Vessel target location estimation during the TIPS procedure

Creation of a Transjugular Intrahepatic Portosystemic Shunt (TIPS) requires passage of a needle toward a moving target that is only seen transiently by x-ray prior to needle passage. Intraoperative, 3D target localization would facilitate target access and improve the safety of the procedure. The clinical assumption is that patients undergoing the TIPS procedure possess rigid, cirrhotic livers that undergo only intraoperative translation without significant deformation or rotation. Based upon this assumption, we hypothesize that the position of any unseen, 3D target point within the liver can be determined intraoperatively by precalculation of the relative positions of the target point to a different 3D point that can be tracked intraoperatively. This paper examines this hypothesis using intraoperatively acquired, biplane, x-ray images of 7 patients. In 6, we tracked the effects of cardiac and respiratory motion, and in 3 the effects of needle pressure. Methods involved reconstruction of 3D vessel bifurcation and other trackable intrahepatic points from biplane angiograms, measurement of liver deformation by examining changing distances between these 3D points over time, and comparison of expected to actual displacements of these points with respect to a fixed reference point in the liver. We conclude that, for the rigid livers associated with patients undergoing TIPS, that there is less intraoperative deformation than previously reported by other groups addressing healthy liver deformation, and that the location of an unseen target can be predicted within 3 mm accuracy

Emergency Pericardiocentesis in Children

Cardiac tamponade is a life-threatening condition characterized by compression of the heart due to pericardial accumulation of different types of fluid and requires prompt diagnosis and immediate therapeutic intervention. Echocardiography is the most useful imaging technique to diagnose the cardiac tamponade and to evaluate the size, location, and hemodynamic impact of the pericardial effusion. Emergency pericardiocentesis is the procedure used for the aspiration of the fluid from the pericardial space in patients with significant pericardial effusion which determines hemodynamic compromise (cardiac tamponade). Emergency pericardiocentesis in children is performed under local anesthesia and is echocardiographic-guided. The first step of echocardiographic-guided pericardiocentesis is to assess the dimension and distribution of the pericardial fluid and the optimal trajectory of the needle in order to efficiently evacuate the pericardial fluid. The transducer is situated 3–5 cm from the parasternal border and the trajectory of the needle is established by the angle of the transducer. The needle is positioned between the xiphoid process and the left costal cartilages and is advanced, while a continuous aspiration is performed. It is important to avoid the neighboring vital organs (heart, liver, lung, internal mammary artery, and the intercostal vascular bundle). Complications which can occur are as follows: dysrhythmias, puncture of coronary artery or mammary artery, hemothorax, pneumothorax, pneumopericardium, and hepatic injury

