Publications by authors named "Stephan Waldeck"

17 Publications

  • Page 1 of 1

Prediction of cardiac events with non-contrast magnetic resonance feature tracking in patients with ischaemic cardiomyopathy.

ESC Heart Fail 2021 Nov 24. Epub 2021 Nov 24.

1st Department of Medicine, University Medical Centre Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, Heidelberg, D-68167, Germany.

Aims: The aim of this study was to evaluate the prognostic value of feature tracking (FT) derived cardiac magnetic resonance (CMR) strain parameters of the left ventricle (LV)/right ventricle (RV) in ischaemic cardiomyopathy (ICM) patients treated with an implantable cardioverter-defibrillator (ICD). Current guidelines suggest a LV-ejection fraction ≤35% as major criterion for ICD implantation in ICM, but this is a poor predictor for arrhythmic events. Supplementary parameters are missing.

Methods And Results: Ischaemic cardiomyopathy patients (n = 242), who underwent CMR imaging prior to primary and secondary implantation of ICD, were classified depending on EF ≤ 35% (n = 188) or >35% (n = 54). FT parameters were derived from steady-state free precession cine views using dedicated software. The primary endpoint was a composite of cardiovascular mortality (CVM) and/or appropriate ICD therapy. There were no significant differences in FT-function or LV-/RV-function parameters in patients with an EF ≤ 35% correlating to the primary endpoint. In patients with EF > 35%, standard CMR functional parameters, such as LV-EF, did not reveal significant differences. However, significant differences in most FT parameters correlating to the primary endpoint were observed in this subgroup. LV-GLS (left ventricular-global longitudinal strain) and RV-GRS (right ventricular-global radial strain) revealed the best diagnostic performance in ROC curve analysis. The combination of LV-GLS and RV-GRS showed a sensitivity of 85% and a specificity of 76% for the prediction of future events.

Conclusions: The impact of FT derived measurements in the risk stratification of patients with ICM depends on LV function. The combination of LV-GLS/RV-GRS seems to be a predictor of cardiovascular mortality and/or appropriate ICD therapy in patients with EF > 35%.
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http://dx.doi.org/10.1002/ehf2.13712DOI Listing
November 2021

Impact of medical imaging on the epigenome - low-dose exposure in the course of computed tomography does not induce detectable changes of DNA-methylation profiles in peripheral blood cells.

Int J Radiat Biol 2021 Dec 2:1-6. Epub 2021 Dec 2.

Bundeswehr Institute of Radiobiology Affiliated to Ulm University, Munich, Germany.

Background: Computed tomography (CT) is a main contributor to artificial low-dose exposure. Understanding the biological effects induced by CT exposure and their dependency on the characteristics of photon spectra is essential for knowledge-driven risk assessment. In a previous gene expression study, we have identified upregulation of , , , and after ex vivo exposure with single-energy CT and dual-energy CT (DECT). In this study, we focused on CT-induced changes of DNA methylation. This epigenetic modification of DNA is a central regulator of gene expression and instrumental in preserving genome integrity. Previous studies reported focal hypermethylation and global hypomethylation after exposure with doses above 100 mSv, however, the effect of low dose exposure on DNA methylation is hardly explored.

Materials And Methods: DNA was isolated from peripheral blood of three healthy individuals 6 h after ex vivo exposition to single-energy (80 kV and 150 kV) and DECT (80 kV/Sn150 kV) with a calculated effective dose of 7.0 ± 0.08 mSv. The experimental setting was identical to the one used in our previous gene expression study enabling a direct comparison of gene expression results with changes of DNA methylation identified in this study. DNA methylation was analyzed by high-throughput sequencing of bisulfite-treated DNA targeted methylation sequencing.

Results: Unsupervised hierarchical clustering based on DNA methylation profiles of all samples created three distinct clusters. Formation of these three clusters was solely determined by the origin of samples, indicating the absence of prominent irradiation-associated changes of DNA methylation. In line with this observation, inter-individual comparison of non-irradiated samples revealed 1163, 1224 and 4550 significant differentially methylated regions (DMRs), respectively, whereas the pairwise comparison of irradiated and non-irradiated samples failed to identify irradiation-induced DMRs in any of the three probands. This even applied to the genomic regions harboring , , , and , the five genes known to be upregulated by CT exposure.

