- Email: [email protected]
TPSDose43: A new TG-43 based dose calculation code for brachytherapy
228
Abstracts / Physica Medica 32 (2016) 222–250
organs at risk (eyeball, mucosa, etc). The thickness of these plates should be selected in accordance to the radioactive source used for brachytherapy i.e. 6 mm for (192)Ir and 10 mm for (60) Co [5]. Lead plates must be removable. They shouldn’t be present during CT scans if we want to limit the number of artifacts in CT images. The plates must be replaced before the first fraction of brachytherapy.
A layer of silicone was placed on the gypsum cast – it’s thickness directly above the planning target volume (PTV) was approximately 5 mm. In the remaining area it was more than 5 mm and more than 10 mm in the area where the applicator would be fixed/stabilised.
When the surface of the applicator was dry OncoSmart ProGuide Needles were inserted above the PTV. The needles were parallel to each other and the distance between adjacent needles ranged from 3 to 7 mm. The needles covered the whole target volume defined by the radiation oncologist.[6]
The applicators were covered with another layer of silicone and the remaining parts of the mask were also filled with this material in order to improve its durability. The mask is usually used from 8 to 10 days of treatment.[7]
So prepared mask should be left to dry completely, which may take even 24 h. This period can be shortened by leaving the mask in an air-conditioned room. Than the mask should be carefully removed from the gypsum cast. The specialist should verify if the mask is correctly prepared. Fiducial markers were placed on the borders of the lesion in order to facilitate the process of defining the planning target volume on CT images. We selected markers carefully because we wanted to avoid any changes in mask positioning. There is another solution used in difficult to reach sites i.e. cutting the inner layer of silicone and inserting the marker inside this cut. However, these cuts may need an additional thin layer of silicone to close them. Than the mask was placed on the patient and fixed additionally with elastic dressings like Codofix or special Velcro tape for tracheal tubes or oxygen cannulas e.g. Posey foam trach tie. Markers for CT/ MRI examinations provided by the manufacturer of OncoSmart ProGuide Needles were placed in the needles. CT scout view allowed to define the range of CT scan and assess adhesion of the mask. CT images were sent to the treatment planning system TPS (Oncentra) and the treatment plan was prepared. It was impossible to define any shape and size of protective plates in our TPS therefore dose values for organs at risks were smaller in reality and differences corresponded to plates’ thickness and the material they were made of. Protective plates should be repositioned on the mask before the first fraction of brachytherapy. They shouldn’t affect the shape of the mask on the side of patient’s skin. In order to have full control over the dose delivered to the planning target volume as well as organs at risk, especially when the eyeball is in a close proximity, in vivo dosimetry should be performed during the first fraction at least. [8] MOSFET detectors may be used for this purpose. Micro-MOSFET detectors are very useful for small (approximately 1 mm2) and difficult to reach surfaces. Examples presenting the use of individual applicators for HDR brachytherapy: Fig 1. A patient with multifocal head and neck cancer. Fig 2. Silicone impressions for a patient with multifocal head and neck cancer.
Fig 3. A patient with multifocal head and neck cancer - CT images and reconstructions in different planes (A,B,C) and a 3D reconstruction (D). Fig 4. A patient with submandibular cancer. Fig 5. A patient with submandibular cancer - CT images and reconstructions in different planes (A,B,C) and a 3D reconstruction(D). Fig 6. A patient with locally advanced squamous cell carcinoma of the nose. Fig 7. A patient with locally advanced squamous cell carcinoma of the nose - CT images and reconstructions in different planes (A, B, C) and a 3D reconstruction(D).
