Impact of Hybrid Iterative Reconstruction on Agatston Coronary Artery Calcium Scores in Comparison to Filtered Back Projection in Native Cardiac CT.

PURPOSE: To investigate whether the effects of hybrid iterative reconstruction (HIR) on coronary artery calcium (CAC) measurements using the Agatston score lead to changes in assignment of patients to cardiovascular risk groups compared to filtered back projection (FBP). MATERIALS AND METHODS: 68 patients (mean age 61.5 years; 48 male; 20 female) underwent prospectively ECG-gated, non-enhanced, cardiac 256-MSCT for coronary calcium scoring. Scanning parameters were as follows: Tube voltage, 120 kV; Mean tube current time-product 63.67 mAs (50 - 150 mAs); collimation, 2 × 128 × 0.625 mm. Images were reconstructed with FBP and with HIR at all levels (L1 to L7). Two independent readers measured Agatston scores of all reconstructions and assigned patients to cardiovascular risk groups. Scores of HIR and FBP reconstructions were correlated (Spearman). Interobserver agreement and variability was assessed with ĸ-statistics and Bland-Altmann-Plots. RESULTS: Agatston scores of HIR reconstructions were closely correlated with FBP reconstructions (L1, R = 0.9996; L2, R = 0.9995; L3, R = 0.9991; L4, R = 0.986; L5, R = 0.9986; L6, R = 0.9987; and L7, R = 0.9986). In comparison to FBP, HIR led to reduced Agatston scores between 97 % (L1) and 87.4 % (L7) of the FBP values. Using HIR iterations L1 - L3, all patients were assigned to identical risk groups as after FPB reconstruction. In 5.4 % of patients the risk group after HIR with the maximum iteration level was different from the group after FBP reconstruction. CONCLUSION: There was an excellent correlation of Agatston scores after HIR and FBP with identical risk group assignment at levels 1 - 3 for all patients. Hence it appears that the application of HIR in routine calcium scoring does not entail any disadvantages. Thus, future studies are needed to demonstrate whether HIR is a reliable method for reducing radiation dose in coronary calcium scoring.

Age-related incidence of pulmonary embolism and additional pathologic findings detected by computed tomography pulmonary angiography.

OBJECTIVE: To compare the incidence of pulmonary embolism (PE) and additional pathologic findings (APF) detected by computed tomography pulmonary angiography (CTPA) according to different age-groups. MATERIALS AND METHODS: 1353 consecutive CTPA cases for suspected PE were retrospectively reviewed. Patients were divided into seven age groups: ≤29, 30-39, 40-49, 50-59, 60-69, 70-79 and ≥80 years. Differences between the groups were tested using Fisher's exact or chi-square test. A p-value<0.0024 indicated statistical significance when Bonferroni correction was used. RESULTS: Incidence rates of PE ranged from 11.4% to 25.4% in different age groups. The three main APF were pleural effusion, pneumonia and pulmonary nodules. No significant difference was found between the incidences of PE in different age groups. Furthermore, APF in different age groups revealed no significant differences (all p-values>0.0024). CONCLUSION: The incidences of PE and APF detected by CTPA reveal no significant differences between various age groups.

Sacroplasty in a cadaveric trial: comparison of CT and fluoroscopic guidance with and without balloon assistance.

Sacral insufficiency fractures can cause severe, debilitating pain to patients concerned. The incidence of this fracture type correlates with the appearance of osteoporosis in the elderly population. A polymethylmethacrylate (PMMA) cement injection procedure called sacroplasty has been recently described as an optional method for the treatment of this fracture type. However, the correct cement placement in the complex anatomical structure of the sacrum is a surgical challenge. The aim of the study is to compare the precision, safety, and radiation exposure of standard multiplanar fluoroscopy and computed tomography (CT) guidance for PMMA application to the sacrum using both balloon-assisted sacroplasty and conventional sacroplasty. A controlled experimental investigation in a human cadaver trial has been performed. Two imaging and two application modalities to monitor percutaneous PMMA injection to the sacrum were examined. The application forms were randomized from side to side of the pelvis. We found less cement extravasation in the CT-guided groups, but also a significant higher radiation exposure (P < 0.05) by using CT guidance. The conventional fluoroscopy-guided sacroplasty revealed the shortest procedure time (incision to closure time) of all treatment groups (P < 0.01). These findings show no difference regarding cement extravasation between ballon-assisted and conventional sacroplasty. Further, in comparison to fluoroscopy-assisted technique, the CT-guided cement injection seems to decrease the risk of cement extravasation, irrespective of the use of an additional balloon assistance. However, we have to consider a greater radiation exposure using CT guidance. Further investigations will proof the suitability in the normal course of clinical life.

