Multislice CT-image-guided endoscopic sinus surgery using an electromagnetic tracking system

Prospects and limitations of different registration modalities in electromagnetic ENT navigation

The present study examined electromagnetic tracking technology for ENT navigation. Five different registration modalities were compared and navigation accuracy was assessed. Four skull models were individually fabricated with a three-dimensional printer, based on patients' computer tomography datasets. Individual silicone masks were fitted for skin and soft tissue simulation. Five registration modalities were examined: (1) invasive marker, (2) automatic, (3) surface matching (AccuMatch), (4) anatomic landmarks, and (5) oral splint registration. Overall navigation accuracy and accuracy on selected anatomic locations were assessed by targeting 26 titanium screws previously placed over the skull. Overall navigation accuracy differed significantly between all registration modalities. The target registration error was 0.94 ± 0.06 mm (quadratic mean ± standard deviation) for the invasive marker registration, 1.41 ± 0.04 mm for the automatic registration, 1.59 ± 0.14 mm for the surface matching registration, and 5.15 ± 0.66 mm (four landmarks) and 4.37 ± 0.73 mm (five landmarks) for the anatomic landmark registration. Oral splint registration proved itself to be inapplicable to this navigation system. Invasive marker registration was superior on most selected anatomic locations. However, on the ethmoid and sphenoid sinus the automatic registration process revealed significantly lower target registration error values. Only automatic and surface registration met the accuracy requirements for noninvasive registration. Particularly, the automatic image-to-world registration reaches target registration error values on the anterior skull base which are comparable with the gold standard of invasive screw registration.

Approach to intraoperative electromagnetic navigation in orthognathic surgery: A phantom skull based trial

INTRODUCTION

Intraoperative guidance using electromagnetic navigation is an upcoming method in maxillofacial surgery. However, due to their unwieldy structures, especially the line-of-sight problem, optical navigation devices are not used for daily orthognathic surgery. Therefore, orthognathic surgery was simulated on study phantom skulls, evaluating the accuracy and handling of a new electromagnetic tracking system.

MATERIAL AND METHODS

Le-Fort I osteotomies were performed on 10 plastic skulls. Orthognathic surgical planning was done in the conventional way using plaster models. Accuracy of the gold standard, splint-based model surgery versus an electromagnetic tracking system was evaluated by measuring the actual maxillary deviation using bimaxillary splints and preoperative and postoperative cone beam computer tomography imaging. The distance of five anatomical marker points were compared pre- and postoperatively.

RESULTS

The electromagnetic tracking system was significantly more accurate in all measured parameters compared with the gold standard using bimaxillary splints (p < 0.01). The data shows a discrepancy between the model surgical plans and the actual correction of the upper jaw of 0.8 mm. Using the electromagnetic tracking, we could reduce the discrepancy of the maxillary transposition between the planned and actual orthognathic surgery to 0.3 mm on average.

DISCUSSION

The data of this preliminary study shows a high level of accuracy in surgical orthognathic performance using electromagnetic navigation, and may offer greater precision than the conventional plaster model surgery with bimaxillary splints.

CONCLUSION

This preliminary work shows great potential for the establishment of an intraoperative electromagnetic navigation system for maxillofacial surgery.

Comparison of 3% sorbitol vs psyllium fibre as oral contrast agents in MR enterography

OBJECTIVE

To compare the degree of small bowel distension achieved by 3% sorbitol, a high osmolarity solution, and a psyllium-based bulk fibre as oral contrast agents (OCAs) in MR enterography (MRE).

METHODS

This retrospective study was approved by our institutional review board. A total of 45 consecutive normal MRE examinations (sorbitol, n = 20; psyllium, n = 25) were reviewed. The patients received either 1.5 l of 3% sorbitol or 2 l of 1.6 g kg(-1) psyllium prior to imaging. Quantitative small bowel distension measurements were taken in five segments: proximal jejunum, distal jejunum, proximal ileum, distal ileum and terminal ileum by two independent radiologists. Distension in these five segments was also qualitatively graded from 0 (very poor) to 4 (excellent) by two additional independent radiologists. Statistical analysis comparing the groups and assessing agreement included intraclass coefficients, Student's t-test and Mann-Whitney U-test.

