- Email: [email protected]
Assessment of the Implant Geometry in Fractionated Interstitial HDR Breast Brachytherapy
Abstracts / Brachytherapy 15 (2016) S21eS204 target. Catheter insertion under ideal conditions (i.e. on phantom) takes about 29.66.9s and includes the full reconstruction of the catheter geometry and tip localization (within 0.70.3 mm of true location). The DVHs and dose metrics are updated automatically based the EM information. At any time, the EM-tracked stylet can be reinserted to reacquire one or more catheter’s position; it takes ~2.5 minutes for a typical 16-catheters implant (9.52.6s/catheter, including dose recalculation). We further compared the new TPS volumes and plans to a commercial TPS as well as confirm the validity of the DICOM-RT export. Conclusions: The proposed platform integrates innovative technologies that have the potential to increase precision and accessibility of prostate HDR brachytherapy. The results, using clinically realistic workflows, show a significant streamlining the 3DUS-based real-time implant process. Key critical steps, such as accurate catheter reconstruction and tip localization are obtained at no (time) cost following insertion and can be redone quickly as required. This pre-clinical study suggests that realtime HDR procedures could be performed in less than 1 hour, on par with real-time prostate seed implants.
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average by 5.1 mm (s.d. 0.5 mm). The systematic offset of all dwell positions represents an error detection signature that can identify the potential origin of the error. Conclusions: Two examples of simulated treatment errors are presented. Each produced an error signature that allowed identification of the origin of the treatment delivery error. Employing a FPD system for tracking the source during treatment delivery facilitates a non-invasive error detection method for HDR brachytherapy. Characterisation of all possible failure modes and error signatures will allow automatic algorithms to specifically identify each of these, and also allow the establishment of clinically relevant treatment interrupt thresholds for errors that will have a detrimental impact on the patient’s treatment.
PP10 Presentation Time: 2:48 PM Treatment Delivery Error Trapping in HDR Brachytherapy Ryan L. Smith, MAppSci1,2, Annette Haworth, PhD3,2, Vanessa Panettieri, PhD1, Jeremy Millar, FRANZCR1,2, Rick Franich, PhD2. 1Alfred Health Radiation Oncology, The Alfred Hospital, Melbourne, Australia; 2School of Applied Sciences, RMIT University, Melbourne, Australia; 3Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, Australia. Purpose: Independent routine treatment delivery verification is important to identify potential errors and ensure patient safety in high dose rate (HDR) brachytherapy. Compared with external beam, the relative risk of a treatment error is high due to the many steps in a brachytherapy procedure involving human/manual tasks, but the frequency and severity of these errors is largely unknown as there are limited systems available to identify and report errors. Here we demonstrate a novel, non-invasive flat panel detector (FPD) system to provide source position information during treatment delivery. Combined with the treatment plan, the system acts as an in vivo error trapping device, providing the user with feedback as to the cause and possible severity of the treatment delivery error. Materials and Methods: For the purpose of this error trapping simulation a solid water phantom containing 18 plastic catheters was constructed. The phantom was CT scanned and a treatment plan created using six catheters. The phantom was placed on the treatment couch, above the FPD which is integrated into the HDR brachytherapy treatment couch. Radio-opaque xray dwell position markers were inserted into the treatment catheters and a radiograph acquired with a ceiling mounted x-ray source and the FPD. The x-ray dwell position markers were removed, the transfer tubes connected and the treatment plan delivered. As the treatment progressed, the FPD acquired ‘images’ of the Ir-192 exit radiation distribution at each dwell position. The distribution ‘image’ at each dwell position was processed to determine the source position, which was then compared to the expected position derived from the treatment plan, for delivery verification. Potential treatment delivery errors were simulated. These represent errors likely to occur in the clinical setting, which are typically difficult to localise with current approaches. Simulated errors included incorrect indexer length and incorrect transfer channel connection (interchanged channels). The calculated difference in position between planned and measured dwell positions for each delivered dwell was used as a mechanism to immediately indicate the presence and likely cause of the treatment delivery errors. Results: Incorrect transfer channel connection simulation is depicted in figure 1(a), showing the planned dwells of channel 1 (red circles) erroneously being delivered to channel 5 (black circle/cross). The average difference between planned and measured position is 79.0 mm (s.d. 0.3 mm), clearly flagging a (simulated) treatment error had occurred. For the simulated indexer length error the measured dwell positions offset from the planned positions in the long axis of the implanted catheters on
Figure 1. Pre-treatment radiograph showing the planned dwell positions (red circles) and the actual measured dwell positions (black circle/cross), overlayed on the x-ray dwell position markers, (a) A simulation of an interchanged channel connection delivery error, illustrating channel 1 and channel 5 incorrectly connected, (b) A simulation of incorrect indexer length delivery error for all catheters.
