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Biomedical subjects

R Kikinis

Publications and source records attributed to R Kikinis.

At least 91 records · Page 5Linked to original sources
PubMed1999

Virtual laryngoscopy.

Virtual endoscopy enables computer-generated 3-dimensional visualization of a cavity by reconstructing 2-dimensional computed tomographic or magnetic resonance data. The technique has been used experimentally to study the colon, bronchi, ears, and other structures. Here, virtual laryngoscopies were created from the cross-sectional image data of 3 patients. The cases represented a normal airway, a squamous cell carcinoma of the glottic fold, and a posterior glottic stenosis. These reconstructions included extraluminal anatomy that is not typical of current virtual endoscopic techniques. The 2-dimensional computed tomographic and magnetic resonance images of the patients underwent post-processing for 3-dimensional reconstruction. The resulting models were imported into an experimental virtual endoscopy program for 1) airway lumen generation and 2) interactive viewing. Though they could not be used for biopsy, the virtual laryngoscopies provided, in a noninvasive fashion, good simulation of endoscopy. Virtual endoscopy also gave the added benefits of the ability to assess the transmural extent of disease and view the airway distal to areas of luminal compromise. This technology may well provide clinical benefit in preoperative planning, staging, and intraprocedural guidance for head and neck disease and merits further study.

Adult↗
PubMed1998

Volumetric evaluation of the thalamus in schizophrenic male patients using magnetic resonance imaging.

BACKGROUND: The thalamus, an important subcortical brain region connecting limbic and prefrontal cortices, has a significant role in sensory and cortical processing. Although inconsistently, previous studies have demonstrated neuroanatomical abnormalities in the thalamus of schizophrenic patients. METHODS: This structural magnetic resonance imaging study, based on segmentation of contiguous coronal 1.5-mm images, compared thalamic brain volumes of 15 chronic, male schizophrenic patients with 15 normal controls matched on age, sex, handedness, and parental socioeconomic status. RESULTS: There were no significant differences between patients and controls in thalamic volumes, right or left, adjusted for total brain volume; however, there were significantly different correlations of thalamic volumes with prefrontal white matter and lateral ventricles among patients, but not among controls. Thalamic volumes among patients were also significantly correlated with bizarre behavior, hallucinations, and thought disorder. CONCLUSIONS: Findings suggest that connectivity between thalamic nuclei and prefrontal cortical areas are abnormal in chronic male schizophrenic patients. In addition, ventricular enlargement may be, in part, due to subtle reduction in thalamic volume and/or in volume of thalamocortical and corticothalamic fibers secondary to thalamic abnormalities. Finally, correlations with positive symptomatology underscore the role of the thalamus in gating or filtering of sensory information and coordination of cortical processing.

Adult↗
PubMed1998

Three-dimensional image reconstruction for low-grade glioma surgery.

Three-dimensional image reconstruction for preoperative surgical planning and intraoperative navigation for the resection of low-grade gliomas was performed in 20 patients. Thirteen of these surgeries were performed while the patient received a local anesthetic to allow for cortical mapping. Ninety percent of the patients were functionally intact postoperatively. The authors propose that the combination of the three-dimensional image reconstruction and surgical navigation, in conjunction with intraoperative cortical mapping, provides an additional means for surgeons to improve the safety and precision of the procedures.

Journal Article↗
PubMed1998

Magnetic resonance imaging shows orientation and asymmetry of white matter fiber tracts.

Apparent diffusion tensor maps of the human brain were acquired with a magnetic resonance imaging sequence (Gudbjartsson, H., Maier, S.E., Mulkern, R.V., M6rocz, I.A., Patz, S., Jolesz, F.A., Magn. Reson. Med. 36 (1996) 509-519). It was shown that the geometric nature of the apparent diffusion tensors can quantitatively characterize the tissue structure. Display of the orientation and directional uniformity of the water diffusion in the brain demonstrated most of the known major anatomical constituents of human white matter. A comparison of corresponding anatomic regions in the white matter of both hemispheres in 24 healthy volunteers revealed that fiber tracts within the anterior limb of the internal capsule have a significantly higher (P < 0.01) measure of alignment in the right hemisphere. This method offers a unique tool for the in vivo demonstration of neural connectivity in healthy and diseased brain.

