Publications by authors named "Andrea Steuwe"

9 Publications

  • Page 1 of 1

Impact of increasing levels of adaptive statistical iterative reconstruction on image quality in oil-based postmortem CT angiography in coronary arteries.

Int J Legal Med 2021 Feb 24. Epub 2021 Feb 24.

Medical Faculty, Department of Diagnostic and Interventional Radiology, University Dusseldorf, D-40225, Dusseldorf, Germany.

Introduction: Postmortem multi-detector computed tomography (PMCT) has become an important part in forensic imaging. Modern reconstruction techniques such as iterative reconstruction (IR) are frequently used in postmortem CT angiography (PMCTA). The image quality of PMCTA depends on the strength of IR. For this purpose, we aimed to investigate the impact of different advanced IR levels on the objective and subjective PMCTA image quality.

Material And Methods: We retrospectively analyzed the coronary arteries of 27 human cadavers undergoing whole-body postmortem CT angiography between July 2017 and March 2018 in a single center. Iterative reconstructions of the coronary arteries were processed in five different level settings (0%; 30%; 50%; 70%; 100%) by using an adaptive statistical IR method. We evaluated the objective (contrast-to-noise ratio (CNR)) and subjective image quality in several anatomical locations.

Results: Our results demonstrate that the increasing levels of an IR technique have relevant impact on the image quality in PMCTA scans in forensic postmortem examinations. Higher levels of IR have led to a significant reduction of image noise and therefore to a significant improvement of objective image quality (+ 70%). However, subjective image quality is inferior at higher levels of IR due to plasticized image appearance.

Conclusion: Objective image quality in PMCTA progressively improves with increasing level of IR with the best CNR at the highest IR level. However, subjective image quality is best at low to medium levels of IR. To obtain a "classic" image appearance with optimal image quality, PMCTAs should be reconstructed at medium levels of IR.
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February 2021

Effective dose of radiation per screw in surgery of adolescent idiopathic scoliosis: matched pair analysis of 293 pedicle screws inserted using three different techniques.

J Child Orthop 2020 Dec;14(6):554-561

Department of Orthopedic Surgery, University Hospital of Duesseldorf, Duesseldorf, Germany.

Purpose: Reports on heterogenous groups of patients have indicated that pedicle screw insertion guided by navigation (PIN) leads to, for the patient, higher doses of radiation compared with pedicle screw insertion guided by fluoroscopy (PIF). This would be a major concern, especially in paediatric deformity correction.

Methods: After a power analysis (aiming at > 0.8) 293 pedicle screws which were inserted in patients with adolescent idiopathic scoliosis were analyzed by comparing effective dose and fluoroscopy time per screw for three different techniques. Groups 2 and 3 were matched to Group 1 by Lenke type of scoliosis. Group 1 were prospectively enrolled consecutive patients that have been operated on by PIN with image acquisition by preoperative CT scan (CTS). Group 2 were consecutive retrospectively matched patients who have been operated on by PIN with image acquisition by an intraoperative 3D scan (3DS). Group 3 were consecutive retrospectively matched patients who have been operated on by PIF.

Results: Mean dose of radiation per screw was 1.0 mSv (sd 0.8) per screw in CTS patients, 0.025 mSv (sd 0.001) per screw in 3DS patients and 0.781 mSv (sd 0.12) per screw in PIF patients. The difference was significant (p < 0.0001).

Conclusion: When we compared different techniques of navigation, navigation by image acquisition with CTS showed a significantly higher (by 97.5%) dose of radiation per screw for the patient than navigation by image acquisition by a 3DS. Navigation by 3DS showed significantly lower effective dose per screw for the adolescent patients than the fluoroscopic technique.

Level Of Evidence: II.
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December 2020

Update: Selective adrenal venous sampling (AVS) - Indication, technique, and significance.

Rofo 2020 Dec 16. Epub 2020 Dec 16.

University Dusseldorf, Medical Faculty, Department of Diagnostic and Interventional Radiology, Dusseldorf, Germany.

Background:  Primary aldosteronism (PA) is the most common detectable cause of secondary hypertension. The majority of patients have either an adrenal aldosterone-producing adenoma (APA) or bilateral adrenal hyperplasia (BAH) demanding different therapeutic approaches. Screening tests and imaging cannot reliably distinguish between a unilateral or bilateral PA.

Methods:  This review article gives an overview concerning etiology, diagnostics, and therapeutic options of PA, and reviews the indication, the technique, and relevance of selective adrenal venous sampling (AVS) in the context of the current literature and the authors' experience.

Results:  AVS can verify or exclude a unilaterally dominated secretion with a high success rate. Patients with PA and a unilateral APA can be treated curatively by adrenalectomy.

Conclusions:  AVS is an established diagnostic examination for differentiation of unilateral from bilateral adrenal disease in patients with PA.

