Biomedical subjects

Toril A Nagelhus Hernes

Publications and source records attributed to Toril A Nagelhus Hernes.

7 recordsLinked to original sources

PubMed2006

Intraoperative navigated 3-dimensional ultrasound angiography in tumor surgery.

BACKGROUND: Avoiding damage to blood vessels is often the concern of the neurosurgeon during tumor surgery. Using angiographic image data in neuronavigation may be useful in cases where vascular anatomy is of special interest. Since 2003, we have routinely used 3D ultrasound angiography in tumor surgery, and between January 2003 and May 2005, 62 patients with different tumors have been operated using intraoperative 3D ultrasound angiography in neuronavigation. METHODS: An ultrasound-based neuronavigation system was used. In addition to 3D ultrasound tissue image data, 3D ultrasound angiography (power Doppler) image data were acquired at different stages of the operation. The value and role of navigated 3D ultrasound angiography as judged by the surgeon were recorded. RESULTS: We found that intraoperative ultrasound angiography was easy to acquire and interpret, and that image quality was sufficient for neuronavigation. In 26 of 62 cases, ultrasound angiography was found to be helpful by visualizing hidden vessels adjacent to and inside the tumor, facilitating tailored approaches and safe biopsy sampling. CONCLUSIONS: Intraoperative 3D ultrasound angiography is straightforward to use, image quality is sufficient for image guidance, and it adds valuable information about hidden vessels, increasing safety and facilitating tailored approaches. Furthermore, with updated 3D ultrasound angiography imaging, accuracy of neuronavigation may be maintained in cases of brain shift.

Biopsy↗

PubMed2004

[3-D navigation in laparoscopic surgery].

BACKGROUND: The main drawback with the laparoscopic approach is that the surgeon lacks the possibility to palpate vessels, tumours and organs during surgery. Furthermore, the laparoscope only provides a surface view of organs. There is a need for more advanced visualization that enhances the view to include information below the surface of the organs when the procedure is planned and for control and guidance during treatment. MATERIAL AND METHODS: We propose 3-D navigation technology based on preoperatively acquired MR or CT data used in combination with a laparoscopic navigation pointer. The pointer has an attached position tracker which enables the surgeon to interactively control the display of images prior to and during surgery. RESULTS: We have used this technology during treatment of four patients with adrenal tumours. Preoperative registration of images of the patients was performed within two minutes with an average accuracy of 7.1 mm. 2-D and 3-D visualizations interactively controlled by the pointer were used both for planning and for guidance of the surgical procedures. INTERPRETATION: The pointer was a useful tool in image guidance of laparoscopic surgery in the reported cases both for planning the approach in detail and for guidance. We believe abdominal 3-D image guidance using a laparoscopic navigation pointer has a large potential for improving laparoscopic surgery, especially in cases where vessels and anatomical relations might be difficult to identify using only a laparoscope. Accordingly, this new technology will increase safety and facilitate successful laparoscopic surgery.

Adrenal Gland Neoplasms↗

PubMed2003

A new method for analysis of motion of carotid plaques from RF ultrasound images.

Motion of carotid artery plaques during the cardiac cycle may contribute to plaque disruption and embolism. We have developed a computerized method that objectively analyzes such motion from a sequence of ultrasound (US) radiofrequency (RF) images. A displacement vector map is obtained by 2-D correlation of local areas in consecutive images. From this map, motion dynamics can be quantified and presented as function of time, spatial (image) coordinates or as single numbers. Correct functionality has been verified on laboratory data. Applied to patient data, the method gives temporal results that correlate well with ECG data and the calculated peak systolic velocities of typically 10 mm/s agree well with values reported in the literature. The spatial analysis demonstrates that different plaque regions may exhibit different motion patterns that may cause internal stress, leading to fissures and plaque disruption. Thus, the motion analysis method may provide new and important information about the plaque characteristics and the prospective risk of cerebrovascular events.

Aged↗

PubMed2003

Multimodal image fusion in ultrasound-based neuronavigation: improving overview and interpretation by integrating preoperative MRI with intraoperative 3D ultrasound.

OBJECTIVE: We have investigated alternative ways to integrate intraoperative 3D ultrasound images and preoperative MR images in the same 3D scene for visualizing brain shift and improving overview and interpretation in ultrasound-based neuronavigation. MATERIALS AND METHODS: A Multi-Modal Volume Visualizer (MMVV) was developed that can read data exported from the SonoWand neuronavigation system and reconstruct the spatial relationship between the volumes available at any given time during an operation, thus enabling the exploration of new ways to fuse pre- and intraoperative data for planning, guidance and therapy control. In addition, the mismatch between MRI volumes registered to the patient and intraoperative ultrasound acquired from the dura was qualified. RESULTS: The results show that image fusion of intraoperative ultrasound images in combination with preoperative MRI will make perception of available information easier by providing updated (real-time) image information and an extended overview of the operating field during surgery. This approach will assess the degree of anatomical changes during surgery and give the surgeon an understanding of how identical structures are imaged using the different imaging modalities. The present study showed that in 50% of the cases there were indications of brain shift even before the surgical procedure had started. CONCLUSIONS: We believe that image fusion between intraoperative 3D ultrasound and preoperative MRI might improve the quality of the surgical procedure and hence also improve the patient outcome.

