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IN VIVO DOSIMETRY IN HDR BRACHYTHERAPY FOR CERVIX CANCER
B RACHYTHERAPY: V ERIFICATION AND DOSIMETRY
Brachytherapy: dosimetry
S 139
Verification and
373 poster (Physics Track) IN VIVO DOSIMETRY IN HDR BRACHYTHERAPY FOR CERVIX CANCER. E. Bloemen- van Gurp1 1
Conclusions: Some patients show a high CV, higher than 5% which demonstrates a strong dose inter fraction variation. Our results show a high SD variation which precludes to use few CT exams and our recommendation is to use as many CT exams as you can afford.Some patients show a high CV, higher than 5% which demonstrates a strong dose inter fraction variation. Our results show a high SD variation which precludes to use few CT exams and our recommendation is to use as many CT exams as you can afford. 372 poster (Physics Track) MALIGNANT SKIN INFILTRATION: BRACHYTHERAPY TREATMENT PLANNING AND OPTIMIZATION B. Petrovic1 , B. Djuran2 , L. Rutonjski1 , O. Cudic1 , M. Erak1 1 I NSTITUTE OF O NCOLOGY, Department of Radiotherapy, Sremska Kamenica, Serbia 2 I NSTITUTE OF O NCOLOGY VOJVODINE, Department of Radiotherapy, Sremska Kamenica, Serbia
Purpose: To present method of brachytherapy irradiation of skin inflitration (lenticular metastases, basocellular carcinoma) implemented in our clinic. Materials: Treatment planning system used is Varian BrachyVision v.8.1.18. The individual moulds are prepared for each patient. The head (or thoracal) thermoplastic masks are used as base for applicators. Number and length of applicators was directed by the size of a lesion. Two orthogonal radiographs are made by the non isocentric C arm (Philips Endura). They are imported into TPS and used for reconstruction and treatment planning. Depth of dose prescription was determined from the CT scans (were applicable) or from other findings. The depth of dose prescription was calculated as depth of infiltration plus thickness of the thermoplastic mask. After volume optimization, and dose constraints satisfied, the result of calculation was reviewed and improved by dose shaper tool Results: In total 5 patients were treated till now. One had lenticular metastases (field size 25cm x 11cm), others had basocellular carcinoma of different sizes (up to the whole half of the skull). Three patients already finished treatment and had first follow up, two other are currently under treatment. First clinical results were obvious: pain relief, stoppage of bleeding, significant reduction of lesion.
MAASTRO CLINIC, Radiotherapy-Oncology, Maastricht, Netherlands
Purpose: HDR brachytherapy with iridium-192 is a frequently used technique for the treatment of patients with cervical cancer. The position of the gynecological applicator in the cervical canal can change between the imaging phase and the actual treatment, e.g. due to patient transport from the CT to the irradiation suite. As a result, deviations between the planned dose distribution and the actual dose distribution may occur. To verify the in vivo dose values in the organs at risk viz. bladder and rectum, MOSFET-dosimetry was performed. Materials: Micro-MOSFETs (TN-502RDM) and a MOSFET linear-array (TN252LA5) were used for the measurements. Calibration was performed in water. The MOSFET was placed in the center and a 192 Ir source was placed at 0◦ and 180◦ . Phantom measurements were performed to investigate the linearity and the angular dependence of the detector response. Next, measurements were performed to simulate the clinical measurements in a phantom. Measurements were performed in 2 patients during sequential fractions. A micro-MOSFET was placed in the urine catheter and a linear-array was positioned in the rectum and fixed with a home-made rectum sponge. In vivo dose values were compared to calculated dose values at these positions. Uncertainties are given as 1 SD of the mean. Results: The calibration factor was (1.19±0.02) mV/cGy for the microMOSFETs and (0.90±0.01) mV/cGy for the linear array. Phantom measurements demonstrated that the MOSFET dose response is almost linear in the clinical dose range, from 15 cGy up to 8 Gy. The angular dependence of the response is within 2% (180◦ ). The simulation of the clinical practice in a phantom demonstrated a mean result of (1±7)%. Patient in vivo measurements demonstrated an average deviation between measured and calculated doses of (-4±18)% for the bladder and (-9±15)% for the rectum. Conclusions: In vivo dosimetry is a method to register the actual dose values in the OARs and link dose values to clinical side effects. MOSFETs are potentially suitable for in vivo dosimetry during HDR brachytherapy. Deviations between the planned and actual dose values may occur due to an error in the treatment process and to a shift of the applicator in the cervical canal after the imaging procedure. Also, a deviation in dose in the organs at risk can occur due to internal motion with respect to the applicator (intestinal motion and bladder filling). 374 poster (Physics Track) THE CHOICE OF THE BEST DISPOSITION OF THE DOSE IN THE TREATMENT IN PARTIAL BREAST IRRADIATION. M. Jurczyk1 , T. Opala2 , P. Jankowski3 , J. Kobzda3 1 G INEKOLOGICZNO -P OLOZNICZY S ZPITAL K LINICZNY UM, Department of Mother’s and Child’s Health, Poznan University of Medical Sciences, Laboratory HDR, Poznan, Poland 2 G INEKOLOGICZNO -P OLOZNICZY S ZPITAL K LINICZNY UM, Department of Mother’s and Child’s Health, Poznan University of Medical Sciences, Poznan, Poland 3 G INEKOLOGICZNO -P OLOZNICZY S ZPITAL K LINICZNY UM, Department of Brachytherapy, Poznan, Poland
