Imaging Modality For Guidance Research Articles

TU‐B‐201‐00: TG180: Imaging Dose During RT

Radiotherapy is in the era of image guided radiation therapy (IGRT) in which imaging procedures are routinely performed for patient positioning, and target localization. The additional imaging dose delivered may increase risk to the patient and therefore needs to be managed. This lecture provides an overview of the AAPM TG‐180 which is charged with: providing an overview on imaging dose including megavoltage electronic portal imaging (MV EPI), kilovoltage digital radiography (kV DR), Tomotherapy MV‐CT, megavoltage cone‐beam CT (MV‐CBCT) and kilovoltage cone‐beam CT (kV‐CBCT) as well as providing general guidelines for commissioning and managing imaging dose calculations. The dose to radiotherapy (RT) patients resulting from different image guidance procedures is reviewed and recommendations for managing the imaging dose are provided. Different techniques for reducing the image guidance dose are summarized. A recommended threshold beyond which imaging dose should be considered in the treatment planning process is discussed. This lecture also discusses kilovoltage imaging dose determination by calculation and estimation, and inclusion in treatment planning as well as accounting for MV imaging dose and the future of MV imaging. Learning Objectives: Learn the different image guidance modalities, typical organ doses resulting from different image procedures, and techniques to reduce the imaging dose; Understand the imaging dose threshold and rationale for accounting for the imaging dose; Learn how to account for kV imaging dose Learn how to account for MV imaging dose and understand the future of MV imaging

TU‐B‐201‐02: Accounting for KV Imaging Dose

Radiotherapy is in the era of image guided radiation therapy (IGRT) in which imaging procedures are routinely performed for patient positioning, and target localization. The additional imaging dose delivered may increase risk to the patient and therefore needs to be managed. This lecture provides an overview of the AAPM TG‐180 which is charged with: providing an overview on imaging dose including megavoltage electronic portal imaging (MV EPI), kilovoltage digital radiography (kV DR), Tomotherapy MV‐CT, megavoltage cone‐beam CT (MV‐CBCT) and kilovoltage cone‐beam CT (kV‐CBCT) as well as providing general guidelines for commissioning and managing imaging dose calculations. The dose to radiotherapy (RT) patients resulting from different image guidance procedures is reviewed and recommendations for managing the imaging dose are provided. Different techniques for reducing the image guidance dose are summarized. A recommended threshold beyond which imaging dose should be considered in the treatment planning process is discussed. This lecture also discusses kilovoltage imaging dose determination by calculation and estimation, and inclusion in treatment planning as well as accounting for MV imaging dose and the future of MV imaging. Learning Objectives: Learn the different image guidance modalities, typical organ doses resulting from different image procedures, and techniques to reduce the imaging dose; Understand the imaging dose threshold and rationale for accounting for the imaging dose; Learn how to account for kV imaging dose Learn how to account for MV imaging dose and understand the future of MV imaging

Radiolucent 4D Ultrasound Imaging: System Design and Application to Radiotherapy Guidance.

Four-dimensional (4D) ultrasound (US) is an attractive modality for image guidance due to its real-time, non-ionizing, volumetric imaging capability with high soft tissue contrast. However, existing 4D US imaging systems contain large volumes of metal which interfere with diagnostic and therapeutic ionizing radiation in procedures such as CT imaging and radiation therapy. This study aimed to design and characterize a novel 4D Radiolucent Remotely-Actuated UltraSound Scanning (RRUSS) device that overcomes this limitation. In a phantom, we evaluated the imaging performance of the RRUSS device including frame rate, resolution, spatial integrity, and motion tracking accuracy. To evaluate compatibility with radiation therapy workflow, we evaluated device-induced CT imaging artifacts, US tracking performance during beam delivery, and device compatibility with commercial radiotherapy planning software. The RRUSS device produced 4D volumes at 0.1-3.0 Hz with 60° lateral field of view (FOV), 50° maximum elevational FOV, and 200 mm maximum depth. Imaging resolution (-3 dB point spread width) was 1.2-7.9 mm at depths up to 100 mm and motion tracking accuracy was ≤ 0.3±0.5 mm. No significant effect of the RRUSS device on CT image integrity was found, and RRUSS device performance was not affected by radiotherapy beam exposure. Agreement within ±3.0% / 2.0 mm was achieved between computed and measured radiotherapy dose delivered directly through the RRUSS device at 6 MV and 15 MV. In vivo liver, kidney, and prostate images were successfully acquired. Our investigations suggest that a RRUSS device can offer non-interfering 4D guidance for radiation therapy and other diagnostic and therapeutic procedures.

