Operating Room Performance Optimization Metrics: a Systematic Review.

Literature proposes numerous initiatives for optimization of the Operating Room (OR). Despite multiple suggested strategies for the optimization of workflow on the OR, its patients and (medical) staff, no uniform description of 'optimization' has been adopted. This makes it difficult to evaluate the proposed optimization strategies. In particular, the metrics used to quantify OR performance are diverse so that assessing the impact of suggested approaches is complex or even impossible. To secure a higher implementation success rate of optimisation strategies in practice we believe OR optimisation and its quantification should be further investigated. We aim to provide an inventory of the metrics and methods used to optimise the OR by the means of a structured literature study. We observe that several aspects of OR performance are unaddressed in literature, and no studies account for possible interactions between metrics of quality and efficiency. We conclude that a systems approach is needed to align metrics across different elements of OR performance, and that the wellbeing of healthcare professionals is underrepresented in current optimisation approaches.

Deep learning for surgical phase recognition using endoscopic videos.

BACKGROUND: Operating room planning is a complex task as pre-operative estimations of procedure duration have a limited accuracy. This is due to large variations in the course of procedures. Therefore, information about the progress of procedures is essential to adapt the daily operating room schedule accordingly. This information should ideally be objective, automatically retrievable and in real-time. Recordings made during endoscopic surgeries are a potential source of progress information. A trained observer is able to recognize the ongoing surgical phase from watching these videos. The introduction of deep learning techniques brought up opportunities to automatically retrieve information from surgical videos. The aim of this study was to apply state-of-the art deep learning techniques on a new set of endoscopic videos to automatically recognize the progress of a procedure, and to assess the feasibility of the approach in terms of performance, scalability and practical considerations. METHODS: A dataset of 33 laparoscopic cholecystectomies (LC) and 35 total laparoscopic hysterectomies (TLH) was used. The surgical tools that were used and the ongoing surgical phases were annotated in the recordings. Neural networks were trained on a subset of annotated videos. The automatic recognition of surgical tools and phases was then assessed on another subset. The scalability of the networks was tested and practical considerations were kept up. RESULTS: The performance of the surgical tools and phase recognition reached an average precision and recall between 0.77 and 0.89. The scalability tests showed diverging results. Legal considerations had to be taken into account and a considerable amount of time was needed to annotate the datasets. CONCLUSION: This study shows the potential of deep learning to automatically recognize information contained in surgical videos. This study also provides insights in the applicability of such a technique to support operating room planning.

Electrosurgery: short-circuit between education and practice.

Introduction: Electrosurgery is used in 80% of surgical procedures. The technique allows surgeons to skilfully dissect tissues and achieve haemostasis. Since improper use of electrosurgery can lead to serious adverse events, training is required to potentially reduce the number and severity of these events. In this study we evaluate education and training in electrosurgery for surgical residents. Material and methods: Residents from six surgical subspecialties in the Netherlands were invited to anonymously complete a digital questionnaire about training, supervision and adverse events regarding electrosurgery. Results: Of the 197 respondents, 69% had received some form of training; mostly a single theoretical lecture. The feeling of competence in theory and practical skills was positively rated by 39% and 71%, respectively. Moreover, 35% judged the theoretical knowledge of their supervisors as insufficient and 65% changed their electrosurgical application technique to the preference of the supervisor. 30% of the residents had encountered a serious adverse event (e.g., burn wounds) related to the application of electrosurgery. Conclusions: The training of residents in theoretical aspects of electrosurgery is limited. Residents are not satisfied with the acquired theoretical knowledge of themselves and of their supervisors. Since adverse events related to electrosurgery occur frequently, more extensive education for both residents and their supervisors is needed to enhance patient safety.

Measuring surgical safety during minimally invasive surgical procedures: a validation study.

