[en] Purpose: for radiation treatment of patients with cervical cancer and a high risk for paraaortic lymph node involvement, an easy three-dimensional (3-D) conformal irradiation technique (partial half-beam [PHB]) for protection of organs at risk, especially of renal tissue, was developed. Patients and methods: in five consecutive female patients a computed tomography scan was performed. Dose-volume histograms of the renal tissue and other organs at risk were analyzed for PHB, three other 3-D conformal techniques, and an intensity-modulated radiotherapy (IMRT) technique. Results: the PHB technique reduced the renal volume and volumes of other organs at risk exposed to radiation doses when comparing all patients to the other 3-D conformal techniques. With use of the IMRT technique more renal tissue volume received very low radiation doses (≤ 6.8 Gy) whereas the D₁₀ was lower than with the PHB technique. Conclusion: in female patients with cervical cancer and high risk for paraaortic lymph node involvement, the use of the PHB technique is recommended to reduce renal radiation exposure, if no IMRT technique should be applied. The PHB technique is very easily and fast applicable. (orig.)

[en] Background and Purpose: The use of a rectal balloon leads to a protection of the posterior rectal wall in irradiation of prostate cancer. The purpose of this analysis was to quantitatively assess the optimal volume in rectal balloons concerning rectal dose sparing in different clinical target volumes (CTVs) in prostate cancer irradiation. Patients and Methods: 14 patients with localized prostate cancer undergoing external beam radiotherapy were investigated. The prostate, the entire and the proximal seminal vesicles were delineated as CTV. Treatment plans without a rectal balloon and with a rectal balloon inflated with 40 ml (six patients) or 60 ml air (eight patients) were generated for each CTV and compared concerning rectal dose volume histograms. Results: The use of a rectal balloon filled with 40 ml air led to no significant advantage in radiation exposure of the rectal wall in all CTVs. The use of a rectal balloon filled with 60 ml air resulted in a significant decrease of the exposed rectal wall volume in all CTVs with a reduced estimated risk for chronic toxicity in case of inclusion of the proximal or entire seminal vesicles into the CTV. Conclusion: The use of a rectal balloon filled with 60 ml air led to a significantly decreased proportion of the irradiated rectal wall for all CTVs. This volume filled in rectal balloons is therefore recommended for use. In case of irradiation of the prostate without the seminal vesicles, the use of a rectal ballon should be considered carefully concerning the patients' imaginable discomfort using a rectal balloon and a questionable advantage concerning the estimated risk for chronic toxicity. (orig.)

[en] Purpose: National and international dosimetry protocols assume a position accuracy for ionization chambers of less than 0.2mm. To follow this precept the manufacturer PTW-Freiburg introduced a positioning assistance system (TRUFIX) for their particular ion chambers. Aim of this study is an experimental investigation of the positioning uncertainties for ROOS-type ionization chambers. Methods: For all measurements a linear accelerator Elekta Synergie was used. The experiments were performed in a water-phantom. To collimate the electron beam a 10×10cm"2 applicator was installed. All measured depth dose curves were normalized to their maximum. In all cases the TRUFIX system was applied for chamber positioning. For the first measurement series, to determine the positioning reproducibility of a ROOS chamber, one person placed the chamber three times in a 6 MeV electron beam. The mean value of this three measurements was the reference for further six random persons who repeated this procedure. The results were compared for different depths (R_5_0, z_r_e_f and R_p). To investigate the impact of different individual chambers of the same type 10 different ROOS chambers were placed by the same person in a 6, 12 and 18MeV electron beam and the measured reference depths z_r_e_f were compared. Results: The absolute positioning reproducibility is less than 0.1mm for the same person. The positioning uncertainties are increasing up to +/−0.3mm if different persons perform the chamber’s positioning within the water phantom. The comparison of the 10 different ROOS chambers resulted in reference depths z_r_e_f with deviations in the range of +/−0.45mm for all energies. Conclusion: The position accuracy of 0.2mm can be fulfilled with the TRUFIX system. The comparison of the 10 different ROOS ionization chambers showed noticeable deviations in the determined reference depth. The impact of a positioning uncertainty of about 0.3–0.4mm on the total perturbation correction will be considered.

