Dr. Serena J. Scott Profile

Dr. Serena J. Scott

at Univ of California at San Francisco

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Author

Publications (5)

Proceedings Article | 12 March 2015 Paper

Development of a fast 3D treatment planning platform for clinical interstitial microwave hyperthermia within free-hand obliquely implanted HDR catheters

Serena Scott, Vasant Salgaonkar, Punit Prakash, Sergio Curto, I-Chow Hsu, Chris Diederich

Proceedings Volume 9326, 93260X (2015) https://doi.org/10.1117/12.2079701

KEYWORDS: Antennas, Tissues, 3D modeling, Superposition, Microwave radiation, Liquid crystals, High dynamic range imaging, Dielectrics, Blood, Distance measurement

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A treatment planning platform for interstitial microwave hyperthermia was developed for practical, free-hand clinical implants. Such implants, consisting of non-parallel, moderately curved antennas with varying insertion depths, are used in HDR brachytherapy for treating locally advanced cancer.

Numerical models for commercially available MA251 antennas (915 MHz, BSD Medical) were developed in COMSOL Multiphysics, a finite element analysis software package. To expedite treatment planning, electric fields, power deposition and temperature rises were computed for a single straight antenna in 2D axisymmetric geometry. A precomputed library of electric field and temperature solutions was created for a range of insertion depths (5-12 cm) and blood perfusion rates (0.5-5 kg/m³/s). 3D models of multiple antennas and benchtop phantoms experiments using temperature-sensitive liquid crystal paper to monitor heating by curved antennas were performed for comparative evaluation of the treatment planning platform.

A patient-customizable hyperthermia treatment planning software package was developed in MATLAB with capabilities to interface with a commercial radiation therapy planning platform (Oncentra, Nucleotron), import patient and multicatheter implant geometries, calculate insertion depths, and perform hyperthermia planning with antennas operating in asynchronous or synchronous mode. During asynchronous operation, the net power deposition and temperature rises were approximated as a superposition sum of the respective quantities for one single antenna. During synchronous excitation, a superposition of complex electrical fields was performed with appropriate phasing to compute power deposition. Electric fields and temperatures from the pre-computed single-antenna library were utilized following appropriate non-rigid coordinate transformations. Comparison to 3D models indicated that superposition of electric fields around parallel antennas is valid when they are at least 15 mm apart. Phantom experiments with curved antennas produced temperature profiles quite similar to those created using the planning system.

The hyperthermia planning software allowed users to select power and phasing, assess the corresponding 3D contours of energy and temperature, and optimize treatment parameters through gradient search techniques. The system produces fairly accurate temperature distributions in cases when the antennas are at least 15 mm apart.

Proceedings Article | 11 March 2015 Paper

Development of an endoluminal high-intensity ultrasound applicator for image-guided thermal therapy of pancreatic tumors

Matthew Adams, Serena Scott, Vasant Salgaonkar, Peter Jones, Juan Plata-Camargo, Graham Sommer, Chris Diederich

Proceedings Volume 9326, 93260F (2015) https://doi.org/10.1117/12.2078841

KEYWORDS: Tumors, Transducers, Ultrasonography, Tissues, 3D modeling, Pancreas, Thermal modeling, Head, Stomach, Acoustics

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Proceedings Article | 26 February 2013 Paper

MR guided thermal therapy of pancreatic tumors with endoluminal, intraluminal and interstitial catheter-based ultrasound devices: preliminary theoretical and experimental investigations

Punit Prakash, Vasant Salgaonkar, Serena Scott, Peter Jones, Daniel Hensley, Andrew Holbrook, Juan Plata, Graham Sommer, Chris Diederich

Proceedings Volume 8584, 85840V (2013) https://doi.org/10.1117/12.2004669

KEYWORDS: Tumors, Ultrasonography, Tissues, Stomach, Magnetic resonance imaging, Transducers, Pancreas, Neodymium, 3D modeling, Acoustics