Focal Spot, Spring 1995

https://digitalcommons.wustl.edu/focal_spot_archives/1069/thumbnail.jp

High frequency jet ventilation (HFJV) in clinical practice

Background: Surgery often requires general anaesthesia. During general anaesthesia, a ventilator is often used to secure the breathing of the patient. This is preferably done by mimicking normal ventilation. Conventional ventilation causes the lung to inflate and deflate which in turn makes the diaphragm move up and down in the craniocaudal direction. Therefore, all organs adjacent to the diaphragm will be affected by these breathing-related motions. During liver tumour ablation, stereotactic technique can be used. During stereotactic technique, radiological images are used to optimise needle placement in three dimensions, to reach the target tumour. It is of great importance that the target tumour does not move, ensuring that the tissue destruction is limited to the tumour and avoiding injury of healthy surrounding tissue. To meet the demand of target organ immobilisation, high frequency jet ventilation (HFJV) has become an interesting option. This method uses small tidal volumes at high frequencies that highly differ from normal physiological respiration in humans, contrary to conventional ventilation during surgery. HFJV has been used for decades especially for ventilation during airway procedures. To ventilate the patient while minimising abdominal organ movement and thereby improving surgical conditions during stereotactic ablative procedures is a novel way of using the benefits of HFJV. Aim: This doctoral thesis studied the feasibility and safety of using high frequency jet ventilation for the specific purpose of liver immobilisation during stereotactic ablation procedures. The aim of Study I was to study gas exchange during HFJV during stereotactic ablation of liver tumours. In Study II, post-operative hypertension and its relation to liver tumour ablation techniques and ventilation methods were studied. In Study III the formation of atelectasis during HFJV was studied. In Study IV the levels of carbon dioxide (CO2) were studied in two different groups randomised to different sizes of the endotracheal tube in which the jet-catheter was placed during HFJV in liver tumour ablation. In Study IV continuous transcutaneous carbon dioxide (TcCO2) monitoring was compared to intermittent measurement of arterial carbon dioxide (PaCO2). Methods: Study I is a prospective, observational study. Blood gas analysis was performed every 15 minutes for the first 45 minutes of HFJV in 24 patients undergoing liver tumour ablation. Study II is a retrospective, observational study. Medical chart records were collected and analysed for early post-operative hypertension for 134 patients receiving either HFJV or conventional ventilation (CV) and various ablation methods, microwave ablation (MWA) or irreversible electroporation (IRE). Study III is a prospective, observational study. CT-images over the lower part of the lung were taken in 25 patients every 15 minutes during the first 45 minutes of HFJV. The images were analysed for atelectasis formation during HFJV using the MatLab software program. Study IV is a randomised, prospective study. PaCO2 was measured during the first 45 minutes after initiation of HFJV in patients randomised to endotracheal tube (ETT) inner diameter (ID) 8 or 9 mm. TcCO2 was also measured during the same period and compared to gold standard PaCO2. Airway pause pressures, peak pressures and signs of intubation injuries were also studied. Results: In Study I blood gas analyses showed that none of the 24 patients experienced hypoxemia during the first 45 minutes of high frequency jet ventilation. A statistically significant rise in arterial carbon dioxide (PaCO2) was seen at all time points during HFJV compared to baseline. A further statistically significant rise in PaCO2 was seen during HFJV compared to T=0 at T=30 (p=0.006) and T=45 (p=0.003). A corresponding statistically significant decrease in pH was seen compared to baseline at T=15 (p=0.03) from a mean value of 7.44 to 7.31. A further small drop in pH was seen over time but with no significance between time points. During early recovery in the post anaesthesia care unit, PaCO2 and pH resumed spontaneous to baseline values. All lactate values were within normal range except for one value in one patient during recovery that was slightly raised to 2.3 mmol L-1. Study II showed that hypertension was common in post-operative care after liver tumour ablation. Patients receiving MWA under HFJV had the highest proportion of having at least one episode of severe hypertension (SAP >180 mmHg) when compared to patients receiving IRE under HFJV and MWA under CV. Multiple regression analysis showed increased odds for post-operative hypertension when MWA was used compared to IRE and when HFJV was used compared to CV. Study III showed that the formation of atelectasis increased over time during HFJV during the 45 minutes studied, from 5.6% to 8.1% of the total lung area. The increase in atelectasis was significant at T=30 (p=0.002) and T=45 (p=0.024). The area of normal ventilation was however unchanged. In a subgroup analysis with patients with a BMI<30, no significant difference in the amount of atelectasis could be seen between the time points. In Study IV PaCO2 increased in both groups, with ETT ID 8 and 9 mm, but no statistically significant difference between the two groups was seen (p=0.06). TcCO2 was measured and compared to PaCO2. A Bland-Altman plot and an ICC analysis showed a good correlation between the two methods. Conclusions: The overall result of this thesis indicates that high frequency jet ventilation is feasible and safe during stereotactic ablation of upper abdominal organs for up to 45 minutes. There is a risk of hypertensive events in the early recovery, following liver tumour ablation when MWA and HFJV are used. Atelectasis increases but the proportion of normally ventilated lung is preserved. PaCO2 increases but is rapidly reversed during recovery. An ETT ID 8 mm can be used in male patients for shorter procedures, regarding PaCO2. TcCO2 is a feasible technique when following the changes in carbon dioxide although blood gas analysis should be considered in patients in need for haemodynamic monitoring and risk of carbon dioxide retention

