Publications by authors named "Ralph Gnannt"

25 Publications

  • Page 1 of 1

Laparoscopic Ureteroureterostomy vs. Common Sheath Ureteral Reimplantation in Children With Duplex Kidney Anomalies.

Front Pediatr 2021 18;9:637544. Epub 2021 Feb 18.

Division of Pediatric Urology, University Children's Hospital Zurich, Zurich, Switzerland.

Laparoscopic ureteroureterostomy (LUU) has been proposed as an alternative to common sheath ureteral reimplantation (CSUR) in children with symptomatic duplex kidneys. However, data is limited for LUU in the pediatric population. The aim of this study was to analyze our experience with LUU and to compare the results with those after CSUR to assess whether a less invasive surgical approach could be a valid alternative. The data of all children with duplex kidneys who underwent either LUU or CSUR at our center from 2006 to 2018 were reviewed retrospectively. After parental counseling, the option of LUU was provided as an alternative to CSUR for unilateral procedures and in the absence of vesicoureteral reflux to the receiving ureter. Baseline characteristics, indication for surgery, hospitalization and operative times, and intraoperative, post-operative, and late complications were analyzed. Preoperative and 1-year post-operative sonographies were reviewed by a pediatric radiologist. Increasing renal pelvic diameter (Δ >5 mm) was regarded as a sign of ureteral obstruction. Forty children were included in this study, with 16 children receiving LUU and 24 children receiving CSUR. The children had a mean age of 2.7 years (7 months-9.8 years) and were followed up in our outpatient clinic for an average of 3.9 years (3 months-10.6 years) after surgery. The median hospital stay was 2 days shorter after LUU. Initially, a considerably longer time was needed for LUU, but after more experience was gained, similar operative times were observed for both procedures. Complications were encountered in both groups. After LUU, two patients developed anastomotic leakage: one was managed conservatively, and one required temporary nephrostomy. In the CSUR group, one patient developed vesicoureteral obstruction during follow-up and required reoperation with LUU. The occurrence of post-operative urinary tract infections was similar in both groups. No complications related to the ureteral stump after LUU arose. LUU is a safe and efficacious treatment option for children with duplex kidney anomalies and can be used as an alternative to CSUR. All children receiving LUU showed a non-obstructive, patent anastomosis and no signs for stenotic compromise of the receiving ureter.
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February 2021

Hemodialysis Catheters in Infants: A Retrospective Single-Center Cohort Study.

J Vasc Interv Radiol 2020 05 15;31(5):778-786. Epub 2020 Apr 15.

Image Guided Therapy, Department of Medical Imaging, The Hospital for Sick Children, University of Toronto, 555 University Ave, Toronto, ON M5G 1X8, Canada.

Purpose: Evaluate technical aspects and outcomes of insertion/maintenance of hemodialysis (HD) central venous catheter (CVC) during infancy.

Materials And Methods: Single-center retrospective study of 29 infants who underwent 49 HD-CVC insertions between 2002 and 2016. Demographics, procedural, and post-procedural details, interventional radiology (IR) maintenance procedures, technical modifications, complications, and outcomes were evaluated. Technical adjustments during HD-CVC placement to adapt catheter length to patient size were labeled "modifications." CVCs requiring return visit to IR were called IR-maintenance procedures. Mean age and weight at HD-CVC insertion were 117 days and 4.9 kg.

Results: Of the 29 patients, 13 (45%) required renal-replacement-therapy (RRT) as neonates, 10 (34%) commenced RRT with peritoneal dialysis (PD), and 19 (66%) with HD. Fifteen nontunneled and 34 tunneled HD-CVCs were inserted while patients were ≤1 year. Technical modifications were required placing 25/49 (51%) HD-CVCs: 5/15 (33%) nontunneled and 20/34 (59%) tunneled catheters (P = .08). Patients underwent ≤6 dialysis-cycles/patient during infancy (mean 2.3), and a mean of 4.1 and 49 HD-sessions/catheter for nontunneled and tunneled HD-CVCs, respectively. Mean primary and secondary device service, and total access site intervals for tunneled HD-CVCs were 75, 115, and 201 days, respectively. A total of 26 of 49 (53%) patients required IR-maintenance procedures. Nontunneled lines had greater catheter-related bloodstream infections per 1,000 catheter-days than tunneled HD-CVCs (9.25 vs. 0.85/1,000 catheter days; P = .02). Nineteen patients (65%) survived over 1 year. At final evaluation (December 2017): 8/19 survived transplantation, 5/19 remained on RRT, 2/19 completely recovered, 1/19 lost to follow-up, and 3 died at 1.3, 2, and 10 years.

Conclusions: Placement/maintenance of HD-CVCs in infants pose specific challenges, requiring insertion modifications, and IR-maintenance procedures to maintain function.
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May 2020

MR Features of Juxta-Articular Venous Malformations of the Knee to Predict the Clinical Outcome of Sclerotherapy.

J Vasc Interv Radiol 2020 Apr 24;31(4):551-557. Epub 2019 Dec 24.

Department of Diagnostic and Interventional Radiology, University Hospital Zurich, Zurich, Switzerland.

