Endoluminal Views Research Articles

Exploring the interior of 3D endoluminal lesions in the air spaces by a novel electronic biopsy technique: A preliminary study of endoluminal colon lesions.

To explore the interior of a lesion in a 3D endoluminal view, this study investigates the application of an 'electronic biopsy' (EB) technique to computed tomographic colonography (CTC) for further differentiation and 2D image correlation of endoluminal lesions in the air spaces. A retrospective study of sixty-two various endoluminal lesions from thirty patients (13 males, 17 females; age range, 31 to 90 years) was approved by our institutional review board and evaluated. The endoluminal lesions were segmented using gray-level threshold and reconstructed into isosurfaces using a marching cube algorithm. EB allows users to interactively erode and apply grey-level mapping (GM) to the surface of the region of interest (ROI) in 3D CTC. Radiologists conducted the clinical evaluation, and the resulting data were analyzed. EB significantly improves 3D gray-level presentation for evaluating the surface and inside of endoluminal lesions over that of SR, GM or target GM (TGM) (P < 0.01) with preservation of the 3D spatial effect. Moreover, 3D to 2D image correlation were achieved in any layer of the lesion using EB as did GM/TGM on the surface. The specificity and diagnostic accuracy of EB are significantly greater than those of SR (P < 0.01). These performance can be better further with GM/TGM and reach the best with EB (specificity, 89.3-92.9%; accuracy, 95.2-96.8%). EB can be used in CTC to improve the differentiation of endoluminal lesions. EB increases 3D to 2D image correlations of the lesions on or beneath the lesion surface.

A 'Masked' Anomalous Left Coronary Artery From Pulmonary Artery: Utility of Endoluminal Views.

We present the cardiac CT images of 5-month infant with aorto-pulmonary window along with anomalous left coronary artery from pulmonary artery along with endoluminal views which help the surgeons in pre-planning of baffle orientation.

P–334 CT virtual Histerotomography: a new method for the evaluation of fallopian tube patency and pelvic organs in patients seeking pregnancy

Abstract Study question Can computerized virtual histerotomography (CT-HSG) be used for the evaluation of fallopian tube patency and pelvic organs in patients seeking pregnancy? Summary answer: CT-HSG seems to be an adequate test for the evaluation of fallopian tube patency, pelvic organs, and the uterine cavity. What is known already CT-HSG is a minimally invasive exam, which diagnoses variations in the female reproductive system, uses low radiation doses and is well tolerated by patients. It simultaneously evaluates the uterine wall, cavity and cervix, tubes, and adjacent pelvic structures. The exam enables virtual navigation, which consists of the endoluminal view of the cervical canal and uterine cavity and allows 3D reconstruction of images. The exam remains underused to assess infertility, but previous studies have shown potential and its use may be widespread. Study design, size, duration Retrospective cohort study, that included data from 317 women seeking pregnancy, between January/2019 and January/2021. The CT-HSG was indicated for infertility (90.3%) and RPL (0.9%) investigation, and for the evaluation of tubal stump in patients who were planning the tubal reversal surgery (8.8%). Patients filled out a questionnaire about their pain symptoms and data were collected from electronic records. Participants/materials, setting, methods The study analyzed patients’ clinical characteristics and image findings regarding tubes, uterine cavity, and ovaries. For the exam, a catheter was positioned in the cervix, where the contrast medium (iopromide) was injected through an infusion pump at 0.30 ml/s, for a total of 20ml. The tomographic slices were obtained at the 50th second. The CT-HSG images were interpreted by the same gynecologist and radiologist. Data were analyzed using SPSS version 20.0. Main results and the role of chance Women and partners’ mean age was 32.7 ± 5.6 and 34.6 ± 7.7 years, respectively, and women’s mean BMI was 28.4 ± 6.4 Kg/m². The pain scale was applied in 103 patients, who reported 5.4±3.2 pain scale scores at the end of the exam. Among the infertile patients 67% were nulliparous. Regarding the exam findings, most of the uterus findings were normal (72.6%). The variations found were uterine malformations (including unicornuate uterus, uterus didelphys, bicornuate uterus, septate uterus, and arcuate uterus), synechia, fibroids, endometrial polyps, adenomyosis and retractions/lateralizations that may suggest endometriosis. The tubal findings on the right/left (%) were: 65/67.5 patent horn; 18.9/17.7 obstructed tubes; 4/41 dilatation/hydrosalpinx and 9.4/9.1 with previous history of tubal ligation or salpingectomy; 1.5% of the tubal evaluation were inconclusive. Eleven from 317 patients had to repeat the exam due to occurrences during the execution (for example, improper catheter positioning, cuff fall, stenosis of the internal cervical ostium, severe pain).The 3D analysis and virtual navigation assist in the findings assessment, in addition to being simpler for the gynecologists evaluation. Limitations, reasons for caution The sample size is small due to the exam being a new technique. Patient follow-up and correlation with laparoscopy and hysteroscopy, when indicated, are under studied. Wider implications of the findings: The exam seems to be promising for assessing infertility, RPL and the tubal stump. Moreover, it may be a good option to hysterosalpingography as it seems to cause less pain and allows to evaluate the ovaries and the uterine contour, added to 3D reconstructions and to virtual uterine navigation. Trial registration number Not applicable

