Publications by authors named "Thorsten Fleiter"

25 Publications

  • Page 1 of 1

A 3-D-Printed Patient-Specific Ultrasound Phantom for FAST Scan.

Ultrasound Med Biol 2021 Mar 14;47(3):820-832. Epub 2020 Dec 14.

Department of Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland, USA.

Ultrasound phantoms are commonly used to assess the performance of ultrasound systems and ensure their proper functionality, in addition to providing opportunities for medical training. However, Focused Assessment with Sonography for Trauma (FAST) phantoms, in particular, are prohibitively expensive and procedure specific. This work explores the use of additive manufacturing to fabricate a patient-specific, full-scale torso ultrasound phantom. Phantom geometry was derived from anonymized computed tomography scans and segments into discrete organs. The digital organs (torso, skeleton, liver, spleen) were 3-D printed and used as castable molds for producing their respective body features. These organs were integrated with artificial hemorrhages to produce a realistic training tool for FAST scans. The resulting phantom is low in cost, has a verified shelf-life of at least 1 y and was positively reviewed by a trauma and emergency radiologist for its ability to provide accurate geometric and ultrasound information.
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http://dx.doi.org/10.1016/j.ultrasmedbio.2020.11.004DOI Listing
March 2021

Iodine-based Dual-Energy CT of Traumatic Hemorrhagic Contusions: Relationship to In-Hospital Mortality and Short-term Outcome.

Radiology 2019 09 30;292(3):730-738. Epub 2019 Jul 30.

From the Departments of Diagnostic Radiology and Nuclear Medicine (U.K.B., K.S., D.D., T.P., G.L., T.R.F.), Neurosurgery (B.A., G.S., M.S.), Neurology, R. Adams Cowley Shock Trauma Center (Y.G.P.), Epidemiology and Public Health (Y.L.), University of Maryland School of Medicine, 22 S Greene St, Baltimore, MD 21201; and University of Maryland School of Medicine, Baltimore, Md (M.R., S.T.).

BackgroundTraumatic hemorrhagic contusions are associated with iodine leak; however, quantification of leakage and its importance to outcome is unclear.PurposeTo identify iodine-based dual-energy CT variables that correlate with in-hospital mortality and short-term outcomes for contusions at hospital discharge.Materials and MethodsIn this retrospective study, consecutive patients with contusions from May 2016 through January 2017 were analyzed. Two radiologists evaluated CT variables from unenhanced admission head CT and follow-up head dual-energy CT scans obtained after contrast material-enhanced whole-body CT. The outcomes evaluated were in-hospital mortality, Rancho Los Amigos scale (RLAS) score, and disability rating scale (DRS) score. Logistic regression and linear regression were used to develop prediction models for categorical and continuous outcomes, respectively.ResultsThe study included 65 patients (median age, 48 years; interquartile range, 25-65.5 years); 50 were men. Dual-energy CT variables that correlated with mortality, RLAS score, and DRS score were iodine concentration, pseudohematoma volume, iodine quantity in pseudohematoma, and iodine quantity in contusion. The single-energy CT variable that correlated with mortality, RLAS score, and DRS score was hematoma volume at follow-up CT. Multiple logistic regression analysis after inclusion of clinical variables identified two predictors that enabled determination of mortality: postresuscitation Glasgow coma scale (P-GCS) (adjusted odds ratio, 0.42; 95% confidence interval [CI]: 0.2, 0.86; = 0.01) and iodine quantity in pseudohematoma (adjusted odds ratio, 1.4 per milligram; 95% CI: 1.02 per milligram, 1.9 per milligram; = 0.03), with a mean area under the receiver operating characteristic curve of 0.96 ± 0.05 (standard error). For RLAS, the predictors were P-GCS (mean coefficient, 0.32 ± 0.06; < .001) and iodine quantity in contusion (mean coefficient, -0.04 per milligram ± 0.02; 0.01). Predictors for DRS were P-GCS (mean coefficient, -1.15 ± 0.27; < .001), age (mean coefficient, 0.13 per year ± 0.04; .002), and iodine quantity in contusion (mean coefficient, 0.19 per milligram ± 0.07; .02).ConclusionIodine-based dual-energy CT variables correlate with in-hospital mortality and short-term outcomes for contusions at hospital discharge.© RSNA, 2019See also the editorial by Talbott and Hess in this issue.
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http://dx.doi.org/10.1148/radiol.2019190078DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7705608PMC
September 2019

Dual-Energy Computed Tomography Imaging of Head: Virtual High-Energy Monochromatic (190 keV) Images Are More Reliable Than Standard 120 kV Images for Detecting Traumatic Intracranial Hemorrhages.

J Neurotrauma 2019 04 8;36(8):1375-1381. Epub 2019 Jan 8.

1 Department of Diagnostic Radiology and Nuclear Medicine, R. Adams Cowley Shock Trauma Center, University of Maryland School of Medicine, Baltimore, Maryland.

