Preferences for Surveillance of Barrett's Oesophagus: a Discrete Choice Experiment.

PURPOSE: Endoscopic surveillance for Barrett's oesophagus is undertaken to detect dysplasia and early cancer, and to facilitate early intervention. Evidence supporting current practice is of low quality and often influenced by opinion. This study investigated the preferences of patients for surveillance of Barrett's oesophagus in an Australian cohort. METHODS: Four Barrett's oesophagus surveillance characteristics/attributes were evaluated within a discrete choice experiment based on literature and expert opinion: (1) surveillance method (endoscopy vs a blood test vs a novel breath test), (2) risk of missing a cancer over a 10-year period, (3) screening interval, and (4) out-of-pocket cost. The data from the discrete choice experiment was analysed within the framework of random utility theory using a mixed logit regression model. RESULTS: The study sample comprised patients (n = 71) undergoing endoscopic surveillance for Barrett's oesophagus of whom n = 65 completed the discrete choice experiment. The sample was predominantly male (77%) with average age of 65 years. All attributes except surveillance method significantly influenced respondents' preference for Barrett's oesophagus surveillance. Policy analyses suggested that compared to the reference case (i.e. endoscopy provided annually at no upfront cost and with a 4% risk of missing cancer), increasing test sensitivity to 0.5% risk of missing cancer would increase participation by up to 50%; surveillance every 5 years would lead to 26% reduction, while every 3 to 3.5 years would result in 7% increase in participation. Respondents were highly averse to paying A$500 for the test, resulting in 48% reduction in participation. None of the other surveillance methods was preferred to endoscopy, both resulting in 11% reduction in participation. CONCLUSION: Test sensitivity, test frequency and out-of-pocket cost were the key factors influencing surveillance uptake. Patients prefer a test with the highest sensitivity, offered frequently, that incurs no upfront costs.

Endoscopic cyst-gastrostomy for pancreatic pseudocysts: refining the indications.

BACKGROUND: Pseudocysts are a common consequence of acute pancreatitis and require intervention if symptomatic. Endoscopic management is emerging as a safe and effective alternative to surgery, although its use is not yet widespread. METHODS: We describe our experience of 10 consecutive unselected patients who underwent endoscopic ultrasound-guided cyst-gastrostomy and stent insertion at a tertiary referral centre. Technical aspects of the procedure are detailed with accompanying photographs. RESULTS: Six patients made an uneventful recovery. Four patients developed complications, of which one was successfully salvaged by endoscopy and three required surgery. CONCLUSION: We discuss technical and patient factors which may have contributed to these complications in the context of current literature, and in particular, found that the presence of necrosis was associated with higher morbidity, both in our series and in others. In our experience, endoscopic ultrasound-guided cyst-gastrostomy is best employed in simple, mature pseudocysts without necrotic debris, and we recommend this procedure only after a detailed assessment of the pseudocyst in a specialist hepatobiliary unit.

Australian clinical practice guidelines for the diagnosis and management of Barrett's esophagus and early esophageal adenocarcinoma.

Barrett's esophagus (BE), a common condition, is the only known precursor to esophageal adenocarcinoma (EAC). There is uncertainty about the best way to manage BE as most people with BE never develop EAC and most patients diagnosed with EAC have no preceding diagnosis of BE. Moreover, there have been recent advances in knowledge and practice about the management of BE and early EAC. To aid clinical decision making in this rapidly moving field, Cancer Council Australia convened an expert working party to identify pertinent clinical questions. The questions covered a wide range of topics including endoscopic and histological definitions of BE and early EAC; prevalence, incidence, natural history, and risk factors for BE; and methods for managing BE and early EAC. The latter considered modification of lifestyle factors; screening and surveillance strategies; and medical, endoscopic, and surgical interventions. To answer each question, the working party systematically reviewed the literature and developed a set of recommendations through consensus. Evidence underpinning each recommendation was rated according to quality and applicability.

A case of pancreatic cancer in the setting of autoimmune pancreatitis with nondiagnostic serum markers.

