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Актуальність. Невирішеними питаннями застосування лазеріндукованої інтерстиціальної термотерапії (ЛІТТ) у лікуванні солідних вузлів щитоподібної залози (ЩЗ) на сьогодні є визначення показань і протипоказань, методики і технології її виконання, підвищення ефективності і покращання віддалених результатів. Мета дослідження: вивчити вплив ЛІТТ на навколовузлову тканину і функціональну здатність ЩЗ, визначити фактори, що впливають на терміни заміщення вузла сполучною тканиною та її об’єм, розробити показання до повторного застосування термотерапії. Матеріали та методи. З використанням ЛІТТ проліковані 272 хворі на вузловий зоб без ознак кістозної дегенерації. Усі пацієнти — жінки віком від 22 до 68 років. Об’єм вузлів був у межах від 0,8 до 5,0 см3. За ультразвуковими характеристиками, зокрема за ехогенністю, вузли були такими: 46 — гіпоехогенні, 189 — ізоехогенні та 37 — гіперехогенні. Використовували діодний лазер Лахта-Мілон. ЛІТТ проводили за таких параметрів: довжина хвилі 1060 нм, безперервний режим, потужність випромінювання у межах від 2,5 до 3,2 Вт. Перебіг ЛІТТ контролювали сонографічно. Зміни у вузлі, навколовузловій тканині та функцію залози після ЛІТТ визначали на другу добу, через 2 тижні, через 1, 3, 6, 9 та 12 місяців після маніпуляції. Результати. На другу добу після лазерної термотерапії у вузлах розвивається асептичне запалення, а розміри їх збільшуються на 25–30 %. У подальшому, у визначені терміни обстеження, розміри вузлів зменшувались, показники гормональної функції не змінювались. Через 6 місяців після ЛІТТ при розмірах вузлів до 2 см повне їх заміщення сполучною тканиною відмічалось у всіх випадках гіпо- й ізоехогених вузлів і в 71 % — гіперехогенних, а при розмірах від 2 до 5 см — у 75 % випадків вузлів гіпоехогенної структури, 18 % — ізоехогенної і не було позитивного ефекту у разі гіперехогенних вузлів. У випадках неефективного лікування знадобилося проведення повторної ЛІТТ, після якої у всіх пацієнтів настала повна редукція вузла. Висновки. У розроблених режимах ЛІТТ не викликає деструктивних змін у навколовузловій тканині і розладів гормональної функції залози. Тривалість регресу і заміщення вузла сполучною тканиною визначають його ехогенність і об’єм. Показаннями до повторного застосування термотерапії є залишкова тканина в ділянці вузла в межах більше 42 % від вихідного об’єму через півроку після проведеного лікування та наявність у ній тиреоїдного епітелію.

The experience in applying a new method of treating patients with Baker’s cyst is described. The method is based on laser-induced thermotherapy using a special dual-port introducer. It has been shown that the use of the developed surgical instruments makes it possible to reduce the time and cost of the procedure and to increase its safety. It also allows the period of rehabilitation to be reduced in comparison with the conventional surgical methods of treatment. Based on the results of the application of the new method and equipment, practical recommendations have been formulated that make it possible to individualize the treatment of patients with Baker’s cyst.

—A thermophysical model of heat transfer from a liquid heated by radiation into biological tissues with a cyst of an individual picture of temperature fields, which takes the parameters of laser radiation, as well as the individual thermodynamic and morphometric characteristics of the object of exposure and its syntopy, into account, is proposed. The model is designed for algorithmization of performance of laser-induced indirect thermotherapy of cavity tumors. A comparison was made between the theoretical prediction of the dynamics of temperature changes in the wall of a Baker’s cyst and the experimental data obtained using a thin needle thermocouple placed through a needle in the center of a cyst filled with liquid, whose dimensions had been previously determined by magnetic resonance imaging. It was shown that at the heat transfer coefficient of 3000 W/(m2 K) the proposed model described the heating of the cyst contents due to heat transfer from its inner wall accurately.