High-energy monochromatic (190 keV) images may be more reliable than standard 120 kV Images for detecting intracranial hemorrhages. We aimed to retrospectively compare virtual high monochromatic (190 keV) and standard 120 kV images from dual-energy computed tomography (CT; DECT) for the diagnosis of intracranial hemorrhages in traumatic brain injury (TBI). We analyzed admission CT studies in 100 trauma patients. Three radiologists independently reviewed four image sets: 120 kV and 190 keV (thin [1 mm] and thick [5 mm] section) images for the presence of various types of intracranial hemorrhages. The proportions of positive variables were compared and differences calculated by McNemar test and sensitivities determined by contingency tables. Randomly selected hemorrhagic lesions were analyzed for contrast index (CI). Thin-section 190 keV images were superior in the detection of subdural hematomas (SDH) (p < 0.0001), supratentorial contusions (p < 0.0001), and epidural hematomas (EDH) (p = 0.014), when compared with standard 120 kV images. However, 190 keV images were inferior to standard 120 kV images in diagnosis of subarachnoid hemorrhage (SAH) (thin-sections, p = 0.059; thick-sections, 0.0075). The 190 keV images yielded moderate increase in CI of contusions (Cohen's d > 0.53) and a large increase in CI of extra-axial hematomas (Cohen's d > 0.86). Our results indicate that virtual high monochromatic (190 keV, thin-section) images combined with standard 120 kV images may provide optimal diagnostic performance for evaluation of patients suspected of TBI.
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http://dx.doi.org/10.1089/neu.2018.5985DOI Listing
April 2019

Diagnostic accuracy of triple-contrast multi-detector computed tomography for detection of penetrating gastrointestinal injury: a prospective study.

Eur Radiol 2016 Nov 16;26(11):4107-4120. Epub 2016 Mar 16.

R. Adams Cowley Shock Trauma Center, University of Maryland School of Medicine, 22 S. Greene Street, Baltimore, MD, 21201, USA.

Purpose: Neither the performance of CT in diagnosing penetrating gastrointestinal injury nor its ability to discriminate patients requiring either observation or surgery has been determined.

Materials And Methods: This was a prospective, single-institutional observational study of patients with penetrating injury to the torso who underwent CT. Based on CT signs, reviewers determined the presence of a gastrointestinal injury and the need for surgery or observation. The primary outcome measures were operative findings and clinical follow-up. CT results were compared with the primary outcome measures.

Results: Of one hundred and seventy-one patients (72 gunshot wounds, 99 stab wounds; age range, 18-57 years; median age, 28 years) with penetrating torso trauma who underwent CT, 45 % were followed by an operation and 55 % by clinical follow up. Thirty-five patients had a gastrointestinal injury at surgery. The sensitivity, specificity, and accuracy of CT for diagnosing a gastrointestinal injury for all patients were each 91 %, and for predicting the need for surgery, they were 94 %, 93 %, 93 %, respectively. Among the 3 % of patients who failed observation, 1 % had a gastrointestinal injury.

Conclusion: CT is a useful technique to diagnose gastrointestinal injury following penetrating torso injury. CT can help discriminate patients requiring observation or surgery.

Key Points: • The most sensitive sign is wound tract extending up to gastrointestinal wall. • The most accurate sign is gastrointestinal wall thickening. • Triple-contrast CT is a useful technique to diagnose gastrointestinal injury. • Triple-contrast CT helps to discriminate patients requiring observation and surgery.
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http://dx.doi.org/10.1007/s00330-016-4260-3DOI Listing
November 2016

Vascular complications of penetrating brain injury: comparison of helical CT angiography and conventional angiography.

J Neurosurg 2014 Nov 29;121(5):1275-83. Epub 2014 Aug 29.

Departments of 1 Radiology and.

Object: The authors conducted a study to compare the sensitivity and specificity of helical CT angiography (CTA) and digital subtraction angiography (DSA) in detecting intracranial arterial injuries after penetrating traumatic brain injury (PTBI).

Methods: In a retrospective evaluation of 48 sets of angiograms from 45 consecutive patients with PTBI, 3 readers unaware of the DSA findings reviewed the CTA images to determine the presence or absence of arterial injuries. A fourth reader reviewed all the disagreements and decided among the 3 interpretations. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CTA were calculated on a per-injury basis and in a subpopulation of patients with traumatic intracranial aneurysms (TICAs).

Results: Sensitivity of CTA for detecting arterial injuries was 72.7% (95% CI 49.8%-89.3%); specificity, 93.5% (95% CI 78.6%-99.2%); PPV, 88.9% (95% CI 65.3%-98.6%); and NPV, 82.9% (95% CI 66.4%-93.4%). All 7 TICAs were correctly identified by CTA. Sensitivity, specificity, PPV, and NPV of CTA in detecting TICAs were 100%. To compare agreement with DSA, the standard of reference, confidence scores categorized as low, intermediate, and high probability yielded an overall effectiveness of 77.8% (95% CI 71.8%-82.9%).

Conclusions: Computed tomography angiography had limited overall sensitivity in detecting arterial injuries in patients with PTBI. However, it was accurate in identifying TICAs, a subgroup of injuries usually managed by either surgical or endovascular approaches, and non-TICA injuries involving the first-order branches of intracranial arteries.
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http://dx.doi.org/10.3171/2014.7.JNS132688DOI Listing
November 2014

Optimizing trauma multidetector CT protocol for blunt splenic injury: need for arterial and portal venous phase scans.

Radiology 2013 Jul 28;268(1):79-88. Epub 2013 Feb 28.

Department of Diagnostic Radiology, University of Maryland Medical Center, 22 S Greene St, Baltimore, MD 21201, USA.

Purpose: To retrospectively compare the diagnostic performance of arterial, portal venous, and dual-phase computed tomography (CT) for blunt traumatic splenic injury.

