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PubMedDate not supplied

Simulated femoral repositioning with three-dimensional CT.

Three-dimensional volumetric rendering of CT data has proven to be valuable in the evaluation of the hip. Although video loop animation allows review of the anatomy from all perspectives, it does not show the functional range of motion of the femur in the acetabulum. We have developed a technique termed simulated dynamic CT that gives dynamic animated three-dimensional viewing capabilities. This technique incorporates static CT data with gait and movement data to produce a sequence of dynamic images simulating range of motion. Additionally, this technique allows simulation of surgical techniques to visually anticipate the results of reduction and traction and potential limitations in subsequent hip movement. To assess the potential of this technique, two dysplastic hip patients were studied prior to reconstruction. In each case the perspective thus gained led to altered surgical management.

Child↗

PubMed1997

Tele-education: the virtual medical laboratory.

The virtual medical laboratory (VML) was conceived to provide an Internet-accessible resource, offering access for clinicians and scientists to an invaluable data archive at the institute of Laryngology and Otology, London. The Institute is home to the largest collection of temporal bone, laryngeal, skull and sinus sections in Europe. The skull and sinus collections include an extensive section consisting of animal material. These were contributions from zoos around the world. Over the last 50 years, samples have been carefully sectioned and stained by specialized technicians to produce histology slices of most regions of the head and neck. The aim of the project is to create a virtual medical laboratory, which will provide access to archived histological material as well as computerized tomography and magnetic resonance data. Central to this aim is the reconstruction of the internal anatomy of the temporal bone from two-dimensional histology slices, to create three-dimensional views that can be used for anatomical simulation and surgical training in otolaryngology. State-of-the-art three-dimensional reconstruction and rendering technology allows us to develop such a model. Computer-generated simulation could be made available to all hospitals in which otolaryngology is practised, via digital communication networks. We aim to develop core technology in our own specialty that is applicable to other fields of higher education, which have not been exposed to such modern teaching modalities. This has the potential to become an invaluable teaching resource for anatomists, surgeons and other scientists.

Computer Communication Networks↗

PubMed2006

[Simulating the outcome of ptosis and squint surgery with digital photomontage].

BACKGROUND: When being informed preoperatively about the risks and prospects of ptosis and squint surgery patients may wish to see pictures of the possible outcome. In most cases pre- and postoperative prints of patients with similar problems will be sufficient. But, to come to a decision, some patients need portrait prints of their own face modified to show the changes that could be produced by the surgery proposed. Such photo prints can be rather easily produced with modern computer and software equipment. MATERIALS AND METHODS: Portrait photos have been shot with a digital camera and have been modified in a personal computer with image processing software. RESULTS: Technique and outcome are shown with two case studies. One patient had a slight asymmetry of the upper lids after a bilateral anterior fat resection for dysthyroid exophthalmus. The second patient suffered from a considerable pseudoexotropia caused by retinopathy of prematurity. In both cases the probable result could be simulated photographically to an extent that decision making became rather easy. CONCLUSIONS: Phototechnical simulation of surgical outcome may be useful to produce better information for some patients.

Adult↗

PubMed2000

Reliability of bimaxillary surgical planning with the 3-D orthognathic surgery simulator.

Functional and esthetic dysgnathia surgery requires accurate planning and precise surgical technique. Programs that simulate such surgery have thus become increasingly important. These are useless, however, when there is no technique for reproduction of surgical planning in the patient. This can be mediated by a surgical model. The present study investigates the accuracy resulting from use of the 3-D orthognathic surgery simulator (3-D OSS) in reproducing planned patient treatment. Eighteen patients with Angle Class III malocclusions who required bimaxillary surgery were evaluated. Planning criteria depended on the orthognathically intended occlusion and the jaw position simulated in the dentofacial planner, which predicted a harmonious profile. Model planning was carried out in the 3-D OSS. The accuracy of surgical reproduction was determined by cephalometric comparison of the postoperative cephalograms and computer simulation images. There were horizontal repositioning errors of 0.61 +/- 0.45 mm to 0.78 +/- 0.52 mm at the maxillary reference points (posterior nasal spine, anterior nasal spine, point A, and incision superius). Analysis of the positioning precision attained vertically was of the same order of magnitude, with values between 0.57 +/- 0.46 mm and 0.85 +/- 0.71 mm. Less precision was achieved in the mandible. The mean horizontal variation observed at incision inferius (0.91 +/- 0.51 mm) was still within the range of values for the maxilla, but an increase in the error to 1.61 +/- 0.79 mm was registered caudally to menton. The attained position of the maxilla did not vary significantly from the planned position (P < or = 0.05). Use of the orthognathic surgery simulator allowed precise implementation of the planned surgery. The model planning proved to be very helpful in preparing difficult bimaxillary operations.

