Search

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.

Purpose: Rotational IMRT is a new technique, whose value still has to be assessed. We evaluated its adequacy for the treatment of head and neck (H&N) cancer compared to the well-established step-and-shoot IMRT., Materials and Methods: A total of 15 patients, who were treated with either IMRT (13 patients) or VMAT (2 patients) in the H&N region, were chosen. For each patient, a treatment plan with the respective other technique was calculated. To compare the resulting dose distributions, the dose-volume histograms (DVHs) were evaluated. To quantify the differences, a new quality index (QI) was introduced, as a measure of the planning target volume (PTV) coverage and homogeneity. A conformity function (CF) was defined to estimate normal tissue sparing., Results: The QI for VMAT amounts to 36.3, whereas for IMRT the mean value is 66.5, indicating better PTV coverage as well as less overdosage for the rotational technique. While the sparing of organs at risk (OAR) was similar for both techniques, the CF shows a significantly better sparing of healthy tissue for all doses with VMAT treatment., Conclusions: VMAT results in dose distributions for H&N patients that are at least comparable with treatments performed with step-and-shoot IMRT. Two new tools to quantify the quality of dose distributions are presented and have proven to be useful.

Background and Purpose: In spite of various efforts perihilar cholangiocellular carcinoma (Klatskin tumour) has still a bad prognosis. The treatment of patients with inoperable Klatskin tumours by stereotactic fractionated radiotherapy (SFRT) was analysed retrospectively. PATIENTS, METHODS AND MATERIALS: In our department 13 patients were treated for Klatskin tumours by SFRT (32-56 Gy, 3 x 4 Gy/week) from 1998 to 2008. The treatment technique was developed from stereotactic body frame radiotherapy to image guided (IGRT) stereotactic radiotherapy with control of patient positioning by cone beam computer tomography (CBCT). 6/13 patients received additional chemotherapy before or after SFRT., Results: A median survival of 33.5 (6.6-60.4) months after diagnosis was reached by SFRT. The median time of freedom from tumour progression was 32.5 (6.1-60.4, last patient died without tumour progression) months. The therapy was tolerated very well. Nausea was the most common side effect. 5/13 patients suffered from recurrent cholangitis caused and enhanced by the primary tumour and drainages or stents in the bile ducts., Conclusions: In the context of reaching local control being still the main problem of Klatskin tumour patients, SFRT seems to be a very promising method for the treatment of these tumours., (Copyright 2010 Elsevier Ireland Ltd. All rights reserved.)

Purpose: Part 2 of this study presents the results of the clinical audits of the "Arztliche Stelle" (AS) concerning process quality in the radiation therapy units in Baden-Württemberg, Germany., Material and Methods: The process quality of nine main test groups (laws, organizations, technical equipment, GMP [Good Medical Practice] principles, radiotherapy, radiation procedure, follow-up, discharge report, physics) were questioned by the AS commission and evaluated in a four-stage classification (1-4; none to grave deficiencies)., Results: In 18 institutes (81%), the medical and physical-technical inspection, including radiation protection for patients and staff, revealed very high to high quality, safe treatment commensurate with current standards was guaranteed once the suggestions for improvement given by the experts had been implemented. In four institutes (18%), the inspection showed a still satisfactory quality but a shorter period for reinspection was recommended. The most frequent comments/deficiencies were found in staff structures (32%), in continuous education/training for staff (32%), in informed patient consent (41%), follow-up (45%), and/or a unclearly formulated discharge report for the referring physicians (45%)., Conclusion: The medical and physical-technical examination of radiation treatment in the vast majority (81%) of the radiation therapy institutes in Baden-Württemberg showed a very high or high quality. Most of the comments and deficiencies concerned the sector of systematic continued training for staff, giving clear explanations to patients, structured follow-up, and the state of the medical discharge reports. These deficiencies, however, do not represent any immediate danger to the patient through any deficiencies in therapy. The experience gained by the AS could act as a model for quality improvement and could also be transmitted to other medical sectors to retain quality standards. The various specialist associations are called upon to gradually adopt the suggestions for quality improvements which are based on concrete as-is analyses by steadily aligning practice with theory. This would enable the steadily rising demands of quality assurance to be sustainably implemented through practicable models.

