Publications by authors named "Joel Aissa"

33 Publications

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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http://dx.doi.org/10.1007/s00414-021-02530-1DOI Listing
February 2021

Is the prediction of one or two ipsilateral positive lymph nodes by computerized tomography and ultrasound reliable enough to restrict therapeutic neck dissection in oral squamous cell carcinoma (OSCC) patients?

J Cancer Res Clin Oncol 2021 Feb 1. Epub 2021 Feb 1.

Department of Oral and Maxillofacial Surgery, Medical Faculty, University Hospital of the Heinrich-Heine-University, Düsseldorf, Germany.

Introduction: Proper management of the clinically involved neck in OSCC patients continues to be a matter of debate. Our aim was to analyze the accuracy of computerized tomography (CT) and ultrasound (US) in anticipating the exact location of lymph node (LN) metastases of OSCC patients across the AAO-HNS (American Academy of Otolaryngology-Head and Neck Surgery) levels ipsi- and contralaterally. Furthermore, we wanted to assess the suitability of therapeutic selective neck dissection (SND) in patients with one or two ipsilateral positive nodes upon clinical staging (cN1/cN2a and cN2b(2/x) patients).

Methods: We prospectively analyzed the LN status of patients with primary OSCC using CT and US from 2007 to 2013. LNs were individually assigned to a map containing the AAO-HNS levels; patients bearing a single or just two ipsilateral positive nodes (designated cN1/cN2a or cN2b(2/x) patients either by CT (CT group) or US alone (US group) or in a group combining findings of CT and US (CTUS group)) received an ipsi-ND (I-V) and a contra-ND (I-IV). 78% of the LNs were sent individually for routine histopathological examination; the remaining were dissected and analyzed per neck level.

Results: Upon the analysis of 1.670 LNs of 57 patients, the exact location of pathology proven LN metastases in cN1 patients was more precisely predicted by US compared to CT with confirmed findings only in levels IA, IB und IIA. Clearly decreasing the number of missed lesions, the findings in the CTUS group nearly kept the spatial reliability of the US group. The same analysis for patients with exactly two supposed ipsilateral lesions (cN2b(2/x)) yielded confirmed metastases from levels I to V for both methods individually and in combination and, therefore, render SND insufficient for these cases.

Conclusion: Our findings stress the importance of conducting both, CT and US, in patients with primary OSCC. Only the combination of their findings warrants the application of therapeutic SND in patients with a single ipsilateral LN metastasis (cN1/cN2a patients) but not in patients with more than one lesion upon clinical staging (≥ cN2b).
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http://dx.doi.org/10.1007/s00432-021-03523-8DOI Listing
February 2021

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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http://dx.doi.org/10.1259/bjr.20200677DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7774679PMC
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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http://dx.doi.org/10.1088/1361-6498/aba16aDOI Listing
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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http://dx.doi.org/10.1259/bjr.20200204DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7446014PMC
August 2020

Impact of different iterative metal artifact reduction (iMAR) algorithms on PET/CT attenuation correction after port implementation.

Eur J Radiol 2020 Aug 15;129:109065. Epub 2020 May 15.

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

Purpose: To evaluate the effect of various interactive metal artifact reduction (iMAR) algorithms on attenuation correction in the vicinity of port chambers in PET/CT.

Material And Methods: In this prospective study, 30 oncological patients (12 female, 18 male, mean age 59.6 ± 10.5y) with implanted port chambers undergoing 18F-FDG PET/CT were included. CT images were reconstructed with standard weighted filtered back projection (WFBP) and three different iMAR algorithms (hip, dental filling (DF) and pacemaker (PM)). PET attenuation correction was performed with all four CT datasets. SUVmean, SUVmax and HU measurements were performed in fat and muscle tissue in the vicinity of the port chamber at the location of the strongest bright and dark band artifacts. Differences between HU and SUV values across all CT- and PET-images were investigated using a paired t-test. Bonferroni correction was used to prevent alpha-error accumulation (p < 0.008).

Results: In comparison to WFBP (fat: 94.2 ± 53.9 HU, muscle: 197.6 ± 49.2 HU) all three iMAR algorithms led to a decrease of HU in bright band artifacts. iMAR-DF led to a decrease of 159.2 % (fat: -51.9 ± 58.5 HU, muscle: 94.5 ± 55.3 HU), iMAR-hip of 138.3 % (fat: -30.3 ± 58.5, muscle: 70.4 ± 28.8) and iMAR-PM of 122.3 % (fat: -21.2 ± 47.2 HU, muscle: 72.5 ± 25.1 HU; for all p < 0.008). There was no significant effect of iMAR on SUV measurements in comparison to WFBP.

Conclusion: iMAR leads to a significant change of HU values in artifacts caused by port catheter chambers in comparison to WFBP. However, no significant differences in attenuation correction and consecutive changes in SUV measurements can be observed.
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http://dx.doi.org/10.1016/j.ejrad.2020.109065DOI Listing
August 2020

Impact of different metal artifact reduction techniques on attenuation correction in 18F-FDG PET/CT examinations.

Br J Radiol 2020 Jan 1;93(1105):20190069. Epub 2019 Nov 1.

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

Objective: To evaluate the impact of different metal artifact reduction (MAR) algorithms on Hounsfield unit (HU) and standardized uptake values (SUV) in a phantom setting and verify these results in patients with metallic implants undergoing oncological PET/CT examinations.

Methods And Materials: In this prospective study, PET-CT examinations of 28 oncological patients (14 female, 14 male, mean age 69.5 ± 15.2y) with 38 different metal implants were included. CT datasets were reconstructed using standard weighted filtered back projection (WFBP) without MAR, MAR in image space (MARIS) and iterative MAR (iMAR, hip algorithm). The three datasets were used for PET attenuation correction. SUV and HU measurements were performed at the site of the most prominent bright and dark band artifacts. Differences between HU and SUV values across the different reconstructions were compared using paired t-tests. Bonferroni correction was used to prevent alpha-error accumulation ( < 0.017).

Results: For bright band artifacts, MARIS led to a non-significant mean decrease of 12.0% (345 ± 315 HU) in comparison with WFBP (391 ± 293 HU), whereas iMAR led to a significant decrease of 68.3% (125 ± 185 HU, < 0.017). For SUVmean, MARIS showed no significant effect in comparison with WFBP (WFBP: 0.99 ± 0.40, MARIS: 0.96 ± 0.39), while iMAR led to a significant decrease of 11.1% (0.88 ± 0.35, < 0.017). Similar results were observed for dark band artifacts.

