Linear energy transfer characterization of five gel dosimeter formulations for electron and proton therapeutic beams.

Gel dosimeters, including radiochromic types like Fricke, as well as polymer formulations, are considered to be the only reliable option for accurate 3D dosimetry. Nevertheless, their implementation in daily clinical quality assurance still remains strongly limited for a few high specialized radiotherapy centres. Although gel dosimeters present very good water-equivalence due to their inherent chemical and isotopic compositions, addressing the corresponding dosimetry outputs is highly challenging, needing careful assessment in terms of the different radiation qualities involved in the mixed field. Accurate estimations of the linear energy transfer for each gel dosimeter formulation stands as a baseline for further accurate dose deconvolution in mixed radiation fields. The present study reports on the linear energy transfer characterization of five different gel dosimeter formulations, Fricke, Itabis, Magic, Nipam, and Pagat, for electron and proton therapeutic beams as obtained by Monte Carlo approaches, along with experimental results for validation purposes. The linear energy transfer, as a function of beam quality and penetration depth, is obtained for electron and proton therapeutic beams remarking the presence of non-negligible variations, which need to be accounted for a further accurate implementation of gel dosimetry as well as for precise dose deconvolution in mixed radiation fields.

[Endoprosthetic management of patients with hip arthrodesis]. / Die endoprothetische Versorgung von Patienten mit Hüftarthrodese.

PURPOSE: Purpose of this retrospective study was to investigate the long-term results of total hip replacement in patients with hip arthrodesis. METHODS: Between 1976 and 1986 conversion of a earlier performed arthrodesis of the hip to total hip replacement was carried out in a total of 20 patients. 15 of these have been followed up postoperatively for an average of 15.7 years. The main preoperative symptoms were pain affecting the lumbar spine, the ipsilateral knee and/or both hip joints. In two cases, the arthrodesis has fractured. RESULTS: With the exception of one female patient, all the patients expressed satisfaction with the postoperative results, pain having been alleviated or eliminated. The difference in leg length presenting preoperatively in 12 patients was partly or completely equalized in ten cases. Specific physiotherapy over a period of several months resulted in an appreciable increase in muscular power in all patients. Postoperatively ten patients had a slight, five a pronounced limp, while 11 patients needed a walking aid. Recurrent dislocations occurred in one patient. We observed one aseptic loosening of the cup after 10 years. CONCLUSION: The results of the study show that conversion of surgically ankylosed hip joints to total hip replacement makes good sense. Provided that the indication is established with care, this major surgical procedure represents a suitable method, not only of improving the patient's quality of life, but also, and in particular, of at least appreciably improving the symptoms developing after hip arthrodesis. There seems no increased rate of aseptic implant loosening.