[en] In modern radiotherapy the verification of complex treatments plans is often performed in inhomogeneous or even anthropomorphic phantoms. For dose verification small detectors are necessary and therefore alanine detectors are most suitable. Though the response of alanine for a wide range of clinical photon energies in water is well know, the knowledge about the influence of the surrounding phantom material on the response of alanine is sparse. Therefore we investigated the influence of twenty different surrounding/phantom materials for alanine dosimeters in clinical photon fields via Monte Carlo simulations. The relative electron density of the used materials was in the range $n_e/n_{e,\text{w}}=0.20$ up to 1.69, covering almost all materials appearing in inhomogeneous or anthropomorphic phantoms used in radiotherapy. The investigations were performed for three different clinical photon spectra ranging from 6 to 25 MV-X and Co-60 and as a result a perturbation correction $k_{\text{env}}$ depending on the environmental material was established. The Monte Carlo simulation show, that there is only a small dependence of $k_{\text{env}}$ on the phantom material and the photon energy, which is below  ±0.6%. The results confirm the good suitability of alanine detectors for in-vivo dosimetry. (note)

[en] Introduction. - Curative therapy for patients with small-cell lung cancer (SCLC) is based on multidrug chemotherapy combinations and radiotherapy. After a long time follow-up, the aim of the study was to evaluate the efficacy and toxicity of sequential chemo-radiotherapy and the effect of prophylactic cranial irradiation (PCI). Methods. - From 1995-2005, 96 patients with SCLC (64 limited-disease [LD], 32 extensive-disease [ED]; median age 61 years [range 39-79]) were treated at our department with varying chemotherapy regimens and sequential mediastinal radiotherapy (50 Gy + 10 Gy boost in case of residual disease after chemotherapy). Afterwards, 15 patients with LD, good general condition and at least partial response after local treatment received PCI (30 Gy). Results. - After a median follow-up of 78.6 months, 20 patients remained alive (20.8%, median survival time 18.2 months). The 2-/5-year overall survival rates were 33.8% and 12.6%, the 2-/5-year loco-regional control rates were 30.3% and 24.5%, respectively. Distant metastases occurred in 43 patients (24 cerebral). Cerebral metastasis occurred in 6.7% and 27.2% of the patients with PCI and without PCI respectively. Only tumor stage showed a statistically significant impact on overall survival and loco-regional control in multivariate analysis. Radiotherapy was well tolerated. Grade 3/4 toxicity occurred in seven patients. Prognosis of patients with SCLC remains poor. Administration of PCI in selected patients bears a decrease in the incidence of cerebral metastases. Alternative chemotherapy schemes as well as irradiation schemes and techniques should be the substance of future randomized trials. (authors)

[en] Aims and purpose: Radiotherapy is an essential and reliable element of the treatment armamentarium in oncology. Numerous rules, regulations, and protocols minimize the associated risks. It can, however, never be excluded that errors in the treatment delivery chain result in inadequate tumor doses or unnecessary damage to organs at risk. A legal framework governs the management of such incidents. The most important European and North American regulations are reported. Results: Various directives issued by the European Union are differently implemented nationally. This applies particularly to the characterization of incidents that must be reported to authorities. Reporting thresholds, audit systems, and the extent of the integration of voluntary reporting systems vary. Conclusion: Radiotherapy incidents are dealt with differently on an international level. Changes are to be expected based on the European Basic Safety Standards Directive that is currently being prepared and will have to be implemented nationally in due course. (orig.)

