One of the treatment options for recurrent brain metastases is surgical resection combined with i... more One of the treatment options for recurrent brain metastases is surgical resection combined with intracranial brachytherapy. GammaTile® (GT) (GT Medical Technologies, Tempe, Arizona) is a tile-shaped permanent brachytherapy device with cesium 131 (131 Cs) seeds embedded within a collagen carrier. We report a case of treating a patient with recurrent brain metastases with GT and demonstrate a dosimetric modeling method.
International Journal of Radiation Oncology*Biology*Physics, 2019
evaluable patients, median EPIC-26 bowel domain at baseline was 100 (IQR 87.5-100) which decrease... more evaluable patients, median EPIC-26 bowel domain at baseline was 100 (IQR 87.5-100) which decreased to a minimum of 87.5 (IQR 81.25-95.8) at 11 months and returned to 100 (IQR 91.7-100) at most recent follow-up. Conclusion: SABR to the prostate with STADT is safe and well-tolerated with toxicity comparable to conventionally fractionated regimens.
International Journal of Radiation Oncology*Biology*Physics, 2018
interstitial (IS) brachytherapy techniques have improved the delineation and coverage of a high-r... more interstitial (IS) brachytherapy techniques have improved the delineation and coverage of a high-risk clinical target volume (HRCTV) while allowing for higher dose delivery. PMB has become increasingly controversial in the era of IGBT. Due to the lack of data on safety of omitting PMB, patterns of failure with and without use of PMB were explored. Materials/Methods: Women with locally advanced (FIGO Stage IIB-IVA or with PM invasion identified on imaging) cervical cancer diagnosed between 2001-2016 were identified. All patients received external beam radiotherapy (EBRT) and brachytherapy boost (BT) using either low-dose rate (LDR) or HDR sources (prescribed to point A and HRCTV, respectively). HRCTV was contoured using MRI guidance (either diagnostic or with apparatus in place). PMB was delivered to achieve a cumulative dose of 56-60 Gy to the lateral parametria. Demographic, treatment era (pre and post 2009), pre-treatment imaging modality, FIGO stage, lymph node status, PMB, BT modality (IS vs. tandem & ovoid, T&O), dose rate, and patterns of failure were collected. Cramer's V and chi-squared tests were used to assess strength of association between variables. The log-rank test was used for univariate analysis (UVA) and a Cox proportional hazards model was created for multivariable analysis (MVA). Overall survival (OS) was estimated using Kaplan-Meier analysis Results: A total of 71 women were identified with median follow up of 25 months. 36 women received PMB. Median doses were as follows: EBRT 45 Gy, PMB 4.5 Gy, HDR BT 29.5 Gy, and LDR 40 Gy. 37 women received HDR and 34 received LDR BT. Six patients who did not receive PMB had PM involvement only on imaging. PMB patients were less likely to have received diagnostic MRI, PET, or IS and more likely to receive LDR. The use of PET, dose rate, and treatment era were highly correlated with one another (Cramer's V 0.7-0.9, p<0.001). 2-year OS was 74%. On UVA, treatment year, use of PET, use of MRI, and dose rate were associated with OS (all p<0.05). In an MVA including PMB, age, race, nodal status, FIGO stage, and PET, para-aortic nodal involvement (HRZ 4.33, 95% CI 1.01-10.7, pZ0.049) and use of PET (HRZ0.22, 95% CI 0.1-0.7, pZ0.007) were associated with OS. PMB was associated with higher crude rates of local (22% vs. 6%, pZ0.049), locoregional (30% vs. 6%, pZ0.01), and distant failure (28% vs. 9%, pZ0.04). Conclusion: In this retrospective study, the omission of PMB did not compromise local control or impact OS in the setting of IGBT. At our institution, PMB treatment has gradually been eliminated in cervical cancer treatment. Adaptive IGBT provides accurate identification and dose shaping of HRCTV previously unachievable in the 2D era, allowing for targeting of gross parametrial involvement.
Purpose In external beam radiotherapy (EBRT), one of the major challenges is to compensate for ta... more Purpose In external beam radiotherapy (EBRT), one of the major challenges is to compensate for target motion. Recently, we developed a tracking method for target motion compensations, which includes real-time motion of the treatment couch and a prediction algorithm to correct the couch motion trajectory for the system latency. The purpose of this study was to evaluate the tracking system efficacy, using tumor motion trajectories collected from real patients diagnosed with lung cancer. Methods The treatment couches in EBRT are used for patient positioning. To include tumor motion, clinicians prescribe the radiation dose to the target including a large volume of the healthy tissue. To solve this problem, we redesigned the existing treatment couch to allow for real-time motion during the radiation delivery. As a result, the couch obtained the possibility for motion compensation. To investigate efficacy and accuracy of the tumor motion compensation, the system was evaluated using twenty...
