Application of robotic technologies in lower gastrointestinal tract endoscopy: A systematic review

Table 3 Summary of the included studies reviewing robotic lower gastrointestinal endoscopy devices with magnetic or hybrid actuation

Ref.	Design and actuation components of evaluated robotic system(s)	Endoscope and/or capsule dimensions	Mode(s) of actuation	Mode(s) of illumination and luminal visualisation	Capabilities evaluated	Degree of robot navigational assistance	Study methodology	Main findings
Valdastri et al[49], 2008 (Italy)	Swallowable wireless capsule with surgical clip, electromagnetic motor, 4 IPMs and a bidirectional communication platform. The EPM on a passive hydraulic arm is controlled manually by the user. A HMI controls clip deployment	Diameter of 12.8 mm and a length of 33.5 mm	Magnetic	No camera in this prototype however 300 mm3 space was left for future integration. Throughout the experiments the capsule was monitored with a flexible endoscope	Therapeutic clip application for bleeding	Direct robot operation	Ex vivo- Porcine colon placed in a model of the abdomen–10 trials. In vivo-1 pig	Ex vivo: Clip release: 100%; Clip release occurred instantly, and moving of the capsule was effective and fast. It took 2-3 min to position the capsule against the mucosa to be clipped. In vivo: Good locomotion and positioning with the EPM. The clip was released successfully onto the desired target. The clip remained in situ. The amount of tissue grasped was satisfactory
Ciuti et al[50], 2010 (Italy)	Magnetic wireless capsule with inertial and vision sensors and a set of IPM; External robotic arm with EPM and human machine interface. The working distance is 150 mm. The HMI is used to control the robotic arm and receives input from the capsule	Capsule: 40 mm in length, 18 mm in diameter	Magnetic	CMOS camera and 4 white LEDs	Visualisation, locomotion and learning curve	Intelligent teleoperation	Ex vivo: 500 mm porcine colon in human phantom model–40 trials (some insufflated and collapsed colons)	Insufflated colon: 100% of success rate in traversing the entire colon. Short learning curve (descriptive analysis) to drive the robotic arm. The average time required to traverse the colon was approximately 10 min. Collapsed colon: Capsule was able to travel only really short distances and manual assistance was required
Ciuti et al[51], 2009 (Italy)	Wired capsule with 3 IPMs and vision module; EPM either controlled manually or robotically via a robotic arm controlled by a HMI and controller. The working distance is 150 mm	14 mm in diameter and 38 mm in length	Magnetic	CMOS camera with illumination system	Robotic versus manual steering	Direct or Intelligent teleoperation	Ex vivo: 480 mm porcine colon in human phantom model–10 trials each for robot and manual arm steering. In vivo: 2 Pigs–5 trials each for robot and manual arm steering	Ex vivo: Robot versus manual steering: The mean completion time: 423 s vs 201 s (P < 0.01). The mean percentage of ‘4 mm white spherical targets’ reached: 87% versus 37% (P < 0.01). In vivo: Manual steering was usually faster, whereas manoeuvrability was better with robotic movement of the EPM (Descriptive analysis)
Carpi et al[52], 2011 (Italy/United States)	PillCam (Given Imaging Ltd, Israel) capsule covered in a magnetic shell; Two EPMs, a magnetic navigation system (Niobe, Stereotaxis, Inc, United States), a remote computer work-station and mouse. Fluoroscopic images were continuously acquired by means of a digital scanner to provide visual feedback regarding capsule manoeuvres	13 mm in diameter and length	Magnetic	Not described	Steering and localisation capability	Intelligent teleoperation	In vivo: Pig (Number of pigs and trials not described)	The capsule was freely moved within the colon. No complications
