<p>Radio-frequency (RF) lesioning is a method utilising high frequency currents for thermal coagulation of pathological tissue or signal pathways. The current is delivered from an electrode with a temperature sensor, permitting control of the current at a desired target temperature. In the brain RF-lesioning can e.g. be used for severe chronic pain and movement disorders such as Parkinson’s disease. This thesis focuses on modelling and simulation with the aim of gaining better understanding and predictability of the lesioning process in deep brain structures. The finite element method (FEM) together with experimental comparisons was used to study the effects of electrode dimensions, electrode target temperature, electric and thermal conductivity of the brain tissue, blood perfusion and cerebrospinal fluid (CSF) filled cysts. Equations for steady current, thermal transport and incompressible flow were used together with statistical factorial design and regression analysis for this purpose.</p><p>Increased target temperature, electrode tip length and electrode diameter increased the simulated lesion size, which is in accordance with experimental results. The influence of blood perfusion, modelled as an increase in thermal conductivity in non-coagulated tissue, gave smaller simulated lesions with increasing blood perfusion as heat was more efficiently conducted from the rim of the lesion. If no consideration was taken to the coagulation the lesion became larger with increased thermal conductivity instead, as the increase in conducted heat was compensated for through an increased power output in order to maintain the target temperature. Simulated lesions corresponded well to experimental in-vivo lesions.</p><p>The electric conductivity in a homogeneous surrounding had little impact on lesion development. However this was not valid for a heterogeneous surrounding. CSF-filled cysts have a much higher electric conductivity than brain tissue focussing the current to them if the electrode tip is in contact with both. Heating of CSF can also cause considerable convective flow and as a result a very efficient heat transfer. This affected simulated as well as experimental lesion sizes and shapes resulting in both very large lesions if sufficient power compared to the cysts size was supplied and very small lesions if the power was low, mitigating the heat over a large volume.</p><p>In conclusion especially blood perfusion and CSF can greatly affect the lesioning process and appear to be important to consider when planning surgical procedures. Hopefully this thesis will help improve knowledge about and predictability of clinical lesioning.</p>

An increasing number of power plants in Scandinavia are beginning to use biofuel instead of coal or oil. The material in the new fuel is a mixture of woodchips, mostly Pine, Spruce and Salix, bark, GROT (tops and branches from felling waste) and sawdust from sawmills. It is heterogeneous, having a moisture content varying from 15% up to 65%. The moisture content affects the combustion of the fuel and therefore its commercial value. The industry is now interested in obtaining a method for measuring the moisture content of biofuel, quickly and reliably; preferably on delivery at the power plant. The measuring technique presented in this thesis is the first reported in the literature capable of measuring the moisture content of a large sample of such an heterogeneous material as biofuel. The equipment is today calibrated for a sample volume of 0.1 m3. A radio frequent signal is supplied from an antenna and penetrates the biofuel. Its reflection is modeled using partial least squares. As part of the work presented in this thesis, a new type of measuring rig and an analysis method for measurement of the moisture content of large samples of heterogeneous material have been developed. A statistical model for moisture content measurements of five different biofuel materials using radio waves has been built, having a root mean square error of prediction of 2.7. The interactions between biofuels and radio frequent signals have been demonstrated, indicating a variation of the reflection with varying types of biofuel material and variation in the reflection and delay of the signal with varying moisture content.

This thesis aims to increase the knowledge on people with symptoms attributed to electromagnetic fields (EMF) by investigating the effects of EMF exposure and by additional description of the heterogeneous group of people reporting EMF-related symptoms. The effect of mobile phone (MP)-like radio frequency (RF) fields on symptoms, autonomic nervous system (ANS) parameters, short-term memory, and reaction time in persons with MP-related symptoms (MP participants) was investigated in a provocation study. A second provocation study investigated the effect of similar exposure on serum concentration of biomarkers in persons with atopic dermatitis. No effect of exposure was detected in either study. MP participants displayed changes in heart rate variability (HRV) during cognitive tests, but not during rest. This contrasts with earlier findings, participants with symptoms attributed to EMF sources in general (EHS participants) displayed an elevated sympathetic nervous system activity both during cognitive tests and during rest. Proposed differences between subgroups of persons with EMF-related symptoms with respect to symptoms, personality traits and stress were investigated in a questionnaire study. MP participants reported primarily symptoms from the head; EHS participants reported symptoms from many organ systems. Furthermore, EHS participants reported higher levels of anxiety, depression, stress, and exhaustion when compared with a reference group. MP participants reported higher levels of anxiety and exhaustion only. In a pilot study, 24-hour and short-term HRV were investigated in EHS participants, to examine whether the previously observed sympathovagal imbalance would still be present. There was a tendency toward increased parasympathetic activity compared with earlier recordings, and a reduction of symptoms. Twenty-four hour and short-term recordings were fairly similar for each participant; however, there were large between-subject differences. The results do not support the hypothesis of effects of MP-like RF exposure on symptoms, ANS activity, CFFT, cognitive function, or biomarkers. However, they do support the hypothesis that persons with different symptom attribution (MP and EHS) may differ also in ANS activity and psychological aspects.