Virtual endoluminal aortic root views determined at coronary CT angiography - an important tool for improving anomalous coronary artery visualization and surgical planning.

Anomalous origin of the coronary arteries, though uncommon, is of great clinical concern. It can be the cause of sudden cardiac death and abnormal cardiac hemodynamics. Advances in electrocardiographically (ECG)-gated multi-detector CT have increased diagnostic accuracy in detecting anomalous origin of coronary arteries and their interarterial and intramural courses. Recent advances in multi-detector CT image processing software have allowed the creation of virtual endoluminal views of the aortic root and improved assessment of the intramural course (the length and relationship to the intercoronary commissure) of the coronary artery, which is of considerable surgical importance. We review our experience with virtual endoluminal imaging in our first 19 cases of interarterial coronary artery anomalies (17 cases of interarterial with intramural segment and 2 cases of purely interarterial course) diagnosed preoperatively and proven surgically.

Co-registration of Intravascular Ultrasound With Angiographic Imaging for Carotid Artery Disease

Intravascular ultrasound (IVUS) provides endoluminal views and cross-sectional images of carotid arteries but lacks overview of vascular territory provided by angiography. Co-registration of IVUS with angiographic images may provide the potential to navigate both imaging modalities in a synchronous manner. The objective of this study is to evaluate the feasibility and accuracy of co-registering both imaging modalities in the carotid vasculature of the neck. Fourteen patients with 15 cervical carotid artery lesions underwent angiography and subsequent treatment. In each case, an IVUS catheter was advanced to the target lesion and a reference angiography sequence was acquired. This was followed by an electrocardiography-triggered fluoroscopy sequence that was initiated upon IVUS catheter pullback. IVUS data collected during pullback were registered with fluoroscopy and evaluated for error and clinical usability. A total of 32 landmarks were identified that demonstrated reasonable agreement during IVUS-angiography co-registration. There was a mean registration error distance of 3.36 mm (SD 2.82 mm) between targets. The longitudinal extent and severity of the disease through the target segment could be easily evaluated after co-registration. Semiautomatic tracking and co-registration of angiography and IVUS is a new technology and has the potential to increase the use of IVUS in carotid disease and to proivde the opportunity to optimize procedural outcomes.

CT colonography has low sensitivity but high specificity in the detection of internal hemorrhoids.