Anisotropy↗
PubMed1998

Deformable modeling of facial tissue for craniofacial surgery simulation.

While deformable object modeling has been studied by computer graphics specialists for more than two decades, only a few applications in the field of surgical simulation have been developed which provide both real-time and physically realistic modeling of complex, nonlinear tissue deformations. Particularly in craniofacial surgery, the prediction of soft-tissue changes--which result from alterations in the underlying bone structure--is critical to the surgical outcome. The prediction these tissue changes and, therefore, the prognosis of the postoperative appearance of the patient, is still based on empirical studies of the relationship between bone and tissue movements: There exists no physical model which takes into account the individual patient anatomy to simulate the resulting tissue changes during craniofacial surgery. In this article we present two different deformable tissue models which are intergrated in an interactive surgical simulation test bed. Both techniques allow precise preoperative simulation of the resulting soft tissue changes during craniofacial surgery and visualization of the patient's postoperative appearance. The different deformable models are described in detail and both are applied to the same craniofacial case study. The simulation results are shown and compared with regard to the speed and accuracy of the prediction of the patient's postoperative appearance.

Computer Simulation↗
PubMed1998

Virtual pancreatoscopy of mucin-producing pancreatic tumors.

We used computer-based virtual endoscopy techniques as a novel approach to clarify the three-dimensional (3D) surgical anatomy of the pancreas and of mucin-producing pancreatic tumors. Thirteen cases (18 lesions) of mucin-producing pancreatic tumors were investigated by virtual pancreatoscopy. Virtual endoscopic images were generated with virtual endoscopy software application on UNIX workstations. We created surface-rendered virtual endoscopic images derived from a computer reconstruction of the cross-sectional magnetic resonance imaging data. Virtual endoscopy could visualize the surfaces of the pancreatic duct and the bile duct, and also demonstrated all cystic tumors. The surfaces of malignant mucin-producing pancreatic tumors were illustrated as being more irregular than those of benign lesions. The virtual endoscopic technique could demonstrate not only a surface-rendered endoscopic image of the tumors but also a 3D reconstructed image of the pancreas. The relationship to anatomic structures located outside the surfaces is continuously maintained and displayed at the same time. Virtual pancreatoscopy was useful for surgical planning of minimally invasive resection of the pancreas.

Adenocarcinoma, Mucinous↗
PubMed1998

Quantitative magnetic resonance imaging of brain development in premature and mature newborns.

Definition in the living premature infant of the anatomical and temporal characteristics of development of critical brain structures is crucial for insight into the time of greatest vulnerability of such brain structures. We used three-dimensional magnetic resonance imaging (3D MRI) and image-processing algorithms to quantitate total brain volume and total volumes of cerebral gray matter (GM), unmyelinated white matter (WM), myelinated WM, and cerebrospinal fluid (CSF) in 78 premature and mature newborns (postconceptional age, 29-41 weeks). Total brain tissue volume was shown to increase linearly at a rate of 22 ml/wk. Total GM showed a linear increase in relative intracranial volume of approximately 1.4% or 15 ml in absolute volume per week. The pronounced increase in total GM reflected primarily a fourfold increase in cortical GM. Unmyelinated WM was found to be the most prominent brain tissue class in the preterm infant younger than 36 weeks of postconceptional age. Although minimal myelinated WM was present in the preterm infant at 29 weeks, between 35 and 41 weeks an abrupt fivefold increase in absolute volume of myelinated WM was documented. Extracerebral and intraventricular CSF was readily quantitated by this technique and found to change minimally. The application of 3D MRI and tissue segmentation to the study of human infant brain from 29 to 41 weeks of postconceptional age has provided new insights into cerebral cortical development and myelination and has for the first time provided means of quantitative assessment in vivo of early human brain development.

Body Composition↗
PubMed1998

Virtual otoscopy.