A Framework for Tumor Localization in Robot-Assisted Minimally Invasive Surgery

Manual palpation of tissue is frequently used in open surgery, e.g., for localization of tumors and buried vessels and for tissue characterization. The overall objective of this work is to explore how tissue palpation can be performed in Robot-Assisted Minimally Invasive Surgery (RAMIS) using laparoscopic instruments conventionally used in RAMIS. This thesis presents a framework where a surgical tool is moved teleoperatively in a manner analogous to the repetitive pressing motion of a finger during manual palpation. We interpret the changes in parameters due to this motion such as the applied force and the resulting indentation depth to accurately determine the variation in tissue stiffness. This approach requires the sensorization of the laparoscopic tool for force sensing. In our work, we have used a da Vinci needle driver which has been sensorized in our lab at CSTAR for force sensing using Fiber Bragg Grating (FBG). A computer vision algorithm has been developed for 3D surgical tool-tip tracking using the da Vinci \u27s stereo endoscope. This enables us to measure changes in surface indentation resulting from pressing the needle driver on the tissue. The proposed palpation framework is based on the hypothesis that the indentation depth is inversely proportional to the tissue stiffness when a constant pressing force is applied. This was validated in a telemanipulated setup using the da Vinci surgical system with a phantom in which artificial tumors were embedded to represent areas of different stiffnesses. The region with high stiffness representing tumor and region with low stiffness representing healthy tissue showed an average indentation depth change of 5.19 mm and 10.09 mm respectively while maintaining a maximum force of 8N during robot-assisted palpation. These indentation depth variations were then distinguished using the k-means clustering algorithm to classify groups of low and high stiffnesses. The results were presented in a colour-coded map. The unique feature of this framework is its use of a conventional laparoscopic tool and minimal re-design of the existing da Vinci surgical setup. Additional work includes a vision-based algorithm for tracking the motion of the tissue surface such as that of the lung resulting from respiratory and cardiac motion. The extracted motion information was analyzed to characterize the lung tissue stiffness based on the lateral strain variations as the surface inflates and deflates

International Student’s Survival Guide to Clinical Practice

Clinical patient work is an essential part of learning for all dentistry students. However, the beginning of clinical work can be stressful. In addition to learning new skills, students must also learn how the teaching clinic works and what are its customs and practices. To make the transition from pre-clinical studies to clinical studies easier, Piia Uusitalo and Katariina Havukainen wrote a second cycle degree thesis called Kandin selviytymisopas klinikkaan in 2015. It was written only in Finnish with Finnish speaking undergraduates in mind, but there was also demand for a similar guide for exchange students as part of an exchange study reform for dentistry students. The first part of translation work included interviews with exchange students either when they arrived to Turku or at the end of their exchange period. Interview questions handled everything from their wishes and hopes to experiences and criticism depending on which stage of their exchange period interviews were conducted. The second part included translation work and modifications that were done according to the wishes, problems and proposals that interviewees had mentioned during interviews. Lastly, the English guide was updated with instructions for new materials and procedures and Finnish Current Care Guidelines (Käypä hoito) for periodontology. There is also a new step-by-step guide on aseptics in both the teaching clinic and the Oral and Maxillofacial Unit of Turku University Hospital. This guide will hopefully help exchange students to get accustomed to teaching clinic’s activities faster than before and make their stay at the Institute of Dentistry fruitful and enjoyable

Local anesthesia and tooth extraction

УЧЕБНО-МЕТОДИЧЕСКИЕ ПОСОБИЯРОТОВОЙ ПОЛОСТИ ХИРУРГИЧЕСКИЕ ОПЕРАЦИИАНЕСТЕЗИЯ В СТОМАТОЛОГИИАНЕСТЕЗИЯ МЕСТНАЯЗУБОВ ЭКСТРАКЦИЯИНОСТРАННЫЕ СТУДЕНТЫСТОМАТОЛОГИЯПособие содержит разделы дисциплины "Челюстно-лицевая хирургия и хирургическая стоматология" по местной анестезии и операции удаления зуба