References 1. Guix B, Finestres F, Tello J, et al.. Treatment of skin carcinomas of the face by high-dose-rate brachytherapy and custom-made surface molds. Int J Radiat Oncol Biol Phys 2000;47(1):95–102. 2. Aplicator Guide, Applicators and Accessories for HDR & PDR Brachytherapy, Nucletron BV; 2011. 3. Mazeron J, Ardiet J, Haie-Méder C. GEC-ESTRO recommendations for brachytherapy for head and neck squamous cell carcinomas. Radiother Oncol 2009;91:150–6. 4. Matys R, Kubicka-Mendak I, Łyczek J. Pictorial essay penile cancer brachytherapy HDR mould technique used at the Holycross Cancer Center. J Contemp Brachyther 2011;3(4):224–9. 5. Baltas Krieger, Zamboglou. The physics of modern brachytherapy for oncology. IOP Publishing.; 2006. 6. Musmacher J, Ghaly M, Satchwill K. High dose rate brachytherapy with surface applicators: treatment for nonmelanomatous skin cancer. Journal of Clinical oncology, 2006 ASCO annual meeting proceedings Part I. vol 24, No. 18S (June 20 Supplement); 2006. p. 15543. 7. Owczarek G, Białas B, Smolska B, et al.. Our experience of mold brachytherapy technique for basal cell carcinoma of the face. J Contemp Brachyther 2009;1(3):188–9. 8. Sabbas AM, Kulidzhanov FG, Presser J, et al.. HDR brachytherapy with surface applicators: technical considerations and dosimetry. Technol Cancer Res Treat 2004;3(3):259–67.. Jun. http://dx.doi.org/10.1016/j.ejmp.2016.07.469
TPSDOSE43: A NEW TG-43 BASED DOSE CALCULATION CODE FOR BRACHYTHERAPY G. Yegin *, S. Sariaydin Celal Bayar University, Faculty of Science and Letters, Physics Dept., Manisa, Turkey ⇑ Corresponding author. Introduction. TG-43 formalism is a brachytherapy dose calculation method recommended by AAPM in1995. Purpose. To develop and make available a TG-43 based dose calculation code for testing or validating dose distributions from other brachytherapy dose calculation engines such as model based dose calculation algorithms (MBDCA). Materials and methods. TPSDose43 can be used to produce 3d dose distributions around brachytherapy sources by using TG-43 formalism. A user is allowed to provide new TG-43 data sets for any source/seed model. It is optional to use either 1d or 2d formalism. In a geometry, multiple sources can be placed at different locations or else one source can move among different dwell points as it does in the routine treatment planning systems. In 2d dose calculations, the orientation of a source can be taken into account. The code was written in C++.
Abstracts / Physica Medica 32 (2016) 222–250
Results. Dose outputs from TPSDose43 were compared against a well-known Monte Carlo code BrachyDose in certain scenarios where the environment medium is water. Both results were in a very good agreement. Conclusion. From our test results we concluded that TPSDose43 is fast, flexible and a simple to use brachytherapy dose calculation program. Also, it is a good candidate of a dose comparison tool for MBDCAs. Disclosure. This study is partly supported by The Scientific and Technological Research Council of Turkey (TUBITAK) under project number: 213E028. http://dx.doi.org/10.1016/j.ejmp.2016.07.470
DOCUMENTATION OF A NEW INTRACAVITARY APPLICATOR FOR TRANSRECTAL HYPERTHERMIA FOR PROSTATE CANCER CASES A. Nikolakopoulou a,*, C. Armpilia a, C. Antypas a, E. Karanasiou c, R. Avgousti a, E. Apostolou a, N. Uzunoglou c, I. Gogalis a, V. Kouloulias b a st 1 Radiology Dept, Medical Physics Unit, Medical School, National and Kapodistrian University of Athens, Greece b nd 2 Radiology Dept, Radiotherapy Unit, Medical School, National and Kapodistrian University of Athens, Greece c Microwave laboratory, Electrical Engineering and Computer Science, National Technical University of Athens, Greece ⇑ Corresponding author.