RESULTS

Small bowel distension was not significantly different in any of the five small bowel segments between the use of sorbitol and psyllium as OCAs in both the qualitative (p = 0.338-0.908) and quantitative assessments (p = 0.083-0.856). The mean bowel distension achieved was 20.1 ± 2.2 mm for sorbitol and 19.8 ± 2.5 mm for psyllium (p = 0.722). Visualization of the ileum was good or excellent in 65% of the examinations in both groups.

CONCLUSION

Sorbitol and psyllium are not significantly different at distending the small bowel and both may be used as OCAs for MRE studies.

ADVANCES IN KNOWLEDGE

This is the first study to directly compare the degree of distension in MRE between these two common, readily available and inexpensive OCAs.

[Intraoperative navigation system in endoscopic sinus surgery]

Intraoperative navigation systems have been developed to increase the safety and efficiency of endoscopic sinus surgery. The objective of this study was to compare the application and utilization of optical and electromagnetical navigation systems in our own experience during the endoscopic surgery.

MATERIAL AND METHODS

An optical-based image guidance systems (MatrixPolar Navigation System, Xion, Germany; Karl Storz Surgical Cockpit Navigation Panel Unit, Karl Storz, Germany; Stryker Navigation CartII ENT, Stryker, USA) and electromagnetic (Fusion ENT Navigation System, Medtronic, USA; Fiagon, fiagon GmbH, Germany) was used to performed 40 sinonasal and skull base surgeries. We compared the precision and accuracy of both types of systems and additional time necessary for setting up the system and real operating room time. We also analysed the convenience of navigation according to possibilities of easy instruments manipulation and fluency of navigation process.

RESULTS

The mean measured accurancy of anatomical localization at start of the surgery for optical systems was 1.62 ± 0.4mm and for electromagnetic respectively 1.79 ± 0.39 mm. The time to set up the optical system was longer than for electromagnetic one (12 vs 5 minutes). Operating room time was increased for both systems, for optical to 22 vs 8 minutes for electromagnetic one. Surgeon's working comfort during operation was better for electromagnetic systems and allowed for fluently movements with instruments.

CONCLUSIONS

Intraoperative navigation systems assist the surgeon with anatomical localization during endoscopic sinus surgery and improve its safety and efficacy. The choice of optical or electromagnetic system should be compared of effective costs and surgeon's preferences.

Imaging of pediatric patients with inflammatory bowel disease

OBJECTIVE

The goal of this review is to examine the current imaging literature and develop basic imaging guidelines for evaluation of children with inflammatory bowel disease (IBD). The three following typical clinical scenarios in the imaging evaluation of IBD are considered: patient with an initial diagnosis of suspected IBD, the goals being to determine disease extent and severity and to differentiate Crohn disease from ulcerative colitis; patient with known IBD presenting with new acute symptoms (fever, peritonitis, leukocytosis) requiring urgent evaluation; and patient with known IBD presenting with nonacute symptomatic recurrence (abdominal pain, diarrhea), the goals being to assess the efficacy of the current treatment and to evaluate the possible need for additional medical or surgical intervention.

CONCLUSION

Imaging of pediatric patients with IBD must balance considerations of diagnostic accuracy against concerns about patient exposure to ionizing radiation and tolerance of the imaging technique. The imaging modality chosen depends on the clinical presentation and expected pathologic finding.

CT enterography: review of technique and practical tips

CT enterography is a new non-invasive imaging technique that offers superior small bowel visualisation compared with standard abdomino-pelvic CT, and provides complementary diagnostic information to capsule endoscopy and MRI enterography. CT enterography is well tolerated by patients and enables accurate, efficient assessment of pathology arising from the small bowel wall or surrounding organs. This article reviews the clinical role of CT enterography, and offers practical tips for optimising technique and accurate interpretation.

Improving superficial target delineation in radiation therapy with endoscopic tracking and registration

PURPOSE

Target delineation within volumetric imaging is a critical step in the planning process of intensity modulated radiation therapy. In endoluminal cancers, endoscopy often reveals superficial areas of visible disease beyond what is seen on volumetric imaging. Quantitatively relating these findings to the volumetric imaging is prone to human error during the recall and contouring of the target. We have developed a method to improve target delineation in the radiation therapy planning process by quantitatively registering endoscopic findings contours traced on endoscopic images to volumetric imaging.