BACKGROUND: During the implementation of new interventions (i.e., surgical devices and technologies) in the operating room, surgical safety might be compromised. Current safety measures are insufficient in detecting safety hazards during this process. The aim of the study was to observe whether surgical teams are capable of measuring surgical safety, especially with regard to the introduction of new interventions. METHODS: A Surgical Safety Questionnaire was developed that had to be filled out directly postoperative by three surgical team members. A potential safety concern was defined as at least one answer between (strongly) disagree and indifferent. The validity of the questionnaire was assessed by comparison with the results from video analysis. Two different observers annotated the presence and effect of surgical flow disturbances during 40 laparoscopic hysterectomies performed between November 2010 and April 2012. RESULTS: The surgeon reported a potential safety concern in 16% (85/520 questions). With respect to the scrub nurse and anesthesiologist, this was both 9% (46/520). With respect to the preparation, functioning, and ease of use of the devices in 37.5-47.5% (15-19/40 procedures) a potential safety concern was reported by one or more team members. During procedures after which a potential safety concern was reported, surgical flow disturbances lasted a higher percentage of the procedure duration [9.3 ± 6.2 vs. 2.9 ± 3.7% (mean ± SD), p < .001]. After procedures during which a new instrument or device was used, more potential safety concerns were reported (51.2 vs. 23.1%, p < .001). CONCLUSIONS: Potential safety concerns were especially reported during procedures in which a relatively high percentage of the duration consisted of surgical flow disturbances and during procedures in which a new instrument or device was used. The Surgical Safety Questionnaire can act as a validated tool to evaluate and maintain surgical safety during minimally invasive procedures, especially during the introduction of a new intervention.

Endpoint Accuracy in Manual Control of a Steerable Needle.

PURPOSE: To study the ability of a human operator to manually correct for errors in the needle insertion path without partial withdrawal of the needle by means of an active, tip-articulated steerable needle. MATERIALS AND METHODS: The needle is composed of a 1.32-mm outer-diameter cannula, with a flexure joint near the tip, and a retractable stylet. The bending stiffness of the needle resembles that of a 20-gauge hypodermic needle. The needle functionality was evaluated in manual insertions by steering to predefined targets and a lateral displacement of 20 mm from the straight insertion line. Steering tasks were conducted in 5 directions and 2 tissue simulants under image guidance from a camera. The repeatability in instrument actuations was assessed during 100 mm deep automated insertions with a linear motor. In addition to tip position, tip angles were tracked during the insertions. RESULTS: The targeting error (mean absolute error ± standard deviation) during manual steering to 5 different targets in stiff tissue was 0.5 mm ± 1.1. This variability in manual tip placement (1.1 mm) was less than the variability among automated insertions (1.4 mm) in the same tissue type. An increased tissue stiffness resulted in an increased lateral tip displacement. The tip angle was directly controlled by the user interface, and remained unaffected by the tissue stiffness. CONCLUSIONS: This study demonstrates the ability to manually steer needles to predefined target locations under image guidance.

Surgical flow disturbances in dedicated minimally invasive surgery suites: an observational study to assess its supposed superiority over conventional suites.

BACKGROUND: Minimally invasive surgery (MIS) is frequently compromised by surgical flow disturbances due to technology- and equipment-related failures. Compared with MIS in a conventional cart-based OR, performing MIS in a dedicated integrated operating room (OR) is supposed to be beneficial to patient safety. The aim of this study was to compare a conventional OR with an integrated OR with regard to the incidence and effect of equipment-related surgical flow disturbances during an advanced laparoscopic gynecological procedure [laparoscopic hysterectomy (LH)]. METHODS: Using video recording, 40 LHs performed between November 2010 and April 2012 (20 in a conventional cart-based OR and 20 in an integrated OR) were analyzed by two different observers. Outcome measures were the number, duration and effect (on a seven-point ordinal scale) of the surgical flow disturbances (e.g., malfunctioning, intraoperative repositioning, setup device). RESULTS: A total of 103 h and 45 min was observed. The interobserver agreement was high (kappa .85, p < .001). Procedure time was not significantly different (NS) [conventional OR vs. integrated OR, minutes ± standard deviation (SD), mean 161 ± 27 vs. 150 ± 34]. A total of 1651 surgical flow disturbances were observed (mean ± SD per procedure 40.8 ± 19.4 vs. 41.8 ± 15.9, NS). The mean number of surgical flow disturbances per procedure with regard to equipment was 6.3 ± 3.7 versus 8.5 ± 4.0, NS. No clinically relevant differences in the mean effect of these disturbances on the surgical flow between the two OR setups were observed. CONCLUSIONS: Performing LH in an integrated OR did not reduce the number of surgical flow disturbances nor the effect of these disturbances. Furthermore, in the integrated OR, repositioning of the monitors was a frequent and time-consuming source of disturbance. In order to maintain the high standard of surgical safety, the entire surgical team has to be aware that by performing surgery in an integrated OR different potential source for disruption arise.

