Biomedical subjects

T Lüth

Publications and source records attributed to T Lüth.

9 recordsLinked to original sources

PubMed2006

[Improved accuracy and precision of the automated shaver (navigated control) in functional endoscopic sinus surgery].

BACKGROUND: The feasibility of a navigate-controlled Shaver for the paranasal sinus surgery was proven in an initial study. Deficits showed up in the conversion of the planed cavity. Goal of this study is (1) the development and evaluation of a FESS demonstrator for the investigations to the surgical accuracy and (2) the evaluation of the resulting surgical accuracy for registration and conversion of the work space with an improved rigidity of the Shaver and a completely revised study design. METHODS: As a demonstrator for the navigate-controlled resection of a volume through the Shaver a two-piece plastic head with an anatomical head and soft tissue model was designed. The investigation of the surgical accuracy takes place with 417 measurements to 4 different fiducial markers on the demonstrator head. The measurements for the deviation of the resulting cavity from the planned volume was realised with a work space by 24 x 24 x 30 mm. The 5 walls of the cavity were seized with 80 measuring points for each level and thus altogether 2000 measured values (5 models x 5 levels x 200 points). RESULTS: The described demonstrator showed itself suitable for the close-to-application attempts to the surgical accuracy. The maximum deviation A (max) indicated position of the Shaver from the reference value amounted to 1,93 mm. The maximum average value of the exceeding of a planned cavity amounts to 1,62 mm. CONCLUSIONS: Based on these results a virtual safety passage of 2.00 mm is sufficient. The study refers the clinical serviceability of the navigate-controlled Shaver in paranasal sinus surgery.

Equipment Design↗

PubMed2006

[Clinical efficiency and the influence of human factors on ear, nose, and throat navigation systems].

BACKGROUND: The aim of this study was to evaluate the Navibase navigation system for ear, nose, and throat (ENT) surgery. A new methodology for evaluating surgical and human factors is developed. PATIENTS AND METHODS: The evaluation is based on 102 ENT surgical applications, including 89 cases of functional endoscopic sinus surgery (FESS). The evaluation of surgical and human factors was performed by seven ENT surgeons. To evaluate surgical performance, level of quality (LOQ) in the 89 cases of FESS was determined, comparing the surgeon's own impressions with those of the navigation system on a scale from 0 to 100 and further comparing them with clinical results. Intraoperative changes in surgical strategy were documented. The human factors of total confidence (trust), situation awareness, skill set requirement and workload shift were recorded as level of reliance (LOR). RESULTS: The maximum deviation amounted to 1.93 mm. Averaging the quality of information resulted in an LOQ of 63.59. Every second application of the navigation system (47.9%) led to a change in surgical strategy. Total confidence showed a positive evaluation of 3.35 points in LOR. CONCLUSION: Application-relevant information relevant to the application beyond only technical details permits comparison with other assisting systems.

Attitude of Health Personnel↗

PubMed2006

Establishing navigated control in head surgery.

Navigated Control (NC) describes an additional control for a tracked power driven instrument within a preoperatively segmented work space. In head surgery the authors first implemented NC in functional endoscopic sinus surgery (FESS). Recently the feasibility of NC for surgery on the petrosal bone is evaluated. NC in FESS and in petrosal bone surgery may reduce the risk of comorbidity and the time effort compared to the conventional surgical interventions.

Endoscopy↗

PubMed2005

[Navigated control: a new concept in computer assisted ENT-surgery].

This work conceived and evaluates a mechatronical system for ORL-surgery by example of a Shaver for Functional Endoscopic Sinus Surgery controlled by navigation. The Shaver is automatically on/off-regulated depending on the current position in relation to the planned working space. This working space is defined on the basis of the individual CT data. Within this area the Shaver reacts to the signal of the surgeon (foot pedal). If the Shaver leaves the working space, an interruption of the drive regulation to the Shaver takes place. The evaluation of the planning software based on 32 patient CT-data sets. The registration accuracy in a anatomical model was examined on 451 measurements of endonasal attached titanium screws. The conversions of the working space were evaluated at 5 different technical models. The average time for segmenting the working space was found at 4.23 minutes per case. An average registration accuracy of the Shaver of 1.08 mm resulted. The pre-defined cavity was to be cleared away without restrictions. The preoperative determined work-space was converted by 3.1 mm over all levels. The study proves the feasibility of a mechatronical assistant system by the example of the navigate-controlled Shaver in paranasal sinus surgery. Contrary to conventional CAS solutions redundancy and cognitive discharge of the surgeon are considered in this conception. We see numerous applications according to the explained principle for power-control of instruments in ORL-surgery in the future such as drilling, high frequency surgery or laser.