Background. Autoimmune pancreatitis (AIP) often mimics pancreatic cancer. The diagnosis of both conditions is difficult preoperatively let alone when they coexist. Several reports have been published describing pancreatic cancer in the setting of AIP. Case Report. The case of a 53-year-old man who presented with abdominal pain, jaundice, and radiological features of autoimmune pancreatitis, with a "sausage-shaped" pancreas and bulky pancreatic head with portal vein impingement, is presented. He had a normal serum IgG4 and only mildly elevated Ca-19.9. Initial endoscopic ultrasound-(EUS-) guided fine-needle aspiration (FNA) of the pancreas revealed an inflammatory sclerosing process only. A repeat EUS guided biopsy following biliary decompression demonstrated both malignancy and features of autoimmune pancreatitis. At laparotomy, a uniformly hard, bulky pancreas was found with no sonographically definable mass. A total pancreatectomy with portal vein resection and reconstruction was performed. Histology revealed adenosquamous carcinoma of the pancreatic head and autoimmune pancreatitis and squamous metaplasia in the remaining pancreas. Conclusion. This case highlights the diagnostic and management difficulties in a patient with pancreatic cancer in the setting of serum IgG4-negative, Type 2 AIP.

Circumferential location predicts the risk of high-grade dysplasia and early adenocarcinoma in short-segment Barrett's esophagus.

BACKGROUND: Whether early Barrett's neoplasia has a predilection for particular spatial locations in shorter segment disease is currently unknown. Anatomic factors may play a role in lesion location because of differing levels of mucosal acid exposure. OBJECTIVE: To identify high-risk lesion locations, which has important implications for surveillance strategies. DESIGN: We interrogated a prospectively maintained database of patients who underwent endoscopic resection (ER) for Barrett's neoplasia at 2 Australian tertiary centers. Lesions targeted for ER were characterized and their location in the distal esophagus was noted as on a clock face. A Z test of proportions was used to test for deviation from uniformity in the distribution of lesions. SETTING: Two Australian tertiary centers. PATIENTS: Patients who underwent ER for Barrett's neoplasia. MAIN OUTCOME MEASUREMENTS: Lesion location in the distal oesophagus, resected specimen histology. RESULTS: A total of 146 consecutive patients had ER for biopsy-proven high-grade dysplasia or esophageal adenocarcinoma. A total of 75 patients had Barrett's segment length of 5 cm or less and a visible lesion. Five patients had 2 visible lesions giving a total of 80 lesions. ER of 66 lesions (82.5%) led to the identification of advanced pathology: 37 high-grade dysplasia (46%), 24 mucosal adenocarcinoma (30%), 5 submucosal adenocarcinoma (6%). Of a total of 80 lesions, 43 (53.8%) (95% CI, 42.9%-64.7%) were centered within the 2- to 5-o'clock arc, comprising 25% of the circumference. This area also accounted for 36 (54.5%) of the 66 lesions with advanced histology (95% CI, 42.5%-66.5%). All confidence intervals lie wholly above the 25% expected in a uniform circular distribution (P < .05). LIMITATIONS: Observational study in a tertiary center. CONCLUSIONS: In Barrett's maximal segments of 5 cm or less, the 2- to 5-o'clock arc, accounts for approximately 50% of macroscopically visible lesions and associated early neoplasia. This finding has important implications for surveillance strategies.

Giant laterally spreading tumors of the duodenum: endoscopic resection outcomes, limitations, and caveats.