Conclusion: iMAR significantly reduces artifacts caused by metal implants in CT and thus leads to a significant change of SUV measurements in bright and dark band artifacts compared with WFBP and MARIS, thus probably improving PET quantification.

Advances In Knowledge: The present work indicates that MAR algorithms such as iMAR algorithm in integrated PET/CT scanners are useful to improve CT image quality as well as PET quantification in the evaluation of tracer uptake adjacent to large metal implants. A detailed analysis of oncological patients with various large metal implants using different MAR algorithms in PET/CT has not been conducted yet.
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http://dx.doi.org/10.1259/bjr.20190069DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6948077PMC
January 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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http://dx.doi.org/10.1088/1361-6498/ab4d00DOI Listing
March 2020

Implementation of Institutional Size-Specific Diagnostic Reference Levels for CT Angiography.

Acad Radiol 2019 12 22;26(12):1661-1667. Epub 2019 Feb 22.

University Duesseldorf, Department of Diagnostic and Interventional Radiology, Moorenstraße 5, 40225 Duesseldorf, Germany.

Rationale And Objectives: To generate institutional size-specific diagnostic reference levels (DRLs) for computed tomography angiography (CTA) examinations and assess the potential for dose optimization compared to size-independent DRLs.

Materials And Methods: CTA examinations of the aorta, the pulmonary arteries and of the pelvis/lower extremity performed between January 2016 and January 2017 were included in our retrospective study. Water equivalent diameter (Dw) was automatically calculated for each patient. The relationship between Dw and computed tomography dose index (CTDI) was analyzed and the 75th percentile was chosen as the upper limit for institutional DRLs. Size-specific institutional DRLs were compared to national size-independent DRLs from Germany and the UK.

Results: A total of 1344 examinations were included in our study (n = 733 aortic CTA, n = 406 pulmonary CTA, n = 205 pelvic/lower extremity CTA). Mean Dw was 26 ± 9 cm and mean CTDI was 7.0 ± 4.6 mGy. For all CTA protocols, there was a linear progression of CTDI with increasing Dw with an R² = 0.95 in aortic CTA, R² = 0.94 in pulmonary CTA and R² = 0.93 in pelvic/lower extremity CTA. Median CTDI increased by 0.57 mGy per additional cm Dw in aortic CTA, by 1.1 mGy in pulmonary CTA and by 0.31 mGy in pelvic/lower extremity CTA. Institutional DRLs were lower than national DRLs for average size patients (aortic CTA: Dw 28.2 cm, CTDI 7.6 mGy; pulmonary CTA, Dw 27.9 cm, CTDI 11.8 mGy; pelvic/lower extremity CTA, Dw 20.0 cm, CTDI 6.4 mGy). More dose outliers in small patients were detected with size-specific DRLs compared to national size-independent DRLs (56.4% vs 16.2%).

Conclusion: We implemented institutional size-specific DRLs for CTA examinations which enabled a more precise analysis compared to national sizeindependent DRLs.
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http://dx.doi.org/10.1016/j.acra.2019.01.019DOI Listing
December 2019

Noise insertion in CT for cocaine body packing: where is the limit of extensive dose reduction?

Eur J Med Res 2018 Dec 7;23(1):59. Epub 2018 Dec 7.

Department of Diagnostic and Interventional Radiology, Medical Faculty, University Dusseldorf, Moorenstr. 5, 40225, Dusseldorf, Germany.

Background: To evaluate the detection rate and image quality in CT-body-packer-screening at different radiation-dose levels and to determine a dose threshold that enables a reliable detection of incorporated body packs and incidental findings with a maximum of dose saving.

Materials And Methods: We retrospectively included 27 individuals who underwent an abdominal CT with automated exposure control due to suspected body packing. CT images were reconstructed at different radiation-dose levels of 50%, 10, 5% and 1% using iterative reconstructions. All 135 CT reconstructions were evaluated by three independent readers. Reviewers determined the presence of foreign bodies and evaluated the image quality using a 5-point ranking scale. In addition, visualization of incidental findings was assessed.

Results: A threshold of 5% (effective dose 0.11 ± 0.07 mSv) was necessary to correctly identify all 27 patients with suspected body packing. Extensive noise insertion to a dose level of 1% (0.02 ± 0.01 mSV) led to false-positive solid cocaine findings in three patients. Image quality was comparable between 100 and 50%. The threshold for correct identification of incidental findings was 10% of the initial dose (effective dose 0.21 ± 0.13 mSv).

Conclusions: Our results indicate that dose of abdominal CT for the detection of intracorporeal cocaine body packets can be markedly reduced to up to 5% of the initial dose while still providing sufficient image quality to detect ingested body packets. However, a minimum effective dose of 0.21 mSv (10% of initial dose) seems to be required to properly identify incidental findings.
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http://dx.doi.org/10.1186/s40001-018-0356-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6284291PMC
December 2018

Performance and clinical impact of machine learning based lung nodule detection using vessel suppression in melanoma patients.

Clin Imaging 2018 Nov - Dec;52:328-333. Epub 2018 Sep 11.

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

Purpose: To evaluate performance and the clinical impact of a novel machine learning based vessel-suppressing computer-aided detection (CAD) software in chest computed tomography (CT) of patients with malignant melanoma.

Materials And Methods: We retrospectively included consecutive malignant melanoma patients with a chest CT between 01/2015 and 01/2016. Machine learning based CAD software was used to reconstruct additional vessel-suppressed axial images. Three radiologists independently reviewed a maximum of 15 lung nodules per patient. Vessel-suppressed reconstructions were reviewed independently and results were compared. Follow-up CT examinations and clinical follow-up were used to assess the outcome. Impact of additional nodules on clinical management was assessed.

Results: In 46 patients, vessel-suppressed axial images led to the detection of additional nodules in 25/46 (54.3%) patients. CT or clinical follow up was available in 25/25 (100%) patients with additionally detected nodules. 2/25 (8%) of these patients developed new pulmonary metastases. None of the additionally detected nodules were found to be metastases. None of the lung nodules detected by the radiologists was missed by the CAD software. The mean diameter of the 92 additional nodules was 1.5 ± 0.8 mm. The additional nodules did not affect therapeutic management. However, in 14/46 (30.4%) of patients the additional nodules might have had an impact on the radiological follow-up recommendations.

