Sook Kien Ng

Stereotactic body radiation therapy in pancreatic cancer: the new frontier.

Pancreatic cancer (PCA) remains a disease with a poor prognosis. The majority of PCA patients are unable to undergo surgical resection, which is the only potentially curative option at this time. A combination of chemotherapy and chemoradiation (CRT) are standard options for patients with locally advanced, unresectable disease, however, local control and patient outcomes remains poor. Stereotactic body radiation therapy (SBRT) is an emerging treatment option for PCA. SBRT delivers potentially ablative doses to the pancreatic tumor plus a small margin over a short period of time. Early studies with single-fraction SBRT demonstrated excellent tumor control with high rates of toxicity. The implementation of SBRT (3–5 doses) has demonstrated promising outcomes with favorable tumor control and toxicity rates. Herein we discuss the evolving role of SBRT in PCA treatment.

High-dose-rate intraoperative radiation therapy: The nuts and bolts of starting a program

High-dose-rate intraoperative radiation therapy (HDR-IORT) has historically provided effective local control (LC) for patients with unresectable and recurrent tumors. However, IORT is limited to only a few specialized institutions and it can be difficult to initiate an HDR-IORT program. Herein, we provide a brief overview on how to initiate and implement an HDR-IORT program for a selected group of patients with gastrointestinal and pelvic solid tumors using a multidisciplinary approach. Proper administration of HDR-IORT requires institutional support and a joint effort among physics staff, oncologists, surgeons, anesthesiologists, and nurses. In order to determine the true efficacy of IORT for various malignancies, collaboration among institutions with established IORT programs is needed.

Feasibility study of ultrasound imaging for stereotactic body radiation therapy with active breathing coordinator in pancreatic cancer

Abstract Purpose Stereotactic body radiation therapy (SBRT) allows for high radiation doses to be delivered to the pancreatic tumors with limited toxicity. Nevertheless, the respiratory motion of the pancreas introduces major uncertainty during SBRT. Ultrasound imaging is a non‐ionizing, non‐invasive, and real‐time technique for intrafraction monitoring. A configuration is not available to place the ultrasound probe during pancreas SBRT for monitoring. Methods and Materials An arm‐bridge system was designed and built. A CT scan of the bridge‐held ultrasound probe was acquired and fused to ten previously treated pancreatic SBRT patient CTs as virtual simulation CTs. Both step‐and‐shoot intensity‐modulated radiation therapy (IMRT) and volumetric‐modulated arc therapy (VMAT) planning were performed on virtual simulation CT. The accuracy of our tracking algorithm was evaluated by programmed motion phantom with simulated breath‐hold 3D movement. An IRB‐approved volunteer study was also performed to evaluate feasibility of system setup. Three healthy subjects underwent the same patient setup required for pancreas SBRT with active breath control (ABC). 4D ultrasound images were acquired for monitoring. Ten breath‐hold cycles were monitored for both phantom and volunteers. For the phantom study, the target motion tracked by ultrasound was compared with motion tracked by the infrared camera. For the volunteer study, the reproducibility of ABC breath‐hold was assessed. Results The volunteer study results showed that the arm‐bridge system allows placement of an ultrasound probe. The ultrasound monitoring showed less than 2 mm reproducibility of ABC breath‐hold in healthy volunteers. The phantom monitoring accuracy is 0.14 ± 0.08 mm, 0.04 ± 0.1 mm, and 0.25 ± 0.09 mm in three directions. On dosimetry part, 100% of virtual simulation plans passed protocol criteria. Conclusions Our ultrasound system can be potentially used for real‐time monitoring during pancreas SBRT without compromising planning quality. The phantom study showed high monitoring accuracy of the system, and the volunteer study showed feasibility of the clinical workflow.

MO-FG-CAMPUS-JeP3-04: Feasibility Study of Real-Time Ultrasound Monitoring for Abdominal Stereotactic Body Radiation Therapy

PURPOSE Ultrasound is ideal for real-time monitoring in radiotherapy with high soft tissue contrast, non-ionization, portability, and cost effectiveness. Few studies investigated clinical application of real-time ultrasound monitoring for abdominal stereotactic body radiation therapy (SBRT). This study aims to demonstrate the feasibility of real-time monitoring of 3D target motion using 4D ultrasound. METHODS An ultrasound probe holding system was designed to allow clinician to freely move and lock ultrasound probe. For phantom study, an abdominal ultrasound phantom was secured on a 2D programmable respiratory motion stage. One side of the stage was elevated than another side to generate 3D motion. The motion stage made periodic breath-hold movement. Phantom movement tracked by infrared camera was considered as ground truth. For volunteer study three healthy subjects underwent the same setup for abdominal SBRT with active breath control (ABC). 4D ultrasound B-mode images were acquired for both phantom and volunteers for real-time monitoring. 10 breath-hold cycles were monitored for each experiment. For phantom, the target motion tracked by ultrasound was compared with motion tracked by infrared camera. For healthy volunteers, the reproducibility of ABC breath-hold was evaluated. RESULTS Volunteer study showed the ultrasound system fitted well to the clinical SBRT setup. The reproducibility for 10 breath-holds is less than 2 mm in three directions for all three volunteers. For phantom study the motion between inspiration and expiration captured by camera (ground truth) is 2.35±0.02 mm, 1.28±0.04 mm, 8.85±0.03 mm in LR, AP, SI directly, respectively. The motion monitored by ultrasound is 2.21±0.07 mm, 1.32±0.12mm, 9.10±0.08mm, respectively. The motion monitoring error in any direction is less than 0.5 mm. CONCLUSION The volunteer study proved the clinical feasibility of real-time ultrasound monitoring for abdominal SBRT. The phantom and volunteer ABC studies demonstrated sub-millimeter accuracy of 3D motion movement monitoring.