Conclusions: CT exposure with various photon spectra did not result in detectable changes of DNA methylation. However, minor effects in a subpopulation of irradiated cells cannot be ruled out. Thus, future studies with extended observation intervals are needed to investigate DNA methylation changes that are induced by indirect effects at later points of time or become detectable by clonal expansion of affected cells. Moreover, our data suggest that DNA methylation analysis is less sensitive in detecting immediate effects of low-dose irradiation when compared to gene expression analysis.
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http://dx.doi.org/10.1080/09553002.2021.2004329DOI Listing
December 2021

Determination of Cochlear Duct Length With 3D Two-dimensional Methods: A Retrospective Clinical Study of Imaging by Computed Tomography and Cone Beam Computed Tomography.

In Vivo 2021 Nov-Dec;35(6):3339-3344

Department of Diagnostic and Interventional Radiology and Neuroradiology, Bundeswehr Central Hospital Koblenz, Koblenz, Germany.

Background: The aim of this study was to compare three different methods for measurement of cochlear duct length (CDL) in the clinical setting for two different imaging modalities, namely computed tomography (CT) and cone-beam computed tomography (CBCT).

Patients And Methods: One hundred temporal bone data sets (CT: n=50; CBCT: n=50) of non-malformed cochleae were retrospectively analyzed using three different CDL estimation techniques: 3D curved multiplanar reconstruction (cMPR), 2D cMPR and the A-value formula.

Results: The data sets belonged to 60 patients (34 males, 26 females; mean age=50.28±18.58 years). For both imaging modalities, application of the 3D cMPR estimation technique led to significantly greater mean CDL values than the two-dimensional methods (p<0.0083). The CDL measurements viewed in CT imaging software were significantly shorter than the corresponding CBCT measurements (p<0.05). Using a linear mixed model, differences in CDL by sex (p=0.796), age (p=0.377) and side of ear (p=0.690) were not significant.

Conclusion: The 3D cMPR technique was found to provide the most accurate in vivo CDL measurement in non-malformed cochlea in both CT and CBCT imaging compared to 2D methods. The study results also suggest that the higher spatial resolution in CBCT imaging results in more precise CDL determination than in CT.
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http://dx.doi.org/10.21873/invivo.12631DOI Listing
October 2021

Gene expression changes and DNA damage after ex vivo exposure of peripheral blood cells to various CT photon spectra.

Sci Rep 2021 06 8;11(1):12060. Epub 2021 Jun 8.

Bundeswehr Institute of Radiobiology Affiliated to Ulm University, Neuherbergstrasse 11, 80937, Munich, Germany.

Dual-energy CT provides enhanced diagnostic power with similar or even reduced radiation dose as compared to single-energy CT. Its principle is based on the distinct physical properties of low and high energetic photons, which, however, may also affect the biological effectiveness and hence the extent of CT-induced cellular damage. Therefore, a comparative analysis of biological effectiveness of dual- and single-energy CT scans with focus on early gene regulation and frequency of radiation-induced DNA double strand breaks (DSBs) was performed. Blood samples from three healthy individuals were irradiated ex vivo with single-energy (80 kV and 150 kV) and dual-energy tube voltages (80 kV/Sn150kV) employing a modern dual source CT scanner resulting in Volume Computed Tomography Dose Index (CTDIvol) of 15.79-18.26 mGy and dose length product (DLP) of 606.7-613.8 mGy*cm. Non-irradiated samples served as a control. Differential gene expression in peripheral blood mononuclear cells was analyzed 6 h after irradiation using whole transcriptome sequencing. DSB frequency was studied by 53BP1 + γH2AX co-immunostaining and microscopic evaluation of their focal accumulation at DSBs. Neither the analysis of gene expression nor DSB frequency provided any evidence for significantly increased biological effectiveness of dual-energy CT in comparison to samples irradiated with particular single-energy CT spectra. Relative to control, irradiated samples were characterized by a significantly higher rate of DSBs (p < 0.001) and the shared upregulation of five genes, AEN, BAX, DDB2, FDXR and EDA2R, which have already been suggested as radiation-induced biomarkers in previous studies. Despite steadily decreasing doses, CT diagnostics remain a genotoxic stressor with impact on gene regulation and DNA integrity. However, no evidence was found that varying X-ray spectra of CT impact the extent of cellular damage.
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http://dx.doi.org/10.1038/s41598-021-91023-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8187728PMC
June 2021

The Nipple as a Landmark for Needle Decompression of Tension Pneumothorax in Children - A CT-Based Evaluation and Proposal of an Alternative Insertion Site.