Purpose: To evaluate the structure quality (medical staff, linear accelerators, and patients) of radiotherapy units based on the clinical audits by the "Arztliche Stelle" (this institution is based on federal German law) in Baden-Württemberg., Material and Methods: External audits (performed by at least two radiation oncologists, one radiation physicist, and a member of the administration) of recently completed charts by designated reviewers using appropriate checklists developed by the federal task group ("Arztliche Stelle") were used., Results: In the interval from 2005 to 2007, 60 linear accelerators in 24 radiotherapy units served a population of approximately 10.7 million inhabitants (178,000 inhabitants/linear accelerator). 28,210 people with malignant tumors were treated in these units in 2007. These patients were served by 127 radiation oncologists, 83 radiation physicists, and 235 technologists. The ratio of patients irradiated annually to staff would become 222 (range 85-400) for a radiation oncologist, 339 for a radiation physicist (range 170-538), and 120 for a technologist (range 48-189). In five of seven departments (71%), new staff was employed following the recommendations of the auditors., Conclusion: Clinical audits by the "Arztliche Stelle" are highly effective to evaluate the structure quality of radiotherapy units. Based on these audits realistic data for staff requirements were gained. Making use of these data, guidelines for average minimum personnel necessary for good patient care were calculated. Personnel requirements may vary related to specific needs (teaching, research) of the treatment program and should be accounted for when discussing with the administration. The recommendations of the auditors of the "Arztliche Stelle" resulted in the new employment of additional staff.

Background and Purpose: Modern medical linear accelerators (linacs) are equipped with X-ray systems, which allow to check the patient's position just prior to treatment. Their usefulness for stereotactic radiosurgery (SRS) depends on how accurately they allow to determine the deviation between the actual and planned isocenter positions. This accuracy was investigated with measurements using two different phantoms (Figures 1 and 2)., Material and Methods: After precisely aligning a phantom onto the linac isocenter, two perpendicular X-rays or a cone-beam CT (CBCT) are taken, and the isocenter position is deduced from this data. The deviation of the thereby gained position from the setup isocenter is taken as a measure for the uncertainty of this method., Results: Isocenter verification with two orthogonal X-rays (Figure 4) achieves accuracies of better than 1 mm (Table 3). The distance between the isocenters of the CBCT and the linac (Figure 3) is in the order of 1 mm, but remains constant on the time scale of 1 week (Table 1) and may therefore be taken into account. The uncertainty after correction is below 0.2 mm., Conclusion: kV imaging with the patient in treatment position allows to verify the isocenter position with submillimeter precision, and therefore offers a supplemental test, suitable for SRS, which takes all positional uncertainties into account.

In view of the poor prognosis of patients with cholangiocarcinoma (CCC), there is a need for new therapeutic strategies. Inter-disciplinary therapy seems to be most promising. Radiotherapy is an effective alternative to surgery for hilar CCC (Klatskin tumors) if an adequate radiation dose can be delivered to the liver hilus. Here, we describe a patient for whom we used a stereotactic radiotherapy technique in the context of an inter-disciplinary treatment concept. We report a 45-year-old patient with a locally advanced Klatskin tumor. Explorative laparotomy showed that the tumor was not resectable. A metallic stent was implanted and the patient was treated by stereotactic radiotherapy using a body frame. A total dose of 48 Gy (3X4 Gy/wk) was administered. Therapy was well tolerated. After 32 mo, local tumor recurrence and a chest wall metastasis developed and were controlled by radio-chemotherapy. After more than 56 mo with a good quality of life, the patient died of advanced neoplastic disease. Stereotactic radiotherapy led to a long-term survival of this patient with a locally advanced Klatskin tumor. In the context of inter-disciplinary treatment concepts, this radiotherapy technique is a promising choice of treatment for patients with hilar CCC.

Background: On-site physical quality assurance (QA) was performed in the participating centers of the CHARTWEL-Bronchus trial to ensure that physical and technical treatment parameters correspond with the requirements of this trial., Material and Methods: Questionnaires were sent to the clinics to obtain information on the equipment and in-house QA policies. In addition, two phantoms with drillings for an ionization chamber were shipped with detailed instructions for CT-based treatment planning of a fixed field (RW3 phantom) and a standardized isocentric 3-field technique (Rando humanoid phantom). Using their routine treatment planning system, the participating centers performed point dose calculations for the isocenters in both phantoms and for defined points in the lungs and the spinal cord of the Rando phantom. During the on-site visit, the doses in these points and the deviation of the actual monitor calibration from the internal reference value of the department were determined. In addition, relevant geometric parameters of the accelerator were checked., Results: In the RW3 phantom, the maximum dose deviations from the prescribed value were 3.5% without correction for the actual monitor calibration and 2.1% after correction. The maximum dose deviation in the isocenter of the Rando phantom was 4.0%. To separate the influence of the treatment planning system on this deviation from other sources, all measurements in the Rando phantom were corrected for the deviations determined in the RW3 phantom. After this correction, the maximum deviation was 3.0% in the isocenter. For the other measurement points, the largest dose deviation of 7% was found in the left lung. Deviations of geometric parameters were negligible in all audited departments., Conclusion: The CHARTWEL-Bronchus physical QA program revealed a high conformity of geometric and dosimetric parameters and valid dose calculations by the CT-based treatment planning systems in all audited departments.