PP11 Presentation Time: 2:57 PM Assessment of the Implant Geometry in Fractionated Interstitial HDR Breast Brachytherapy Markus Kellermeier, PhD, Benjamin Hofmann, BSc, Vratislav Strnad, MD, Christoph Bert, PhD. Radiation Oncology, University Clinic Erlangen, Erlangen, Germany. Purpose: To determine the inter-fraction stability of the implant geometry in fractionated HDR interstitial brachytherapy (HDR-iBT) partial breast irradiations (PBI) by means of electromagnetic tracking (EMT). Materials and Methods: In our contemporary phantom study, an EMT protocol to track 6F catheters with an accuracy of 10.3 mm (maximum: 2 mm) in our typical clinical environment was established [Kellermeier et al. Med. Phys. 42(6):3533]. Based on that protocol, the implant geometry of 21 patients (17 patients: 9-fraction PBI and four patients: 2fraction boost after teletherapy) was quantified during their iBT treatment. For each patient, the implant geometry was measured on the CT table just after acquiring the treatment planning scan (EMCT) and on the HDR treatment table directly after each treatment fraction (EMFx). Three 6 degrees of freedom (DoF) sensors were placed on the breast surface to obtain fiducial positions used to derive relative positions of a 5 DoF sensor manually and consecutively inserted in the catheters. To compensate for patient movements, e.g. respiratory motion, the implant sensor data were corrected against the mean position of the fiducial sensors. Using the catheter traces, dwell positions (DPs) were determined for each measurement. In analogy to the already published phantom studies, the rigid coherent point drift (CPD) algorithm was used to register corresponding DPs. For each patient, the determined DPs from EMCT and EMFx were compared against the CT-derived DPs from treatment planning (CTRef). In addition, to assess quantitatively the changes in the implant geometry - without the need for registration - the
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Abstracts / Brachytherapy 15 (2016) S21eS204
distances from each DP to all DPs within a 3 cm spherical range were determined. For each measured implant geometry, the change in these intra-implant DP distances (IIDD) was compared with those from CTRef. Results: EMT of the whole catheter implant per patient (median: 17 catheters) took per fraction on average 6.8 minutes plus a few minutes for setup of the EMT system. The registered implant geometry from the CT table showed over all DPs a mean deviation of 1.3 mm (median: 1.1 mm, inter-quartile range IQR: 0.9 mm). Registration of the EMT-based DP from the fractions (EMFx) against CTRef resulted in an overall mean deviation of 2.4 mm (median: 2.2 mm, IQR: 1.7 mm). Throughout the fractionated treatment, no significant trend could be determined (see the Figure for the various measurement sessions). Regarding the change in IIDD over CTRef, EMCT showed a mean deviation of 0.9 mm (median: 0.6 mm, IQR: 1.1 mm). In the EMFx data, IIDD changed by 1.0 mm (median: 0.8 mm, IQR: 1.3 mm). Conclusions: EMT measurements in 21 HDR-iBT breast patients were feasible within the clinical workflow and well tolerated by the patients. EMT determined DPs based on the patient measurements on the CT table differed by 1.3 mm (mean) from the CT-derived DPs used for treatment planning. Throughout the fractionated treatment, the EMT determined DP deviation increased to 2.4 mm (mean) without a significant trend over the treatment duration. Financial disclosure statement: This study was supported by an unrestricted research grant from Elekta.