Prehosp Emerg Care 2021 Nov-Dec;25(6):747-752. Epub 2020 Nov 3.

Objective: Needle decompression of tension pneumothorax in children is a rarely encountered but potentially life-saving procedure, that is accompanied by a certain risk of injury. We evaluated the nipple as a landmark for an alternative anterior insertion site and as an aid in localizing lateral insertion sites, as well as its influence on the safety profile of the procedure.

Methods: In thoracic computer tomography scans of children aged 0-10 years, the distance to the closest vital structure was compared between the traditional anterior insertion site (2nd intercostal space midclavicular line) and an alternative anterior insertion site (2nd intercostal space at the nipple line). Furthermore, the level of the nipple at the midaxillary line was investigated as guidance in quickly localizing the lateral insertion site and ensuring an insertion site high enough to avoid intraabdominal injury by the decompression needle. Additionally, correlation of these measures with age was investigated.

Results: The distance to the closest vital structure at the 2nd intercostal space was significantly bigger at the nipple line compared to the midclavicular line (right: 2.23 ± 1.13 cm vs. 0.99 ± 0.80 cm, p < 0.0001; left: 1.92 ± 1.19 cm vs. 0.81 ± 0.70 cm, p < 0.0001). At the midaxillary line, the level of the nipple was at the 4th or 5th intercostal space in the majority of children (right: 83.8%; left: 88.1%). The mean distance from the nipple to the diaphragmatic cupola was 2.63 ± 1.85 cm on the right and 3.40 ± 1.86 cm on the left hemithorax.

Conclusion: When performing anterior needle decompression in children, we recommend inserting the needle at the more lateral insertion site at the 2nd intercostal space at the nipple line. At the lateral decompression sites, the nipple can be used as a marker for localizing the correct intercostal space for insertion and thereby ensuring enough caudad distance to the diaphragm to avoid abdominal injury.
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http://dx.doi.org/10.1080/10903127.2020.1831670DOI Listing
November 2020

Additional CTA-Subtraction Technique in Detection of Pulmonary Embolism-a Benefit for Patients or Only an Increase in Dose?

Health Phys 2020 07;119(1):148-152

German Federal Armed Forces Central Hospital Koblenz, Department for Radiology and Neuroradiology, Koblenz, Germany.

Latest advantages in computed tomography (CT) come with enhanced diagnostic imaging and also sophisticated dose reduction techniques. However, overall exposure to ionizing radiation of patients in Germany rises slightly, which is mainly based on the growing number of performed CT scans. Furthermore, new possibilities in modern imaging, including 4D scans or perfusion protocols, offer new medical insights but require additional scans.In this study, we reevaluated data sets from patients undergoing CT examinations because of suspected pulmonary embolism and compared doses and diagnostic results of the standard protocol to the additional modern CT subtraction technique. Two groups of single-blinded radiologists were provided with CT data sets from 50 patients. One group (G1) had access to full datasets including CT subtraction with perfusion map. The other group (G2) only evaluated conventional CT angiography. Results were compared to final clinical diagnosis. Dose length product (DLP) of CT angiography was compared to CT subtraction technique, which consists of an additional non-contrast-enhanced scan and perfusion map. Effective dose was calculated using a Monte Carlo simulation-based software tool (ImpactDose). Inter-rater agreement of both groups was strong in G1 with κ = .896 and minimal in G2 (κ = .307). Agreement to final diagnosis was strong in both groups (G1, κ = .848; G2, κ = .767). Doses applied using the CT subtraction technique were 34.8% higher than for CT angiography alone (G1 DLP 337.6 ± 171.3 mGy x cm; G2 DLP 220.2 ± 192.8 mGy x cm; p < .001). Calculated effective dose was therefore significantly higher for G1 (G1 4.82 ± 2.20 mSv; G2 3.04 ± 1.33 mSv; p < .001). Our results indicate a benefit of the CT subtraction technique for the detection of pulmonary embolisms in clinical routine, accompanied by an increase in the dose administered. Although CT protocols should always be applied carefully to specific clinical indications in order to maximize the potential for dose reduction and keep the administered dose as low as reasonably achievable, one should never lose sight of the diagnostic benefit, especially in vital clinical indications.
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http://dx.doi.org/10.1097/HP.0000000000001274DOI Listing
July 2020