International Journal of Radiation Oncology*Biology*Physics, 2014
evaluation & dose escalation in moving targets. Deformable registration on TWA 4-D CBCT dataset i... more evaluation & dose escalation in moving targets. Deformable registration on TWA 4-D CBCT dataset is necessary for accurate dose accumulation over oligofractionated SABR treatments & can be used as one of trigger tool for adaptive replanning.
Purpose: To investigate the effects on dose to critical structures for density corrected planning... more Purpose: To investigate the effects on dose to critical structures for density corrected planning on simple (APPA and off‐cord) and conformal (4–5 field) lung plans compared to historical experience assuming homogeneous density. Method and Materials: Ten patients were planned using both techniques with XIO CMS software. The conformal plans were normalized to percentage coverage of target volumes and the simple plans were calculated to midplane. All plans were calculated using homogeneous density as the standard. After planning, CT density corrections were implemented and monitor units were matched to the homogeneous plan; the plans were not re‐optimized. Dose volume histograms were reviewed for critical structures of cord, “hot spot” D5(PTV), and V20(lung). Plan uniformity was assessed by the slope of the PTV dose curve using the equation [(D5–D95)/Dmean]. Results: The V20 increased with corrections: 23.7±1.7 to 24.6±7.2 for complex plans; 25.2±10.8 to 26.1±11.3 for simple plans. The conformal plans degraded in uniformity by a factor twice that of the simple plans and D5 increased accordingly. Cord dose increased slightly in conformal plans (33.65Gy±12.0Gy to 34.38±12.2Gy) and remains similar in simple plans (37.83±16.5Gy to 38.11±16.8Gy). The range of cord dose variations in corrected conformal plans was from −0.22–3.24Gy; one increase raised the cord V1% from 45.95Gy to 48.84Gy. Additionally, since the simple plans historically were assumed to approximate zero cord dose for the off‐cord obliques, the calculated/delivered cord dose is much higher. The effect of density corrections increased notably in the conformal plans where more beams transverse the lung.Conclusion: Although the effect of homogeneity corrections are well documented, the outcome on plan uniformity and critical structure tolerances should be further examined when transitioning from simple to multi‐field beam arrangements including IMRT. This study provides clinical dosimetric reference for adoption of heterogeneity corrected planning.
In a preclinical study, we demonstrated that blood flow and tissue oxygenation could be manipulat... more In a preclinical study, we demonstrated that blood flow and tissue oxygenation could be manipulated by focused ultrasound; the effects of such manipulation were interrogated via optical spectroscopy at wavelengths where oxy- and deoxy-hemoglobin display different extinction properties. We have designed a clinical breast scanner based on these noninvasive techniques. In addition to the focused ultrasound field intersecting with the
In contemporary brachytherapy procedures, needle placement at the desired target is challenging f... more In contemporary brachytherapy procedures, needle placement at the desired target is challenging for a variety of reasons. A robot-assisted brachytherapy system can potentially improve needle placement and seed delivery, resulting in enhanced therapeutic outcome. In this paper we present a robotic system with 16 degrees of freedom (DOF) (9 DOF for the positioning module and 7 DOF for the surgery module) that has been developed and fabricated for prostate brachytherapy. Strategies to reduce needle deflection and target movement were incorporated after extensive experimental validation. Provision for needle motion and force feedback was included in the system to improve robot control and seed delivery. Preliminary experimental results reveal that the prototype system is sufficiently accurate in placing brachytherapy needles.
In contemporary brachytherapy procedures, needle placement at the desired target is challenging d... more In contemporary brachytherapy procedures, needle placement at the desired target is challenging due to a variety of reasons. A robot-assisted brachytherapy system can improve the needle placement and seed delivery resulting in enhanced patient care. In this paper we present a 16 DOF (degreesof-freedom) robotic system (9DOF positioning module and 7DOF surgery module) developed and fabricated for prostate brachytherapy. Techniques to reduce needle deflection and target movement have been incorporated after verifying with extensive experiments. Provisions for needle motion and force feedback have been included into the system for improving the robot control and seed delivery. Preliminary experimental results reveal that the prototype system is quite accurate (sub-millimeter) in placing brachytherapy needles.
