- Email: [email protected]
65. Study of respiratory signals of patients undergoing 4DCT for VMAT lung cancer treatments
Abstracts / Physica Medica 56 (2018) 59–132
sion/shape/shrinkage. Only 3 patients experienced >1 cc change of SL95%-105% during treatment (maximum variation: 6 cc) while negative DSL95%-105% > 1 cc, up to 17 cc, were seen in 15/33 patients. A negative change was correlated with the presence of some overlap between PTV and SL at planning (p = 0.03). DSL 95% are shown for all patients in Fig. 1. Conclusions. Most patients treated with a SIB approach with Tomotherapy for HN cancer showed negative or irrelevant changes to the dose delivered to the skin. Less than 10% of patients seem to be candidate to ART to counteract any significant skin dose increase during therapy. https://doi.org/10.1016/j.ejmp.2018.04.073
64. Skin dose in high dose rate brachytherapy for breast cancers: evaluation by in vivo dosimetry using TLD and MOSFET dosimeters S. Fabiani a, M. Italiani a, M. Casale a, M. Muti a, E. Maranzano b
103
and they were placed on the skin next to the catheters and the nipple. We are currently implementing MOSFET real time measurements to compare with TLD results and to further improve the estimation of the skin dose. Results. The doses measured by TLDs were compared to those calculated by the TPS in specific region of interest (ROI). For each patient two IVD sessions were performed, and the reproducibility of TLD positioning was assessed: 60% of couples give the same value within the experimental error. 77% of measurements show a clear overestimation of skin dose by the TPS. A Gaussian fit of the percentage differences between measured and calculated doses (Fig. 1) yielded an overestimation value of (25.2 ± 7.6)%. For a first group of patients IVD sessions were performed using MOSFET dosimeters, placed on the skin following the previous arrangement of TLDs. The doses measured by MOSFETs were compared to those calculated by the TPS in specific ROIs. Preliminary results show a quantitatively similar overestimation. Conclusions. Measurements in PB-BRT are necessary to quantify the real skin dose accurately. A novel approach based on IVD allows us to define dose limits, to achieve not only the tumor control but also a good cosmetic outcome to improve the quality of patient’s life.
a
Azienda Ospedaliera S. Maria, S.C. Radioterapia Oncologica – S.S. Fisica Sanitaria, Terni, Italy b Azienda Ospedaliera S. Maria, S.C. Radioterapia Oncologica, Terni, Italy Purpose. The aim of this work is to evaluate a novel approach for the verification of the real skin dose in partial breast high dose rate brachytherapy (PB-BRT), quantify the treatment planning system (TPS) overestimation and develop a methodology for routinary in vivo dosimetry (IVD). Methods. Currently there is not a general acknowledged constraint for skin dose in PB-BRT. Because of our center’s experience (20 PBBRT patients treated/year) we achieve a good cosmetic outcome if the TPS calculated skin dose is below 50% of the prescription of 32 Gy (4 Gy/fraction, twice daily). The skin dose was calculated by a TPS which overestimates it assuming a homogeneous water medium and not accounting for the finite patient dimensions. IVD was performed on patients treated with multi-catheter brachytherapy, which involves placement of 9–15 catheters through the breast. Thermoluminescent dosimeters (TLDs) were used in the IVD sessions
https://doi.org/10.1016/j.ejmp.2018.04.074
65. Study of respiratory signals of patients undergoing 4DCT for VMAT lung cancer treatments L. Redapi a, M. Querci a, L. Marrazzo b, S. Calusi a, C. Talamonti a,b, M. Casati b, S. Pallotta a,b a
Department of Biomedical, Experimental and Clinical Sciences ‘‘Mario Serio”, University of Florence, Florence, Italy b Medical Physics Unit AOU Careggi, Florence, Italy Purpose. To account for respiratory motion in radiotherapy treatment of lung lesions, 4DCT is often employed. For a correct reconstruction of respiratory phases, periodic and regular breathing is the underlying hypothesis when phase-binning algorithms are used. Aim of this work was to study the respiratory signals acquired during 4DCT and to evaluate whether a correlation exists between deviations from regularity of breathing signal and quality of reconstructed images. Methods and materials. 4DCT of 40 patients acquired with a Philips Brilliance Big Bore CT were analyzed in this study. Respiratory signals were exported and an in-house written Matlab routine was used for extracting and processing the waveforms. The duration of each respiratory cycle (CD) was calculated as the distance between two consecutive maxima, while the fraction of inspiration (ID) was calculated as the ratio between the distance minimum–maximum and the duration of the whole cycle. Mean value (M), standard deviation (rÞ and relative percentage error Er ¼ Mr 100 were extracted for each patient, the latter being a measurement of breathing regularity. Thereafter, 4DCT image quality was blindly scored from 1 to 4 (1: presence of visible artifacts in the reconstructed phases, 4: absence of visible artifacts). Patients were classified according to the score and mean relative percentage errors and standard deviations were calculated within each scoring class. Results. In fig. 1 mean relative percentage errors versus assigned score are reported for both CD and ID. A correlation between Er and image quality is clearly visible. Threshold values for Er of about 18% for CD and about 15% for ID can be identified as limits between good and bad quality reconstructed images. Conclusion. Variations in respiratory cycle and inspiration phase duration clearly correlate with the quality of 4DCT reconstruction and can be used as predictors of image quality.