Nodular formations of the thyroid gland are quite a widespread pathology. The prevalence of nodular goiter in the population is present in 50–70% of the total population. Basically, thyroid nodes are benign and aren’t a direct threat to human life. Laser-induced thermotherapy is one of the minimally invasive methods of treatment. The main idea of laser-induced thermotherapy is to heat the thyroid nodule by laser radiation with a wavelength of 805–1060 nm to a temperature of 41–46°С. In this case, the results of treatment by laser-induced thermotherapy (LITT) in 7 patients with nontoxic goiter were studied. There were no complications after the procedure. The technique of LITT showed high efficiency as a treatment of nontoxic goiter, because in many cases there was a decrease in the size of the thyroid node by 71.6 ± 16.8%. The introduction of LITT to the clinical practice and inclusion it into guidelines of nodular non-toxic goiter treatment can give to patient opportunity to treat nodes without surgical operations.

Laser-induced thermotherapy (LITT) plays an important role in oncology to treat human liver tumors. LITT is a minimally invasive method causing tumor destruction due to heat ablation and coagulative effects of the tissue. Tumor tissue is much more sensitive to heat than normal healthy tissue. The big advantage of the LITT compared to other minimally invasive procedures, such as microwave ablation or radiofrequency therapy, is that the treatment primarily takes place under MRI control, such that patients are exposed to a small radiation dose. The present paper describes the mathematical modeling of laser-induced thermotherapy and shows simulation results for porcine liver.

Laser-induced thermotherapy is a local, minimally invasive treatment for liver tumors, which uses laser radiation to destroy targeted tissue. Many factors, such as the placement of the applicator(s), the length of the treatment and the amount of radiation introduced, affect the success of the treatment. In this work, we focus on controlling the amount of laser power applied during the treatment. This results in a PDE-constrained optimal control problem. Because such problems are computationally expensive to solve directly, a space-mapping approach is used. The coarse model used in the space-mapping method is derived through a novel linearization of the constraining equations and subsequently reduced using proper orthogonal decomposition. An example problem shows the viability of this approach.

Laser-induced thermotherapy (LITT) is used to treat liver cancer by inserting a laser applicator into the tumor and applying radiation to heat and destroy it. A mathematical model for the simulation of LITT is compared to experimental results with ex-vivo pig livers.

Laser-induced thermotherapy (LITT) predicts the effects of laser applications in LITT and optimizes the efficacy of irradiation plans, the light distribution in liver tissue, the optical tissue properties, and the changes caused by thermal denaturation. In this paper, COMSOL Multiphysics, a commercially available Finite Element (FE) simulation software package, was used to simulate the interaction between laser and liver tissue. A short-pulse laser point source, coagulated liver tissue and uniform soft tissue submerged in water were established. In this study, two sets of simulation models were used to describe the principles: 1) Diffusion equation was used to simulate light propagation; 2) Temperature changes were simulated using biothermal equations. The experimental results show that there are significant differences in penetration depth and light energy distribution of native and coagulated liver tissues under laser irradiation with different wavelengths. The penetration depth of the liver tissue after heat coagulation is significantly reduced. In addition, the simulation can present the temperature curve during the clinical hyperthermia of liver cancer and determine the effect by various treatment parameters. These results provide a better understanding of laser-tissue interactions and may be helpful to researchers in the fields of laser medical.

Photothermal therapy (PTT) has been emerging as an effective, minimally invasive approach to treat cancers. However, a method to quantitatively evaluate the treatment effect after laser-induced thermotherapy (LITT) is needed. In this study, we used 808 nm laser radiation with three different power densities to treat the breast cancer tissue from 4T1 cell lines in a mouse model. The viscoelastic properties of the treated cancer tissues were characterized by a two-term Prony series using a ramp-hold indentation method. We observed that instantaneous shear modulus G0 was significantly higher for the treated cancer tissues than that of the untreated tissue when treated with a power density of 1.5 W/cm2, but significantly lower with a power density of 2.5 W/cm2. The long-term shear modulus G∞ was also significantly higher for the cancer tissue at 1.5 W/cm2, compared to the untreated tissue. The treatment effects were verified by estimating the cell apoptosis rate using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). Our results indicate that the viscoelastic properties of the tissue could potentially be used as biomarkers for evaluating the LITT treatment effect. In addition, we also observed a strain-independent behavior of the treated cancer tissue, which provided useful information for applying in vivo imaging method such as magnetic resonance elastography (MRE) for treatment evaluation based on biomechanical properties.

We investigate the planning of minimally invasive tumor treatments via laser-induced thermotherapy. The goal is to control the laser in order to obtain an optimal treatment, e.g. eradicating the tumor, while leaving as much healthy tissue unharmed as possible. To this end, we define a PDE-constrained optimal control problem. As these problems are usually computationally expensive, we propose a simplified modeling approach using reduced-order models. Numerical results illustrate the viability of our approach.