Materials And Methods: Informed consent was waived for this institutional review board-approved, HIPAA-compliant study. Retrospective record review identified 120 blunt trauma patients (87 male [72.5%] 33 female [27.5%]; age range, 18-94 years) who had undergone dual-phase abdominal CT within 5 years, including 30 without splenic injury, 30 with parenchymal injury only, 30 with splenic active bleeding, and 30 with intrasplenic pseudoaneurysm. Six radiologists each performed blinded review of 20 different cases, and scored the presence of pseudoaneurysm, active bleeding, parenchymal injury, and hematoma; 20 cases were interpreted by all radiologists. Data analysis included calculation of diagnostic performance measures with confidence intervals, areas under receiver operating characteristic curves, and interobserver agreement/variability.

Results: For intrasplenic pseudoaneurysm, arterial phase imaging was more sensitive (70% [21 of 30] vs 17% [five of 30]; P < .0002) and more accurate (87% [78 of 90] vs 72% [65 of 90]; P = .0165) than portal venous phase imaging. For active bleeding, arterial phase imaging was less sensitive (70% [21 of 30] vs 93% [28 of 30]; P = .0195) and less accurate (89% [80 of 90] vs 98% [88 of 90]; P = .0168) than portal venous phase imaging. For parenchymal injury, arterial phase CT was less sensitive (76% [68 of 90] vs 93% [84 of 90]; P = .001) and less accurate (81% [nine of 120] vs 95% [114 of 120]; P = .0008) than portal venous phase CT. For all injuries, dual-phase review was equivalent to or better than single-phase review.

Conclusion: For CT evaluation of blunt splenic injury, arterial phase is superior to portal venous phase imaging for pseudoaneurysm but inferior for active bleeding and parenchymal disruption; dual-phase CT provides optimal overall performance.
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http://dx.doi.org/10.1148/radiol.13121370DOI Listing
July 2013

Real-time CT-guided percutaneous placement of LV pacing leads.

JACC Cardiovasc Imaging 2013 Jan;6(1):96-104

Maryland Arrhythmia and Cardiology Imaging Group (MACIG), Division of Cardiology, University of Maryland, Baltimore, Maryland 21201, USA.

Objectives: The aim of this study was to assess the feasibility of real-time computed tomographic (CT) imaging to guide the percutaneous placement of left ventricular (LV) leads in an animal model.

Background: Cardiac resynchronization therapy has been shown to improve morbidity and mortality in patients with chronic heart failure. However, placement of the coronary sinus lead can be challenging and may require a more aggressive surgical approach.

Methods: Nine swine were placed in a real-time CT scanner to define the safest percutaneous access strategy. Under real-time CT guidance, a 3.5-F pacing lead was placed percutaneously in the anterolateral LV epicardium (n = 6 swine) or to the posterolateral wall after the creation of intentional left pneumothorax (n = 3 swine) in a tangential (n = 12) or perpendicular (n = 1) approach. Pacing parameters and CT images were assessed during 30-min follow-up. Necropsy findings were compared with real-time CT images.

Results: CT imaging successfully defined the safest percutaneous access route in all 13 lead placements and guided the therapeutic creation of pneumothoraces. Needle trajectory remained within 5 mm of the access route defined on CT imaging. LV lead placement under CT guidance was successful in all attempts within 19 ± 7 min. The mean pacing thresholds was 2.5 ± 1.5 V, the mean R wave amplitude was 11.2 ± 5.6 mV, and the mean impedance was 686 ± 103 Ω and remained unchanged after tangential placement during 30-min follow-up. Although no cardiac complications were observed with tangential lead placement (12 of 12), the perpendicular approach resulted in a pericardial effusion requiring pericardiocentesis. At necropsy, CT images correlated well with the in situ pathological results.

Conclusions: Percutaneous placement of LV pacing leads under CT guidance is feasible and might offer an alternative to more invasive surgical approaches in patients with complicated coronary sinus lead placement.
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http://dx.doi.org/10.1016/j.jcmg.2012.06.012DOI Listing
January 2013

Syntheses and characterization of lisinopril-coated gold nanoparticles as highly stable targeted CT contrast agents in cardiovascular diseases.

Langmuir 2012 Jul 5;28(28):10398-408. Epub 2012 Jul 5.

Lisinopril was used as the targeting moiety to prepare gold nanoparticle-based functional CT contrast agents. Pure lisinopril, thioctic acid-lisinopril conjugate, and reduced thioctic acid-lisinopril conjugate were used to obtain GNP-Lis, GNP-TA-Lis, and GNP-RTA-Lis, respectively, via ligand exchange reaction on citrate-coated gold nanoparticles (GNPs). These lisinopril-decorated GNPs were fully characterized, and their chemical stabilities in biological relevant media and in high salt concentration were compared. Their relative stabilities toward lyophilization and against cyanide-induced decomposition were also investigated. Because of their higher stability, GNP-TA-Lis were used to assess the targeting of angiotensin converting enzyme (ACE) using X-ray computed tomography (CT). The images obtained displayed high contrast in the region of the lungs and heart, clearly indicating the targeting of ACE, whose overexpression is associated with development of cardiac and pulmonary fibrosis. Thus, the new nanoprobes prepared here will serve as very useful tools for the monitoring of cardiovascular pathophysiologies using CT imaging.
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http://dx.doi.org/10.1021/la301694qDOI Listing
July 2012

Focal cystic high-attenuation lesions: characterization in renal phantom by using photon-counting spectral CT--improved differentiation of lesion composition.

Radiology 2010 Jan;254(1):270-6

Department of Radiology, Duke University Medical Center, Durham, NC, USA.