A case of SARS-CoV-2 pneumonia with successful antiviral therapy in a 77-year-old man with a heart transplant.

Am J Transplant 2020 Jul 11;20(7):1925-1929. Epub 2020 Jun 11.

Department of Internal Medicine, Bundeswehr Central Hospital Koblenz, Koblenz, Germany.

The SARS-CoV-2 infection can be seen as a single disease, but it also affects patients with relevant comorbidities who may have an increased risk of a severe course of infection. In this report, we present a 77-year-old patient with a heart transplant receiving relevant immunosuppressive therapy who tested positive for SARS-CoV-2 after several days of dyspnea, dry cough, and light general symptoms. Computed tomography confirmed interstitial pneumonia. The patient received antiviral therapy with hydroxychloroquine and showed no further deterioration of the clinical state. After 12 days of hospitalization, the patient was released; he was SARS-CoV-2 negative and completely asymptomatic.
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http://dx.doi.org/10.1111/ajt.15932DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7264518PMC
July 2020

CT Irradiation-induced Changes of Gene Expression within Peripheral Blood Cells.

Health Phys 2020 07;119(1):44-51

Bundeswehr Central Hospital Koblenz, Department of Radiology, Rübenacher Straße 170, 56072 Koblenz, Germany.

Computed tomography (CT) is a crucial element of medical imaging diagnostics. The widespread application of this technology has made CT one of the major contributors to medical radiation burden, despite the fact that doses per individual CT scan steadily decrease due to the advancement of technology. Epidemiological risk assessment of CT exposure is hampered by the fact that moderate adverse effects triggered by low doses of CT exposure are likely masked by statistical fluctuations. In light of these limitations, there is need of further insights into the biological processes induced by CT scans to complement the existing knowledge base of risk assessment. This prompted us to investigate the early transcriptomic response of ex vivo irradiated peripheral blood of three healthy individuals. Samples were irradiated employing a modern dual-source-CT-scanner with a tube voltage of 150 kV, resulting in an estimated effective dose of 9.6 mSv. RNA was isolated 1 h and 6 h after exposure, respectively, and subsequently analyzed by RNA deep sequencing. Differential gene expression analysis revealed shared upregulation of AEN, FDXR, and DDB2 6 h after exposure in all three probands. All three genes have previously been discussed as radiation responsive genes and have already been implicated in DNA damage response and cell cycle control after DNA damage. In summary, we substantiated the usefulness of AEN, FDXR, and DDB2 as RNA markers of low dose irradiation. Moreover, the upregulation of genes associated with DNA damage reminds one of the genotoxic nature of CT diagnostics even with the low doses currently applied.
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http://dx.doi.org/10.1097/HP.0000000000001231DOI Listing
July 2020

Detection of Embedded Low-level Radioactive Shrapnel after the Explosion of a Radiological Dispersal Device in Radiological Emergency Imaging.

Health Phys 2020 07;119(1):95-100

Department for Radiology and Neuroradiology, Bundeswehr Central Hospital, Rübenacherstrasse 170, 56072, Koblenz, Germany.