Background: Diffuser fibers have been used for some time in the fields of laser-induced thermotherapy and photodynamic therapy. For their applicability the breaking strength, the thermostability and a homogeneous radiation profile are of great importance. Flexible applicators offer special benefits because they introduce a totally new range of application possibilities. Objective: The aim of the presented investigations was to develop a totally new flexible diffuser fiber generation which can be produced cheaper and without the use of any further materials. For this purpose it was proposed to induce scattering micro dots directly into silica fibers by generating a local change of the refractive index in the core of the optical fiber. The resulting diffuser was expected to create a homogeneous radiation profile containing at least 80% of the light coupled into the optical fiber, i.e. less than 20% prograde (forward) emission. Materials and methods: On the basis of former research results, scattering micro dots were induced linearly into the core of an optical silica fiber through a multiple photon process using a femtosecond laser. In addition to the macroscopic optical control by means of a microscope, the form of the radiation profile was examined as well as the non-scattered forward emission which depends on a variety of influencing factors. The processing was optimized according to the observations made. The thermostability of the developed prototypes was assessed by using a thermocamera, and the minimal bending radius was determined. Finally the prototypes were tested and validated ex vivo using porcine liver. Results: An influence of the processing power, the number and radial position of the scattering micro dots as well as the therapeutic coupled-in wavelength onto the form of the radiation profile and the non-scattered forward emission was determined. Both the form of the radiation profile and the prograde emission were found to be independent of the therapeutic laser power coupled into the fiber. The developed prototype had a nearly homogeneous radiation profile, a forward emission of 12.8±2.1% in average, and a minimum bending radius of 31±6 mm. Conclusion: The non-scattered forward emission of the developed diffusers was within the objective of below 20% and the radiation profile was very nearly homogeneous. In order to improve the reproducibility of the production process, an improved fixation apparatus needs to be developed.

Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver and is the fifth most common cancer worldwide.1,2 It is the third leading cause of cancer-related deaths worldwide and globally accounts for as many as 500,000 deaths annually.1 Although hepatic resection and transplantation offer a potential for curative therapy, most patients with HCC (70%–80%) are not candidates for curative resection or transplantation because of either advanced stage at the time of initial presentation or because of underlying advanced cirrhosis.3,4 Transarterial chemoembolization (TACE) is the most widely used first-line treatment in the Western World and Asia for patients with unresectable HCC. Transarterial chemoembolization is considered the standard of care especially in Barcelona-Clinic Liver Cancer (BCLC) B patients, based on 2 meta-analyses that demonstrated 2-year overall survival benefit.5,6 In addition, TACE alone or in combination with laser induced thermotherapy resulted in improved patient survival in patients with unresectable noncolorectal and nonbreast cancer origin.7 There is increased interest in determining response of hepatic malignancies to therapy using the entire tumor burden rather than a single index lesion.8 In developing RECIST 1.1, the response evaluation criteria in solid tumors (RECIST) working group considered moving from anatomic unidimensional assessment of tumor burden to either volumetric anatomical assessment or to functional assessment. However, this was deemed inappropriate owing to insufficient standardization of the acquisition or image analysis techniques.8 Measuring volumetric tumor burden remains critical because patients with extensive hepatic involvement at baseline may have less functioning liver parenchyma and therefore less likelihood for survival after intra-arterial therapy (IAT) compared with those with low tumor burden.9 Moreover, in patients with colorectal metastases, the number and size of metastases are significant prognostic factors for long-term survival in patients treated with laser-induced interstitial therapy.10 Functional imaging techniques are increasingly being used to monitor response to therapy, often predicting the success of therapy before conventional measurements using size change.11-14 The European Association for the Study of the Liver guidelines recommend measuring the enhancing part of the tumor in the axial plane for assessing treatment response; however, enhancement in a single axial plane may not reflect global changes in the entire tumor volume.15 Dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) can quantify tumor vascularity and thus can delineate zones of viable enhancing tumor and zones of tumor necrosis with poor/absent contrast enhancement.16 Several previous studies reported significant changes in contrast enhancement as well as apparent diffusion coefficient (ADC) after loco-regional therapy.13,17,18 Diffusion weighted imaging (DWI) and the generated ADC values can differentiate viable from dead tumor cells by assessing differences in membrane permeability. Successful treatment is reflected by increase in tumor water diffusion values, which manifests as increase in ADC values.11 With advances in image processing techniques, several recent studies have demonstrated changes in both of these functional techniques (ADC and DCE-MRI) in the index tumor volume rather than in a single axial plane.19-21 However, to date, there is sparse evidence of the value of assessing response in all targeted tumors using these functional techniques. Therefore, the objective of this study was to evaluate response in the entire targeted tumor burden using functional MRI response and its impact on overall survival in patients with HCC treated by IAT.