We aimed to evaluate the diagnostic performance of computed tomography colonography (CTC) in the detection of internal hemorrhoids. Three gastroenterologists systematically reported on the presence of internal hemorrhoids in patients with incomplete colonoscopy, for whom they considered a subsequent CTC. For 44 patients with internal hemorrhoids revealed by optical colonoscopy, an age- and gender-matched cohort of 66 patients with normal findings in the rectum was selected. Endoluminal and transaxial CTC views of the rectum were evaluated for the presence of internal hemorrhoids, the anal verge prominence, asymmetry, and cushion-like appearance on a Likert scale by two experienced radiologists and two gastroenterologists. The sensitivity, specificity, and AUC for identification of internal hemorrhoids were 0.61 (95% CI, 0.53-0.68), 0.69 (95% CI, 0.63-0.75) and 0.66 (95% CI, 0.62-0.70), respectively. The radiologists showed a better specificity, the gastroenterologists a slightly better sensitivity. When only the rating "very likely" was considered as positive, the specificity rose to 0.89 (95% CI, 0.81-0.94) with a sensitivity of 0.50 (95% CI, 0.38-0.62). The interobserver agreement was fair. The best predictor of the presence of hemorrhoids was a prominent anal verge in the supine position (OR=1.789, 95% CI, 1.267-2.525). The difference between supine and prone positions in the evaluated features in patients with internal hemorrhoids was not significant. CTC has low sensitivity but high specificity in the detection of internal hemorrhoids, if the rater is confident in detecting them. Internal hemorrhoids do not substantially change their shape between prone and supine positions.

Black-blood cinematic rendering: A new method for cardiac CT intraluminal visualization

BackgroundCinematic rendering (CR) is a method of generating photorealistic 3D images from volumetric computed tomography (CT) data. In this manuscript, we describe a CR preset we have termed black-blood cinematic rendering (BBCR) that allows for detailed endoluminal views of the heart. MethodsThree recent chest CT scans were retrospectively selected as representative examples for BBCR visualization. All scans had been performed with our institution's clinical standard, post-contrast, cardiac-gated chest CT. The BBCR images were created from isotropic-voxel reconstructed volumetric data on a stand-alone workstation. ResultsThe BBCR technique was successfully utilized to demonstrate intraluminal cardiac findings in a patient with a normal left ventricle, a patient with a left ventricular mural thrombus, and a patient status-post transcatheter aortic valve replacement. ConclusionsBBCR is a new method of utilizing volumetric chest CT data in order to provide detailed images of intraluminal anatomy and pathology of the heart. Further study of this promising method is warranted.

Interobserver Variation of Colonic Polyp Measurement at Computed Tomography Colonography

BackgroundThe concept of “advanced polyps” is well accepted and is defined as polyps ≥10 mm and/or those having a villous component and/or demonstrating areas of dysplasia. Of these parameters, computed tomography colonography (CTC) can only document size. The accepted management of CTC-detected “advanced polyps” is to recommend excision if feasible, whereas the management of “intermediate” (6–9 mm) polyps is more controversial, and interval surveillance may be acceptable. Therefore, distinction between 6-9 mm and ≥10 mm is important. MethodsDatasets containing 26 polyps originally reported as between 8-12 mm in diameter were reviewed independently by 4 CTC-accredited radiologists. Observers tabulated the largest measurement for each polyp on axial, coronal, sagittal, and endoluminal views at lung-window settings. These measurements were also compared to those determined by the computer-aided detection (CAD) software. ResultsThe interobserver reliability intra-class correlation coefficient (ICC) for sagittal projection was 0.80 (“excellent” category of Hosmer and Lemeshow [2004]), 0.71 for axial (“acceptable”), 0.69 for coronal, and 0.41 for endoluminal (“unacceptable”). The largest of sagittal/axial/coronal measurement gave the best reliability with the smallest variance (ICC = 0.80; 95% CI 0.67–0.89). For 8 of 26 polyps, at least one radiologist's measurement placed the polyp in a different category compared to a colleague. For the majority of the polyps, the CAD significantly overestimated the readings compared to the largest of the manual measurements with an average difference of 1.6 mm (P < .0001 for sagittal/axial/coronal). This resulted in 33% of polyps falling into a different category—10% were lower and 23% were higher (P < .034). ConclusionIt is apparent that around the cutoff point of 10 mm between “advanced” and “intermediate” polyps, interobserver performance is variable.

