Philip Bao

Ultrasound-to-computer-tomography registration for image-guided laparoscopic liver surgery

BackgroundThe application of image-guided surgery (IGS) to laparoscopic liver resection and ablation is currently limited, but it would assist in intraoperative decision making regarding oncologic margins, ablation probe placement, and ablation tracking.MethodsEight spherical surface targets on a liver phantom were imaged with an optically tracked laparoscopic ultrasound (US) probe. Ten US images of each target were registered to computer tomography (CT) images of the phantoms and then mapped to the CT scans. Accuracy of the registration was assessed by comparing the distance between the predicted target location and the position obtained directly from CT.ResultsThe average localization error was 5.3 mm. The errors resulted primarily from inaccurate US probe tracking but were otherwise insensitive to the variability that arises from manually identifying targets in US and CT images.ConclusionsThe results obtained for US-to-CT registration in a phantom model suggest that further investigations into its clinical use are warranted and that other IGS technologies could be applied to laparoscopic liver surgery as well.

A prototype ultrasound-guided laparoscopic radiofrequency ablation system

BackgroundAdvanced laparoscopic procedures, particularly laparoscopic liver resection and ablation, may benefit from image-guided surgery techniques that involve interactive three-dimensional imaging and instrument tracking.MethodsA prototype system for laparoscopic ultrasound-guided radiofrequency ablation was designed and implemented. This system uses an infrared camera to track instruments and runs on a personal computer. Features of the system include spatially registered ultrasound visualization, volume reconstruction, and interactive targeting. Targeting of accuracy studies was performed by directing a tracked needle to a phantom target.ResultsUltrasound data collection and volume reconstruction can be achieved within minutes and interactively reviewed by the surgeon. Early results with phantom experiments demonstrate a targeting accuracy of 5 to 10 mm.ConclusionsThese results support the further development of this and similar image-guided surgery systems for specific laparoscopic procedures. Eventually, rigorous clinical evaluation will be necessary to prove their value.

Development of a three-dimensional freehand endorectal ultrasound system for use in rectal cancer imaging.

The initial study reporting the accuracy of an optically tracked endorectal ultrasound (TERUS) probe for the purpose of improving the staging of rectal cancer is presented here. In this work we describe the need for a more accurate ERUS system and why the incorporation of image guidance makes this goal feasible. A rectal phantom was constructed with five targets placed in positions where tumors normally occur. The locations of these targets were found using two different imaging modalities, CT and ultrasound, and the target registration error (TRE) between these two image sets was calculated. The average TRE of 33 image captures of the five targets using TERUS was 2.1mm. This is a promising outcome because the desired tumor margins for rectal cancer are on the order of centimeters. These preliminary results support the proof of concept for a TERUS system that should improve ultrasound imaging in rectal cancer.

Tracked ultrasound for laparoscopic surgery

We calibrate a tracked laparoscopic ultrasound probe for application in image-guided surgery and 3-D volume reconstruction. With a plane-mapping technique, the spatial relationship between the ultrasound beam emitted from the tip of the probe to the local coordinate system of the probe was determined by mapping it with an optically tracked pointer. A cross-wire calibration technique was also performed for comparison. The accuracy and precision of the calibrated probe was evaluated by measuring its ability to localize targets in a water bath. Target registration error depended upon probe position, varying from an average 0.88 mm for the fixed probes to 6.09 mm for a moving probe. This error can be reduced to 4.54 mm by accounting for target localization error which is the error determining the position of the probe itself. These results validate the plane-mapping calibration technique for this type of ultrasound probe, and better probe tracking is expected to reduce the overall registration error.

Resection of mesenteric inflammatory veno-occlusive disease causing ischemic colitis.

Mesenteric in.ammatory veno-occlusive disease (MIVOD) is a rare cause of mesenteric ischemia that is diagnosed by histologic examination of the operative specimen. Recurrence of symptoms occurs, but further resection of ischemic intestine is seldom required. We describe the case of MIVOD in a young patient with clinical findings of ischemic colitis. The patient experienced complete resolution of the process, thus confirming the relatively benign course of this disease following resection. This report substantiates resolution of the infiammatory process after resection, colostomy, and reanastomosis. We review the literature and make conclusions regarding the clinical management of this disease.