104
Abstracts / Physica Medica 56 (2018) 59–132
https://doi.org/10.1016/j.ejmp.2018.04.075
66. Results of a spectrometric analysis performed at the ASST Lariana on 223Ra-dichloruro Xofigo A. Ostinelli, M. Duchini, M. Frigerio, P. Lattuada, M. Cacciatori ASST Lariana, UOC Fisica Sanitaria, Como, Italy Purpose. BAYER has recently marketed a pharmaceutical named Xofigo, consisting of 223Ra-dichloride, for the treatment of metastatic bone lesions of castration-resistant prostate cancer. Its production modality consists of the neutron irradiation of a 226Ra target yielding 227Ac which, through intermediate steps, decays into 223Ra. In view of the possible presence of radionuclide impurities that may demand strong radiation protection requirements (e.g. 227Ac and 226Ra), a radiometric analysis of Xofigo was performed to rule out any contamination by other long-lived radioisotopes [1]. Methods. The spectrometry system consisted of the GEM-20 P EG&G ORTEC Hyperpure Germanium detector, the ORTEC TRIUMPPCI-8 k multichannel analyzer, the ORTEC GammaVision spectral analysis program, and two certified calibration point sources (152Eu and 241Am). A 0.2 ml volume of radiopharmaceutical (about 200 kBq activity) was inserted into a conical test tube and the gamma emission spectrum was acquired. The detection efficiency
was calculated by a dedicated application (ORTEC ANGLE v.3.0), integrated with the GammaVision software. The spectral analysis was performed by means of a specific library, containing both expected and suspected radioisotopes. Results. The spectral acquisitions (see Figure) and the related analysis (see Table) were repeated to test the reproducibility of the results and provided the following outcomes: the calculated 223Ra activity was (196 ± 9) kBq, in agreement with the one measured at sampling, and the 211Bi and 219Rn activities were absolutely compatible with the transient equilibrium condition with the 223Ra father. No radionuclides other than those expected were found above the minimum detectable activity (MDA). Conclusions. Any significant presence of radioisotope contamination in the radiopharmaceutical sample and, consequently, of issues related to long-lived radionuclides, can be excluded, ensuring both the operator and the patient protection and the safe management of the radioactive waste. Reference 1. EANM Guideline for radionuclide therapy of bone metastases with radium-223; 2017. https://doi.org/10.1016/j.ejmp.2018.04.076
sion/shape/shrinkage. Only 3 patients experienced >1 cc change of SL95%-105% during treatment (maximum variation: 6 cc) while negative DSL95%-105% > 1 cc, up to 17 cc, were seen in 15/33 patients. A negative change was correlated with the presence of some overlap between PTV and SL at planning (p = 0.03). DSL 95% are shown for all patients in Fig. 1. Conclusions. Most patients treated with a SIB approach with Tomotherapy for HN cancer showed negative or irrelevant changes to the dose delivered to the skin. Less than 10% of patients seem to be candidate to ART to counteract any significant skin dose increase during therapy. https://doi.org/10.1016/j.ejmp.2018.04.073
64. Skin dose in high dose rate brachytherapy for breast cancers: evaluation by in vivo dosimetry using TLD and MOSFET dosimeters S. Fabiani a, M. Italiani a, M. Casale a, M. Muti a, E. Maranzano b
103
and they were placed on the skin next to the catheters and the nipple. We are currently implementing MOSFET real time measurements to compare with TLD results and to further improve the estimation of the skin dose. Results. The doses measured by TLDs were compared to those calculated by the TPS in specific region of interest (ROI). For each patient two IVD sessions were performed, and the reproducibility of TLD positioning was assessed: 60% of couples give the same value within the experimental error. 77% of measurements show a clear overestimation of skin dose by the TPS. A Gaussian fit of the percentage differences between measured and calculated doses (Fig. 1) yielded an overestimation value of (25.2 ± 7.6)%. For a first group of patients IVD sessions were performed using MOSFET dosimeters, placed on the skin following the previous arrangement of TLDs. The doses measured by MOSFETs were compared to those calculated by the TPS in specific ROIs. Preliminary results show a quantitatively similar overestimation. Conclusions. Measurements in PB-BRT are necessary to quantify the real skin dose accurately. A novel approach based on IVD allows us to define dose limits, to achieve not only the tumor control but also a good cosmetic outcome to improve the quality of patient’s life.