Purpose: To analyze and correlate preinterventional magnetic resonance (MR) imaging findings with clinical symptoms after percutaneous sclerotherapy of venous malformations (VMs) adjacent to the knee.

Materials And Methods: Twenty-five patients (mean age, 24 y; range, 7-55 y; 11 female) with 26 VMs adjacent to the knee undergoing sclerotherapy (direct puncture, diagnostic angiography, sclerosant injection) were identified, and MR imaging findings were analyzed. The VM involved the synovium of the knee joint in 19 of 26 cases (76%). These lesions were associated with joint effusion (3 of 19; 16%), hemarthrosis (4 of 19; 21%), or synovial thickening (16 of 19; 84%). Follow-up ended 6-8 weeks after the first or second sclerotherapy session if complete pain relief was achieved or 3 months after the third sclerotherapy session. Treatment outcomes were categorized as symptom improvement (complete or partial pain relief) or poor response (unchanged or increased pain).

Results: Forty-nine percutaneous sclerotherapy sessions were performed. Despite the absence of signs of knee osteoarthritis, patients with a VM involving the synovium (8 of 14; 57%) showed a poor response to sclerotherapy (1 of 8 [13%] pain-free after 1 sclerotherapy session). Among patients with VMs with no associated joint alteration and no synovial involvement (6 of 14; 43%), 5 of 6 (83%) showed improvement of symptoms after 1 sclerotherapy session (P < .05).

Conclusions: Juxta-articular VMs of the knee are frequently associated with hemarthrosis and synovial thickening. Patients with signs of osteoarthritis and synovial involvement of the VM on presclerotherapy MR imaging deserve special consideration, as these findings predict worse clinical symptoms after sclerotherapy.
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April 2020

Lymphatische Malformationen.

Ralph Gnannt

Rofo 2019 Sep 20;191(S 02):S111-S112. Epub 2019 Aug 20.

Universitäts-Kinderspital Zürich.

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September 2019

Clinical Impact of Chronic Venous Changes Induced by Central Lines in Children: A Cohort with Abnormal Venograms.

J Vasc Interv Radiol 2019 May 27;30(5):715-723. Epub 2019 Mar 27.

Image Guided Therapy, Diagnostic Imaging, The Hospital for Sick Children, University of Toronto, 555 University Ave, Toronto, ON, M5G 1X8, Canada.

Purpose: To explore the hypothesis that central venous stenosis/obstructions (CVS/O) in children are influenced by prior central venous access devices (CVADs) and are associated with future risk for thromboses.

Material And Methods: A convenience sample of 100 patients with abnormal venography (stenosis, collaterals, occlusions) documented during peripherally inserted central catheter (PICC) placements were identified from consecutive PICC placements (January 2008 to November 2012). The patients (41 males, 59 females, median age 2.7 years, median weight 11 kg) were categorized based on venographic presence (Group A, n = 53) or absence (Group B, n = 47) of visible connection to the superior vena cava. Each patient's CVAD history, before and after venography, was analyzed (until October 2016).

Results: Before venogram, Group B patients were associated with a higher number of previous CVADs, larger diameter devices, greater incidence of malposition, and more use of polyurethane catheters than Group A patients (P < .001). An ipsilateral PICC was successfully placed in 98% of Group A, compared to 32% of Group B (P < .001). After venogram, significantly more Doppler ultrasounds (DUS) were performed and thromboses diagnosed in Group B (57% and 36%) compared to Group A (21% and 8%) (P < .003; P = .001), respectively.

Conclusions: Previous catheter characteristics influenced the severity of venographic changes of CVS/O (Group B). Group B was associated with more subsequent symptomatic thromboses. This information may assist parents and referring physicians to anticipate potential adverse sequelae from CVS/O on the child's venous health.
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May 2019

Non-vascular interventional radiology in the paediatric alimentary tract.

Eur J Radiol 2019 Mar 13;112:72-81. Epub 2018 Dec 13.

Bilddiagnostik, Paediatric Interventional Radiology, University Children's Hospital, Steinwiesstrasse 75, CH-8032, Zürich, Switzerland.

Paediatric interventional radiology is an evolving speciality which is able to offer numerous minimally invasive treatments for gastrointestinal tract pathologies. Here we describe interventions performed by paediatric interventional radiologists on the alimentary tract from the mouth to the rectum. The interventions include sclerotherapy, stricture management by dilation, stenting and adjunctive therapies such as Mitomycin C administration and enteral access for feeding, motility assessment and administration of enemas.
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March 2019

Increased risk of symptomatic upper-extremity venous thrombosis with multiple peripherally inserted central catheter insertions in pediatric patients.

Pediatr Radiol 2018 07 27;48(7):1013-1020. Epub 2018 Feb 27.

Image Guided Therapy, Diagnostic Imaging, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada.

Background: Peripherally inserted central catheters (PICCs) are associated with superficial and deep venous thrombosis of the arm.

Objective: The purpose of this study was to analyze the sequelae of repeated upper limb PICC insertions in children, in terms of the frequency of upper limb thrombosis in this patient group.

