Cryosurgery in the battle against cancer

Thermal gradients and cryosurgical probe performance

Некоторые теоретические аспекты криохирургии




Introduction: Disease statistics of recent decades reveal the increasing frequency of cancer and cancer deaths, and this in spite of exorbitantly risen financial costs for diagnostics and therapy (major equipment, intensive care, etc.). The situation has by no means improved in recent years and the current treatment modes appear to be of limited effectiveness. A new way of thinking must help in a decisive way to determine the future of cancer research and treatment. New methods of diagnosis and treatment should finally lead to a significant increase in the rates of cure for neoplastic disease. Modern cryosurgery, which is a particularly sparing surgical technique, is today internationally highly respected. The excellent results which have been published in numerous international journals are the outcome of many years of practical experience. At the same time it has become clear that the best use of this method has only become possible through the development of efficient medico-technical devices.

Purpose: To be an important contribution to the further development of cryosurgery and cryotechnology in medicine and to its future indispensability.

Material and Mathods: To date more than 2000 patients have received cryosurgical treatment, either in targeted tissue or an entire organ, both on an in-patient and an out-patient basis.

Results: Our theoretical, experimental and clinical knowledge such as other world-wide authors shown that has been gathered throughout the world is making it possible to successfully treat different kinds of cancer. The most extraordinary successes have been achieved with "cold" or "white" surgery. For 87% cancer patients it borders on the miraculous. Not only did they quickly regain their previous quality of life and thus also their will to live, most important of all they were pain-free. Furthermore, they did not require general anesthesia and were either outpatients or very briefly inpatients. This new surgical technique and high-tech cryotechnology (Puls, Kyiv, Ukraine) offers the patient a number of advantages. This high-tech device "Universal Cryosurgical System" was developed and put into use in record time on the basis of our own know-how as well as on the basis of international theoretical, experimental and clinical knowledge

Conclusion: The enormous efficiency (performance), the surgically uncomplicated results, the high rate of treatment success, as well as the enhanced quality of life of the patients will doubtless contribute to an upsurge in the use of this method in the near future. At the present time the "Universal Cryosurgical System" created by an international medico-technical team is considered to be the world-wide most advanced technology for cryosurgery applicable in many different areas of medicine. Our new cryosurgical technology is able to create sub-zero temperatures of up to -196°C where they are required, that is, where the cryosurgical instrument makes contact with the tissue, and this accurate freezing procedure can, moreover, be repeated again and again. Although essential for cryosurgery to be effective, repeated lowering of the temperature to such a degree has up to now not been possible.

THERMAL GRADIENTS AND CRYOSURGICAL PROBE PERFORMANCE
February 1997

John Bauhst, H. Ma, C-M Zhang, A. Gage
SUNY at Binghamton and Buffalo and Cryomedical Sciences, Inc., Rockeville, MD USA

Successful cryosurgery requires knowledge of cryosurgical probe performance. Our objective was to determine the freezing capability of cryosurgical probes and to evaluate this capability in terms of the factors in the freeze/thaw cycle known to produce a destructive response.
Method - Cryosurgical probes, 3.4 mm and 8 mm in diameter, were placed in agelatin bath and cooled to tip temperatures of -195 °C, -175 °C and -100 °C by cryosurgical apparatus (CMS AccuProbeR System).
Thermocouples, placed on probe freezing surface and at distances of 4, 8, 12, 16, and 20 mm from the surface, measured temperature changes during the growth of the iceball. Mutiple runs of 20 minutes at each of the settings provided data.

Results - The 8 mm probe achieved a tip temperature (PT) of -195°C in 3 minutes and produced a 7cm iceball in 20 minutes. The 8mm probe used with a PT of -100°C produced a 5.5cm iceball in 20 minutes. The -40°C isotherm was 5mm inside of the 0°C isotherm with PT of -195°C, 7mm inside of the 0°C isotherm with a PT of -175°C, and 13mm inside o the 0°C isotherm with a PT at -100°C. The 3.4mm probe with PT at -175°C produced a 5cm iceball in 20mins. Used at -100°C, the resultant iceball was 4cm in 20 minutes. The -40°C isotherm with PT at -175°C was 10mm from 0°C isotherm. With PT at -100°C, the -40°C isotherm was only 4mm from the probe, 16mm inside of the 0°C isotherm.