Imaging techniques assist the surgeon in diagnosis of disease, surgical planning, and providing image guidance during surgery. Endoscopy has the drawback of being a minimally invasive procedure and limiting visualization to the inner surface of the lumen. Ultrasound, CT, and MR imaging show volumes of tissue beyond the lumen wall; however, their planar, two-dimensional representations require mental reconstruction of anatomic structures, which often proves difficult with the small, complex structures within the temporal bone. To improve three-dimensional visualization of the inner ear, we successfully completed a virtual model that can be displayed as a contiguous, three-dimensional luminal view, known as virtual otoscopy, which emulates traditional endoscopy. A concomitant global view and a view of the related CT slice adds a distinct advantage in the presentation and study of this complex organ. Advances in computer and software technology may overcome the time and cost factors that, at present, limit widespread use of virtual otoscopy. Overall, virtual otoscopy stands as a promising new visualization technique for elucidation of the middle ear, inner ear, and temporal bone structures.

Computer Simulation↗
PubMed1998

A simple method of scalp localization using multiplanar reconstruction of MR images.

BACKGROUND: Image-based scalp localization methods currently used are complex and not standardized. The authors have developed a simple yet accurate method for craniotomy localization using multiplanar reconstruction (MPR) algorithms. METHODS: In this method, the goal is to localize a projected point (defined as T) of the center of the lesion on the scalp. An oblique coronal plane is reformatted using a patient's magnetic resonance (MR) images with MPR algorithms to include both the center of the lesion and bilateral external auditory meati. Then the distance between T and the ipsilateral external auditory meatus or sagittal suture (defined as S) is measured along the scalp contour in the plane. The distance between the bregma and S is also measured. These distances are used for scalp localization, using a tape measure in the operating room. RESULTS: We have had successful scalp localization in six clinical cases. It took about 3 min to measure each distance on the MR console. CONCLUSION: This method for craniotomy planning using MPR algorithms is simple and sufficiently accurate.

Craniotomy↗
PubMed1998

Real-time interactive three-dimensional segmentation.

RATIONALE AND OBJECTIVES: The authors developed a real-time, interactive three-dimensional (3D) segmentation pipeline that uses relatively low-level segmentation operations and provides two-dimensional and 3D visualization through a user-friendly graphical interface. MATERIALS AND METHODS: The low-level segmentation processes were implemented on a massively parallel computer; the graphical user interface was written with a public domain software toolkit. Since their implementation 2 years ago, these segmentation tools have been applied to approximately 300 computed tomographic and magnetic resonance imaging data sets. Two typical clinical cases are presented to demonstrate their applications. RESULTS: The entire processing pipeline can be executed in a few seconds. The tools are simple to learn because they involve the use of low-level procedures and a user-friendly graphical interface with a short interactive response time. Segmentation of the bones, aorta, kidneys, and kidney cysts in case 1 could be performed in about 16 minutes. The time needed to segment each organ in case 2 ranged from about 15 minutes for the skin and brain to about 1 minute for the tumor. CONCLUSION: Satisfactory results can be obtained in a relatively short time with the real-time interactive 3D segmentation system. Operation of the system can be easily learned by a wide variety of nonspecialized users with some medical background.

Algorithms↗
PubMed1998

Volumetric object modeling for surgical simulation.

Surgical simulation has many applications in medical education, surgical training, surgical planning and intra-operative assistance. However, extending current surface-based computer graphics methods to model phenomena such as the deformation, cutting, tearing or repairing of soft tissues poses significant challenges for real-time interactions. This paper discusses the use of volumetric methods for modeling complex anatomy and tissue interactions. New techniques are introduced that use volumetric methods for modeling soft-tissue deformation and tissue cutting at interactive rates. An initial prototype for simulating arthroscopic knee surgery is described which uses volumetric models of the knee derived from 3-D magnetic resonance imaging, visual feedback via real-time volume and polygon rendering, and haptic feedback provided by a force-feedback device.

Arthroscopy↗
PubMed1998

Experimentation with a transcranial magnetic stimulation system for functional brain mapping.