The role of 3-dimensional sonography and virtual sonographic cystscopy in detection of bladder tumors

IntroductionBladder cancer is the second most common genitourinary malignancy. Recent technological advances have led to the development of virtual endoluminal internal views similar to those obtained with conventional endoscopy (virtual cystoscopy). ObjectivesTo evaluate the potential value of virtual cystoscopy in the detection and follow up of bladder tumors. Patients and methodsA total of 50 patients from Ain Shams University Hospital were studied between August 2012 and April 2014 at Ain Shams’ Radiology Department and Sonoscan Radiology Center. All patients underwent 2D-US, 3D virtual sonographic cystoscopy and conventional cystoscopy, with results compared for sensitivity and specificity in correlation with the site, size and shape of the tumor. Results3D virtual cystoscopy showed a sensitivity of 96.5%; while its specificity in identifying lesions was 85.7%; positive predictive values were 96.5%; negative predictive value were 85.7%. The sensitivity of the 2D ultrasound was 77.2%; while its specificity in identifying lesions was 57.1%; positive predictive values came at 88%; negative predictive value were 38.1%. Calculations were made taking into consideration the conventional cystoscopy “gold standard”. ConclusionAdditional to lower costs and no radiation exposure, 3D sonography appears comparable to the use of CT scans and MRI in providing virtual cystoscopy in investigating bladder cancer. Virtual sonographic cystoscopy may therefore be a useful alternative for screening and follow up of tumors, particularly if conventional cystoscopy cannot be performed. However, 3D sonography cannot replace pathological staging, and there is still a need to further improve this technology for enhanced assessment of mucosal abnormalities.

Lower Gastrointestinal Endoscopy

Since the advent of the first flexible fiberoptic sigmoidoscope in 1967, lower gastrointestinal endoscopy equipment has technologically advanced and is used for a number of diagnostic and therapeutic procedures. This review covers the definition of and indications for lower endoscopy; diagnostic and screening colonoscopy, bowel preparation for colonoscopy, special considerations for patients on anticoagulants and antiplatelet agents; endocarditis prophylaxis; general technique; diagnostic and therapeutic techniques during colonoscopy, sigmoidoscopy, anoscopy, endoscopic ultrasonography, balloon-assisted colonoscopy, and lower endoscopy training; and innovations on the horizon. Figures show room setup and patient positioning for colonoscopy; technique for insertion of a colonoscope and endoluminal view of rectum, descending colon, transverse colon, and cecum; pinch biopsy and hot biopsy forceps; snare polypectomy and endomucosal resection of a polyp using the lift and cut and suction cap techniques; Haggitt classification of tissue invasion in a pedunculated polyp; endoscopic clips and their application; self-expanding uncovered metal stents and their method of deployment; an anoscope; and rigid endorectal probes for endoscopic ultrasonography. Tables list indications for colonoscopy, recommendations for screening for colorectal cancer (average risk) from the US Preventive Services Task Force, recommendations from the US Multi-Society Task Force for surveillance after baseline colonoscopy in average-risk individuals, recommendations from the US Multi-Society Task Force for screening and surveillance in colorectal cancer (high risk), bowel preparation scales, agents for bowel preparation prior to colonoscopy, and Haggitt classification of tumor invasiveness in an adenomatous polyp. This review contains 10 highly rendered figures, 7 tables, and 60 references.

Corresponding Supine and Prone Colon Visualization Using Eigenfunction Analysis and Fold Modeling.