Interventional Radiation Oncology (IRO): Transition of a magnetic resonance simulator to a brachytherapy suite

PURPOSE As a core component of a new gynecologic cancer radiation program, we envisioned, structured, and implemented a novel Interventional Radiation Oncology (IRO) unit and magnetic resonance (MR)-brachytherapy environment in an existing MR simulator. METHODS AND MATERIALS We describe the external and internal processes required over a 6-8 month time frame to develop a clinical and research program for gynecologic brachytherapy and to successfully convert an MR simulator into an IRO unit. RESULTS Support of the institution and department resulted in conversion of an MR simulator to a procedural suite. Development of the MR gynecologic brachytherapy program required novel equipment, staffing, infrastructural development, and cooperative team development with anesthetists, nurses, therapists, physicists, and physicians to ensure a safe and functional environment. Creation of a separate IRO unit permitted a novel billing structure. CONCLUSIONS The creation of an MR-brachytherapy environment in an MR simulator is feasible. Developing infrastructure includes several collaborative elements. Unique to the field of radiation oncology, formalizing the space as an Interventional Radiation Oncology unit permits a sustainable financial structure.

Techniques for Internal Mammary Node Radiation

The clinical decision to include the internal mammary (IM) nodal chain into radiation treatment fields for breast cancer is complex, and the literature surrounding this decision is controversial and even conflicting [1–5]. However, with three high profile papers published in the past year supporting the use of IM radiation even in relatively low-risk women, there will likely be an increasing trend toward IM radiation in the coming years [6]. The primary reasons not to treat these nodes are that it can be technically challenging and may increase exposure to the heart, lung, and contralateral breast. Ultimately, the decision to treat the IM nodes for an individual patient balances the estimated clinical benefit based on the patient’s scenario with the potential additional toxicity that may be conferred by treating this nodal group. This chapter will focus on the various techniques that may be employed to treat the IM nodes, rather than the complex decision-making involved for an individual patient.

TH‐EF‐BRB‐09: Real‐Time Ultrasound Monitoring with Speckle Tracking in Abdominal Stereotactic Body Radiation Therapy

Purpose: Ultrasound is ideal for real-time monitoring with high soft tissue contrast, non-ionization, portability, and cost effectiveness. No studies have investigated clinical feasibility of real-time ultrasound monitoring for abdominal stereotactic body radiation therapy (SBRT) under active breath control (ABC). We are able to monitor target motion using 4D ultrasound and speckle tracking. Methods: An arm-bridge system (ABS) was designed to allow clinician to freely move and lock ultrasound probe. A ceiling mounted infrared camera was calibrated to track probe position using an reflector on the probe. An abdominal ultrasound phantom was secured on a programmable respiratory motion platform to simulate the 20 second expiration and inspiration phases of the ABC with 10 mm inferior translation for 6 cycles. The probe was coupled to the phantom using gel. 4D ultrasound B-mode images were simultaneously acquired at each breath-hold for monitoring. A 3D normalized cross-correlation template matching algorithm was developed to track speckle and feature Point-of-interest (POI) motion at shallow, medium and deep positions in B-mode images. The reproducibility of breath-hold was evaluated by comparing speckle tracking and motion platform position as a function of ROI size. Results: During the repeated respiration movement, the probe position variation was minimal (< 0.5 mm at all time in all directions). For target motion monitoring, ultrasound speckle tracking showed high reproducibility (0.005±0.005 mm AP and 0.01±0.01 mm SI for all ROIs, and 0.03±0.02 mm RL for the shallow and medium ROI). For the deep speckle ROI, the RL error was 0.04±0.04 mm likely due to reduced resolution with depth. Deep ROI showed increased RL tracking accuracy with increased ROI size. Conclusion: Our ABS was able to maintain fixed probe position during the respiration movement with high fidelity. Ultrasound speckle tracking was able to precisely determine the motion over repeated breath-hold for real time monitoring. This work is supported by NIT grant R01CA161613.