Implementation and validation of portal dosimetry with an amorphous silicon EPID in the energy range from 6 to 25 MV

The purpose of this study was to develop, implement and validate a method for portal dosimetry with an amorphous silicon EPID for a wide energy range. Analytic functions were applied in order to correct for nonlinearities in detector response with dose rate, irradiation time and total dose. EPID scattering processes were corrected for by means of empirically determined convolution kernels. For a variety of rectangular and irregularly shaped fields, head scatter factors determined from central axis portal dose values and those measured with an ionization chamber showed a maximum deviation of 0.5%. The accuracy of our method was further investigated for pretreatment IMRT verification (i.e. without absorbers in the beam). The agreement between EPID and film dosimetry was quantified using gamma (gamma) evaluation, with 2% dose and 2 mm distance-to-agreement criteria. All gamma-distributions showed a gamma(mean) < 0.5, a 99th percentile <1.5 and a fraction of pixels with gamma > 1 smaller than 7%. The number of monitor units delivered by single segments of the IMRT fields could be extracted from the portal images with high accuracy. Measured and delivered doses were within +/-3% for more than 98% of data points. Ghosting effects were found to have limited effects on dosimetric IMRT verification.     

Rapid antidepressant effect of S-ketamine in schizophrenia

Rapid anti-suicidal and antidepressant effects of ketamine have repeatedly been confirmed in unipolar and bipolar depression. Although meaningful antidepressant efficacy of ketamine has also been shown in depressed patients with a history of psychotic symptoms, its administration in psychotic disorders has largely been neglected due to its potential to exacerbate dissociative or psychotic symptoms. Presenting a case of a young female inpatient suffering from schizophrenia with a severe post-psychotic depression, we demonstrate a robust anti-suicidal and antidepressant effect of S-ketamine infusions administered thrice weekly for 3 weeks in total. Importantly, no relevant psychotic or dissociative symptoms occurred during the whole augmentation treatment period leading to a sustained remission of depressive symptoms and suicidality. Our safe and effective experience with intravenous S-ketamine might encourage researchers and clinicians to widen its administration range beyond the diagnosis of depression to enrich the current knowledge of ketamine effects in psychotic disorders.     

Die Unfallchirurgie und die Deutsche Gesellschaft für Unfallchirurgie

Die Unfallchirurgie -     

Are our expectations bigger than the results we achieve? A comparative study analysing potential advantages of ankle arthroplasty over arthrodesis

Purpose

Prior studies have reported improved gait performance and kinematics after total ankle arthroplasty (TAR) compared to ankle arthrodesis (AAD). Given these findings, AAD has been primarily considered as a salvage procedure that may lead to adjacent joint degeneration.

Methods

A total of 101 TAR and 40 screw arthrodeses were enrolled in a retrospective study with a prospectively designed follow-up examination that included gait analysis and outcome assessment with the AOFAS hindfoot score and FAOS questionnaire.

Results

Significant asymmetry in gait and reduced range of motion compared to normal remained after both procedures. Subjective outcome improved after both procedures, and pain was significantly better after TAR. Limited functional gains after TAR and joint degeneration to the same degree after both procedures was seen in the mid-term. Hindfoot fusion seemed to have a greater impact on postoperative function than ankle arthrodesis.

Conclusion

Considering only minor functional gains of TAR compared to AAD the implantation of current TAR designs in large patient series may be questioned.     

Customised osteotomy guides and endoprosthetic reconstruction for periacetabular tumours

Purpose

We sought to analyse clinical and oncological outcomes of patients after guided resection of periacetabular tumours and endoprosthetic reconstruction of the remaining defect.

Methods

From 1988 to 2008, we treated 56 consecutive patients (mean age 52.5 years, 41.1 % women). Patients were followed up either until death or February 2011 (mean follow up 5.5 years, range 0.1–22.5, standard deviation ± 5.3). Kaplan–Meier analysis was used to estimate survival rates.

Results

Disease-specific survival was 59.9 % at five years and 49.7 % at ten and 20 years, respectively. Wide resection margins were achieved in 38 patients, whereas 11 patients underwent marginal and seven intralesional resection. Survival was significantly better in patients with wide or marginal resection than in patients with intralesional resection (p = 0.022). Survival for patients with secondary tumours was significantly worse than for patients with primary tumours (p = 0.003). In 29 patients (51.8 %), at least one reoperation was necessary, resulting in a revision-free survival of 50.5 % at five years, 41.1 % at ten years and 30.6 % at 20 years. Implant survival was 77.0 % at five years, 68.6 % at ten years and 51.8 % at 20 years. A total of 35 patients (62.5 %) experienced one or more complications after surgery. Ten of 56 patients (17.9 %) experienced local recurrence after a mean of 8.9 months. The mean postoperative Musculoskeletal Tumor Society (MSTS) score was 18.1 (60.1 %).

Conclusion

The surgical approach assessed in this study simplifies the process of tumour resection and prosthesis implantation and leads to acceptable clinical and oncological outcomes.     

Quality of Life After Surgical Treatment of Early Barrett’s Cancer: A Prospective Comparison of the Ivor-Lewis Resection Versus the Modified Merendino Resection

Introduction

The Merendino (MER) procedure has been evaluated as an alternative to transthoracic esophageal resection (TER) for early stage Barrett’s carcinoma. Apart from reducing morbidity and mortality, improvements concerning postoperative health-related quality of life (HRQL) have been postulated. The aim of our study was to compare HRQL between these procedures.