Key Points: · Selective adrenal venous sampling (AVS) is a safe, reliable, and minimally invasive method to detect a unilateral or bilateral adrenal adrenal gland disease.. · Verification of lateralization by AVS has direct therapeutic relevance for patients with primary aldosteronism (PA).. · AVS can be performed with low radiation exposure, without contrast medium, and with a high success rate when performed by an experienced interventional radiologist..

Citation Format: · Loberg C, Antoch G, Stegbauer J et al. Update: Selective adrenal venous sampling (AVS) - Indication, technique, and significance. Fortschr Röntgenstr 2020; DOI: 10.1055/a-1299-1878.
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December 2020

Influence of a novel deep-learning based reconstruction software on the objective and subjective image quality in low-dose abdominal computed tomography.

Br J Radiol 2021 Jan 23;94(1117):20200677. Epub 2020 Oct 23.

Department of Diagnostic and Interventional Radiology, University Dusseldorf, Medical Faculty, Dusseldorf, Germany.

Objectives: Modern reconstruction and post-processing software aims at reducing image noise in CT images, potentially allowing for a reduction of the employed radiation exposure. This study aimed at assessing the influence of a novel deep-learning based software on the subjective and objective image quality compared to two traditional methods [filtered back-projection (FBP), iterative reconstruction (IR)].

Methods: In this institutional review board-approved retrospective study, abdominal low-dose CT images of 27 patients (mean age 38 ± 12 years, volumetric CT dose index 2.9 ± 1.8 mGy) were reconstructed with IR, FBP and, furthermore, post-processed using a novel software. For the three reconstructions, qualitative and quantitative image quality was evaluated by means of CT numbers, noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) in six different ROIs. Additionally, the reconstructions were compared using SNR, peak SNR, root mean square error and mean absolute error to assess structural differences.

Results: On average, CT numbers varied within 1 Hounsfield unit (HU) for the three assessed methods in the assessed ROIs. In soft tissue, image noise was up to 42% lower compared to FBP and up to 27% lower to IR when applying the novel software. Consequently, SNR and CNR were highest with the novel software. For both IR and the novel software, subjective image quality was equal but higher than the image quality of FBP-images.

Conclusion: The assessed software reduces image noise while maintaining image information, even in comparison to IR, allowing for a potential dose reduction of approximately 20% in abdominal CT imaging.

Advances In Knowledge: The assessed software reduces image noise by up to 27% compared to IR and 48% compared to FBP while maintaining the image information.The reduced image noise allows for a potential dose reduction of approximately 20% in abdominal imaging.
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January 2021

Dose-optimised chest computed tomography for diagnosis of Coronavirus Disease 2019 (COVID-19) - Evaluation of image quality and diagnostic impact.

J Radiol Prot 2020 09;40(3):877-891

Medical Faculty, Department of Diagnostic and Interventional Radiology, University Hospital Düsseldorf, Düsseldorf D-40225, Germany.

Objectives: The detection of Coronavirus Disease 2019 (COVID-19) by reverse transcription polymerase chain reaction (RT-PCR) has varying sensitivity. Computed tomography (CT) of the chest can verify infection in patients with clinical symptoms and a negative test result, accelerating treatment and actions to prevent further contagion. However, CT employs ionising radiation. The purpose of this study was to evaluate protocol settings, associated radiation exposure, image quality and diagnostic performance of a low-dose CT protocol in a university hospital setting.

Materials And Methods: Chest CT examinations were performed on a single scanner (Somatom Definition Edge, Siemens Healthineers, Germany) in 105 symptomatic patients (60 male, 45 female). Images were evaluated with regard to protocol parameters, image quality, radiation exposure and diagnostic accuracy. Serial RT-PCR served as the standard of reference. Based on this reference standard sensitivity, specificity, positive and negative predictive values of CT with 95% confidence interval were calculated.

Results: The mean effective dose was 1.3 ± 0.4 mSv (0.7-2.9 mSv) for the patient cohort (mean age 66.6 ± 16.7 years (19-94 years), mean body mass index (BMI) 26.6 ± 5.3 kg m (16-46 kg/m)). A sensitivity of 100 [95% CI: 82-100]%, a specificity of 78 [95% CI: 68-86]%, a positive predictive value of 50 [95% CI: 33-67]% and a negative predictive value of 100 [95% CI: 95-100]% were obtained. No COVID-19 diagnoses were missed by CT. Image noise did not strongly correlate with BMI or patient diameter and was rated as average.

Conclusions: We presented a robust imaging procedure with a chest CT protocol for confident diagnosis of COVID-19. Even for an overweight patient cohort, an associated radiation exposure of only 1.3 ± 0.4 mSv was achieved with sufficient diagnostic quality to exclude COVID-19.
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September 2020

Diagnostic value and forensic relevance of a novel photorealistic 3D reconstruction technique in post-mortem CT.