Adult↗

PubMed1991

Computer-CT planning of the electron boost in definitive breast irradiation.

Treatment planning of the electron boost in breast irradiation at this institution is performed by using information from CT scanning and from surgical clips used to define the tumor bed. A refinement of this technique, taking into account the surgical axis of approach, using computer-CT planning is now implemented. The location of the scar and the clips are digitized using a computer to define the tumor bed dimensions. With 3-D computer software a line, simulating the surgical axis and the central ray of the electron beam, is drawn between the deepest clip and the surgical scar. This beam's eye view along the surgical axis is projected onto a screen as a starting point. Appropriate gantry angle, treatment table position, beam energy, and precise shaping of the electron field borders with a 2 cm margin around the clips and the scar are determined. Simulation films comparing clinically set-up fields and computer-CT planned fields were reviewed. In only 5 of 17 patients did the clinically set-up field have adequate inclusion of the tumor bed within the treatment volume. Computer-CT planned fields ensured adequate inclusion of the tumor bed in all, including the remaining 12. In 7 patients obvious increased sparing of normal breast tissue was seen with computer-CT planned fields. This technique enables accurate placement of a shaped electron field and further refinement of electron boost treatment planning. This is especially true in situations in which the tumor bed is located at a site distant from the lumpectomy scar rather than directly beneath it and in cases where the tumor bed lies deep within the breast.

Breast Neoplasms↗

PubMed2002

Open surgery simulation.

The design of simulators for surgical training and planning poses a great number of technical challenges. Therefore the focus of systems and algorithms was mostly on the more restricted minimal invasive surgery. This paper tackles the more general problem of open surgery and presents efficient solutions to several of the main difficulties. In addition to an improved collision detection scheme for computing interactions with even heavily moving tissue, a hierarchical system for the haptic rendering has been realized in order to reach the best performance of haptic feedback. A flexible way of modeling complex surgical tools out of simple basic components is proposed. In order to achieve a realistic and at the same time fast relaxation of the tissue, the approach of explicit finite elements has been substantially improved. We are able to demonstrate realistic simulations of interactive open surgery scenarios.

Algorithms↗

PubMed2003

The middle cranial fossa approach: an anatomical study.

Hearing preservation surgery has become an option for an increasing number of patients with vestibular schwannomas due to diagnosis at an earlier stage. The middle cranial fossa approach represents one such surgical approach for resection of vestibular schwannomas with hearing preservation. We have undertaken an anatomical study of the middle cranial fossa approach to the internal auditory meatus using 20 fresh temporal bones. By simulating the surgical approach it was possible to analyze critically two of the main recognized subapproaches to the internal acoustic meatus. The results confirmed that the angle subtended by the facial nerve and "blue-lined" semicircular canal was much less than 60 degrees but equally important was the degree of individual variability. Furthermore the roof of the geniculate fossa was not infrequently dehiscent. The distance measured from the inner table of the craniotomy to the superior semicircular canal was on average 22 mm, similar to previous reports and utilized by some in their approach in this challenging surgery. From this anatomical study it appears that safe dissection of this area is facilitated by observing the more acute angle between the facial nerve and superior semicircular canal and by taking advantage of the relationship between the inner table and important landmarks.

Cranial Fossa, Middle↗

PubMed2026

Standardized visual overlays enhance laparoscopic instruction: A mixed-methods evaluation.

