Zdzislaw Krol

Computer simulation and rapid prototyping for the reconstruction of the mandible.

Augmented-reality environments, that is, computer graphics merged with 3-dimensional representations of anatomic regions generated from imaging modalities (mainly computed tomography [CT] and magnetic resonance imaging), have their background in well-known and well-established conventional image-guided surgery, which we can describe as the “first generation of navigation.” 1-3 Although the surgeon is solely supplied with “information,” this technology significantly expands the range of the intraoperatively available information. Nevertheless, it does not provide any kind of haptic feedback, and the transfer of all the computer information is accomplished manually during the treatment of the patient. Technical progress led to the integration of rapid prototyping techniques (3-dimensional stereolithography) in image-guided surgery workflows and therefore can add “haptic” information to the computerbased visualization. Therefore we can call such approaches the “second generation of navigation.” Simulation and planning of surgical interventions by use of stereolithographic models can contribute to the optimization of treatment and can also enhance quality management in craniomaxillofacial surgery, because the specific anatomic situation of each patient can be comprehensively analyzed preoperatively. Navigation technology enables the precise transfer of the

JULIUS - An Extendable Software Framework for Surgical Planning and Image-Guided Navigation

In this paper we introduce the extendable and cross-platform software framework JULIUS, which will become public available by the end of this year. JULIUS consists of three conceptual layers and provides diverse assistance for medical visualization, surgical planning and image-guided navigation. The system features a modular and portable design and combines both pre-operative planning and intra-operative assistance within one single environment.

Navigation-Guided Harvesting of Autologous Iliac Crest Graft for Mandibular Reconstruction

Osseous reconstructions with free tissue transfer techniques in the facial region are well established and provide satisfactory results. Also, the introduction of new planning and transfer tools has simplified the surgical process for mandibular reconstruction. The reconstruction of the mandible remains very challenging: functional aspects like speech, swallowing, and chewing—with the help of dentures—have to be taken into account in the same way as esthetic aspects of the patient’s facial appearance. Although many authors report very good results using the free fibula flaps, this technology still has some disadvantages. In dentate patients especially with hemimandibulectomy, the gracile fibula bone causes an asymmetric facial appearance and inappropriate load situations between the strong healthy hemimandible and the reconstructed part. This may subsequently lead to complications. The iliac crest bone was reported to be the first choice for these patients. 1-3 For reconstructive surgical interventions with free-fibula flaps, several methods for virtual planning and transfer of the planning to the patient

Extendable application framework for medical visualization and surgical planning

This paper introduces an extendable cross-platform software framework Julius for medical visualization and surgical planning, consisting of two conceptual layers: the Julius Software Development Kit (JSDK) and the Julius Graphical User Interface (JGUI). The JSDK can be used stand-alone to speed up development of research tools. While the JGUI acts like a front end for the JSDK and offers easy handling combined with time-saving functionality to increase performance and productivity. Julius features a modular, cross-platform design and comes with a full set of components, like semi-automatic segmentation, registration, visualization and navigation.

Computer-aided osteotomy design for harvesting autologous bone grafts in reconstructive surgery

Autologous grafts serve as the standard grafting material in the treatment of maxillofacial bone tumors, traumatic defects or congenital malformations. The pre-selection of a donor site depends primarily on the morphological fit of the available bone mass and the shape of the part that has to be transplanted. To achieve sufficient incorporation of the autograft into the host bone, precise planning and simulation of the surgical intervention based on 3D CT studies is required. This paper presents a method to identify an optimal donor site by performing an optimization of appropriate similarity measures between donor region and a given transplant. At the initial stage the surgeon has to delineate the osteotomy border lines in the template CT data set and to define a set of constraints for the optimization of appropriate similarity measures between donor region and a given transplant. At the initial stage the surgeon has to delineate the osteotomy border lines in the template CT data set and to define a set of constraints for the optimization task in the donor site CT data set. The following fully automatic optimization stage delivers a set of sub-optimal and optimal donor sites for a given template. All generated solutions can be explored interactively on the computer display using an efficient graphical interface. Reconstructive operations supported by our system were performed on 28 patients. We found that the operation time can be considerably shortened by this approach.