Materials And Methods: The study population included all children who underwent their first successful arm PICC insertion between January 2010 and December 2015. We included subsequent ipsilateral arm PICCs in the analysis. Patients were followed until March 2016 or until any alternative central venous line insertion. For each PICC insertion, we collected demographic variables and line characteristics. We correlated all symptomatic deep and superficial thromboses of the arm with the PICC database.

Results: Applying inclusion and exclusion criteria, 2,180 PICCs remained for analysis. We identified first, second, third and fourth PICC insertions in the same arm in 1,955, 181, 38 and 6 patients, respectively. In total there were 57 upper body deep symptomatic thrombotic events. An increasing odds ratio was seen with higher numbers of PICC insertions, which was significant when comparing the first with the third and fourth PICC insertions in the same arm (odds ratio [OR] 6.00, 95% confidence interval [CI] 2.25-16.04, P=0.0004). Double-lumen PICCs were associated with a significantly higher risk of thrombosis than single lumen (OR 2.77, 95% CI 1.72-4.47, P=0.0003).

Conclusion: Repetitive PICC insertions in the same arm are associated with an increased risk of symptomatic thrombosis. Double-lumen PICCs are associated with a higher risk of thrombosis compared to single-lumen lines.
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July 2018

Structural and perfusion magnetic resonance imaging of the lung in cystic fibrosis.

Pediatr Radiol 2018 02 15;48(2):165-175. Epub 2017 Nov 15.

Department of Diagnostic Imaging, University Children's Hospital Zürich, Steinwiesstr. 75, 8032, Zürich, CH, Switzerland.

Background: Because of its absence of ionising radiation and possibility for obtaining functional information, MRI is promising for assessing lung disease in children who require repetitive imaging for long-term follow-up.

Objective: To describe MRI findings in children with cystic fibrosis and evaluate semi-quantitative dynamic contrast-enhanced lung perfusion.

Materials And Methods: We retrospectively compared lung MRI in 25 children and young adults with cystic fibrosis (median age 3.7 years) to 12 children (median age 2 years) imaged for other pathologies. MRI at 1.5 T included respiratory-gated sequences and contrast-enhanced lung perfusion imaging. We described and graded any morphologic change. Signal enhancement and time to peak values of perfusion abnormalities were compared to those of normally enhancing lung parenchyma.

Results: Frequent findings in patients with cystic fibrosis were bronchial wall thickening (24/25, 96%), areas of consolidation (22/25, 88%), enlarged lymph nodes (20/25, 80%), bronchiectasis (5/25, 20%) and mucus plugging (3/25, 12%). Compared to normally enhancing lung, perfusion defects (21/25, 84%), characterised by decreased enhancement, showed prolonged time to peak. Areas of consolidation showed increased enhancement. While time to peak of procedure-related atelectasis was not significantly different from that of normal lung, disease-related consolidation showed prolonged time to peak (P=0.01).

Conclusion: Lung MRI demonstrates structural and perfusion abnormalities in children and young people with cystic fibrosis. Semi-quantitative assessment of dynamic contrast-enhanced perfusion imaging might allow differentiation between procedure-related atelectasis and disease-related consolidation.
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February 2018

Technique, Safety, and Yield of Bone Biopsies for Histomorphometry in Children.

J Vasc Interv Radiol 2017 Nov 18;28(11):1577-1583. Epub 2017 Aug 18.

Division of Image Guided Therapy, Diagnostic Imaging, Department of Medical Imaging, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON M5G 1X8 Canada.

Purpose: To evaluate image-guided bone biopsy for bone histomorphometry to assess osteoporosis in children with respect to safety and yield.

Materials And Methods: A single-center retrospective review was performed of 79 bone biopsies in 73 patients performed between 2007 and 2015. Biopsies of the iliac bone were performed under general anesthesia, after tetracycline labeling, using a Rochester needle (Medical Innovations International, Inc, Rochester, Minnesota). Ultrasound and fluoroscopic guidance were used in all procedures. Biopsy technique, technical success, safety, and histomorphometry results (complete, incomplete, none) were analyzed.

Results: There were 41 male patients (51.8%). Technical success was achieved in 76/79 (96%) procedures. Of 79 biopsies, 75 (95%) were uneventful. Unplanned overnight observation was required in 3 (minor SIR grade B), and prolonged hospital stay owing to hematoma causing nerve compression pain was required in 1 (major SIR grade D). Complete histomorphometric reports were obtained in 69 (87%) procedures, incomplete reports were obtained in 7 (9%), and no reports were obtained in 3(4%). Incomplete reports were insufficient to provide a definitive diagnosis or guide treatment. Histomorphometry impacted subsequent therapy in 69 (87%) biopsies.

Conclusions: Image-guided bone biopsy for osteoporosis using the Rochester needle is a valuable and safe technique for establishing the diagnosis of osteoporosis and directing treatment based on histomorphometry results.
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November 2017

Peripherally Inserted Central Catheters in Pediatric Patients: To Repair or Not Repair.

Cardiovasc Intervent Radiol 2017 Jun 30;40(6):845-851. Epub 2017 Jan 30.

Image Guided Therapy, Diagnostic Imaging, The Hospital for Sick Children, University of Toronto, 555 University Avenue Toronto, Toronto, ON, M5G 1X8, Canada.