Purpose: To evaluate the capability of spectral computed tomography (CT) to improve the characterization of cystic high-attenuation lesions in a renal phantom and to test the hypothesis that spectral CT will improve the differentiation of cystic renal lesions with high protein content and those that have undergone hemorrhage or malignant contrast-enhancing transformation.

Materials And Methods: A renal phantom that contained cystic lesions grouped in nonenhancing cyst and hemorrhage series and an iodine-enhancing series was developed. Spectral CT is based on new detector designs that may possess energy-sensitive photon-counting abilities, thereby facilitating the assessment of quantitative information about the elemental and molecular composition of tissue or contrast materials. Imaging of the renal phantom was performed with a prototype scanner at 20 mAs and 70 keV, allowing characterization of x-ray photons at 25-34, 34-39, 39-44, 44-49, 49-55, and more than 55 keV. Region of interest analysis was used to determine lesion attenuation values at various x-ray energies. Statistical analysis was performed to assess attenuation patterns and identify distinct levels of attenuation on the basis of curve regression analysis with analysis of variance tables.

Results: Spectral CT depicted linear clusters for the cyst (P < .001, R(2) > 0.940) and hemorrhage (P < .001, R(2) > 0.962) series without spectral overlap. A distinct linear attenuation profile without spectral overlap was also detected for the iodine-enhancing series (P < .001, R(2) > 0.964), with attenuation values attained in the 34-39-keV energy bin statistically identified as outliers (mean slope variation, >37%), corresponding with iodine k-edge effects at 33.2 keV.

Conclusion: Spectral CT has the potential to enable distinct characterization of hyperattenuating fluids in a renal phantom by helping identify proteinaceous and hemorrhagic lesions through assessment of their distinct levels of attenuation as well as by revealing iodine-containing lesions through analysis of their specific k-edge discontinuities.
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http://dx.doi.org/10.1148/radiol.09090068DOI Listing
January 2010

MDCT diagnosis of penetrating diaphragm injury.

Eur Radiol 2009 Aug 31;19(8):1875-81. Epub 2009 Mar 31.

Department of Diagnostic Radiology, University of Maryland School of Medicine, 22 S Greene St., Baltimore, MD 21201, USA.

The purpose of the study was to determine the diagnostic sensitivity and specificity of multidetector CT (MDCT) in detection of diaphragmatic injury following penetrating trauma. Chest and abdominal CT examinations performed preoperatively in 136 patients after penetrating trauma to the torso with injury trajectory in close proximity to the diaphragm were reviewed by radiologists unaware of surgical findings. Signs associated with diaphragmatic injuries in penetrating trauma were noted. These signs were correlated with surgical diagnoses, and their sensitivity and specificity in assisting the diagnosis were calculated. CT confirmed diaphragmatic injury in 41 of 47 injuries (sensitivity, 87.2%), and an intact diaphragm in 71 of 98 patients (specificity, 72.4%). The overall accuracy of MDCT was 77%. The most accurate sign helping the diagnosis was contiguous injury on either side of the diaphragm in single-entry penetrating trauma (sensitivity, 88%; specificity, 82%). Thus MDCT has high sensitivity and good specificity in detecting penetrating diaphragmatic injuries.
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http://dx.doi.org/10.1007/s00330-009-1367-9DOI Listing
August 2009

Calcified vascular plaque specimens: assessment with cardiac dual-energy multidetector CT in anthropomorphically moving heart phantom.

Radiology 2008 Oct 18;249(1):119-26. Epub 2008 Aug 18.

Department of Radiology, Duke University Medical Center, DUMC 3808, Durham, NC 27710, USA.

Purpose: To evaluate whether dual-energy multidetector computed tomography (CT) with image postprocessing techniques enhances accuracy of calcified plaque quantification beyond the scope of single-energy multidetector CT, by using optical coherence tomography (OCT) as the reference standard.

Materials And Methods: Four atherosclerotic specimens were examined with 64-section dual-energy multidetector CT by using a novel dual-detector "double-decker" design, with stacked high- and low-energy detector arrays with 32 x 0.625-mm collimation, at 140 kVp and 400 mAs, acquiring simultaneous and isopedic low- and high-energy data sets. Additionally, combined-energy data sets were calculated, and an enhancement algorithm was proposed. Cardiac motion was simulated by an anthropomorphically moving phantom, and OCT was used as a reference standard for plaque quantification. Univariate general linear model (GLM) analysis was used to compare sizes of plaque calcifications determined with OCT with those determined with dual-energy multidetector CT, and the significance of factors such as cardiac motion was assessed.

Results: GLM analysis revealed that plaque quantification based on low-, high-, and combined-energy data sets differed significantly from that based on OCT (P < .001). Greater data variation occurred in smaller (<8 mm(2)) and larger (>12 mm(2)) calcifications. Comparison of calcified plaque sizes determined with OCT with those determined with the dual-energy multidetector CT enhancement algorithm revealed no significant difference (P = .550). Cardiac activity led to a slight increase in data variation in regard to OCT for corresponding static (mean, 10.2% +/- 3.2 [standard deviation]) and dynamic (13.8% +/- 4.9) dual-energy multidetector CT data sets.

Conclusion: Dual-energy multidetector CT with novel postprocessing techniques enhanced accuracy of calcified plaque quantification by reducing effects of tissue blooming and beam hardening beyond single-energy multidetector CT.
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http://dx.doi.org/10.1148/radiol.2483071576DOI Listing
October 2008

Coronary stent patency: dual-energy multidetector CT assessment in a pilot study with anthropomorphic phantom.

Radiology 2008 Jun 18;247(3):687-95. Epub 2008 Apr 18.

