Biomedical subjects

Augustinus Ludwig Jacob

Publications and source records attributed to Augustinus Ludwig Jacob.

4 recordsLinked to original sources

PubMed2007

A CT database for research, development and education: concept and potential.

Both in radiology and in surgery, numerous applications are emerging that enable 3D visualization of data from various imaging modalities. In clinical practice, the patient's images are analyzed on work stations in the Radiology Department. For specific preclinical and educational applications, however, data from single patients are insufficient. Instead, similar scans from a number of individuals within a collective must be compiled. The definition of standardized acquisition procedures and archiving formats are prerequisite for subsequent analysis of multiple data sets. Focusing on bone morphology, we describe our concept of a computer database of 3D human bone models obtained from computed tomography (CT) scans. We further discuss and illustrate deployment areas ranging from prosthesis design, over virtual operation simulation up to 3D anatomy atlases. The database of 3D bone models described in this work, created and maintained by the AO Development Institute, may be accessible to research institutes on request.

Bone and Bones↗

PubMed2003

A faster method for 3D/2D medical image registration--a simulation study.

3D/2D patient-to-computed-tomography (CT) registration is a method to determine a transformation that maps two coordinate systems by comparing a projection image rendered from CT to a real projection image. Iterative variation of the CT's position between rendering steps finally leads to exact registration. Applications include exact patient positioning in radiation therapy, calibration of surgical robots, and pose estimation in computer-aided surgery. One of the problems associated with 3D/2D registration is the fact that finding a registration includes solving a minimization problem in six degrees of freedom (dof) in motion. This results in considerable time requirements since for each iteration step at least one volume rendering has to be computed. We show that by choosing an appropriate world coordinate system and by applying a 2D/2D registration method in each iteration step, the number of iterations can be grossly reduced from n6 to n5. Here, n is the number of discrete variations around a given coordinate. Depending on the configuration of the optimization algorithm, this reduces the total number of iterations necessary to at least 1/3 of it's original value. The method was implemented and extensively tested on simulated x-ray images of a tibia, a pelvis and a skull base. When using one projective image and a discrete full parameter space search for solving the optimization problem, average accuracy was found to be 1.0 +/- 0.6(degrees) and 4.1 +/- 1.9 (mm) for a registration in six parameters, and 1.0 +/- 0.7(degrees) and 4.2 +/- 1.6 (mm) when using the 5 + 1 dof method described in this paper. Time requirements were reduced by a factor 3.1. We conclude that this hardware-independent optimization of 3D/2D registration is a step towards increasing the acceptance of this promising method for a wide number of clinical applications.

Algorithms↗

PubMed2003

Stenting for pulmonary artery stenosis due to a recurrent primary leiomyosarcoma.

PURPOSE: To report stent implantation for a malignant obstruction within the pulmonary artery (PA) caused by a recurrent leiomyosarcoma in the pulmonary trunk. CASE REPORT: A 62-year-old man with a non-metastatic primary leiomyosarcoma of the right PA underwent pneumectomy of the right lung and postoperative radiotherapy in 1994. Six years later, he presented with symptoms of progressive right ventricular dysfunction. Computed tomography (CT) identified a high-grade stenosis of the left PA due to recurrent tumor within the pulmonary trunk extending into the left PA. Transthoracic ultrasound documented severe pulmonary hypertension with a high pressure gradient across the stenosis. A stent was deployed percutaneously, successfully establishing PA patency. Pressure measurements showed a significantly reduced gradient across the stented area. In follow-up, the patient reported subjective improvement of symptoms; CT scans revealed a fully patent stent. His status remained stable 11 months after stent implantation. CONCLUSIONS: PA leiomyosarcoma is a rare and highly malignant tumor. In most cases, surgery can only prolong survival for the short term. Palliative interventional PA stenting performed under local anesthesia can offer improvement in quality of life by reducing excessive pulmonary hypertension.

Constriction, Pathologic↗

PubMed2002

CT-guided percutaneous embolization of a lumbar artery maintaining a type II endoleak.

PURPOSE: To demonstrate the possibility of percutaneous embolization of a type II endoleak guided by computed tomographic (CT) fluoroscopy. CASE REPORT: A type II endoleak maintained by a hypertrophic fourth lumbar artery failed to occlude spontaneously 7 months after stent-graft deployment for endovascular repair of an infrarenal abdominal aortic aneurysm. A percutaneous procedure was performed to eliminate the endoleak using needle puncture and embolization under CT fluoroscopic guidance. The sagittal diameter of the aneurysm sac, which had remained constant after initial endovascular exclusion, shrank from 5.2 to 4.8 cm in the 3 months following embolization. CONCLUSIONS: Percutaneous embolization of lumbar branches guided by CT fluoroscopy may be an alternative to other therapies for type II endoleaks.

Aged↗