coatings, enhance the energy distribution in the nucleus of cells. Here, transmission electron microscopy (TEM) imaging was used to reveal the internal distribution of NPs 8 days after intratumoral injection in a PC3 prostate cancer murine model. The NPs distribution (Fig. 1a) was then used in a Monte Carlo simulation (MC). Materials and Methods: The cytoplasmic and nucleus membranes were contoured on the TEM cell images of injected tumors; these contours are used to generate the geometry models for cells and nucleus in MC. Eight days after injection, the NPs appeared massively trapped in vesicles located inside and outside of the cytoplasmic membranes. Then, the Geant4-DNA code was used to simulate all energy deposition events. Each NP was modeled as a ø10 nm 103Pd core plus 20 nm gold coating. Vesicles were modeled as spheres with equivalent diameter as those in TEM images and a compact packing model (F51.0) was used to position NPs inside the vesicles. Alternative packing models using various slack factors (F50.9, 0.7, 0.5, defined as the number of NPs divided by that of the compact model) were further investigated. The NP concentration was estimated 68.9 mg-Au/g-H2O in the local region of injection, which determines the separation between NPs in the hypothetical uniform distributions. Results: For vesicles, the radius-independent radial energy deposition (RED, defined as radial energy deposition scaled by the square of radius) curve increases dramatically with the dimension of vesicles. As shown in Fig. 1b, the peak RED value of the ø 0.2mm vesicle is 1230 m^2 MeV/
Figure. Deviation of EMT-based dwell positions against the CT-derived dwell positions from treatment planning (CTRef) considering all fractions of all patients. On each box, the central mark is the median, the edges of the box are the 25th and 75th percentiles, the whiskers extend to the extreme data points not considering outliers, which are plotted individually.
PP12 Presentation Time: 3:06 PM A Monte-Carlo Study of Cellular Dosimetry of Radioactive Gold-Palladium Nanoparticles Based on the Transmission Electron Microscopy Images Yunzhi Ma, PhD1,2, Myriam Laprise-Pelletier, Msc3,4, Jean Lagueux, ote, PhD1, Marc-Andre Fortin, PhD1,5, PhD1, Marie-France C^ Luc Beaulieu, PhD1,6. 1Department de Radio-Oncologie, Centre de recherche du CHU de Quebec, Quebec City, QC, Canada; 2Department of Physics, Engineering and Optics and Centre de recherche sur le cancer, Universite Laval, Quebec, QC, Canada; 3Centre de recherche du CHU de Quebec, Quebec City, QC, Canada; 4Department of Mining, Metallurgy and Materials Engineering, Universite Laval, Quebec City, QC, Canada; 5 Department of Mining, Metallurgy and Materials Engineering, Universite Laval, Quebec City, QC, Canada; 6Department of Physics, Engineering and Optics and Centre de recherche sur le cancer, Universite Laval, Quebec City, QC, Canada. Purpose: Radioactive gold-palladium nanoparticles (103Pd:Pd@Au NPs) are being developed for prostate cancer brachytherapy. Photons emitted by 103Pd (energies: 20.1 and 23.0 keV), interacting with gold on NP
Figure 1. a) TEM image 8 days after injection; b) Radial energy deposition (RED) of vesicles; c) Energy deposition distribution (EDD) with uniform extracellular NP distribution; d) EDD with uniform cytoplasmic NP distribution; e) EDD with vesicles-based NP distribution; f) Histograms of EDD in the central nucleus for the three situations described in c), d), e).
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average by 5.1 mm (s.d. 0.5 mm). The systematic offset of all dwell positions represents an error detection signature that can identify the potential origin of the error. Conclusions: Two examples of simulated treatment errors are presented. Each produced an error signature that allowed identification of the origin of the treatment delivery error. Employing a FPD system for tracking the source during treatment delivery facilitates a non-invasive error detection method for HDR brachytherapy. Characterisation of all possible failure modes and error signatures will allow automatic algorithms to specifically identify each of these, and also allow the establishment of clinically relevant treatment interrupt thresholds for errors that will have a detrimental impact on the patient’s treatment.