The Art of Electrosurgery: Trainees and Experts.

The benefits of electrosurgery have been acknowledged since the early 1920s, and nowadays more than 80% of surgical procedures involve devices that apply energy to tissues. Despite its widespread use, it is currently unknown how the operator's choices with regard to instrument selection and application technique are related to complications. As such, the manner in which electrosurgery is applied can have a serious influence on the outcome of the procedure and the well-being of patients. The aim of this study is to investigate the variety of differences in usage of electrosurgical devices. Our approach is to measure these parameters to provide insight into application techniques. A sensor was developed that records the magnitude of electric current delivered to an electrosurgical device at a frequency of 10 Hz. The sensor is able to detect device activation times and a reliable estimate of the power-level settings. Data were recorded for 91 laparoscopic cholecystectomies performed by different surgeons and residents. Results of the current measurement data show differences in the way electrosurgery is applied by surgeons and residents during a laparoscopic cholecystectomy. Variations are seen in the number of activations, the activation time, and the approach for removal of the gallbladder. Analysis showed that experienced surgeons have a longer activation time than residents (3.01 vs 1.41 seconds, P < .001) and a lower number of activations (102 vs 123). This method offers the opportunity to relate application techniques to clinical outcome and to provide input for the development of a best practice model.

Where are my instruments? Hazards in delivery of surgical instruments.

BACKGROUND: Unavailability of instruments is recognised to cause delays and stress in the operating room, which can lead to additional risks for the patients. The aim was to provide an overview of the hazards in the entire delivery process of surgical instruments and to provide insight into how Information Technology (IT) could support this process in terms of information availability and exchange. METHODS: The process of delivery was described according to the Healthcare Failure Mode and Effects Analysis methodology for two hospitals. The different means of information exchange and availability were listed. Then, hazards were identified and further analysed for each step of the process. RESULTS: For the first hospital, 172 hazards were identified, and 23 of hazards were classified as high risk. Only one hazard was considered as 'controlled' (when actions were taken to remove the hazard later in the process). Twenty-two hazards were 'tolerated' (when no actions were taken, and it was therefore accepted that adverse events may occur). For the second hospital, 158 hazards were identified, and 49 of hazards were classified as high risk. Eight hazards were 'controlled' and 41 were 'tolerated'. The means for information exchange and information systems were numerous for both cases, while there was not one system that provided an overview of all relevant information. CONCLUSIONS: The majority of the high-risk hazards are expected to be controlled by the use of IT support. Centralised information and information availability for different parties reduce risks related to unavailability of instruments in the operating room.

Fiber-Optic Fabry-Pérot Interferometers for Axial Force Sensing on the Tip of a Needle.

A range of complex percutaneous procedures, such as biopsy or regional anesthesia, rely heavily on accurate needle insertion. Small variations in the mechanical properties of the pierced tissue can however cause deviations from the projected needle path and can thus result in inaccurate placement of the needle. Navigation of a rigid needle towards the target tissue is traditionally based on the surgeons capacity to interpret small variations in the needle insertion force. A more accurate measurement of these small force variations enables improvement in needle targeting, can potentially aid in enhancing force feedback in robotic needle placement and can provide valuable information on tissue-tool interaction. In this study we investigated several concepts for the design of a force sensor based on a fiber-optic Fabry-Pérot interferometer to measure needle-tissue interaction forces on the tip of a 18 G needle, where special attention was given to concepts for a sensor with (1), an intrinsic low cross-sensitivity to temperature and (2), elementary design and fabrication. Three concepts, using either a quartz capillary, an Invar capillary or a thin polyimide film as the force sensitive element were prototyped and subjected to both static and dynamic testing. The force transducer based on a quartz capillary presented the lowest cross-sensitivity to temperature ( 12 m N / ∘ C) and good accuracy (maximum measurement error of 65 m N /10 N ) in a measurement of static forces. However, limited strength of the sensor is expected to prevent usage of the quartz capillary in small diameter needles. The concepts for a sensor based on an Invar capillary or a thin polyimide film proved a higher cross-sensitivity to temperature ( 50 m N / ∘ C and 220 m N / ∘ C, respectively) and higher maximum measurement error (350 m N /10 N , 800 m N /10 N ), comparable to those of FBG-based sensors reported in literature, but are likely to be more suitable for integration in very small biopsy needles.