Introduction: Preservation of venous access in children is a major concern in pediatric interventional radiology. If a peripherally inserted central catheter (PICC) breaks, there are two options: repair the line with a repair kit or exchange the line over a wire in the interventional suite. The purpose of this study is to assess the outcome of PICC repairs in children and to compare these with the outcomes of PICC exchange.

Materials And Methods: This is a single-center, retrospective study of central line-associated bloodstream infection (CLABSI) following management of externally broken PICCs (2010-2014). The occurrence of CLABSI within 30 days after repair (Group A) or exchange (Group B) of a line was analyzed, as well as PICCs exchanged following an initial and failed repair.

Results: A total of 235 PICC breaks were included in the study, of which 161 were repaired, and 116 of whom were successful (68%, Group A). No repair was performed in 74 PICCs-55/74 of these were exchanged over a wire (74%, Group B), and 19/74 lines were removed. The 30 days post-repair CLABSI rate (Group A) was 2.0 infections per 1000 catheter days, and the calculated risk was 4.3%. In comparison the 30 days post-exchange CLABSI rate (Group B) was 4.0 per 1000 catheter days and the calculated risk 10.9%. This difference was significant when adjusted for antibiotic use (OR 3.87; 95% CI 1.07-14.0, p = 0.039).

Conclusion: The results of this study support repairing a broken PICC instead of removing or replacing the line.
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June 2017

Variables decreasing tip movement of peripherally inserted central catheters in pediatric patients.

Pediatr Radiol 2016 Oct 7;46(11):1532-8. Epub 2016 Jun 7.

Image Guided Therapy, Diagnostic Imaging, The Hospital for Sick Children, University of Toronto, 555 University Ave., Toronto, ON, M5G 1X8, Canada.

Background: The position of the tip of a peripherally inserted central catheter (PICC) is crucial; malposition can lead to malfunction of the line or life-threatening events (e.g., arrhythmias, perforation).

Objective: To determine what factors other than arm position and accessed vein might influence the tip position of a PICC.

Materials And Methods: Inclusion criteria were upper limb PICC placement, body weight <20 kg, intraoperative imaging with the arm in 0°, 45° and 90° abduction and an arm view marking the skin entry site relative to the shoulder. Evaluated variables included patient demographics, and PICC and insertion site characteristics. We measured central tip movement in rib units.

Results: We included 112 children who received a PICC (42 girls/70 boys, mean age 31±13 months, mean weight 6.5±4.9 kg). The overall range of central tip movement was -1 to +4 rib units (mean +0.8±0.7 rib units). Silicone PICCs moved significantly less than polyurethane PICCs (P<0.05). PICCs placed in the cephalic vein moved significantly less than those placed in other veins (P<0.05). Patient demographics and PICC characteristics (size, number of lumens, left or right arm accessed, length of the line) did not influence the range of central tip movement of a PICC (P>0.05).

Conclusion: Silicone PICCs and PICCs inserted into the cephalic vein move less than PICCs made of polyurethane and PICCs inserted into the brachial and basilic veins. These findings might assist operators in deciding which PICC to place in children in a given clinical context.
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October 2016

Transvenous Embolization of an Acquired Arteriovenous Malformation of the Arm.

J Vasc Interv Radiol 2015 Oct;26(10):1585-7

Institute of Diagnostic and Interventional Radiology, UniversitätsSpital Zürich, Rämistrasse 100, 8091 Zürich, Switzerland.

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October 2015

Distinguishing infected from noninfected abdominal fluid collections after surgery: an imaging, clinical, and laboratory-based scoring system.

Invest Radiol 2015 Jan;50(1):17-23

From the *Institute of Diagnostic and Interventional Radiology, and †Department of Surgery, Swiss Hepato-Pancreato-Biliary and Transplantation Center, University Hospital Zurich; and ‡Division of Biostatistics, Institute of Social and Preventive Medicine, University of Zurich, Zurich, Switzerland.

Objectives: Mortality from abdominal abscesses ranges from 30% in treated cases up to 80% to 100% in patients with undrained or nonoperated abscesses. Various computed tomographic (CT) imaging features have been suggested to indicate infection of postoperative abdominal fluid collections; however, features are nonspecific and substantial overlap between infected and noninfected collections exists. The purpose of this study was to develop and validate a scoring system on the basis of CT imaging findings as well as laboratory and clinical parameters for distinguishing infected from noninfected abdominal fluid collections after surgery.

Materials And Methods: The score developmental cohort included 100 consecutive patients (69 men, 31 women; mean age, 58 ± 17 years) who underwent portal-venous phase CT within 24 hours before CT-guided intervention of postoperative abdominal fluid collections. Imaging features included attenuation (Hounsfield unit [HU]), volume, wall enhancement and thickness, fat stranding, as well as entrapped gas of fluid collections. Laboratory and clinical parameters included diabetes, intake of immunosuppressive drugs, body temperature, C-reactive protein, and leukocyte blood cell count. The score was validated in a separate cohort of 30 consecutive patients (17 men, 13 women; mean age, 51 ± 15 years) with postoperative abdominal fluid collections. Microbiologic analysis from fluid samples served as the standard of reference.