patient with lenticular metastases treated with brachytherapy mould Conclusions: This treatment modality is very simple, effective and with excellent outcomes (clinical and esthetical). It is easily implemented in all patients, especially in elderly people, those with cardiac problems, and all who cannot be surgically treated.ACKNOWLEDGMENTThis work has been done after the complete renovation of the brachytherapy premises and installation of new equipment at the institution, funded by IAEA (national TC project) Authors are grateful to the hosts of the IAEA fellowships in Maria Sklodowska Curie Memorial Cancer Center in Gliwice, Poland
Purpose: New trends in the treatment of breast cancer by brachytherapy proceeded by operative intervention show comparable effectiveness of PBI and WBI. Standard planning of the disposition of the doses is based on the principles of the Paris system. Materials: Theoretical comparison of the three methods of planning of the disposition of the dose with the specification of various points was carried out in the Laboratory of Brachytherapy Gynaecological and Obstetrical Clinical Hospital of University of Medical Sciences in Poznan: 1◦ method based on the 3 description points being the centre of gravity of triangles; 2◦ method based on the 1 description point being the centre of gravity of the trapezium; 3◦ method - In the centre of the tumor bad.To the analysis an applicator was chosen consisting of five needles arranged in two planes (3 + 2). The disposition of doses from the first method were accepted as the reference. Results: Uniformity Index of the tumor bad in respective methods carried out suitably: 1,40 ± 0,02; 1,28 ± 0,015; 1,11 ± 0,10.The use of the second method caused the reduction of V85 about the average 14,55 %, V100 about 19,81 % and V150 about 19,7 % in relation to above mentioned volumes in the first method. Parameters for the third method were less convenient: 24,38 %, 34,1 % and 30,51 %. Conclusions: The third method seems to be theoretically the best of irradiating the volume a the tumor bad with the simultaneous reduction of the dose in the area of the healthy tissues.
Brachytherapy: dosimetry
S 139
Verification and
373 poster (Physics Track) IN VIVO DOSIMETRY IN HDR BRACHYTHERAPY FOR CERVIX CANCER. E. Bloemen- van Gurp1 1
Conclusions: Some patients show a high CV, higher than 5% which demonstrates a strong dose inter fraction variation. Our results show a high SD variation which precludes to use few CT exams and our recommendation is to use as many CT exams as you can afford.Some patients show a high CV, higher than 5% which demonstrates a strong dose inter fraction variation. Our results show a high SD variation which precludes to use few CT exams and our recommendation is to use as many CT exams as you can afford. 372 poster (Physics Track) MALIGNANT SKIN INFILTRATION: BRACHYTHERAPY TREATMENT PLANNING AND OPTIMIZATION B. Petrovic1 , B. Djuran2 , L. Rutonjski1 , O. Cudic1 , M. Erak1 1 I NSTITUTE OF O NCOLOGY, Department of Radiotherapy, Sremska Kamenica, Serbia 2 I NSTITUTE OF O NCOLOGY VOJVODINE, Department of Radiotherapy, Sremska Kamenica, Serbia
Purpose: To present method of brachytherapy irradiation of skin inflitration (lenticular metastases, basocellular carcinoma) implemented in our clinic. Materials: Treatment planning system used is Varian BrachyVision v.8.1.18. The individual moulds are prepared for each patient. The head (or thoracal) thermoplastic masks are used as base for applicators. Number and length of applicators was directed by the size of a lesion. Two orthogonal radiographs are made by the non isocentric C arm (Philips Endura). They are imported into TPS and used for reconstruction and treatment planning. Depth of dose prescription was determined from the CT scans (were applicable) or from other findings. The depth of dose prescription was calculated as depth of infiltration plus thickness of the thermoplastic mask. After volume optimization, and dose constraints satisfied, the result of calculation was reviewed and improved by dose shaper tool Results: In total 5 patients were treated till now. One had lenticular metastases (field size 25cm x 11cm), others had basocellular carcinoma of different sizes (up to the whole half of the skull). Three patients already finished treatment and had first follow up, two other are currently under treatment. First clinical results were obvious: pain relief, stoppage of bleeding, significant reduction of lesion.