The use of magnetic resonance-guided laser-induced thermal therapy (MR-LITT) as a minimally invasive method of treating intra-cranial pathology is a rapidly growing field. The use of MR-LITT in neurooncology has shown promising results; however, there has been no review to date of the current literature.A review of the published literature regarding MR-LITT in neurooncology was performed. Studies on PubMed were included if at least one patient with a cerebral tumour or radiation necrosis was treated using quantitative MR thermography-guided LITT, as well as if either safety or outcomes were discussed.In treating recurrent Grade-III and -IV gliomas, we found improved median overall survival of 20.9 months from diagnosis of recurrence, which is comparable with that of 18.9 months for high-dose-rate brachytherapy and 24.4 months for repeated open surgery. Median progression-free survival (PFS) of recurrent glioma is noted to be 4.5 months. For metastatic lesions, we found a median overall survival (OS) to vary between 9.0 and 19.8 months with a PFS between 3.8 and 8.5 months. Current literature reports median OS in similar patients to lie between 7.0 and 28.6 months. Severe complication rates (with permanent deficits) are found to be between 12 and 16.7%, comparable with 11% found in literature for open surgery.The current literature shows that MR-LITT is safe and shows promising local tumour control rates. Larger randomised studies are warranted to further investigate this adjuvant therapy in the treatment of recurrent high-grade gliomas and metastases.

In 1982, Thomas J Vogl graduated from Ludwig Maximilian University of Munich (Germany) with an MD. In 1988, he obtained the position of Assistant Professor at the University of Munich, in 1992 Associate and Full Professor of the Free University of Berlin (Germany) and in 1995 Professor of the Humboldt University of Berlin (Germany). Currently, he is Head of the Department of Diagnostic and Interventional Radiology at the University of Frankfurt (Germany). He has been the recipient of several honorary awards, and is a member of multiple national and international radiological and oncological societies, as well as of editorial boards of journals. He has specialized in interventional oncology, vascular procedures, multidetector computed tomography, MRI, evaluation of contrast agent and magnetic resonance-guided procedures.

Purpose To evaluate the clinical value of different magnetic resonance imaging (MRI) sequences for a real-time thermo-monitoring during laser-induced thermotherapy (LITT) in kidneys. Methods Twenty-eight ex vivo pig kidneys were treated with laser ablation under MR guidance in a high-field MR scanner (Magnetom Espree or Avanto Fit, Siemens, Germany). For the thermal ablation of the kidney, a neodymium yttrium-aluminum-garnet (Nd:YAG) laser was used in combination with a special protective catheter (length 43 cm, 4 French) which is sealed at the distal end. First, ablation was performed for 7, 10, and 13 minutes using FLASH sequences for investigation of time-dependent growth of lesion size. In the second step, we evaluated the optimal imaging sequence during a 7 minutes ablation of the kidney and after cooling using four different MR sequences (Haste, FLASH, radial VIBE, and Caipirinha DIXON). Results Macroscopic lesion volume increased from 3,784 ± 1,525 mm3 to 7,683 ± 5,756 mm3 after the ablation from 7 to 13 minutes and MR volume ranged from 2,107 ± 1,674 mm3 to 2,934 ± 1,549 mm3 after the ablation from 7 to 13 minutes. During ablation, FLASH (132 ± 34%) and radial VIBE (120 ± 43%) sequences displayed lesion volumes most efficiently with a trend to overestimation. The Caipirinha DIXON (323 ± 24%) sequence overestimated the volumes significantly during real-time monitoring. The volumes measured by MRI with FLASH (61 ± 30%), Haste (67 ± 28%), or radial VIBE (48 ± 14%) sequences after cooling of the kidney after ablation were always underestimated. The Caipirinha DIXON (142 ± 2%) sequence still overestimated the lesion volume after cooling of the kidney. Conclusion LITT is a feasible ablation modality in kidney tissue. Moreover, macroscopic and MR lesion volume increases time-dependently. For online monitoring, radial VIBE and FLASH sequences seem to be most efficient. Lasers Surg. Med. 46:558–562, 2014. © 2014 Wiley Periodicals, Inc.