Conclusion: Machine learning based vessel suppression led to the detection of significantly more lung nodules in melanoma patients. Radiological follow-up recommendations were altered in 30% of the patients. However, all lung nodules turned out to be non-malignant on follow-up.
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http://dx.doi.org/10.1016/j.clinimag.2018.09.001DOI Listing
January 2019

Age-related apparent diffusion coefficients of lumbar vertebrae in healthy children at 1.5 T.

Pediatr Radiol 2018 07 13;48(7):1008-1012. Epub 2018 Apr 13.

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

Background: Diffusion-weighted magnetic resonance imaging with apparent diffusion coefficient (ADC) calculation is important for detecting bone marrow pathologies.

Objective: To investigate age-related differences of lumbar vertebral body ADC to establish normal values for healthy children.

Materials And Methods: Forty-nine healthy children without any history of oncological or hematological diseases (10.2±4.7 years, range: 0-20 years) were included in this retrospective study. All magnetic resonance imaging (MRI) examinations were performed at 1.5 T and with similar scan parameters. The diffusion-weighted sequences were performed with b values of 50, 400 and 800 s/mm. ADC values were measured by placing regions of interest at three different levels within each lumbar vertebral body (L1 to L5). ADC values were analyzed for different age groups (0-2 years, 3-6 years, 7-11 years, 12-14 years, 15-20 years), for each vertebral and intravertebral level.

Results: The mean ADC of the whole study group was 0.60±0.09 × 10 mm/s. Children between the ages of 12 and 14 years had significantly higher ADC compared to the other age groups (P≤0.0003). ADC values were significantly higher in the 1st lumbar vertebral body compared to the other levels of the lumbar spine (P<0.005) with the exception of L5, and in the upper third of the vertebral bodies compared to the middle or lower thirds (P≤0.003).

Conclusion: The age-, vertebral- and intravertebral level-dependent differences in ADC suggest a varying composition and cellularity in different age groups and in different locations.
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http://dx.doi.org/10.1007/s00247-018-4119-7DOI Listing
July 2018

Tailoring CT Dose to Patient Size: Implementation of the Updated 2017 ACR Size-specific Diagnostic Reference Levels.

Acad Radiol 2018 12 23;25(12):1624-1631. Epub 2018 Mar 23.

University Dusseldorf, Medical Faculty, Department of Diagnostic and Interventional Radiology, Moorenstraße 5, 40225 Dusseldorf, Germany.

Rationale And Objectives: To use an automatic computed tomography (CT) dose monitoring system to analyze the institutional chest and abdominopelvic CT dose data as regards the updated 2017 American College of Radiology (ACR) diagnostic reference levels (DRLs) based on water-equivalent diameter (Dw) and size-specific dose estimates (SSDE) to detect patient-size subgroups in which CT dose can be optimized.

Materials And Methods: All chest CT examinations performed between July 2016 and April 2017 with and without contrast material, CT of the pulmonary arteries, and abdominopelvic CT with and without contrast material were included in this retrospective study. Dw and SSDE were automatically calculated for all scans using a previously validated in-house developed Matlab software and stored into our CT dose monitoring system. CT dose data were analyzed as regards the updated ACR DRLs (size groups: 21-25 cm, 25-29 cm, 29-33 cm, 33-37 cm, 37-41 cm). SSDE and volumetric computed tomography dose index (CTDIvol) were used as CT dose parameter.

Results: Overall, 30,002 CT examinations were performed in the study period, 3860 of which were included in the analysis (mean age 62.1 ± 16.4 years, Dw 29.0 ± 3.3 cm; n = 577 chest CT without contrast material, n = 628 chest CT with contrast material, n = 346 CT of chest pulmonary, n = 563 abdominopelvic CT without contrast material, n = 1746 abdominopelvic CT with contrast material). Mean SSDE and CTDIvol relative to the updated DRLs were 43.3 ± 26.4 and 45.1 ± 27.9% for noncontrast chest CT, 52.3 ± 23.1 and 52.0 ± 23.1% for contrast-enhanced chest CT, 68.8 ± 29.5 and 70.0 ± 31.0% for CT of pulmonary arteries, 41.9 ± 29.2 and 43.3 ± 31.3% for noncontrast abdominopelvic CT, and 56.8 ± 22.2 and 58.8 ± 24.4% for contrast-enhanced abdominopelvic CT. Lowest dose compared to the DRLs was found for the Dw group of 21-25 cm in noncontrast abdominopelvic CT (SSDE 30.4 ± 21.8%, CTDIvol 30.8 ± 21.4%). Solely the group of patients with a Dw of 37-41 cm undergoing noncontrast abdominopelvic CT exceeded the ACR DRL (SSDE 100.3 ± 59.0%, CTDIvol 107.1 ± 63.5%).

Conclusions: On average, mean SSDE and CTDIvol of our institutional chest and abdominopelvic CT protocols were lower than the updated 2017 ACR DRLs. Size-specific subgroup analysis revealed a wide variability of SSDE and CTDIvol across CT protocols and patient size groups with a transgression of DRLs in noncontrast abdominopelvic CT of large patients (Dw 37-41 cm).
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http://dx.doi.org/10.1016/j.acra.2018.03.005DOI Listing
December 2018

Institutional computed tomography diagnostic reference levels based on water-equivalent diameter and size-specific dose estimates.

J Radiol Prot 2018 Jun 20;38(2):536-548. Epub 2017 Dec 20.