Results: Diabetes, body temperature, C-reactive protein, attenuation of the fluid collection (in HUs), wall enhancement and thickness of the wall, adjacent fat stranding, as well as entrapped gas within the fluid collection were significantly different between infected and noninfected collections (P < 0.001). Multiple logistic regression analysis revealed diabetes, C-reactive protein, attenuation of the fluid collection (in HUs), as well as entrapped gas as significant independent predictors of infection (P < 0.001) and thus was selected for constructing a scoring system from 0 to 10 (diabetes: 2 points; C-reactive protein, ≥ 100 mg/L: 1 point; attenuation of fluid collection, ≥ 20 HU: 4 points; entrapped gas: 3 points). The model was well calibrated (Hosmer-Lemeshow test, P = 0.36). In the validation cohort, scores of 2 or lower had a 90% (95% confidence interval [CI], 56%-100%) negative predictive value, scores of 3 or higher had an 80% (95% CI, 56%-94%) positive predictive value, and scores of 6 or higher a 100% (95% CI, 74%-100%) positive predictive value for diagnosing infected fluid collections. Receiver operating characteristic analysis revealed an area under the curve of 0.96 (95% CI, 0.88-1.00) for the score.

Conclusions: We introduce an accurate scoring system including quantitative radiologic, laboratory, and clinical parameters for distinguishing infected from noninfected fluid collections after abdominal surgery.
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January 2015

Iterative reconstructions versus filtered back-projection for urinary stone detection in low-dose CT.

Acad Radiol 2013 Nov;20(11):1429-35

Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, Raemistrasse 100, CH-8091, Zurich, Switzerland.

Rationale And Objectives: To evaluate prospectively, in patients with suspected or known urinary stone disease, the image quality and diagnostic confidence of nonenhanced abdominal low-dose computed tomography (CT) with iterative reconstruction (IR) compared to filtered back-projection (FBP).

Materials And Methods: Fifty consecutive patients with suspected (n = 33) or known (n = 17) urinary stone disease underwent nonenhanced abdominal low-dose CT (120 kVp, 30 effective mAs, 1.6 ± 0.5 mSv). Reconstructions were performed with sinogram-affirmed IR and with FBP. Attenuation (in Hounsfield units) was measured in subcutaneous fat and urinary bladder; image noise was determined. Two readers assessed image quality, number and location of urinary calculi were recorded, and diagnostic confidence was assessed. Statistical analyses included Mann-Whitney, Friedman's two-way, Wilcoxon signed rank, Pearson's, and Spearman's rank order correction tests.

Results: Attenuation of urinary bladder (P = .208, reader 1; P = .123, reader 2) and fat (P = .568, reader 1; P = .834, reader 2) was similar among FBP and IR datasets. Image noise was reduced in IR datasets by 40.1% (P < .001). IR improved image quality (P < .01), and obesity as factor impairing image quality was noted in FBP but not in IR images (P < .05). There was no significant difference in number of calculi in datasets reconstructed with IR and FBP (P = .102, reader 1; P = .059, reader 2). Diagnostic confidence regarding identification of urinary calculi improved with IR (P < .05, reader 1; P < .01, reader 2).

Conclusion: IR improves image quality and confidence for diagnosing urinary stone disease in abdominal low-dose CT.
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November 2013

Split-bolus dual-energy CT urography: protocol optimization and diagnostic performance for the detection of urinary stones.

Abdom Imaging 2013 Oct;38(5):1136-43

Department of Radiology, University Hospital Zurich, Raemistrasse 100, 8091, Zurich, Switzerland,

Purpose: Prospective protocol optimization, determination of image quality and diagnostic performance of virtual non-enhanced images (VNEI) derived from split-bolus dual-energy computed tomography (DECT) urography in patients with urinary stones.

Methods: IRB-approved, prospective study of 100 patients who, after written informed consent, underwent single-energy, non-enhanced CT and split-bolus, contrast-enhanced DECT (30 + 50 mL of contrast media; combined nephro-urographic acquisition). DECT was performed using setting A (80/140 kVp) in the first 20, and setting B (100/140 kVp) in the second 20 patients. Tin filtration was used in all patients. After a pre-analysis of VNEI quality, 60 additional patients were examined using setting B. Two readers qualitatively and quantitatively determined image quality of all weighted-average DECT images regarding urinary tract opacification (n = 100), and all VNEI regarding quality of iodine subtraction and urinary stone detection (n = 80). True nonenhanced (TNEI) images were the standard of reference for statistical analysis (inter-reader variability and diagnostic performance characteristics).

Results: The urinary tract was completely opacified in 94% (94/100) of patients. Iodine subtraction was improved (p < 0.01) and image noise of VNEI was lower (p < 0.05) in DECT setting B. On VNEI, 83% (86/104) of urinary stones were correctly identified and 17% (18/104) were missed. Stones missed (2.5 mm, 1-4) were significantly smaller than stones correctly identified (5 mm, 2-27; p < 0.001). Diagnostic accuracy was 98% on a per-renal-unit basis and 96% on a per-patient basis. Inter-reader agreements were excellent (κ = 0.91-1.00; ICC = 0.86-0.99).

