Esther Rozeboom

T2 weighted signal intensity evolution may predict pathological complete response after treatment for rectal cancer

AbstractObjectivesTo determine the diagnostic value of T2-weighted signal intensity evolution in the tumour for detection of complete response to neoadjuvant chemoradiotherapy in patients with rectal cancer.MethodsThirty-nine patients diagnosed with locally advanced adenocarcinoma and treated with chemoradiotherapy (CRT), followed by surgery, underwent magnetic resonance imaging (MRI) before and after CRT on 1.5-T MRI using T2-weighted fast spin-echo (FSE) imaging. The relative T2-weighted signal intensity (rT2wSI) distribution in the tumour and post-CRT residual tissue was characterised by means of the descriptive statistical parameters, such as the mean, 95th percentile and standard deviation (SD). Receiver operating characteristic curves were used to determine the diagnostic potential of the CRT-induced alterations (Δ) in rT2wSI descriptives. The tumour regression grade (TRG) served as a histopathological reference standard.ResultsCRT induced a significant decrease of approximately 50% in all rT2wSI descriptives in complete responders (TRG1). This drop was significantly larger than for incomplete response groups (TRG2–TRG4). The ΔrT2wSI descriptives produced a high diagnostic performance for identification of complete responders, e.g. Δ95th percentile, ΔSD and Δmean resulted in accuracy of 92%, 90% and 82%, respectively.ConclusionsQuantitative assessment of the CRT-induced changes in the tumour T2-weighted signal intensity provides high diagnostic performance for selection of complete responders.Key Points• T2 weighted MRI helps predict response after chemoradiotherapy for rectal cancer. • Residual tumour and chemoradiotherapy-induced fibrosis have different T2 relaxation properties. • T2-weighted signal intensity evolution is a promising non-invasive marker of therapeutic response. • A pathologically complete response is associated with the largest signal intensity drop.

Intuitive user interfaces increase efficiency in endoscope tip control

BackgroundFlexible endoscopes are increasingly used to perform advanced intraluminal and transluminal interventions. These complex interventions demand accurate and efficient control, however, current endoscopes lack intuitiveness and ergonomic control of the endoscope tip. Alternative handheld controllers can improve intuitiveness and ergonomics, though previous studies are inconclusive concerning their effect on the efficiency of endoscope manipulation. The aim of this study is to determine the efficiency of a robotic system with intuitive user interface in controlling the tip of the flexible endoscope.MethodsWe compared the efficiency of time and tip trajectory when steering the endoscope tip using the conventional steering wheels and a robotic platform with three different user interfaces: a touchpad in combination with a position control algorithm, a joystick combined with linear rate control, and a joystick combined with non-linear rate control. Fourteen participants, without a medical background, used all four interfaces. They performed both large navigational and fine targeting tasks in a simulated environment which allowed objective cross-subject comparison. Afterward, the participants were asked to select their preferred steering method.ResultsParticipants were significantly faster in steering the endoscope tip when using robotic steering compared to using the conventional steering method. Between the robotic interfaces, using the touchpad was significantly faster compared to the joystick with linear rate control. Use of the joystick with non-linear rate control led to a shorter tip trajectory compared to the touchpad. The majority of participants preferred the joystick with non-linear rate control over the other steering methods.ConclusionsThis work shows that intuitive user interfaces can improve the efficiency of endoscope tip steering.

Colonoscopy with robotic steering and automated lumen centralization: a feasibility study in a colon model.

BACKGROUND AND STUDY AIMS We introduced a new platform for performing colonoscopy with robotic steering and automated lumen centralization (RS-ALC) and evaluated its technical feasibility. PARTICIPANTS AND METHODS Expert endoscopists (n = 8) and endoscopy-naive novices (n = 10) used conventional steering and RS-ALC to perform colonoscopy in a validated colon model with simulated polyps (n = 21). The participants were randomized to which modality they were to use first. End points were the cecal intubation time, number of detected polyps, and subjective evaluation of the platform. RESULTS Novices were able to intubate the cecum faster with RS-ALC (median 8 minutes [min] 56 seconds [s], interquartile range [IQR] 6  min 46  s - 16  min 34  s vs. median 11  min 47  s, IQR 8  min 19  s - 15  min 33  s, P = 0.65), whereas experts were faster with conventional steering (median 2  min 9  s, IQR 1  min 13 s - 7  min 28  s vs. median 13  min 1  s, IQR 5  min 9 s - 16  min 54  s, P = 0.12). Novices detected more polyps with RS-ALC (median 88.1 %, IQR 79.8 % - 95.2 % vs. median 78.6 %, IQR 75.0 % - 91.7 %, P = 0.17), whereas experts detected more polyps with conventional steering (median 80.9 %, IQR 76.2 % - 85.7 % vs. median 69.0 %, IQR 61.0 % - 75.0 %, P = 0.03). Novices were more positive than experts about the new platform (P = 0.02), noting an easier and faster introduction of the colonoscope with RS-ALC than with conventional steering. CONCLUSIONS Colonoscopy with RS-ALC is technically feasible and appears to be easier and more intuitive than conventional steering for endoscopy-naive novices.

Robotic-assisted flexible colonoscopy: preliminary safety and efficiency in humans.

