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Ara Darzi

Publications and source records attributed to Ara Darzi.

At least 55 records · Page 3Linked to original sources
PubMed2005

Laparoscope self-calibration for robotic assisted minimally invasive surgery.

For robotic assisted minimal access surgery, recovering 3D soft tissue deformation is important for intra-operative surgical guidance, motion compensation, and prescribing active constraints. We propose in this paper a method for determining varying focal lengths of stereo laparoscope cameras during robotic surgery. Laparoscopic images typically feature dynamic scenes of soft-tissue deformation and self-calibration is difficult with existing approaches due to the lack of rigid temporal constraints. The proposed method is based on the direct derivation of the focal lengths from the fundamental matrix of the stereo cameras with known extrinsic parameters. This solves a restricted self-calibration problem, and the introduction of the additional constraints improves the inherent accuracy of the algorithm. The practical value of the method is demonstrated with analysis of results from both synthetic and in vivo data sets.

Algorithms↗
PubMed2005

Soft-tissue motion tracking and structure estimation for robotic assisted MIS procedures.

In robotically assisted laparoscopic surgery, soft-tissue motion tracking and structure recovery are important for intraoperative surgical guidance, motion compensation and delivering active constraints. In this paper, we present a novel method for feature based motion tracking of deformable soft-tissue surfaces in totally endoscopic coronary artery bypass graft (TECAB) surgery. We combine two feature detectors to recover distinct regions on the epicardial surface for which the sparse 3D surface geometry may be computed using a pre-calibrated stereo laparoscope. The movement of the 3D points is then tracked in the stereo images with stereo-temporal constrains by using an iterative registration algorithm. The practical value of the technique is demonstrated on both a deformable phantom model with tomographically derived surface geometry and in vivo robotic assisted minimally invasive surgery (MIS) image sequences.

Algorithms↗
PubMed2005

Invisible shadow for navigation and planning in minimal invasive surgery.

Depth estimation is one of the most fundamental challenges for performing minimally invasive surgical (MIS) procedures. The requirement of accurate 3D instrument navigation using limited visual depth cues makes such tasks even more difficult. With the constant expectation of improving safety for MIS, there is a growing requirement for overcoming such constraints during MIS. We present in this paper a method of improving the surgeon's perception of depth by introducing an "invisible shadow" in the operative field cast by an endoscopic instrument. Although, the shadow is invisible to human perception, it can be digitally detected, enhanced and re-displayed. Initial results from our study suggest that this method improves depth perception especially when the endoscopic instrument is in close proximity to the surface. Experiment results have shown that the method could potentially be used as an instrument navigation aid allowing accurate maneuvering of the instruments whilst minimizing tissue trauma.

Algorithms↗
PubMed2005

A comparison of open vs. laparoscopic abdominal rectopexy for full-thickness rectal prolapse: a meta-analysis.

PURPOSE: Using meta-analytical techniques, this study was designed to compare open and laparoscopic abdominal procedures used to treat full-thickness rectal prolapse in adults. METHODS: Comparative studies published between 1995 and 2003, cited in the literature of open abdominal rectopexy vs. laparoscopic abdominal rectopexy, were used. The primary end points were recurrence and morbidity, and the secondary end points assessed were operative time and length of hospital stay. A random effect model was used to aggregate the studies reporting these outcomes, and heterogeneity was assessed. RESULTS: Six studies, consisting of a total of 195 patients (98 open and 97 laparoscopic) were included. Analysis of the data suggested that there is no significant difference in recurrence and morbidity between laparoscopic abdominal rectopexy and open abdominal rectopexy. Length of stay was significantly reduced in the laparoscopic group by 3.5 days (95 percent confidence interval, 3.1-4; P < 0.01), whereas the operative time was significantly longer in this group, by approximately 60 minutes (60.38 minutes; 95 percent confidence interval, 49-71.8). CONCLUSIONS: Laparoscopic abdominal rectopexy is a safe and feasible procedure, which may compare equally with the open technique with regards to recurrence and morbidity and favorably with length of stay. However large-scale randomized trials, with comparative, sound methodology are still needed to ascertain detailed outcome measures accurately.

Adult↗
PubMed2005

Surgical skill is predicted by the ability to detect errors.