Introduction. A new intracavitary microwave hyperthermia applicator specially designed for heating prostate through the rectal is designed. The aim of this study is to document the new antenna operating at 433 MHz, as well as to assess the SAR distributions in terms of thermometry in a soft tissue phantom. Materials and methods. The microwave applicator consists of a dipole-type l/2, a reflector and a cooling liquid. To evaluate the SAR distribution the applicator was inserted into the gel-phantom box that mimics the dielectric properties of the normal tissue. The applicator is connected to the power unit to generate the electromagnetic field, which propagates across the antenna. The temperature distribution is detected with a calibrated thermometer, which is implanted into specific locations of the phantom. Results. The maximum value of the SAR is found on the surface’s central area of the antenna, located into the phantom box. The penetration depth of microwaves, defined as the depth at which the rate of SAR is the half of the maximum rate measured at the surface of the antenna, was calculated to be 3 cm. Our measurements confirm the role of the reflector to direct the microwaves towards in a certain area in contrast to other treatment devices which direct SAR distribution symmetrically. Conclusion. The 2-D SAR characteristics of a new designed applicator were investigated. Our experimental measurements showed that it can be used effectively as a treatment device for prostate cancer demonstrating a clear advantage of other similar devices. http://dx.doi.org/10.1016/j.ejmp.2016.07.471
IMPACT OF MR GEOMETRIC DISTORTION ON BRACHYTHERAPY IN CERVICAL CANCER Tarraf Torfeh, Rabih Hammoud *, Ana Vasic, Satheesh Paloor, Suparna Chandramouli, Souha Aouadi, Primoz Petric, Noora Al-Hammadi Department of Radiation Oncology, National Center for Cancer Care & Research (NCCCR), Hamad Medical Corporation, Doha, Qatar
⇑
229
Corresponding author.
Introduction. Volumetric imaging and in particular magnetic resonance (MR) has replaced the 2D imaging for brachytherapy treatment planning. However it is recognized that MR images suffer from geometric distortions which can have an impact on target and OARs DVH parameters due to high dose gradient in brachytherapy applications. Objective. To assess the potential dosimetric impact of MR geometric distortion on the brachytherapy treatment planning for cervical cancer. Materials and methods. MR dataset for 15 cervical cancer patients were acquired based on GEC ESTRO recommendations. Structures were delineated on the paraaxial images and treatment plans were generated using OncentraTM TPS. In-house software was developed to calculate the deformable registration between CT and MR images of a control point based phantom and to derive a distortion map of the MR system. Geometrically corrected images were then generated by applying the inverse of the distortion map. Structures were copied and adapted to the corrected datasets and the treatment plans recomputed. Dose Volume Histograms (DVH) were evaluated for High Risk CTV (HRCTV), bladder, rectum, and sigmoid. Results. Mean geometric distortions were less than 0.5 mm over a Field Of View (FOV) of 350 mm. Differences in D100 and D90 were less than 2% for HRCTV. Differences in D2cc were less than 4% for bladder, rectum, and sigmoid. Preliminary results showed that, for all organs, less than 4% of deviation was observed for D100 and D90. Conclusions. For an FOV of 350 mm, MR geometric distortion has no significant dosimetric impact on DVH parameters in brachytherapy for cervical cancer. Disclosure. Authors have nothing to disclose. http://dx.doi.org/10.1016/j.ejmp.2016.07.472
IN VIVO MEASUREMENTS FOR BIOKINETIC AND MONTE CARLO SIMULATIONS OF ABSORBED DOSE IN PAEDIATRIC PATIENTS USING RADIOPHARMACEUTICALS J. Costa a,*, P.Teles a, R. Parafita b, A. Canudo b, D.C. Costa b, P. Vaz a a
Grupo de Proteção e Segurança Radiológica, Centro de Ciências e Tecnologias Nucleares (C2TN), CTN/IST, Polo de Loures. Bobadela, Portugal b Medicina Nuclear/Radiofarmacologia – Champalimaud Centre for the Unknown, Fundação Champalimaud, Lisboa, Portugal ⇑ Corresponding author. Introduction. The use of radiopharmaceuticals implies calculation of absorbed doses according to MIRD methodology. However, particularly in children, other parameters are thought to be important and determinant for dose calculations. Amongst these are the pharmacokinetics characteristics of each radiotracer and their relationship with organ physiology and pathology, and the patients’ anatomical characteristics. Therefore, there is a need to improve dosimetric calculations based on other algorithms taking into account those variables. Purpose. Improve 99mTc-DMSA and 99mTc-MAG3 calculated absorbed doses in children after intravenous administration for diagnostic purposes. Gamma camera and in vivo measurements were used to assess the biokinetic data. The specific absorbed fraction (SAF) values are estimated via Monte Carlo simulations and scaled VOXEL phantoms. Materials and methods. In vivo measurements were mathematically analysed in order to obtain a value for the activity as function of time. The simulations were performed using MCNPX and two paediatric VOXEL phantoms (BABY and CHILD) which were scaled to fit several anatomical parameters, such as body weight, height and kidney mass, amongst others.