a
Azienda Ospedaliera S. Maria, S.C. Radioterapia Oncologica – S.S. Fisica Sanitaria, Terni, Italy b Azienda Ospedaliera S. Maria, S.C. Radioterapia Oncologica, Terni, Italy Purpose. The aim of this work is to evaluate a novel approach for the verification of the real skin dose in partial breast high dose rate brachytherapy (PB-BRT), quantify the treatment planning system (TPS) overestimation and develop a methodology for routinary in vivo dosimetry (IVD). Methods. Currently there is not a general acknowledged constraint for skin dose in PB-BRT. Because of our center’s experience (20 PBBRT patients treated/year) we achieve a good cosmetic outcome if the TPS calculated skin dose is below 50% of the prescription of 32 Gy (4 Gy/fraction, twice daily). The skin dose was calculated by a TPS which overestimates it assuming a homogeneous water medium and not accounting for the finite patient dimensions. IVD was performed on patients treated with multi-catheter brachytherapy, which involves placement of 9–15 catheters through the breast. Thermoluminescent dosimeters (TLDs) were used in the IVD sessions
https://doi.org/10.1016/j.ejmp.2018.04.074
65. Study of respiratory signals of patients undergoing 4DCT for VMAT lung cancer treatments L. Redapi a, M. Querci a, L. Marrazzo b, S. Calusi a, C. Talamonti a,b, M. Casati b, S. Pallotta a,b a
Department of Biomedical, Experimental and Clinical Sciences ‘‘Mario Serio”, University of Florence, Florence, Italy b Medical Physics Unit AOU Careggi, Florence, Italy Purpose. To account for respiratory motion in radiotherapy treatment of lung lesions, 4DCT is often employed. For a correct reconstruction of respiratory phases, periodic and regular breathing is the underlying hypothesis when phase-binning algorithms are used. Aim of this work was to study the respiratory signals acquired during 4DCT and to evaluate whether a correlation exists between deviations from regularity of breathing signal and quality of reconstructed images. Methods and materials. 4DCT of 40 patients acquired with a Philips Brilliance Big Bore CT were analyzed in this study. Respiratory signals were exported and an in-house written Matlab routine was used for extracting and processing the waveforms. The duration of each respiratory cycle (CD) was calculated as the distance between two consecutive maxima, while the fraction of inspiration (ID) was calculated as the ratio between the distance minimum–maximum and the duration of the whole cycle. Mean value (M), standard deviation (rÞ and relative percentage error Er ¼ Mr 100 were extracted for each patient, the latter being a measurement of breathing regularity. Thereafter, 4DCT image quality was blindly scored from 1 to 4 (1: presence of visible artifacts in the reconstructed phases, 4: absence of visible artifacts). Patients were classified according to the score and mean relative percentage errors and standard deviations were calculated within each scoring class. Results. In fig. 1 mean relative percentage errors versus assigned score are reported for both CD and ID. A correlation between Er and image quality is clearly visible. Threshold values for Er of about 18% for CD and about 15% for ID can be identified as limits between good and bad quality reconstructed images. Conclusion. Variations in respiratory cycle and inspiration phase duration clearly correlate with the quality of 4DCT reconstruction and can be used as predictors of image quality.
104
Abstracts / Physica Medica 56 (2018) 59–132
https://doi.org/10.1016/j.ejmp.2018.04.075
66. Results of a spectrometric analysis performed at the ASST Lariana on 223Ra-dichloruro Xofigo A. Ostinelli, M. Duchini, M. Frigerio, P. Lattuada, M. Cacciatori ASST Lariana, UOC Fisica Sanitaria, Como, Italy Purpose. BAYER has recently marketed a pharmaceutical named Xofigo, consisting of 223Ra-dichloride, for the treatment of metastatic bone lesions of castration-resistant prostate cancer. Its production modality consists of the neutron irradiation of a 226Ra target yielding 227Ac which, through intermediate steps, decays into 223Ra. In view of the possible presence of radionuclide impurities that may demand strong radiation protection requirements (e.g. 227Ac and 226Ra), a radiometric analysis of Xofigo was performed to rule out any contamination by other long-lived radioisotopes [1]. Methods. The spectrometry system consisted of the GEM-20 P EG&G ORTEC Hyperpure Germanium detector, the ORTEC TRIUMPPCI-8 k multichannel analyzer, the ORTEC GammaVision spectral analysis program, and two certified calibration point sources (152Eu and 241Am). A 0.2 ml volume of radiopharmaceutical (about 200 kBq activity) was inserted into a conical test tube and the gamma emission spectrum was acquired. The detection efficiency
was calculated by a dedicated application (ORTEC ANGLE v.3.0), integrated with the GammaVision software. The spectral analysis was performed by means of a specific library, containing both expected and suspected radioisotopes. Results. The spectral acquisitions (see Figure) and the related analysis (see Table) were repeated to test the reproducibility of the results and provided the following outcomes: the calculated 223Ra activity was (196 ± 9) kBq, in agreement with the one measured at sampling, and the 211Bi and 219Rn activities were absolutely compatible with the transient equilibrium condition with the 223Ra father. No radionuclides other than those expected were found above the minimum detectable activity (MDA). Conclusions. Any significant presence of radioisotope contamination in the radiopharmaceutical sample and, consequently, of issues related to long-lived radionuclides, can be excluded, ensuring both the operator and the patient protection and the safe management of the radioactive waste. Reference 1. EANM Guideline for radionuclide therapy of bone metastases with radium-223; 2017. https://doi.org/10.1016/j.ejmp.2018.04.076