METHODS

Using electromagnetic sensors embedded in an endoscope, 2D endoscopic images were registered to computed tomography (CT) volumetric images by tracking the position and orientation of the endoscope relative to a CT image set. Regions-of-interest (ROI) in the 2D endoscopic view were delineated. A mesh created within the boundary of the ROI was projected onto the 3D image data, registering the ROI with the volumetric image. This 3D ROI was exported to clinical radiation treatment planning software. The precision and accuracy of the procedure was tested on two solid phantoms with superficial markings visible on both endoscopy and CT images. The first phantom was T-shaped tube with X-marks etched on the interior. The second phantom was an anatomically correct skull phantom with a phantom superficial lesion placed on the pharyngeal surface. Markings were contoured on the endoscope images and compared with contours delineated in the treatment planning system based on the CT images. Clinical feasibility was tested on three patients with early stage glottic cancer. Image-based rendering using manually identified landmarks was used to improve the registration.

RESULTS

Using the T-shaped phantom with X-markings, the 2D to 3D registration accuracy was 1.5-3.5 mm, depending on the endoscope position relative to the markings. Intraobserver standard variation was 0.5 mm. Rotational accuracy was within 2°. Using the skull phantom, registration accuracy was assessed by calculating the average surface minimum distance between the endoscopy and treatment planning contours. The average surface distance was 0.92 mm with 93% of all points in the 2D-endoscopy ROI within 1.5 mm of any point within the ROI contoured in the treatment planning software. This accuracy is limited by the CT imaging resolution and the electromagnetic (EM) sensor accuracy. The clinical testing demonstrated that endoscopic contouring is feasible. With registration based on em tracking only, accuracy was 5.6-8.4 mm. Image-based registration reduced this error to less than 3.5 mm and enabled endoscopic contouring in all cases.

CONCLUSIONS

Registration of contours generated on 2D endoscopic images to 3D planning space is feasible, with accuracy smaller than typical set-up margins. Used in addition to standard 3D contouring methods in radiation planning, the technology may improve gross tumour volume (GTV) delineation for superficial tumors in luminal sites that are only visible in endoscopy.

Mural attenuation in normal small bowel and active inflammatory Crohn’s disease on CT enterography: location, absolute attenuation, relative attenuation, and the effect of wall thickness. AJR Am J Roentgenol. 2009;192:417-423. [PMID: 19155404 DOI: 10.2214/AJR.08.1267]

OBJECTIVE

The purpose of our study was to measure relative and absolute wall attenuations and wall thickness in normal small bowel on contrast-enhanced CT enterography and to study the efficacy of relative attenuation, absolute attenuation, and wall thickness in distinguishing normal from active inflammatory Crohn's disease of the terminal ileum.

MATERIALS AND METHODS

Using a case-control study design, we reviewed 630 CT enterography examinations, of which 191 were normal and 36 had active inflammatory Crohn's disease in the terminal ileum. In healthy individuals, wall thickness and attenuation in distended and collapsed loops were measured in the duodenum and four abdominal quadrants. Wall thickness and attenuation were also measured in the terminal ileum. All measurements of intraarterial attenuation were taken at the same slice level. In the examinations of patients with Crohn's disease, only terminal ileum wall thickness and attenuation as well as arterial attenuation at the same slice level were measured. Normal segments were compared with a linear model. Terminal ileum data were fit to a multivariate logistic regression model.

RESULTS

Relative attenuation and absolute attenuation in the normal distended and collapsed duodenum and left upper quadrant were significantly greater than in all other segments (p < 0.001 and < 0.048 for relative attenuation and p < 0.001 and < 0.032 for absolute attenuation, respectively). Relative attenuation and wall thickness models and absolute attenuation and wall thickness models discriminated normal from active terminal ileum Crohn's disease significantly better than the same measurements without wall thickness (p = 0.017 and 0.001, respectively). When the bowel wall is > 3 mm, a relative attenuation cutoff of 0.5 is 89% sensitive and 81% specific.

CONCLUSION

In normal small bowel, when wall measurement is taken into account, the duodenum and jejunum have a greater relative attenuation and absolute attenuation than other segments. Relative attenuation and absolute attenuation with wall thickness models discriminate normal from active terminal ileum Crohn's disease better than the same measurements without wall thickness.