Department of Radiology, Duke University Medical Center, DUMC 3808, Durham, NC 27710, USA.

Purpose: To prospectively evaluate, by optimizing image acquisition and introducing alternative image postprocessing techniques, dual-energy multidetector computed tomography (CT) for depiction of the lumens of coronary artery stents placed in a moving anthropomorphic heart phantom.

Materials And Methods: Four coronary stents (2, 3, 4, and 5 mm) were examined at 64-section dual-energy multidetector CT by using a dual-detector "double-decker" imager with stacked high- and low-energy detector arrays, 0.67-mm section thickness, and 32 x 0.625-mm collimation. Simultaneous high- and low-energy data sets were acquired at 80 and 140 kVp and at 400 mAs. Cardiac motion was simulated in a moving anthropomorphic heart phantom. Stents were imaged longitudinally and axially with the phantom at rest and with it in motion. Use of an enhancement algorithm based on high- and low-energy absorption profiles was proposed. Stent lumen depiction and stent mesh delineation were quantified in terms of contrast-to-noise ratio (CNR) and kurtosis (kappa), respectively. Image quality was analyzed at univariate general linear model analysis in which peak voltage and data enhancement algorithm were dependent factors and stent orientation and cardiac motion were independent factors.

Results: Analysis of CNR and kappa revealed an interdependency between CNR and kappa and stent diameter: The CNR and kappa of smaller stents increased significantly when these stents were imaged at lower peak voltages in the axial plane and with the enhancement algorithm applied to the 80-kVp data sets (P < .001). The CNR and kappa of larger stents increased significantly when these stents were imaged at higher peak voltages in the longitudinal plane, and imaging of these stents benefited from the enhancement algorithm being applied to the 140-kVp data sets (P < .001).

Conclusion: Dual-energy multidetector CT performed with optimized acquisition parameters and alternative image postprocessing led to enhanced coronary stent lumen depiction to an extent beyond that achieved with single-energy multidetector CT.
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http://dx.doi.org/10.1148/radiol.2473070849DOI Listing
June 2008

The role of 3D-CTA in the assessment of peripheral vascular lesions in trauma patients.

Eur J Radiol 2007 Oct 14;64(1):92-102. Epub 2007 Sep 14.

Department of Diagnostic Imaging, Section of Trauma and Emergency Radiology, University of Maryland School of Medicine, S. Greene Street, Baltimore, MD 21201, United States.

Purpose: The goal of any imaging in the setting of a level 1 trauma center is to assess the injuries of a patient as fast as possible with the least amount of time spend to move the patients between rooms or scanners in order to reduce the time till final diagnosis. CT-angiography (CTA) has become increasingly used to analyze peripheral vascular lesions in blunt and penetrating trauma.

Methods: Diagnostic angiography and CTA are competing methods for the display of peripheral vascular lesions. The specific advantages and shortcomings of both techniques for the routine use in a trauma center are discussed.

Results: The inherent limitations of the spatial and temporal resolution of a CTA are compensated by the availability of the procedure and reduced time needed for the final diagnosis.

Conclusion: 3D-CTA with multislice CT (MSCT) can be used to replace the diagnostic angiography in patients with blunt or penetrating extremity injuries.
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http://dx.doi.org/10.1016/j.ejrad.2007.07.018DOI Listing
October 2007

Spectral coronary multidetector computed tomography angiography: dual benefit by facilitating plaque characterization and enhancing lumen depiction.

J Comput Assist Tomogr 2006 Sep-Oct;30(5):804-11

Department of Radiology, University Hospitals of Ulm, University of Ulm, Ulm, Germany.

Objective: To assess ex vivo specimens of atherosclerotic coronary arteries by dual energy (DE) multidetector computed tomography (MDCT) imaging, and to correlate depicted vessel lumen morphology and detected tissue characteristics with histopathologic analysis.

Methods: Coronary arteries were imaged on a 16-slice MDCT using a DE protocol consisting of a 90- and 140-kV scan. Coronary arteries were perfused with iodine- and gadolinium-based contrast agents. The DE K-edge subtractions were performed. Regions-of-interest were placed on histopathologically/radiographically-matched vascular lumen and wall, fibromuscular and calcified plaque, and fat tissues. Vascular/tissue contrast-to-noise ratios (CNR) were calculated, and their dependence on tissue type and contrast agent type was statistically evaluated.

Results: Tissue CNR analysis confirmed that all tissue types were successfully distinguished. Vascular wall and fibromuscular plaque achieved a significant increase in CNR ratios when DE techniques were used compared with 140 kV protocols.

Conclusions: Spectral DE MDCT imaging of ex vivo atherosclerotic coronary arteries allows successful tissue characterization and enhances depiction of coronary lumen.
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http://dx.doi.org/10.1097/01.rct.0000228162.70849.26DOI Listing
October 2006

Qualitative and quantitative accuracy of CAOS in a standardized in vitro spine model.

Clin Orthop Relat Res 2006 Sep;450:118-28

Department of Trauma Surgery, Hand, Plastic, and Reconstructive Surgery, University of Ulm, Steinhövelstrasse 9, D-89075 Ulm, Germany.