The effect of body mass index on fluoroscopic time and radiation dose during lumbar transforaminal epidural steroid injections

ObjectiveTransforaminal epidural steroid injections (TFESIs) are a commonly used, effective treatment for radicular pain. Accurate delivery of the injected medication helps to ensure maximum therapeutic efficacy and to decrease possible adverse events, and fluoroscopy is the preferred and most common image-guidance modality used to ensure accurate needle placement during lumbar TFESIs. However, fluoroscopic-guided lumbar TFESIs put patients at risk because of radiation exposure. The purpose of this study was to determine the relationship between body mass index (BMI) and fluoroscopy time and radiation dose during lumbar TFESIs. DesignA retrospective study design was used. SettingThe study was conducted at an academic orthopedic center. All procedures were performed by physicians board-certified in Physical Medicine and Rehabilitation (PM&R) and with subspecialty certification in sports medicine, or by a trainee under close supervision from an attending physician. ParticipantsParticipants were patients who underwent fluoroscopic-guided lumbar TFESIs between February 2013 and March 2015 with a documented height/weight, fluoroscopy time, and radiation dose. InterventionsAll patients received unilateral or bilateral lumbar TFESIs with fluoroscopic guidance. Fluoroscopy time and dose were recorded. Main Outcome MeasuresThe main outcome measures were fluoroscopy time and radiation dose. A Bonferroni correction was implemented for multiple comparisons, defining statistical significance at p<.01. ResultsA total of 2,443 injections were performed on 1,548 patients. There were 419 normal, 572 overweight, and 557 obese patients, respectively. There were 1,426 first-time injections and 1,017 repeat injections. Sixty-nine percent (1,681) were unilateral injections, and 26.4% (645) were single level injections. A trainee was involved in 1,361 (55.7%) of the injections performed. The mean fluoroscopy time for all injections was 30.0±17.5 seconds, and the mean radiation dose was 2,164±1,484 mGy-cm2. The mean fluoroscopy time was 27.7±15.2 seconds for normal weight patients, 30.0±21.0 seconds for overweight patients, and 32.2±15.1 seconds for obese patients, showing a significant difference between groups (p<.001). The mean radiation doses for each group were 1,376±450, 1,911±653, and 3,029±640 mGy-cm2, respectively, with a significant increase in radiation dose with increasing BMI (p<.001). ConclusionsThe findings of this study demonstrate that fluoroscopy radiation dose and fluoroscopy time during lumbar TFESIs are increased in patients with an elevated BMI, and in patients of greater age, but the presence of a trainee had no effect on fluoroscopy time.

Percutaneous biopsy in the abdomen and pelvis: a step-by-step approach.

Percutaneous abdominal biopsies provide referring physicians with valuable diagnostic and prognostic information that guides patient care. All biopsy procedures follow a similar process that begins with the preprocedure evaluation of the patient and ends with the postprocedure management of the patient. In this review, a step-by-step approach to both routine and challenging abdominal biopsies is covered with an emphasis on the differences in biopsy devices and imaging guidance modalities. Adjunctive techniques that may facilitate accessing a lesion in a difficult location or reduce procedure risk are described. An understanding of these concepts will help maintain the favorable safety profile and high diagnostic yield associated with percutaneous biopsies.

Commissioning a Next-Generation Treatment Planning System for Adaptive Radiation Therapy

Image-guided radiotherapy allows monitoring patients’ tumour response, weight loss, organ filling and shape changes (e.g. neck flexion, lung motion). Incorporating anatomic deformations into dose distributions may enable informed adaptive re-planning and improved therapeutic ratios. Deformable image registration is needed to track tissue motion on a voxel-by-voxel basis prior to adaptive re-planning. The purpose of this study was to quantify the geometric accuracy of novel deformable registration algorithms. A new treatment planning system (RayStation, RaySearch Laboratories), undergoing testing at our institution, contains 2 novel deformable image registration algorithms: a contour-based algorithm (driven by organ contours between image pairs) and a hybrid algorithm (additionally driven by maximizing the similarity between voxel grey-values). The algorithms were tested as follows. First, digital phantoms were created by warping 5 CT images (3 pelvis, 2 head and neck, 1 lung) with known deformations. The original images were then recovered using RayStation’s registration algorithms. Accuracy was quantified as the voxel-by-voxel displacement differences throughout the images. Second, patient datasets (n=74, liver/lung 4DCT and MR/MR, liver CT-MR, prostate MR-MR) were registered using both algorithms. Accuracy of the patient data was quantified by measuring the residual distances of contours and point landmarks between the deformed (i.e. registered) images and the actual patient images. Typical image resolution was 2-3 mm for CT, and 3-6 mm for MR. For the phantom CT data, the 95th percentile of errors for the contours distance-to-agreement ranged from 0.5-1.9 mm for the hybrid algorithm and 0.5-3.9 mm for the contour-based algorithm. Both algorithms had internal displacement errors >5 mm in nearly all cases, indicating contour alignment does not guarantee accurate internal organ registration. For the patient data, both registration algorithms achieved mean contour distance-to-agreements <2 mm for the liver/lung 4DCT, liver CT-MR and prostate MR, and <3.5 mm for the liver/lung MR. The internal organ target registration error was measured using anatomic point landmarks (median: 5 liver, 60 lungs, 3 prostate). The internal accuracy for the contour-based algorithm was consistently within the image resolution across all data (mean errors: 2.7-4.4 mm). The hybrid algorithm’s accuracy varied widely (means errors: 2.7-3.3 mm for liver/lung 4DCT, 3.9 mm for prostate MR, 8.2-12.0 mm for liver CT-MR and liver/lung 4DCT), exceeding the image resolution when MR data was used. RayStation’s novel deformable registration technology was evaluated. To ensure the registration errors are within the image resolution, the choice of algorithm depends on the anatomic site and modality of image-guidance (e.g. CT, cone-beam CT, MR). Deformable image registration technology allows dynamic patient motion to be incorporated into dose distributions, facilitating the clinical implementation of adaptive radiotherapy.