Abstracts / Physica Medica 32 (2016) 222–250
organs at risk (eyeball, mucosa, etc). The thickness of these plates should be selected in accordance to the radioactive source used for brachytherapy i.e. 6 mm for (192)Ir and 10 mm for (60) Co [5]. Lead plates must be removable. They shouldn’t be present during CT scans if we want to limit the number of artifacts in CT images. The plates must be replaced before the first fraction of brachytherapy.
A layer of silicone was placed on the gypsum cast – it’s thickness directly above the planning target volume (PTV) was approximately 5 mm. In the remaining area it was more than 5 mm and more than 10 mm in the area where the applicator would be fixed/stabilised.
When the surface of the applicator was dry OncoSmart ProGuide Needles were inserted above the PTV. The needles were parallel to each other and the distance between adjacent needles ranged from 3 to 7 mm. The needles covered the whole target volume defined by the radiation oncologist.[6]
The applicators were covered with another layer of silicone and the remaining parts of the mask were also filled with this material in order to improve its durability. The mask is usually used from 8 to 10 days of treatment.[7]
So prepared mask should be left to dry completely, which may take even 24 h. This period can be shortened by leaving the mask in an air-conditioned room. Than the mask should be carefully removed from the gypsum cast. The specialist should verify if the mask is correctly prepared. Fiducial markers were placed on the borders of the lesion in order to facilitate the process of defining the planning target volume on CT images. We selected markers carefully because we wanted to avoid any changes in mask positioning. There is another solution used in difficult to reach sites i.e. cutting the inner layer of silicone and inserting the marker inside this cut. However, these cuts may need an additional thin layer of silicone to close them. Than the mask was placed on the patient and fixed additionally with elastic dressings like Codofix or special Velcro tape for tracheal tubes or oxygen cannulas e.g. Posey foam trach tie. Markers for CT/ MRI examinations provided by the manufacturer of OncoSmart ProGuide Needles were placed in the needles. CT scout view allowed to define the range of CT scan and assess adhesion of the mask. CT images were sent to the treatment planning system TPS (Oncentra) and the treatment plan was prepared. It was impossible to define any shape and size of protective plates in our TPS therefore dose values for organs at risks were smaller in reality and differences corresponded to plates’ thickness and the material they were made of. Protective plates should be repositioned on the mask before the first fraction of brachytherapy. They shouldn’t affect the shape of the mask on the side of patient’s skin. In order to have full control over the dose delivered to the planning target volume as well as organs at risk, especially when the eyeball is in a close proximity, in vivo dosimetry should be performed during the first fraction at least. [8] MOSFET detectors may be used for this purpose. Micro-MOSFET detectors are very useful for small (approximately 1 mm2) and difficult to reach surfaces. Examples presenting the use of individual applicators for HDR brachytherapy: Fig 1. A patient with multifocal head and neck cancer. Fig 2. Silicone impressions for a patient with multifocal head and neck cancer.
Fig 3. A patient with multifocal head and neck cancer - CT images and reconstructions in different planes (A,B,C) and a 3D reconstruction (D). Fig 4. A patient with submandibular cancer. Fig 5. A patient with submandibular cancer - CT images and reconstructions in different planes (A,B,C) and a 3D reconstruction(D). Fig 6. A patient with locally advanced squamous cell carcinoma of the nose. Fig 7. A patient with locally advanced squamous cell carcinoma of the nose - CT images and reconstructions in different planes (A, B, C) and a 3D reconstruction(D).