Concern about the threat of a terrorist attack with a Radiological Dispersal Device has increased considerably over the last few years, and this comes along with an immense challenge, especially regarding medical treatment of combined injuries with incorporated radioactive fragments. In such scenarios, the identification and surgical exploration of radioactive fragments is a major issue to prevent further radiation-induced effects like wound healing disorders, onset of acute radiation syndrome, and as a late-effect cancer. However, in a usual emergency setting, it is unclear how this task can be achieved. Within this study, we evaluated the feasibility of different radiological methods to identify and locate an incorporated radioactive fragment. We placed two different Cs sources and several non-radioactive fragments representing sham control samples within a human spine phantom. Standard emergency imaging procedures were performed, including plane radiography and different CT scans (64 row, 384 row dual energy, 320 row without iterative metal artifact reduction), respectively. Eight radiologists were blinded toward the results and asked to identify the radioactive fragments within the provided images. For both sources, correct identification was rather low (15.63%). Furthermore, none of the questioned radiologists (N = 0) stated that they were able to identify the radioactive shrapnel distinctly. Positive predictive value was accordingly low (15.63%). Most participants recommended a scintigraphy-based technique for identification (26.67%) rather than radiographic procedures (6.67%). Identification and location of incorporated small radioactive fragments with low energies by standard radiological procedures prior to surgical exploration is not promising. Nevertheless, procedures that can achieve this aim are needed direly in the case of a terrorist attack with a radiological dispersal device and should be available in an emergency department.
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http://dx.doi.org/10.1097/HP.0000000000001203DOI Listing
July 2020

Index Finger Muscle Fatigue and Pistol Firing Failure.

Hum Factors 2019 11 28;61(7):1066-1076. Epub 2019 Feb 28.

Bundeswehr Institute for Preventive Medicine, Andernach, Germany.

Objective: The aim of this study was to analyze finger strength and effects of muscle fatigue on the ability to shoot.

Background: The finger and hand muscles of soldiers are subject to high loads. For example, the trigger pull of military pistols can amount up to 58 N (≈6 kg) and could cause muscle fatigue in the trigger finger. For soldiers, however, maintaining the ability to shoot is essential for self-defense and survival.

Method: The marksmanship training of 30 German soldiers (15 female) ages 18 to 40 years was evaluated. Three consecutive exercises with a total of 60 rounds were fired from target ranges of 5 and 10 m, equally using a single-action and double-action trigger mode. Maximum voluntary isometric contraction of the index finger (MVC) was measured before and after each of the three firing exercises.

Results: Shooting reduced MVC in female (88.2 ± 15.8 N to 67.3 ± 17.7 N, < .001) and male soldiers (145.8 ± 21.7 N to 112.7 ± 26.6 N, < .001). Of the 30 subjects, 23 were unable to shoot due to fatigue, including 15 of 15 female soldiers. The higher MVC was at rest, the less commonly ( = .73, < .001) and the later ( = 0.82, < .001) task failure occurred. Two intermissions of approximately 6 min did not suffice for a significant recovery.

Conclusion: Excessive trigger pull weight causes muscle fatigue of the index finger and can ultimately lead to task failure during pistol marksmanship training. Short breaks are insufficient for the recovery of finger muscles.

Application: This study presents a new perspective on ideal trigger pull weight, which should be carefully considered by manufacturers to allow repetitive firing and simultaneously ensure safe handling.
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http://dx.doi.org/10.1177/0018720819827457DOI Listing
November 2019

Diagnostic accuracy of third-generation dual-source dual-energy CT: a prospective trial and protocol for clinical implementation.

World J Urol 2019 Apr 3;37(4):735-741. Epub 2018 Aug 3.

Department of Urology, Federal Armed Services Hospital Koblenz, Rübenacher Str. 170, 56072, Koblenz, Germany.

Purpose: Uric acid (UA) calculi can be referred to chemolitholysis rather than invasive treatment. Dual-energy computed tomography (DECT) may be able to distinguish between UA and non-UA (NUA) calculi. The aim of this study was to evaluate the validity of third-generation DECT for the first time and to investigate whether combining DECT with clinical parameters can increase its predictive accuracy.

Materials And Methods: All patients who presented to our emergency department between January 2015 and March 2017 with urinary stones were prospectively included in this observational study and underwent DECT with subsequent interventional stone removal. Stone composition was analyzed using infrared spectrometry as the gold standard. Predictive accuracy of DECT and clinical covariates was computed by assessing univariate and multivariate areas under the curve (AUCs).