Brain↗

PubMed2002

Accuracy evaluation of a 3D ultrasound-based neuronavigation system.

We have investigated the 3D navigation accuracy of a frameless ultrasound-based neuronavigation system (SonoWand) for surgical planning and intraoperative image guidance. In addition, we present a detailed description and review of the error sources associated with surgical neuronavigation based on preoperative MRI data and intraoperative ultrasound. A phantom with 27 precisely defined points was scanned with ultrasound by various translation and tilt movements of the ultrasound probe (180 3D scans in total), and the 27 image points in each volume were located using an automatic detection algorithm. These locations were compared to the physically measured locations of the same 27 points. The accuracy of the neuronavigation system and the effect of varying acquisition conditions were found through a thorough statistical analysis of the differences between the two point sets. The accuracy was found to be 1.40 +/- 0.45 mm (arithmetic mean) for the ultrasound-based neuronavigation system in our laboratory setting. Improper probe calibration was the major contributor to this figure. Based on our extensive data set and thorough evaluation, the accuracy found in the laboratory setting is expected to be close to the overall clinical accuracy for ultrasound-based neuronavigation. Our analysis indicates that the overall clinical accuracy may be as low as 2 mm when using intraoperative imaging to compensate for brain shift.

Humans↗

PubMed2002

Neuronavigation by intraoperative three-dimensional ultrasound: initial experience during brain tumor resection.

OBJECTIVE: Three-dimensional (3-D) ultrasound is an intraoperative imaging modality used in neuronavigation as an alternative to magnetic resonance imaging (MRI). This article summarizes 4 years of clinical experience in the use of intraoperative 3-D ultrasound integrated into neuronavigation for guidance in brain tumor resection. METHODS: Patients were selected for inclusion in the study on the basis of the size and location of their lesion. Preoperative 3-D MRI data were registered and used for planning as in other conventional neuronavigation systems. Intraoperative 3-D ultrasound images were acquired three to six times, and tumor resection was guided on the basis of these updated 3-D images. RESULTS: Intraoperative 3-D ultrasound represents a good solution to the problem of brain shift in neuronavigation because it easily provides an updated, and hence more accurate, map of the patient's true anatomy in all phases of the operation. Ultrasound makes it possible to follow the progression of the operation, and it improves the radicality of tumor resection by detecting tumor tissue that would remain if the imaging technology had not been used (in 53% of the cases). Integration of 3-D ultrasound with navigation technology solves the orientation problem experienced previously with two-dimensional ultrasound in neurosurgery. The technology makes it possible to directly compare intraoperative ultrasound and MRI data regarding visualization of the lesion. Ultrasound image quality is useful for guiding surgical procedures. CONCLUSION: Intraoperative 3-D ultrasound seems to provide a time- and cost-effective way to update high-quality 3-D maps used in neuronavigation.

Brain Neoplasms↗

PubMed2002

Brain operations guided by real-time two-dimensional ultrasound: new possibilities as a result of improved image quality.

OBJECTIVE: In 1995, a project was initiated in Trondheim, Norway, to investigate various possibilities for more frequent use of ultrasound in brain surgery. Since that time, the quality of ultrasonic images has improved considerably through technological adjustment of parameters. The objective of the present study was to explore essential clinical parameters required for the successful use of ultrasonic guidance in brain surgery. METHODS: During the study period, several surgical setups designed to optimize the use of intraoperative real-time two-dimensional ultrasonic imaging were explored. These included various positions of the ultrasound probe in relation to both the operation cavity and the lesion, as well as the position of the operation channel in relation to the gravity line. RESULTS: All lesions from the latest period (1997-2001; n = 114) were depicted well by ultrasound imaging, with the exception of two cases. High image quality and direct image guidance of the tool were maintained best throughout the operation by imaging through an intact dura and at an angle relative to a vertical operation channel. All tumor operations were performed without complications, and ultrasound imaging was found to be an important factor in the detection of remaining tumor tissue at the conclusion of surgery. For 14 low vascular tumors, the operation was guided only by ultrasound imaging. No bleeding complications occurred. A method of minimally invasive ultrasound-guided evacuation of hematomas was developed. In 19 patients, the method was found to be efficient (i.e., >90% of the hematoma was evacuated) and without complications, except for one patient who experienced rebleeding. CONCLUSION: With proper planning and surgical setup, ultrasound imaging may provide acceptable image quality for use in image-guided brain operations.

Brain↗