[en] Differential cross sections for Compton scattering from the free proton at Θ_γ'^lab=130.7 deg. in the energy region from 200 MeV to 410 MeV and for quasi-free Compton scattering from the proton bound in the deuteron at Θ_γ'^lab=148.8 deg. in the energy region from 200 MeV to 290 MeV have been measured. The free proton data are in agreement with dispersion-theory predictions based on standard parameters. The difference of the proton polarizabilities has been extracted from the quasi-free data. Our result, αbar-βbar=[9.1±1.7(stat+syst)±1.2(mod)]x10^-4 fm³, is in reasonable agreement with the world average of the free proton data if the backward spin polarizability γ_π is taken to be -37.6x10^-4 fm⁴ as predicted by dispersion theory in agreement with many theoretical calculations. This implies that quasi-free Compton scattering may also be used to determine the electromagnetic polarizabilities of the neutron. No indication has been found of a recently suggested new contribution to γ_π

[en] A number of national and international societies published recommendations regarding the required equipment and manpower assumed to be necessary to treat a number of patients with radiotherapy. None of these recommendations were based on actual time measurements needed for specific radiotherapy procedures. The German Society of Radiation Oncology (DEGRO) was interested in substantiating these recommendations by prospective evaluations of all important core procedures of radiotherapy in the most frequent cancers treated by radiotherapy. The results of the examinations of radiotherapy with intensity-modulated radiation therapy (IMRT) in patients with different tumor entities are presented in this manuscript. Four radiation therapy centers [University Hospital of Marburg, University Hospital of Giessen, University Hospital of Berlin (Charite), Klinikum rechts der Isar der Technischen Universitaet Muenchen] participated in this prospective study. The workload of the different occupational groups and room occupancies for the core procedures of radiotherapy were prospectively documented during a 2-month period per center and subsequently statistically analyzed. The time needed per patient varied considerably between individual patients and between centers for all the evaluated procedures. The technical preparation (contouring of target volume and organs at risk, treatment planning, and approval of treatment plan) was the most time-consuming process taking 3 h 54 min on average. The time taken by the medical physicists for this procedure amounted to about 57 %. The training part of the preparation time was 87 % of the measured time for the senior physician and resident. The total workload for all involved personnel comprised 74.9 min of manpower for the first treatment, 39.7 min for a routine treatment with image guidance, and 22.8 min without image guidance. The mean room occupancy varied between 10.6 min (routine treatment without image guidance) and 23.7 min (first treatment with image guidance). The prospective data presented here allow for an estimate of the required machine time and manpower needed for the core procedures of radiotherapy in an average radiation treatment with IMRT. However, one should be aware that a number of necessary and time-consuming activities were not evaluated in the present study. (orig.)

[en] On the basis of correct Hounsfield unit to electron density calibration, cone-beam computed tomography (CBCT) data provide the opportunity for retrospective dose recalculation in the patient. Therefore, the consequences of translational positioning corrections and of morphological changes in the patient anatomy can be quantified for prostate cancer patients. The organs at risk were newly contoured on the CBCT data sets of 7 patients so as to evaluate the actual applied dose. The daily dose to the planning target volume (PTV) was recalculated with and without the translation data, which result from the real patient repositioning. A CBCT-based dose recalculation with uncertainties less than 3 % is possible. The deviations between the planning CT and the CBCT without the translational positioning correction vector show an average dose difference of - 8 % inside the PTV. An inverse proportional relation between the mean bladder dose and the actual volume of the bladder could be established. The daily applied dose to the rectum is about 1-54 % higher than predicted by the planning CT. A dose calculation based on CBCT data is possible. The daily positioning correction of the patient is necessary to avoid an underdosage in the PTV. The new contouring of the organs at risk - the bladder and rectum - allows a better appraisal to be made of the total applied dose to these organs. (orig.)

[en] The differential cross sections for Compton scattering from the proton have been measured at MAMI with three different detector setups. There is a good agreement among all the results. The theoretical calculation based on dispersion relations shows that there is no drastic change necessary in the parameters of this approach