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Image-guided thermal interventions have been proposed for potential palliative and curative treatments of pancreatic tumors. Catheter-based ultrasound devices offer the potential for temporal and 3D spatial control of the energy deposition profile. The objective of this study was to apply theoretical and experimental techniques to investigate the feasibility of endogastric, intraluminal and transgastric catheter-based ultrasound for MR guided thermal therapy of pancreatic tumors. The transgastric approach involves insertion of a catheter-based ultrasound applicator (array of 1.5 mm OD x 10 mm transducers, 360° or sectored 180°, ~7 MHz frequency, 13-14G cooling catheter) directly into the pancreas, either endoscopically or via image-guided percutaneous placement. An intraluminal applicator, of a more flexible but similar construct, was considered for endoscopic insertion directly into the pancreatic or biliary duct. An endoluminal approach was devised based on an ultrasound transducer assembly (tubular, planar, curvilinear) enclosed in a cooling balloon which is endoscopically positioned within the stomach or duodenum, adjacent to pancreatic targets from within the GI tract. A 3D acoustic bio-thermal model was implemented to calculate acoustic energy distributions and used a FEM solver to determine the transient temperature and thermal dose profiles in tissue during heating. These models were used to determine transducer parameters and delivery strategies and to study the feasibility of ablating 1-3 cm diameter tumors located 2-10 mm deep in the pancreas, while thermally sparing the stomach wall. Heterogeneous acoustic and thermal properties were incorporated, including approximations for tumor desmoplasia and dynamic changes during heating. A series of anatomic models based on imaging scans of representative patients were used to investigate the three approaches. Proof of concept (POC) endogastric and transgastric applicators were fabricated and experimentally evaluated in tissue mimicking phantoms, ex vivo tissue and in vivo canine model under multi-slice MR thermometry. RF micro-coils were evaluated to enable active catheter-tracking and prescription of thermometry slice positions. Interstitial and intraluminal ultrasound applicators could be used to ablate (t₄₃>240min) tumors measuring 2.3-3.4 cm in diameter when powered with 20-30 W/cm² at 7 MHz for 5-10 min. Endoluminal applicators with planar and curvilinear transducers operating at 3-4 MHz could be used to treat tumors up to 20-25 mm deep from the stomach wall within 5 min. POC devices were fabricated and successfully integrated into the MRI environment with catheter tracking, real-time thermometry and closed-loop feedback control.

Proceedings Article | 26 February 2013 Paper

Interstitial ultrasound ablation of tumors within or adjacent to bone: Contributions of preferential heating at the bone surface

Serena Scott, Punit Prakash, Vasant Salgaonkar, Peter Jones, Richard Cam, Misung Han, Viola Rieke, E. Clif Burdette, Chris Diederich

Proceedings Volume 8584, 85840Z (2013) https://doi.org/10.1117/12.2002632

KEYWORDS: Bone, Tissues, Tumors, Ultrasonography, Natural surfaces, 3D modeling, Acoustics, Safety, Transducers, Lung

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Proceedings Article | 23 February 2011 Paper

Catheter-based ultrasound hyperthermia with HDR brachytherapy for treatment of locally advanced cancer of the prostate and cervix

Chris Diederich, Jeff Wootton, Punit Prakash, Vasant Salgaonkar, Titania Juang, Serena Scott, Xin Chen, Adam Cunha, Jean Pouliot, I. Hsu

Proceedings Volume 7901, 79010O (2011) https://doi.org/10.1117/12.876401

KEYWORDS: Ultrasonography, High dynamic range imaging, Cervix, Prostate, Transducers, Computing systems, Control systems, Amplifiers, Thermometry, Rectum

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A clinical treatment delivery platform has been developed and is being evaluated in a clinical pilot study for providing 3D controlled hyperthermia with catheter-based ultrasound applicators in conjunction with high dose rate (HDR) brachytherapy. Catheter-based ultrasound applicators are capable of 3D spatial control of heating in both angle and length of the devices, with enhanced radial penetration of heating compared to other hyperthermia technologies. Interstitial and endocavity ultrasound devices have been developed specifically for applying hyperthermia within HDR brachytherapy implants during radiation therapy in the treatment of cervix and prostate. A pilot study of the combination of catheter based ultrasound with HDR brachytherapy for locally advanced prostate and cervical cancer has been initiated, and preliminary results of the performance and heating distributions are reported herein. The treatment delivery platform consists of a 32 channel RF amplifier and a 48 channel thermocouple monitoring system. Controlling software can monitor and regulate frequency and power to each transducer section as required during the procedure. Interstitial applicators consist of multiple transducer sections of 2-4 cm length × 180 deg and 3-4 cm × 360 deg. heating patterns to be inserted in specific placed 13g implant catheters. The endocavity device, designed to be inserted within a 6 mm OD plastic tandem catheter within the cervix, consists of 2-3 transducers × dual 180 or 360 deg sectors. 3D temperature based treatment planning and optimization is dovetailed to the HDR optimization based planning to best configure and position the applicators within the catheters, and to determine optimal base power levels to each transducer section. To date we have treated eight cervix implants and six prostate implants. 100 % of treatments achieved a goal of >60 min duration, with therapeutic temperatures achieved in all cases. Thermal dosimetry within the hyperthermia target volume (HTV) and clinical target volume (CTV) are reported. Catheter-based ultrasound hyperthermia with HDR appears feasible with therapeutic temperature coverage of the target volume within the prostate or cervix while sparing surrounding more sensitive regions.

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