Surgery is currently considered the treatment of choice for patients with colorectal cancer liver metastases (CRLM) when resectable. The majority of these patients can also benefit from systemic chemotherapy. Recently, local or regional therapies such as thermal ablations have been used with acceptable outcomes. We searched the medical literature to identify studies and reviews relevant to radiofrequency (RF) ablation, microwave (MW) ablation and laser-induced thermotherapy (LITT) in terms of local progression, survival indexes and major complications in patients with CRLM. Reviewed literature showed a local progression rate between 2.8 and 29.7 % of RF-ablated liver lesions at 12-49 months follow-up, 2.7-12.5 % of MW ablated lesions at 5-19 months follow-up and 5.2 % of lesions treated with LITT at 6-month follow-up. Major complications were observed in 4-33 % of patients treated with RF ablation, 0-19 % of patients treated with MW ablation and 0.1-3.5 % of lesions treated with LITT. Although not significantly different, the mean of 1-, 3- and 5-year survival rates for RF-, MW- and laser ablated lesions was (92.6, 44.7, 31.1 %), (79, 38.6, 21 %) and (94.2, 61.5, 29.2 %), respectively. The median survival in these methods was 33.2, 29.5 and 33.7 months, respectively. Thermal ablation may be an appropriate alternative in patients with CRLM who have inoperable liver lesions or have operable lesions as an adjunct to resection. However, further competitive evaluation should clarify the efficacy and priority of these therapies in patients with colorectal cancer liver metastases.

Magnetic resonance-guided laser induced thermotherapy (MRgLITT) has become an increasingly relevant therapy for tumor ablation due to its minimally invasive approach and broad applicability across many tissue types. The current state of the art applies laser irradiation via cooled optical fiber applicators in order to generate ablative heat and necrosis in tumor tissue. Magnetic resonance temperature imaging (MRTI) is used concurrently with this therapy to plan treatments and visualize tumor necrosis. Though application in neurosurgery remains in its infancy, MRgLITT has been found to be a promising therapy for many types of brain tumors. This review examines the current use of MRgLITT with regard to the special clinical challenge of glioblastoma multiforme and examines the potential applications of next-generation nanotherapy specific to the treatment of glioblastoma.

The aim of this study was to evaluate the accuracy of real-time magnetic resonance imaging (MRI) T1-based treatment monitoring for predicting volume of lesions induced by laser-induced thermotherapy (LITT) of liver metastases.This prospective study was approved by the institutional review board and informed consent from all included patients was obtained. In 151 patients, 237 liver metastases were ablated during 372 LITT procedures. 1.5 T MRI treatment monitoring was performed based on longitudinal relaxation time (T1) using fast low-angle shot (FLASH) sequences. Patients underwent additional contrast-enhanced MRI directly after LITT, 24 h after the procedure and during follow-up at 3, 6 and 12 months. The amount of energy necessary to induce a defined necrotic area was investigated within the various liver segments.The total amount of energy applied during LITT varied from 6.12-225.32 kJ (mean 48.96 kJ). Ablation in liver segments 5 (2.12 kJ/cm(3)) and 8 (2.16 kJ/cm(3)) required the highest energy. The overall pre-ablative metastasis volume ranged from 0.5-51.94 cm(3) (mean 1.99 cm(3), SD 25.49 cm(3)) while the volume measured in the last available T1 image varied from 0.78-120 cm(3) (mean 26.25 cm(3), SD 25.66 cm(3)). Volumes measured via MRI T1-based treatment monitoring showed a stronger correlation with necrosis 24 h after LITT (r = 0.933, p0.001) than contrast-enhanced MRI directly after the procedure (r = 0.888, p0.001).Real-time MRI T1-based treatment monitoring during LITT of liver metastases allows for precise estimation of the resulting lesion volume and improves control of the energy necessary during ablation.