BACKGROUND: Giant hemicircumferential and greater nonampullary duodenal adenomas or laterally spreading tumors (LSTs) may be amenable to safe endoscopic resection, but little data exists on outcomes or risk stratification. DESIGN: We interrogated a prospectively maintained database of all patients who underwent endoscopic resection between January 2008 and November 2010. The resection technique was standardized. Major complications were defined as perforation, bleeding requiring readmission with hemoglobin drop of more than 20 g/L, or other substantial deviations from the usual clinical course. Outcomes were analyzed in 2 groups: giant lesions (>30 mm) and conventional duodenal polyps (<30 mm in diameter). Statistical evaluation was performed by using a χ(2) test. RESULTS: A total of 50 nonampullary duodenal polyps and LSTs were resected from 46 patients (23 men, mean age 59.4 years, range 35-83 years). Nineteen were giant hemicircumferential and greater LSTs (mean size 40.5 mm, range 30-80 mm), and 31 were less than 30 mm in diameter (mean size 14.5 mm, range 5-25 mm). Intraprocedural bleeding occurred more frequently in giant lesions (57.8% vs 19.3%, P = .005) and was treated with a combination of soft coagulation and endoscopic clips with hemostasis achieved in all cases. Major complications, mostly bleeding related, occurred in 5 patients (26.3%) with giant lesions and 1 patient (3.2%) with a smaller lesion (P = .014). There were no deaths. LIMITATION: Retrospective observational study in a tertiary center. CONCLUSIONS: Endoscopic resection of giant nonampullary duodenal LSTs is a successful treatment. However, it is hazardous and associated with significantly higher complication rates, primarily bleeding, when compared with conventional duodenal polypectomy. Safer and more effective hemostatic tools are required in this high-risk location.

Morphometric evaluation of duodenal biopsies in celiac disease.

OBJECTIVES: The Marsh classification is a semiquantitative method for the diagnosis and monitoring of changes in duodenal biopsies in celiac disease. We have explored the possibility that quantitative changes in villous area and crypt length (morphometry) may provide better information on changes in duodenal morphology, particularly after the introduction of a gluten-free diet. METHODS: We measured villous height, apical and basal villous widths, and crypt length in 57 adults with celiac disease and 83 control subjects. Villous area was calculated as a trapezoid approximation. Serial changes in villous area and crypt length were determined at regular intervals for up to 4 years after the introduction of a gluten-free diet. Morphometric changes were also correlated with Marsh grade, self-reported adherence to a gluten-free diet, and changes in celiac serology. RESULTS: The gluten-free diet resulted in a progressive increase in villous area and a progressive decrease in crypt length. Morphometric improvement reached a plateau after 6-12 months with mean villous area attaining a value approximately half that of control subjects. Morphometric data were more sensitive than Marsh grade. Improvement in morphometric indices was significantly associated with the disappearance of anti-endomysial IgA antibody but not with dietary compliance. CONCLUSIONS: Morphometry is a sensitive way to document changes in duodenal biopsies in celiac disease. In adults treated with a gluten-free diet, it is uncommon for villous area to return to values observed in control subjects, but morphometric improvement is associated with the disappearance of anti-endomysial IgA antibody.

Dynamic shape instantiation for intra-operative guidance.

Primary liver cancer and oligometastatic liver disease are one of the major causes of mortality worldwide and its treatment ranges from surgery to more minimally invasive ablative procedures. With the increasing availability of minimally invasive hepatic approaches, a real-time method of determining the 3D structure of the liver and its location during the respiratory cycle is clinically important. However, during treatment, it is difficult to acquire images spanning the entire 3D volume rapidly. In this paper, a dynamic 3D shape instantiation scheme is developed for providing subject-specific optimal scan planning. Using only limited planar information, it is possible to instantiate the entire 3D geometry of the organ of interest. The efficacy of the proposed method is demonstrated with both detailed numerical simulation and a liver phantom with known ground-truth data. Preliminary clinical application of the technique is evaluated on a patient group with metastatic liver tumours.

Dynamic view expansion for enhanced navigation in Natural Orifice Transluminal Endoscopic Surgery.

Natural Orifice Transluminal Endoscopic Surgery (NOTES) is an emerging surgical technique with increasing global interest. It has recently transcended the boundaries of clinical experiments towards initial clinical evaluation. Although profound benefits to the patient have been demonstrated, NOTES requires highly skilled endoscopists for it to be performed safely and successfully. This predominantly reflects the skill required to navigate a flexible endoscope through a spatially complex environment. This paper presents a method to extend the visual field of the surgeon without compromising on the safety of the patient. The proposed dynamic view expansion uses a novel parallax correction scheme to provide enhanced visual cues that aid the navigation and orientation during NOTES surgery in periphery, while leaving the focal view undisturbed. The method was validated using a natural orifice simulated surgical environment and demonstrated on in vivo porcine data.

Pq-space based non-photorealistic rendering for augmented reality.