This is a prospective, non-randomized pilot study comparing the cost-utility of hepatic resection, radiofrequency ablation (RFA), systemic chemotherapy, and symptom control only for the treatment of colorectal liver metastases. Seven patients underwent hepatic resection, 7 underwent RFA, 20 received chemotherapy, and 6 received symptom control alone. Liver resection provided an average of 2.51 QALY’s compared to 1.99 QALY’s for RFA, and 1.18 QALY’s for chemotherapy, and 0.82 QALY’s for symptom control alone. The costs were $20,122, $ 15,845, $15,069, and $3,899, respectively. The cost-utilities of liver resection and RFA were similar at $8,027 and $7,965 per QALY, respectively, although patients receiving RFA generally had more advanced disease. The cost-utility of chemotherapy was $12,751/QALY and the cost-utility of symptom control alone was $4,788/QALY. RFA is still a relatively new. However, if long-term survival proves promising, it may prove to be a viable alternative to liver resection. / May 2006

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (p. 208-215).

M. Tech. Electrical Engineering. / Food security has become a global epidemic over the years. The objective of this research is to perform laboratory tests in order to measure and evaluate the electrical properties of different food materials using Radio Frequency (RF) channels. Presented in this document is a literature review which focuses on the dielectric and electrical properties of specific food materials, food media characteristics, transmission properties, the methods of testing that have been used as well as the achieved results, which provide a broader perspective of and about the food specimen that have undergone the experiment. The research is directed towards sensing food items through practical and experimental measurements as a contribution towards the development and erection of a future design and the operation of a device that will beam RF waves through food to detect any bacterial infections that may be present in the food.

Tyrimo metu apibendrinti ir išanalizuoti 74 knarkiančiųjų bei lengvu ir vidutinio sunkumo obstrukcinės miego apnėjos hipopnėjos sindromu (OMAHS) sergančių pacientų klinikiniai duomenys, ir įvertinta 38 jų miego partnerių emocinė būklė prieš pacientų gydymą ir praėjus 2–4 mėn. po pacientams taikyto knarkimo ir OMAHS gydymo – radiodažnuminės termoabliacijos (RDTA). Šio darbo uždaviniai: 1. Ištirti ir palyginti knarkiančiųjų bei sergančių lengvu ir vidutinio sunkumo OMAHS pacientų viršutinių kvėpavimo takų anatomines ir funkcines savybes, apnėjų hipopnėjų indeksą, nusiskundimus sveikata ir emocinę būklę. 2. Įvertinti knarkiančiųjų bei sergančių lengvu ir vidutinio sunkumo OMAHS pacientų gyvenimo kokybę prieš pradedant gydymą ir po gydymo RDTA. 3. Įvertinti su RDTA operacijomis susijusių pacientų nusiskundimų intensyvumą ir pooperacinių komplikacijų dažnį. 4. Ištirti ir įvertinti knarkiančiųjų bei sergančių lengvu ir vidutinio sun¬kumo OMAHS pacientų nusiskundimus ir apnėjų hipopnėjų indeksą po gydymo RDTA. 5. Ištirti ir įvertinti knarkiančiųjų bei sergančių lengvu ir vidutinio sunkumo OMAHS pacientų emocinę būklę po gydymo RDTA. 6. Ištirti ir įvertinti knarkiančiųjų bei sergančių lengvu ir vidutinio sunkumo OMAHS miego partnerių emocinę būklę ir jos pokyčius po pacientų gydymo RDTA. Po pacientų gydymo RDTA nustatytas pacientų nusiskundimų intensyvumo ir apnėjų hipopnėjų indekso sumažėjimas bei emocinės būklės pagerėjimas, ir pacientų miego part¬ne¬rių depresiškumo sumažėjimas... [toliau žr. visą tekstą] / A total of 74 snoring and mild to moderate obstructive sleep apnea hypopnea syndrome (OSAHS) patients underwent complete full night polysomnography (PSG) and clinical examination and were treated with two sessions of radiofrequency tissue ablation (RFTA). The emotional state of 38 bed partners of snoring and mild to moderate OSAHS patients were evaluated at the baseline and 2–4 months after the patients completed the treatment. Objectives of the study: 1. To examine and evaluate the relationship between complaints, anatomical features, PSG results, and emotional state of snoring and mild to moderate OSAHS patients. 2. To assess the quality of life among snoring and mild to moderate OSAHS patients before and after the RFTA treatment. 3. To analyze the morbidity and the rate of postoperative compli¬ca¬tions of RFTA. 4. To evaluate the influence of RFTA on the objective (PSG results) and subjective (complaints) outcomes in snoring and mild to moderate OSAHS patients. 5. To evaluate the influence of RFTA on the outcomes of anxiety and depression in snoring and mild to moderate OSAHS patients. 6. To examine the emotional state and to evaluate the effect of RFTA on anxiety and depression in bed partners of snoring and mild to moderate OSAHS patients. A remarkable improvement in patients’ complaints, PSG results and emotional state after RFTA was observed. RFTA therapy resulted in improved depression scores for the bed partners of snoring and mild to moderate OSAHS patients.

