-attenuated diffusion restriction was detected after contrast agent application., Conclusion: Nine cases were identified. Whereas CT features were less typical, we observed the following imaging features on MRI: A strong, rim-attenuated diffusion restriction (9/9); onion layer-like hypointense zones, in particular in the innermost part of the abscess wall on T2-weighted images (9/9). Enhancement of the lesion border was present in the majority of the cases (7/9)., Key Points: · There are typical MRI imaging features of aspergillomas.. · However, these findings could be affected by the immune status of the patient.. · Swift identification of aspergilloma imaging patterns is essential to allow for adequate therapeutic decision making.., Citation Format: · Gärtner F, Forstenpointner J, Ertl-Wagner B et al. CT and MRI Findings in Cerebral Aspergilloma. Fortschr Röntgenstr 2018; 190: 967 - 970., Competing Interests: Disclosure The authors report no conflicts of interest in this work., (© Georg Thieme Verlag KG Stuttgart · New York.)

Background: Hyperdense arteries in cranial CT of acute stroke patients have been described as a sign for acute ischemia in various brain-feeding arteries. However, only 1 case of a hyperdense anterior cerebral artery sign (HACAS) has been published to date. In this study, the frequency and association of HACAS with clinical symptoms and outcome are described., Methods: Our radiological databases were searched for patients with infarcts in the territory of the anterior cerebral artery (ACA). Only patients who received an initial CT and a follow-up CT or MRI were included. The presence of a HACAS was rated by 2 independent observers using the Cohen kappa-statistics. Further data recorded were early ischemic signs, final size of infarct, symptoms, initial NIHSS (National Institute of Health Stroke Scale) score, latency between symptom onset and initial CT, etiology, modified Rankin Scale (mRS) score at discharge and secondary hemorrhage., Results: A HACAS could be visualized in 11/24 patients (46%). Interobserver agreement was substantial with Cohen's kappa = 0.66. Patients with a HACAS had a significantly higher NIHSS score (9.45 +/- 8.41; median: 8) than those without (3.69 +/- 2.09; median: 4). A HACAS was visible more frequently when the CT was performed early (<2.5 h after symptom onset). There was no correlation with single symptoms, size of infarct, etiology, mRS or the tendency to hemorrhage., Conclusions: HACAS is associated with a higher NIHSS score. It is an early sign of ischemia which can be reversible over time. It can be helpful in the detection of ischemia in the territory of the ACA.

The purpose of this study was to investigate the precision of CT-based volumetric measurements of artificial small pulmonary nodules under ex vivo conditions. We implanted 322 artificial nodules in 23 inflated ex vivo porcine lungs in a dedicated chest phantom. The lungs were examined with a multislice spiral CT (20 mAs, collimation 16x0.75 mm, 1 mm slice thickness, 0.7 mm increment). A commercial volumetry software package (LungCARE VA70C-W; Siemens, Erlangen, Germany) was used for volume analysis in a semi-automatic and a manual corrected mode. After imaging, the lungs were dissected to harvest the nodules for gold standard determination. The volumes of 202 solitary, solid and well-defined lesions without contact with the pleura, greater bronchi or vessels were compared with the results of volumetry. A mean nodule diameter of 8.3 mm (+/-2.1 mm) was achieved. The mean relative deviation from the true lesion volume was -9.2% (+/-10.6%) for semi-automatic and -0.3% (+/-6.5%) for manual corrected volumetry. The subgroup of lesions from 5 mm to <10 mm in diameter showed a mean relative deviation of -8.7% (+/-10.9%) for semi-automatic volumetry and -0.3% (+/-6.9%) for manually corrected volumetry. We conclude that the presented software allowed for precise volumetry of artificial nodules in ex vivo lung tissue. This result is comparable to the findings of previous in vitro studies.

Purpose: The aim of this in vitro and ex vivo CT study was to investigate whether the use of a routine thorax protocol (RTP) with optimized reconstruction parameters can provide comparable accuracy, reproducibility and interobserver variability of volumetric analyses to that of a special volumetry protocol (SVP)., Materials and Methods: To assess accuracy, 3 polyurethane (PU) spheres (35 HU; diameters: 4, 6 and 10 mm) were examined with a recommended SVP using a multislice CT (collimation 16 x 0.75 mm, pitch 1.25, 20 mAs, slice thickness 1 mm, increment 0.7 mm, medium kernel) and an optimized RTP (collimation 16 x 1.5 mm, pitch 1.25, 100 mAs, reconstructed slice thickness 2 mm, increment 0.4 mm, sharp kernel). For the assessment of intrascan and interscan reproducibility and interobserver variability, 20 artificial small pulmonary nodules were placed in a dedicated ex vivo chest phantom and examined with identical scan protocols. The artificial lesions consisted of a fat-wax-Lipiodol mixture. Phantoms and ex vivo lesions were examined afterwards using commercial volumetry software. To describe accuracy the relative deviations from the true volumes of the PU phantoms were calculated. For intrascan and interscan reproducibility and interobserver variability, the 95 % normal range (95 % NR) of relative deviations between two measurements was calculated., Results: For the SVP the achieved relative deviations for the 4, 6 and 10 mm PU phantoms were - 14.3 %, - 12.7 % and - 6.8 % and were 4.5 %, - 0.6 % and - 2.6 %, respectively, for the optimized RTP. SVP showed a 95 % NR of 0 - 1.5 % for intrascan and a 95 % NR of - 10.8 - 2.9 % for interscan reproducibility. The 95 % NR for interobserver variability was - 4.3 - 3.3 %. The optimized RTP achieved a 95 % NR of - 3.1 - 4.3 % for intrascan reproducibility and a 95 % NR of - 7.0 - 3.5 % for interscan reproducibility. The 95 % NR for interobserver variability was - 0.4 - 6.8 %., Conclusion: For datasets achieved with an SVP and an optimized RTP, this experimental approach showed comparable accuracy, reproducibility, and interobserver variability to allow for sufficient volumetric analysis of pulmonary lesions.

Objective: The main purpose of this study was to investigate the reproducibility of computed tomography (CT)-based volumetric measurements of small pulmonary nodules., Methods: We implanted 70 artificial pulmonary nodules in 5 ex vivo porcine lungs in a dedicated chest phantom. The lungs were scanned 5 times consecutively with multislice-CT (collimation 16 x 0.75 mm, slice thickness 1 mm, reconstruction increment 0.7 mm). A commercial software package was used for lesion volumetry. The authors differentiated between intrascan reproducibility, interscan reproducibility, and results from semiautomatic and postprocessed volumetry., Results: Analysis of intrascan reproducibility revealed a mean variation coefficient of 6.2% for semiautomatic volumetry and of 0.7% for human adapted volumetry. For interscan reproducibility a mean variation coefficient of 9.2% and for human adapted volumetry a mean of 3.7% was detected., Conclusion: The presented volumetry software showed a high reproducibility that can be expected to detect nodule growth with a high degree of certainty.

Purpose: To develop a method for generating realistic pulmonary nodules that equal small pulmonary metastases and granulomas., Materials and Methods: A total of 70 artificial lesions were introduced into 5 inflated porcine lungs inside a dedicated chest phantom by high pressure injection of a fat-wax-Lipiodol mixture and scanned with 16-slice computed tomography (CT). Image evaluation by two experienced radiologists included analysis of morphology, nodule size and density., Results: The median nodule density was 78.8 Hounsfield units (HU), with 54 of 70 nodules (77.14 %) judged typical of small lung metastases., Conclusion: Without inducing visible damage of lung parenchyma, the injection technique produces highly realistic pulmonary nodules for morphometry or nodule detection with CT.