Disruption of the Tumor Vasculature Using Combined Radiation and Ultrasound-stimulated Microbubbles: Preliminary Preclinical Results in Human Prostate Xenografts

by organ contours between image pairs) and a hybrid algorithm (additionally driven by maximizing the similarity between voxel grey-values). The algorithms were tested as follows. First, digital phantoms were created by warping 5 CT images (3 pelvis, 2 head and neck, 1 lung) with known deformations. The original images were then recovered using RayStation’s registration algorithms. Accuracy was quantified as the voxel-by-voxel displacement differences throughout the images. Second, patient datasets (n1⁄474, liver/ lung 4DCT and MR/MR, liver CT-MR, prostate MR-MR) were registered using both algorithms. Accuracy of the patient data was quantified by measuring the residual distances of contours and point landmarks between the deformed (i.e. registered) images and the actual patient images. Typical image resolution was 2-3 mm for CT, and 3-6 mm for MR. Results/Benefits/Challenges: For the phantom CT data, the 95th percentile of errors for the contours distance-to-agreement ranged from 0.5-1.9 mm for the hybrid algorithm and 0.5-3.9 mm for the contour-based algorithm. Both algorithms had internal displacement errors >5 mm in nearly all cases, indicating contour alignment does not guarantee accurate internal organ registration. For the patient data, both registration algorithms achieved mean contour distance-to-agreements <2 mm for the liver/lung 4DCT, liver CT-MR and prostate MR, and <3.5 mm for the liver/lung MR. The internal organ target registration error was measured using anatomic point landmarks (median: 5 liver, 60 lungs, 3 prostate). The internal accuracy for the contour-based algorithm was consistently within the image resolution across all data (mean errors: 2.7-4.4 mm). The hybrid algorithm’s accuracy varied widely (means errors: 2.7-3.3 mm for liver/lung 4DCT, 3.9 mm for prostate MR, 8.2-12.0 mm for liver CT-MR and liver/lung 4DCT), exceeding the image resolution when MR data was used. Conclusion/Impact/Outcomes: RayStation’s novel deformable registration technology was evaluated. To ensure the registration errors are within the image resolution, the choice of algorithm depends on the anatomic site and modality of image-guidance (e.g. CT, cone-beam CT, MR). Deformable image registration technology allows dynamic patient motion to be incorporated into dose distributions, facilitating the clinical implementation of adaptive radiotherapy.

Optimizing modality selection for image-guided procedures: an analysis of the challenges to ultrasound guidance.

Selection of the most appropriate modality for image guidance is essential for procedural success. We identified specific factors contributing to failure of ultrasound-guided procedures that were subsequently performed using CT guidance. This single-center, retrospective study included 164 patients who underwent a CT-guided biopsy, aspiration/drainage, or ablation after initially having the same procedure attempted unsuccessfully with ultrasound guidance. Review of the procedure images, reports, biopsy results, and clinical follow-up was performed and the reasons for inability to perform the procedure with ultrasound guidance were recorded. Patient cross-sectional area and depth to target were calculated. Differences in area and depth were compared using general linear modeling. Depth as a predictor of an unfavorable body habitus designation was modeled using logistic regression. US guidance was successful in the vast majority of cases (97%). Of the 164 procedures, there were 92 (56%) biopsies, 63 (38%) aspirations/drainages, and 9 (5%) ablations. The most common reason for procedure failure was poor acoustic window (83/164, 51%). Other reasons included target lesion being poorly discerned from adjacent tissue (61/164, 37%), adjacent bowel gas (34/164, 21%), body habitus (27/164, 16%), and gas-containing collection (22/164, 13%). Within the biopsy subgroup, patients for whom body habitus was a limiting factor were found to have on average a larger cross-sectional area and lesion depth relative to patients whose body habitus was not a complicating factor (p<0.0001 and p=0.0009). Poor acoustic window was the most common reason for procedural failure with ultrasound guidance. In addition, as lesion depth increased, the odds that body habitus would limit the procedure also increased. If preliminary imaging suggests a limited sonographic window, particularly for deeper lesions, proceeding directly to CT guidance should be considered.