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

Size-specific institutional diagnostic reference levels (DRLs) were generated for chest and abdominopelvic computed tomography (CT) based on size-specific dose estimates (SSDEs) and depending on patients' water-equivalent diameter (Dw). 1690 CT examinations were included in the IRB-approved retrospective study. SSDEs based on the mean water-equivalent diameter of the entire scan volume were calculated automatically. SSDEs were analyzed for different patient sizes and institutional DRLs (iDRLS; 75% percentiles) based on Dw and SSDEs were generated. iDRLs were compared to the national DRLs. Mean volumetric computed tomography dose index (CTDIvol), Dw and SSDEs for all 1690 CT examinations were 7.2 ± 4.0 mGy (0.84-47.9 mGy), 29.0 ± 3.4 cm and 8.5 ± 3.8 mGy (1.2-37.7 mGy), respectively. Overall, the mean SSDEs of all CT examinations were higher than the CTDIvol in chest CT, abdominopelvic CT and upper abdominal CT, respectively (p < 0.001 for all). There was a strong linear correlation between Dw and SSDEs in chest (R = 0.66), abdominopelvic (R = 0.98) and upper abdominal CT (R = 0.96) allowing for the implementation of size-specific institutional DRLs based on SSDEs and patients' Dw. We generated size-specific, Dw-dependent institutional DRLs based on SSDEs, which allow for easier and more comprehensive analyses of CT radiation exposure. Our results indicate that implementation of SSDEs into national DRLs may be beneficial.
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http://dx.doi.org/10.1088/1361-6498/aaa32cDOI Listing
June 2018

Accuracy of Size-Specific Dose Estimate Calculation from Center Slice in Computed Tomography.

Radiat Prot Dosimetry 2018 02;178(3):343

Department of Diagnostic and Interventional Radiology, Medical Faculty, University Dusseldorf, Moorenstraße 5, 40 225 Düsseldorf, Germany.

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http://dx.doi.org/10.1093/rpd/ncx119DOI Listing
February 2018

Iterative metal artefact reduction (MAR) in postsurgical chest CT: comparison of three iMAR-algorithms.

Br J Radiol 2017 Nov 22;90(1079):20160778. Epub 2017 Aug 22.

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

Objectives: The purpose of this study was to evaluate the impact of three novel iterative metal artefact (iMAR) algorithms on image quality and artefact degree in chest CT of patients with a variety of thoracic metallic implants.

Methods: 27 postsurgical patients with thoracic implants who underwent clinical chest CT between March and May 2015 in clinical routine were retrospectively included. Images were retrospectively reconstructed with standard weighted filtered back projection (WFBP) and with three iMAR algorithms (iMAR-Algo1 = Cardiac algorithm, iMAR-Algo2 = Pacemaker algorithm and iMAR-Algo3 = ThoracicCoils algorithm). The subjective and objective image quality was assessed.

Results: Averaged over all artefacts, artefact degree was significantly lower for the iMAR-Algo1 (58.9 ± 48.5 HU), iMAR-Algo2 (52.7 ± 46.8 HU) and the iMAR-Algo3 (51.9 ± 46.1 HU) compared with WFBP (91.6 ± 81.6 HU, p < 0.01 for all). All iMAR reconstructed images showed significantly lower artefacts (p < 0.01) compared with the WFPB while there was no significant difference between the iMAR algorithms, respectively. iMAR-Algo2 and iMAR-Algo3 reconstructions decreased mild and moderate artefacts compared with WFBP and iMAR-Algo1 (p < 0.01).

Conclusion: All three iMAR algorithms led to a significant reduction of metal artefacts and increase in overall image quality compared with WFBP in chest CT of patients with metallic implants in subjective and objective analysis. The iMARAlgo2 and iMARAlgo3 were best for mild artefacts. IMARAlgo1 was superior for severe artefacts. Advances in knowledge: Iterative MAR led to significant artefact reduction and increase image-quality compared with WFBP in CT after implementation of thoracic devices. Adjusting iMAR-algorithms to patients' metallic implants can help to improve image quality in CT.
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http://dx.doi.org/10.1259/bjr.20160778DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5963368PMC
November 2017

ACCURACY OF SIZE-SPECIFIC DOSE ESTIMATE CALCULATION FROM CENTER SLICE IN COMPUTED TOMOGRAPHY.

Radiat Prot Dosimetry 2018 Jan;178(1):8-19

Department of Diagnostic and Interventional Radiology, Medical Faculty, University Dusseldorf, Moorenstraße 5, 40 225 Düsseldorf, Germany.

To evaluate the accuracy of size-specific dose estimate (SSDE) calculation from center slice with water-equivalent diameter (Dw) and effective diameter (Deff). A total of 1812 CT exams (1583 adult and 229 pediatric) were included in this retrospective study. Dw and Deff were automatically calculated for all slices of each scan. SSDEs were calculated with two methods: (1) from the center slice; and (2) from all slices of the volume, which was regarded as the reference standard. Impact of patient weight, height and body mass index (BMI) on SSDE accuracy was assessed. The mean difference between overall SSDE and the center slice approach ranged from 2.0 ± 1.7% (range: 0-15.5%) for pediatric chest to 5.0 ± 3.2% (0-17.2%) for adult chest CT. Accuracy of the center slice SSDE approach correlated with patient size (BMI: r = 0.15-0.43; weight r = 0.26-0.49) which led to SSDE overestimation in small and underestimation in large patients. SSDE calculation using the center slice leads to an error of 2-5%; however, SSDE is underestimated in large patients and overestimation in small patients.
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http://dx.doi.org/10.1093/rpd/ncx069DOI Listing
January 2018

Optimizing radiation exposure in screening of body packing: image quality and diagnostic acceptability of an 80 kVp protocol with automated tube current modulation.

Forensic Sci Med Pathol 2017 Jun 7;13(2):145-150. Epub 2017 Mar 7.

Department of Diagnostic and Interventional Radiology, University Dusseldorf, Medical Faculty, Moorenstr 5, D-40225, Dusseldorf, Germany.