BACKGROUND AND AIMS The flexible endoscope is used as a platform for minimally invasive interventions. However, control of the conventional endoscope and multiple instruments is difficult. Robotic assistance could provide a solution and better control for a single operator. A novel platform should also enable interventions in areas that are currently difficult to reach. This study evaluates the safety and efficacy of a robotic platform that guides a conventional endoscope through the large bowel. METHODS Adult patients scheduled for routine diagnostic colonoscopy were included in this feasibility study. The endoscope was introduced using a robotic add-on to provide tip bending and air/water actuation. The endoscopist directly controlled the endoscope shaft. Upon cecal intubation, the add-on was detached and the procedure continued using conventional control. Primary evaluation parameters were the number of serious adverse events and the percentage of successful cecal intubations. RESULTS The procedure was performed on 22 consecutive patients who all gave informed consent. There were no serious adverse events. Cecal intubation was successful in 15 patients (68%) using the robotic add-on. Six cases were completed after conversion to conventional control: 3 cases were converted to pass sharp angulation in the flexures and 3 cases were converted after technical difficulties. One case was not successful with either technique because of severe diverticulosis. CONCLUSIONS The robotic add-on steering module allows safe endoscope intubation to reach intervention sites throughout the large bowel. The next step is to clinically evaluate complementary instrument and shaft-guiding modules in therapeutic procedures.

Evaluation of the tip-bending response in clinically used endoscopes

Background and study aims: Endoscopic interventions require accurate and precise control of the endoscope tip. The endoscope tip response depends on a cable pulling system, which is known to deliver a significantly nonlinear response that eventually reduces control. It is unknown whether the current technique of endoscope tip control is adequate for a future of high precision procedures, steerable accessories, and add-on robotics. The aim of this study was to determine the status of the tip response of endoscopes used in clinical practice. Materials and methods: We evaluated 20 flexible colonoscopes and five gastroscopes, used in the endoscopy departments of a Dutch university hospital and two Dutch teaching hospitals, in a bench top setup. First, maximal tip bending was determined manually. Next, the endoscope navigation wheels were rotated individually in a motor setup. Tip angulation was recorded with a USB camera. Cable slackness was derived from the resulting hysteresis plot. Results: Only two of the 20 colonoscopes (10 %) and none of the five gastroscopes reached the maximal tip angulation specified by the manufacturer. Four colonoscopes (20 %) and none of the gastroscopes demonstrated the recommended cable tension. Eight colonoscopes (40 %) had undergone a maintenance check 1 month before the measurements were made. The tip responses of these eight colonoscopies did not differ significantly from the tip responses of the other colonoscopes. Conclusion: This study suggests that the majority of clinically used endoscopes are not optimally tuned to reach maximal bending angles and demonstrate adequate tip responses. We suggest a brief check before procedures to predict difficulties with bending angles and tip responses.

Single-handed controller reduces the workload of flexible endoscopy

AbstractThe control of the conventional flexible endoscope is non-ergonomic and non-intuitive. A novel single-handed interface could reduce the experienced workload, without reducing current efficiency or effectiveness of endoscope manipulation. The aim of this study is to evaluate the workload, efficiency and effectiveness of a single-handed controller in colonoscopy, in comparison to a bimanual controller and the conventional angulation wheels. Twenty-one inexperienced students performed colonoscopies on a computer simulator using either the single-handed controller with a joystick interface, a bimanual controller with a joystick interface or the conventional angulation wheels. Participants performed three sessions of colonoscopies. After each session, the experienced workload was evaluated using a seven-component absolute scoring scale. Efficiency of the procedure was evaluated by the cecal intubation time and total-used scope length. Effectiveness was evaluated by the percentage of bowel wall visualization. The total workload of the single-handed controller was lower compared to the conventional angulation wheels for all three sessions. The total workload of the bimanual controller was lower compared to the conventional angulation wheels in the second and third session and also lower compared to the single-handed controller in the third session. There was no significant difference between the three control interfaces in time efficiency, used scope length or visualization performance. Single-handed and bimanual controllers with a joystick interface are a feasible approach to reduce the workload of colonoscopy without reducing efficiency or effectiveness of endoscope manipulation.

Robotic steering of flexible endoscopes

Flexible endoscopes were originally designed for non-invasive inspection of body cavities and hollow organs. Today, they are also used for complex minimal invasive interventions. Control of the endoscope is difficult and complexity rises with interventional procedures. Endoscopists suffer from long learning curves, ergonomic complaints and multi-person control is needed to steer endoscope and instrument(s). Robotics have the potential to overcome these problems. The combined forces of a technical university, mechatronic company and physicians from multiple hospitals led to the design of an add-on robotic platform. The platform aims to improve usability of conventional flexible endoscopes for complex interventions. These interventions require accurate and precise tip steering. This thesis describes the design and clinical evaluation of the platforms tip steering module. An optimal user interface and control algorithm was sought to improve usability of the endoscope in clinical practise. The results showed non-inferiority of the platform in simulated diagnostic procedures. A patient study showed that the add-on platform allows a safe and feasible introduction of an endoscope through the bowel. The robotic platform proposed in this thesis is based on pairing with conventional endoscopes. Consequently, performance results of the add-on platform also depend on the tip bending response of the used endoscopes. An evaluation of the tip bending response of clinically used endoscopes suggests that the vast majority of endoscopes are not optimally tuned to reach maximal bending angles and adequate tip response. Innovations that close the control loop and hysteresis control methods are expected to further improve precise and efficient endoscope tip steering.