Learning from visual force feedback in box trainers: tissue manipulation in laparoscopic surgery.

BACKGROUND: Currently, task time and errors are often used as performance parameters in laparoscopic training. Training with the focus on task time improvement alone results in fast, but possibly less controlled, instrument movements and therefore suboptimal tissue handling skills. METHODS: Twenty-five medical students were randomly assigned in two groups. Both groups performed a tissue manipulation task six times. During this training session, the time feedback group (n = 13) received real-time visual feedback of the task time. The force feedback group (n = 12) received real-time visual feedback of the tissue manipulation force. After the training sessions, participants in both groups performed an entirely different task without visual feedback. Task time, force, and motion parameters of this posttest were used to compare the technical skills of the medical students. RESULTS: The training data of the group that received force feedback showed a learning curve for the mean and max absolute force, max force area, force volume, task time, and path length of both instruments. The data from the group that received time feedback showed a learning curve for the max force, task time, and path length of both instruments. In the posttest, the parameters of mean absolute force (p = 0.039), max force (p = 0.041), and force volume (p = 0.009) showed a significant difference in favor of the group that received force feedback. CONCLUSIONS: The learning curves and the posttest indicate that training with visual force feedback improves tissue handling skills with no negative effect on the task time and instrument motions. Conventional laparoscopic training with visual time feedback improves instrument motion and task time, but it does not improve tissue manipulation skills.

Therapeutic prostate cancer interventions: quantification of pubic arch interference and needle positioning errors.

INTRODUCTION: This study focuses on the quantification of and current guidelines on the hazards related to needle positioning in prostate cancer treatment: (1) access restrictions to the prostate gland by the pubic arch, so-called Pubic Arch Interference (PAI) and (2) needle positioning errors. Next, we propose solution strategies to mitigate these hazards. METHODS: The literature search was executed in the Embase, Medline ALL, Web of Science Core Collection*, and Cochrane Central Register of Controlled Trials databases. RESULTS: The literature search resulted in 50 included articles. PAI was reported in patients with various prostate volumes. The level of reported PAI varied between 0 and 22.3 mm, depending on the patient's position and the measuring method. Low-Dose-Rate Brachytherapy induced the largest reported misplacement errors, especially in the cranio-caudal direction (up to 10 mm) and the largest displacement errors were reported for High-Dose-Rate Brachytherapy in the cranio-caudal direction (up to 47 mm), generally increasing over time. CONCLUSIONS: Current clinical guidelines related to prostate volume, needle positioning accuracy, and maximum allowable PAI are ambiguous, and compliance in the clinical setting differs between institutions. Solutions, such as steerable needles, assist in mitigating the hazards and potentially allow the physician to proceed with the procedure.This systematic review was performed in accordance with the PRISMA guidelines. The review was registered at Protocols.io (DOI: dx.doi.org/10.17504/protocols.io.6qpvr89eplmk/v1).

The influence of instrument configuration on tissue handling force in laparoscopy.

In single-access surgery, instruments enter the abdominal cavity through only 1 incision, the position of the instruments relative to each other is different compared with that in conventional laparoscopy. Changes in instrument configuration may increase task complexity and therefore affect tissue handling skills. The aim of this study is to determine if a relation exists between instrument configuration and tissue interaction force. A study was performed to investigate the differences in manipulation force between a single-port (SP) and 2-port (TP) instrument configuration in a standard box trainer. A force platform was placed under a tissue manipulation task in a box trainer and used to measure the pulling forces and trial time. A total of 28 medical students with no previous experience in laparoscopic surgery were divided into 2 equal groups. Group 1 trained the task 6 times with the TP configuration and subsequently performed 6 trials with the SP configuration. Group 2 used the configurations in the opposite order. For both groups, the learning curves of the maximum force and task time were compared. Time and maximum pulling forces were significantly different between the 2 instrument configurations. In both groups, the participants used significantly more force in the SP configuration than in the TP configuration. The force data indicate that the increased complexity in instrument handling with straight instruments in a SP configuration increases the tissue manipulation force. Furthermore, the tissue handling skills of novices who mastered the task with the TP configuration decreased after switching to the SP configuration.