2007 29th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2007
Robotic assistance can help clinicians to improve the flexibility of needle insertion and accurac... more Robotic assistance can help clinicians to improve the flexibility of needle insertion and accuracy of seed deposition. However, the robotic platform is a safety critical system for its automated operational mode. Thus, it is important to perform Hazard Identification &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp; Safety Insurance Control (HISIC) for securing the safety of a medical robotic system. In this paper, we have performed HISIC for our robotic platform, called Endo-Uro Computer Lattice for Intratumoral Delivery, Implementation, and Ablation with Nanosensing (ECLIDIAN). The definition and requirements of the system are described by Unified Modeling Language (UML). Failure Mode and Effect Analysis (FMEA) are executed for the principles of HISIC, such as hazard identification, safety insurance control, safety critical limit, monitoring and control. FMEA combined with UML can also be implemented to ensure reliability of the human operation. On the basis of safety control index and fuzzy mathematics, safety effective value is outlined to assess the validity of safety insurance control for robotic system. The above principles and methods are feasible and effective for hazard analysis during the development of the robotic system.
In the last decade, there have been significant developments into integration of robots and autom... more In the last decade, there have been significant developments into integration of robots and automation tools with brachytherapy delivery systems. These systems aim to improve the current paradigm by executing higher precision and accuracy in seed placement, improving calculation of optimal seed locations, minimizing surgical trauma, and reducing radiation exposure to medical staff. Most of the applications of this technology have been in the implantation of seeds in patients with early-stage prostate cancer. Nevertheless, the techniques apply to any clinical site where interstitial brachytherapy is appropriate. In consideration of the rapid developments in this area, the American Association of Physicists in Medicine (AAPM) commissioned Task Group 192 to review the state-of-the-art in the field of robotic interstitial brachytherapy. This is a joint Task Group with the Groupe Européen de Curiethérapie-European Society for Radiotherapy & Oncology (GEC-ESTRO). All developed and reporte...
In this study, the physical characteristics (penumbra width variation with the source size and sh... more In this study, the physical characteristics (penumbra width variation with the source size and shape, interleaf leakage, transmission through the leaves, and the tongueand-groove effect) of two linear accelerators (BrainLAB's Novalis and Elekta's Synergy-S Beam Modulator) have been investigated. For similar square fields (about 4.5 cm  4.5 cm) with source-to-surface/skin-distance (SSD) ranging from 90 cm to 115 cm and measurements taken at the depth of D max Z 1.5 cm for 6 MV photon beam. The Novalis MLC has penumbra width of 2.4 AE 0.11 mme2.8 AE 0.11 mm at the leaf-end and 2.2 AE 0.1 mme2.7 AE 0.1 mm on the leafside; and those for the Synergy-S MLC are 4.4 AE 0.17 mme5.2 AE 0.2 mm and 3.0 AE 0.12 mme 3.5 AE 0.12 mm. Upon rotating the Synergy-S collimator by 90 (i.e., shifting the leaf movement to the gunetarget direction), significant reduction of the leaf-end penumbra width (17%) and increase of leaf-side penumbra width (28%) suggest an elliptical shape of the radiation source spot. Similar rotation of the collimator yielded reduction of the penumbras on both leaf-end (34%) and leaf-side (28%) for Novalis, indicating that the Novalis has a more symmetric source size. For all the field sizes and settings, BrainLAB's Novalis mMLC produce a smaller penumbra for simple square fields compared to the Elekta's Synergy-S. However, this difference became less pronounced for leaf-side penumbra and also for circular fields. The tongue-and-groove effect of the Novalis (23 AE 0.9%) is slightly smaller than that of the Synergy-S (25 AE 1%); while the interleaf leakage and leakage directly through leaves for Synergy-S (1.6 AE 0.07% & 0.9 AE 0.04%) are lower than that of Novalis (2 AE 0.08% & 1.3 AE 0.05%).
Accurate placement of surgical needles is very important in a variety of medical procedures. Howe... more Accurate placement of surgical needles is very important in a variety of medical procedures. However, precise interstitial intervention is quite challenging due to the heterogeneous nature of biological tissue. In order to better understand the force acting upon the needle during insertion procedure, different types of soft material phantoms have been experimented upon in the recent years. In this paper, we have performed a comprehensive study on surgical needle insertion force into soft materials (agar, gelatin, silicon rubber, and polyvinylchloride). Experimental results include insertion force as well as a Young's modulus analysis. Additionally, the effects of temperature, and amount of time between phantom preparation and experimentation have been investigated. Initial results show that depending upon the material used, material properties will vary significantly due to both temperature as well as elapsed time. These variations can greatly change experimental results causin...