Cost-effectiveness and patient tolerance of low-attenuation oral contrast material: milk versus VoLumen

OBJECTIVE

The purpose of our study was to prospectively compare the cost, effectiveness, and patient tolerance of milk and VoLumen, a 0.1% barium suspension, in patients undergoing abdominal and pelvic CT with oral and i.v. contrast media.

SUBJECTS AND METHODS

Two hundred fifteen consecutive outpatients were randomly assigned to receive either whole milk (n = 115) or VoLumen (n = 100). Results were independently reviewed by two radiologists who were blinded to the oral contrast agent used. Degree of bowel distention was qualitatively scored on a 4-point scale, and bowel wall visibility was graded qualitatively on a yes-or-no basis. A questionnaire regarding oral contrast tolerability was provided to each patient. Cost comparison of the two agents was performed.

RESULTS

No statistically significant differences were seen between whole milk and VoLumen with respect to degree of bowel distention and mural visualization for all segments of bowel studied (p > 0.05 for both reviewers). Significantly more patients ranked milk as pleasant in taste compared with VoLumen (p < 0.0001). More patients preferred milk compared with VoLumen (p < 0.0001). Milk was better tolerated than VoLumen, with fewer abdominal side effects, including abdominal discomfort (p = 0.019), cramping (p = 0.019), nausea (p = 0.016), and diarrhea (p = 0.0002). The cost per patient for VoLumen is $18 compared with $1.48 for milk.

CONCLUSION

Whole milk is comparable to VoLumen with respect to bowel distention and bowel wall visualization and has a lower cost, better patient acceptance, and fewer adverse symptoms. Milk is a cost-effective alternative to VoLumen as a low-attenuation oral contrast agent.

A novel technique for localization of small pulmonary nodules

BACKGROUND

To show the safety and accuracy of a new marking technique using an image-guided technique for preoperative localization of a small pulmonary nodule.

METHODS

CT data of a patient with a peripheral pulmonary nodule < 20 mm were transmitted to a surgical navigation system (StealthStation Treon Treatment Guidance System; Medtronic; Louisville, KY). To match preoperative CT image data to the physical space occupied by the patient during surgery, five to six superficial skin fiducials were used for registration. A 16-gauge needle attached by a positioning sensor was advanced into or immediately adjacent to the nodule for injection of methylene blue under guidance of the StealthStation system. Then the lesion marked by the methylene was thoracoscopically resected.

RESULTS

Seventeen patients (12 men and 5 women; mean age, 51.3 years) underwent this procedure, and all the nodules were identified due to the precise location of the probe. They were resected with sufficient margins. There were no surgical complications. The average time of registration was 4.8 +/- 0.9 min (+/- SD). Registration error was on average 2.7 +/- 0.2 mm.

CONCLUSIONS

Image-guided navigation is useful, accurate, and safe in the localization of small peripheral lung lesions.

Experimental image-guided endoscopic pituitary surgery: a useful learning model

OBJECTIVES

The purpose of this study, which combined image guidance and endocscopic pituitary surgery (EPS), was to test its practicability as a learning tool to acquire the necessary skills in an experimental setting.

METHODS

Ten cadaver-heads were explored using a standard endoscopic transsphenoidal surgical technique combined with the InstaTrak 3500 (GE Medical Systems, Lawrence, MA, USA) image guidance system. The time taken for the experimental setup and the optic-radiologic correlations of topographic landmarks were recorded and photographed.

RESULTS

The average time for setting up the system was 11.9 min+/-2.0, which included head fixation, headset positioning, registration, calibration and verification of the system. With the guidance of the navigation system, the ostium, sellar floor and adjacent structures encountered during EPS could be identified easily and were reflected on the 3D-CT images accurately.

CONCLUSION

The experimental model validated the practicability of image guidance combined with EPS. The non-invasive interactive computer-assisted CT-guided navigational system facilitated the surgical procedure by providing precise spatial relationship between instrument position and adjacent structures. This combination is a useful teaching and learning tool in the cadaver and in patients will be useful, particularly for complex cases and redo-surgery.

Endoscopic pituitary surgery with and without image guidance: an experimental comparison

BACKGROUND

The combination of image guidance and endoscopy is the newest trend in pituitary surgery. To assess the impact of image guidance on EPS, we measured and calculated the accuracy of the system and compared some critical surgical steps with and without image guidance under experimental conditions in terms of surgical time and precision.