Ultrasound 3D Volume Reconstruction from an Optically Tracked Endorectal Ultrasound (TERUS) Probe

Endorectal Ultrasound (ERUS) is essential for the accurate staging of rectal cancer. Staging is important to the treatment of patients with rectal cancer because it will determine whether the patient receives preoperative radiotherapy for the purpose of tumor downstaging. ERUS images are intrinsically different from images taken by Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) in that ultrasound provides 2D images while CT and MRI provide 3D data sets that can be rendered into volumes and then re-sliced and viewed as 2D images in any desired orientation. This fundamental difference between ultrasound and tomographic imaging modalities creates a problem when a direct comparison between ultrasound and CT or MRI is desired. To accomplish the goal of following tumor volume over time, an accurate ultrasound volume must be constructed. By optically tracking the ERUS probe as data is collected, the intensity value for each pixel is saved and then inserted into the nearest voxel in the ERUS volume matrix. We validate the accuracy of volume reconstruction by finding the 3D coordinates of targets that are inside of the ERUS volume and comparing them to their known physical locations.

Laparoscopic Total Gastrectomy with D2 Lymphadenectomy and Side-to-Side Stapled Esophagojejunostomy

IntroductionAn optimal method has yet to be established for laparoscopic total gastrectomy with intracorporeal anastomosis.MethodsWe aim to describe a simple technique for intracorporeal anastomoses. Technique of laparoscopic total gastrectomy with side-to-side stapled intracorporeal esophagojejunostomy anastomosis and Roux-en-Y jejunojejunostomy is performed on patients with gastric malignancy in an academic community tertiary care center.ResultsThe anastomotic technique of laparoscopic total gastrectomy with side-to-side stapled esophagojejunostomy is described.ConclusionLaparoscopic total gastrectomy with D2 lymphadenectomy and side-to-side esophagojejunostomy is safe to perform and has the advantage of a wide lumen with low chance for stricture. A laparoscopic total gastrectomy with stapled side-to-side esophagojejunostomy is feasible and safe in advanced gastric cancer.

Adult Embryonal Sarcoma of the Liver: Management of a Massive Liver Tumor.

Undifferentiated embryonal sarcomas of the liver are extremely rare cases in adults. We report the case of a 30-year-old male who presented with early satiety and abdominal pain due to a massive tumor originating from the left liver and occupying the entire epigastrium. The patient underwent bland embolization in an attempt to decrease the size of the tumor. He then underwent a formal left hepatectomy with resection of liver segments 2, 3, and 4. Extrahepatic inflow control of the portal vein and hepatic artery was performed prior to parenchymal transection. No Pringle maneuver was required. Pathology analysis showed a 45 cm tumor consistent with an undifferentiated embryonal sarcoma and negative microscopic margins. The epidemiology, treatment, and prognosis of this unusual cancer presentation are reviewed.

Semi-automatic staging system for rectal cancer using spatially oriented unwrapped endorectal ultrasound

Endorectal ultrasound is currently the gold standard for the staging of rectal cancer; however, the accurate staging of the disease requires extensive training and is difficult, especially for those clinicians who do not see a large number of patients per year. Therefore, there is a need for a semi-automatic staging system to assist the clinicians in the accurate staging of rectal cancer. We believe that the unwrapping of the circular ERUS images captured by a spatially tracked ERUS system is a step in this direction. The steps by which a 2D image can be unwrapped are described thereby allowing the circular layers of the rectal wall to be displayed as flat layers stacked on top of each other. We test the unwrapping process using images from a cylindrical rectal phantom and a human rectum. The process of unwrapping endorectal ultrasound images qualitatively provides good visualization of the layers of the rectal wall and rectal tumors and supports the continual study of this novel staging system.

Ultrasound-guided ablation system for laparoscopic liver surgery

This work describes the design and implementation of a system for liver tumor ablation guided by ultrasound. Features of the system include spatially registered ultrasound visualization, ultrasound volume reconstruction, and interactive targeting. Early results with phantom experiments indicate a targeting accuracy of 5-10mm. The system serves as a foundation for further clinical studies and applications of image-guided therapy to liver procedures.