Three-dimensional assessment of pedicular screws in thoracic and lumbar fractures using free-hand technique: a single-surgeon experience

Introduction Several sophisticated image-guided modalities have been developed to improve the accuracy of screw placement; however, such modalities may increase healthcare costs and radiation exposure to the patient, and the clinical efficacy compared with traditional techniques may be questionable. Globally, the free-hand technique of pedicle screw placement was found to be a reliable and safe method with low rates of complications and to be potentially more cost-effective than other sophisticated techniques in treating several spinal disorders. Aim The aim of this work was to assess the accuracy and safety of free-hand pedicle screw placement in thoracic and lumbar fractures using minimal image exposure. Materials and methods This is a prospective radiographic review of thoracic and lumbar pedicle screws inserted in patients suffering from unstable fractures. All of the procedures were performed by a single consultant spine surgeon. Screws were inserted at one side and then intraoperative lateral imaging was used to check the level and verify the position of the screws. The same procedure was repeated on the other side. The vertebral bodies were divided into three equidistant horizontal zones (A, B, and C). Positioning of the screw tips was regarded as ideal when located in zones A and B. Multislice computed tomography was used to assess the accuracy. Results There were 669 pedicle screws inserted in 88 consecutive cases from T3 to L5, with a mean of 7.6 screws. The overall number of misplaced screws was nine (1.3%). Intraoperative revision was made in 16 (seven cases, 2.4%) screws. No intraoperative or immediate postoperative complication occurred due to screw placement. Conclusion Minimal revision rate was noticed, and only two lateral images were needed in most of the cases. This is quite important in developing countries, where an image intensifier serves more than one room.

Simulating temperature distribution of high-intensity focused ultrasound during bone treatments

To help improve therapeutic results for treatment of bone tumors, high intensity focused ultrasound (HIFU) is being investigated as a non-invasive alternative to surgery and radiotherapy. HIFU ablative treatments require an imaging modality for guidance, and magnetic resonance (MR) imaging is currently the strongest choice as it is able to provide temperature mapping throughout the treatment process. Unfortunately, the temperature feedback that is critical to ensuring safety and optimal soft tissue ablation is often unobtainable in bone structures. As an alternative to obtaining feedback, this project is focused on developing a simulator that is capable of predicting the temperature distribution in and around bone tissue during HIFU therapy. Having such a simulation would provide a better understanding of the thermal dosages incurred by the bone during HIFU treatment of tumors.

TH-C-BRD-00: Optimization of CT Planning Imaging and Techniques to Reduce Radiation Dose Resulting From Daily Imaging Guidance Procedures

IGRT has significantly improved the accuracy of radiation treatment by utilizing CT scans for contouring target and organ during treatment planning and x-ray imaging devices integrated to treatment units for patient positioning during radiation delivery. A significant progress has been made recently to improve CT image quality in treatment planning and to reduce daily imaging guidance dose. This course is designed to provide educational guidance on these two important imaging issues. I) Optimization of CT Simulation Imaging. This part will provide guidance on optimizing CT image quality in radiation therapy. There have been many publications on optimizing CT protocols for diagnostic imaging purposes. However, the effort to optimize CT protocols for imaging applications in radiation therapy has been limited. Although some lessons we learn from diagnostic CT imaging can be applied to CT imaging in radiation therapy, there should be more emphasis on task-based image quality. In addition, there are imaging features widely used in diagnostic CT imaging (e.g., metal artifact reduction) may not be well known in radiation therapy community but can play critical roles for accurate radiation treatment planning. This part of the session will feature a conversation between a radiation therapy physicist and a diagnostic imaging physicist focusing on the needs specific to CT simulation imaging in radiation therapy and the approaches to address these needs. II) Techniques to reduce radiation dose resulting from daily imaging guidance procedures. This part will provide an overview of radiation dose to patients resulting from different image devices used in image-guided procedures and provide guidance on the techniques available to reduce imaging dose resulting from daily imaging guidance procedures. Depending on the image modality including MV and kV imaging devices, a variety of techniques are available to significantly reduce daily imaging guidance dose to organs at risk. Different methods of accounting for the imaging doses will be discussed. Learning Objectives: 1. Understand CT image quality needs specific to imaging applications in radiation therapy 2. Learn the imaging acquisition and reconstruction optimization for CT imaging applications in radiation therapy 3. Discuss appropriate approaches to optimize CT protocols in radiation therapy; 4. Briefly review the typical radiation dose to patients resulting from different image-guided procedures MV and kV imaging modalities; 5. Understand the techniques available to reduce imaging dose 6. Discuss different methods of accounting for the imaging doses