Tissue temperature distribution plays a crucial role in the outcome of laser-induced thermotherapy (LITT), a technique employed for neoplasias removal. Since recent studies proposed LITT for pancreatic tumors treatment, assessment of temperature and of its effects around the laser applicator could be useful to define optimal laser settings. The aims of this work are temperature monitoring and measurement of ablated tissue volume in an ex vivo porcine pancreas undergoing double-applicator LITT. A three-dimensional numerical model is implemented to predict temperature rise and volumes of ablated tissue in treated pancreas. Experiments are performed to validate the model, with two modalities: (1) 12-fiber Bragg grating sensors are adopted to monitor the heating and cooling during LITT at several distances from the applicators tip, and (2) 1.5-T MR imaging is used to estimate the ablated volume. Experimental data agree with theoretical ones: at 2 mm from both applicators tips, the maximum temperature increase is approximately 60°C downward from the tips, while it increases of about 40°C and 30°C, respectively, at the level and upward from the tips. This behavior occurs also at other distances, proving that the tissue downward from the tip is mostly heated. Furthermore, the estimated volume with MRI agrees with theoretical one (i.d., 0.91±0.09 vs. 0.95 cm 3). The encouraging results indicate that the model could be a suitable tool to choose the optimal laser settings, in order to control the volume of ablated tissue. © 2013 Springer-Verlag.

Since the inception of radiosurgery, the management of brain metastases has become a common problem for neurosurgeons. Although the use of stereotactic radiosurgery and/or whole brain radiation therapy serves to control the majority of disease burden, patients who survive longer than 6-8 months sometimes face the problem of symptomatic radiographically regrowing lesions with few treatment options. Here we investigate the feasibility of use of MRI-guided stereotactic laser induced thermotherapy (LITT) as a novel treatment option for these lesions. Six patients who had previously undergone gamma knife stereotactic radiosurgery for brain metastases were selected. All patients had an initial favorable response to radiosurgery but subsequently developed regrowth of at least one lesion associated with recurrent edema and progressive neurological symptoms requiring ongoing steroids for symptom control. All lesions were evaluated for craniotomy, but were deemed unresectable due to deep location or patient's comorbidities. Stereotactic biopsies were performed prior to the thermotherapy procedure in all cases. LITT was performed using the Visualase system and follow-up MRI imaging was used to determine treatment response. In all six patients biopsy results were negative for tumor and consistent with adverse radiation effects also known as radiation necrosis. Patients tolerated the procedure well and were discharged from the hospital within 48 h of the procedure. In 4/6 cases there was durable improvement of neurological symptoms until death. In all cases steroids were weaned off within 2 months. One patient died from systemic causes related to his cancer a month after the procedure. One patient had regrowth of the lesion 3 months after the procedure and required re-initiation of steroids and standard craniotomy for surgical resection. There were no complications directly related to the thermocoagulation procedure. Stereotactic laser induced thermotherapy is a feasible alternative for the treatment of symptomatic regrowing metastatic lesions after radiosurgery. The procedure carries minimal morbidity and, in this small series, shows some effectiveness in the symptomatic relief of edema and neurological symptoms paralleled by radiographic lesional control. Further studies are necessary to elucidate the safety of this technology.