The increasing use of robotic assisted minimally invasive surgery (MIS) provides an ideal environment for using Augmented Reality (AR) for performing image guided surgery. Seamless synthesis of AR depends on a number of factors relating to the way in which virtual objects appear and visually interact with a real environment. Traditional overlaid AR approaches generally suffer from a loss of depth perception. This paper presents a new AR method for robotic assisted MIS, which uses a novel pq-space based non-photorealistic rendering technique for providing see-through vision of the embedded virtual object whilst maintaining salient anatomical details of the exposed anatomical surface. Experimental results with both phantom and in vivo lung lobectomy data demonstrate the visual realism achieved for the proposed method and its accuracy in providing high fidelity AR depth perception.

Nonrigid 2-D/3-D registration for patient specific bronchoscopy simulation with statistical shape modeling: phantom validation.

This paper presents a nonrigid registration two-dimensional/three-dimensional (2-D/3-D) framework and its phantom validation for subject-specific bronchoscope simulation. The method exploits the recent development of five degrees-of-freedom miniaturized catheter tip electromagnetic trackers such that the position and orientation of the bronchoscope can be accurately determined. This allows the effective recovery of unknown camera rotation and airway deformation, which is modelled by an active shape model (ASM). ASM captures the intrinsic variability of the tracheo-bronchial tree during breathing and it is specific to the class of motion it represents. The method reduces the number of parameters that control the deformation, and thus greatly simplifies the optimisation procedure. Subsequently, pq-based registration is performed to recover both the camera pose and parameters of the ASM. Detailed assessment of the algorithm is performed on a deformable airway phantom, with the ground truth data being provided by an additional six degrees-of-freedom electromagnetic (EM) tracker to monitor the level of simulated respiratory motion.

Patient-specific bronchoscopy visualization through BRDF estimation and disocclusion correction.

This paper presents an image-based method for virtual bronchoscope with photo-realistic rendering. The technique is based on recovering bidirectional reflectance distribution function (BRDF) parameters in an environment where the choice of viewing positions, directions, and illumination conditions are restricted. Video images of bronchoscopy examinations are combined with patient-specific three-dimensional (3-D) computed tomography data through two-dimensional (2-D)/3-D registration and shading model parameters are then recovered by exploiting the restricted lighting configurations imposed by the bronchoscope. With the proposed technique, the recovered BRDF is used to predict the expected shading intensity, allowing a texture map independent of lighting conditions to be extracted from each video frame. To correct for disocclusion artefacts, statistical texture synthesis was used to recreate the missing areas. New views not present in the original bronchoscopy video are rendered by evaluating the BRDF with different viewing and illumination parameters. This allows free navigation of the acquired 3-D model with enhanced photo-realism. To assess the practical value of the proposed technique, a detailed visual scoring that involves both real and rendered bronchoscope images is conducted.

Photorealistic modeling of tissue reflectance properties.

OBJECTIVE: For Minimally Invasive Surgery (MIS) procedures, specular highlights constitute important visual cues for gauging tissue deformation as well as perceiving depth and orientation. This paper describes a novel reflectance modeling technique that is particularly suitable for simulating light interaction behavior with mucus-covered tissue surfaces. METHODS: The complex and largely random tissue-light interaction behavior is modeled with a noise-based approach. In the proposed technique, Perlin noise is used to modulate the shape of specular highlights and imitate the effects of the complex tissue structure on reflected lighting. For efficient execution, the noise texture is generated in pre-processing and stored in an image-based representation, i.e., a reflectance map. At run-time, the graphics hardware is used to attain per-pixel control and achieve realistic tissue appearance. RESULTS: The reflectance modeling technique has been used to replicate light-tissue reflection in surgical simulation. By comparing the results acquired against those obtained from conventional per-vertex Phong lighting and OpenGL multi-texturing, it is observed that the noise-based approach achieves improved tissue appearance similar to that observed in real procedures. Detailed user evaluation demonstrates the quality and practical value of the technique for increased perception of photorealism. CONCLUSION: The proposed technique presents a practical strategy for surface reflectance modeling that is suitable for real-time interactive surgical simulation. The use of graphics hardware further enhances the practical value of the technique.