Feasibility Studies↗

PubMed2004

Automated laser registration in image-guided surgery: evaluation of the correlation between laser scan resolution and navigation accuracy.

Markerless patient registration based on the facial skin surface makes logistics prior to image-guided surgery much easier, as it is not necessary to place and measure registration markers. A laser scan registration of the surgical site takes the place of conventional marker-based registration. In a clinical study, the stability and accuracy of markerless patient registration was evaluated in 12 patients. Intraoral titanium markers served as targets for the infrared-pointer of the navigation system in order to check the accuracy of the markerless registration process. The correlation between laser scan resolution and navigation accuracy was checked using seven different laser scan resolutions (a cloud of 300,000 laser scan points down to 3750 laser scan points of the surgical site). The markerless patient registration was successful as long as high laser scan resolution was used (30,000 laser scan points and more): the titanium markers were detected with a mean deviation of 1.1 +/- 0.2 mm. Low resolution laser scans (6000 laser scan points of the surgical site and less) revealed inaccuracies up to 6 mm.

Humans↗

PubMed2003

[New concepts in image assisted surgery: automated patient registration based on the jaw and external ear].

OBJECTIVE: Automatic and marker less patient registration based on natural anatomical interfaces may considerably reduce the radiation load and logistical input prior to computer-assisted surgical interventions, as it is not necessary to place and measure reference markers. The present study was to find out if, apart from the facial skin, also auricles as well as the upper and lower jaw can be used as anatomical interfaces for the intraoperative registration of the patient's position. MATERIAL AND METHOD: Prior to surgical intervention the positions of 20 patients were registered by a high-resolution 3D laser scan and correlated with the preoperative CT data set. Tumors, skeletal malformations, and foreign bodies were indications for surgical intervention. Auricles as well as the upper and lower jaw were used to register the patient's positions. The accuracy of this basically marker less method was clinically evaluated through the additionally placed conventional registration markers. RESULTS AND CONCLUSION: The marker less patient registration based on natural anatomical interfaces was successful in the upper jaw (deviation: 0.8+/-0.3 mm). The tongue and mobile floor of the mouth led to geometric incongruence and inadequate laser registration in the lower jaw. As far as the auricles were concerned, high accuracy could only be achieved as long as the auricles had not been deformed during CT imaging (deviation: 1.9+/-0.9 mm). The usual CT acquisition with a conventional head support, however, led to temporary auricular deformations in more than half of the patients, which made an exact laser scan registration impossible.

Artifacts↗

PubMed2001

[Cutting speeds and success of biopsy with different punch biopsy instruments].

PURPOSE: The goal of our investigations was the verification of the relationship between the reachable cutting speed and the biopsy success for different large-core needle biopsy devices in dependence of the cutting depth as well as different kinds of tissue. METHODS: We measured the dynamic cutting properties of five large-core needle devices with moveable outer needles in air and different tissues. An incremental stripe had been attached on to the outer needle and was moved through a photooptical sensor during the cutting phase. For the valuation of the biopsy success we compared the absolute weight respectively the volume of the tissue probes as well as the relative weight in relation to the size of the sample chambers within the inner trocars. RESULTS: A clear correlation between the cutting speed, the tissue properties and the biopsy success had been registered, especially for more solid tissues. CONCLUSIONS: For a successful large-core needle biopsy a cutting speed of 8 to 12 metres per second is essential. To compensate slower needle movements high quality requirements for the surface, geometry and edge have to be fulfilled.

Animals↗

PubMed1999

[Bilateral rehabilitation with an implant-anchored orbital prosthesis].

From the aesthetic point of view, a patient can be completely rehabilitated after the loss of an eye with the insertion of an artificial eye made of glass. If the delicate structures of the eyelids have been severely damaged, however, or if the eye socket does not provide adequate retention for an eye prosthesis, rehabilitation becomes more difficult, and sometimes cannot be achieved with a cosmetically satisfactory result. In such cases, a facial prosthesis offers an alternative solution. Stable retention can be ensured with craniofacial implants. Single-sided rehabilitation by this method is quite common, but bilateral treatment is a rarity. We report on the prosthetic rehabilitation of a patient after exenteration on both sides due to retinoblastomas.

Adult↗

PubMed1999

1H and 31P NMR characterisation of a double breast coil for spectroscopic measurements and imaging.

For the first time a double turn breast coil has been described which can be used for 1H imaging, 1H spectroscopy and 31P spectroscopy. The paper describes basic technical features of the coil, coil design, B1 field/excitation field distribution for 1H and 31P, sensitivity, and feasibility for 31P spectroscopic in vivo studies. The main advantage of the double frequency tuneable coil is that 1H imaging for tumor localization and 31P spectroscopy for response control can be done without an additional repositioning of the patient.

Breast Neoplasms↗