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261 Oral Quality control audits in radiotherapy in Poland
Proffered papers
60% receive radiotheray either as part of their primary treatment or in connection with recurrences or palliation. Carrying out well established quality control procedures are essential in reducing errors during the process of dose delivery in radiotherapy. There are today about 170 radiotherapy centres in Brazil with 100 linear accelerators and 130 60Co gamma-ray units, As result, the high patient working-load raises concerns on the quality of the delivered cancer treatments. Based on this, the State University of Rio de Janeiro (UERJ) partially sponsored by the IAEA, in agreement with the Brazilian Societies of Radiation Oncology and Medical Physics and in close cooperation with the ESTROEQUAL project has set up a Quality Assurance Dosimetry Network (PQD) to check the dose in both reference and non- reference conditions. This program covers photon and electron beams in accordance with thee EQUAL methodology and acceptance criteria. It also uses a phantom to check the dose at 10 cm in air and at 2 cm in water for 1921r HDR brachytherapy sources, The present work reports the results of first year of experience, the general organization of the TLD network in Brazil, the results of the comparisons and cross calibrations of its measuring systems with the ESTRO and IAEA standards. The traceability of the measuring systems has been carefully kept in order to assure a high degree of accuracy to the measured values, The PQD is now participating in a joint effort with the IAEA-EQUAL to develop a TLD based QA dosimetry audits system for non-reference conditions including the off-central beam axis. 261
Oral
Quality control audits in radiotherapy in Poland W, B~Jlski, J. Rostkowska, M. Kania, B. Gwiazdowska Medical Physics Department, Cancer Centre - Institute of Oncology, W a r saw, Poland The Secondary Standard Dosimetry Laboratory (SSDL) of the Medical Physics Department of the Centre of Oncotogy in Warsaw is a continuation of the Radiation Measurements Laboratory created in 1937, following the suggestions of Marie Curie, the founder of the institute. The SSDL is a member of the tAENWHO international network of such laboratories and is periodically audited by the IAEA. It is in charge of calibration of all radiotherapy dosimeters in Poland, and it also co-ordinates all activities crried out in radiotherapy quality assurance programmes nation-wide. The results of the efforts, aimed at the development of a quality audit programme and methodology in radiotherapy, are presented. The External Audit Group (EAG) was set-up according to the recommendations of the International Atomic Energy Agency (IAEA). It was incorporated into the SSDL. The EAG is in charge of the management of the project and organization of the TLD measurements. The SSDL takes the responsibilities of the metrological aspects of the programme. In Poland there exist 21 radiotherapy centres, and a total number of 64 megavoltage units. The first audit, supported by the IAEA, was done during the period between 1991-93 in 11 centres, tt yielded interesting results on the magnitude and sources of uncertainties of dose measurements. Between 1993-95 a nation-wide TLD check for photon beams in the framework of the EROPAQ project was performed. Since 1999 regular yearly audit runs have been carried out, covering Co-60, photon and electron beam output measurements in standard conditions. The SSDL also carries out external audits during preparatory stages of multi-centre prospective clinical trials. This requires extensive checks of a number of parameters of radiotherapy equipment and measurements of dose in non-standard conditions in order to test the 3-D radiotherapy treatment planning systems. Calibration of dosimeters remains the essential task of the SSDL but carrying out external audits, elaboration of recommendations and regulations, and creation of a comprehensive data-base of radiotherapy centres is also very effective in assuring the quality of radiotherapy nation-wide. The results of the TLD postal audits indicate an improvement of dose determination in audites radiotherapy centres in subsequent audit runs. 262
Oral
A quality assurance phantom for treatment planning, dosimetry and portal imaging for participating centres in the MRC RT-01 trial in dose escalated prostate radiotherapy (ISRCTN 47772397) R. Moore 1, A. Wardngton 1, E. Aird2, A. Tipper I , K. Walker2 1Royal Marsden Hospital, Medical Physics, London, United Kingdom 2Mount Vernon Hospital, Medical Physics, Northwood, United Kingdom RTO1QA committee, Institution Clinical Trials Unit, UK Medical Research council