BACKGROUND: Objective analysis methods of surgical performance are now available so comparison between surgeons is available. One such method is by direct observation using the Objective Structured Assessment of Technical Skills (OSATS), but this is a time-consuming process; therefore, a simple screening tool for the ability to detect errors (previously validated) was analyzed and considered as a predictor of qualitative performance. METHODS: Thirty-eight volunteer surgeons were recruited to the skills laboratory to undertake 3 exercises. Two were bench-top surgical tasks that were scored using the global rating of the OSATS technique. The third task was the ability to detect simple errors in 22 synthetic models of common surgical procedures, some of which contained purposefully made errors. P<.05 was deemed to be statistically significant. RESULTS: The scores (interquartile ranges in parentheses) for the 3 sections were excision of sebaceous cyst=21 (19,24), closure of small bowel enterotomy=23 (21,27), and identification of errors=31 (27,34). Three scorers blinded to the operative models exhibited an interobserver reliability of .9 and .91 for the video tasks, respectively. Spearman's rank correlations between the error examination and performance on the 2 tasks were both statistically significant at .69 (cystectomy) and .54 (enterotomy). CONCLUSIONS: The ability to detect simple surgical errors is a predictor of technical skill and performance of bench tasks. What must be answered is whether the use of such models and principles can shorten the qualitative surgical learning curve.

Clinical Competence↗
PubMed2005

The reliability of multiple objective measures of surgery and the role of human performance.

BACKGROUND: There is a need for reliable and valid objective methods of technical skills in surgery. Six-bench surgical top stations have been combined to assess basic surgical trainees (BSTs) objectively. The current study examines its reliability and validity across repeat sittings. METHODS: Eleven surgical trainees (6 senior BSTs and 5 higher surgical trainees [HSTs]) undertook 5 sittings of the 6-station assessment designed to be completed within 90 minutes. The 6 stations consisted of knot tying, suturing, closure of enterotomy, excision of sebaceous cyst, laparoscopic task, and instrument examination. Methods of analysis employed were motion analysis, observation with criteria, and inbuilt simulation metrics. RESULTS: On analysis 3 knot tying and suturing stations exhibited significant differences in either time or movement; any difference was over by the second run. The intertest reliabilities were .66, .74, .55, .51, and .65 for the 5 runs. The intratest reliability across repeated sittings varied from .56 to .96. The inter-rater reliability for video assessment varied from .77 to .94. CONCLUSION: The assessment is reliable and valid across repeated sittings. Its use in assessment of basic technical skills needs to be encouraged.

Clinical Competence↗
PubMed2005

Assessment of psychomotor skills acquisition during laparoscopic cholecystectomy courses.

BACKGROUND: Standardized short courses in laparoscopic cholecystectomy aim to teach laparoscopic skills to surgical trainees, although end-of-course assessments of performance remain subjective. The current study aims to objectively assess psychomotor skills acquisition of trainees attending laparoscopic cholecystectomy courses. METHODS: Thirty-seven junior surgical trainees had their laparoscopic skills assessed before and after attending 1 of 3 separate 2-day courses (A, B, and C), all with identical format. Assessments were comprised of a standardized simulated laparoscopic task, with performance measured using a valid electromagnetic hand-motion tracking device. RESULTS: Overall, trainees made significant improvements in path length (P=.006), number of movements (P<.001), and time taken (P<.001). Analyzing the 3 courses separately, only trainees attending courses A and C made significant improvements. DISCUSSION: Objective validated methods can be used to assess learning of psychomotor skills on courses. In addition to providing participants with an insight into their skills, these data can be used to demonstrate course efficacy.

Cholecystectomy, Laparoscopic↗
PubMed2005

Does minimally invasive vein harvesting technique affect the quality of the conduit for coronary revascularization?

The effect of minimally invasive great saphenous vein harvest on patient morbidity (wound infection and other healing disturbances) has been extensively investigated, yet its impact on the quality of the venous conduit is less well known. This study aims to review the literature with regard to macroscopic quality, postoperative myocardial infarction rates, and angiographic patency of the minimally invasive versus conventionally harvested vein using meta-analytic techniques where appropriate. Results suggest that conduits are comparable in macroscopic quality with minimally invasively harvested veins requiring more repairs prior to grafting. Postoperative myocardial infarction rates were not significantly different between groups, which is supported by the limited evidence on angiographic patency.