The aim of this study was to evaluate the objective and subjective image quality of a novel computed tomography (CT) protocol with reduced radiation dose for body packing with 80 kVp and automated tube current modulation (ATCM) compared to a standard body packing CT protocol. 80 individuals who were examined between March 2012 and July 2015 in suspicion of ingested drug packets were retrospectively included in this study. Thirty-one CT examinations were performed using ATCM and a fixed tube voltage of 80 kVp (group A). Forty-nine CT examinations were performed using a standard protocol with a tube voltage of 120 kVp and a fixed tube current time product of 40 mAs (group B). Subjective and objective image quality and visibility of drug packets were assessed. Radiation exposure of both protocols was compared. Contrast-to-noise ratio (group A: 0.56 ± 0.36; group B: 1.13 ± 0.91) and Signal-to-noise ratio (group A: 3.69 ± 0.98; group B: 7.08 ± 2.67) were significantly lower for group A compared to group B (p < 0.001). Subjectively, image quality was decreased for group A compared to group B (2.5 ± 0.8 vs. 1.2 ± 0.4; p < 0.001). Attenuation of body packets was higher with the new protocol (group A: 362.2 ± 70.3 Hounsfield Units (HU); group B: 210.6 ± 60.2 HU; p = 0.005). Volumetric Computed Tomography Dose Index (CTDIvol) and Dose Length Product (DLP) were significantly lower in group A (CTDIvol 2.2 ± 0.9 mGy, DLP 105.7 ± 52.3 mGycm) as compared to group B (CTDIvol 2.7 ± 0.1 mGy, DLP 126.0 ± 9.7 mGycm, p = 0.002 and p = 0.01). The novel 80 kVp CT protocol with ATCM leads to a significant dose reduction compared to a standard CT body packing protocol. The novel protocol led to a diagnostic image quality and cocaine body packets were reliably detected due to the high attenuation.
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http://dx.doi.org/10.1007/s12024-017-9848-7DOI Listing
June 2017

Value of delayed gadolinium-enhanced magnetic resonance imaging of cartilage for the pre-operative assessment of cervical intervertebral discs.

J Orthop Res 2017 08 14;35(8):1824-1830. Epub 2016 Oct 14.

Neurosurgical Department, University Hospital, Dusseldorf, Germany.

The study was performed to preoperatively assess the cartilage integrity of cervical intervertebral discs (IVDs) using Delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC). Therefore, 53 cervical intervertebral discs of nine preoperative patients with neck and shoulder/arm pain scheduled for discectomy (five females, four males; mean age: 47.1 ± 8.4 years; range: 36-58 years) were included for biochemical analysis in this retrospective study. The patients underwent 3T magnetic resonance imaging (MRI) including biochemical imaging with dGEMRIC and morphological, sagittal T2 weighted (T2w) imaging. Cervical IVDs were rated using an MRI based grading system for cervical IVDs on T2w images. Region-of-interest measurements were performed in the nucleus pulposus (NP) and annulus fibrosus (AF) and a dGEMRIC index was calculated. Our results demonstrated that IVDs scheduled for discectomy showed significantly lower dGEMRIC index compared to IVDs that did not require surgical intervention in NP and AF (NP: 898.4 ± 191.9 ms vs. 1,150.3 ± 320.7 ms, p = 0.008; AF: 738.7 ± 183.8 ms vs. 984.6 ± 178.9 ms, p = 0.008). For Miyazaki score 3, the dGEMRIC indices were significantly lower in IVDs scheduled for surgery compared to non-operated discs for NP (p = 0.043) and AF (p = 0.018). In conclusion we could demonstrate that biochemical imaging with dGEMRIC is feasible in cervical IVDs. Significantly lower dGEMRIC index suggested GAG depletion in degenerated cervical IVD, scheduled for discectomy. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1824-1830, 2017.
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http://dx.doi.org/10.1002/jor.23454DOI Listing
August 2017

Metal Artifact Reduction in Computed Tomography After Deep Brain Stimulation Electrode Placement Using Iterative Reconstructions.

Invest Radiol 2017 Jan;52(1):18-22

From the *Department of Diagnostic and Interventional Radiology, Medical Faculty, University of Dusseldorf, Dusseldorf; and †Computed Tomography, Siemens Healthcare GmbH, Forchheim, Germany.

Objectives: Diagnostic accuracy of intraoperative computed tomography (CT) after deep brain stimulation (DBS) electrode placement is limited due to artifacts induced by the metallic hardware, which can potentially mask intracranial postoperative complications. Different metal artifact reduction (MAR) techniques have been introduced to reduce artifacts from metal hardware in CT. The purpose of this study was to assess the impact of a novel iterative MAR technique on image quality and diagnostic performance in the follow-up of patients with DBS electrode implementation surgery.

Materials And Methods: Seventeen patients who had received routine intraoperative CT of the head after implantation of DBS electrodes between March 2015 and June 2015 were retrospectively included. Raw data of all patients were reconstructed with standard weighted filtered back projection (WFBP) and additionally with a novel iterative MAR algorithm. We quantified frequencies of density changes to assess quantitative artifact reduction. For evaluation of qualitative image quality, the visibility of numerous cerebral anatomic landmarks and the detectability of intracranial electrodes were scored according to a 4-point scale. Furthermore, artifact strength overall and adjacent to the electrodes was rated.

Results: Our results of quantitative artifact reduction showed that images reconstructed with iterative MAR (iMAR) contained significantly lower metal artifacts (overall low frequency values, 1608.6 ± 545.5; range, 375.5-3417.2) compared with the WFBP (overall low frequency values, 4487.3 ± 875.4; range, 2218.3-5783.5) reconstructed images (P < 0.004). Qualitative image analysis showed a significantly improved image quality for iMAR (overall anatomical landmarks, 2.49 ± 0.15; median, 3; range, 0-3; overall electrode characteristics, 2.35 ± 0.16; median, 2; range, 0-3; artifact characteristics, 2.16 ± 0.08; median, 2.5; range, 0-3) compared with WFBP (overall anatomical landmarks, 1.21 ± 0.64; median, 1; range, 0-3; overall electrode characteristics, 0.74 ± 0.37; median, 1; range, 0-2; artifact characteristics, 0.51 ± 0.15; median, 0.5; range, 0-2; P < 0.002).

Conclusions: Reconstructions of cranial CT images with the novel iMAR algorithm in patients after DBS implantation allows an efficient reduction of metal artifacts near DBS electrodes compared with WFBP reconstructions. We demonstrated an improvement of quantitative and qualitative image quality of iMAR compared with WFBP in patients with DBS electrodes.
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http://dx.doi.org/10.1097/RLI.0000000000000296DOI Listing
January 2017

Stent Lumen Visibility in Single-energy CT Angiography: Does Tube Potential Matter?

Acad Radiol 2016 06 6;23(6):752-9. Epub 2016 May 6.

Department of Diagnostic and Interventional Radiology, Medical Faculty, University Dusseldorf, Moorenstraße 5, 40225 Dusseldorf, Germany.

Rationale And Objectives: There has been a trend toward lowering tube potential in computed tomography angiography (CTA) examinations to reduce radiation dose or contrast medium dose. The aim of this study was to evaluate the influence of tube potential on peripheral artery in-stent lumen visibility in CTA examinations.