We present a method for registration and visualization of corresponding supine and prone virtual colonoscopy scans based on eigenfunction analysis and fold modeling. In virtual colonoscopy, CT scans are acquired with the patient in two positions, and their registration is desirable so that physicians can corroborate findings between scans. Our algorithm performs this registration efficiently through the use of Fiedler vector representation (the second eigenfunction of the Laplace-Beltrami operator). This representation is employed to first perform global registration of the two colon positions. The registration is then locally refined using the haustral folds, which are automatically segmented using the 3D level sets of the Fiedler vector. The use of Fiedler vectors and the segmented folds presents a precise way of visualizing corresponding regions across datasets and visual modalities. We present multiple methods of visualizing the results, including 2D flattened rendering and the corresponding 3D endoluminal views. The precise fold modeling is used to automatically find a suitable cut for the 2D flattening, which provides a less distorted visualization. Our approach is robust, and we demonstrate its efficiency and efficacy by showing matched views on both the 2D flattened colons and in the 3D endoluminal view. We analytically evaluate the results by measuring the distance between features on the registered colons, and we also assess our fold segmentation against 20 manually labeled datasets. We have compared our results analytically to previous methods, and have found our method to achieve superior results. We also prove the hot spots conjecture for modeling cylindrical topology using Fiedler vector representation, which allows our approach to be used for general cylindrical geometry modeling and feature extraction.

Flexible robotics with electromagnetic tracking improves safety and efficiency during in vitro endovascular navigation

One limitation of the use of robotic catheters is the lack of real-time three-dimensional (3D) localization and position updating: they are still navigated based on two-dimensional (2D) X-ray fluoroscopic projection images. Our goal was to evaluatewhether incorporating an electromagnetic (EM) sensor on a robotic catheter tip could improve endovascular navigation. Six users were tasked to navigate using a robotic catheter with incorporated EM sensors in an aortic aneurysm phantom. All users cannulated two anatomic targets (left renal artery and posterior "gate") using four visualization modes: (1) standard fluoroscopy mode (control), (2) 2D fluoroscopy mode showing real-time virtual catheter orientation from EM tracking, (3) 3D model of the phantom with anteroposterior and endoluminal view, and (4) 3D model with anteroposterior and lateral view. Standard X-ray fluoroscopy was always available. Cannulation and fluoroscopy times were noted for every mode. 3D positions of the EM tip sensor were recorded at 4Hz to establish kinematic metrics. The EM sensor-incorporated catheter navigated as expected according to all users. The success rate for cannulation was 100%. For the posterior gate target, mean cannulation times in minutes:seconds were 8:12, 4:19, 4:29, and 3:09, respectively, for modes 1, 2, 3 and 4 (P= .013), and mean fluoroscopy times were 274, 20, 29, and 2seconds, respectively (P= .001). 3D path lengths, spectral arc length, root mean dimensionless jerk, and number of submovements were significantly improved when EM tracking was used (P< .05), showing higher quality of catheter movement with EM navigation. The EM tracked robotic catheter allowed better real-time 3D orientation, facilitating navigation, with a reduction in cannulation and fluoroscopy times and improvement of motion consistency and efficiency.

An Experimental Set-Up for Navigated-Contrast-Agent and Radiation Sparing Endovascular Aortic Repair (Nav-CARS EVAR)

Over the last decade endovascular stenting of aortic aneurysm (EVAR) has been developed from single centre experiences to a standard procedure. With increasing clinical expertise and medical technology advances treatment of even complex aneurysms are feasible by endovascular methods. One integral part for the success of this minimally invasive procedure is innovative and improved vascular imaging to generate exact measurements and correct placement of stent prosthesis. One of the greatest difficulty in learning and performing this endovascular therapy is the fact that the three-dimensional vascular tree has to be overlaid with the two-dimensional angiographic scene by the vascular surgeon. We report the development of real-time navigation software, which allows a three-dimensional endoluminal view of the vascular system during an EVAR procedure in patients with infrarenal aortic aneurysm. We used the preoperative planning CT angiography for three-dimensional reconstruction of aortic anatomy by volume-rendered segmentation. At the beginning of the intervention the relevant landmarks are matched in real-time with the two-dimensional angiographic scene. During the intervention the software continously registers the position of the guide-wire or the stent. An additional 3D-screen shows the generated endoluminal view during the whole intervention in real-time. We examined the combination of hardware and software components including complex image registration and fibre optic sensor technology (fibre-bragg navigation) with integration in stent graft introducer sheaths using patient-specific vascular phantoms in an experimental setting. From a technical point of view the feasibility of fibre-Bragg navigation has been proven in our experimental setting with patient-based vascular models. Three-dimensional preoperative planning including registration and simulation of virtual angioscopy in real time are realised. The aim of the Nav-CARS-EVAR concept is reduction of contrast medium and radiation dose by a three-dimensional navigation during the EVAR procedure. To implement fibre-Bragg navigation further experimental studies are necessary to verify accuracy before clinical application.