Šio mokslinio darbo tikslas buvo įvertinti efektyvumą bei saugumą gydant prieširdžių virpėjimą, naudojant elektrofiziologinius RD abliacijos unipolinius elektrodinius kateterius pacientams, kuriems mitralinio vožtuvo ydą koreguojančios operacijos atliekamos per prieširdžių pertvaros(tarprieširdinės ir viršutinio pertvaros) pjūvius. Atlikus šią operaciją – po 1 metų >80% pacientų neturi prieširdžių virpėjimo/plazdėjimo, iš jų 76% nevartoja antiaritminių vaistų. galutinio sekimo metu fiksuota, kad išliko 71,5% pacientų be prieširdžių virpėjimo ir plazdėjimo. Labirinto procedūra prailgina tik 16 ± 3 min dirbtinės kraujotakos laiką. Išeities ir operacinių parametrų atžvilgiu tarprieširdinės ir viršutinio pertvaros pjūvių grupės nesiskyrė. Mitralinio vožtuvo ydos korekcijos pobūdis – protezavimas ar plastika - statistiškai patikimai neturėjo PV gydymo rezultams. Gydymo efektyvumui įtakos turi: didesnė širdies nepakankamumo funkcinė klasė ir kairiojo prieširdžio išilginis dydis nustatytas echoskopiškai M - režimu. Pooperacinių antrinių prieširdinių tachikardijų ir atipinių prieširdžių plazdėjimo kombinuota (taikant antiaritminius vaistus, perstemplinę stimuliaciją ir perkateterinę radiodažnuminę abliacija) terapija leidžia pagerinti labirinto procedūros rezultatus. Viršutinis pertvaros pjūvis naudotinas sudėtingose operacijose, taip galima lengviau apžiūrėti mitralinį vožtuvą ir koreguoti mitralinę ydą. / The purpose of this scientific work was to evaluate safety and efficacy of treatment of atrial fibrillation using monopolar radiofrequency ablation electrodes in patients who undergo mitral valve surgical correction using incisions of atrial septum (trans-septal and superior septal approaches). More than 80% of the patients are free of atrial fibrillation one year after the operation and 76% of these patients do not use anti-arrhythmic drugs. During the final visit of follow-up it was recorded that 71.5% of the patients remained free of atrial fibrillation and flutter. The maze procedure increases duration of cardiopulmonary by-pas for 16 ± 3 min, only. The baseline and surgical correction data in groups of patients of trans-septal and superior septal approaches did not differ. The method of mitral valve correction (implantation of mitral valve prosthesis or plasty of the valve) had no statistically significant influence on the results of atrial fibrillation treatment. The factors influencing the efficacy of the treatment include higher class of heart failure and larger longitudinal measurement of the left atrium found on echoscopy using M-mode. Combined therapy of secondary atrial tachycardia and atypical atrial flutter (by means of anti-arrhythmic drugs, trans-oesophageal stimulation and per-catheter ablation) enables to improve the results of maze procedure. The superior septal approach should be used in complicated operations as using this incision it is more... [to full text]

This is a prospective, non-randomized pilot study comparing the cost-utility of hepatic resection, radiofrequency ablation (RFA), systemic chemotherapy, and symptom control only for the treatment of colorectal liver metastases. Seven patients underwent hepatic resection, 7 underwent RFA, 20 received chemotherapy, and 6 received symptom control alone. Liver resection provided an average of 2.51 QALY’s compared to 1.99 QALY’s for RFA, and 1.18 QALY’s for chemotherapy, and 0.82 QALY’s for symptom control alone. The costs were $20,122, $ 15,845, $15,069, and $3,899, respectively. The cost-utilities of liver resection and RFA were similar at $8,027 and $7,965 per QALY, respectively, although patients receiving RFA generally had more advanced disease. The cost-utility of chemotherapy was $12,751/QALY and the cost-utility of symptom control alone was $4,788/QALY. RFA is still a relatively new. However, if long-term survival proves promising, it may prove to be a viable alternative to liver resection.

The effect of short, strong radiofrequency pulses on the nuclear spin system is examined. Providing the durations of the pulses are short with respect to coupling constants within the spin system, they may be described by simple rotation operators which are exponential functions of the angular momentum operators. Operator algebra can be used to define the interaction of such pulses with the spin system, and the mutual interaction of a sequence of pulses. The case of a simple coupled spin system is examined in detail and it is found that a vector model can be used to describe the motion of the expectation values of the observables. This model also allows treatment of such 'non-classical 1 effects as coherence transfer and multiple-quantum coherence. The proposal is also made that certain types of pulse imperfection may be compensated by using specially constructed sequences of small numbers of pulses, which are termed 'composite pulses'. Their compensatory action is illustrated by computer simulation, and by experimental results. In the case of certain symmetrical composite pulses, operator algebra can be used to understand their overall effect in the presence of pulse imperfections, suggesting their use in such critical applications as multiple spin echo trains. Another class of symmetrical composite pulses provides rotations by arbitrary angles around the z-axis of the rotating reference frame, and is expected to be of use in multiple-quantum spectroscopy.