Long-term observations of mechanical parameters have been performed in Freiburg for the last 7 years within the quality assurance of stereotactic irradiation at linear accelerators. The deviations between the laser indication and the position of the beam isocentre are recorded, as well as parameters for the stability of the couch rotation and the additional devices for patient adjustment and beam collimation. The deviations are used for the correction of the calculated isocentre coordinates. The long-term observation of the measured values and their standard deviations allow conclusions about the quality of the measuring procedure itself, the laser adjustment, the extension of the isocentre sphere, as well as the mechanical slackness of the treatment couch and the fixation device of the stereotactic ring. The standard deviations of the isocentre position were within 0.3 to 0.8 mm, those of the measurement quality approximately 0.2 mm. The analysis of long-term observation has contributed to improvements of the equipment and of quality assurance procedures.

Using a non-invasive mask this patient fixation system for stereotactic radiotherapy allows one to perform fractionated irradiation. Measuring the statistical quantities of patient motion and positioning uncertainties and calculating its effect on a spherically symmetric dose distribution showed that there is no severe disadvantage in most cases. Only if small field-size, excentric target volume localisation and extreme proximity to an organ at risk coincides have the statistical effects to be taken into account. The greatest measured standard deviation for positioning uncertainty was 2.3 mm. Its effect on the dose distribution with a field size of 9.1 mm increases the diameter of the 80% isodose to about 115%.

Three-dimensional (3-D) radiotherapy planning is applied for the conformation therapy of a bronchial carcinoma. The treatment technique, using dynamically controlled shielding blocks, and the treatment planning procedure are described. The method has now been in clinical routine since 4 years; problems with the patient's positioning are discussed.

An irradiation phantom was used to measure dose increases using the backscatter of different materials (titanium, steel, lead, aluminium). Telecobalt-60 and 8-MV photons were used for the irradiation. The irradiation dose was measured by means of a defined X-ray film blackening. The most important parameter was to find out whether under simulated conditions, undesirable hot spots occur. We were able to demonstrate that a 12.5 to 16% increase in the radiation dose can be observed for titanium and steel at a distance of 0.45 mm from the metal specimen. A comparison between titanium and steel did not demonstrate a relevant advantage for titanium. Therefore, adjuvant percutaneous radiation therapy should not have any influence on the life of the implant, if the soft tissue layer is of sufficient thickness. The available literature is reviewed and presented in tables.

Very small electron beams show considerable reduction of the dose output factor, the therapeutically relevant range, the practical range and the therapeutically relevant field size, compared to broad beams. The first three effects were measured on the central beam axis for different quadratic field sizes and are presented in the first part of this publication. A simple field zone method for calculation of irregular shaped electron beams was developed from the different depth dose curves. The method allows the determination of the maximum dose and the 80% range with sufficient accuracy for practical purposes. The examination of the reduction of the therapeutically relevant field size and the consequences following thereof with respect to the adequate electron therapy of a small irregular target volume will be published in a second part.

The researches of Pauwels and those following him have demonstrated that the subchondral bone density distribution below the surface of a joint is a metrical parameter which mirrors the predominant stress acting on that joint. Their technique of x-ray densitometry cannot, however, be used during life. By employing computer tomography, a new method has been developed--CT-osteoabsorptiometry (CT-OAM)--which can be used to obtain the density distribution pattern in the living subject. By means of a comparative investigation on specimens which were examined both with traditional x-ray densitometry and with CT absorptiometry, it has been shown that the new method can produce the same results, but providing the great advantage to be used on the living. In addition, the density distribution pattern of the glenoid cavity has been examined in patients with various shoulder conditions, and also in gymnasts who exercise on the rings. The distribution of subchondral bone density showed different patterns in the different groups examined. Both the comparison of the methods and the subsequent study confirmed that CT osteoabsorptiometry enables assessment to be made of the individual long-term stresses acting on a living joint.