Br J Radiol 2020 Aug 18;93(1112):20200204. Epub 2020 Jun 18.

Department of Diagnostic and Interventional Radiology, University Dusseldorf, Medical Faculty, D-40225, Dusseldorf, Germany.

Objectives: Evaluation of performance and forensic relevance of a novel, photorealistic, 3D reconstruction method (cinematic rendering, (CR)) in comparison with conventional post-mortem CT (PMCT) and volume rendering (VR) technique for visualization of traumatic injuries.

Methods: 112 pathologies (fractures, soft tissue injuries and foreign bodies) from 33 human cadavers undergoing whole body PMCT after traumatic death were retrospectively analyzed. Pathologies were reconstructed with CR and VR techniques. Fractures were classified according to their dislocation. Images were evaluated according to their expressiveness and judicial relevance by two forensic pathologists using a five-level Likert-scale (1: high expressiveness, 5: low expressiveness). They decided whether CR reconstructions were suitable for judicial reviews. The detection rate of pathologies was determined by two radiologists.

Results: CR was more expressive than VR for all three trauma categories ( < 0.01) and than conventional CT when used for fractures with dislocation ( < 0.001), injuries of the ventral body surface ( < 0.001), and demonstration of foreign bodies ( = 0.033). CR and VR became more expressive with a higher grade of fracture dislocation ( < 0.001). 20% of all pathologies in the CR and VR reconstructions were not detectable by radiologists.

Conclusion: CR reconstructions are superior to VR regarding the expressiveness. For fractures with substantial dislocation, soft tissue injuries, and foreign bodies , CR showed a significantly better expressiveness than conventional PMCT. CR and VR have significant limitations in cases of fractures with minor dislocations and covered soft tissue injuries.

Advances In Knowledge: CR is a helpful tool to present pathologies found in PMCT for judicial reviews.
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August 2020

Development of size-specific institutional diagnostic reference levels for computed tomography protocols in neck imaging.

J Radiol Prot 2020 Mar 11;40(1):68-82. Epub 2019 Oct 11.

University Düsseldorf, Medical Faculty, Department of Diagnostic and Interventional Radiology, D-40225 Düsseldorf, Germany.

Purpose: To develop size-specific institutional diagnostic reference levels (DRLs) for computed tomography (CT) protocols used in neck CT imaging (cervical spine CT, cervical CT angiography (CTA) and cervical staging CT) and to compare institutional to national DRLs.

Materials And Methods: Cervical CT examinations (spine, n = 609; CTA, n = 505 and staging CT, n = 184) performed between 01/2016 and 06/2017 were included in this retrospective study. For each region and examination, the volumetric CT dose index (CTDI) and dose-length product (DLP) were determined and binned into size bins according to patient water-equivalent diameter (d). Linear regression analysis was performed to calculate size-specific institutional DRLs for CTDI and DLP, applying the 75th percentile as the upper limit for institutional DRLs. The mean institutional CTDI and DLP were compared to national DRLs (CTDI 20 mGy for cervical spine CT (DLP 300 mGycm) and cervical CTA (DLP 600 mGycm), and CTDI 15 mGy for cervical staging CT (DLP 330 mGycm)).

Results: The mean CTDI and DLP (±standard deviation) were 15.2 ± 4.1 mGy and 181.5 ± 88.3 mGycm for cervical spine CT; 8.1 ± 4.3 mGy and 280.2 ± 164.3 mGycm for cervical CTA; 8.6 ± 1.9 mGy and 162.8 ± 85.0 mGycm for cervical staging CT. For all CT protocols, there was a linear increase in CTDI and DLP with increasing d. For the CTDI, size-specific institutional DRLs increased with d from 14 to 29 mGy for cervical spine CT, from 5 to 17 mGy for cervical CTA and from 8 to 13 mGy for cervical staging CT. For the DLP, size-specific institutional DRLs increased with d from 130 to 510 mGycm for cervical spine CT, from 140 to 640 mGycm for cervical CTA and from 140 to 320 mGycm for cervical staging CT. Institutional DRLs were lower than national DRLs by 81% and 67% for cervical spine CT (d = 17.8 cm), 43% and 51% for cervical CTA (d = 19.5 cm) and 59% and 53% for cervical staging CT (d = 18.8 cm) for CTDI and DLP, respectively.

Conclusion: Size-specific institutional DRLs were generated for neck CT examinations. The mean institutional CTDI and DLP values were well below national DRLs.
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March 2020

Comparison of Radiation Exposure Associated With Intraoperative Cone-Beam Computed Tomography and Follow-up Multidetector Computed Tomography Angiography for Evaluating Endovascular Aneurysm Repairs.

J Endovasc Ther 2016 Aug 18;23(4):583-92. Epub 2016 May 18.