Materials And Methods: Nine different peripheral artery stents were placed in a vessel phantom (inner diameter: 5 mm, surrounded by water) and scanned consecutively using a 128-row CT scanner with 70, 80, 100, 120, and 140 kV and two different concentrations of contrast medium to simulate contrast-enhanced blood. Medium-smooth and ultra-sharp reconstruction kernels with filtered back projection (B30f, B46f) and iterative reconstruction technique (I30f, I46f) were used. Visible in-stent lumen diameter and artifact width were evaluated using a semiautomatic software tool. All stents were scanned with digital angiography, which was regarded as the reference standard.

Results: Averaged over all stents, visible in-stent lumen diameter ranged from 1.30 ± 0.21 mm (CM2/70 kV/I30f) to 3.13 ± 0.32 mm (CM1/120 kV/I46f). In-stent lumen diameters were significantly higher for 120 and 140 kV compared to 70 kV (2.39 ± 0.73 and 2.39 ± 0.66 mm vs 1.99 ± 0.69 mm; P = 0.01 and P = 0.005). Ultra-sharp reconstruction kernels lead to significantly better in-stent lumen visibility than smooth reconstruction kernels (B46f: 2.74 ± 0.34 mm vs B30f: 1.57 ± 0.36 mm; P < 0.001, respectively). Furthermore, in-stent lumen visibility was improved for iterative reconstructions compared to filtered back projection (I46f: 2.93 ± 0.30 mm vs B46f: 2.74 ± 0.34 mm; P < 0.001). Contrast medium concentration did not influence in-stent lumen visibility.

Conclusions: Despite all known benefits of low kV CTA protocols, the use of a very low tube potential may hamper in-stent lumen visibility. A sharp kernel may be of value when evaluating the inner lumen of vascular stents.
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http://dx.doi.org/10.1016/j.acra.2016.03.012DOI Listing
June 2016

CT pulmonary angiography: simultaneous low-pitch dual-source acquisition mode with 70 kVp and 40 ml of contrast medium and comparison with high-pitch spiral dual-source acquisition with automated tube potential selection.

Br J Radiol 2016 Jun 23;89(1062):20151059. Epub 2016 Mar 23.

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

Objective: To assess the feasibility of a 70-kVp CT pulmonary angiography (CTPA) protocol using simultaneous dual-source (SimDS) acquisition mode with 40 ml of contrast medium (CM) and comparison with a high-pitch spiral dual-source (SpiralDS) acquisition protocol with automated tube potential selection (ATPS).

Methods: Following the introduction of a new 70-kVp/40-ml SimDS-CTPA protocol in December 2014 for all patients with a body mass index (BMI) below 35 kg m(-2), the first 35 patients were retrospectively included in this study and assigned to Group A (BMI: 27 ± 4 kg m(-2), age: 66 ± 15 years). The last 35 patients with a BMI below 35 kg m(-2) who had received SpiralDS-CTPA with ATPS were included for comparison (Group B) (70 ml CM; BMI: 27 ± 4 kg m(-2), age: 68 ± 16 years). Subjective image quality (image quality) was assessed by two radiologists (from 1, non-diagnostic, to 4, excellent). Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), volumetric CT dose index (CTDIvol), dose-length product (DLP) and effective dose were assessed.

Results: All examinations were of diagnostic image quality. Subjective image quality, SNR and CNR were comparable between Groups A and B (3.7 ± 0.6 vs 3.7 ± 0.5, 14.6 ± 6.0 vs 13.9 ± 3.7 and 12.4 ± 5.7 vs 11.6 ± 3.3, respectively; p > 0.05). CTDIvol, DLP and effective dose were significantly lower in Group A than in Group B (4.5 ± 1.6 vs 7.5 ± 2.1 mGy, 143.3 ± 44.8 vs 278.3 ± 79.44 mGy cm and 2.0 ± 0.6 vs 3.9 ± 1.1 mSv, respectively; p < 0.05).

Conclusion: 70-kVp SimDS-CTPA with 40 ml of CM is feasible and provides diagnostic image quality, while radiation dose and CM can be reduced by almost 50% and 40%, respectively, compared with a SpiralDS-CTPA protocol with ATPS.

Advances In Knowledge: 70-kVp SimDS-CTPA with 40 ml of CM is feasible in patients with a BMI up to 35 kg m(-2) and can help reduce radiation exposure and CM in these patients.
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http://dx.doi.org/10.1259/bjr.20151059DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5258170PMC
June 2016

Metal artifact reduction (MAR) based on two-compartment physical modeling: evaluation in patients with hip implants.

Acta Radiol 2017 Jan 2;58(1):70-76. Epub 2016 Mar 2.

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

Background: Artifacts from metallic implants can hinder image interpretation in computed tomography (CT). Image quality can be improved using metal artifact reduction (MAR) techniques.

Purpose: To evaluate the impact of a MAR algorithm on image quality of CT examinations in comparison to filtered back projection (FBP) in patients with hip prostheses.

Material And Methods: Twenty-two patients with 25 hip prostheses who underwent clinical abdominopelvic CT on a 64-row CT were included in this retrospective study. Axial images were reconstructed with FBP and five increasing MAR levels (M30-34). Objective artifact strength (OAS) (SI-SI) was assessed by region of interest (ROI) measurements in position of the strongest artifact (SI) and in an osseous structure without artifact (SI) (in Hounsfield units [HU]). Two independent readers evaluated subjective image quality regarding metallic hardware, delineation of bone, adjacent muscle, and pelvic organs on a 5-point scale (1, non-diagnostic; 5, excellent image quality). Artifacts in the near field, far field, and newly induced artifacts due to the MAR technique were analyzed.

Results: OAS values were: M34: 243.8 ± 155.4 HU; M33: 294.3 ± 197.8 HU; M32: 340.5 ± 210.1 HU; M31: 393.6 ± 225.2 HU; M30: 446.8 ± 224.2 HU and FBP: 528.9 ± 227.7 HU. OAS values were significantly lower for M32-34 compared to FBP (P < 0.01). For overall subjective image quality, results were: FBP, 2.0 ± 0.2; M30, 2.3 ± 0.8; M31, 2.6 ± 0.5; M32, 3.0 ± 0.6; M33, 3.5 ± 0.6; and M34, 3.8 ± 0.4 (P < 0.001 for M30-M34 vs. FBP, respectively). Increasing MAR levels resulted in new artifacts in 17% of reconstructions.