Pedicle breach with screw implantation is relatively common. For clinical application of computer-assisted orthopaedic surgery, it is important to quantitatively know the accuracy and localization of any guidance modality. We ascertained the accuracy of computed tomography and C-arm-based navigated drilling versus conventional fluoroscopy using an artificial thoracic and lumbar spine model. The 3.2-mm diameter transpedicle drilling target was the center of a 4-mm steel ball fixed in the anterior left pedicle axis. After drilling, we used computed tomography to verify the position of the steel ball and the canal and visually explored for cortex perforation. Quantitative vector calculation showed computed tomography-based navigation had the greatest accuracy (median, d(thoracic) = 1.4 mm; median, d(lumbar) = 1.8 mm) followed by C-arm navigation (median, d(thoracic) = 2.6 mm; median, d(lumbar) = 2 mm) and the conventional procedure (median, d(thoracic) = 2.2 mm; median, d(lumbar) = 2.7 mm). Visual examination showed a decreased perforation rate in navigated drillings. We found no correlation between pedicle breaches and inaccurate drilling. The data suggest computer-assisted orthopaedic surgery cannot provide sub-millimeter accuracy, and complete prevention of pedicle perforation is not realistic.
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http://dx.doi.org/10.1097/01.blo.0000218731.36967.e8DOI Listing
September 2006

CT colonography: comparison of a colon dissection display versus 3D endoluminal view for the detection of polyps.

Eur Radiol 2006 Jan 14;16(1):68-72. Epub 2005 Jun 14.

Department for Diagnostic Radiology, University Hospital of Ulm, Steinhoevelstr. 9, 89075, Ulm, Germany.

The purpose of this study was to compare sensitivity, specificity, and postprocessing time of a colon dissection approach to regular 3D-endoluminal workup of computed tomography (CT) colonography for the detection of polypoid lesions. Twenty-one patients who had received conventional colonoscopy after CT colonography were selected; 18 patients had either colon polyps or colon cancer and three had no findings. CT colonography was performed using a 4-channel multi-detector-row (MDR) CT in ten cases and a 16-channel MDR-CT in 11 cases. A blinded reader retrospectively evaluated all colonographies using both viewing methods in a randomized order. Thirty-seven polyps were identified by optical colonoscopy. An overall per-lesion sensitivity of 47.1% for lesions smaller than 5 mm, 56.3% for lesions between 5 mm and 10 mm, and 75.0% for lesion larger than 10 mm was calculated using the colon dissection approach. This compared to an overall per-lesion sensitivity of 35.3% (<5 mm), 81.5% (5-10 mm), and 100.0% (>10 mm) using the endoluminal view. The average time consumption for CT colonography evaluation with the colon dissection software was 10 min versus 38 min using the endoluminal view. A colon dissection approach may provide a significant time advantage for evaluation of CT colonography while obtaining a high sensitivity. It is especially superior in the detection of lesions smaller than 5 mm.
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http://dx.doi.org/10.1007/s00330-005-2805-yDOI Listing
January 2006

Multi-detector row CT: is prospective electrocardiographic triggering improving the detection of small pulmonary tumors?

Acad Radiol 2005 May;12(5):614-9

Department of Diagnostic Radiology, University of Ulm, Steinhoevelstr. 9, 89075 Ulm, Germany.

Rationale And Objectives: To compare prospectively ECG-triggered multi-detector row computed tomography (ECG-MDR-CT) and multi-detector row computed tomography (MDR-CT) without triggering for the detection of pulmonary tumors.

Materials And Methods: 100 patients with proven or suspected tumors were referred for CT of the lung for staging of lung metastases. First, a non-enhanced scan was performed using prospective ECG-triggering on a four-row multidetector helical CT scanner, followed by a contrast-enhanced scan without triggering. The diagnostic assessibility in detecting intrapulmonary nodules and mediastinal structures was graded using a 5-point scale (rated 1 = bad to 5 = very good image quality).

Results: ECG-MDR-CT images detected a total of 26% more pulmonary nodules than MDR-CT. For tumors <5 mm, the detection rate was 62% higher using ECG-triggered scans (P = .024). Subjective assessment found median demarcation ratings for all pulmonary findings of 4 (ECG-MDR-CT) versus 3 (MDR-CT). Mediastinal structures were delineated better using ECG triggering. The median ranking for demarcation of pulmonary findings <10 mm was 4 on ECG-MDR-CT and 3 on MDR-CT, respectively. For vessels and the left bronchus, the median of demarcation was 4 on triggered images and 2 on MDR-CT, respectively. The median values referring to the demarcation of mediastinal structures were not significantly different between ECG-MDR-CT and MDR-CT.

Conclusion: Our data indicate the superiority of prospectively triggered ECG-MDR-CT over MDR-CT for the diagnosis of small pulmonary tumors using a 4-row multidetector CT.
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http://dx.doi.org/10.1016/j.acra.2005.02.004DOI Listing
May 2005

Functional cardiac CT and MR: effects of heart rate and software applications on measurement validity.

J Thorac Imaging 2005 Feb;20(1):10-6

Department of Radiology, University Hospitals of Cleveland, Case Western Reserve University, Cleveland, Ohio 44106-5056, USA.