TH-C-BRD-01: Optimization of CT Simulation Imaging in Radiation Therapy: Background and Motivations

IGRT has significantly improved the accuracy of radiation treatment by utilizing CT scans for contouring target and organ during treatment planning and x-ray imaging devices integrated to treatment units for patient positioning during radiation delivery. A significant progress has been made recently to improve CT image quality in treatment planning and to reduce daily imaging guidance dose. This course is designed to provide educational guidance on these two important imaging issues. I) Optimization of CT Simulation Imaging. This part will provide guidance on optimizing CT image quality in radiation therapy. There have been many publications on optimizing CT protocols for diagnostic imaging purposes. However, the effort to optimize CT protocols for imaging applications in radiation therapy has been limited. Although some lessons we learn from diagnostic CT imaging can be applied to CT imaging in radiation therapy, there should be more emphasis on task-based image quality. In addition, there are imaging features widely used in diagnostic CT imaging (e.g., metal artifact reduction) may not be well known in radiation therapy community but can play critical roles for accurate radiation treatment planning. This part of the session will feature a conversation between a radiation therapy physicist and a diagnostic imaging physicist focusing on the needs specific to CT simulation imaging in radiation therapy and the approaches to address these needs. II) Techniques to reduce radiation dose resulting from daily imaging guidance procedures. This part will provide an overview of radiation dose to patients resulting from different image devices used in image-guided procedures and provide guidance on the techniques available to reduce imaging dose resulting from daily imaging guidance procedures. Depending on the image modality including MV and kV imaging devices, a variety of techniques are available to significantly reduce daily imaging guidance dose to organs at risk. Different methods of accounting for the imaging doses will be discussed. Learning Objectives: 1. Understand CT image quality needs specific to imaging applications in radiation therapy 2. Learn the imaging acquisition and reconstruction optimization for CT imaging applications in radiation therapy 3. Discuss appropriate approaches to optimize CT protocols in radiation therapy; 4. Briefly review the typical radiation dose to patients resulting from different image-guided procedures MV and kV imaging modalities; 5. Understand the techniques available to reduce imaging dose 6. Discuss different methods of accounting for the imaging doses

TH-C-BRD-03: Techniques to Reduce Radiation Dose Resulting From Daily Imaging Guidance Procedures

IGRT has significantly improved the accuracy of radiation treatment by utilizing CT scans for contouring target and organ during treatment planning and x-ray imaging devices integrated to treatment units for patient positioning during radiation delivery. A significant progress has been made recently to improve CT image quality in treatment planning and to reduce daily imaging guidance dose. This course is designed to provide educational guidance on these two important imaging issues. I) Optimization of CT Simulation Imaging. This part will provide guidance on optimizing CT image quality in radiation therapy. There have been many publications on optimizing CT protocols for diagnostic imaging purposes. However, the effort to optimize CT protocols for imaging applications in radiation therapy has been limited. Although some lessons we learn from diagnostic CT imaging can be applied to CT imaging in radiation therapy, there should be more emphasis on task-based image quality. In addition, there are imaging features widely used in diagnostic CT imaging (e.g., metal artifact reduction) may not be well known in radiation therapy community but can play critical roles for accurate radiation treatment planning. This part of the session will feature a conversation between a radiation therapy physicist and a diagnostic imaging physicist focusing on the needs specific to CT simulation imaging in radiation therapy and the approaches to address these needs. II) Techniques to reduce radiation dose resulting from daily imaging guidance procedures. This part will provide an overview of radiation dose to patients resulting from different image devices used in image-guided procedures and provide guidance on the techniques available to reduce imaging dose resulting from daily imaging guidance procedures. Depending on the image modality including MV and kV imaging devices, a variety of techniques are available to significantly reduce daily imaging guidance dose to organs at risk. Different methods of accounting for the imaging doses will be discussed. Learning Objectives: 1. Understand CT image quality needs specific to imaging applications in radiation therapy 2. Learn the imaging acquisition and reconstruction optimization for CT imaging applications in radiation therapy 3. Discuss appropriate approaches to optimize CT protocols in radiation therapy; 4. Briefly review the typical radiation dose to patients resulting from different image-guided procedures MV and kV imaging modalities; 5. Understand the techniques available to reduce imaging dose 6. Discuss different methods of accounting for the imaging doses