Submilisievert ultralow-dose CT colonography using iterative reconstruction technique: a feasibility study.

Computed tomography (CT) colonography is a well established modality for the examination of symptomatic patients as well as in screening. Recent technical advances in improving image quality by iterative reconstruction contribute to the reduction of the radiation dose which is a major concern in CT imaging. To evaluate image quality of ultralow-dose submilisievert CT colonography using hybrid iterative reconstruction technique. Sixteen patients underwent contrast-enhanced CT colonography with standard protocol in supine position and ultralow-dose protocol in prone position. Ultralow-dose datasets were reconstructed with filtered back projection and an advanced hybrid iterative reconstruction technique. Two radiologists independently evaluated 96 colonic segments for image quality in the endoluminal view and axial thin sections. Colonic distension, smoothness of colonic wall and distortion of folds in the endoluminal view, sharpness of colonic wall delineation, perceived image noise, and presence of photon starvation artifact were rated on a five-point scale. Intraluminal noise expressed as standard deviation of Hounsfield density was measured in all segments. The mean radiation dose was 0.42 mSv and 5.48 mSv in prone and supine scans, respectively. All distended segments were rated evaluable in standard dose and ultralow-dose series reconstructed with the iterative reconstruction technique, whereas in 61% segments image quality was rated poor or unacceptable in ultralow-dose series where filtered back projection was used with worst ratings in the rectum and the sigmoid colon. This pilot study shows that iterative reconstruction technique is a feasible method to decrease the radiation dose from CT colonography for both positions below 1mSv. Further investigations of larger scale need to be done to clarify, whether such a low radiation dose would influence the detection of polyps.

PS218. Plasma and Patterning: The New Focus for the Development of Nanocomposite Vascular Grafts

Introduction: Over the last decade, interventional endovascular stenting of aortic aneurysm has been developed from single center experiences to a standard procedure in many countries. One integral part for the success of this minimally-invasive procedure is innovative and improved vascular imaging. One of the most difficulty in learning and performing this interventional therapy is the fact, that the three-dimensional vascular tree has to be overlain with the two-dimensional angiographic scene by the vascular surgeon. Methods: We report the development of real-time navigation software, which allows a three-dimensional endoluminal view of the vascular system during an EVARprocedure in patients with infrarenal aortic aneurysm. Even in patients with complex anatomy, the surgeon or the interventionalist achieves an accurate option of spatial perception concerning the current vascular anatomy, e.g. the position of the guide-wire. We analyzed patients with an infra-renal aortic aneurysm in which the planning CT-Scans were volumerendered. At the beginning of the intervention the relevant landmarks were matched in real-time with the twodimensional angiographic scene. During intervention the software continuously registers the position of the guidewire or the stent. An additional 3d-screen shows the generated endoluminal view during the whole intervention in real-time. Results: Our preliminary results of navigated endoluminal virtual angioscopy are promising. The “Virtual angioscope” may improve intraoperative visualization, placement of guide-wires and stents. It may reduce the amount of contrast agents and exposure to x-Rays. The prototype also offers the possibility of intervention planning and simulation which may lead to a reduced learning curve and therefore patient safety. Conclusion: Not only for pre-interventional simulation, even in training of inexperienced surgeons or interventionalists, our 3D navigation system may offer better visualization in complex endoluminal aortic procedures. Plasma and Patterning: The New Focus for the Development of Nanocomposite Vascular Grafts