Conclusions: Split-bolus DECT urography was technically feasible and quality of VNEI was improved with the 100/140 kVp setting. Detection of urinary stones <4 mm on VNEI was limited.
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October 2013

Diagnostic performance of dual-energy CT for the detection of traumatic bone marrow lesions in the ankle: comparison with MR imaging.

Radiology 2012 Jul 8;264(1):164-73. Epub 2012 May 8.

Department of Radiology, University Hospital Zurich, Ramistrasse 100, 8091 Zurich, Switzerland.

Purpose: To evaluate prospectively the performance of noncalcium images reconstructed from dual-energy (DE) computed tomography (CT) for the diagnosis of bone marrow lesions in patients with acute ankle joint trauma in comparison with magnetic resonance (MR) images.

Materials And Methods: The study had local ethics board approval, and written informed consent was obtained. Thirty consecutive patients (15 women; mean age, 34 years±11.8 [standard deviation]) underwent dual-source DE CT (80 kVp and 140 kVp with tin filter) and MR imaging within 1 day following acute ankle trauma. DE CT data were postprocessed by using a three-material decomposition algorithm for generating noncalcium images. MR and noncalcium images were graded by two blinded, independent readers using a four-point system (1=distinct bone marrow lesion, 4=no lesion); CT numbers in noncalcium images were calculated by a third reader. MR imaging interpretations served as the reference standard.

Results: Interreader agreement for qualitative grading of DE CT images was substantial (κ=0.66). The respective sensitivity, specificity, positive predictive value, and negative predictive value of DE CT for depicting distinct bone marrow lesions for both readers were 90.0% each, 80.5% and 81.6%, 25.4% and 26.5%, and 99.1% each. In regions without abnormality, CT numbers in noncalcium images gradually increased from proximal to distal location (P<.001). Significant differences in CT numbers were found in regions positive for bone marrow lesions compared with those that were negative (P<.001). CT numbers for the diagnosis of distinct bone marrow lesions according to MR imaging revealed areas under the receiver operating characteristic curve of 0.973, 0.813, and 0.758 for ankle mortise, talar dome, and talar body/head, respectively.

Conclusion: Compared with MR images, distinct traumatic bone marrow lesions of the ankle joint can be diagnosed on noncalcium images reconstructed from DE CT with high sensitivity and excellent negative predictive value, but with moderate specificity and low positive predictive value.
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July 2012

Automated tube potential selection for standard chest and abdominal CT in follow-up patients with testicular cancer: comparison with fixed tube potential.

Eur Radiol 2012 Sep 2;22(9):1937-45. Epub 2012 May 2.

Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, Raemistrasse 100, CH-8091 Zurich, Switzerland.

Objective: To evaluate prospectively, in patients with testicular cancer, the radiation dose-saving potential and image quality of contrast-enhanced chest and abdominal CT with automated tube potential selection.

Methods: Forty consecutive patients with testicular cancer underwent contrast-enhanced arterio-venous chest and portal-venous abdominal CT with automated tube potential selection (protocol B; tube potential 80-140 kVp), which is based on the attenuation of the CT topogram. All had a first CT at 120 kVp (protocol A) using the same 64-section CT machine and similar settings. Image quality was assessed; dose information (CTDI(vol)) was noted.

Results: Image noise and attenuation in the liver and spleen were significantly higher for protocol B (P < 0.05 each), whereas attenuation in the deltoid and erector spinae muscles was similar. In protocol B, tube potential was reduced to 100 kVp in 18 chest and 33 abdominal examinations, and to 80 kVp in 5 abdominal CT examinations; it increased to 140 kVp in one patient. Image quality of examinations using both CT protocols was rated as diagnostic. CTDI(vol) was significantly lower for protocol B compared to protocol A (reduction by 12%, P < 0.01).

Conclusion: In patients with testicular cancer, radiation dose of chest and abdominal CT can be reduced with automated tube potential selection, while image quality is preserved.
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September 2012

Dual-energy CT for characterization of the incidental adrenal mass: preliminary observations.

AJR Am J Roentgenol 2012 Jan;198(1):138-44

Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, Raemistrasse 100, CH-8091 Zurich, Switzerland.

Objective: The purpose of our study was to evaluate the accuracy of virtual unenhanced images reconstructed from contrast-enhanced dual-energy CT for the differentiation of incidental adrenal masses in comparison with standard unenhanced CT.

Materials And Methods: One hundred-forty patients (mean age, 74±9 years) underwent unenhanced and contrast-enhanced CT of the abdomen, the latter acquired with dual-energy for reconstruction of virtual unenhanced images. Two blinded and independent readers (R1 and R2) measured attenuation of each incidental adrenal mass on standard unenhanced and virtual unenhanced images using an optimized dual-energy three-material decomposition algorithm.

