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[P233] Investigation of the response of cylindrical ionization chamber in non-reference conditions when using high-energy photon beams
Abstracts / Physica Medica 52 (2018) 99–187
and 53 mm could not be reproduced by any of the algorithms. Including both phantom and patient cases, the best and worst algorithm succeeded in visually acceptable DIRs, corresponding to CMS<2.0 mm and DSCP0.87, for 18/25 and 12/25 cases respectively. Visually acceptable DIRs resulted in absorbed dose deviations in the evaluated dose parameters of 63.6 percentage units. Conclusions. Visually acceptable DIRs were achievable for moving structures with constant volume and shifts 630 mm in phantoms and shifts616 mm in patients. Visually acceptable DIRs implied dose deviations 63.6 percentage units on patient CT-images of the thorax region. https://doi.org/10.1016/j.ejmp.2018.06.518
[P233] Investigation of the response of cylindrical ionization chamber in non-reference conditions when using high-energy photon beams Peter Andersson a, John Swanpalmer b, Roumiana Chakarova b,* a Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Gothenburg, Sweden b Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Department of Radiation Physics, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden ⇑ Corresponding author.
Purpose. To investigate the response of CC13 cylindrical ionization chamber in non-reference conditions with focus on the penumbra region and the depth of maximum dose when using high-energy photon beams. This chamber is used for beam data measurements and also for pre-treatment quality assurance procedures for dynamic treatments. Methods. Measurements and Monte Carlo calculations are performed, employing a Varian iX Linac (6 MV photon beam), at the depths of 15 mm and 100 mm for the field sizes of 20 20 mm2; 20100 mm2 and 100100 mm2. The Monte Carlo model is developed using the egs-chamber in the EGSnrc package. Conversion factors are calculated relating the absorbed dose to air in the air cavity of the chamber to the absorbed dose to water through using: (a) water volume equal to the air cavity of the chamber, (b) 111 mm3 water voxel representing point dose. Corresponding correction factors, Cw/chamber and Cw,point/chamber, are determined to quantify the variations in the conversion factors. Results. Agreement within 3.5%/0.5 mm is obtained between the measurements and calculations. The correction factors for a chamber position at the central axis of the beam and at the center of the field penumbra are between 0.98 and 1.02 for all field sizes and depths examined. The largest corrections are seen for off-axis positions 3 mm beyond the penumbra center where Cw,point/chamber varies between 0.54 and 0.71 for the depth of 100 mm and 0.45 and 0.58 for the depth of 15 mm indicating an overestimation of the absorbed dose to water when using the CC13 chamber. Cw,point/chamber factors up to 1.27 are obtained in regions close to the penumbra inside the 2020 mm2 and 20100 mm2 fields indicating an underestimation of the absorbed dose to water. The maximum variation of the Cw/ 2 chamber factors is between 0.70 and 1.06 for the 2020 mm field at the depth of 15 mm. Conclusions. Uncorrected chamber response of the CC13 chamber, or similar, results in under or overestimation of the absorbed dose to water at positions inside or outside of the beam close to the penumbra for small as well as large field sizes. https://doi.org/10.1016/j.ejmp.2018.06.519
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[P234] Waiting and treatment time analysis for radiation therapy treatments Eva Maria Ambroa Rey a,*, David Navarro Giménez a, Julia GarcíaMiguel Quiroga a, Roberto Gomez Pardos a, Antoni Ramirez b, Montserrat Colomer Truyols a a Medical Physics Unit, Radiation Oncology Department, Consorci Sanitari de Terrassa, Terrassa (Barcelona), Spain b Consorci Sanitari de Terrassa, Radiation Oncology, Terrassa, Spain ⇑ Corresponding author.