We describe functional brain mapping experiments using a transcranial magnetic stimulation (TMS) device. This device, when placed on a subject's scalp, stimulates the underlying neurons by generating focused magnetic field pulses. A brain mapping is then generated by measuring responses of different motor and sensory functions to this stimulation. The key process in generating this mapping is the association of the 3-D positions and orientations of the TMS probe on the scalp to a 3-D brain reconstruction such as is feasible with a magnetic resonance image (MRI). We have developed a registration system which not only generates functional brain maps using such a device, but also provides real-time feedback to guide the technician in placing the probe at appropriate points on the head to achieve the desired map resolution. Functional areas we have mapped are the motor and visual cortex. Validation experiments focus on repeatability tests for mapping the same subjects several times. Applications of the technique include neuroanatomy research, surgical planning and guidance, treatment and disease monitoring, and therapeutic procedures.

Brain Mapping↗
PubMed1998

Three-dimensional multi-scale line filter for segmentation and visualization of curvilinear structures in medical images.

This paper describes a method for the enhancement of curvilinear structures such as vessels and bronchi in three-dimensional (3-D) medical images. A 3-D line enhancement filter is developed with the aim of discriminating line structures from other structures and recovering line structures of various widths. The 3-D line filter is based on a combination of the eigenvalues of the 3-D Hessian matrix. Multi-scale integration is formulated by taking the maximum among single-scale filter responses, and its characteristics are examined to derive criteria for the selection of parameters in the formulation. The resultant multi-scale line-filtered images provide significantly improved segmentation and visualization of curvilinear structures. The usefulness of the method is demonstrated by the segmentation and visualization of brain vessels from magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA), bronchi from a chest CT, and liver vessels (portal veins) from an abdominal CT.

Bronchography↗
PubMed1998

Visual hemifield mapping using transcranial magnetic stimulation coregistered with cortical surfaces derived from magnetic resonance images.

The perception of a visual stimulus can be inhibited by occipital transcranial magnetic stimulation. This visual suppression effect has been attributed to disruption in the cortical gray matter of primary visual cortex or in the fiber tracts leading to V1 from the thalamus. However, others have suggested that the visual suppression effect is caused by disruption in secondary visual cortex. Here the authors used a figure-eight coil, which produces a focal magnetic field, and a Quadropulse stimulator to produce visual suppression contralateral to the stimulated hemisphere in five normal volunteer subjects. The authors coregistered the stimulation sites with magnetic resonance images in these same subjects using optical digitization. The stimulation sites were mapped onto the surface of the occipital lobes in three-dimensional reconstructions of the cortical surface to show the distribution of the visual suppression effect. The results were consistent with disruption of secondary visual cortical areas.

Adult↗
PubMed1998

Computer-assisted three-dimensional reconstruction of head and neck tumors.

OBJECTIVE: Because head and neck tumors reside in a complex area, having a three-dimensional (3-D) model of the patient's unique anatomical features may assist in the delineation of pathology. The authors describe a new computer technique of 3-D anatomical reconstruction from two-dimensional computed tomography (CT) and magnetic resonance (MR) data and discuss how it represents a step forward in the continuing evolution of 3-D imaging. STUDY DESIGN: The authors selected three patients with solitary head and neck tumors and reconstructed their anatomy in a 3-D format for study. The tumors represented locations in the nose and central skull base (patient 1), temporal bone (patient 2), and neck (patient 3). MATERIALS AND METHODS: MR and CT images from the individual patients were electronically transferred to workstations in the Surgical Planning Laboratory of the authors' institution. Registration (or fusion) was carried out between the MR and CT images. The desired anatomic components underwent segmentation (identification and isolation). Assembly of the segmented images was performed and the resulting structures were integrated to produce a 3-D model. RESULTS: 3-D models of the following were constructed and displayed in an interactive format on high-capacity computer workstations: 1) a skull base sarcoma with extension into the nasopharynx and nose; 2) an acoustic neuroma with internal auditory canal involvement; and 3) a metastatic recurrence of a tongue base squamous cell carcinoma in the posterior triangle of the right side of the neck with extension to the skull base. CONCLUSION: The authors' Surgical Planning Laboratory has developed a 3-D reconstruction technique that has several new features. The models provided a very good 3-D interactive representation of the tumors and patient anatomy. The need now exists to develop this method of 3-D reconstruction of head and neck tumors for potential applications in treatment, research, and medical education.

Adult↗