The objective of this study is to identify essential aspects influencing radiation dose in computed tomography [CT] of the chest, abdomen and pelvis by intraindividual comparison of imaging parameters and patient related factors. All patients receiving at least two consecutive CT examinations for tumor staging or follow-up within a period of 22 months were included in this retrospective study. Different CT dose estimates (computed tomography dose index [CTDI_vol], dose length product [DLP], size-specific dose estimate [SSDE]) were correlated with patient’s body mass index [BMI], scan length and technical parameters (tube current, tube voltage, pitch, noise level, level of iterative reconstruction). Repeated-measures-analysis was initiated with focus on response variables (CTDI_vol, DLP, SSDE) and possible factors (age, BMI, noise, scan length, peak kilovoltage [kVp], tube current, pitch, adaptive statistical iterative reconstruction [ASIR]). A univariate-linear-mixed-model with repeated-measures-analysis followed by Bonferroni adjustments was used to find associations between CT imaging parameters, BMI and dose estimates followed by a subsequent multivariate-mixed-model with repeated-measures-analysis with Bonferroni adjustments for significant parameters. A p-value <0.05 was considered statistically significant. We found all dose estimates in all imaging regions were substantially affected by tube current. The iterative reconstruction significantly influenced all dose estimates in the thoracoabdominopelvic scans as well as DLP and SSDE in chest-CT. Pitch factor affected all dose parameters in the thoracoabdominopelvic CT group. These results provide further evidence that tube current has a pivotal role and potential in radiation dose management. The use of iterative reconstruction algorithms can substantially decrease radiation dose especially in thoracoabdominopelvic and chest-CT-scans. Pitch factor should be kept at a level of ≥1.0 in order to reduce radiation dose.

Purpose To assess digital patient briefing as an alternative to conventional paper documentation. Materials and Methods 502 patients with a planned computed tomography (CT) examination were selected for digital patient briefing using the E-ConsentPro software from Thieme Compliance on an iPad by Apple (Cupertino, California, USA). For the analysis, three age groups were formed. The time required for the patient briefing, the number of open questions as well as the time needed for discussion with physicians were determined. Student’s t-test was performed to assess statistical significance. Results There was no significant difference between patient age and briefing time which was about 20 minutes on average. The number of open or unclear questions increased with patient age. While patients younger than 30 years of age had about 2 open questions, patients over 30 and 60 years had about 4 and 5 questions, respectively. The total time needed for discussion with physicians was less than 2 minutes on average. A significant difference in the time required for discussion with physicians could not be observed between the individual age groups. Conclusion Tablet-based digital briefing allows the storage of patient documents with reasonable time and effort. Furthermore, it minimizes the risk of data loss. Key Points Citation Format

To evaluate the image quality (IQ) of advanced modeled iterative reconstruction (ADMIRE; Siemens Healthcare, Forchheim, Germany) applying image texture and image visual impression as a supplement to physical parameters such as noise level and spatial resolution. An ACR-phantom with four modules was examined at different radiation dose levels. To characterise the image texture, two Haralick texture parameters, contrast and entropy, were assessed at different dose levels and reconstruction algorithms. The visual impression of images and the low-contrast detectability were evaluated by the structural similarity index (SSIM). The spatial resolution was determined by the modulation transfer functions and the line spread function. The Haralick texture parameters, contrast and entropy, decreased with increasing ADMIRE levels. ADMIRE III, IV and V offered a comparable contrast and entropy to those calculated by filtered back projection (FBP) with a radiation dose reduction up to 50%. SSIM (low-contrast detectability) improved with increasing ADMIRE levels. SSIM calculated by ADMIRE IV and V revealed comparable IQ to FBP with a decreased CTDI_vol up to 50%. Spatial resolution was retained up to 90% dose reduction. Compared to FBP at the same dose level, the image noise decreased up to 61% with higher ADMIRE levels (σ _FBP = 17.3 HU and σ _{ADMIRE V} = 10.6 HU at 6.65 mGy). Taking texture analysis and visual perception into account, a more realistic assessment of the dose reduction potential of ADMIRE can be achieved than quality metrics based alone on physical measurements.

Purpose To evaluate the influence of patient alignment and thereby heel effect on the image quality (IQ) of C-arm flat-panel detector computed tomography (CACT). Materials and Methods An ACR phantom placed in opposite directions along the z-axis (setup A and B) on the patient support was imaged using CACT. Image acquisition was performed with three different image acquisition protocols. The images were reconstructed with four convolution kernels. IQ was assessed in terms of high contrast using the modulation transfer function (MTF) and low contrast by assessing the image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratios (CNR) as well as the reliability of density measurements. Furthermore, the dose intensity profiles were measured free-in-air. Results The MTF in setup B is higher than the MTF measured in setup A (p < 0.01). The image noises measured in setup A for the air and bone inserts were higher compared to those measured in setup B (p > 0.05). Opposite behavior has been observed for the polyethylene, water-equivalent and acrylic inserts. The SNR for all inserts is inversely related to the image noise. A systematically increasing or decreasing trend of CNR could not be observed (p > 0.05). The intensity profile measured by the detector system free-in-air showed that the anode heel effect is perpendicular to the z-axis. Conclusion The patient alignment has a minor influence on the IQ of CACT. This effect is not based on the X-ray anode heel effect but is caused mainly by the non-symmetrical rotation of CACT. Key Points: Citation Format Ziel Der Einfluss der Patientenausrichtung und des Heel-Effekts auf die Bildqualität einer C-Bogen-Flachbilddetektor-Durchleuchtungseinheit (CACT) wurde untersucht. Material und Methoden Ein ACR-Phantom wurde in entgegengesetzten Richtungen entlang der z-Achse auf dem Patiententisch platziert (Setup A und B). Die Messungen wurden an einem CACT mit neuartigen Flachdetektoren durchgeführt. Die Bilddaten wurden mit 3 verschiedenen Untersuchungsprotokollen und 4 Faltungskernen rekonstruiert. Die Hochkontrastauflösung mithilfe der Modulationsübertragungsfunktion (MTF) und die Niederkontrastsauflösung unter Verwendung des Bildrauschens, des Signal-Rausch-Verhältnisses (SNR) und des Kontrast-Rausch-Verhältnisses (CNR) wurden bestimmt. Außerdem wurden die Dosisintensitätsprofile „frei in Luft“ gemessen. Ergebnisse MTF in Setup B ist höher als in Setup A (p < 0,01). Das Rauschen in Setup A für die Luft- und Knocheneinsätze war höher als in Set-up B (p > 0,05). Ein umgekehrter Verlauf wurde für die Einsätze aus Polyethylen, Wasseräquivalent und Acryl beobachtet. SNR für alle Einsätze ist umgekehrt proportional zum Bildrauschen. Ein systematisch ansteigender oder abnehmender Trend von CNR konnte nicht beobachtet werden (p > 0,05). Das vom Detektorsystem gemessene Intensitätsprofil „frei in Luft“ zeigte, dass der Heel-Effekt senkrecht zur z-Achse und nicht parallel dazu verläuft. Schlussfolgerung Die Patientenausrichtung hat einen geringen Einfluss auf die Bildqualität von CACT. Dieser Effekt beruht nicht auf dem Hell-Effekt, sondern durch die asymmetrische Rotation des CACT-Arms. Kernaussagen: Received: 13 September 2019 Accepted: 03 August 2020 Publication Date: 03 September 2020 (online) © Georg Thieme Verlag KG Stuttgart · New York