In this paper, we present needle insertion forces and motion trajectories measured during actual ... more In this paper, we present needle insertion forces and motion trajectories measured during actual brachytherapy needle insertion while implanting radioactive seeds in the prostate glands of 20 different patients. The needle motion was captured using ultrasound images and a 6 degree-of-freedom electromagnetic-based position sensor. Needle velocity was computed from the position information and the corresponding time stamps. From in vivo data we found the maximum needle insertion forces to be about 15.6 and 8.9 N for 17 gauge (1.47 mm) and 18 gauge (1.27 mm) needles, respectively. Part of this difference in insertion forces is due to the needle size difference (17G and 18G) and the other part is due to the difference in tissue properties that are specific to the individual patient. Some transverse forces were observed, which are attributed to several factors such as tissue heterogeneity, organ movement, human factors in surgery, and the interaction between the template and the needle. However, theses insertion forces are significantly responsible for needle deviation from the desired trajectory and target movement. Therefore, a proper selection of needle and modulated velocity (translational and rotational) may reduce the tissue deformation and target movement by reducing insertion forces and thereby improve the seed delivery accuracy. The knowledge gleaned from this study promises to be useful for not only designing mechanical/robotic systems but also developing a predictive deformation model of the prostate and real-time adaptive controlling of the needle.
Purpose: To investigate influence of different needle insertion and seed deposition techniques fo... more Purpose: To investigate influence of different needle insertion and seed deposition techniques for roboticbrachytherapy. To find optimal sets of low, normal and high translational and rotational velocities of the needle for decreasing insertion force, needle deflection and OR time, and increasing seed placement accuracy. Method and Materials: We have developed EUCLIDIAN — a fully automatic robotic prostate brachytherapy system. Robotic system parameters were optimized via preclinical experiments using two types of polyvinylchloride and tissue phantoms, cannula and stylet single‐axis force sensors, and six‐axis force‐torque sensor. Cannula sensor measures the force on the cannula during insertion, withdraw, and axial force exerted by tissue at rest. Stylet sensor measures the force while seed is expelled from the cartridge, during seed travel through the cannula, and at the moment when seed is deposited into tissue. Position of the needle tip and consequently deposition depth into the phantom was measured using optical encoders on the cannula and stylet motors. Cannula and stylet translational velocity range was 5–120 mm/s, and cannula rotation range was 0–30 rev/s. Force patterns were analyzed based on the experimental data. Results: According to the criteria for minimizing insertion force and OR time while maximizing seed deposition precision, it was found that best performances were achieved when cannula and stylet normal speed was 70 ± 10 mm/s and optimal high speed was 100 ± 10 mm/s. Optimal cannula rotation speed range was 15–25 rev/s. In order to avoid seed jam in the cartridge, optimal speed for pushing seed out of the cartridge was 2–5 mm/s. Conclusion: Optimal parameters were programmed in the EUCLIDIAN configuration files. Seed deposition techniques have significant influence on reduction of insertion force, needle deflection and seed deposition accuracy. Future investigation will be on adaptive parameter tuning for specific clinical encounters. Acknowledgement: Supported by NCI‐R01‐CA091763.
Purpose: Focused ultrasonicradiation is known for its ability to induce thermal effects for thera... more Purpose: Focused ultrasonicradiation is known for its ability to induce thermal effects for therapy deep in tissue without surgical intervention. To design a medium intensity focused ultrasound (MIFU) system with distributed ultrasound transducers for breast cancer therapy, physical properties of the acoustic field must be fully characterized. Method and Materials: Custom made ultrasound transducers and driving system were calibrated with 1MHz sine wave input (1mW power). Calibrated gain of RF amplifier was utilized for ultrasound power control. Numerical simulation of the ultrasoundradiation field was carried out with Rayleigh‐Sommerfold integral. The mathematical model for simulation was verified by measuring the acoustic output with a hydrophone. Heat distribution model was established based on the simulated ultrasound field. The heating experiment was implemented under different control strategies (duty cycle, pulse repetition) with tissue‐mimicking phantoms (12W each transducer) and animal tissue phantoms (20W each transducer).Results: The output power for MIFU can be controlled accurately with calibration of ultrasound driving system. The focal length of the transducer was found to be 6.9cm with resonance frequency 1MHz. At −6dB focal zone, the beam width was 0.3cm and the focal zone depth was about 3cm. The mathematical model of the ultrasound field was quite comparable with the measured results. In the simulation of ultrasound fields generated by two orthogonal transducers, the area of −6dB focal zone was 6mm×6mm. The mathematical model of thermal field distribution was verified with heating experiment. The temperature of the target point rose up to 65°C from ambient temperature within 3 minutes of sonication. Significant lesion was visible in the tissue ablation experiment. Conclusion: From the mathematical model and experimental results, it appears that MIFU can potentially be used for soft tissue ablation such as treating breast cancer with better skin sparing. Acknowledgement: Supported by NCI‐R33‐CA107860.