Navigation system based in motion tracking sensor for percutaneous renal access

Tese de Doutoramento em Engenharia BiomédicaMinimally-invasive kidney interventions are daily performed to diagnose and treat several renal diseases. Percutaneous renal access (PRA) is an essential but challenging stage for most of these procedures, since its outcome is directly linked to the physician’s ability to precisely visualize and reach the anatomical target. Nowadays, PRA is always guided with medical imaging assistance, most frequently using X-ray based imaging (e.g. fluoroscopy). Thus, radiation on the surgical theater represents a major risk to the medical team, where its exclusion from PRA has a direct impact diminishing the dose exposure on both patients and physicians. To solve the referred problems this thesis aims to develop a new hardware/software framework to intuitively and safely guide the surgeon during PRA planning and puncturing. In terms of surgical planning, a set of methodologies were developed to increase the certainty of reaching a specific target inside the kidney. The most relevant abdominal structures for PRA were automatically clustered into different 3D volumes. For that, primitive volumes were merged as a local optimization problem using the minimum description length principle and image statistical properties. A multi-volume Ray Cast method was then used to highlight each segmented volume. Results show that it is possible to detect all abdominal structures surrounding the kidney, with the ability to correctly estimate a virtual trajectory. Concerning the percutaneous puncturing stage, either an electromagnetic or optical solution were developed and tested in multiple in vitro, in vivo and ex vivo trials. The optical tracking solution aids in establishing the desired puncture site and choosing the best virtual puncture trajectory. However, this system required a line of sight to different optical markers placed at the needle base, limiting the accuracy when tracking inside the human body. Results show that the needle tip can deflect from its initial straight line trajectory with an error higher than 3 mm. Moreover, a complex registration procedure and initial setup is needed. On the other hand, a real-time electromagnetic tracking was developed. Hereto, a catheter was inserted trans-urethrally towards the renal target. This catheter has a position and orientation electromagnetic sensor on its tip that function as a real-time target locator. Then, a needle integrating a similar sensor is used. From the data provided by both sensors, one computes a virtual puncture trajectory, which is displayed in a 3D visualization software. In vivo tests showed a median renal and ureteral puncture times of 19 and 51 seconds, respectively (range 14 to 45 and 45 to 67 seconds). Such results represent a puncture time improvement between 75% and 85% when comparing to state of the art methods. 3D sound and vibrotactile feedback were also developed to provide additional information about the needle orientation. By using these kind of feedback, it was verified that the surgeon tends to follow a virtual puncture trajectory with a reduced amount of deviations from the ideal trajectory, being able to anticipate any movement even without looking to a monitor. Best results show that 3D sound sources were correctly identified 79.2 ± 8.1% of times with an average angulation error of 10.4º degrees. Vibration sources were accurately identified 91.1 ± 3.6% of times with an average angulation error of 8.0º degrees. Additionally to the EMT framework, three circular ultrasound transducers were built with a needle working channel. One explored different manufacture fabrication setups in terms of the piezoelectric materials, transducer construction, single vs. multi array configurations, backing and matching material design. The A-scan signals retrieved from each transducer were filtered and processed to automatically detect reflected echoes and to alert the surgeon when undesirable anatomical structures are in between the puncture path. The transducers were mapped in a water tank and tested in a study involving 45 phantoms. Results showed that the beam cross-sectional area oscillates around the ceramics radius and it was possible to automatically detect echo signals in phantoms with length higher than 80 mm. Hereupon, it is expected that the introduction of the proposed system on the PRA procedure, will allow to guide the surgeon through the optimal path towards the precise kidney target, increasing surgeon’s confidence and reducing complications (e.g. organ perforation) during PRA. Moreover, the developed framework has the potential to make the PRA free of radiation for both patient and surgeon and to broad the use of PRA to less specialized surgeons.Intervenções renais minimamente invasivas são realizadas diariamente para o tratamento e diagnóstico