Purpose. To analyze the total treatment time and waiting time for the patients in our radiation oncology department. Method. Patient treatment and waiting times were analyzed for a total of 3937 appointments during the last 3 years in three linear accelerators (Agility, Synergy and Infinity). With Elekta’s MOSAIQ Radiation Oncology information system (version 2.60, IMPAC Medical Systems), all patient information is collected and accessible, so you can create exhaustive reports. For this study a report including arrival time, wait time, treatment time and total time in the department was created for all radiotherapy treatments. Agility and Synergy are located in the same site, but Infinity is in a satellite location. Agility machine is dedicated mostly to VMAT treatments, meanwhile Synergy carry on only 3D treatments and Infinity performs VMAT as well as 3D treatments. Results. Medium total treatment time was 15.1 min; median was 13.9 min. On average, patients arrive 30.5 min before the scheduled time. Therefore mean total time in the department was 45.6 min. In addition, for each machine, results were as follow: Agility: 1214 appointments. Average (minutes): early arrival 44.7, total time 45.3, wait time 30.6 and treatment time 14.8. Only 9.6% of the appointments arrived late. Synergy: 1541 appointments. Average (minutes): early arrival 36.8, total time 45.5, wait time 29.8 and treatment time 15.7. A 9.4% of the appointments arrived late. Infinity: 1182 appointments. Average (minutes): early arrival 22.0, total time 46.1, wait time 31.3 and treatment time 14.8. A 21.9% of the appointments arrived late. Conclusions. In summary, patient waiting time and total time are very similar for the three machines. Despite the fact all VMAT treatments have a daily cone beam CT for patient positioning; medium treatment time for Agility is similar to the other machines which perform less VMAT treatments. Furthermore, many patients depend on public/private transport to arrive to their appointments; Infinity machine has the higher rate of late appointments, which could be related with a problem in the transport system. Therefore these results not only provide feedback but also could allow detecting problems and consequently improving waiting times for the patients. https://doi.org/10.1016/j.ejmp.2018.06.520
[P236] Rapid Arc versus a new sectorial sliding window IMRT template in radiotherapy brain treatments: Lens sparing Samantha Cornacchia a,*, Rosangela Errico a, Elena Pierpaoli a, Giovanni Simeone a, Giorgia Califano b, Rocchina Caivano b, Vincenzo Fusco c, Giuseppe Guglielmi d a
Asl Bt, Medical Physics, Barletta, Italy Irccs-Crob, Medical Physics, Rionero IN Vulture, Potenza, Italy c Irccs-Crob, Radiation Oncology, Rionero IN Vulture, Potenza, Italy d University of Foggia, Radiology, Foggia, Italy ⇑ Corresponding author. b
and 53 mm could not be reproduced by any of the algorithms. Including both phantom and patient cases, the best and worst algorithm succeeded in visually acceptable DIRs, corresponding to CMS<2.0 mm and DSCP0.87, for 18/25 and 12/25 cases respectively. Visually acceptable DIRs resulted in absorbed dose deviations in the evaluated dose parameters of 63.6 percentage units. Conclusions. Visually acceptable DIRs were achievable for moving structures with constant volume and shifts 630 mm in phantoms and shifts616 mm in patients. Visually acceptable DIRs implied dose deviations 63.6 percentage units on patient CT-images of the thorax region. https://doi.org/10.1016/j.ejmp.2018.06.518
[P233] Investigation of the response of cylindrical ionization chamber in non-reference conditions when using high-energy photon beams Peter Andersson a, John Swanpalmer b, Roumiana Chakarova b,* a Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Gothenburg, Sweden b Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Department of Radiation Physics, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden ⇑ Corresponding author.