One of the treatment options for recurrent brain metastases is surgical resection combined with i... more One of the treatment options for recurrent brain metastases is surgical resection combined with intracranial brachytherapy. GammaTile® (GT) (GT Medical Technologies, Tempe, Arizona) is a tile-shaped permanent brachytherapy device with cesium 131 (131 Cs) seeds embedded within a collagen carrier. We report a case of treating a patient with recurrent brain metastases with GT and demonstrate a dosimetric modeling method.
International Journal of Radiation Oncology*Biology*Physics, 2019
evaluable patients, median EPIC-26 bowel domain at baseline was 100 (IQR 87.5-100) which decrease... more evaluable patients, median EPIC-26 bowel domain at baseline was 100 (IQR 87.5-100) which decreased to a minimum of 87.5 (IQR 81.25-95.8) at 11 months and returned to 100 (IQR 91.7-100) at most recent follow-up. Conclusion: SABR to the prostate with STADT is safe and well-tolerated with toxicity comparable to conventionally fractionated regimens.
International Journal of Radiation Oncology*Biology*Physics, 2018
interstitial (IS) brachytherapy techniques have improved the delineation and coverage of a high-r... more interstitial (IS) brachytherapy techniques have improved the delineation and coverage of a high-risk clinical target volume (HRCTV) while allowing for higher dose delivery. PMB has become increasingly controversial in the era of IGBT. Due to the lack of data on safety of omitting PMB, patterns of failure with and without use of PMB were explored. Materials/Methods: Women with locally advanced (FIGO Stage IIB-IVA or with PM invasion identified on imaging) cervical cancer diagnosed between 2001-2016 were identified. All patients received external beam radiotherapy (EBRT) and brachytherapy boost (BT) using either low-dose rate (LDR) or HDR sources (prescribed to point A and HRCTV, respectively). HRCTV was contoured using MRI guidance (either diagnostic or with apparatus in place). PMB was delivered to achieve a cumulative dose of 56-60 Gy to the lateral parametria. Demographic, treatment era (pre and post 2009), pre-treatment imaging modality, FIGO stage, lymph node status, PMB, BT modality (IS vs. tandem & ovoid, T&O), dose rate, and patterns of failure were collected. Cramer's V and chi-squared tests were used to assess strength of association between variables. The log-rank test was used for univariate analysis (UVA) and a Cox proportional hazards model was created for multivariable analysis (MVA). Overall survival (OS) was estimated using Kaplan-Meier analysis Results: A total of 71 women were identified with median follow up of 25 months. 36 women received PMB. Median doses were as follows: EBRT 45 Gy, PMB 4.5 Gy, HDR BT 29.5 Gy, and LDR 40 Gy. 37 women received HDR and 34 received LDR BT. Six patients who did not receive PMB had PM involvement only on imaging. PMB patients were less likely to have received diagnostic MRI, PET, or IS and more likely to receive LDR. The use of PET, dose rate, and treatment era were highly correlated with one another (Cramer's V 0.7-0.9, p<0.001). 2-year OS was 74%. On UVA, treatment year, use of PET, use of MRI, and dose rate were associated with OS (all p<0.05). In an MVA including PMB, age, race, nodal status, FIGO stage, and PET, para-aortic nodal involvement (HRZ 4.33, 95% CI 1.01-10.7, pZ0.049) and use of PET (HRZ0.22, 95% CI 0.1-0.7, pZ0.007) were associated with OS. PMB was associated with higher crude rates of local (22% vs. 6%, pZ0.049), locoregional (30% vs. 6%, pZ0.01), and distant failure (28% vs. 9%, pZ0.04). Conclusion: In this retrospective study, the omission of PMB did not compromise local control or impact OS in the setting of IGBT. At our institution, PMB treatment has gradually been eliminated in cervical cancer treatment. Adaptive IGBT provides accurate identification and dose shaping of HRCTV previously unachievable in the 2D era, allowing for targeting of gross parametrial involvement.
Purpose In external beam radiotherapy (EBRT), one of the major challenges is to compensate for ta... more Purpose In external beam radiotherapy (EBRT), one of the major challenges is to compensate for target motion. Recently, we developed a tracking method for target motion compensations, which includes real-time motion of the treatment couch and a prediction algorithm to correct the couch motion trajectory for the system latency. The purpose of this study was to evaluate the tracking system efficacy, using tumor motion trajectories collected from real patients diagnosed with lung cancer. Methods The treatment couches in EBRT are used for patient positioning. To include tumor motion, clinicians prescribe the radiation dose to the target including a large volume of the healthy tissue. To solve this problem, we redesigned the existing treatment couch to allow for real-time motion during the radiation delivery. As a result, the couch obtained the possibility for motion compensation. To investigate efficacy and accuracy of the tumor motion compensation, the system was evaluated using twenty...