The purpose of this study is to retrospectively evaluate local tumor control, time to tumor progression, and survival rates among patients with lung metastatic colorectal cancer who have undergone ablation therapy performed using laser-induced thermotherapy (LITT), radiofrequency ablation (RFA), or microwave ablation (MWA).Data for this retrospective study were collected from 231 CT-guided ablation sessions performed for 109 patients (71 men and 38 women; mean [± SD] age, 68.6 ± 11.2 years; range, 34-94 years) from May 2000 to May 2014. Twenty-one patients underwent LITT (31 ablations), 41 patients underwent RFA (75 ablations), and 47 patients underwent MWA (125 ablations). CT scans were acquired 24 hours after each therapy session and at follow-up visits occurring at 3, 6, 12, 18, and 24 months after ablation. Survival rates were calculated from the time of the first ablation session, with the use of Kaplan-Meier and log-rank tests. Changes in the volume of the ablated lesions were measured using the Kruskal-Wallis method.Local tumor control was achieved in 17 of 25 lesions (68.0%) treated with LITT, 45 of 65 lesions (69.2%) treated with RFA, and 91 of 103 lesions (88.3%) treated with MWA. Statistically significant differences were noted when MWA was compared with LITT at 18 months after ablation (p = 0.01) and when MWA was compared with RFA at 6 months (p = 0.004) and 18 months (p = 0.01) after ablation. The overall median time to local tumor progression was 7.6 months. The median time to local tumor progression was 10.4 months for lesions treated with LITT, 7.2 months for lesions treated with RFA, and 7.5 months for lesions treated with MWA, with no statistically significant difference noted. New pulmonary metastases developed in 47.6% of patients treated with LITT, in 51.2% of patients treated with RFA, and in 53.2% of patients treated with MWA. According to the Kaplan-Meier test, median survival was 22.1 months for patients who underwent LITT, 24.2 months for those receiving RFA, and 32.8 months for those who underwent MWA. The overall survival rate at 1, 2, and 4 years was 95.2%, 47.6%, and 23.8%, respectively, for patients treated with LITT; 76.9%, 50.8%, and 8.0%, respectively, for patients treated with RFA; and 82.7%, 67.5%, and 16.6%, respectively, for patients treated with MWA. The log-rank test revealed no statistically significant difference among LITT, RFA, and MWA. The progression-free survival rate at 1, 2, 3, and 4 years was 96.8%, 52.7%, 24.0%, and 19.1%, respectively, for patients who underwent LITT; 77.3%, 50.2%, 30.8%, and 16.4%, respectively, for patients who underwent RFA; and 54.6%, 29.1%, 10.0%, and 1.0%, respectively, for patients who underwent MWA, with no statistically significant difference noted among the three ablation methods.LITT, RFA, and MWA can be used as therapeutic options for lung metastases resulting from colorectal cancer. Statistically significant differences in local tumor control revealed a potential advantage in using MWA. No differences in time to tumor progression or survival rates were detected when the three different ablation methods were compared.

Background and Objective Magnetic resonance-guided laser-induced thermotherapy (MR-LITT) is a minimally invasive technique that shows promise in neuro-oncology because of its superiority in delivering precise minimally invasive thermal energy with minimal collateral damage. In this analysis, we investigate initial data on the effect of MR-LITT on dural-based lesions. Methods Five patients were identified with dural-based lesions (4 meningiomas, 1 solitary fibrous tumor) with clear evidence of radiologic progression. In all 5 cases, the tumors were localized to the lateral convexity or paramedian locations in the supratentorial space. All patients received MR-LITT and then a follow-up magnetic resonance imaging scan at 24 hours after treatment, at 1 month, and at each subsequent follow-up visit. Local control of the ablated tumor was evaluated with radiographic follow-up and symptomatic progression-free survival was recorded. Results Five LITT treatments were performed on 5 patients with an average age of 65.2 years. The average tumor volume was 29.7 cm 3 and ablation dosage was 12.4 W. On average, 80% of the pretreatment lesion volume was ablated. The mean follow-up time was 59.3 weeks. In total, 2 patients (1 with an anaplastic meningioma and 1 with a solitary fibrous tumor) had radiographic evidence of disease progression. In the observed time of the 3 patients with no progression, there was a 52% reduction in tumor volume. There were no major perioperative complications. Conclusions MR-LITT is a promising technology for dural-based lesion treatment. This initial study demonstrates that MR-LITT is safe and offers several advantages over open surgical treatment. Randomized studies are needed to evaluate its role as a treatment adjunct.

The purpose of the study was to develop a simulation approach for laser-induced thermotherapy (LITT) that is based on mathematical models for radiation transport, heat transport, and tissue damage. The LITT ablation was applied to ex vivo pig liver tissue. Experiments were repeated with different laser powers, i.e., 22-34 W, and flow rates of the cooling water in the applicator system, i.e., 47-92 ml/min. During the procedure, the temperature was measured in the liver sample at different distances to the applicator as well as in the cooling circuit using a fiber optic thermometer. For validation, the simulation results were compared with the results of the laser ablation experiments in the ex vivo pig liver samples. The simulated and measured temperature curves presented a relatively good agreement. The Bland-Altman plot showed an average of temperature differences of -0.13 ∘C and 95%-limits-of-agreement of ±7.11 ∘C. The standard deviation amounted to ±3.63 ∘C. The accuracy of the developed simulation is comparable with the accuracy of the MR thermometry reported in other clinical studies. The simulation showed a significant potential for the application in treatment planning.