Friday, 20 September 2002 $87
The aim of the phantom design is to provide a tool to assess the dosimetric and geometric aspects of static shaped field conformal prostate radiotherapy as per the UK MRC RT-01 Trial. At each hospital the phantom is put through as many of the stages in the planning and treatment chain as practicable using the protocol for patients in the RT-01 trial with similar setup errors as for a real patient. A perspex water phantom containing tissue equivalent plastic inserts to simulate the prostate gland and surrounding bony anatomy was designed and constructed. The phantom geometry was based on CT data from an 'average patient'. Two alternative prostate inserts were manufactured: (i) to enable the outlining of a CT data set from a cylindrical insert containing two slightly different density tissue equivalent plastics, and (ii) a duplicate prostate gland made from MCP alloy. Ionisation chamber cavities were included in the CT insert and simulated bone femoral heads for dose verification. The MCP alloy insert is substituted for plan Verification when used in the simulator and for portal image verification on the treatment linac and has the advantage of a quick check. Information on relative and absolute dosimetry was obtained with a 0.125cc PTW ion chamber. The dose was measured at 13 points on 5 transverse levels and compared with the planning system calculations. The tolerance on the comparison differed for the points. The average relative dose near the isocentre (excluding output variation) was found to be + 0.9% + 0.3% (mean +_seom). The measurements in the central plane showed good agreement with the calculated doses, and offaxis measurements showed reasonable agreement. The point most frequently out of tolerance was near multiple field edges. It was a sensitive dosimetric indication of setup error. Point measurements in reference conditions were also made using a calf brated PTW Farmer type chamber. The uncertainty on this is not yet forreally evaluated. At most of the centres visited, the alanine dosimetry service of the UK National Physical Laboratory was used to estimate dose near the isocentre within the phantom. Use of alanine provided an independent check on the ionometry. The methods were in reasonable agreement.
60% receive radiotheray either as part of their primary treatment or in connection with recurrences or palliation. Carrying out well established quality control procedures are essential in reducing errors during the process of dose delivery in radiotherapy. There are today about 170 radiotherapy centres in Brazil with 100 linear accelerators and 130 60Co gamma-ray units, As result, the high patient working-load raises concerns on the quality of the delivered cancer treatments. Based on this, the State University of Rio de Janeiro (UERJ) partially sponsored by the IAEA, in agreement with the Brazilian Societies of Radiation Oncology and Medical Physics and in close cooperation with the ESTROEQUAL project has set up a Quality Assurance Dosimetry Network (PQD) to check the dose in both reference and non- reference conditions. This program covers photon and electron beams in accordance with thee EQUAL methodology and acceptance criteria. It also uses a phantom to check the dose at 10 cm in air and at 2 cm in water for 1921r HDR brachytherapy sources, The present work reports the results of first year of experience, the general organization of the TLD network in Brazil, the results of the comparisons and cross calibrations of its measuring systems with the ESTRO and IAEA standards. The traceability of the measuring systems has been carefully kept in order to assure a high degree of accuracy to the measured values, The PQD is now participating in a joint effort with the IAEA-EQUAL to develop a TLD based QA dosimetry audits system for non-reference conditions including the off-central beam axis. 261
Oral