Conclusion: The investigated MAR algorithm led to a significant reduction of artifacts from metallic hip implants. The highest MAR level provided the least severe artifacts and the best overall image quality.
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http://dx.doi.org/10.1177/0284185116633911DOI Listing
January 2017

CT angiography of the aorta using 80 kVp in combination with sinogram-affirmed iterative reconstruction and automated tube current modulation: Effects on image quality and radiation dose.

J Med Imaging Radiat Oncol 2016 Apr 7;60(2):187-93. Epub 2016 Jan 7.

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

Introduction: The objective of this study was to evaluate image quality and radiation dose of a CT angiography (CTA) protocol using 80 kVp in combination with iterative reconstruction and automated tube current modulation.

Methods: Ninety-five aortic CTA examinations were included in this study. A novel 80 kVp aortic CTA-protocol with iterative reconstruction was introduced in our department in March 2012 for patients with a body mass index (BMI) below 32 kg/m(2). The first 72 consecutive examinations were retrospectively assigned to group A (56 patients, 42 men, 14 women, mean age 69.6 ± 10.7 years, BMI range 19.7-31.1 kg/m(2)). For comparison, the last 23 consecutive examinations performed with the old protocol (100 kVp) were assigned to group B (21 patients, 13 men, 8 women, mean age 67.4 ± 11.1 years, BMI range 19.7-31.9 kg/m(2)). Thoracic and abdominal contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR) and aortic attenuation were assessed. Subjective image quality was rated on a 5-point scale (1 = non diagnostic; 5 = excellent). Furthermore, dose length product (DLP) and volumetric computed tomography dose index (CTDIvol) were analysed.

Results: All examinations achieved diagnostic image quality. Attenuation of the aorta was significantly higher in group A compared with B (thoracic: 443.5 ± 90.5 Hounsfield units (HU) vs. 296.0 ± 61.0 HU; abdominal: 426.3 ± 94.2 HU vs. 283.6 ± 60.5 HU; P < 0.05, respectively). CNR, SNR and subjective image quality were comparable between both groups (CNR: 12.8 ± 3.7 vs. 13.0 ± 7.4; SNR 14.4 ± 3.9 vs. 14.9 ± 8.2; subjective image quality: 4.3 ± 0.6 vs. 4.5 ± 0.6; P > 0.05, respectively). CTDIvol and DLP were significantly lower in group A (1.9 ± 0.5 mGy; 139.2 ± 41.1 mGy × cm) as compared with group B (4.2 ± 1.4 mGy; 292.1 ± 91.5 mGy × cm; P < 0.001, respectively).

Conclusion: Low-dose CTA of the aorta using 80 kVp with iterative reconstruction enables a significant dose reduction of up to 50% compared with a 100 kVp protocol in patients with a BMI below 32 kg/m(2) while diagnostic image quality is maintained.
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http://dx.doi.org/10.1111/1754-9485.12425DOI Listing
April 2016

Does body mass index outperform body weight as a surrogate parameter in the calculation of size-specific dose estimates in adult body CT?

Br J Radiol 2016 23;89(1059):20150734. Epub 2015 Dec 23.

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

Objective: To assess the value of body mass index (BMI) in comparison with body weight as a surrogate parameter for the calculation of size-specific dose estimates (SSDEs) in thoracoabdominal CT.

Methods: 401 CT examinations in 235 patients (196 chest, 205 abdomen; 95 females, 140 males; age 62.5 ± 15.0 years) were analysed in regard to weight, height and BMI (kg m(-2)). Effective diameter (Deff, cm) was assessed on axial CT images. The correlation between BMI, weight and Deff was calculated. SSDEs were calculated based on Deff, weight and BMI and lookup tables were developed.

Results: Overall height, weight, BMI and Deff were 172.5 ± 9.9 cm, 79.5 ± 19.1 kg, 26.6 ± 5.6 kg m(-2) and 30.1 ± 4.3 cm, respectively. There was a significant correlation between Deff and BMI as well as weight (r = 0.85 and r = 0.84; p < 0.05, respectively). Correlation was significantly better for BMI in abdominal CT (r = 0.89 vs r = 0.84; p < 0.05), whereas it was better for weight in chest CT (r = 0.87 vs r = 0.81; p < 0.05). Surrogated SSDEs did not differ significantly from the reference standard with a median absolute relative difference of 4.2% per patient (interquartile range 25-75: 3.1-7.89, range 0-25.3%).

Conclusion: BMI and weight exhibit a significant correlation with Deff in adult patients and can be used as surrogates in the calculation of SSDEs. Using the herein-developed lookup charts, SSDEs can be calculated based on patients' weight and BMI.

Advances In Knowledge: In abdominal CT, BMI has a superior correlation with effective diameter compared with weight, whereas weight is superior in chest CT. Patients' BMI and weight can be used as surrogates in the calculation of SSDEs.
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http://dx.doi.org/10.1259/bjr.20150734DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4986493PMC
July 2016

Diagnostic value of CT-localizer and axial low-dose computed tomography for the detection of drug body packing.

J Forensic Leg Med 2016 Jan 2;37:55-60. Epub 2015 Nov 2.

University Dusseldorf, Medical Faculty, Department of Diagnostic and Interventional Radiology, Moorenstr. 5, D-40225 Dusseldorf, Germany.

Objectives: The purpose of this study was to assess the diagnostic performance of CT-localizers in the detection of intracorporal containers.

Methods: This study was approved by the research ethics committee of our clinic. From March 2012 to March 2013, 108 subjects were referred to our institute with suspected body packing. The CT-localizer and the axial CT-images were compared by two blinded observers retrospectively. Presence of body packs was assessed in consensus. Sensitivity and specificity, PPV and NPV of the CT-localizer were calculated.

Results: Packets were detected in the CT-localizer of 19 suspects. In 28 of 108 cases packs were detected in axial CT-images. Sensitivity of CT-localizer for detection of packs was 0.68, and specificity was 1.00. There were no cases rated as false positive. The PPV was 1.0 and the NPV was 0.89. The omission of the axial CT-images would have led to a mean radiation dose reduction of 1.94 ± 0.5 mSv.