Prototype of a 3D-navigation System for Interventional Therapy of Aortic Aneurysms

Introduction: Over the last decade, interventional endovascular stenting of aortic aneurysm has been developed from single center experiences to a standard procedure in many countries. One integral part for the success of this minimally-invasive procedure is innovative and improved vascular imaging. One of the most difficulty in learning and performing this interventional therapy is the fact, that the three-dimensional vascular tree has to be overlain with the two-dimensional angiographic scene by the vascular surgeon. Methods: We report the development of real-time navigation software, which allows a three-dimensional endoluminal view of the vascular system during an EVARprocedure in patients with infrarenal aortic aneurysm. Even in patients with complex anatomy, the surgeon or the interventionalist achieves an accurate option of spatial perception concerning the current vascular anatomy, e.g. the position of the guide-wire. We analyzed patients with an infra-renal aortic aneurysm in which the planning CT-Scans were volumerendered. At the beginning of the intervention the relevant landmarks were matched in real-time with the twodimensional angiographic scene. During intervention the software continuously registers the position of the guidewire or the stent. An additional 3d-screen shows the generated endoluminal view during the whole intervention in real-time. Results: Our preliminary results of navigated endoluminal virtual angioscopy are promising. The “Virtual angioscope” may improve intraoperative visualization, placement of guide-wires and stents. It may reduce the amount of contrast agents and exposure to x-Rays. The prototype also offers the possibility of intervention planning and simulation which may lead to a reduced learning curve and therefore patient safety. Conclusion: Not only for pre-interventional simulation, even in training of inexperienced surgeons or interventionalists, our 3D navigation system may offer better visualization in complex endoluminal aortic procedures. Plasma and Patterning: The New Focus for the Development of Nanocomposite Vascular Grafts

Stereotactic endovascular aortic navigation with a novel ultrasonic-based three-dimensional localization system

Endovascular aortic procedures have been developed to treat many aortic diseases effectively. However, these procedures are also becoming increasingly complex given the development of branched or fenestrated endografts. Part of the difficulty lies in the limitations of current imaging paradigms. A more intuitive, three-dimensional (3D) mode of intraoperative imaging is desirable to accommodate the future progression of endovascular techniques. This article describes a novel endovascular catheter tracking device that uses ultrasonic signals, not ultrasound imaging. The tracking device displays real-time invivo location on previously acquired 3D computed tomography (CT) images in an intuitive, endoluminal view. This system was tested in two swine and validated against fluoroscopy and by delivering stent grafts. The ultrasonic-based localization system (ULS) provides real-time location information of a modified endovascular catheter and displays this location on preoperative 3D CT images. The 9F endovascular catheter has a small ultrasonic transmitter attached to its tip to signal its location to the ULS. Subsequent endovascular deployment of an aortic stent was carried out using only the ULS to target the stent placement position in the aorta of Yorkshire swine. System accuracy was measured against concurrent angiography as well as to deployed stents in situ. We successfully displayed the endovascular catheter tip location in real time along the registered CT aortic images, providing virtual endoluminal tracking. The relative accuracy of the ULS as compared with angiography for catheter movements in the abdominal aorta was found to have a mean error less than 1 mm. The ULS coordinates tracked within the lumen of the aortic image 98% of the time, as defined by the proportion of points within one radius distance of the aortic image centerline. Finally, three aortic stents were deployed using the ULS virtual image display to locate the target position in the aorta for stent deployment. Errors between target position and actual stent position ranged from-5.0 to+7.9 mm. This study demonstrates the feasibility of virtual image-guided endovascular aortic navigation using a ULS. This provides a 3D platform for virtual navigation on preoperative CT scan images during endovascular procedures that could assist in stent deployment as well as minimize or eliminate the need for procedural ionizing radiation and iodinated contrast. Future work will focus on miniaturization and refinements in accuracy that will be required to translate this technology into clinical application in endovascular procedures.