Conclusions - The colder the probe temperature, the faster the rate of freezing and the larger the frozen volume. The colder the probe and the faster the freezing rate, the closer the -40°C isotherm is to the 0°C isotherm. Probe temperatures of -175°C and colder are needed to create lethal temperatures more than 2cm from the probe, as is required for many cancers.

From: Proceedings 10th World Congress of Cryosurgery
Method of extension of the volume of the zone of cryolesion
November 1998

V V Shafranov, AV Kobiatsky, EN Borkhunova, AV Taganov
Pediatric Surgery department Russian State Medical University, Moscow, Russia

Experience gained so far by cryogenic surgery indicates that the possibilities of cryodestruction of sizable pathological formations are fairly limited. To overcome this barrier, it is necessary to change the status of the tissues, making them more sensitive to cryodestruction.
The theoretical investigations suggest that microwave irradiation is one of the factors capable to change the status of tissues and to raise their sensitivity to cold exposure. Experiments on livers of 98 rabbits showed that microwaves of certain range do not induce irreversible changes in biological tissues but Promote a significant increasement of the necrotic zone. It has been found that microwaves affect bound water which becomes more mobile and sensitive to cold. To evaluate the status of free and bound water under freezing before and after microwave irradiation, a nuclear magnetic resonance method was used. it has been established that heat conductivity markedly increased after UHF irradiation.
The combined use of UHF irradiation and cryogenic destruction is 30-40 times more effective than cryogenic destruction alone. The UHF-cryodestruction method allowed to avoid complex surgical operations and to get good clinical results in children with angiomas. Success was achieved in 95%.

Преимущества криохирургических операций по сравнению с традиционными очевидны: простота, безболезненность, отсутствие кровотечений, высокая точность и быстрая органотипическая регенерация, отсутствие заметной общей реакции, высокая эффективность лечения. Все это порождает некоторые иллюзии относительно возможностей криохирургии как у врачей, так и у разработчиков криогенной аппаратуры. Казалось, что увеличение холодопроизводительности криоинструмента и поверхности теплообмена рабочей части наконечника способно усилить разрушающее действие низкой температуры. Однако этого не происходит в силу ряда причин. Объяснение характера криоповреждения тканей с позиций теории Mazur R. для криохирургии является неадекватным. Данная теория не учитывает структурные, метаболические и теплофизические особенности тканей, которые и ограничивают разрушающие возможности низких температур. Механизм повреждения тканей существенно отличается от такового клеток, погруженных в раствор. "Мишенью" для криодеструкции в ткани является микроциркуляторное русло, так как именно в нем сосредоточено наибольшее количество свободной воды. Кроме того, прямой и опосредованной (за счет нарушения микроциркуляции) деструкции подвергаются клетки. При высокой скорости охлаждения -200°С в мин.) в зоне замораживания возникают термомеханические напряжения, усилия здесь достигают 30 кг/см2. За счет эффектов пучения и смещения происходит "вспенивание" крови, ткань разрывается, и ее структура необратимо деформируется. При этом необходимо учитывать, что организм воспринимает криоинструмент с контактным наконечником как точечный источник холода, даже при использовании самой мощной криосистемы. Исходя из этого, понятна безуспешность локального замораживания больших объемов тканей и ограниченность аппаратурных возможностей криотехники. При инженерно-теоретических разработках криохирургической аппаратуры и прогнозирования результатов криовоздействия необходимо учитывать не локальное, а общее тепловыделение. Данные по локальному тепловыделению ткани имеют значительную ошибку, так как не отражают истинную картину тепловых процессов и не учитывают комплекс лабильных энергетических процессов. В этой связи была создана математическая модель процесса замораживания, которая учитывает взаимосвязь "криоинструмент - ткань" и позволяет прогнозировать размеры зоны крионекроза для разных методик криовоздействия, в том числе комбинированного СВЧ-криогенного. На основании данной модели были получены т.н. предельные зоны замораживания. Следует подчеркнуть, что деструкция ткани с использованием низких температур имеет черты вероятностного процесса, и полученные модели носят приблизительный характер. Однако они позволяют учесть множество факторов, влияющих на процесс криодеструкции, в частности такие важные факторы как тепловыделение и структура ткани.

В кн.: Достижения криомедицины. Санкт-Петербург, Изд-во "Наука", 2001, С.78-89.

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