Purpose. To investigate the response of CC13 cylindrical ionization chamber in non-reference conditions with focus on the penumbra region and the depth of maximum dose when using high-energy photon beams. This chamber is used for beam data measurements and also for pre-treatment quality assurance procedures for dynamic treatments. Methods. Measurements and Monte Carlo calculations are performed, employing a Varian iX Linac (6 MV photon beam), at the depths of 15 mm and 100 mm for the field sizes of 20 20 mm2; 20100 mm2 and 100100 mm2. The Monte Carlo model is developed using the egs-chamber in the EGSnrc package. Conversion factors are calculated relating the absorbed dose to air in the air cavity of the chamber to the absorbed dose to water through using: (a) water volume equal to the air cavity of the chamber, (b) 111 mm3 water voxel representing point dose. Corresponding correction factors, Cw/chamber and Cw,point/chamber, are determined to quantify the variations in the conversion factors. Results. Agreement within 3.5%/0.5 mm is obtained between the measurements and calculations. The correction factors for a chamber position at the central axis of the beam and at the center of the field penumbra are between 0.98 and 1.02 for all field sizes and depths examined. The largest corrections are seen for off-axis positions 3 mm beyond the penumbra center where Cw,point/chamber varies between 0.54 and 0.71 for the depth of 100 mm and 0.45 and 0.58 for the depth of 15 mm indicating an overestimation of the absorbed dose to water when using the CC13 chamber. Cw,point/chamber factors up to 1.27 are obtained in regions close to the penumbra inside the 2020 mm2 and 20100 mm2 fields indicating an underestimation of the absorbed dose to water. The maximum variation of the Cw/ 2 chamber factors is between 0.70 and 1.06 for the 2020 mm field at the depth of 15 mm. Conclusions. Uncorrected chamber response of the CC13 chamber, or similar, results in under or overestimation of the absorbed dose to water at positions inside or outside of the beam close to the penumbra for small as well as large field sizes. https://doi.org/10.1016/j.ejmp.2018.06.519
167
[P234] Waiting and treatment time analysis for radiation therapy treatments Eva Maria Ambroa Rey a,*, David Navarro Giménez a, Julia GarcíaMiguel Quiroga a, Roberto Gomez Pardos a, Antoni Ramirez b, Montserrat Colomer Truyols a a Medical Physics Unit, Radiation Oncology Department, Consorci Sanitari de Terrassa, Terrassa (Barcelona), Spain b Consorci Sanitari de Terrassa, Radiation Oncology, Terrassa, Spain ⇑ Corresponding author.
Purpose. To analyze the total treatment time and waiting time for the patients in our radiation oncology department. Method. Patient treatment and waiting times were analyzed for a total of 3937 appointments during the last 3 years in three linear accelerators (Agility, Synergy and Infinity). With Elekta’s MOSAIQ Radiation Oncology information system (version 2.60, IMPAC Medical Systems), all patient information is collected and accessible, so you can create exhaustive reports. For this study a report including arrival time, wait time, treatment time and total time in the department was created for all radiotherapy treatments. Agility and Synergy are located in the same site, but Infinity is in a satellite location. Agility machine is dedicated mostly to VMAT treatments, meanwhile Synergy carry on only 3D treatments and Infinity performs VMAT as well as 3D treatments. Results. Medium total treatment time was 15.1 min; median was 13.9 min. On average, patients arrive 30.5 min before the scheduled time. Therefore mean total time in the department was 45.6 min. In addition, for each machine, results were as follow: Agility: 1214 appointments. Average (minutes): early arrival 44.7, total time 45.3, wait time 30.6 and treatment time 14.8. Only 9.6% of the appointments arrived late. Synergy: 1541 appointments. Average (minutes): early arrival 36.8, total time 45.5, wait time 29.8 and treatment time 15.7. A 9.4% of the appointments arrived late. Infinity: 1182 appointments. Average (minutes): early arrival 22.0, total time 46.1, wait time 31.3 and treatment time 14.8. A 21.9% of the appointments arrived late. Conclusions. In summary, patient waiting time and total time are very similar for the three machines. Despite the fact all VMAT treatments have a daily cone beam CT for patient positioning; medium treatment time for Agility is similar to the other machines which perform less VMAT treatments. Furthermore, many patients depend on public/private transport to arrive to their appointments; Infinity machine has the higher rate of late appointments, which could be related with a problem in the transport system. Therefore these results not only provide feedback but also could allow detecting problems and consequently improving waiting times for the patients. https://doi.org/10.1016/j.ejmp.2018.06.520
[P236] Rapid Arc versus a new sectorial sliding window IMRT template in radiotherapy brain treatments: Lens sparing Samantha Cornacchia a,*, Rosangela Errico a, Elena Pierpaoli a, Giovanni Simeone a, Giorgia Califano b, Rocchina Caivano b, Vincenzo Fusco c, Giuseppe Guglielmi d a
Asl Bt, Medical Physics, Barletta, Italy Irccs-Crob, Medical Physics, Rionero IN Vulture, Potenza, Italy c Irccs-Crob, Radiation Oncology, Rionero IN Vulture, Potenza, Italy d University of Foggia, Radiology, Foggia, Italy ⇑ Corresponding author. b