This study sought to validate different software applications for cardiac function analysis using ECG-gated CT and MR datasets in correlation with underlying heart rate. Ten patients and a set of ventricular phantoms underwent concurrent multislice-CT and cine-MR imaging for evaluation of cardiac function. Datasets from both imaging modalities were evaluated utilizing 2 volumetric analysis tools to determine left ventricular volume and mass. Initially, intraobserver measurement variability was assessed. Detected measurement variability was correlated with underlying absolute magnitude of cardiac volumes and masses. Subsequently, results were statistically evaluated by determining significant data variability depending on imaging modality and choice of evaluation software. Finally, the data variability was correlated with underlying heart rates. This study showed that all analyzed datasets uniformly presented intraobserver variations below 2%, and variability was not related to the magnitude of measurement. Significant measurement accuracy was proven in all calculated parameters obtained from the cardiac phantoms. Acquired patient datasets and calculated functional parameters showed significant data homogeneity, with measurement variability coefficients ranging from 0.935-0.955. CT datasets showed maximal data variability at heart rates below 60 BpM. MR datasets showed maximal data variability at heart rates above 90 BpM. In conclusion, CT and MR datasets allowed an interchangeable utilization of volumetric analysis tools. However, reliable volumetric analysis was limited to an optimal range of cardiac rates for each modality, thus emphasizing the necessity of reporting volumetric measurement results in combination with heart rate to allow for consideration of this possible cause for measurement variation.
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http://dx.doi.org/10.1097/01.rti.0000154077.13947.8eDOI Listing
February 2005

Volumetric assessment of pulmonary nodules with ECG-gated MDCT.

AJR Am J Roentgenol 2004 Nov;183(5):1217-23

Department of Radiology, University Hospitals of Cleveland, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106-5056, USA.

Objective: The objective of our study was to assess physiologic lung deformation and compression originating from cardiovascular motion and their subsequent impact on determining the volume of small pulmonary nodules throughout the cardiac cycle on ECG-gated MDCT.

Subjects And Methods: Seventy-three small noncalcified pulmonary nodules were identified in 30 patients who underwent ECG-gated MDCT. The volume of each nodule was assessed throughout the cardiac cycle using computer-aided automatic segmentation algorithms, and the assessment was repeated three times. To ensure the validity of the subtle changes in volume that were detected, we determined the volume and signal attenuation in phantom data sets and patient nodules without temporal or spatial differentiation. Subsequently, nodules were assigned to pulmonary segments, and volume changes were correlated to cardiac phases, nodular location, and mean nodular size. Statistical multivariate tests were performed to evaluate significant patterns.

Results: The validity of significant measurements was proven in evaluated phantom data sets with a general tendency toward overestimating nodular volume (p = 0.492). Statistical evaluation of nodular signal attenuation confirmed true deformation and compression of nodules rather than partial volume effects as the reason for volume variations (p = 0.874). Differentiating pulmonary nodules in cardiac phases, pulmonary locations, and mean nodular volumes, we found that one single effect did not determine the amount of cardiovascular motion conveyed to pulmonary parenchyma and subsequently led to nodule deformation. Multivariate testing revealed statistically significant measures identifying patterns correlating variation in nodular volume with cardiac phase (p < 0.001), nodular location (p = 0.007), and mean nodular size (p < 0.001).

Conclusion: Cardiovascular motion was disproportionately conveyed to various pulmonary segments and led to changes in the volume of pulmonary nodules, especially in small pulmonary nodules. A precise volumetric assessment was therefore possible only by identifying the underlying cardiac phase.
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http://dx.doi.org/10.2214/ajr.183.5.1831217DOI Listing
November 2004

Multidetector CT angiography of arterial inflow and runoff in the lower extremities: a challenge in data acquisition and evaluation.

J Endovasc Ther 2004 Apr;11(2):144-51

Department of Radiology, Case Western Reserve University, University Hospitals of Cleveland, 11100 Euclid Avenue, Cleveland, OH 4410-106, USA.

Purpose: To show the feasibility of acquiring homogenous 3-dimensional datasets with high temporal and spatial resolution from computed tomographic angiographic (CTA) scans of the lower extremities and to assess automated vessel-tracking techniques for vascular evaluation.

Methods: Eighteen men (mean age 67.0 years, range 43-83) with aneurysmal or occlusive vascular diseases underwent contrast-enhanced CTA of the lower limb arteries utilizing a 16-row CT imager. Curved multiplanar reformations were generated by manual selection of vessel centerlines in the infrarenal aorta and the arterial vasculature in the pelvis, thigh, and calf based on volume-rendering techniques. For each vessel, opacification and depiction were quantitatively evaluated. The manually segmented images were compared to datasets processed with automated vessel-tracking strategies by 5 radiologists, who evaluated diagnostic reliability and image quality. A Differential Receiver Operating Characteristic (DROC) analysis was performed.

Results: An increase in the temporal and spatial resolution led to acquisition of high quality CTA datasets. Significant homogeneity of the vascular contrast-to-noise ratios was achieved in the pelvic (coefficient of variance 1.5% to 10.1%), thigh (0.1% to 9.4%), and calf (3.3% to 19.2%) vessels. The assessment of vascular delineation revealed full-width-at-half-maximum contrast values of 96.4%, 95.5%, and 111.3% in the pelvis, thigh, and calf, respectively. Observers were not able to distinguish between manual and automated vascular segmentation, as represented by a 0.56 value for the area under the DROC curve.

Conclusions: High-resolution CTA lower extremity datasets were acquired successfully, presenting vascular signal intensities of high homogeneity suitable for automated vessel-tracking techniques. Automated 3D visualization tools produced reliable, reproducible, and time-efficient centerline extractions that were comparable to manually defined centerlines.
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http://dx.doi.org/10.1583/03-1098.1DOI Listing
April 2004

Multislice helical CT of the pancreas and spleen.

Eur J Radiol 2003 Mar;45 Suppl 1:S59-72

Department of Radiology, University of Ulm, Ulm, Germany.