International Journal of Radiation Oncology*Biology*Physics, 2014
evaluation & dose escalation in moving targets. Deformable registration on TWA 4-D CBCT dataset i... more evaluation & dose escalation in moving targets. Deformable registration on TWA 4-D CBCT dataset is necessary for accurate dose accumulation over oligofractionated SABR treatments & can be used as one of trigger tool for adaptive replanning.
Purpose: To investigate the effects on dose to critical structures for density corrected planning... more Purpose: To investigate the effects on dose to critical structures for density corrected planning on simple (APPA and off‐cord) and conformal (4–5 field) lung plans compared to historical experience assuming homogeneous density. Method and Materials: Ten patients were planned using both techniques with XIO CMS software. The conformal plans were normalized to percentage coverage of target volumes and the simple plans were calculated to midplane. All plans were calculated using homogeneous density as the standard. After planning, CT density corrections were implemented and monitor units were matched to the homogeneous plan; the plans were not re‐optimized. Dose volume histograms were reviewed for critical structures of cord, “hot spot” D5(PTV), and V20(lung). Plan uniformity was assessed by the slope of the PTV dose curve using the equation [(D5–D95)/Dmean]. Results: The V20 increased with corrections: 23.7±1.7 to 24.6±7.2 for complex plans; 25.2±10.8 to 26.1±11.3 for simple plans. The conformal plans degraded in uniformity by a factor twice that of the simple plans and D5 increased accordingly. Cord dose increased slightly in conformal plans (33.65Gy±12.0Gy to 34.38±12.2Gy) and remains similar in simple plans (37.83±16.5Gy to 38.11±16.8Gy). The range of cord dose variations in corrected conformal plans was from −0.22–3.24Gy; one increase raised the cord V1% from 45.95Gy to 48.84Gy. Additionally, since the simple plans historically were assumed to approximate zero cord dose for the off‐cord obliques, the calculated/delivered cord dose is much higher. The effect of density corrections increased notably in the conformal plans where more beams transverse the lung.Conclusion: Although the effect of homogeneity corrections are well documented, the outcome on plan uniformity and critical structure tolerances should be further examined when transitioning from simple to multi‐field beam arrangements including IMRT. This study provides clinical dosimetric reference for adoption of heterogeneity corrected planning.
In a preclinical study, we demonstrated that blood flow and tissue oxygenation could be manipulat... more In a preclinical study, we demonstrated that blood flow and tissue oxygenation could be manipulated by focused ultrasound; the effects of such manipulation were interrogated via optical spectroscopy at wavelengths where oxy- and deoxy-hemoglobin display different extinction properties. We have designed a clinical breast scanner based on these noninvasive techniques. In addition to the focused ultrasound field intersecting with the
In contemporary brachytherapy procedures, needle placement at the desired target is challenging f... more In contemporary brachytherapy procedures, needle placement at the desired target is challenging for a variety of reasons. A robot-assisted brachytherapy system can potentially improve needle placement and seed delivery, resulting in enhanced therapeutic outcome. In this paper we present a robotic system with 16 degrees of freedom (DOF) (9 DOF for the positioning module and 7 DOF for the surgery module) that has been developed and fabricated for prostate brachytherapy. Strategies to reduce needle deflection and target movement were incorporated after extensive experimental validation. Provision for needle motion and force feedback was included in the system to improve robot control and seed delivery. Preliminary experimental results reveal that the prototype system is sufficiently accurate in placing brachytherapy needles.
In contemporary brachytherapy procedures, needle placement at the desired target is challenging d... more In contemporary brachytherapy procedures, needle placement at the desired target is challenging due to a variety of reasons. A robot-assisted brachytherapy system can improve the needle placement and seed delivery resulting in enhanced patient care. In this paper we present a 16 DOF (degreesof-freedom) robotic system (9DOF positioning module and 7DOF surgery module) developed and fabricated for prostate brachytherapy. Techniques to reduce needle deflection and target movement have been incorporated after verifying with extensive experiments. Provisions for needle motion and force feedback have been included into the system for improving the robot control and seed delivery. Preliminary experimental results reveal that the prototype system is quite accurate (sub-millimeter) in placing brachytherapy needles.