Results: Of 84 patients with 144 urinary stones, 10 (11.9%) patients had UA stones according to infrared spectrometry, and the remaining stones were NUA or mixed stones. DECT had a positive predictive value of 100% and a negative predictive value of 98.5% for UA stones. The AUC for urine pH alone was 0.71 and 0.97 for DECT plus urine pH. No UA stones were found in patients with a urine pH above > 5.5. Mean DLP was 225.15 ± 128.60 mGy*cm and mean effective dose was 3.38 ± 1.93 mSv.

Conclusions: DECT is a safe method for assigning patients to oral chemolitholysis. Clinical preselection of patients based on urinary pH (< 6.0) leads to a more liable use of DECT. Third-generation DECT needs significant lower radiation doses compared to previous generations.
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http://dx.doi.org/10.1007/s00345-018-2430-4DOI Listing
April 2019

Investigation of factors potentially influencing calcitonin levels in the screening and follow-up for medullary thyroid carcinoma: a cautionary note.

BMC Clin Pathol 2013 Nov 4;13(1):27. Epub 2013 Nov 4.

Department of General, Visceral and Thoracic Surgery, German Armed Forces Central Hospital, Ruebenacher Strasse 170, Koblenz 56072, Germany.

Background: The malignant transformation of thyroid C cells is associated with an increase in human calcitonin (hCT), which can thus be helpful in the early diagnosis of medullary thyroid carcinoma (MTC). For this reason, hCT levels should be determined in all patients with nodular goitre. Hashimoto's thyroiditis, nodular goitre and proton pump inhibitor (PPI) therapy are factors reported to influence basal serum hCT concentrations. The diagnostic role of mildly to moderately increased hCT levels is thus a matter of debate. In this study, we attempt to clarify the role of the aforementioned factors.

Methods: From 2008 to 2009, we collected data from 493 patients who were divided into five groups. We assessed whether there were significant differences in hCT levels between patients with Hashimoto's thyroiditis, patients with nodular goitre, patients with PPI therapy, and healthy control subjects. In addition, we investigated whether a delayed analysis of blood samples has an effect on serum hCT concentrations.

Results: Immunoradiometric assays (Calcitonin IRMA magnum, MEDIPAN) revealed that the time of analysis did not play a role when low levels were measured. Delayed analysis, however, carried the risk of false low results when serum hCT concentrations were elevated. Men had significantly higher serum hCT levels than women. The serum hCT concentrations of patients with Hashimoto's thyroiditis and nodular goitre were not significantly different from those of control subjects. Likewise, PPI therapy did not lead to a significant increase in serum hCT concentrations regardless of the presence or absence of nodular goitre.

Conclusions: Increases in serum hCT levels are not necessarily attributable to Hashimoto's thyroiditis, nodular goitre or the regular use of PPIs and always require further diagnostic attention.
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http://dx.doi.org/10.1186/1472-6890-13-27DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4175476PMC
November 2013

Influence of sinogram affirmed iterative reconstruction of CT data on image noise characteristics and low-contrast detectability: an objective approach.

PLoS One 2013 13;8(2):e56875. Epub 2013 Feb 13.

Department of Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.

Objectives: To utilize a novel objective approach combining a software phantom and an image quality metric to systematically evaluate the influence of sinogram affirmed iterative reconstruction (SAFIRE) of multidetector computed tomography (MDCT) data on image noise characteristics and low-contrast detectability (LCD).

Materials And Methods: A low-contrast and a high-contrast phantom were examined on a 128-slice scanner at different dose levels. The datasets were reconstructed using filtered back projection (FBP) and SAFIRE and virtual low-contrast lesions (-20HU) were inserted. LCD was evaluated using the multiscale structural similarity index (MS-SIM*). Image noise texture and spatial resolution were objectively evaluated.

Results: The use of SAFIRE led to an improvement of LCD for all dose levels and lesions sizes. The relative improvement of LCD was inversely related to the dose level, declining from 208%(±37%), 259%(±30%) and 309%(±35%) at 25mAs to 106%(±6%), 119%(±9%) and 123%(±8%) at 200mAs for SAFIRE filter strengths of 1, 3 and 5 (p<0.05). SAFIRE reached at least the LCD of FBP at a relative dose of 50%. There was no statistically significant difference in spatial resolution. The use of SAFIRE led to coarser image noise granularity.

