The Feasibility of Haar Feature-Based Endoscopic Ultrasound Probe Tracking for Implanting Hydrogel Spacer in Radiation Therapy for Pancreatic Cancer

Abstract

PurposeWe proposed a Haar feature-based method for tracking endoscopic ultrasound (EUS) probe in diagnostic computed tomography (CT) and Magnetic Resonance Imaging (MRI) scans for guiding hydrogel injection without external tracking hardware. This study aimed to assess the feasibility of implementing our method with phantom and patient images.Materials and MethodsOur methods included the pre-simulation section and Haar features extraction steps. Firstly, the simulated EUS set was generated based on anatomic information of interpolated CT/MRI images. Secondly, the efficient Haar features were extracted from simulated EUS images to create a Haar feature dictionary. The relative EUS probe position was estimated by searching the best matched Haar feature vector of the dictionary with Haar feature vector of target EUS images. The utilization of this method was validated using EUS phantom and patient CT/MRI images.ResultsIn the phantom experiment, we showed that our Haar feature-based EUS probe tracking method can find the best matched simulated EUS image from a simulated EUS dictionary which includes 123 simulated images. The errors of all four target points between the real EUS image and the best matched EUS images were within 1 mm. In the patient CT/MRI scans, the best matched simulated EUS image was selected by our method accurately, thereby confirming the probe location. However, when applying our method in MRI images, our method is not always robust due to the low image resolution.ConclusionsOur Haar feature-based method is capable to find the best matched simulated EUS image from the dictionary. We demonstrated the feasibility of our method for tracking EUS probe without external tracking hardware, thereby guiding the hydrogel injection between the head of the pancreas and duodenum.

Demonstrating the benefits of corrective intraoperative feedback in improving the quality of duodenal hydrogel spacer placement

“…However, the main challenge is the registration of 2D ultrasound images to the CT and measuring the amount of separation, which is the aim of our current and future studies. [46][47][48] We are aware that our study has a few limitations. First, due to the novelty of the duodenal spacer, the number of cases is very limited and has not been widely used in the clinic.…”

Finite Element-Based Personalized Simulation of Duodenal Hydrogel Spacer: Spacer Location Dependent Duodenal Sparing and a Decision Support System for Spacer-Enabled Pancreatic Cancer Radiation Therapy

“…We found that spacer benefit for a high-dose volume is highly dependent on the patient’s anatomy and spacer location. Future work focuses on (1) improving the software and reliability of the model by incorporating a larger patient cohort, (2) adding more features to the DSS such as prediction of toxicity and cost-effectiveness, and (3) proposing a new workflow featuring preoperative simulation and intraoperative guidance to personalize and optimize the duodenal spacer procedure based on our studies on wavelet-based image guidance ( 25 , 48 ).…”

Laparoscopic spacer placement for bulky lymph node metastasis of cervical cancer: A case report

“…As with other approaches to holding the lesion away from the surrounding organs, there is the surgical method to insert a tool called a “spacer.” The materials of the spacer vary depending on the targets. Blood patch, human collagen, acellular human dermis ( Ismael et al, 2016 , Dalwadi et al, 2019 ), hyaluronic acid, and polyethylene-glycol hydrogel have been used, mainly via injection for prostate cancer ( Tang et al, 2018 , Ismael et al, 2016 , Feng et al, 2021 ). Since the first report of the clinical use of spacers in 1984 ( Dürig et al, 1984 ), several placement methods and materials of spacers have been reported in head and neck cancer ( Shibuya, 2009 ) and abdominal pelvic tumors ( Sezeur et al, 1999 ), liver ( Ismael et al, 2016 ), retroperitoneal tumor, and pancreatic cancer ( Feng et al, 2021 ), and researched very intensively in prostate cancer ( Tang et al, 2018 ).…”

“…Blood patch, human collagen, acellular human dermis ( Ismael et al, 2016 , Dalwadi et al, 2019 ), hyaluronic acid, and polyethylene-glycol hydrogel have been used, mainly via injection for prostate cancer ( Tang et al, 2018 , Ismael et al, 2016 , Feng et al, 2021 ). Since the first report of the clinical use of spacers in 1984 ( Dürig et al, 1984 ), several placement methods and materials of spacers have been reported in head and neck cancer ( Shibuya, 2009 ) and abdominal pelvic tumors ( Sezeur et al, 1999 ), liver ( Ismael et al, 2016 ), retroperitoneal tumor, and pancreatic cancer ( Feng et al, 2021 ), and researched very intensively in prostate cancer ( Tang et al, 2018 ). Recently, a meta -analysis confirmed the benefit of percutaneous SpaceOAR TM Hydrogel injection for prostate cancer temporarily distances the rectum from the prostate.…”

“…On the other hand, other materials used as spacers have been only sporadically reported, including allografts, tissue expanders, silicone balloons, and Gore-Tex sheets for pediatric, gynecologic, and other abdominal and retroperitoneal tumors ( Tang et al, 2018 , Sezeur et al, 1999 , Lee et al, 2021 ). The method of inserting these materials varies from endoscopic injections ( Feng et al, 2021 ) to surgical procedures such as open or minimally invasive ( Tang et al, 2018 ). Spacer usage for malignancies except prostate cancer requiring multidisciplinary management, including radiotherapy beyond standard treatment, has not been standardized.…”