TH-C-BRD-02: Optimization of CT Simulation Imaging in Radiation Therapy: Strategies and Tools

IGRT has significantly improved the accuracy of radiation treatment by utilizing CT scans for contouring target and organ during treatment planning and x-ray imaging devices integrated to treatment units for patient positioning during radiation delivery. A significant progress has been made recently to improve CT image quality in treatment planning and to reduce daily imaging guidance dose. This course is designed to provide educational guidance on these two important imaging issues. I) Optimization of CT Simulation Imaging. This part will provide guidance on optimizing CT image quality in radiation therapy. There have been many publications on optimizing CT protocols for diagnostic imaging purposes. However, the effort to optimize CT protocols for imaging applications in radiation therapy has been limited. Although some lessons we learn from diagnostic CT imaging can be applied to CT imaging in radiation therapy, there should be more emphasis on task-based image quality. In addition, there are imaging features widely used in diagnostic CT imaging (e.g., metal artifact reduction) may not be well known in radiation therapy community but can play critical roles for accurate radiation treatment planning. This part of the session will feature a conversation between a radiation therapy physicist and a diagnostic imaging physicist focusing on the needs specific to CT simulation imaging in radiation therapy and the approaches to address these needs. II) Techniques to reduce radiation dose resulting from daily imaging guidance procedures. This part will provide an overview of radiation dose to patients resulting from different image devices used in image-guided procedures and provide guidance on the techniques available to reduce imaging dose resulting from daily imaging guidance procedures. Depending on the image modality including MV and kV imaging devices, a variety of techniques are available to significantly reduce daily imaging guidance dose to organs at risk. Different methods of accounting for the imaging doses will be discussed. Learning Objectives: 1. Understand CT image quality needs specific to imaging applications in radiation therapy 2. Learn the imaging acquisition and reconstruction optimization for CT imaging applications in radiation therapy 3. Discuss appropriate approaches to optimize CT protocols in radiation therapy; 4. Briefly review the typical radiation dose to patients resulting from different image-guided procedures MV and kV imaging modalities; 5. Understand the techniques available to reduce imaging dose 6. Discuss different methods of accounting for the imaging doses

TU-A-210-01: HIFU Physics and Delivery

High-intensity focused ultrasound (HIFU) has developed rapidly in recent years and is used frequently for clinical treatments in Asia and Europe with increasing clinical use and clinical trial activity in the US, making it an important medical technology with which the medical physics community must become familiar. Akin to medical devices that deliver treatments using ionizing radiation, HIFU relies on emitter geometry to non-invasively form a tight focus that can be used to affect diseased tissue while leaving healthy tissue intact. HIFU is unique in that it does not involve the use of ionizing radiation, it causes thermal necrosis in 100% of the treated tissue volume, and it has an immediate treatment effect. However, because it is an application of ultrasound energy, HIFU interacts strongly with tissue interfaces, which makes treatment planning challenging. In order to appreciate the advantages and disadvantages of HIFU as a thermal therapy, it is important to understand the underlying physics of ultrasound tissue interactions. The first lecture in the session will provide an overview of the physics of ultrasound wave propagation; the mechanism for the accumulation of heat in soft-tissue; image-guidance modalities including temperature monitoring; current clinical applications and commercial devices; active clinical trials; alternate mechanisms of action (future of FUS). The second part of the session will compare HIFU to existing ionization radiation techniques. The difficulties in defining a clear concept of absorbed dose for HIFU will be discussed. Some of the technical challenges that HIFU faces will be described, with an emphasis on how the experience of radiation oncology physicists could benefit the field. Learning Objectives: 1. Describe the basic physics and biology of HIFU, including treatment delivery and image guidance techniques. 2. Summarize existing and emerging clinical applications and manufacturers for HIFU. 3. Understand that thermal ablation with HIFU is likely the first of several applications of the technology 4. Learn about some similarities and differences between HIFU and ionizing radiation in terms of physics and biological effects. 5. Learn about some of the technical challenges HIFU faces that might benefit from the experience of radiation oncology physicists including treatment planning improvements, quality assurance procedures, and treatment risk analysis. David Schlesinger receives research support from Elekta Instruments, AB. Matt Eames is an employee of the Focused Ultrasound Foundation which supports research and clinical trials. Dr. Eames conducts research which is supported by the Focused Ultrasound Foundation.