Effective communication during laparoscopic procedures is frequently undermined by spatial disorientation and inconsistent terminology between instructors and trainees. This study examined whether standardized visual overlays on endoscopic monitors could enhance communication and learning. We conducted a three-phase mixed-methods study: qualitative observation of 20 laparoscopic teaching cases; a randomized trial of 63 second-year medical students assigned to control, clock, or alphanumeric grid (AG) overlays during three trials of a standardized transfer task; and intraoperative implementation in 44 cases (30 AG, 14 clock) with post-case surveys and qualitative feedback. In simulation, the clock overlay produced the fastest completion times, whereas the AG yielded the lowest error scores, and both overlays outperformed the control. Intraoperatively, the AG was rated higher than the clock for communication clarity, spatial orientation, perceived operative efficiency, and trainee confidence. Standardized visual overlays, particularly the AG, appear to support intraoperative teaching by providing a shared spatial frame of reference.

Laparoscopy↗

PubMed2001

[Comparison by simulation of the efficiency of surgical blood order equation (SBOE) with that of maximum surgical blood order schedule (MSBOS)].

The maximum surgical blood order schedule (MSBOS) is used to promote efficient blood ordering practice for surgical patients. A surgical order equation (SBOE) was developed to calculate the number of units of red blood cells that should be ordered considering specific patient variables. We compared the efficiency of SBOE with that of the MSBOS by simulations. A retrospective study compared the SBOE with the MSBOS for ordering red blood cells units (MAP) in patients for six types of operations at our hospital. The SBOE was calculated as follows: SBOE (units) = mean blood loss (g)/200 - (preoperative Hb - postoperative Hb) divided by (40/body weight (kg)). The SBOE reduced the ordered units more effectively than the MSBOS. The SBOE reduces crossmatch-to-transfusion ratio (C/T ratio) from 1.2 to 1.6 but it would reduce the ordered units in statistical significance in only two of six types of operations. In conclusion, the SBOE could improve C/T ratio.

Blood Loss, Surgical↗

PubMed1997

Patient-specific anatomic models from three dimensional medical image data for clinical applications in surgery and endoscopy.

Virtual surgery and endoscopy use computer-generated volume renderings and/or models created from 3D medical image scans (CT or MRI) of individual patients. The patient's anatomy, including organs and other internal structures of interest, are then traversed in a virtual "fly-through," giving nearly the same visual impression as if the corresponding real organ was being examined intraoperatively, or as if an actual video or fiberoptic endoscopic procedure was being performed. Such virtual examinations may provide capabilities and information not possible or available in physical examinations. The potential is to provide a noninvasive computer-aided treatment plan or diagnostic screening procedure to augment or replace conventional invasive procedures. With sophisticated image processing and computational analysis, it is possible to perform realistic and useful simulations of surgical and endoscopic procedures, including "virtual dissection and resection" and "virtual biopsy." Surgical margins can be accurately assessed and differential tissue diagnoses made based upon spectral or other information contained in the patient-specific images and models.

Algorithms↗

PubMed1991

Endometriosis of the terminal ileum simulating the clinical, roentgenographic, and surgical findings in Crohn's disease.

A 38-yr-old nulliparous female presented with endometriosis of the terminal ileum which mimicked the clinical, roentgenographic, and surgical findings of Crohn's disease. The patient presented with diarrhea, right lower quadrant pain, fever, and significant weight loss. At surgery, the terminal ileum was inflamed, indurated, thickened, and angulated. Ileal endometriosis may be expected to simulate Crohn's disease, because intestinal endometriosis frequently produces local bowel inflammation, adhesions, stricture, and angulation. Ileal endometriosis should be carefully considered in the differential diagnosis of Crohn's disease in menstruating females who are nulliparous and have dysmenorrhea, dyspareunia, dyschezia, menometrorrhagia, or other perimenstrual symptoms. It is important not to mistake endometriosis for Crohn's disease because endometriosis has a different therapy.

Adult↗

PubMed1999

Learning rate for laparoscopic surgical skills on MIST VR, a virtual reality simulator: quality of human-computer interface.