Gu et al[53], 2017 (China)	The MCCE system (Chongqing Jinshan Science & Technology Group Co, Ltd): Ingestible colon capsule with IPM and battery, an external magnetic manipulator with an EPM, and an image transmission system	Capsule measures 27.9 mm in length by 13.0 mm in diameter	Magnetic	Not described	Manoeuvrability, visualisation, diagnosis and safety	Direct robot operation	In vivo: n = 52 Human, CRC screening volunteers. Capsule movement was visualised via colonoscopy 5 h after ingestion	Average CIT: 3.63 h. Maneuverability of the capsule was good (94.3%) or moderate (5.77%). MCCE provided good-quality pictures and identified 6 positive findings (polyps, diverticulum) which were confirmed by colonoscopy. 78% reached the rectosigmoid colon in 25 min. All 57 volunteers were able to swallow the capsule and excreted the capsule within 2 d. Complications: 7 mild adverse events (abdominal discomfort, nausea, and vomiting) lasting 24 h. No complications at one week follow up
Valdastri et al[13], 2012 (Italy)	MAC consists of capsule-like frontal unit and a compliant multi-lumen tether. The frontal unit contains a vision module, an IPM, a magnetic field sensor, and two channels, one for lens cleaning and the other for insufflation/suction/irrigation or instrument passage. The IPM is controlled by an EPM mounted on a robotic platform. A control device allows the user to directly control the position of the EPM. The working distance is 150 mm. The tether connects to an external control box	Capsule: 11 mm diameter, 26 mm in length. Tether: 5.4 mm diameter, 2 m length	Magnetic	CCD camera with 120 degree field of view and 4 white LEDs	Diagnostic and treatment ability, safety, usability	Intelligent teleoperation	Ex vivo: 850 mm porcine colon in human phantom model–12 trials. In vivo: 2 Pigs–3 trials each	Ex vivo: Mean percentage of 5 mm coloured beads (polyps) detected was 85%. 100% successful removal (polypectomy loop) of identified beads. Mean completion time (inspection and bead removal) was 678 s. Mean bead removal time was 18 s. Good manoeuvrability, low friction from the tether on the colon wall and reliable feedback from the vision module. In vivo: No mucosal damage or perforation. Able to navigate around bends and folds, retroflexion of the camera and successful operation of the tools (loop, forceps, retrieval basket, grasper) without loss of magnetic link
Arezzo et al[54], 2013 (Italy)	Robotic arm with EPM controlled by HMI and controller; Wired capsule with 3 IPMs, camera, LEDs and magnetic sensor. The working distance is 150mm. The wired sheath allows transmission from the vision module and electric energy	Capsule: 13.5 mm in diameter and 29.5 mm in length. Wired sheath: 2 mm in diameter	Magnetic	CCD camera with 120 degree view and 6 white LEDs	Visualisation and diagnostic ability compared to colonoscopy	Intelligent teleoperation	Ex vivo: 850 mm porcine colon in human phantom model–22 trials each for capsule and colonoscope	Robot vs colonoscopy: CIR: 100% for both. Pin detection rate: 80.9% vs 85.8%. Procedure completion time (visualisation and diagnosis): 556 s vs 194 s (P = 0.0001). No difference in intuitiveness score
Slawinski et al[55], 2018 (United States/United Kingdom)	MFE with IPM, camera, illumination module, working channel for instruments, channel for irrigation and insufflation, EPM on robotic arm and HMI. Additional sensing, retroflexion and software control systems	Tip: 20.6 mm in diameter and 18.1 mm in length. Body: 6.5 mm in diameter	Magnetic	Camera and illumination module	Retroflexion ability	Intelligent teleoperation with task autonomy	In vivo: 1 Pig–30 trials	100% successful retroflexion manoeuvres with a mean time of 11.3 s. No acute tissue trauma or perforation