Enabling an unimpeded surgical approach to the skull base in patients with cranial hyperostosis, exemplarily demonstrated for craniometaphyseal dysplasia

Craniometaphyseal dysplasia is an extremely rare, genetic bone-remodeling disorder. Comparable to osteopetrosis, fibrous dysplasia, and other infrequent conditions, craniometaphyseal dysplasia is characterized by progressive diffuse hyperostosis of the neuro- and viscerocranium. Affected patients present with a pathognomonic dysmorphia: macrocephalus, hypertelorism, bulky facial skeleton, and a prominent mandible. Progressive thickening and petrification of the craniofacial bones can continue throughout life, often resulting in neurological symptoms due to obstruction of the cranial nerves in the foramina and therefore immediately requiring neurosurgical interventions to avoid persistent symptoms with severe impairment of function. Treatment is largely infeasible given the lack of suitable tools to perform a craniotomy through the gross calvarial bone. In this paper, the authors present a complete process chain from the CT-based generation of an individual patients model displaying his pathology to optimized preoperative planning of the skulls shape with a thickness of about 6-7 mm. For concise verification of the surgical plan in an operating room environment, a 3D real-time navigation prototype system was utilized. To guarantee realization of the surgery in a reasonable time frame, the mechanical tools were preoperatively selected for optimizing the ablation rate in porcine and bovine bone, which were comparable to that in the patient. This process chain was developed in a modular way, so that it could be easily adopted completely or partially for other surgical indications. A 21-year-old man was treated according to this sophisticated concept. Skull bone more than 50 mm thick in some regions was reduced to physiological thickness. The patient was thus in a stage that neurosurgical interventions could be performed with a regular risk within a reasonable time of treatment.

JULIUS - An Extendable Application Framework for Medical Visualization and Surgical Planning

In this paper we introduce the extendable cross-platform software framework Julius for medical visualization and surgical planning, consisting of two conceptual layers: the Julius Software Development Kit (JSDK) and its front-end the Julius Graphical User Interface (JGUI). Julius features a modular, platform-independent design and includes a full set of components, like semi-automatic segmentation, registration, visualization and navigation.

Computer-assisted selection of donor sites for autologous grafts

A new method is proposed for a precise planning of autologous bone grafts in cranio- and maxillofacial surgery. In patients with defects of the facial skeleton, autologous bone transplants can be harvested from various donor sites in the body. The preselection of a donor site depends i.a. on the morphological fit of the available bone mass and the shape of the part that is to be transplanted. A thorough planning and simulation of the surgical intervention based on 3D CT studies leads to a geometrical description and the volumetric characterization of the bone part to be resected and transplanted. Both, an optimal fit and a minimal lesion of the donor site are guidelines in this process. We use surface similarity and voxel similarity measures in order to select the optimal donor region for an individually designed transplant.

A computer-based comparative quantitative analysis of surgical outcome of mandibular reconstructions with free fibula microvascular flaps

Abstract The free fibula osteoseptocutaneous flap is the standard for reconstruction of extensive mandibular defects. The procedure must be precise to achieve the required functional and aesthetic results. The aim of the present study was to calculate retrospectively the exact differences in surgical outcome based on preoperative and postoperative Computed Tomography data sets. Ten patients with unilateral reconstructions of the mandible with a fibula based on conventional planning were analyzed quantitatively, applying mirroring techniques with direct comparison of the theoretically optimum with the actual reconstruction. The results showed that there is a significant discrepancy between what is actually achieved and the theoretical optimum. The result of the present retrospective analysis shows that there is room for further improvement of the outcome in complex mandible reconstruction cases.

Diagnostic possibilities with multidimensional images in head and neck area using efficient registration and visualization methods

For several diseases in the head and neck area different imaging modalities are applied to the same patient.Each of these image data sets has its specific advantages and disadvantages. The combination of different methods allows to make the best use of the advantageous properties of each method while minimizing the impact of its negative aspects. Soft tissue alterations can be judged better in an MRI image while it may be unrecognizable in the relating CT. Bone tissue, on the other hand, is optimally imaged in CT. Inflammatory nuclei of the bone can be detected best by their increased signal in SPECT. Only the combination of all modalities let the physical come to an exact statement on pathological processes that involve multiple tissue structures. Several surfaces and voxel based matching functions we have tested allowed a precise merging by means of numerical optimization methods like e.g. simulated annealing without the complicated assertion of fiducial markers or the localization landmarks in 2D cross sectional slice images. The quality of the registration depends on the choice of the optimization procedure according to the complexity of the matching function landscape. Precise correlation of the multimodal head and neck area images together with its 2D and 3D presentation techniques provides a valuable tool for physicians.