References 1. Guix B, Finestres F, Tello J, et al.. Treatment of skin carcinomas of the face by high-dose-rate brachytherapy and custom-made surface molds. Int J Radiat Oncol Biol Phys 2000;47(1):95–102. 2. Aplicator Guide, Applicators and Accessories for HDR & PDR Brachytherapy, Nucletron BV; 2011. 3. Mazeron J, Ardiet J, Haie-Méder C. GEC-ESTRO recommendations for brachytherapy for head and neck squamous cell carcinomas. Radiother Oncol 2009;91:150–6. 4. Matys R, Kubicka-Mendak I, Łyczek J. Pictorial essay penile cancer brachytherapy HDR mould technique used at the Holycross Cancer Center. J Contemp Brachyther 2011;3(4):224–9. 5. Baltas Krieger, Zamboglou. The physics of modern brachytherapy for oncology. IOP Publishing.; 2006. 6. Musmacher J, Ghaly M, Satchwill K. High dose rate brachytherapy with surface applicators: treatment for nonmelanomatous skin cancer. Journal of Clinical oncology, 2006 ASCO annual meeting proceedings Part I. vol 24, No. 18S (June 20 Supplement); 2006. p. 15543. 7. Owczarek G, Białas B, Smolska B, et al.. Our experience of mold brachytherapy technique for basal cell carcinoma of the face. J Contemp Brachyther 2009;1(3):188–9. 8. Sabbas AM, Kulidzhanov FG, Presser J, et al.. HDR brachytherapy with surface applicators: technical considerations and dosimetry. Technol Cancer Res Treat 2004;3(3):259–67.. Jun. http://dx.doi.org/10.1016/j.ejmp.2016.07.469
TPSDOSE43: A NEW TG-43 BASED DOSE CALCULATION CODE FOR BRACHYTHERAPY G. Yegin *, S. Sariaydin Celal Bayar University, Faculty of Science and Letters, Physics Dept., Manisa, Turkey ⇑ Corresponding author. Introduction. TG-43 formalism is a brachytherapy dose calculation method recommended by AAPM in1995. Purpose. To develop and make available a TG-43 based dose calculation code for testing or validating dose distributions from other brachytherapy dose calculation engines such as model based dose calculation algorithms (MBDCA). Materials and methods. TPSDose43 can be used to produce 3d dose distributions around brachytherapy sources by using TG-43 formalism. A user is allowed to provide new TG-43 data sets for any source/seed model. It is optional to use either 1d or 2d formalism. In a geometry, multiple sources can be placed at different locations or else one source can move among different dwell points as it does in the routine treatment planning systems. In 2d dose calculations, the orientation of a source can be taken into account. The code was written in C++.
Abstracts / Physica Medica 32 (2016) 222–250
Results. Dose outputs from TPSDose43 were compared against a well-known Monte Carlo code BrachyDose in certain scenarios where the environment medium is water. Both results were in a very good agreement. Conclusion. From our test results we concluded that TPSDose43 is fast, flexible and a simple to use brachytherapy dose calculation program. Also, it is a good candidate of a dose comparison tool for MBDCAs. Disclosure. This study is partly supported by The Scientific and Technological Research Council of Turkey (TUBITAK) under project number: 213E028. http://dx.doi.org/10.1016/j.ejmp.2016.07.470
DOCUMENTATION OF A NEW INTRACAVITARY APPLICATOR FOR TRANSRECTAL HYPERTHERMIA FOR PROSTATE CANCER CASES A. Nikolakopoulou a,*, C. Armpilia a, C. Antypas a, E. Karanasiou c, R. Avgousti a, E. Apostolou a, N. Uzunoglou c, I. Gogalis a, V. Kouloulias b a st 1 Radiology Dept, Medical Physics Unit, Medical School, National and Kapodistrian University of Athens, Greece b nd 2 Radiology Dept, Radiotherapy Unit, Medical School, National and Kapodistrian University of Athens, Greece c Microwave laboratory, Electrical Engineering and Computer Science, National Technical University of Athens, Greece ⇑ Corresponding author.