Conclusions: The value of CT-localizers lies in their high PPV. Localizers are limited by low sensitivity, compared to axial CT-images in screening of potential body packers. However, in positive cases their high PPV may possibly allow to omit the complete axial abdominal CT to achieve even lower radiation exposure.
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http://dx.doi.org/10.1016/j.jflm.2015.10.009DOI Listing
January 2016

Value of 3D TEE for LAA Morphology.

JACC Cardiovasc Imaging 2015 Sep;8(9):1107-1110

Division of Cardiology, Pulmonology, and Vascular Medicine, Medical Faculty, University of Düsseldorf, Düsseldorf, Germany. Electronic address:

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http://dx.doi.org/10.1016/j.jcmg.2014.07.030DOI Listing
September 2015

Low-tube voltage 100 kVp MDCT in screening of cocaine body packing: image quality and radiation dose compared to 120 kVp MDCT.

Abdom Imaging 2015 Oct;40(7):2152-8

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

Purpose: The aim of this study was to evaluate the impact of a reduced tube potential (100 kVp) for non-enhanced abdominal low-dose CT on radiation dose and image quality (IQ) in the detection of body packing.

Methods: This retrospective study was approved by the local research ethics committee of our clinic. From March 2012 to July 2014, 99 subjects were referred to our institute with suspected body packing. 50 CT scans were performed using a 120 kVp protocol (group A), and 49 CTs were performed using a low-dose protocol with a tube voltage of 100 kVp (group B). Subjective and objective IQ were assessed. DLP and CTDIvol were analyzed.

Results: All examinations were of diagnostic IQ. Objective IQ was not significantly different between the 120 kVp and 100 kVp protocol. Mean density of solid and liquid body packets was 210 ± 60.2 HU at 120 kVp and 250.6 ± 29.7 HU at 100 kVp. Radiation dose was significantly lower in group B as compared to group A (p < 0.05). In group A, body packs were detected in 16 (32%) of the 50 patients. In group B, packets were observed in 15 (31%) of 49 patients. Laboratory analysis detected cocaine in all smuggled body packs.

Conclusions: Low-tube voltage 100 kVp MDCT with automated tube current modulation in screening of illegal drugs leads to a diagnostic IQ and significant dose reduction compared to 120 kVp low-tube voltage protocols. Despite lower radiation dose, liquid and solid cocaine containers retain high attenuation and are easily detected.
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http://dx.doi.org/10.1007/s00261-015-0464-2DOI Listing
October 2015

Evaluation of a simplified version of the Rheumatoid Arthritis Magnetic Resonance Imaging Score (RAMRIS) comprising 5 joints (RAMRIS5).

Clin Exp Rheumatol 2015 Mar-Apr;33(2):209-15. Epub 2015 Jan 29.

Department of Rheumatology, University of Dusseldorf, Medical Faculty, Dusseldorf, Germany.

Objectives: The objective of this study was to evaluate a simplified version of the Rheumatoid Arthritis Magnetic Resonance Imaging Score (RAMRIS) reduced to five joints of the hand (RAMRIS5).

Methods: 94 patients with rheumatoid arthritis (62 female; age 59±12 years, range 25-83 years; disease duration 60±90 months (median: 22 months, first quartile: 7 months, third quartile: 66 months) from the REMISSION PLUS study cohort who had complete files on C-reactive protein (CRP) levels and Disease Activity Score of 28 joints (DAS28) and complete MRI of the clinical dominant hand at baseline and after one year under anti-rheumatic therapy (follow-up time 12.5±1.1 months) in a dedicated extremity MRI scanner at 0.2T were included in this retrospective study.

Results: There was a strong correlation between RAMRIS5 and the RAMRIS sum-score for all patients (r=0.87, p<0.001) at baseline and follow-up (r=0.87, p<0.001). Among the subscores there was a significant correlation between RAMRIS5 and RAMRIS-MCP (baseline: r=0.66, p<0.001; follow-up: r=0.74, p<0.001) as well as between RAMRIS5 and RAMRIS-wrist (baseline: r=0.72, p<0.001, follow-up: r=0.69, p<0.001) at baseline and follow-up.

Conclusions: RAMRIS5, a modified shorter RAMRIS score based on five joints of the hand is a viable tool for semi-quantitative assessment of joint damage in RA. This abbreviated score might reduce the time needed for image analysis in MRI-controlled studies in RA and might facilitate the use of MRI in studies on therapy response assessment in RA.
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May 2015

Evaluation of a high iodine delivery rate in combination with low tube current for dose reduction in pulmonary computed tomography angiography.

J Thorac Imaging 2014 Sep;29(5):293-7

*Department of Diagnostic and Interventional Radiology, Medical Faculty, University of Duesseldorf, Duesseldorf †Bracco Imaging, Global Medical & Regulatory Affairs, Konstanz, Germany.

Purpose: The present study evaluates the combination of a high iodine delivery rate with a low tube current-time product for pulmonary computed tomography angiography (CTA).

Materials And Methods: One-hundred nineteen consecutive patients undergoing pulmonary CTA for suspected pulmonary embolism were included and imaged on a 128-row computed tomography scanner at 100 kVp using highly concentrated contrast material (85 mL Iomeprol; 400 mg iodine/mL). The protocol entailed a flow rate of 5 mL/s and 90 mAs for group A, 3.5 mL/s and 135 mAs for group B, 5 mL/s and 135 mAs for group C, and 3.5 mL/s and 90 mAs for group D. Signal-to-noise ratio and contrast-to-noise ratio (CNR) were determined for the pulmonary artery. Subjective image quality (IQ) was rated on a 5-point scale (1=nondiagnostic IQ to 5=excellent IQ).

Results: CNR did not differ significantly between groups A (43.7±27.7), B (34.5±17.9), and C (38.9±13.8), as well as between groups B and D (29.9±11.2). CNR was higher in groups A and C than in group D (P<0.02). Subjective IQ was higher in group A than in groups B and D (P<0.05). Subjective IQ was significantly higher in group A compared with group D (P=0.026) and in group C compared with group D (P=0.007).

Conclusions: A high iodine delivery rate permits dose reduction in pulmonary CTA and can be recommended in patients with suspected pulmonary embolism.
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http://dx.doi.org/10.1097/RTI.0000000000000099DOI Listing
September 2014