Changes in needle maneuver space and optimal insertion site for midline neuraxial puncture with progressive age: an analysis in computed tomography scans.

INTRODUCTION: We systematically describe the morphology and accessibility of interspinous spaces across age groups of patients. Our primary goal was to objectively estimate if the maneuver space for a virtual spinal needle changes with age. Our secondary goal was to estimate if the optimal site and angle for midline neuraxial puncture change with age. METHODS: Measurements were performed in mid-sagittal CT images. The CT images were retrospectively collected from the database of the Department of Radiology of our hospital. Three age groups were studied: 21-30 years (n=36, abbreviated Y(oung)), 51-60 years (n=43, abbreviated M(iddle-aged)) and older than 80 years (n=46, abbreviated Old).A needle trajectory is defined by the chosen puncture point and by the angle at which the needle is directed to its target. We define a Spinal Accessibility Index (SAI) by numerically integrating for an interspace all possible combinations of puncture points and angles that lead to a successful virtual puncture. Successful in this context means that the needle tip reaches the spinal or epidural space without bone contact. Reproducible calculation of the SAI was performed with the help of custom-made software. The larger the value of the SAI, the more possible successful needle trajectories exist that the practitioner may choose from.The optimal puncture point and optimal angle in an age group at a certain level of the spine are defined by the combination of these two, which generates the highest success rate of the entire sample of this age group. RESULTS: At all levels of the spine, the median SAI differed significantly between age groups (independent-samples Kruskal-Wallis test, p<0.001-0.047). The SAI consistently decreased with increasing age. Post-hoc analyses using pairwise comparisons showed a significantly higher SAI in group Y versus Old at all levels (p<0.001-0.006) except at level thoracic (Th)1-Th2 (p=0.138). The SAI was significantly higher in group M versus Old at all levels (p<0.001-0.028) except at level Th1-Th2 (p=0.061), Th4-Th5 (p=0.083), Th9-Th10 (p=1.00) and Th10-Th11 (p=1.00). CONCLUSIONS: Needle maneuver space in midline neuraxial puncture significantly decreases with progressive age at all levels of the spine. Optimal puncture points and angles are similar between age groups.

Visual force feedback in laparoscopic training.

BACKGROUND: To improve endoscopic surgical skills, an increasing number of surgical residents practice on box or virtual reality (VR) trainers. Current training is focused mainly on hand-eye coordination. Training methods that focus on applying the right amount of force are not yet available. METHODS: The aim of this project is to develop a low-cost training system that measures the interaction force between tissue and instruments and displays a visual representation of the applied forces inside the camera image. This visual representation continuously informs the subject about the magnitude and the direction of applied forces. To show the potential of the developed training system, a pilot study was conducted in which six novices performed a needle-driving task in a box trainer with visual feedback of the force, and six novices performed the same task without visual feedback of the force. All subjects performed the training task five times and were subsequently tested in a post-test without visual feedback. RESULTS: The subjects who received visual feedback during training exerted on average 1.3 N (STD 0.6 N) to drive the needle through the tissue during the post-test. This value was considerably higher for the group that received no feedback (2.6 N, STD 0.9 N). The maximum interaction force during the post-test was noticeably lower for the feedback group (4.1 N, STD 1.1 N) compared with that of the control group (8.0 N, STD 3.3 N). CONCLUSIONS: The force-sensing training system provides us with the unique possibility to objectively assess tissue-handling skills in a laboratory setting. The real-time visualization of applied forces during training may facilitate acquisition of tissue-handling skills in complex laparoscopic tasks and could stimulate proficiency gain curves of trainees. However, larger randomized trials that also include other tasks are necessary to determine whether training with visual feedback about forces reduces the interaction force during laparoscopic surgery.