New detachable occlusion balloon unit for transrectal natural orifice translumenal endoscopic surgery

Introduction: Transrectal natural orifice translumenal endoscopic surgery (NOTES) requires a good endoluminal view and adequate intrarectal bacterial clearance in the working area. We developed a new occlusion balloon unit with an easily detachable inflation device, which allows the surgeon a clear working area distal to the balloon. Material and methods: The effectiveness of the sealing balloon and the extent of macroscopic and histopathological injury to the bowel wall at the site of balloon placement were examined in 12 pigs. Results: The mean time to place and inflate the balloon unit was 12.0 ± 3.5 min, effective air-tightness lasted for 21.0 ± 12.0 min. There was no leakage of dye (methylene blue) past the balloon when pressure was maintained >6.70 ± 0.08 kPa (6.62–6.78 kPa). After gut irrigation, good visibility was maintained in the working area for six hours, and adequate bacterial clearance was maintained for three hours. There were no macroscopic signs of intestinal wall damage at the site of balloon placement. Histopathological examination showed only patchy mucosal damage and submucosal thrombus at the site of balloon placement. Conclusion: This newly-developed occlusion balloon unit helps to establish good visibility and adequate bacterial clearance for endoluminal surgical procedures.

Supine and Prone Colon Registration Using Quasi-Conformal Mapping

In virtual colonoscopy, CT scans are typically acquired with the patient in both supine (facing up) and prone (facing down) positions. The registration of these two scans is desirable so that the user can clarify situations or confirm polyp findings at a location in one scan with the same location in the other, thereby improving polyp detection rates and reducing false positives. However, this supine-prone registration is challenging because of the substantial distortions in the colon shape due to the patient's change in position. We present an efficient algorithm and framework for performing this registration through the use of conformal geometry to guarantee that the registration is a diffeomorphism (a one-to-one and onto mapping). The taeniae coli and colon flexures are automatically extracted for each supine and prone surface, employing the colon geometry. The two colon surfaces are then divided into several segments using the flexures, and each segment is cut along a taenia coli and conformally flattened to the rectangular domain using holomorphic differentials. The mean curvature is color encoded as texture images, from which feature points are automatically detected using graph cut segmentation, mathematic morphological operations, and principal component analysis. Corresponding feature points are found between supine and prone and are used to adjust the conformal flattening to be quasi-conformal, such that the features become aligned. We present multiple methods of visualizing our results, including 2D flattened rendering, corresponding 3D endoluminal views, and rendering of distortion measurements. We demonstrate the efficiency and efficacy of our registration method by illustrating matched views on both the 2D flattened colon images and in the 3D volume rendered colon endoluminal view. We analytically evaluate the correctness of the results by measuring the distance between features on the registered colons.

Pictorial Review of Colonic Polyp and Mass Distortion and Recognition with the CT Virtual Dissection Technique

Virtual dissection is a three-dimensional (3D) display technique for CT colonography that could potentially reduce interpretation times. With virtual dissection, the 3D model of the colon is "sliced" open along a centerline trace, rendering a 360° view of the endoluminal mucosa as a rectangular image. However, one must be familiar with several pitfalls and limitations to avoid errors in interpretation. One of the main limitations is the anatomic distortion that results. Polyp shape and colonic folds can be distorted and colonic or polyp mobility can lead to mischaracterization of polyps. Distorted folds, which frequently occur at flexures, can mimic polyps. Annular constricting masses can lead to skip areas, where the abnormality is not displayed. Various entities including diverticula and stool can mimic polyps at virtual dissection. Finally, technical errors such as an inadequate centerline trace can render a polyp occult. The purpose of this review is to demonstrate the spectrum of appearances of polyps at virtual dissection, with an emphasis on more difficult to detect polyps. In addition, 10 interactive virtual dissection quiz cases are presented along with corresponding two-dimensional and 3D endoluminal fly-through views.