Acquiring laparoscopic surgical skills involves initial learning of cognitive and motor skills followed by refinement of those skills. The successful use of a virtual reality simulator depends on the quality of the interface for the human-computer interaction and this can be determined by the initial learning rate. MIST VR, a part-task virtual reality laparoscopic simulator, provides objective assessment of psychomotor skills and can generate an overall score for performance, based upon errors made and time taken for six different tasks. This study analysed the rate of early task/instrument/computer familiarization on consecutive scores achieved by surgically experienced and naive individuals. Eleven surgeons, 18 medical students and seven non-medical personnel were tested on the simulator up to ten consecutive times, within a 2-week period. Performance data from every task and repetition were analysed to obtain individual scores of task performance. The calculation of overall score penalized errors far more heavily than total time taken, with high scores indicating poor performance. The surgeon-computer interface generated a rapid and significant early familiarization curve up to the third session on the simulator, with significant reductions in both time taken and total contact errors made. These results suggest that MIST VR represents a high quality interface. Surgeons scored consistently and significantly better than other subjects on all tasks. For surgically naive individuals, it was possible to predict the level of laparoscopic skills performance that would be attained after overcoming initial simulator learning curve, by studying their initial score. Overall scores reflected surgical experience and suggest that the simulator is measuring surgically relevant parameters. MIST VR provides a validated and much needed method for objective assessment of laparoscopic skills, for a variety of surgical disciplines.

Adult↗

PubMed2005

Experimental validation of a 3D dynamic finite-element model of a total knee replacement.

A 3D forward-dynamics model of a total knee replacement was developed using an explicit finite-element package. The model incorporated both a tibiofemoral and a patellofemoral joint and allowed full 6-DOF kinematics for both joints. Simulated quadriceps contraction was used to drive the model. For validation, a unique experimental apparatus was constructed to simulate an open-chain extension motion under quadriceps control. The ligamentous constraints of the MCL and LCL were simulated using tension springs. The kinematics of the tibia and patella were recorded along with the net forces and moments applied to the femur. Several ligament and inertial configurations were simulated. The RMS differences between the experimental data and model predictions across all simulations were excellent for both the kinematics (angles: 0.3 - 1.6 degrees, displacements: 0.1 - 0.8 mm) and kinetics (forces: 5 - 11 N, moments: 0.2 - 0.6 Nm). The validated model will be extended with physiologically realistic ligaments and utilized in surgical planning simulations.

Arthroplasty, Replacement, Knee↗

PubMedDate not supplied

Computer-aided surgical planning for implantation of hearing aids based on CT data in a VR environment.

A study was undertaken to assess the feasibility of a preoperative fitting test for an implantable hearing aid in a virtual reality (VR) environment. High-resolution spiral computed tomography (CT) of the mastoid bone was performed, and the results of a mastoidectomy were simulated with manual segmentation on a standard medical workstation. CT was also performed on a temporal bone specimen obtained at real mastoidectomy, and the bone margins were segmented automatically with threshold-based techniques. A triangulated surface representation of the bone structures including the mastoid cavity was generated. These data as well as the computer-aided design (CAD) files of the medical devices were transferred into a VR environment. The CAD components of the hearing aid were manipulated to simulate the surgical implantation procedure. Merging CAD data of an implantable hearing aid with CT data of the temporal bone in a VR environment was shown to be a feasible method of providing three-dimensional information for the presurgical determination of fit and mountability. Advances in hardware and software are expected to improve the usability of this method. Although clinical studies are needed, these results may serve as an impetus for exploring the use of low-cost, widely available VR computer equipment in a potentially broad field of clinical applications.

Cochlear Implants↗

PubMed2000

Planning and rehearsal of surgical interventions in the volume model.