Multislice helical CT (MSCT) with its multidetector technology and faster rotation times, has led to new dimensions in spatial and temporal resolution in CT imaging. In contrast to single-slice CT, smaller slice collimations can be applied that lead to almost isotropic voxels and allow high quality multiplanar and 3-D image reconstructions. The high speed of multislice CT can be used to reduce the time needed to cover a given volume, to increase the spatial resolution along the z-axis by applying thinner slice collimations, and to cover longer anatomic volumes. The speed of MSCT allows organ imaging in clearly defined perfusion phases, e.g. the arterial, parenchymal, and portal venous perfusion phases. Contrast agents with higher iodine concentrations (400 mg iodine per ml compared with 300 mg iodine per ml) lead to higher contrast enhancement of the pancreas (arterial+portal venous phases), the kidneys (arterial+portal venous phases), the spleen (arterial phase), the wall of the small intestine (arterial+portal venous phases), the larger and smaller arteries (arterial phase), and the portal vein (portal venous phase). All of these advancements lead to improved visualization of small structures and of various pathologies, such as pancreatic tumors, liver metastases, vessel infiltration, and vascular diseases.
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http://dx.doi.org/10.1016/s0720-048x(02)00363-7DOI Listing
March 2003

Interventional treatment of traumatic priapism.

J Endovasc Ther 2002 Oct;9(5):614-7

Department of Radiology, University of Ulm, Germany.

Purpose: To describe the effectiveness of transarterial embolization of traumatic priapism.

Methods: Six patients ranging in age from 6 to 37 years with traumatic high-flow priapism underwent superselective embolization with gelatin sponges (n=3) or minicoils (n=3). Embolization was repeated up to 3 times.

Results: Embolization was successful in all cases. In 2 patients, repeated embolization led to a flow reduction in the fistula, which spontaneously occluded a few days later. All patients experienced normal erections after intervention, and no side effects were observed.

Conclusions: Transarterial superselective embolization is an effective and well-tolerated therapy in patients with traumatic priapism.
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http://dx.doi.org/10.1177/152660280200900511DOI Listing
October 2002

Multislice helical CT of the abdomen.

Eur Radiol 2002 Jul;12 Suppl 2:S5-10

Department of Radiology, University of Ulm, Ulm, Germany.

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http://dx.doi.org/10.1007/s003300200001DOI Listing
July 2002

Magnetic resonance imaging versus multislice computed tomography of thoracic aortic endografts.

J Endovasc Ther 2002 Jun;9 Suppl 2:II2-13

Department of Radiology, University Hospitals of Ulm, Germany.

Purpose: To compare the potential of magnetic resonance imaging (MRI) to multislice computed tomography (CT) for evaluating stent-graft placement in the thoracic aorta.

Methods: Susceptibility artifacts in 2 different stent-graft systems (Talent and Excluder) were evaluated in vitro in 2 angulations (straight and 33 degrees curved) using 3 different MRI gradient echo sequences (True FISP, 2-dimensional FLASH, and 3-dimensional Turbo FLASH). The size of the stent-related artifact was measured, and the relative stent lumen was calculated. In vivo stent demarcation, stent patency, and additional findings were determined in 13 patients (3 Talent, 9 Excluder, and 1 combined) and compared to CT findings.

Results: In vitro, both endograft systems proved to be MR compatible, with the relative stent lumen value ranging from 82% to 100% in the straight configuration; in a curved model, the relative stent lumen value ranged from 56% to 92% with the 3D Turbo FLASH sequence, which provided the smallest susceptibility artifacts. The Excluder endoprosthesis caused significant signal inhomogeneity within the stent in a curved configuration. In vivo, MRI and multislice CT showed similar results, with CT imaging slightly superior in stent demarcation and MRI better in demonstrating thrombus. CT beam hardening artifacts were pronounced in the Talent system, while the Excluder device caused significant signal inhomogeneity within the stent on magnetic resonance angiography.

Conclusions: Multislice CT and contrast-enhanced MRI are fast, reliable means of providing all relevant information for surveillance of fully MR-compatible stent-grafts in the thoracic aorta.
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June 2002

Renal infarction following endovascular aortic aneurysm repair: incidence and clinical consequences.

J Endovasc Ther 2002 Feb;9(1):98-102

Department of Diagnostic Radiology, University Hospital of Ulm, Germany.

Purpose: To investigate the incidence of renal infarction following endovascular abdominal aortic aneurysm (AAA) repair, with particular emphasis on a comparison of suprarenal versus infrarenal endograft placement.

Methods: Ninety-nine patients (92 men; average age 68 years) who had undergone endovascular AAA repair between July 1995 and July 1999 and who had at least 12 months' follow-up were studied with spiral computed tomographic scans to identify suprarenal endograft deployment and renal infarction.

Results: Among the 193 renal arteries available for study, partial or complete transrenal endograft placement was found in 69 (36%). Sixteen (8.3%) renal infarctions were identified by the postoperative imaging studies. Perfusion of these kidneys was supplied by 6 (8.7%) of the 69 overstented renal arteries and 7 (5.6%) of the 124 uncovered arteries (p > 0.05). In the 3 other cases, intentional accessory renal artery occlusion by the stent-graft fabric led to frank segmental renal infarctions, which were visualized as territorial-perfusion defects affecting up to 27% of the renal volume. In the other 13 infarcted kidneys, the punctate deficits involved <10% of the parenchymal volume. Renal retention values were unaffected in 15 (94%) of 16 patients.

Conclusions: Documented renal infarctions following endovascular aortic stent-graft placement are not common and do not appear to be associated with suprarenal endograft fixation.
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http://dx.doi.org/10.1177/152660280200900116DOI Listing
February 2002