Clinic of Diagnostic and Interventional Radiology, University Hospital Heidelberg, Germany

Purpose: To compare the radiation exposure associated with intraoperative contrast-enhanced cone-beam computed tomography (ceCBCT) acquisitions to standard 3-phase multidetector computed tomography (MDCT) angiography used for assessing technical success after endovascular aortic repair (EVAR).

Methods: Effective doses (EDs) were calculated for 66 EVAR patients (mean age 71 years; 61 men) with a mean 27.7-kg/m(2) body mass index (range 17-49) who had both intraoperative ceCBCT and postoperative 3-phase MDCT angiography between November 2012 and April 2015. In addition, EDs were directly determined using thermoluminescent dosimeters (TLDs) embedded in anthropomorphic phantoms with body mass indexes of 22 and 30 kg/m(2) Effective doses were calculated by summing doses recorded by all TLDs corresponding to a specific tissue type before applying the International Commission on Radiological Protection (ICRP) 60 and 103 weighting factors. EDs were compared with each other for both imaging modalities as well as to TLD measurements.

Results: Average EDs of the patient collective were 4.9±1.1 mSv for ceCBCT, 2.6±1.2 mSv for single-phase MDCT (46% decrease, covering solely the area of the implanted endograft), and 13.6±5.5 mSv for comprehensive 3-phase MDCT examinations (178% increase, anatomical coverage from the aortic arch to femoral artery bifurcation). EDs determined in phantom measurements ranged from 3.1 to 4.5 mSv for ceCBCT, amounting to 2.6 mSv for a single MDCT phase (15% to 40% decrease) using ICRP 60 conversion factors. Applying ICRP 103 factors resulted in higher values for ceCBCT and slightly lower ones for MDCT.

Conclusion: ceCBCT offers the chance for immediate intraoperative revisions of endograft-related problems. Requiring only a single-phase acquisition, ceCBCT is associated with a considerable reduction in ED (50%-75%) compared to standard 3-phase MDCT angiography after EVAR. On the other hand, MDCT has a larger field of view and is associated with less radiation exposure for a single phase (reduction of 20%-60%) if only the stented region is covered; however, MDCT angiography also uses larger amounts of contrast.
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August 2016

A role for 11C-methionine PET imaging in ACTH-dependent Cushing's syndrome.

Eur J Endocrinol 2015 Oct 5;173(4):M107-20. Epub 2015 Aug 5.

Metabolic Research Laboratories Wellcome Trust-MRC Institute of Metabolic Science Departments of Nuclear Medicine Medical Physics Otolaryngology Oncology Neuroradiology Neurosurgery National Institute for Health Research, Cambridge Biomedical Research Centre, University of Cambridge & Addenbrooke's Hospital, Box 289, Hills Road, Cambridge CB2 0QQ, UK

Objective: We report our experience of functional imaging with (11)C-methionine positron emission tomography-computed tomography (PET-CT) co-registered with 3D gradient echo (spoiled gradient recalled (SPGR)) magnetic resonance imaging (MRI) in the investigation of ACTH-dependent Cushing's syndrome.

Design: Twenty patients with i) de novo Cushing's disease (CD, n=10), ii) residual or recurrent hypercortisolism following first pituitary surgery (±radiotherapy; n=8) or iii) ectopic Cushing's syndrome (n=2) were referred to our centre for functional imaging studies between 2010 and 2015. Six of the patients with de novo CD and five of those with persistent/relapsed disease had a suspected abnormality on conventional MRI.

Methods: All patients underwent (11)C-methionine PET-CT. For pituitary imaging, co-registration of PET-CT images with contemporaneous SPGR MRI (1 mm slice thickness) was performed, followed by detailed mapping of (11)C-methionine uptake across the sella in three planes (coronal, sagittal and axial). This allowed us to determine whether suspected adenomas seen on structural imaging exhibited focal tracer uptake on functional imaging.

Results: In seven of ten patients with de novo CD, asymmetric (11)C-methionine uptake was observed within the sella, which co-localized with the suspected site of a corticotroph microadenoma visualised on SPGR MRI (and which was subsequently confirmed histologically following successful transsphenoidal surgery (TSS)). Focal (11)C-methionine uptake that correlated with a suspected abnormality on pituitary MRI was seen in five of eight patients with residual or recurrent Cushing's syndrome following first TSS (and pituitary radiotherapy in two cases). Two patients elected to undergo repeat TSS with histology confirming a corticotroph tumour in each case. In two patients with the ectopic ACTH syndrome, (11)C-methionine was concentrated in sites of distant metastases, with minimal uptake in the sellar region.

Conclusions: (11)C-methionine PET-CT can aid the detection of ACTH-secreting tumours in Cushing's syndrome and facilitate targeted therapy.
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October 2015