2007 29th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2007
Robotic assistance can help clinicians to improve the flexibility of needle insertion and accurac... more Robotic assistance can help clinicians to improve the flexibility of needle insertion and accuracy of seed deposition. However, the robotic platform is a safety critical system for its automated operational mode. Thus, it is important to perform Hazard Identification &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp; Safety Insurance Control (HISIC) for securing the safety of a medical robotic system. In this paper, we have performed HISIC for our robotic platform, called Endo-Uro Computer Lattice for Intratumoral Delivery, Implementation, and Ablation with Nanosensing (ECLIDIAN). The definition and requirements of the system are described by Unified Modeling Language (UML). Failure Mode and Effect Analysis (FMEA) are executed for the principles of HISIC, such as hazard identification, safety insurance control, safety critical limit, monitoring and control. FMEA combined with UML can also be implemented to ensure reliability of the human operation. On the basis of safety control index and fuzzy mathematics, safety effective value is outlined to assess the validity of safety insurance control for robotic system. The above principles and methods are feasible and effective for hazard analysis during the development of the robotic system.
In the last decade, there have been significant developments into integration of robots and autom... more In the last decade, there have been significant developments into integration of robots and automation tools with brachytherapy delivery systems. These systems aim to improve the current paradigm by executing higher precision and accuracy in seed placement, improving calculation of optimal seed locations, minimizing surgical trauma, and reducing radiation exposure to medical staff. Most of the applications of this technology have been in the implantation of seeds in patients with early-stage prostate cancer. Nevertheless, the techniques apply to any clinical site where interstitial brachytherapy is appropriate. In consideration of the rapid developments in this area, the American Association of Physicists in Medicine (AAPM) commissioned Task Group 192 to review the state-of-the-art in the field of robotic interstitial brachytherapy. This is a joint Task Group with the Groupe Européen de Curiethérapie-European Society for Radiotherapy & Oncology (GEC-ESTRO). All developed and reporte...
In this study, the physical characteristics (penumbra width variation with the source size and sh... more In this study, the physical characteristics (penumbra width variation with the source size and shape, interleaf leakage, transmission through the leaves, and the tongueand-groove effect) of two linear accelerators (BrainLAB's Novalis and Elekta's Synergy-S Beam Modulator) have been investigated. For similar square fields (about 4.5 cm  4.5 cm) with source-to-surface/skin-distance (SSD) ranging from 90 cm to 115 cm and measurements taken at the depth of D max Z 1.5 cm for 6 MV photon beam. The Novalis MLC has penumbra width of 2.4 AE 0.11 mme2.8 AE 0.11 mm at the leaf-end and 2.2 AE 0.1 mme2.7 AE 0.1 mm on the leafside; and those for the Synergy-S MLC are 4.4 AE 0.17 mme5.2 AE 0.2 mm and 3.0 AE 0.12 mme 3.5 AE 0.12 mm. Upon rotating the Synergy-S collimator by 90 (i.e., shifting the leaf movement to the gunetarget direction), significant reduction of the leaf-end penumbra width (17%) and increase of leaf-side penumbra width (28%) suggest an elliptical shape of the radiation source spot. Similar rotation of the collimator yielded reduction of the penumbras on both leaf-end (34%) and leaf-side (28%) for Novalis, indicating that the Novalis has a more symmetric source size. For all the field sizes and settings, BrainLAB's Novalis mMLC produce a smaller penumbra for simple square fields compared to the Elekta's Synergy-S. However, this difference became less pronounced for leaf-side penumbra and also for circular fields. The tongue-and-groove effect of the Novalis (23 AE 0.9%) is slightly smaller than that of the Synergy-S (25 AE 1%); while the interleaf leakage and leakage directly through leaves for Synergy-S (1.6 AE 0.07% & 0.9 AE 0.04%) are lower than that of Novalis (2 AE 0.08% & 1.3 AE 0.05%).
Accurate placement of surgical needles is very important in a variety of medical procedures. Howe... more Accurate placement of surgical needles is very important in a variety of medical procedures. However, precise interstitial intervention is quite challenging due to the heterogeneous nature of biological tissue. In order to better understand the force acting upon the needle during insertion procedure, different types of soft material phantoms have been experimented upon in the recent years. In this paper, we have performed a comprehensive study on surgical needle insertion force into soft materials (agar, gelatin, silicon rubber, and polyvinylchloride). Experimental results include insertion force as well as a Young's modulus analysis. Additionally, the effects of temperature, and amount of time between phantom preparation and experimentation have been investigated. Initial results show that depending upon the material used, material properties will vary significantly due to both temperature as well as elapsed time. These variations can greatly change experimental results causin...