Suturing intraabdominal organs: when do we cause tissue damage?

BACKGROUND: It is generally assumed that safety of tissue manipulations during (laparoscopic) surgery is related to the magnitude of force that is exerted on the tissue. To provide trainees with performance feedback about tissue-handling skills, it is essential to define objective criteria for judging the safety of applied forces. To be of clinical relevance, these criteria should relate the applied forces to the risk of tissue damage. This experimental study was conducted to determine which tractive forces during suturing cause tissue damage in different types of porcine tissues. METHODS: Tractive forces were applied on eight different tissue types (fascia, aorta, vena cava, peritoneum, small and large bowel, uterus, and fallopian tube) of 10 different pigs by placing increasingly higher loads on sutures in the tissue. We determined the load at what tissue damage occurred through visual inspection of the tissue. For each tissue sample, three consecutive measurements were performed. RESULTS: The average maximum acceptable force varied between 11.43 N for fascia to 1.25 N for fallopian tube. The difference in allowable force between these two structures is almost tenfold. Small bowel can be handled with a tractive force almost 1.5-fold higher than large bowel. CONCLUSIONS: Each tissue type was found to have its own individual range of acceptable maximum forces before visual tissue damage occurs. With the results presented in this study, it is possible to provide clinically relevant and validated feedback to trainees about their tissue-handling skills.

Implications of the law on video recording in clinical practice.

BACKGROUND: Technological developments allow for a variety of applications of video recording in health care, including endoscopic procedures. Although the value of video registration is recognized, medicolegal concerns regarding the privacy of patients and professionals are growing. A clear understanding of the legal framework is lacking. Therefore, this research aims to provide insight into the juridical position of patients and professionals regarding video recording in health care practice. METHODS: Jurisprudence was searched to exemplify legislation on video recording in health care. In addition, legislation was translated for different applications of video in health care found in the literature. RESULTS: Three principles in Western law are relevant for video recording in health care practice: (1) regulations on privacy regarding personal data, which apply to the gathering and processing of video data in health care settings; (2) the patient record, in which video data can be stored; and (3) professional secrecy, which protects the privacy of patients including video data. Practical implementation of these principles in video recording in health care does not exist. CONCLUSION: Practical regulations on video recording in health care for different specifically defined purposes are needed. Innovations in video capture technology that enable video data to be made anonymous automatically can contribute to protection for the privacy of all the people involved.

Accuracy of needle position measurements using fiber Bragg gratings.

Accurate placement of the needle tip is essential in percutaneous therapies such as radiofrequency ablation (RFA) of liver tumors. Use of a robotic system for navigating the needle could improve the targeting accuracy. Real-time information on the needle tip position is needed, since a needle deflects during insertion in tissue. Needle shape can be reconstructed based on strain measurements within the needle. In the current experiment we determined the accuracy with which the needle tip position can be derived from strain measurements using Fiber Bragg Gratings (FBGs). Three glass fibers equipped with two FBGs each were incorporated in a needle. The needle was clamped at one end and deformed by applying static radial displacements at one or two locations. The FBG output was used for offline estimation of the needle shape and tip position. During deflections of the needle tip up to 12.5 mm, the tip position was estimated with a mean accuracy of 0.89 mm (std 0.42 mm). Adding a second deflection resulted in an error of 1.32 mm (std 0.48 mm). This accuracy is appropriate for applications such as RFA of liver tumors. The results further show that the accuracy can be improved by optimizing the placement of FBGs.

Overcoming pubic arch interference in prostate brachytherapy using steerable needles.