PP10 Presentation Time: 2:48 PM Treatment Delivery Error Trapping in HDR Brachytherapy Ryan L. Smith, MAppSci1,2, Annette Haworth, PhD3,2, Vanessa Panettieri, PhD1, Jeremy Millar, FRANZCR1,2, Rick Franich, PhD2. 1Alfred Health Radiation Oncology, The Alfred Hospital, Melbourne, Australia; 2School of Applied Sciences, RMIT University, Melbourne, Australia; 3Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, Australia. Purpose: Independent routine treatment delivery verification is important to identify potential errors and ensure patient safety in high dose rate (HDR) brachytherapy. Compared with external beam, the relative risk of a treatment error is high due to the many steps in a brachytherapy procedure involving human/manual tasks, but the frequency and severity of these errors is largely unknown as there are limited systems available to identify and report errors. Here we demonstrate a novel, non-invasive flat panel detector (FPD) system to provide source position information during treatment delivery. Combined with the treatment plan, the system acts as an in vivo error trapping device, providing the user with feedback as to the cause and possible severity of the treatment delivery error. Materials and Methods: For the purpose of this error trapping simulation a solid water phantom containing 18 plastic catheters was constructed. The phantom was CT scanned and a treatment plan created using six catheters. The phantom was placed on the treatment couch, above the FPD which is integrated into the HDR brachytherapy treatment couch. Radio-opaque xray dwell position markers were inserted into the treatment catheters and a radiograph acquired with a ceiling mounted x-ray source and the FPD. The x-ray dwell position markers were removed, the transfer tubes connected and the treatment plan delivered. As the treatment progressed, the FPD acquired ‘images’ of the Ir-192 exit radiation distribution at each dwell position. The distribution ‘image’ at each dwell position was processed to determine the source position, which was then compared to the expected position derived from the treatment plan, for delivery verification. Potential treatment delivery errors were simulated. These represent errors likely to occur in the clinical setting, which are typically difficult to localise with current approaches. Simulated errors included incorrect indexer length and incorrect transfer channel connection (interchanged channels). The calculated difference in position between planned and measured dwell positions for each delivered dwell was used as a mechanism to immediately indicate the presence and likely cause of the treatment delivery errors. Results: Incorrect transfer channel connection simulation is depicted in figure 1(a), showing the planned dwells of channel 1 (red circles) erroneously being delivered to channel 5 (black circle/cross). The average difference between planned and measured position is 79.0 mm (s.d. 0.3 mm), clearly flagging a (simulated) treatment error had occurred. For the simulated indexer length error the measured dwell positions offset from the planned positions in the long axis of the implanted catheters on
Figure 1. Pre-treatment radiograph showing the planned dwell positions (red circles) and the actual measured dwell positions (black circle/cross), overlayed on the x-ray dwell position markers, (a) A simulation of an interchanged channel connection delivery error, illustrating channel 1 and channel 5 incorrectly connected, (b) A simulation of incorrect indexer length delivery error for all catheters.
PP11 Presentation Time: 2:57 PM Assessment of the Implant Geometry in Fractionated Interstitial HDR Breast Brachytherapy Markus Kellermeier, PhD, Benjamin Hofmann, BSc, Vratislav Strnad, MD, Christoph Bert, PhD. Radiation Oncology, University Clinic Erlangen, Erlangen, Germany. Purpose: To determine the inter-fraction stability of the implant geometry in fractionated HDR interstitial brachytherapy (HDR-iBT) partial breast irradiations (PBI) by means of electromagnetic tracking (EMT). Materials and Methods: In our contemporary phantom study, an EMT protocol to track 6F catheters with an accuracy of 10.3 mm (maximum: 2 mm) in our typical clinical environment was established [Kellermeier et al. Med. Phys. 42(6):3533]. Based on that protocol, the implant geometry of 21 patients (17 patients: 9-fraction PBI and four patients: 2fraction boost after teletherapy) was quantified during their iBT treatment. For each patient, the implant geometry was measured on the CT table just after acquiring the treatment planning scan (EMCT) and on the HDR treatment table directly after each treatment fraction (EMFx). Three 6 degrees of freedom (DoF) sensors were placed on the breast surface to obtain fiducial positions used to derive relative positions of a 5 DoF sensor manually and consecutively inserted in the catheters. To compensate for patient movements, e.g. respiratory motion, the implant sensor data were corrected against the mean position of the fiducial sensors. Using the catheter traces, dwell positions (DPs) were determined for each measurement. In analogy to the already published phantom studies, the rigid coherent point drift (CPD) algorithm was used to register corresponding DPs. For each patient, the determined DPs from EMCT and EMFx were compared against the CT-derived DPs from treatment planning (CTRef). In addition, to assess quantitatively the changes in the implant geometry - without the need for registration - the
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Abstracts / Brachytherapy 15 (2016) S21eS204
distances from each DP to all DPs within a 3 cm spherical range were determined. For each measured implant geometry, the change in these intra-implant DP distances (IIDD) was compared with those from CTRef. Results: EMT of the whole catheter implant per patient (median: 17 catheters) took per fraction on average 6.8 minutes plus a few minutes for setup of the EMT system. The registered implant geometry from the CT table showed over all DPs a mean deviation of 1.3 mm (median: 1.1 mm, inter-quartile range IQR: 0.9 mm). Registration of the EMT-based DP from the fractions (EMFx) against CTRef resulted in an overall mean deviation of 2.4 mm (median: 2.2 mm, IQR: 1.7 mm). Throughout the fractionated treatment, no significant trend could be determined (see the Figure for the various measurement sessions). Regarding the change in IIDD over CTRef, EMCT showed a mean deviation of 0.9 mm (median: 0.6 mm, IQR: 1.1 mm). In the EMFx data, IIDD changed by 1.0 mm (median: 0.8 mm, IQR: 1.3 mm). Conclusions: EMT measurements in 21 HDR-iBT breast patients were feasible within the clinical workflow and well tolerated by the patients. EMT determined DPs based on the patient measurements on the CT table differed by 1.3 mm (mean) from the CT-derived DPs used for treatment planning. Throughout the fractionated treatment, the EMT determined DP deviation increased to 2.4 mm (mean) without a significant trend over the treatment duration. Financial disclosure statement: This study was supported by an unrestricted research grant from Elekta.