MAASTRO CLINIC, Radiotherapy-Oncology, Maastricht, Netherlands
Purpose: HDR brachytherapy with iridium-192 is a frequently used technique for the treatment of patients with cervical cancer. The position of the gynecological applicator in the cervical canal can change between the imaging phase and the actual treatment, e.g. due to patient transport from the CT to the irradiation suite. As a result, deviations between the planned dose distribution and the actual dose distribution may occur. To verify the in vivo dose values in the organs at risk viz. bladder and rectum, MOSFET-dosimetry was performed. Materials: Micro-MOSFETs (TN-502RDM) and a MOSFET linear-array (TN252LA5) were used for the measurements. Calibration was performed in water. The MOSFET was placed in the center and a 192 Ir source was placed at 0◦ and 180◦ . Phantom measurements were performed to investigate the linearity and the angular dependence of the detector response. Next, measurements were performed to simulate the clinical measurements in a phantom. Measurements were performed in 2 patients during sequential fractions. A micro-MOSFET was placed in the urine catheter and a linear-array was positioned in the rectum and fixed with a home-made rectum sponge. In vivo dose values were compared to calculated dose values at these positions. Uncertainties are given as 1 SD of the mean. Results: The calibration factor was (1.19±0.02) mV/cGy for the microMOSFETs and (0.90±0.01) mV/cGy for the linear array. Phantom measurements demonstrated that the MOSFET dose response is almost linear in the clinical dose range, from 15 cGy up to 8 Gy. The angular dependence of the response is within 2% (180◦ ). The simulation of the clinical practice in a phantom demonstrated a mean result of (1±7)%. Patient in vivo measurements demonstrated an average deviation between measured and calculated doses of (-4±18)% for the bladder and (-9±15)% for the rectum. Conclusions: In vivo dosimetry is a method to register the actual dose values in the OARs and link dose values to clinical side effects. MOSFETs are potentially suitable for in vivo dosimetry during HDR brachytherapy. Deviations between the planned and actual dose values may occur due to an error in the treatment process and to a shift of the applicator in the cervical canal after the imaging procedure. Also, a deviation in dose in the organs at risk can occur due to internal motion with respect to the applicator (intestinal motion and bladder filling). 374 poster (Physics Track) THE CHOICE OF THE BEST DISPOSITION OF THE DOSE IN THE TREATMENT IN PARTIAL BREAST IRRADIATION. M. Jurczyk1 , T. Opala2 , P. Jankowski3 , J. Kobzda3 1 G INEKOLOGICZNO -P OLOZNICZY S ZPITAL K LINICZNY UM, Department of Mother’s and Child’s Health, Poznan University of Medical Sciences, Laboratory HDR, Poznan, Poland 2 G INEKOLOGICZNO -P OLOZNICZY S ZPITAL K LINICZNY UM, Department of Mother’s and Child’s Health, Poznan University of Medical Sciences, Poznan, Poland 3 G INEKOLOGICZNO -P OLOZNICZY S ZPITAL K LINICZNY UM, Department of Brachytherapy, Poznan, Poland
patient with lenticular metastases treated with brachytherapy mould Conclusions: This treatment modality is very simple, effective and with excellent outcomes (clinical and esthetical). It is easily implemented in all patients, especially in elderly people, those with cardiac problems, and all who cannot be surgically treated.ACKNOWLEDGMENTThis work has been done after the complete renovation of the brachytherapy premises and installation of new equipment at the institution, funded by IAEA (national TC project) Authors are grateful to the hosts of the IAEA fellowships in Maria Sklodowska Curie Memorial Cancer Center in Gliwice, Poland
Purpose: New trends in the treatment of breast cancer by brachytherapy proceeded by operative intervention show comparable effectiveness of PBI and WBI. Standard planning of the disposition of the doses is based on the principles of the Paris system. Materials: Theoretical comparison of the three methods of planning of the disposition of the dose with the specification of various points was carried out in the Laboratory of Brachytherapy Gynaecological and Obstetrical Clinical Hospital of University of Medical Sciences in Poznan: 1◦ method based on the 3 description points being the centre of gravity of triangles; 2◦ method based on the 1 description point being the centre of gravity of the trapezium; 3◦ method - In the centre of the tumor bad.To the analysis an applicator was chosen consisting of five needles arranged in two planes (3 + 2). The disposition of doses from the first method were accepted as the reference. Results: Uniformity Index of the tumor bad in respective methods carried out suitably: 1,40 ± 0,02; 1,28 ± 0,015; 1,11 ± 0,10.The use of the second method caused the reduction of V85 about the average 14,55 %, V100 about 19,81 % and V150 about 19,7 % in relation to above mentioned volumes in the first method. Parameters for the third method were less convenient: 24,38 %, 34,1 % and 30,51 %. Conclusions: The third method seems to be theoretically the best of irradiating the volume a the tumor bad with the simultaneous reduction of the dose in the area of the healthy tissues.