Purpose: A proportion of patients are not directly eligible for prostate brachytherapy (BT) due to pubic arch interference (PAI). Constraints in positioning sources behind the pubic arch due to linear, horizontal needle paths, may hamper effective irradiation of the target volume. This work evaluated the effect of prostate volume (Vp) and patient posture change on the amount of PAI, and demonstrated that steerable needles may broaden the inclusion criteria for patients with enlarged prostates and observed PAI. Material and methods: Twenty-seven patients (Vp > 60 cc) were included in this study. Access obstruction to the prostate was evaluated using diagnostic magnetic resonance imaging (MRI) scans, after six upward rotations of the pelvis and the prostate in 5 degree steps, to indicate the effect of patient posture change from supine to lithotomy position. For patients with PAI, we evaluated if the steerable needle could access the obstructed volume of the prostate. Results: The data showed no clear relation between Vp and PAI. In 23 of the 27 patients, in which PAI was observed, 14 showed obstruction of the prostate of ≥ 10 mm in the supine position (mean PAI ± standard deviation: 15.2 ±3.8 mm). Anatomical rotation reduced PAI by 4.8 mm after every 10 degrees of upward rotation, still resulting in obstructions of 8.1 ±2.4 mm in 10 of the 14 cases after 15 degree rotation. The steerable needle enabled access to all the required coordinates of the prostate. Conclusions: The ability to steer along curved paths enables prostate BT in patients with enlarged prostates and PAI, and reduces the change of needing to abandon treatment.

Steerable needles for radio-frequency ablation in cirrhotic livers.

Accurate needle placement in deep-seated liver tumours can be difficult. In this work, we disclose two new manually controlled steerable needles for 17G radio-frequency ablation probe placement. The needles contain stylets with embedded compliant joints for active tip articulations, and concentric tubes for (curved-path) guidance. Needle steering was evaluated sequentially by intended users and in intended-use tissue types. Six interventional radiologists evaluated the needle in repeated ultrasound-guided steering tasks in liver-mimicking phantoms. Targets were located at a 100 mm depth and 20 mm lateral offset from the initial insertion line. The resulting mean absolute tip placement error was 1.0 ± 1.0 mm. Subsequently, steering-induced tissue damage was evaluated in fresh cirrhotic human liver explants. The surface area of puncture holes was estimated in scanned histology slides, using a connected-components analysis. The mean surface area was 0.26 ± 0.16 mm2 after steering with a median radius of curvature of 0.7 × 103 mm, versus 0.35 ± 0.15 mm2 after straight-path insertions with the steerable needle and 0.15 ± 0.09 mm2 after straight-path RFA probe insertions. The steering mechanisms proposed enable clinically relevant path corrections for 17G needles. Radiologists were quickly adept in curved-path RFA probe placement and the evaluation of histological tissue damage demonstrated a potentially safe use during liver interventions.

Block-matching-based registration to evaluate ultrasound visibility of percutaneous needles in liver-mimicking phantoms.

PURPOSE: To present a novel methodical approach to compare visibility of percutaneous needles in ultrasound images. METHODS: A motor-driven rotation platform was used to gradually change the needle angle while capturing image data. Data analysis was automated using block-matching-based registration, with a tracking and refinement step. Every 25 frames, a Hough transform was used to improve needle alignments after large rotations. The method was demonstrated by comparing three commercial needles (14G radiofrequency ablation, RFA; 18G Trocar; 22G Chiba) and six prototype needles with different sizes, materials, and surface conditions (polished, sand-blasted, and kerfed), within polyvinyl alcohol phantom tissue and ex vivo bovine liver models. For each needle and angle, a contrast-to-noise ratio (CNR) was determined to quantify visibility. CNR values are presented as a function of needle type and insertion angle. In addition, the normalized area under the (CNR-angle) curve was used as a summary metric to compare needles. RESULTS: In phantom tissue, the first kerfed needle design had the largest normalized area of visibility and the polished 1 mm diameter stainless steel needle the smallest (0.704 ± 0.199 vs. 0.154 ± 0.027, p < 0.01). In the ex vivo model, the second kerfed needle design had the largest normalized area of visibility, and the sand-blasted stainless steel needle the smallest (0.470 ± 0.190 vs. 0.127 ± 0.047, p < 0.001). As expected, the analysis showed needle visibility peaks at orthogonal insertion angles. For acute or obtuse angles, needle visibility was similar or reduced. Overall, the variability in needle visibility was considerably higher in livers. CONCLUSION: The best overall visibility was found with kerfed needles and the commercial RFA needle. The presented methodical approach to quantify ultrasound visibility allows comparisons of (echogenic) needles, as well as other technological innovations aiming to improve ultrasound visibility of percutaneous needles, such as coatings, material treatments, and beam steering approaches.