32P Wpływ kompensatorów i osłon na rozkład dawki w ciele podczas napromieniowania całego ciała

Napromienianie całego ciała (TBI) było stosowane u 21 chorych (dzieci) przed przeszczepianiem szpiku kostnego. Celem napromieniania było zniszczenie komórek nowotworowych rozsianych w całym ciele, wywołanie immunoupresji i wytworzenie miejsca pod nowoprzeszczepiony szpik. Głównym problemem TBI było uzyskanie równomiernego rozkładu dawki w ciele przy jednoczesnym obniżeniu dawki w płucach.CelCelem pracy była poprawa jednorodności dawki wewnątrz ciała poprzez wprowadzenie w obszar wiązki filtru promieniowania i indywidualnych kompensatorów.MetodaNapromienianie przeprowadzono przy użyciu pól bocznych z odległości 275 cm i przednio-tylnych (AP/PA) z odległości 183 cm. Dawka łączna 12.6 Gy była podawana w 8 frakcjach w ciągu 4 kolejnych dni. 8.2 Gy podano z pól bocznych (moc dawki 6.7 cGy/min), a 4.4 Gy z pól AP/PA (moc dawki 17.7 cGy/min).Podczas pól bocznych niejednorodności w rozkładzie dawki były wynikiem różnic w odległości od źródła do poszczególnych części ciała (np. do głowy, bioder), zaburzenia promieniowania przez układ kolimacyjny, różnic w grubości ciała (biodra 27 cm, głowa 17 cm) i różnic w gęstości tkanek (płuca).Zastosowano filtr promieniowania o schodkowym kształcie w celu wyrównania profilu wiązki oraz indywidualne kompensatory tkankopodobne w celu kompensacji różnic w grubości przekrojów i różnic gęstości tkanek (w obszarze głowy 3,5 cm, szyi 5,5 cm, kolan, stóp po 6,5 cm).WynikiŚrednie odchylenie od dawki zadanej dla 10 wybranych przekrojów referencyjnych wyniosło dla pola otwartego odpowiednio −3.2% (bok) i −5.4% (środek), a dla pola z filtrem i kompensatorami −1.3% i −2.0%. Odchylenie standardowe dla pola otwartego wynosiło odpowiednio 7.1% (bok) i 17.0% (środek), a po wprowadzeniu filtru i kompensatorów 4.8% (bok) i 9.8% (środek).WnioskiWprowadzenie filtra i kompensatorów poprawia jednorodność dawki mierzoną odchyleniem standardowym w obrębie referencyjnych przekrojów oraz wyrównuje niedobory dawki mierzone średnim odchyleniem od dawki zadanej

Beam filter and compensators during total body irradiation on Cobalt-60

Total body irradiation performed with a combination of lateral and anterior – posterior fields was used prior to bone marrow transplantation. Dose discrepancies in a body during lateral fields were caused by different distances from the source to the particular body parts, different thickneses of body sections in ten reference levels and differences in interior tissues density. To improve dose homogeneity a radiation filter and individual compensators were used in the beam.Dose deviations at the points representing patient's side and midline were counted and measured in a water tank and then for a patient taken as an example. Deviations were measured for the open field, filtered field and for the field with the filter and compensators.For a patient taken as an example standard dose deviations for all ten sections were 17.0% in midline and 7.1% in side for an open beam and 9.8%, 4.8% respectively for the beam with the filter and compensators. Mean percent deviations from the dose in the central axis were −3.1% (midline) and −2.5% (side) for open, and −0.1% and 0.9% for the filtered and compensated beams, respectively

Dosimetric verification of dose optimisation algorithm during endovascular brachytherapy of the peripheral vessels

AbstractAimDosimetric verification of the dose optimisation model used in endovascular brachytherapy, evaluation of the optimised dose distributions using elaborated indices.BackgroundThe equipment used for standard radiotherapy is used in vascular brachytherapy for prevention of restenosis after angioplasty.Material and MethodA paraffin-wax phantom, thermoluminescent detectors and MD-55 Gafchromic® films were used for dose measurements. The edge dose index (EDI), central dose index (CDI) and treatment length index (TLI) were introduced to compare dose distributions calculated and measured.ResultsObtained values (p>0.05) show no statistically significant differences between calculated doses and measured doses. EDI values showed improvement in dose homogeneity on the edges of the application after optimisation. After optimisation CDI values from 0.9% to 1.6% for calculated and from −1.8% to 3.1% for measured showed improvement in dose homogeneity in the central part of the application. Observed values of TLI from 3% to 21% for calculated doses and from 7% to 24% for doses measured by Gafchromic® films showed increase of RIL for optimised treatment plans.Conclusions1/ The designed phantom allowed repeatable dosimetric verification of dose distributions in endovascular brachytherapy. 2/ Measurements with thermoluminescent detectors and Gafchromic films proved the accuracy of the calculation algorithm in endovascular brachytherapy conditions. 3/ Elaborated indices were found to be a useful tool in describing dose homogeneity. They allowed the process of optimisation to be controlled and thus an increase in dose homogeneity by 30% at the edges and by 7% in the middle of the treated volume to be achieved

The influence of legislative changes on quality and costs in radiotherapy

SummaryBackgroundOn 24 December 2002, in compliance with Euratom Directive 97/43, the Minister of Health issued an ordinance on rules and regulations of safe application of ionising radiation for medical purposes and methods of internal control over observance of the rules and regulations. The ordinance obliges managers of institutions which apply ionising radiation for medical purposes (radiotherapy, X-ray diagnostics, nuclear medicine) to implement, maintain and develop the Quality Management System (QMS). On 25 August 2005, the Minister of Health issued an ordinance on rules and regulations of safe application of ionising radiation with reference to all types of medical exposure which overruled the ordinance of 24.12.2002.AimThe purpose of this paper was (i) the comparative analysis of the aforementioned ordinances in the context of three selected aspects: internal audits, external audits and the system of quality management, and (ii) the analysis of the rise in labour costs, services, depreciation and materials in 2002–2005, as a result of the implementation of the aforementioned legal rules and regulations.Materials and MethodsA comparative analysis of the two a fore mentioned ordinances of the Minister of Health was performed: concerning (i) external clinical audits, (ii) internal clinical audits and (iii) requirements of the quality management system. The total cost of implementation of such rules and regulations (in particular the cost of the Quality Management System) has been calculated based on an analysis of labour costs, depreciation, materials and services in 2002–2005.ResultsLegislative changes in the scope of safe application of ionising radiation for medical purposes enhance not only the organisation of health care institutions applying radiotherapy, but also the rise in costs of the organisations as a result of implementation of the changes, e.g. through (i) the costs of salaries for work groups or consulting companies implementing QMS, (ii) costs of external services, dosimetric audits by independent calibration laboratories, (iii) costs of QMS certification, (iv) awards and bonuses for internal auditors, (v) costs of service contracts, etc.ConclusionsThe implementation of the quality management system, modernisation of technical infrastructure, systematic controls and measurements of apparatuses and procedures, more effective work organisation, repeatability, regularity and homogeneity not only enhance the quality of medical service, but also the costs in radiotherapy