Results: Fifty-one incidental adrenal masses were found in 42 of 135 patients (31%); 39 incidental adrenal masses were ≥1 cm. On the basis of unenhanced CT, 29 of 51 incidental adrenal masses and 22 of 39 incidental adrenal masses≥1 cm were classified as benign (HU<10). Virtual unenhanced image quality was rated as good or with mild impairment (2.45±0.83 for R1, 2.45±0.99 for R2). Image noise was 12.7±3.6 HU in unenhanced images and 8.8±2.0 HU in virtual unenhanced images (p<0.001). There was no significant difference in incidental adrenal mass attenuation between unenhanced and virtual unenhanced images for all incidental adrenal masses (5.9±21.0 HU vs 7.0±20.6 HU, p=0.48) and for those≥1 cm (6.6±18.5 HU vs 7.9±18.3 HU, p=0.87). Sensitivity, specificity, and accuracy of virtual unenhanced images for the characterization of incidental adrenal masses as probably benign were 76%, 82%, and 78% for R1 and 79%, 95%, and 86% for R2, respectively. For incidental adrenal masses≥1 cm, sensitivity, specificity, and accuracy increased to 95%, 100%, and 97% for R1 and 91%, 100%, and 95% for R2.

Conclusion: Reconstruction of virtual unenhanced images from contrast-enhanced dual-energy CT of the abdomen allows the characterization of the incidental adrenal masses with a good accuracy compared with standard unenhanced CT, with the most favorable results in incidental adrenal masses measuring≥1 cm.
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January 2012

Prospective morphologic and dynamic assessment of deep flexor tendon healing in zone II by high-frequency ultrasound: preliminary experience.

AJR Am J Roentgenol 2011 Dec;197(6):W1110-7

Department of Diagnostic and Interventional Radiology, Musculoskeletal Imaging Research Group, University Hospital Zurich, Switzerland.

Objective: The purpose of this article is to prospectively evaluate early postoperative morphologic and functional changes after deep flexor tendon repair in zone II using ultrasound and to correlate findings from ultrasound with the clinical outcome.

Subjects And Methods: Ten patients (mean age, 34 years; range, 19-55 years) with 11 injured deep flexor tendons of the hand underwent surgical tendon repair. Postoperative tendon morphology was assessed with gray-scale and power Doppler ultrasound over a period of 3 months. Tendon excursion over the proximal interphalangeal joint was assessed by sonographic scar tracking. Correlation of ultrasound findings with clinical outcome was performed.

Results: Almost all repaired tendons exhibited a spindlelike shape after 1 week, of which 50% developed a normal shape after 12 weeks. A persisting spindlelike shape over 3 months was associated with a significantly increased tendon excursion (p < 0.05) and a trend toward better active motion of the fingers (p = 0.056). Tendons with increased power Doppler signal showed a significantly better tendon excursion and active motion after 12 weeks (all p < 0.05). Tendon excursion measurements obtained by scar tracking showed excellent correlation (r = 0.84; p < 0.05) with total active finger motion.

Conclusion: Preliminary data of this study indicate a better clinical outcome if a sutured tendon maintains a spindlelike shape and increased power Doppler signal. This might indicate a predominantly intrinsic healing pattern with reduced adhesion formation. Ultrasound morphology, power Doppler signal, and tendon excursion may be helpful tools to rate tendon healing and to establish individually modified rehabilitation protocols.
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December 2011

MR imaging of the postoperative knee.

J Magn Reson Imaging 2011 Nov;34(5):1007-21

Department of Radiology, University Hospital Zurich, Zurich, Switzerland.

Advances in orthopedic and arthroscopic surgical procedures of the knee such as, knee replacement, ligamentous reconstruction as well as articular cartilage and meniscus repair techniques have resulted in a significant increase in the number of patients undergoing knee arthroscopy or open surgery. As a consequence postoperative MR imaging examinations increase. Comprehensive knowledge of the normal postoperative MR imaging appearances and abnormal findings in the knee associated with failure or complications of common orthopedic and arthroscopic surgical procedures currently undertaken is crucial. This article reviews the various normal and pathological postoperative MR imaging findings following anterior and posterior cruciate ligament, medial collateral ligament and posterolateral corner reconstruction, meniscus and articular cartilage surgery as well as total knee arthroplasty with emphasis on those surgical procedures which general radiologists will likely be faced in their daily clinical routine.
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November 2011

Quantitative radiologic criteria for the diagnosis of lumbar spinal stenosis: a systematic literature review.

BMC Musculoskelet Disord 2011 Jul 28;12:175. Epub 2011 Jul 28.

Horten Centre for patient oriented research and knowledge transfer, University Zurich, Raemistrasse 100, CH 8091 Zurich, Switzerland.

Background: Beside symptoms and clinical signs radiological findings are crucial in the diagnosis of lumbar spinal stenosis (LSS). We investigate which quantitative radiological signs are described in the literature and which radiological criteria are used to establish inclusion criteria in clinical studies evaluating different treatments in patients with lumbar spinal stenosis.

Methods: A literature search was performed in Medline, Embase and the Cochrane library to identify papers reporting on radiological criteria to describe LSS and systematic reviews investigating the effects of different treatment modalities.

Results: 25 studies reporting on radiological signs of LSS and four systematic reviews related to the evaluation of different treatments were found. Ten different parameters were identified to quantify lumbar spinal stenosis. Most often reported measures for central stenosis were antero-posterior diameter (< 10 mm) and cross-sectional area (< 70 mm(2)) of spinal canal. For lateral stenosis height and depth of the lateral recess, and for foraminal stenosis the foraminal diameter were typically used. Only four of 63 primary studies included in the systematic reviews reported on quantitative measures for defining inclusion criteria of patients in prognostic studies.