METHODS

Twenty cadaver heads were explored by standard endoscopic transsphenoidal surgical technique. Optic-radiologic correlations of topographic landmarks were photographed, and the system accuracy and actual visual accuracy were recorded. Some important anatomical parameters were measured in surgical field and on navigation system, and the differences were calculated and analyzed. Some critical surgical steps were recorded and compared between with and without image guidance.

RESULTS

The system accuracy (root mean square), calculated by the computer automatically, showed a mean value of 0.28 +/- 0.06 mm. In some cases, there was a small discrepancy between the visible position of the pointer and its counterpart on the navigation system; we coined this actual visual accuracy. The average value was 1.53 +/- 0.49 mm. The maximum difference between the measurements from the navigation system and from their actual visual counterparts was less than 7%. With and without image guidance, in normal anatomical conditioning, there was no statistically significant difference between the duration of ostium sphenoidale exposure and sellar window creation; however, in anatomical variations, the surgical time was shown to be significantly shorter when navigation was used.

CONCLUSION

We have demonstrated in this experimental setting that the electromagnetic tracking image guidance possesses a high accuracy at millimetric level and therefore provides precise localization and orientation in EPS. With the assistance of neuronavigation system, it is advantageous not only in saving operating time, but also, more importantly, in enhancing the orientation, thus, rendering surgeries safer and more efficient. During the in vivo pituitary surgery, EPS with image guidance can provide accurate and reliable stereoinformation to achieve better results with lesser risks, particularly in complex cases or in reoperations, even in the hands of experienced surgeons.

Using an image-guided navigation system for localization of small pulmonary nodules before thoracoscopic surgery

BACKGROUND

Video-assisted thoracic surgery (VATS) provides a minimally invasive means to resect small pulmonary nodules (SPN). However, thoracoscopy has limits in the detection of small nodules, which are invisible and/or impalpable during surgery. Methods to localize such lesions, including methylene blue injection or the introduction of a hookwire under the guidance of computed tomography (CT), have some limitations. We are developing a new technique using image-guided navigation system for localization of small pulmonary nodules before thoracoscopic surgery.

METHODS

Four pigs underwent spiral-computed tomography (CT) scanning after they were given percutaneously created pulmonary lesions. The CT data were transmitted to a StealthStation navigation system, and with the help of the probe the lesions were located and resected under thoracoscopy.

RESULTS

A total of 20 lesions were created. Nodules were located at an average distance of 15.6 mm from the pleural surface. All the lesions were successfully localized, and biopsy specimens revealed successful resection of target material.

CONCLUSION

This method can provide appropriate guidance to small pulmonary nodules and prove effective in immediately facilitating subsequent thoracoscopic resection.

Advances in imaging of the paranasal sinuses

Imaging technology has played a significant role in the diagnosis and management of sinonasal disorders. Plain sinus films are almost exclusively replaced by CT in the work-up for inflammatory sinus disease. MRI provides complementary information to CT in cases of sinonasal and skull-base neoplasms. The evolution of endoscopic surgical techniques for the paranasal sinuses and skull base is made possible by the parallel advancement of imaging technologies. Recent advances that are currently in clinical use have included multidetector row CT scanners and computer image-guidance systems for surgery. Three-dimensional CT angiography, image-guided CT-MR fusion, and intraoperative image-guidance are new techniques that are currently being evaluated. As imaging technology continues to advance, so does the capability to treat diseases beyond the sinuses and skull base with minimally invasive, endoscopic approaches.

Diagnostic value of CT enteroclysis compared with conventional enteroclysis in patients with Crohn's disease

OBJECTIVE

The objective of our study was to assess the diagnostic value of CT enteroclysis compared with conventional enteroclysis in patients with Crohn's disease.

SUBJECTS AND METHODS

Fifty consecutive patients (26 women, 24 men; mean age, 36.3 years; age range, 18-52 years) with histologically proven Crohn's disease underwent CT enteroclysis and conventional enteroclysis (median time interval, 21.7 days) during a symptomatic stage of their disease. Both techniques were compared with regard to diagnostic yield in assessing the presence and extent of disease. Imaging findings were compared with surgery, follow-up examinations, or both.