Introduction. A new intracavitary microwave hyperthermia applicator specially designed for heating prostate through the rectal is designed. The aim of this study is to document the new antenna operating at 433 MHz, as well as to assess the SAR distributions in terms of thermometry in a soft tissue phantom. Materials and methods. The microwave applicator consists of a dipole-type l/2, a reflector and a cooling liquid. To evaluate the SAR distribution the applicator was inserted into the gel-phantom box that mimics the dielectric properties of the normal tissue. The applicator is connected to the power unit to generate the electromagnetic field, which propagates across the antenna. The temperature distribution is detected with a calibrated thermometer, which is implanted into specific locations of the phantom. Results. The maximum value of the SAR is found on the surface’s central area of the antenna, located into the phantom box. The penetration depth of microwaves, defined as the depth at which the rate of SAR is the half of the maximum rate measured at the surface of the antenna, was calculated to be 3 cm. Our measurements confirm the role of the reflector to direct the microwaves towards in a certain area in contrast to other treatment devices which direct SAR distribution symmetrically. Conclusion. The 2-D SAR characteristics of a new designed applicator were investigated. Our experimental measurements showed that it can be used effectively as a treatment device for prostate cancer demonstrating a clear advantage of other similar devices. http://dx.doi.org/10.1016/j.ejmp.2016.07.471
IMPACT OF MR GEOMETRIC DISTORTION ON BRACHYTHERAPY IN CERVICAL CANCER Tarraf Torfeh, Rabih Hammoud *, Ana Vasic, Satheesh Paloor, Suparna Chandramouli, Souha Aouadi, Primoz Petric, Noora Al-Hammadi Department of Radiation Oncology, National Center for Cancer Care & Research (NCCCR), Hamad Medical Corporation, Doha, Qatar
⇑
229
Corresponding author.
Introduction. Volumetric imaging and in particular magnetic resonance (MR) has replaced the 2D imaging for brachytherapy treatment planning. However it is recognized that MR images suffer from geometric distortions which can have an impact on target and OARs DVH parameters due to high dose gradient in brachytherapy applications. Objective. To assess the potential dosimetric impact of MR geometric distortion on the brachytherapy treatment planning for cervical cancer. Materials and methods. MR dataset for 15 cervical cancer patients were acquired based on GEC ESTRO recommendations. Structures were delineated on the paraaxial images and treatment plans were generated using OncentraTM TPS. In-house software was developed to calculate the deformable registration between CT and MR images of a control point based phantom and to derive a distortion map of the MR system. Geometrically corrected images were then generated by applying the inverse of the distortion map. Structures were copied and adapted to the corrected datasets and the treatment plans recomputed. Dose Volume Histograms (DVH) were evaluated for High Risk CTV (HRCTV), bladder, rectum, and sigmoid. Results. Mean geometric distortions were less than 0.5 mm over a Field Of View (FOV) of 350 mm. Differences in D100 and D90 were less than 2% for HRCTV. Differences in D2cc were less than 4% for bladder, rectum, and sigmoid. Preliminary results showed that, for all organs, less than 4% of deviation was observed for D100 and D90. Conclusions. For an FOV of 350 mm, MR geometric distortion has no significant dosimetric impact on DVH parameters in brachytherapy for cervical cancer. Disclosure. Authors have nothing to disclose. http://dx.doi.org/10.1016/j.ejmp.2016.07.472
IN VIVO MEASUREMENTS FOR BIOKINETIC AND MONTE CARLO SIMULATIONS OF ABSORBED DOSE IN PAEDIATRIC PATIENTS USING RADIOPHARMACEUTICALS J. Costa a,*, P.Teles a, R. Parafita b, A. Canudo b, D.C. Costa b, P. Vaz a a
Grupo de Proteção e Segurança Radiológica, Centro de Ciências e Tecnologias Nucleares (C2TN), CTN/IST, Polo de Loures. Bobadela, Portugal b Medicina Nuclear/Radiofarmacologia – Champalimaud Centre for the Unknown, Fundação Champalimaud, Lisboa, Portugal ⇑ Corresponding author. Introduction. The use of radiopharmaceuticals implies calculation of absorbed doses according to MIRD methodology. However, particularly in children, other parameters are thought to be important and determinant for dose calculations. Amongst these are the pharmacokinetics characteristics of each radiotracer and their relationship with organ physiology and pathology, and the patients’ anatomical characteristics. Therefore, there is a need to improve dosimetric calculations based on other algorithms taking into account those variables. Purpose. Improve 99mTc-DMSA and 99mTc-MAG3 calculated absorbed doses in children after intravenous administration for diagnostic purposes. Gamma camera and in vivo measurements were used to assess the biokinetic data. The specific absorbed fraction (SAF) values are estimated via Monte Carlo simulations and scaled VOXEL phantoms. Materials and methods. In vivo measurements were mathematically analysed in order to obtain a value for the activity as function of time. The simulations were performed using MCNPX and two paediatric VOXEL phantoms (BABY and CHILD) which were scaled to fit several anatomical parameters, such as body weight, height and kidney mass, amongst others.