Optimal sensor placement for predictive cardiac motion modeling.

Subject-specific physiological motion modeling combined with low-dimensional real-time sensing can provide effective prediction of acyclic tissue deformation particularly due to respiration. However, real-time sensing signals used for predictive motion modeling can be strongly coupled with each other but poorly correlated with respiratory induced cardiac deformation. This paper explores a systematic framework based on sequential feature selection for optimal sensor placement so as to achieve maximal model sensitivity and prediction accuracy in response to the entire range of tissue deformation. The proposed framework effectively resolves the problem encountered by traditional regression methods in that the latent variables from both the input and output of the regression model are used to establish their inner relationships. Detailed numerical analysis and in vivo results are provided, which demonstrate the potential clinical value of the technique.

Non-rigid 2D-3D registration with catheter tip EM tracking for patient specific bronchoscope simulation.

This paper investigates the use of Active Shape Models (ASM) to capture the variability of the intra-thoracic airway tree. The method significantly reduces the dimensionality of the non-rigid 2D/3D registration problem and leads to a rapid and robust registration framework. In this study, EM tracking data has been also incorporated through a probabilistic framework for providing a statistically optimal pose given both the EM and the image-based registration measurements. Comprehensive phantom experiments have been conducted to assess the key numerical factors involved in using catheter tip EM tracking for deformable 2D/3D registration.

Photo-realistic tissue reflectance modelling for minimally invasive surgical simulation.

Computer-based simulation is an important tool for surgical skills training and assessment. In general, the degree of realism experienced by the trainees is determined by the visual and biomechanical fidelity of the simulator. In minimally invasive surgery, specular reflections provide an important visual cue for tissue deformation, depth and orientation. This paper describes a novel image-based lighting technique that is particularly suitable for modeling mucous-covered tissue surfaces. We describe how noise functions can be used to control the shape of the specular highlights, and how texture noise is generated and encoded in image-based structure at a pre-processing stage. The proposed technique can be implemented at run-time by using the graphics processor to efficiently attain pixel-level control and photo-realism. The practical value of the technique is assessed with detailed visual scoring and cross comparison experiments by two groups of observers.

Predictive camera tracking for bronchoscope simulation with CONDensation.

This paper exploits the use of temporal information to minimize the ambiguity of camera motion tracking in bronchoscope simulation. The condensation algorithm (Sequential Monte Carlo) has been used to propagate the probability distribution of the state space. For motion prediction, a second-order auto-regressive model has been used to characterize camera motion in a bounded lumen as encountered in bronchoscope examination. The method caters for multimodal probability distributions, and experimental results from both phantom and patient data demonstrate a significant improvement in tracking accuracy especially in cases where there is airway deformation and image artefacts.

Patient-specific bronchoscope simulation with pq-space-based 2D/3D registration.

OBJECTIVE: The use of patient-specific models for surgical simulation requires photorealistic rendering of 3D structure and surface properties. For bronchoscope simulation, this requires augmenting virtual bronchoscope views generated from 3D tomographic data with patient-specific bronchoscope videos. To facilitate matching of video images to the geometry extracted from 3D tomographic data, this paper presents a new pq-space-based 2D/3D registration method for camera pose estimation in bronchoscope tracking. METHODS: The proposed technique involves the extraction of surface normals for each pixel of the video images by using a linear local shape-from-shading algorithm derived from the unique camera/lighting constraints of the endoscopes. The resultant pq-vectors are then matched to those of the 3D model by differentiation of the z-buffer. A similarity measure based on angular deviations of the pq-vectors is used to provide a robust 2D/3D registration framework. Localization of tissue deformation is considered by assessing the temporal variation of the pq-vectors between subsequent frames. RESULTS: The accuracy of the proposed method was assessed by using an electromagnetic tracker and a specially constructed airway phantom. Preliminary in vivo validation of the proposed method was performed on a matched patient bronchoscope video sequence and 3D CT data. Comparison to existing intensity-based techniques was also made. CONCLUSION: The proposed method does not involve explicit feature extraction and is relatively immune to illumination changes. The temporal variation of the pq distribution also permits the identification of localized deformation, which offers an effective way of excluding such areas from the registration process.