RESULTS

CT enteroclysis and conventional enteroclysis were successfully performed in all 50 patients. Crohn's disease-associated radiographic changes were found in 44 patients (88%) using CT enteroclysis and in 42 patients (84%) using conventional enteroclysis. Significantly more Crohn's disease-associated abnormalities were diagnosed with CT enteroclysis than with enteroclysis (p < 0.01). Minimal inflammatory changes of the mucosa were diagnosed in 44 patients (88%) using CT enteroclysis and in 42 patients (84%) using enteroclysis. Both imaging methods depicted stenotic bowel segments in 34 patients (68%), and prestenotic dilatation was diagnosed in 20 patients (40%) with CT enteroclysis and in 15 (30%) with enteroclysis. Fistulas were found in 18 patients (36%) with CT enteroclysis and in eight (16%) with enteroclysis (p < 0.01). Skip lesions could be seen in 17 (34%) and three patients (6%), respectively (p < 0.01). Conglomeration of bowel loops tumors was diagnosed with CT enteroclysis in 13 patients (26%) and in three patients (6%) using conventional enteroclysis (p < 0.01). Only CT enteroclysis depicted abscesses in eight patients (16%) (p < 0.01).

CONCLUSION

CT enteroclysis proved to be significantly superior to conventional enteroclysis in depicting Crohn's disease-associated intra- and extramural abnormalities. CT enteroclysis is the imaging method of choice and should replace enteroclysis in patients with Crohn's disease.

Computer-aided surgery of the paranasal sinuses and skull base

Endoscopic sinus surgery is one of the most common surgical procedures in otolaryngology. However, the location of the orbit and intracranial contents in close proximity to the paranasal sinuses makes endoscopic sinus surgery potentially hazardous. Otolaryngologists have employed computer-aided surgery, or image-guided surgery, over the past two decades to enhance surgeon confidence, allow more thorough surgical dissections and possibly reduce the complication rate of endoscopic sinus surgery. Computer-aided surgery utilizes preoperative imaging to provide real-time localization of surgical instruments in the surgical field. Although computer-aided surgery originated in the neurosurgical realm, otolaryngologists soon appreciated that this technology could assist in identifying critical orbital or intracranial structures surrounding the paranasal sinuses, and potentially aid in decreasing complications. In this article, the history of image-guidance systems and their application to surgery of the paranasal sinuses and skull base will be reviewed. The components of computer-aided surgery systems and the currently available technologies for surgical instrument tracking are discussed, as well as the advantages and disadvantages of each of the tracking technologies. In addition, issues relating to the accuracy of image-guidance systems are examined. A number of institutional series noting surgeon experience with computer-aided surgery in the domain of paranasal sinus surgery are reviewed. Furthermore, the authors evaluate the utility of image-guidance technology beyond the paranasal sinuses and skull base, such as its use in surgery of the pituitary gland and pterygopalatine fossa, research and resident education. Finally, potential future applications of computer-aided surgery technology are discussed.

Application of soft tissue modelling to image-guided surgery

The deformation of soft tissue compromises the accuracy of image-guided surgery based on preoperative images, and restricts its applicability to surgery on or near bony structures. One way to overcome these limitations is to combine biomechanical models with sparse intraoperative data, in order to realistically warp the preoperative image to match the surgical situation. We detail the process of biomechanical modelling in the context of image-guided surgery. We focus in particular on the finite element method, which is shown to be a promising approach, and review the constitutive relationships which have been suggested for representing tissue during surgery. Appropriate intraoperative measurements are required to constrain the deformation, and we discuss the potential of the modalities which have been applied to this task. This technology is on the verge of transition into clinical practice, where it promises to increase the guidance accuracy and facilitate less invasive interventions. We describe here how soft tissue modelling techniques have been applied to image-guided surgery applications.