Quality control audits in radiotherapy in Poland W, B~Jlski, J. Rostkowska, M. Kania, B. Gwiazdowska Medical Physics Department, Cancer Centre - Institute of Oncology, W a r saw, Poland The Secondary Standard Dosimetry Laboratory (SSDL) of the Medical Physics Department of the Centre of Oncotogy in Warsaw is a continuation of the Radiation Measurements Laboratory created in 1937, following the suggestions of Marie Curie, the founder of the institute. The SSDL is a member of the tAENWHO international network of such laboratories and is periodically audited by the IAEA. It is in charge of calibration of all radiotherapy dosimeters in Poland, and it also co-ordinates all activities crried out in radiotherapy quality assurance programmes nation-wide. The results of the efforts, aimed at the development of a quality audit programme and methodology in radiotherapy, are presented. The External Audit Group (EAG) was set-up according to the recommendations of the International Atomic Energy Agency (IAEA). It was incorporated into the SSDL. The EAG is in charge of the management of the project and organization of the TLD measurements. The SSDL takes the responsibilities of the metrological aspects of the programme. In Poland there exist 21 radiotherapy centres, and a total number of 64 megavoltage units. The first audit, supported by the IAEA, was done during the period between 1991-93 in 11 centres, tt yielded interesting results on the magnitude and sources of uncertainties of dose measurements. Between 1993-95 a nation-wide TLD check for photon beams in the framework of the EROPAQ project was performed. Since 1999 regular yearly audit runs have been carried out, covering Co-60, photon and electron beam output measurements in standard conditions. The SSDL also carries out external audits during preparatory stages of multi-centre prospective clinical trials. This requires extensive checks of a number of parameters of radiotherapy equipment and measurements of dose in non-standard conditions in order to test the 3-D radiotherapy treatment planning systems. Calibration of dosimeters remains the essential task of the SSDL but carrying out external audits, elaboration of recommendations and regulations, and creation of a comprehensive data-base of radiotherapy centres is also very effective in assuring the quality of radiotherapy nation-wide. The results of the TLD postal audits indicate an improvement of dose determination in audites radiotherapy centres in subsequent audit runs. 262
Oral
A quality assurance phantom for treatment planning, dosimetry and portal imaging for participating centres in the MRC RT-01 trial in dose escalated prostate radiotherapy (ISRCTN 47772397) R. Moore 1, A. Wardngton 1, E. Aird2, A. Tipper I , K. Walker2 1Royal Marsden Hospital, Medical Physics, London, United Kingdom 2Mount Vernon Hospital, Medical Physics, Northwood, United Kingdom RTO1QA committee, Institution Clinical Trials Unit, UK Medical Research council
Friday, 20 September 2002 $87
The aim of the phantom design is to provide a tool to assess the dosimetric and geometric aspects of static shaped field conformal prostate radiotherapy as per the UK MRC RT-01 Trial. At each hospital the phantom is put through as many of the stages in the planning and treatment chain as practicable using the protocol for patients in the RT-01 trial with similar setup errors as for a real patient. A perspex water phantom containing tissue equivalent plastic inserts to simulate the prostate gland and surrounding bony anatomy was designed and constructed. The phantom geometry was based on CT data from an 'average patient'. Two alternative prostate inserts were manufactured: (i) to enable the outlining of a CT data set from a cylindrical insert containing two slightly different density tissue equivalent plastics, and (ii) a duplicate prostate gland made from MCP alloy. Ionisation chamber cavities were included in the CT insert and simulated bone femoral heads for dose verification. The MCP alloy insert is substituted for plan Verification when used in the simulator and for portal image verification on the treatment linac and has the advantage of a quick check. Information on relative and absolute dosimetry was obtained with a 0.125cc PTW ion chamber. The dose was measured at 13 points on 5 transverse levels and compared with the planning system calculations. The tolerance on the comparison differed for the points. The average relative dose near the isocentre (excluding output variation) was found to be + 0.9% + 0.3% (mean +_seom). The measurements in the central plane showed good agreement with the calculated doses, and offaxis measurements showed reasonable agreement. The point most frequently out of tolerance was near multiple field edges. It was a sensitive dosimetric indication of setup error. Point measurements in reference conditions were also made using a calf brated PTW Farmer type chamber. The uncertainty on this is not yet forreally evaluated. At most of the centres visited, the alanine dosimetry service of the UK National Physical Laboratory was used to estimate dose near the isocentre within the phantom. Use of alanine provided an independent check on the ionometry. The methods were in reasonable agreement.