Martin et al[14], 2020 (United Kingdom)	MFE with an IPM, camera, an insufflation channel, irrigation channel, working channel for instruments and localisation circuit; A robotic arm with EPM; Robot operating system and joystick	Capsule: 20.6 mm in diameter and 18.1 mm in length. Tether: 6.5 mm in diameter	Magnetic	Camera and LED	Comparison of different degrees of autonomy for locomotion and novice usability	Direct robot or intelligent teleoperation or semi-autonomous	In vivo: 2 Pigs–3 trials for each MFE control and colonoscopy in the first pig and 4 trials for each in the second pig	First porcine model–colon distance of 45 cm: Task completion times for direct robot operation, teleoperation, semi-autonomous operation and conventional colonoscopy were 9 min 4 s, 2 min 20 s and 3 min 9 s and 1 min 39 s, respectively. Second porcine model-colon distance of 85 cm: Task completion times for, teleoperation, semi-autonomous operation and conventional colonoscopy were 8 min 6 s, 9 min 39 s and 3 min 29 s, respectively. It was not possible to reach the marker with direct robotic operation. Intelligent and semi-autonomous had NASA task force mean Index ratings lower/less demanding than colonoscopy or direct robot operation
Verra et al[57], 2020 (Italy)	Endoo system: An Endoo capsule with a IPM, soft tether connection with 4 working channels for suction, insufflation, irrigation and instruments; An external robot with EPM, force-torque sensor and movable platform, localisation system and medical workstation with a joystick complete the system. The robot with EPM is controlled via the workstation but can also be steered manually. The localisation system provides information on the capsule position and orientation	Tether: 160 cm long	Magnetic	Two CMOS cameras with 170 degree field of view, 4 white LEDs and 4 green/blue UV-LEDs	Visualisation, locomotion, diagnosis and safety	Semi-autonomous	Ex vivo: 100-120 mm porcine colon in human phantom model	Ex vivo Endoo alone: 100% success rate in operating channel (use of polypectomy snares, biopsy forceps and needles). 100% success rate for target approach tests (using these instruments to target a polyp). Ex vivo Endoo (21 trials) vs colonoscopy (13 trials): Completion rate: 67% vs 100%. Interaction forces: 1.17 N vs 4.12 N. Polyp detection rate: 87% vs 91% (P = 0.16). Mean CIT: 9.5 min vs 3.5 min. The magnetic link was lost an average of 1.28 times per complete procedure, but it was restored in 100% of cases
Simi et al[58], 2010 (Italy)	Wireless endocapsule with legged mechanism (3 legs), DC motor, battery, small IPMs which interacts with an EPM. LabVIEW HMI is present and is also compatible with voice commands	14 mm in diameter, 44 mm in length.	Hybrid- Electromechanical and Magnetic	No camera in this prototype however 450 mm3 space was left for future integration. Throughout the experiments the capsule was monitored with a gastroscope	Locomotion and lumen dilatation	Semiautonomous	Ex vivo: 20 cm porcine colon–10 trials. In vivo: 4 pigs–10 trials. Capsule was placed 40 cm from the anus and expected to travel towards the anus	Ex vivo: Ability to travel 20 cm in 10 min: 70%. Average time to traverse 20 cm and number of leg activations: 4 min and 5 mechanism activations. Average speed: 5 cm/min. In vivo: Ability to travel 40 cm in 20 min: 60%. Average time to traverse 40 cm and number of leg activations: 5 min and 5 activations. Average speed: 8 cm/min
Nouda et al[59], 2018 (Japan)	Self-propelling capsule endoscope (SPCE) consisting of a silicon resin fin with micro-magnet connected to the PillCam SB2 capsule; External magnetic field generating controller (Minimermaid System), human interface with joystick	45 mm in length and 11 mm in diameter	Hybrid- Mechanical and Magnetic	Camera with 156 degree field of view	Locomotion and safety	Semi-autonomous	In vivo: 1 Human	The SPCE could swim smoothly in forward and backward directions but had difficulty bypassing bends. No acute complications

IPM: Internal permanent magnet; EPM: External permanent magnet; HMI: Human machine interface; LEDs: Light emitting diodes; CMOS: Complementary metal-oxide-semiconductor; CIT: Caecal intubation time; CIR: Caecal intubation rate; CCD: Charged coupled device; MCCE: Magnetic controlled capsule endoscopy; MFE: Magnetic flexible endoscope.