Stability of miniature electromagnetic tracking systems

This study aims at a comparative evaluation of two recently introduced electromagnetic tracking systems under reproducible simulated operating-room (OR) conditions: the recently launched Medtronic StealthStation, Treon-EM and the NDI Aurora. We investigate if and to what extent these systems provide improved performance and stability in the presence of surgical instruments as possible sources of distortions compared with earlier reports on electromagnetic tracking technology. To investigate possible distortions under pseudo-realistic OR conditions, a large Langenbeck hook, a dental drill with its handle and an ultrasonic (US) scanhead are fixed on a special measurement rack at variable distances from the navigation sensor. The position measurements made by the Treon-EM were least affected by the presence of the instruments. The lengths of the mean deviation vectors were 0.21 mm for the Langenbeck hook, 0.23 mm for the drill with handle and 0.56 mm for the US scanhead. The Aurora was influenced by the three sources of distortion to a higher degree. A mean deviation vector of 1.44 mm length was observed in the vicinity of the Langenbeck hook, 0.53 mm length with the drill and 2.37 mm due to the US scanhead. The maximum of the root mean squared error (RMSE) for all coordinates in the presence of the Langenbeck hook was 0.3 mm for the Treon and 2.1 mm for the Aurora; the drill caused a maximum RMSE of 0.2 mm with the Treon and 1.2 mm with the Aurora. In the presence of the US scanhead, the maximum RMSE was 1.4 mm for the Treon and 5.1 mm for the Aurora. The new generation of electromagnetic tracking systems has significantly improved compared to common systems that were available in the middle of the 1990s and has reached a high level of technical development. We conclude that, in general, both systems are suitable for routine clinical application.

Small bowel hydro-MR imaging for optimized ileocecal distension in Crohn's disease: Should an additional rectal enema filling be performed?

PURPOSE

To assess the impact of an additional rectal enema filling in small bowel hydro-MRI in patients with Crohn's disease.

MATERIALS AND METHODS

A total of 40 patients with known Crohn's disease were analyzed retrospectively: 20 patients only ingested an oral contrast agent (group A), the other 20 subjects obtained an additional rectal water enema (group B). For small bowel distension, a solution containing 0.2% locust bean gum (LBG) and 2.5% mannitol was used. In all patients, a breathhold contrast-enhanced T1w three-dimensional volumetric interpolated breathhold examination (VIBE) sequence was acquired. Comparative analysis was based on image quality and bowel distension as well as signal-to-noise ratio (SNR) measurements. MR findings were compared with those of conventional colonoscopy, as available (N = 25).

RESULTS

The terminal ileum and rectum showed a significantly higher distension following the rectal administration of water. Furthermore, fewer artifacts were seen within group B. This resulted in a higher reader confidence for the diagnosis of bowel disease, not only in the colon, but also in the ileocecal region. Diagnostic accuracy in diagnosing inflammation of the terminal ileum was 100% in group B; in the nonenema group there were three false-negative diagnoses of terminal ileitis.

CONCLUSION

Our data show that the additional administration of a rectal enema is useful in small bowel MRI for the visualization of the terminal ileum. The additional time needed for the enema administration was minimal, and small and large bowel pathologies could be diagnosed with high accuracy. Thus, we suggest that a rectal enema in small bowel MR imaging be considered.

Laparoscopic lymph node dissection for gastric cancer with intraoperative navigation using three-dimensional angio computed tomography images reconstructed as laparoscopic view

BACKGROUND

Laparoscopic extended lymph node dissection for gastric cancer is difficult to perform because it requires dissection with preservation of vessels. Therefore, an intraoperative navigation system for the angioarchitecture would be helpful. Recent enhanced volume-rendering computed tomography (CT) can produce clear intraluminal three-dimensional (3D) images. This advanced radiological technology can provide 3D angiographic images reconstructed in the same view as would be observed from a laparoscope inserted into the abdominal cavity. We report our experience with laparoscopic gastrectomy with radical lymph node dissection using this advanced radiological technology.

METHODS

3D CT angiographic images from the celiac axis to the proper hepatic artery were reconstructed in two ways preoperatively. The first was only 3D angiographic images that were reconstructed as the laparoscopic view (LapView 3D CT angiography). The second was LapView 3D CT angiography with images of the body of the pancreas, which was more useful for intraoperative navigation in comprehensing anatomy. Two monitors were placed over the shoulder of the patient during surgery. One monitor, which was controlled by the image mixer, projected the laparoscopic images with picture in picture of 3D CT angiographic images. The surgeon performed the surgery with reference to this monitor during lymph node dissection.

RESULTS

3D angiographic CT clearly showed all vessels of interest in laparoscopic lymph node dissection for gastric cancer in 10 cases. The anatomy of vessels appeared as if looking beyond visible surface. LapView 3D CT angiography was useful for laparoscopic navigation surgery.