TU-A-210-02: HIFU: Why Should a Radiation Oncology Physicist Pay Attention?

High-intensity focused ultrasound (HIFU) has developed rapidly in recent years and is used frequently for clinical treatments in Asia and Europe with increasing clinical use and clinical trial activity in the US, making it an important medical technology with which the medical physics community must become familiar. Akin to medical devices that deliver treatments using ionizing radiation, HIFU relies on emitter geometry to non-invasively form a tight focus that can be used to affect diseased tissue while leaving healthy tissue intact. HIFU is unique in that it does not involve the use of ionizing radiation, it causes thermal necrosis in 100% of the treated tissue volume, and it has an immediate treatment effect. However, because it is an application of ultrasound energy, HIFU interacts strongly with tissue interfaces, which makes treatment planning challenging. In order to appreciate the advantages and disadvantages of HIFU as a thermal therapy, it is important to understand the underlying physics of ultrasound tissue interactions. The first lecture in the session will provide an overview of the physics of ultrasound wave propagation; the mechanism for the accumulation of heat in soft-tissue; image-guidance modalities including temperature monitoring; current clinical applications and commercial devices; active clinical trials; alternate mechanisms of action (future of FUS). The second part of the session will compare HIFU to existing ionization radiation techniques. The difficulties in defining a clear concept of absorbed dose for HIFU will be discussed. Some of the technical challenges that HIFU faces will be described, with an emphasis on how the experience of radiation oncology physicists could benefit the field. Learning Objectives: 1. Describe the basic physics and biology of HIFU, including treatment delivery and image guidance techniques. 2. Summarize existing and emerging clinical applications and manufacturers for HIFU. 3. Understand that thermal ablation with HIFU is likely the first of several applications of the technology 4. Learn about some similarities and differences between HIFU and ionizing radiation in terms of physics and biological effects. 5. Learn about some of the technical challenges HIFU faces that might benefit from the experience of radiation oncology physicists including treatment planning improvements, quality assurance procedures, and treatment risk analysis. David Schlesinger receives research support from Elekta Instruments, AB. Matt Eames is an employee of the Focused Ultrasound Foundation which supports research and clinical trials. Dr. Eames conducts research which is supported by the Focused Ultrasound Foundation.

TU-A-210-00: HIFU Therapies - A Primer

High-intensity focused ultrasound (HIFU) has developed rapidly in recent years and is used frequently for clinical treatments in Asia and Europe with increasing clinical use and clinical trial activity in the US, making it an important medical technology with which the medical physics community must become familiar. Akin to medical devices that deliver treatments using ionizing radiation, HIFU relies on emitter geometry to non-invasively form a tight focus that can be used to affect diseased tissue while leaving healthy tissue intact. HIFU is unique in that it does not involve the use of ionizing radiation, it causes thermal necrosis in 100% of the treated tissue volume, and it has an immediate treatment effect. However, because it is an application of ultrasound energy, HIFU interacts strongly with tissue interfaces, which makes treatment planning challenging. In order to appreciate the advantages and disadvantages of HIFU as a thermal therapy, it is important to understand the underlying physics of ultrasound tissue interactions. The first lecture in the session will provide an overview of the physics of ultrasound wave propagation; the mechanism for the accumulation of heat in soft-tissue; image-guidance modalities including temperature monitoring; current clinical applications and commercial devices; active clinical trials; alternate mechanisms of action (future of FUS). The second part of the session will compare HIFU to existing ionization radiation techniques. The difficulties in defining a clear concept of absorbed dose for HIFU will be discussed. Some of the technical challenges that HIFU faces will be described, with an emphasis on how the experience of radiation oncology physicists could benefit the field. Learning Objectives: 1. Describe the basic physics and biology of HIFU, including treatment delivery and image guidance techniques. 2. Summarize existing and emerging clinical applications and manufacturers for HIFU. 3. Understand that thermal ablation with HIFU is likely the first of several applications of the technology 4. Learn about some similarities and differences between HIFU and ionizing radiation in terms of physics and biological effects. 5. Learn about some of the technical challenges HIFU faces that might benefit from the experience of radiation oncology physicists including treatment planning improvements, quality assurance procedures, and treatment risk analysis. David Schlesinger receives research support from Elekta Instruments, AB. Matt Eames is an employee of the Focused Ultrasound Foundation which supports research and clinical trials. Dr. Eames conducts research which is supported by the Focused Ultrasound Foundation.