coatings, enhance the energy distribution in the nucleus of cells. Here, transmission electron microscopy (TEM) imaging was used to reveal the internal distribution of NPs 8 days after intratumoral injection in a PC3 prostate cancer murine model. The NPs distribution (Fig. 1a) was then used in a Monte Carlo simulation (MC). Materials and Methods: The cytoplasmic and nucleus membranes were contoured on the TEM cell images of injected tumors; these contours are used to generate the geometry models for cells and nucleus in MC. Eight days after injection, the NPs appeared massively trapped in vesicles located inside and outside of the cytoplasmic membranes. Then, the Geant4-DNA code was used to simulate all energy deposition events. Each NP was modeled as a ø10 nm 103Pd core plus 20 nm gold coating. Vesicles were modeled as spheres with equivalent diameter as those in TEM images and a compact packing model (F51.0) was used to position NPs inside the vesicles. Alternative packing models using various slack factors (F50.9, 0.7, 0.5, defined as the number of NPs divided by that of the compact model) were further investigated. The NP concentration was estimated 68.9 mg-Au/g-H2O in the local region of injection, which determines the separation between NPs in the hypothetical uniform distributions. Results: For vesicles, the radius-independent radial energy deposition (RED, defined as radial energy deposition scaled by the square of radius) curve increases dramatically with the dimension of vesicles. As shown in Fig. 1b, the peak RED value of the ø 0.2mm vesicle is 1230 m^2 MeV/
Figure. Deviation of EMT-based dwell positions against the CT-derived dwell positions from treatment planning (CTRef) considering all fractions of all patients. On each box, the central mark is the median, the edges of the box are the 25th and 75th percentiles, the whiskers extend to the extreme data points not considering outliers, which are plotted individually.
PP12 Presentation Time: 3:06 PM A Monte-Carlo Study of Cellular Dosimetry of Radioactive Gold-Palladium Nanoparticles Based on the Transmission Electron Microscopy Images Yunzhi Ma, PhD1,2, Myriam Laprise-Pelletier, Msc3,4, Jean Lagueux, ote, PhD1, Marc-Andre Fortin, PhD1,5, PhD1, Marie-France C^ Luc Beaulieu, PhD1,6. 1Department de Radio-Oncologie, Centre de recherche du CHU de Quebec, Quebec City, QC, Canada; 2Department of Physics, Engineering and Optics and Centre de recherche sur le cancer, Universite Laval, Quebec, QC, Canada; 3Centre de recherche du CHU de Quebec, Quebec City, QC, Canada; 4Department of Mining, Metallurgy and Materials Engineering, Universite Laval, Quebec City, QC, Canada; 5 Department of Mining, Metallurgy and Materials Engineering, Universite Laval, Quebec City, QC, Canada; 6Department of Physics, Engineering and Optics and Centre de recherche sur le cancer, Universite Laval, Quebec City, QC, Canada. Purpose: Radioactive gold-palladium nanoparticles (103Pd:Pd@Au NPs) are being developed for prostate cancer brachytherapy. Photons emitted by 103Pd (energies: 20.1 and 23.0 keV), interacting with gold on NP
Figure 1. a) TEM image 8 days after injection; b) Radial energy deposition (RED) of vesicles; c) Energy deposition distribution (EDD) with uniform extracellular NP distribution; d) EDD with uniform cytoplasmic NP distribution; e) EDD with vesicles-based NP distribution; f) Histograms of EDD in the central nucleus for the three situations described in c), d), e).