de várias doenças renais. O acesso renal percutâneo (ARP) é uma etapa essencial e desafiante na maior parte destes procedimentos. O seu resultado encontra-se diretamente relacionado com a capacidade do cirurgião visualizar e atingir com precisão o alvo anatómico. Hoje em dia, o ARP é sempre guiado com recurso a sistemas imagiológicos, na maior parte das vezes baseados em raios-X (p.e. a fluoroscopia). A radiação destes sistemas nas salas cirúrgicas representa um grande risco para a equipa médica, aonde a sua remoção levará a um impacto direto na diminuição da dose exposta aos pacientes e cirurgiões. De modo a resolver os problemas existentes, esta tese tem como objetivo o desenvolvimento de uma framework de hardware/software que permita, de forma intuitiva e segura, guiar o cirurgião durante o planeamento e punção do ARP. Em termos de planeamento, foi desenvolvido um conjunto de metodologias de modo a aumentar a eficácia com que o alvo anatómico é alcançado. As estruturas abdominais mais relevantes para o procedimento de ARP, foram automaticamente agrupadas em volumes 3D, através de um problema de optimização global com base no princípio de “minimum description length” e propriedades estatísticas da imagem. Por fim, um procedimento de Ray Cast, com múltiplas funções de transferência, foi utilizado para enfatizar as estruturas segmentadas. Os resultados mostram que é possível detetar todas as estruturas abdominais envolventes ao rim, com a capacidade para estimar corretamente uma trajetória virtual. No que diz respeito à fase de punção percutânea, foram testadas duas soluções de deteção de movimento (ótica e eletromagnética) em múltiplos ensaios in vitro, in vivo e ex vivo. A solução baseada em sensores óticos ajudou no cálculo do melhor ponto de punção e na definição da melhor trajetória a seguir. Contudo, este sistema necessita de uma linha de visão com diferentes marcadores óticos acoplados à base da agulha, limitando a precisão com que a agulha é detetada no interior do corpo humano. Os resultados indicam que a agulha pode sofrer deflexões à medida que vai sendo inserida, com erros superiores a 3 mm. Por outro lado, foi desenvolvida e testada uma solução com base em sensores eletromagnéticos. Para tal, um cateter que integra um sensor de posição e orientação na sua ponta, foi colocado por via trans-uretral junto do alvo renal. De seguida, uma agulha, integrando um sensor semelhante, é utilizada para a punção percutânea. A partir da diferença espacial de ambos os sensores, é possível gerar uma trajetória de punção virtual. A mediana do tempo necessário para puncionar o rim e ureter, segundo esta trajetória, foi de 19 e 51 segundos, respetivamente (variações de 14 a 45 e 45 a 67 segundos). Estes resultados representam uma melhoria do tempo de punção entre 75% e 85%, quando comparados com o estado da arte dos métodos atuais. Além do feedback visual, som 3D e feedback vibratório foram explorados de modo a fornecer informações complementares da posição da agulha. Verificou-se que com este tipo de feedback, o cirurgião tende a seguir uma trajetória de punção com desvios mínimos, sendo igualmente capaz de antecipar qualquer movimento, mesmo sem olhar para o monitor. Fontes de som e vibração podem ser corretamente detetadas em 79,2 ± 8,1% e 91,1 ± 3,6%, com erros médios de angulação de 10.4º e 8.0 graus, respetivamente. Adicionalmente ao sistema de navegação, foram também produzidos três transdutores de ultrassom circulares com um canal de trabalho para a agulha. Para tal, foram exploradas diferentes configurações de fabricação em termos de materiais piezoelétricos, transdutores multi-array ou singulares e espessura/material de layers de suporte. Os sinais originados em cada transdutor foram filtrados e processados de modo a detetar de forma automática os ecos refletidos, e assim, alertar o cirurgião quando existem variações anatómicas ao longo do caminho de punção. Os transdutores foram mapeados num tanque de água e testados em 45 phantoms. Os resultados mostraram que o feixe de área em corte transversal oscila em torno do raio de cerâmica, e que os ecos refletidos são detetados em phantoms com comprimentos superiores a 80 mm. Desta forma, é expectável que a introdução deste novo sistema a nível do ARP permitirá conduzir o cirurgião ao longo do caminho de punção ideal, aumentado a confiança do cirurgião e reduzindo possíveis complicações (p.e. a perfuração dos órgãos). Além disso, de realçar que este sistema apresenta o potencial de tornar o ARP livre de radiação e alarga-lo a cirurgiões menos especializados.The present work was only possible thanks to the support by the Portuguese Science and Technology Foundation through the PhD grant with reference SFRH/BD/74276/2010 funded by FCT/MEC (PIDDAC) and by Fundo Europeu de Desenvolvimento Regional (FEDER), Programa COMPETE - Programa Operacional Factores de Competitividade (POFC) do QREN