Coronary Artery Bypass↗
PubMed2005

Do technical parameters affect the diagnostic accuracy of virtual bronchoscopy in patients with suspected airways stenosis?

PURPOSE: Virtual bronchoscopy has gained popularity over the past decade as an alternative investigation to conventional bronchoscopy in the diagnosis, grading and monitoring of airway disease. The effect of technical parameters on diagnostic outcome from virtual bronchoscopy has not been determined. This meta-analysis aims to estimate accuracy of virtual compared to conventional bronchoscopy in patients with suspected airway stenosis, and evaluate the influence of technical parameters. MATERIALS AND METHODS: A MEDLINE search was used to identify relevant published studies. The primary endpoint was the "correct diagnosis" of stenotic lesions on virtual compared to conventional bronchoscopy. Secondary endpoints included the effects of the technical parameters (pitch, collimation, reconstruction interval, rendering method, and scanner type), and date of publication on the diagnostic accuracy of virtual bronchoscopy. RESULTS: Thirteen studies containing 454 patients were identified. Meta-analysis showed good overall diagnostic performance with 85% calculated pooled sensitivity (95% CI 77-91%), 87% specificity (95% CI 81-92%) and area under the curve (AUC) of 0.947. Subgroups included collimation of 3mm or more (AUC 0.948), pitch of 1 (AUC 0.955), surface rendering technique (AUC 0.935), and reconstruction interval of more than 1.25 mm (AUC 0.914). There was no significant difference in accuracy accounting for publication date, scanner type or any of the above variables. Weighted regression analysis confirmed none of these variables could significantly account for study heterogeneity. CONCLUSION: Virtual bronchoscopy performs well in the investigation of patients with suspected airway stenosis. Overall sensitivity and specificity and diagnostic odds ratio for diagnosis of airway stenosis were high. The effects of pitch, collimation, reconstruction interval, rendering technique, scanner type, and publication date on diagnostic accuracy were not significant.

Airway Obstruction↗
PubMed2005

Organising a surgical skills centre.

The aim of this paper is to define a strategy for the development and organisation of a surgical skills centre. The areas of interest can be divided into decisions about who, what and where to teach, the importance of an approach which is competency-based, definition of staff to run the centre, and also the use of the centre for the purposes of assessment, as well as training. The efficient delivery of this service will be augmented by adopting a multi-disciplinary and multi-professional approach, and must also be malleable enough to adopt future developments, such as web-based learning. Simulation is now the preferred mode of practice for commencement of surgical training. Surgical skills centres must be able to supply users with tools in a suitably designed environment, which enables them to move along a curriculum which is delivered in a competency-based manner.

Journal Article↗
PubMed2005

A human factors analysis of technical and team skills among surgical trainees during procedural simulations in a simulated operating theatre.

BACKGROUND: High-risk organizations such as aviation rely on simulations for the training and assessment of technical and team performance. The aim of this study was to develop a simulated environment for surgical trainees using similar principles. METHODS: A total of 27 surgical trainees carried out a simulated procedure in a Simulated Operating Theatre with a standardized OR team. Observation of OR events was carried out by an unobtrusive data collection system: clinical data recorder. Assessment of performance consisted of blinded rating of technical skills, a checklist of technical events, an assessment of communication, and a global rating of team skills by a human factors expert and trained surgical research fellows. The participants underwent a debriefing session, and the face validity of the simulated environment was evaluated. RESULTS: While technical skills rating discriminated between surgeons according to experience (P = 0.002), there were no differences in terms of the checklist and team skills (P = 0.70). While all trainees were observed to gown/glove and handle sharps correctly, low scores were observed for some key features of communication with other team members. Low scores were obtained by the entire cohort for vigilance. Interobserver reliability was 0.90 and 0.89 for technical and team skills ratings. CONCLUSIONS: The simulated operating theatre could serve as an environment for the development of surgical competence among surgical trainees. Objective, structured, and multimodal assessment of performance during simulated procedures could serve as a basis for focused feedback during training of technical and team skills.

Attention↗
PubMed2005

A practical approach towards accurate dense 3D depth recovery for robotic laparoscopic surgery.

