• characterisation
• colorectal cancer
• endoscopic device
• flexible endoscopic platform
• minimally invasive surgery
• optimisation
• polyp removal
• soft pneumatic actuator
• surgical robotics
• transanal minimally invasive surgery
• workspace

This study was carried out in response to the significant global impact of diseases that affect the gastrointestinal tract. Colorectal cancer (CRC) remains among the leading causes of cancer-related mortality worldwide, highlighting the critical need for platforms that enable both effective prevention and minimally invasive treatment of such conditions. To fully understand this work, it is essential to consider the morphology of the gastrointestinal tract and the main pathologies that affect it.
Recent studies have emphasised the importance of a detailed anatomical understanding of the large bowel to support the development of more effective medical technologies. Their work involves processing different imaging datasets (including raw and CT medical images) to extract key anatomical metrics such as bowel length and lumen diameter, with distinctions based on gender and posture (supine or prone). These metrics provide biomedical engineers with crucial insights into the physical constraints of the intestine, which must be considered in the design of endoscopic platforms capable of navigating such anatomically complex spaces.
The development of CRC results from alterations in the healthy colonic epithelium. Polyps showing malignant characteristics have the potential to metastasise. There are several established methods for classifying polyps based on morphology, size, and histology. It is generally accepted that polyps greater than 10 mm in size should be removed due to their higher malignancy risk.
The present study focuses on the characterisation and optimisation of the distal section of an innovative flexible endoscopic platform. The platform consists of two modules: a control unit and an actuation unit. The control unit allows the clinician to interface with the actuation unit, managing the various degrees of freedom attributed to flexible surgical instruments, such as those used in traditional endoscopic surgery. These degrees of freedom: translation, rotation, and bending, are enabled by pneumatic soft actuators (SPA). The actuators are designed to be integrated with standard endoscopic instruments, allowing them to perform complex movements within the intestine. Translation determines the level of extension of the actuator relative to the add-on component, which in turn allows the simultaneous use of two instruments through the classic flexible endoscope.
The configuration of the platform, with its soft pneumatic actuators, enables controlled movements that are not achievable with traditional rigid systems. The three degrees of freedom are crucial for navigating the tortuous paths of the intestinal lumen and for achieving effective bimanual manipulation during surgery, and they are particularly beneficial in confined anatomical areas where precise orientation and movement of the instruments are essential to perform complex procedures such as polyp removal or endoscopic resection of malignant tissues, resulting in minimal trauma to surrounding tissues and postoperative complications.
Depending on the staging of the lesion, some surgical approaches are more appropriate than others. The current gold standard for colorectal cancer removal is total mesorectal excision (TME), a radical operation associated with a certain level of morbidity. Given the complex anatomy of the intestinal canal, minimally invasive surgery (MIS) is increasingly being explored to improve surgical outcomes. Novel platforms for advanced MIS, including robotic and flexible endoscopic systems, have been introduced in this work to address the challenges posed by surgery within the intestinal district.
Although there is a wide variety of new flexible devices available for CRC removal, most of them remain in an experimental validation phase or under development. At present, the only commercially available system allows surgical access up to 20 cm from the anal verge, restricting the range of possible interventions.
Workspace reachability was first evaluated, followed by the analysis of forces under different operating conditions of the soft pneumatic actuators. Workspace characterisation was conducted using the Aurora NDI System®, an electromagnetic tracking device, equipped with the Aurora® 6DOF 0.8x9 mm Sensor Tool to track the tip of the soft pneumatic actuator during progressive bending. Following thorough data analysis, the bending angle at the actuator tip was evaluated.
Force characterisation was performed using a dynamometer, evaluating the SPA in three configurations. All tests were performed with different extension lengths (enabled by the translational degree of freedom of the SPA).
After a thorough literature review, specific project constraints were defined, reflecting both clinical requirements and environmental limitations. A simulation was used to recreate the workspace of the SPAs, accounting for degrees of freedom including bending and roll angle around their axes. Some of the add-on’s dimensions were parameterised in the simulation with the aim of achieving the optimal configuration. All considerations were evaluated in the worst case scenario.