Application of Multiple Novel Imaging Modalities for Guidance and Treatment of the Patient with Subaortic Stenosis

Discrete Subvalvar Aortic Stenosis (DSS) is an uncommon acquired cause of left ventricular outflow tract obstruction (LVOT) and often found during Transthoracic Echocardiography (TTE). The membranes are located adjacent to the Aortic Valve (AV) or extended to the anterior leaflet of the mitral valve. The high-velocity systolic jet collides and damages the AV leaflets making the valve more likely to fail and more susceptible to clot and vegetation formation. There is an increased risk of moderate to severe Aortic Insufficiency (AI) when the peak LVOT gradient reaches >50mmHg. The clinical course of subvalvar aortic stenosis is generally progressive with increasing obstruction and progression of AI. Surgical resection of the fibrous ridge with myomectomy is the treatment of choice. The DSS was discovered unexpectedly in this 42 year-old white male with a past medical history of ascending aortic aneurysm, diabetes, hypertension and hyperlipidemia. He was admitted with chest pain, shortness of breath and syncope. TTE showed normal left ventricle with calcified and thickened AV. Peak LVOT gradient was 48mmHg. Due to poor acoustic window, Transesophageal Echocardiogram (TEE) with real time 3-dimensional imaging (RT3D-TEE) was performed. TEE revealed a membranous structure located in the LVOT below a severely calcified AV. Doppler study revealed peak LVOT gradient of 57mmHg with a mean gradient of 38mmHg. Severe AI was also noted. Patient received a #25mm porcine valve with resection of the subaortic membrane and septal myomectomy. Pathology report revealed rubbery, fibromembranous tissue, consistent with DSS. Patient did well after surgery and was discharged home in 4 days. Application of multiple novel imaging modalities, such as TEE and RT-3D-TEE allowed us to better characterize the structure of the DSS and provide guidance for better surgical outcome.

The status of contemporary image-guided modalities in oncologic surgery.

To review the current trends in optical imaging to guide oncologic surgery. Surgical resection remains the cornerstone of therapy for patients with early stage solid malignancies and more than half of all patients with cancer undergo surgery each year. The technical ability of the surgeon to obtain clear surgical margins at the initial resection remains crucial to improve overall survival and long-term morbidity. Current resection techniques are largely based on subjective and subtle changes associated with tissue distortion by invasive cancer. As a result, positive surgical margins occur in a significant portion of tumor resections, which is directly correlated with a poor outcome. A comprehensive review of studies evaluating optical imaging techniques is performed. A variety of cancer imaging techniques have been adapted or developed for intraoperative surgical guidance that have been shown to improve functional and oncologic outcomes in randomized clinical trials. There are also a large number of novel, cancer-specific contrast agents that are in early stage clinical trials and preclinical development that demonstrate significant promise to improve real-time detection of subclinical cancer in the operative setting. There has been an explosion of intraoperative imaging techniques that will become more widespread in the next decade.

Comparison of the Diagnostic Yield of Cytology and Concurrent Surgical Pathology Specimens by Novel Electromagnetic Navigation Bronchoscopy

Introduction: Rapid on-site evaluation of specimen adequacy is used at many institutions to enhance diagnostic yield. Cytology personnel began routinely performing ROSE at our institution in 2010. The aim of this study is to determine the effect of ROSE on diagnostic yield at our institution. Materials and Methods: Two 4 month time periods in which the majority of bronchoscopic cytology samples were obtained either with or without ROSE were selected. All bronchoscopic procedures were included whether or not real time image guidance was used. Image-guided modalities including fluoroscopy, endobronchial ultrasound-guided FNA (EBUS) and electromagnetic navigation bronchoscopy (ENB) were used during both periods. The pre-ROSE time period was 1/1/09-4/30/09 and the postROSE time period was 1/1/12 4/30/12. The following data were collected: final diagnosis, number of non-diagnostic samples, number of slides per case, use of ancillary testing and number of patients requiring additional procedures. Unsatisfactory/non-diagnostic samples and all atypical categories were considered non-diagnostic. All procedures after the initial procedure were considered additional until a conclusive diagnosis was rendered. Pearson’s Chi-squared test with Yates’ continuity correction was used to determine statistical significances. Results: A total of 151 procedures were performed pre-ROSE and 246 procedures post-ROSE. Specific diagnostic categories and use of ancillary testing are summarized in Table 1. Comparison of diagnostic and non-diagnostic cases and additional diagnostic procedures performed are summarized in Table 2. Conclusions: There were significantly fewer non-diagnostic bronchoscopic samples in the post-ROSE period. Use of ancillary studies increased significantly in the post-ROSE period with more malignancies given a specific cell type. The number of additional procedures performed for definitive diagnosis decreased in the post-ROSE time period. Correlation of impact of ROSE on specific imaging modalities used in bronchoscopy is warranted