Penalized maximum-likelihood sinogram restoration for dual focal spot computed tomography.

Due to various system non-idealities, the raw data generated by a computed tomography (CT) machine are not readily usable for reconstruction. Although the deterministic nature of corruption effects such as crosstalk and afterglow permits correction by deconvolution, there is a drawback because deconvolution usually amplifies noise. Methods that perform raw data correction combined with noise suppression are commonly termed sinogram restoration methods. The need for sinogram restoration arises, for example, when photon counts are low and non-statistical reconstruction algorithms such as filtered backprojection are used. Many modern CT machines offer a dual focal spot (DFS) mode, which serves the goal of increased radial sampling by alternating the focal spot between two positions on the anode plate during the scan. Although the focal spot mode does not play a role with respect to how the data are affected by the above-mentioned corruption effects, it needs to be taken into account if regularized sinogram restoration is to be applied to the data. This work points out the subtle difference in processing that sinogram restoration for DFS requires, how it is correctly employed within the penalized maximum-likelihood sinogram restoration algorithm and what impact it has on image quality.

[Computer-assisted screw placement into the posterior pelvic ring: assessment of different navigated procedures in a cadaver trial]. / Computerassistierte Verschraubung des hinteren Beckenrings : Systematischer Vergleich verschiedener Navigationsverfahren am Kadaverpräparat.

OBJECTIVE: Computer-assisted procedures have recently been introduced for navigated iliosacral screw placement. Currently there are only few data available reflecting results and outcome of the different navigated procedures which may be used for this indication. We therefore evaluated the features of a new 3D image intensifier used for navigated iliosacral screw placement compared to 2D fluoroscopic and CT navigation. MATERIALS AND METHODS: Twenty fixed human cadavers were used in this trial. Cannulated cancellous screws were percutaneously implanted in the supine position in four treatment groups. An optoelectronic system was used for the navigated procedures. Screw placement was postoperatively assessed by fluoroscopic 3D scan and CT. The target parameters of this investigation were practicability, precision as well as procedure and fluoroscopic time per screw. RESULTS: All navigated procedures revealed a significant loss of time compared to non-navigated screw placement (2D: p<0.001, 3D: p>0.05, CT: p<0.001). Simultaneously a significant decrease of radiation exposure time was observed in the navigated groups (p<0.001 each). The misplacement rate was 20% in the non-navigated and the 2D fluoroscopic navigated group each. Procedures providing 3D imaging of the posterior pelvis did not produce any screw misplacement (p>0.05). However, the CT procedure was associated with time-consuming registration and high rates of failed matching procedures. CONCLUSION: Our data show a clear benefit of using C-arm navigation for iliosacral screw placement compared with the CT-based procedure. While both fluoroscopy-based navigation procedures decrease intraoperative radiation exposure times, only 3D fluoroscopic navigation seems to improve the precision compared to non-navigated screw placement.

[Injury pattern and clinical course of children with multiple injuries in comparison to adults, Ab 11-year analysis at a clinic of maximum utilization]. / Verletzungsmuster und klinischer Verlauf polytraumatisierter Kinder im Vergleich mit Erwachsenen. Eine 11-Jahres-Analyse am Klinikum der Maximalversorgung.

Due to the small number of polytraumatized children treated in single clinics, only a few studies are available that compare multiply injured children and adults. However, the differences between the two groups with respect to type of injury, injury patterns and pathophysiology may have some crucial effect on the clinical course and are therefore essential for the treatment regime. In this study data about the epidemiology, the preclinical treatment, the clinical course and the complication rates of polytraumatized children and adults were analysed. The aim of this study was to point out the main differences between the two collectives and to compare the results with the current literature. Traffic accidents were the leading cause for trauma (children 77.8%, adults 62.6%). Children more often were transported by helicopter than adults. In both age groups head injuries and fractures of the extremities were most frequent. Adults had a prolonged ventilation time as well as an increased stay in ICU and a regular ward.