In this paper, we present needle insertion forces and motion trajectories measured during actual ... more In this paper, we present needle insertion forces and motion trajectories measured during actual brachytherapy needle insertion while implanting radioactive seeds in the prostate glands of 20 different patients. The needle motion was captured using ultrasound images and a 6 degree-of-freedom electromagnetic-based position sensor. Needle velocity was computed from the position information and the corresponding time stamps. From in vivo data we found the maximum needle insertion forces to be about 15.6 and 8.9 N for 17 gauge (1.47 mm) and 18 gauge (1.27 mm) needles, respectively. Part of this difference in insertion forces is due to the needle size difference (17G and 18G) and the other part is due to the difference in tissue properties that are specific to the individual patient. Some transverse forces were observed, which are attributed to several factors such as tissue heterogeneity, organ movement, human factors in surgery, and the interaction between the template and the needle. However, theses insertion forces are significantly responsible for needle deviation from the desired trajectory and target movement. Therefore, a proper selection of needle and modulated velocity (translational and rotational) may reduce the tissue deformation and target movement by reducing insertion forces and thereby improve the seed delivery accuracy. The knowledge gleaned from this study promises to be useful for not only designing mechanical/robotic systems but also developing a predictive deformation model of the prostate and real-time adaptive controlling of the needle.
Purpose: To investigate influence of different needle insertion and seed deposition techniques fo... more Purpose: To investigate influence of different needle insertion and seed deposition techniques for roboticbrachytherapy. To find optimal sets of low, normal and high translational and rotational velocities of the needle for decreasing insertion force, needle deflection and OR time, and increasing seed placement accuracy. Method and Materials: We have developed EUCLIDIAN — a fully automatic robotic prostate brachytherapy system. Robotic system parameters were optimized via preclinical experiments using two types of polyvinylchloride and tissue phantoms, cannula and stylet single‐axis force sensors, and six‐axis force‐torque sensor. Cannula sensor measures the force on the cannula during insertion, withdraw, and axial force exerted by tissue at rest. Stylet sensor measures the force while seed is expelled from the cartridge, during seed travel through the cannula, and at the moment when seed is deposited into tissue. Position of the needle tip and consequently deposition depth into the phantom was measured using optical encoders on the cannula and stylet motors. Cannula and stylet translational velocity range was 5–120 mm/s, and cannula rotation range was 0–30 rev/s. Force patterns were analyzed based on the experimental data. Results: According to the criteria for minimizing insertion force and OR time while maximizing seed deposition precision, it was found that best performances were achieved when cannula and stylet normal speed was 70 ± 10 mm/s and optimal high speed was 100 ± 10 mm/s. Optimal cannula rotation speed range was 15–25 rev/s. In order to avoid seed jam in the cartridge, optimal speed for pushing seed out of the cartridge was 2–5 mm/s. Conclusion: Optimal parameters were programmed in the EUCLIDIAN configuration files. Seed deposition techniques have significant influence on reduction of insertion force, needle deflection and seed deposition accuracy. Future investigation will be on adaptive parameter tuning for specific clinical encounters. Acknowledgement: Supported by NCI‐R01‐CA091763.
Purpose: Focused ultrasonicradiation is known for its ability to induce thermal effects for thera... more Purpose: Focused ultrasonicradiation is known for its ability to induce thermal effects for therapy deep in tissue without surgical intervention. To design a medium intensity focused ultrasound (MIFU) system with distributed ultrasound transducers for breast cancer therapy, physical properties of the acoustic field must be fully characterized. Method and Materials: Custom made ultrasound transducers and driving system were calibrated with 1MHz sine wave input (1mW power). Calibrated gain of RF amplifier was utilized for ultrasound power control. Numerical simulation of the ultrasoundradiation field was carried out with Rayleigh‐Sommerfold integral. The mathematical model for simulation was verified by measuring the acoustic output with a hydrophone. Heat distribution model was established based on the simulated ultrasound field. The heating experiment was implemented under different control strategies (duty cycle, pulse repetition) with tissue‐mimicking phantoms (12W each transducer) and animal tissue phantoms (20W each transducer).Results: The output power for MIFU can be controlled accurately with calibration of ultrasound driving system. The focal length of the transducer was found to be 6.9cm with resonance frequency 1MHz. At −6dB focal zone, the beam width was 0.3cm and the focal zone depth was about 3cm. The mathematical model of the ultrasound field was quite comparable with the measured results. In the simulation of ultrasound fields generated by two orthogonal transducers, the area of −6dB focal zone was 6mm×6mm. The mathematical model of thermal field distribution was verified with heating experiment. The temperature of the target point rose up to 65°C from ambient temperature within 3 minutes of sonication. Significant lesion was visible in the tissue ablation experiment. Conclusion: From the mathematical model and experimental results, it appears that MIFU can potentially be used for soft tissue ablation such as treating breast cancer with better skin sparing. Acknowledgement: Supported by NCI‐R33‐CA107860.
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Papers by Tarun Podder