Materials and methods

Between July 2000 and July 2007, 117 patients with early Barrett’s carcinoma underwent surgery. Patients with tumor recurrence were excluded from the study. HRQL was assessed 1 and 2 years after surgery using the European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Core Questionnaire (EORTC-QLQ-C30) and the QLQ-OES18 module. Patients recently diagnosed with early Barrett’s carcinoma served as controls. Symptoms that showed a difference of more than ten between the control and the study groups were considered clinically relevant and were tested for significant differences between the study groups using the Mann–Whitney U test (p < 0.05).

Results

The response rates for the questionnaires ranged between 70 and 93 %. In the MER group, more items reflected a clinical relevant impairment of HRQL than in the TER group. Significant complaints in the MER group included nausea/vomiting, appetite loss, local pain, difficulties with social eating, and choking. Moreover, we found a significant restriction concerning global health and emotional and social functioning in this group 1 year after surgery. 2 years postoperatively, hardly any differences between the operative techniques could be detected. The only symptom in favor of the MER procedure was a better dysphagia score postoperatively.

Conclusion

Our study suggests that MER procedure is not superior to subtotal esophagectomy with regard to HRQL.     

Impact of the Reconstruction Method on Delayed Gastric Emptying After Pylorus-Preserving Pancreaticoduodenectomy: A Prospective Randomized Study

Background

Delayed gastric emptying (DGE) is of considerable concern in patients undergoing pylorus-preserving pancreaticoduodenectomy (PPPD). Prolonged hospital stay, increased cost, and decreased quality of life add on to interventions needed to treat DGE. This study was conducted to determine if performing duodenojejunostomy via the antecolic rather than the retrocolic route improved incidence of DGE.

Methods

Patients undergoing PPPD between April 2007 and November 2009 were randomized for either antecolic or retrocolic reconstruction of the duodenojejunostomy. DGE was then assessed by clinical criteria on postoperative day (POD) 10. A paracetamol absorption test was also administered with a liquid meal, and serial plasma levels of intestinal peptides were measured.

Results

Overall, 64 patients were amenable for analysis: 36 in the antecolic group and 28 in the retrocolic group. The incidences of DGE on POD 10 were 17.6 and 23.1 % (antecolic vs. retrocolic, respectively) (p = 0.628). The two groups did not differ in regard to their median (interquartile range) postoperative hospital length of stay [13.0 (10.0–17.5) vs. 12.5 (11.0–17.0) days; p = 0.446], time to regular diet [5 (5–7) vs. 5 (4–6) days; p = 0.353], or morbidity (52.9 vs. 50.0 %; p = 0.777). The median length of nasogastric tube decompression was similar in the two groups [4 (3–7) vs. 3 (3–5) days; p = 0.600]. Levels of paracetamol and glucagon-like peptide-1 were markedly decreased in patients with DGE.

Conclusions

Antecolic reconstruction after PPPD does not improve the occurrence/the incidence of DGE and is similar to retrocolic reconstruction with regard to secondary outcome parameters.     

Optimization of Manufacturing Parameters and Tensile Specimen Geometry for Fused Deposition Modeling (FDM) 3D-Printed PETG

Additive manufacturing provides high design flexibility, but its use is restricted by limited mechanical properties compared to conventional production methods. As technology is still emerging, several approaches exist in the literature for quantifying and improving mechanical properties. In this study, we investigate characterizing materials’ response of additive manufactured structures, specifically by fused deposition modeling (FDM). A comparative analysis is achieved for four different tensile test specimens for polymers based on ASTM D3039 and ISO 527-2 standards. Comparison of specimen geometries is studied with the aid of computations based on the Finite Element Method (FEM). Uniaxial tensile tests are carried out, after a careful examination of different slicing approaches for 3D printing. We emphasize the effects of the chosen slicer parameters on the position of failures in the specimens and propose a simple formalism for measuring effective mechanical properties of 3D-printed structures.     

Surface Modifications of Titanium Aluminium Vanadium Improve Biocompatibility and Osteogenic Differentiation Potential

Osteogenic cells are strongly influenced in their behaviour by the surface properties of orthopaedic implant materials. Mesenchymal stem and progenitor cells (MSPCs) migrate to the bone–implant interface, adhere to the material surface, proliferate and subsequently differentiate into osteoblasts, which are responsible for the formation of the bone matrix. Five surface topographies on titanium aluminium vanadium (TiAl₆V₄) were engineered to investigate biocompatibility and adhesion potential of human osteoblasts and the changes in osteogenic differentiation of MSPCs. Elemental analysis of TiAl₆V₄ discs coated with titanium nitride (TiN), silver (Ag), roughened surface, and pure titanium (cpTi) surface was analysed using energy-dispersive X-ray spectroscopy and scanning electron microscopy. In vitro cell viability, cytotoxicity, adhesion behaviour, and osteogenic differentiation potential were measured via CellTiter-Glo, CytoTox, ELISA, Luminex^® technology, and RT-PCR respectively. The Ag coating reduced the growth of osteoblasts, whereas the viability of MSPCs increased significantly. The roughened and the cpTi surface improved the viability of all cell types. The additive coatings of the TiAl₆V₄ alloy improved the adhesion of osteoblasts and MSPCs. With regard to the osteogenic differentiation potential, an enhanced effect has been demonstrated, especially in the case of roughened and cpTi coatings.