Visualization of 3D medical data is routinely used in a wide range of applications. However, for the planning and rehearsal of surgical interventions more sophisticated techniques for interaction have to be developed. The realistic specification and visualization of free form cuts is needed to allow the 'look and feel' close to a real dissection. The problem here is, since these cuts are not represented by intensity changes, that the gray-level-gradient-method can not be used for the estimation of surface normals. In addition, the interactive repositioning of dissected fragments has to be simulated. We have developed an extended ray-casting algorithm for visualization of object motion in the volume model. We implemented new methods for the representation, modeling and high quality rendering (subvoxel resolution) of arbitrarily shaped cut regions within the volume model. The representation is done using a dynamic data structure. This way, all operations can easily be reversed and the original object information is preserved. The modeling of cut surfaces is done in an independent data volume where the partial-volume-effect, which is the prerequisite for the gray-level-gradient method, is calculated as it would be generated by an imaging system. This way, the localization of cut surfaces at subvoxel resolution and an accurate estimation of the surface normals is achieved. The key point here is to detect if a cut surface really truncates an object or if the object has not been affected by a cutting operation. We will present an new method, called adaptive sampling which allows to determine the situation by the generation of additional sample points (when necessary) during the ray casting process. The described techniques provides the basis for simulation of surgical interventions in the voxel-model which could not be achieved with any surface-based method. We present a system for simulation and rehearsal of otosurgical approaches, where we implemented a drill-like tool with which the student lays off the route to the operating area. The key point is to not injure structures of risk such as the facial nerve. For applications like the simulation of craniofacial surgery we developed a gradual cutting tool ("virtual scalpel").

Computer Graphics↗

PubMed1986

Muramyl dipeptide protects decomplemented mice from surgically-induced infection.

Muramyl dipeptide (MDP) is a natural product of bacterial cell-wall breakdown, which can now be produced synthetically; it is the smallest component of the mycobacterial cell wall capable of reproducing the adjuvant activities of Freund's complete adjuvant. We tested the well-documented, protective effect of MDP to increase survival in a murine model simulating surgically-induced bacteremia. The protocol involved the bacterial innoculation of control and decomplemented mice in the presence and the absence of pretreatment with MDP. Bacteremia in both the control and decomplemented groups pretreated with MDP was decreased statistically at 24 h (P less than 0.01) as compared to controls. Likewise, survival was increased significantly at 24 h (P less than 0.05), 48 h (P less than 0.001), and 72 h (P less than 0.001) using the same group comparisons. We conclude, therefore, that MDP maintains its protective effect in the absence of complement, supporting the view that the mechanism of action of MDP is complement independent.

Acetylmuramyl-Alanyl-Isoglutamine↗

PubMed1986

Acetabular fractures: three-dimensional computer tomographic imaging and interactive surgical planning.

Three-dimensional imaging can provide a valuable perceptual link between conventional radiographs and axial computed tomographic scans in the evaluation of complex acetabular fractures. With the 3D83 computer program, three-dimensional images can be generated to correlate with standard radiographic views. Unique images can also be created that offer perspectives unobtainable by conventional radiography. More sophisticated interactive techniques allow computer simulation of surgical approaches.

Acetabulum↗

PubMed2001

Dynamic 3D computer-assisted reconstruction of a metallic retrobulbar foreign body for diagnostic and surgical purposes. [Case report of orbital injury with ethmoid bone involvement].

The main goal of our dynamic 3D computer-assisted reconstruction of a metallic retrobulbar foreign body following orbital injury with ethmoid bone involvement was to use 3D-information obtained from standard computed tomography (CT) data to explore and evaluate the nasal cavity, ethmoidal sinuses, retrobulbar region, and the foreign body itself by simulated dynamic computed visualization of the human head. A foreign body, 10 x 30 mm in size, partially protruded into the posterior ethmoidal cells and partially into the orbit, causing dislocation and compression of the medial rectus muscle and inferior rectus muscle. The other muscles and the optic nerve were intact. Various steps were taken to further the ultimate diagnosis and surgery. Thin CT sections of the nasal cavity, orbit and paranasal sinuses were made on a conventional CT device at a regional medical center, CT scans were transmitted via a computer network to different locations, and special views very similar to those seen on standard endoscopy were created. Special software for 3D modeling, specially designed and modified for 3D C-FESS purposes, was used, as well as a 3D-digitizer connected to the computer and multimedia navigation through the computer during 3D C-FESS. Our approach achieves the visualization of very delicate anatomical structures within the orbit in unconventional (non-standard) sections and angles of viewing, which cannot be obtained by standard endoscopy or 2D CT scanning. Finally, virtual endoscopy (VE) or a 'computed journey' through the anatomical spaces of the paranasal sinuses and orbit substantially improves the 3D C-FESS procedure by simulating the surgical procedure prior to real surgery.

Journal Article↗