Conclusion: A novel objective approach combining a software phantom and the MS-SSIM* image quality metric was used to analyze the detectability of virtual low-contrast lesions against the background of image noise as created using SAFIRE in comparison to filtered back-projection. We found, that image noise characteristics using SAFIRE at 50% dose were comparable to the use of FBP at 100% dose with respect to lesion detectability. The unfamiliar imaging appearance of iteratively reconstructed datasets may in part be explained by a different, coarser noise characteristic as demonstrated by a granulometric analysis.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0056875PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3572072PMC
August 2013

A systematic approach towards the objective evaluation of low-contrast performance in MDCT: combination of a full-reference image fidelity metric and a software phantom.

Eur J Radiol 2012 Nov 29;81(11):3166-71. Epub 2012 Jun 29.

Institute of Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany.

Objectives: To assess the feasibility of an objective approach for the evaluation of low-contrast detectability in multidetector computed-tomography (MDCT) by combining a virtual phantom containing simulated lesions with an image quality metric.

Materials And Methods: A low-contrast phantom containing hypodense spheric lesions (-20 HU) was scanned on a 64-slice MDCT scanner at 4 different dose levels (25, 50, 100, 200 mAs). In addition, virtual round hypodense low-contrast lesions (20 HU object contrast) based on real CT data were inserted into the lesion-free section of the datasets. The sliding-thin-slab algorithm was applied to the image data with an increasing slice-thickness from 1 to 15 slices. For each dataset containing simulated lesions a lesion-free counterpart was reconstructed and post-processed in the same manner. The low-contrast performance of all datasets containing virtual lesions was determined using a full-reference image quality metric (modified multiscale structural similarity index, MS-SSIM*). The results were validated against a reader-study of the real lesions.

Results: For all dose levels and lesion sizes there was no statistically significant difference between the low-contrast performance as determined by the image quality metric when compared to the reader study (p<0.05). The intraclass correlation coefficient was 0.72, 0.82, 0.90 and 0.84 for lesion diameters of 4 mm, 5 mm, 8 mm and 10 mm, respectively. The use of the sliding-thin-slab algorithm improves lesion detectability by a factor ranging from 1.15 to 2.69 when compared with the original axial slice (0.625 mm).

Conclusion: The combination of a virtual phantom and a full-reference image quality metric enables a systematic, automated and objective evaluation of low-contrast detectability in MDCT datasets and correlates well with the judgment of human readers.
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http://dx.doi.org/10.1016/j.ejrad.2012.06.003DOI Listing
November 2012

Intraoperative image guidance in neurosurgery: development, current indications, and future trends.

Radiol Res Pract 2012 8;2012:197364. Epub 2012 May 8.

Department of Neurosurgery, German Federal Armed Forces Hospital, 89081 Ulm, Germany.

Introduction. As minimally invasive surgery becomes the standard of care in neurosurgery, it is imperative that surgeons become skilled in the use of image-guided techniques. The development of image-guided neurosurgery represents a substantial improvement in the microsurgical treatment of tumors, vascular malformations, and other intracranial lesions. Objective. There have been numerous advances in neurosurgery which have aided the neurosurgeon to achieve accurate removal of pathological tissue with minimal disruption of surrounding healthy neuronal matter including the development of microsurgical, endoscopic, and endovascular techniques. Neuronavigation systems and intraoperative imaging should improve success in cranial neurosurgery. Additional functional imaging modalities such as PET, SPECT, DTI (for fiber tracking), and fMRI can now be used in order to reduce neurological deficits resulting from surgery; however the positive long-term effect remains questionable for many indications. Method. PubMed database search using the search term "image guided neurosurgery." More than 1400 articles were published during the last 25 years. The abstracts were scanned for prospective comparative trials. Results and Conclusion. 14 comparative trials are published. To date significant data amount show advantages in intraoperative accuracy influencing the perioperative morbidity and long-term outcome only for cerebral glioma surgery.
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http://dx.doi.org/10.1155/2012/197364DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3357627PMC
August 2012

Influence of multiplanar reformations on low-contrast performance in thin-collimated multidetector computed tomography.

