Thesis (MScEng (Mechanical and Mechatronic Engineering))--Stellenbosch University, 2008. / A fluoroscopy-guided needle-positioning system is designed and tested as a first prototype for aiding urologists in gaining fast, accurate and repeatable kidney calyx access during a PCNL procedure while also reducing radiation exposure of the people involved. Image guidance is realized by modelling the fluoroscopic system as an adapted pinhole camera model and utilizing stereo vision principles on a stereo image pair. Calibration, distortion correction and image processing algorithms are implemented on images of a designed calibration object. Thereafter the resulting variables are used in the targeting of the calyx with the aid of a graphical user interface. The required relative translation and rotation of the needle from its current position to the target is calculated and the system is adjusted accordingly. Using digital cameras, needle placement accuracies of 2.5 mm is achieved within the calibrated volume in a simulated environment. Similar results are achieved in the surgery room environment using the fluoroscopic system. Successful needle access in two porcine kidney calyxes concluded the testing

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In percutaneous procedures, where the surgeon inserts a needle into a target in the patient, it is challenging to access the target at the rst attempt. Repeated needle insertion attempts are highly undesirable, as they lead to increased theatre time, patient haemorrhage and radiation exposure. The proposal of this thesis was to develop a low-cost system to aid surgeons with the process of positioning and orientating the needle prior to insertion. The proposed system uses a stereo pair of images produced by a standard C-arm uoroscope. By applying computer vision techniques, such as triangulation, the desired needle position and orientation are determined from the set of images. An articulated manipulator is used to position and orientate the needle. The surgeon makes selections on the images, via a graphical user interface (GUI), to indicate the desired position and orientation of the needle. Following these selections, an algorithm determines the necessary angles for the manipulator. The surgeon then positions the manipulator accordingly. Results from tests on a phantom showed the system to be repeatable and accurate to 2 mm. This is less accurate than similar, existing systems which, reported accuracies of 0:25 and 1:21 mm. However, 2 mm accuracy is considered adequate as it allows a range of percutaneous procedures to be performed such as needle biopsy, regional anaesthesia, brachytherapy and percutaneous nephrolithotomy (PCNL). Tests on both a phantom kidney and a porcine kidney indicated that the system can function in a real percutaneous procedure and with an anatomical target. The total cost to develop the prototype system was R15 000. The accuracy of the proposed system and the time to gain access to the target indicate that the system can be a bene cial aid to surgeons when performing percutaneous procedures. As minimal X-ray imaging is required, patients will also be spared excessive radiation exposure and theatre time. / AFRIKAANSE OPSOMMING: In perkutane prosedures, waar die chirurg 'n naald in 'n teiken op die pasiënt invoeg, is dit moeilik om met die eerste probeerslag toegang tot die teiken te bekom. Herhaalde pogings om die naald in te voeg is hoogs ongewens, aangesien dit tot verlengde teatertyd, bloeding by pasinte sowel as stralingsblootstelling lei. 'n Laekostestelsel is ontwikkel om chirurge by te staan met die proses om die naald voor invoeging te plaas en te oriënteer. Die stelsel gebruik 'n paar stereobeelde wat deur 'n standaard-C-arm- uoroskoop voortgebring word. Met behulp van rekenaarsigtegnieke, soos triangulasie, word die gewenste naaldposisie en -oriëntasie uit die stel beelde bepaal. 'n Geartikuleerde manipuleerder word gebruik om die naald te plaas en te oriënteer. Die chirurg voer die vereiste invoerdata deur middel van 'n gra ese gebruikerskoppelvlak (GGK) in, waarna 'n algoritme die vereiste hoeke vir die manipuleerder bepaal. Die chirurg plaas dan die manipuleerder dienooreenkomstig. Die resultate van toetse op 'n fantoom toon dat die stelsel herhaalbaar en tot op 2 mm akkuraat is. Dit is minder akkuraat as soortgelyke, bestaande stelsels, wat 'n akkuraatheid van 0:25 mm en 1:21 mm onderskeidelik aangemeld het. Tog kan akkuraatheid van 2 mm as voldoende beskou word, aangesien dit 'n verskeidenheid perkutane prosedures moontlik maak, soos naaldbiopsies, regionale anestesie, bragiterapie en perkutane nefrolitotomie (PCNL). Toetse op 'n fantoomnier dui daarop dat die stelsel wél in 'n werklike perkutane prosedure kan funksioneer. Toetse op 'n varknier toon dat die stelsel wél ook met 'n anatomiese teiken kan werk. Die totale koste om die prototipe te ontwikkel was R15 000. Die akkuraatheid van die voorgestelde stelsel en die tydsduur om toegang tot die teiken te bekom, dui daarop dat die stelsel 'n nuttige hulpmiddel kan wees vir chirurge wat perkutane prosedures uitvoer. Aangesien minimale Xstraalbeelding vereis word, sal dit pasiënte ook oormatige stralingsblootstelling en verlengde teatertyd spaar.