Conclusions: There is a need for consensus on well-defined, unambiguous radiological criteria to define lumbar spinal stenosis in order to improve diagnostic accuracy and to formulate reliable inclusion criteria for clinical studies.
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July 2011

Whole-body CT in polytrauma patients: effect of arm positioning on thoracic and abdominal image quality.

Emerg Radiol 2011 Aug 7;18(4):285-93. Epub 2011 Apr 7.

Institute for Diagnostic and Interventional Radiology, University Hospital Zurich, Raemistrasse 100, 8091, Zurich, Switzerland.

The purpose of this study is to assess the influence of different arm positioning techniques on thoracic and abdominal image quality and radiation dose of whole-body trauma CT (wbCT). One hundred and fifty polytrauma patients (104 male, mean age 47 ± 19) underwent wbCT with arms elevated above the head (group A, n=50), alongside the abdomen (group B, n=50), and on a pillow ventrally to the chest with both arms flexed (group C, n=50). Two blinded, independent observers measured image noise and rated image quality (scores 1-3) of the liver, aorta, spleen, spine, and lower lungs. Radiation dose parameters were noted, and the abdomens' anterior-posterior diameter and scan lengths were measured. Interreader agreements for image noise (r=0.86; p<0.001) and subjective image quality (k=0.71-0.84) were good. Noise was lower (p<0.05), image quality of the liver, aorta, spleen, and spine was higher, and radiation dose lower in group A than in groups B and C (p<0.001, each). Image quality of the spleen, liver, and aorta were higher in group C than in group B (p<0.05, each). No significant differences in scan length (p=0.61) were found among groups. Abdominal anterior-posterior diameter correlated significantly with noise (r=0.82; p<0.01) and dose (r=0.47; p<0.001). Estimated effective radiation doses were significantly (p<0.001) higher in groups B (21.2 mSv) and C (21.9 mSv) as compared to A (16.1 mSv). In wbCT for polytrauma patients, positioning of the arms above the head results in better image quality and lower radiation dose. Placing the flexed arms on a large pillow ventrally to the chest significantly improves image quality as compared to positioning alongside the abdomen.
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August 2011

Quantification of liver fat in the presence of iron and iodine: an ex-vivo dual-energy CT study.

Invest Radiol 2011 Jun;46(6):351-8

Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, Zurich, Switzerland.

Purpose: Iodinated contrast media (CM) and iron in the liver are known to hinder an accurate quantification of liver fat content (LFC) with single-energy computed tomography (SECT). The purpose of this study was to evaluate the feasibility and accuracy of dual-energy CT (DECT) for ex vivo quantification of LFC, in the presence of iron and CM, compared with SECT.

Materials And Methods: Sixteen phantoms with a defined LFC of 0%, 10%, 30%, and 50% fat and with varying iron content (0, 1.5, 3, and 6 mg/mL wet weight liver) were scanned with a second-generation dual-source 128-slice CT system. Phantoms were scanned unenhanced and contrast-enhanced after adding 1.0 mg/mL iodine to each phantom. Both SECT (120 kV) and DECT (tube A: 140 kV, using a tin filter 228 mAs; tube B: 80 kV, 421 mAs) data were acquired. An iron-specific dual-energy 3-material decomposition algorithm providing virtual noniron images (VNI) was used to subtract iron and CM from the data. CT numbers (Hounsfield units) were measured in all data sets, including 120 kV from SECT, as well as 140 kV, 80 kV, 50%:50% weighted 80 kV/140 kV, and VNI derived from DECT. The dual-energy index was calculated from 80 kV and 140 kV data. SECT and DECT measurements (Hounsfield units) including the dual-energy index of unenhanced and contrast-enhanced phantoms were compared with the known titrated LFC, using Pearson correlation analysis and Student t test for related samples.

Results: Inter-reader agreement was excellent for all measurements of CT numbers in both SECT and DECT data (Pearson r, 0.965-1.0). For fat quantification in the absence of iron and CM, CT numbers were similar in SECT and DECT (all, P > 0.05), showing a linear correlation with titrated LFC (r ranging from 0.981 to 0.999; P < 0.01). For fat quantification in the presence of iron but without CM, significant underestimation of LFC was observed for all measurements in SECT and DECT (P < 0.05), except for VNI. Measurements in VNI images allowed for an accurate LFC estimation, with no significant differences compared with measurements in iron-free phantoms (all, P > 0.25). For fat quantification in the presence of iron and CM, further underestimation of LFC was seen for measurements in SECT and DECT (P < 0.015), except for VNI. Measurements in VNI images showed a high accuracy for estimating the LFC, with no significant difference compared with measurements in iron- and CM-free phantoms (P > 0.2).

Conclusions: Our ex vivo phantom study indicates that DECT with the use of a dedicated, iron-specific 3-material decomposition algorithm allows for the accurate quantification of LFC, even in the presence of iron and iodinated CM. VNI images reconstructed from DECT data equal nonenhanced SECT data of liver without CM by eliminating iron and iodine from the images. No added value was seen for DECT as compared with SECT for quantification of LFC in the absence of iron and iodine.
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June 2011