Invest Radiol 2011 Oct;46(10):632-8

Department of Radiology, Hannover Medical School, Germany.

Objectives: : To analyze the influence of multiplanar reformations of thin-collimated multidetector computed tomography datasets on low-contrast performance.

Materials And Methods: : A low-contrast phantom simulating focal hypodense lesions (-20 HU object contrast) was scanned on a 64-slice spiral CT scanner at 4 different dose levels (25 mAs, 50 mAs, 100 mAs, 200 mAs, and no dose modulation). Other scanner parameters were as follows: tube voltage = 120 kVp, rotation time = 0.8 s, reconstructed slice thickness = 0.625 mm, reconstruction interval = 0.5 mm, reconstruction kernel = standard. Coronal reformations were created using the open-source software OsiriX. A sliding-thin-slab (STS) averaging algorithm was applied to each axial and each reformatted dataset with an increasing slab thickness from 1 to 20 slices. The low-contrast performance of all datasets was calculated semiautomatically using a reader-independent, statistical approach and is expressed as the visibility index. The results were analyzed for differences between the coronal reformations and the original axial datasets. In addition, the statistical approach used herein was validated against a reader study.

Results: : The visibility index of the coronal reformatted datasets over all lesion sizes was inferior when compared with the original axial datasets and reached 75.4% (±11.7%), 79.9% (±16.3%), 79.4% (±5.5%), and 93.7% (±14.6%) for dose levels of 25, 50, 100, and 200 mAs, respectively. The overall mean low-contrast performance was 82.1% of the axial dataset (P < 0.05, except for 200 mAs). The deterioration of low-contrast performance was inversely correlated with lesion size (R = 0.91). The use of the STS averaging algorithm significantly improved image quality for all datasets (112.6%-180.2%) with the beneficial effect being stronger for the coronal reformations. There was no statistically significant difference in the evaluation of low-contrast performance between the statistical approach and the ready study.

Conclusion: : Coronal reformations of thin-collimated multidetector computed tomography datasets show a significant reduction of low-contrast performance when compared with the original axial dataset, especially in high noise data. The use of an STS averaging algorithm had a significant benefit for both, coronal and axial orientations. The effect was more pronounced with coronal reformations and should be routinely applied to improve image quality.
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October 2011

F-18 2-fluoro-2-deoxy-glucose positron emission tomography/computed tomography for the detection of radicular and peripheral neurolymphomatosis: correlation with magnetic resonance imaging and ultrasound.

Clin Nucl Med 2009 Aug;34(8):493-5

Department of Radiology, Hannover Medical School, Germany.

Neurolymphomatosis is an uncommon extranodal manifestation of non-Hodgkin lymphoma. It may mimic a broad variety of neurologic conditions which renders clinical diagnosis challenging. As blind nerve biopsy is invasive and may be false negative, surrogate criteria for the diagnosis of neurolymphomatosis have been proposed based on magnetic resonance imaging/computed tomography findings. However, these morphologic modalities may suffer from limited sensitivity. Recently, a few reports have been published that discuss a possible advantage of F-18 2-fluoro-2-deoxy-glucose positron emission tomography/computed tomography (F-18 FDG PET/CT) in these patients.We report the case of a 41-year-old man who presented with progressive tetraparesis and dysaesthesia, in which F-18 FDG PET/CT aided to the diagnosis of neurolymphomatosis due to a large B-cell lymphoma. The patient received chemotherapy (R-CHOP) and the neurologic symptoms were clearly regressive. Three months after the end of systemic chemotherapy the patient presented again with progressive neurologic symptoms. A second PET/CT was performed and demonstrated disease recurrence in the right testis as well as widespread neurolymphomatosis. Additional ultrasound and magnetic resonance imaging examinations were performed and confirmed infiltration of the left brachial plexus, the right femoral, and the right sciatic nerve.We present this case to support the hypothesis that F-18 FDG PET/CT is a valuable imaging modality in patients with suspected neurolymphomatosis. It allows one to accurately determine the extent of the disease in a single whole-body examination.
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August 2009
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