Evaluation of spatial and temporal resolution for ECG-gated 16-row multidetector CT using a dynamic cardiac phantom.

Measurements of spatial and temporal resolution for ECG-gated scanning of a stationary and moving heart phantom with a 16-row MDCT were performed. A resolution phantom with cylindrical holes from 0.4 to 3.0 mm diameter was mounted to a cardiac phantom, which simulates the motion of a beating heart. Data acquisition was performed with 16x0.75 mm at various heart rates (HR, 60-120 bpm), pitches (0.15-0.30) and scanner rotation times (RT, 0.42 and 0.50 s). Raw data were reconstructed using a multi-cycle real cone-beam reconstruction algorithm at multiple phases of the RR interval. Multi-planar reformations (MPR) were generated and analyzed. Temporal resolution and cardiac cycles used for image reconstruction were calculated. In 97.2% (243/250) of data obtained with the stationary phantom, the complete row of holes with 0.6 mm was visible. These results were independent of heart rate, pitch, scanner rotation time and phase point of reconstruction. For the dynamic phantom, spatial resolution was determined during phases of minimal motion (116/250). In 40.5% (47/116), the resolution was 0.6 mm and in 37.1% (43/116) 0.7 mm. Temporal resolution varied between 63 and 205 ms, using 1.5-4.37 cardiac cycles for image reconstruction.

[Bone grafts endoscopically applied to the spine Ergebnisse der anterioren Fusion und therapeutische Konsequenzen]. / Endoskopische Knochentransplantation an der Wirbelsäule Ergebnisse der anterioren Fusion und therapeutische Konsequenzen.

The application of autogenous bone grafts represents the golden standard for reconstruction of the load-bearing anterior column in the thoracolumbar spine. However, the osseous integration of the implanted grafts is demanding and delayed union or pseudarthrosis may occur. There are no standardized data available yet indicating the further course in such cases. The aim of this study was to evaluate the incorporation of endoscopically applied grafts and to develop therapeutic strategies for delayed or non-fusions. Twenty patients suffering from unstable injuries of the thoracolumbar spine were studied in a prospective clinical trial. After primary dorsal stabilization, the anterior column was thoracoscopically reconstructed with an autogenous iliac crest graft and a fixed-angle implant (MACS). The osseous integration of the bone grafts was detected by MSCT 1 year postoperatively. Complete integration of the transplanted bone grafts was observed in only 65% of the cases. In 25% partial integration was detected and in two cases a fracture of the transplanted iliac crest graft occurred. Despite the incomplete integration of the bone grafts, the further course without surgical intervention revealed no clinical or radiological evidence of a concomitant implant loosening or a relevant secondary loss of correction. Similar to the open technique, endoscopic reconstruction of the anterior column with autogenous bone grafts may lead to disadvantageous results concerning the integration and healing of the applied bone grafts. Decision making in such cases depends on the individual clinical and radiological findings (i.e., evidence of implant loosening and concomitant loss of correction).

Correlation of time to platelet engraftment with amount of transplanted CD34+CD41+ cells after allogeneic bone marrow transplantation.

A major problem after autologous or allogeneic stem cell transplantation is prolonged thrombocytopenia. There are several studies published about correlations of the composition of the graft and time to platelet engraftment for autologous transplantation but only a few studies for allogeneic transplantation. In our study, we wanted to find out whether the correlation between the time to platelet engraftment and amount of transplanted CD34(+)CD41(+) cells described previously after autologous peripheral blood stem cell transplantation could be reproduced in the allogeneic bone marrow transplantation setting. We found correlations not only for the number of transplanted CD34(+) cells with the time to leukocyte engraftment (r = -0.32, p = 0.045) but also for the number of transplanted CD34(+)CD41(+) cells and time to platelet engraftment (r = -0.34, p = 0.038), which were both statistically significant. A significant correlation between transplanted CD34(+) cells versus platelet engraftment and transplanted CD34(+)CD41(+) cells versus leukocyte engraftment was not found. The finding that the amount of committed megakaryocyte progenitor cells in the graft is an important predictive factor for platelet engraftment after allogeneic bone marrow transplantation might be the base for future studies of ex vivo expansion of clonable megakaryocyte precursors.