OBJECTIVE: Recovering tissue deformation during robotic-assisted minimally invasive surgery (MIS) is an important step towards motion compensation and stabilization. This article presents a practical strategy for dense 3D depth recovery and temporal motion tracking for deformable surfaces. METHODS: The method combines image rectification with constrained disparity registration for reliable depth estimation. The accuracy and practical value of the technique are validated using a tissue phantom with known 3D geometry and motion characteristics and in vivo data. RESULTS: Results from the phantom model correctly follow the motion trend indicated from the ground truth provided by CT scanning, and regression analysis shows the intrinsic accuracy that can be achieved with the proposed technique. Results applied to in vivo robotic-assisted MIS data are also provided, indicating the practical value of the proposed method. CONCLUSION: The proposed method presents a practical strategy for dense depth recovery of surface structure in robotic-assisted MIS that incorporates stereo vision. Results on phantom and in vivo data indicate the quality of the method and also highlight the importance of further considering the effects of specular highlights.

Algorithms↗
PubMed2005

Laparoscopic task recognition using Hidden Markov Models.

Surgical skills assessment has been paid increased attention over the last few years. Stochastic models such as Hidden Markov Models have recently been adapted to surgery to discriminate levels of expertise. Based on our previous work combining synchronized video and motion analysis we present preliminary results of a HMM laparoscopic task recognizer which aims to model hand manipulations and to identify and recognize simple surgical tasks.

Clinical Competence↗
PubMed2005

Soft tissue deformation using a nonlinear hierarchical finite element model with real-time online refinement.

Simulating soft tissue deformation in real-time is a requirement for realistically rendering the VR interaction between human organs and surgical tools. Finite Element Model (FEM) describes complex mechanical and physiological behaviour but it is computationally too demanding especially when a nonlinear model is to be implemented. For this reason, we introduce a multiresolution approach to FEM that only employs the region of the object under deformation to find the solution of the differential equations of motion. In order to increase the quality of the deformation, refinement of the original mesh is performed with the insertion of new surface nodes in real-time in the region of interaction. To guarantee the stability of the nonlinear model, the presence of flat tetrahedra (slivers) has to be avoided; therefore a sliver elimination technique has been implemented resulting in a more stable simulation.

Clinical Competence↗
PubMed2005

Inguinal hernia.

Explore the source record for details and available documents.

Hernia, Inguinal↗
PubMed2005

Haemostasis using a ready-to-use collagen sponge coated with activated thrombin and fibrinogen.

Adequate haemostasis is an important part of any surgical procedure, but particularly so in the case of visceral organ surgery where apparently insignificant ooze can ultimately result in significant haemorrhage and coagulopathy. To achieve haemorrhage control, the surgeon may use conventional techniques (eg, suture ligation, diathermy, and swab compression), but failing this has the option of using physical coagulation tools (eg, the argon beam coagulator) and haemostasis adjuncts (eg, fibrin glues and collagen sheets). Advances in manufacturing have led to development of several other haemostatic products including absorbable gelatin sponges, cyanoacrylates, and polymer-based adhesives. One such product consists of a fixed, ready-to-use equine collagen sponge coated with human thrombin and fibrinogen. It may be applied directly to the bleeding surface, without the need for preparation or reconstitution. This chapter reviews the published evidence and compares its use to other classes of haemostasis adjuncts across a range of surgical specialties, namely hepatic, splenic, thoracic, vascular, and minimally invasive surgery. It also aims to highlight the apparent advantages and limitations of the fibrinogen and thrombin-coated collagen sponge compared to other commercially available haemostasis adjuncts, and identify potential applications for the product.

Animals↗
PubMed2004

Robotic assisted rectopexy.

BACKGROUND: During the last 3 years, robotic surgery has had a considerable impact on minimally invasive surgery in a wide range of specialties. This study describes the surgical technique and preliminary results of our first 6 cases of robotic assisted suture rectopexy. METHODS: During a period of 13 months 6 patients with full thickness rectal prolapse were operated on with the da Vinci surgical system. All patients were considered suitable for a suture rectopexy. Setting-up time, procedure time, patient recovery, and hospital stay were recorded and compared with the current literature. RESULTS: All operations were completed successfully using the robotic system. There were no major complications and no deaths. Mean setting-up time was 28 minutes, mean operation time was 127 minutes, and mean hospital stay was 6 days. At 3 to 6 months of follow-up all patients are in good health, with no signs of recurrence and no reports of constipation. CONCLUSIONS: Robotic assisted suture rectopexy is feasible and safe and apparently meets accepted standards of laparoscopic surgery.

Adult↗