Background: To evaluate a treatment protocol with repeated transarterial-chemoembolisation (TACE) downsizing before MR-guided laser-induced interstitial thermotherapy (LITT) using different chemotherapeutic combinations in patients with unresectable colorectal cancer (CRC) liver metastases. Methods: Two hundred and twenty-four patients were included in the current study. Transarterial-chemoembolisation (mean 3.4 sessions per patient) was performed as a downsizing treatment to meet the LITT requirements (number⩽5, diameter

Purpose To evaluate MR-thermometry using fast MR sequences for laser induced interstitial thermotherapy (LITT) at 0.2 and 1.5 T systems. Methods & Materials In-vitro experiments were performed using Agarose gel mixture and lobes of porcine liver. MR-thermometry was performed by means of longitudinal relaxation time (T1) and proton resonance frequency shift (PRF) methods under acquisition of amplitude and phase shift images. Four different sequences were used for T1 thermometry: A gradient-echo (GRE), a True Fast Imaging with Steady Precession (TRUFI), a Saturation Recovery Turbo-FLASH (SRTF), and an Inversion Recovery Turbo-FLASH (IRTF) sequence (FLASH—Fast Low Angle Shot). PRF was measured with four sequences: Two fast-spoiled GRE sequences (one as WIP sequence), a Turbo-FLASH (TFL) sequence (WIP sequence), and a multiecho-TrueFISP sequence. Temperature was controlled and verified using a fiber-optic Luxtron device. The temperature was correlated with the MR measurement. Results All sequences showed a good linear correlation R2 = 0.97–0.99 between the measured temperature and the MR-thermometry measurements. The only exception was the TRUFI sequence in the Agarose phantom that showed a non-linear calibration curve R2 = 0.39–0.67. At 1.5 T, the Agarose experiments revealed similar temperature accuracies of 4–6°C for all sequences excluding TRUFI. During experiments with the liver, the PRF sequences showed better performance than the T1, with accuracies of 5–12°C, contrary to the T1 sequences at 14–18°C. The accuracy of the Siemens PRF-FLASH sequence was 5.1°C. At 0.2 T, the Agarose experiments provided the highest accuracy of 3.3°C for PRF measurement. At the liver experiments the T1 sequences SRTF and FLASH revealed the best accuracies at 6.4 and 7.0°C. Conclusion The accuracy and speed of MR temperature measurements are sufficient for controlling the temperature-based tumor destruction. For 0.2 T systems SRTF and FLASH sequences are recommended. For 1.5 T systems SRTF and FLASH are the most accurate. Lasers Surg. Med. 44:257–265, 2012. © 2012 Wiley Periodicals, Inc.

The method to investigation the changes of optical properties and evaluating the effect of laser application in real time is presented in this paper. In vivo measurements of the reduced scattering coefficient (μ’s) and tissue temperature (T) were performed with a functional near infrared spectroscopy (fNIRS) system and a temperature measurement system during LITT. Mice liver tumors were examined in vivo in different laser doses (0.8W, 1.0W, 1.2W, 1.4W) at a certain heating time (600s). The results showed that there were the same rising tendencies of the reduced scattering coefficient and temperature during LITT. They increased quickly at the beginning, gradually reached a stable state, and rose faster when the laser power was greater. When the tissue temperature was in the range of 50°C to 70°C, there was a clear linear relationship between μ’s and T. The linear equation was obtained for the first time.

Minimally invasive treatment options for liver tumor therapy have been increasingly used during the last decade because their benefit has been proven for primary and inoperable secondary liver tumors. Among these, radiofrequency ablation has gained widespread consideration. Optimal image-guidance offers precise anatomical information, helps to position interventional devices, and allows for differentiation between already-treated and remaining tumor tissue. Patient safety and complete ablation of the entire tumor are the overriding objectives of tumor ablation. These may be achieved most elegantly with magnetic resonance (MR)-guided therapy, where monitoring can be performed based on precise soft-tissue imaging and additional components, such as diffusion-weighted imaging and temperature mapping. New MR scanner types and newly developed sequence techniques have enabled MR-guided intervention to move beyond the experimental phase. This article reviews the current role of MR imaging in guiding radiofrequency ablation. Signal characteristics of primary and secondary liver tumors are identified, and signal alteration during therapy is described. Diffusion-weighted imaging (DWI) and temperature mapping as special components of MR therapy monitoring are introduced. Practical information concerning coils, sequence selection, and parameters, as well as sequence gating, is given. In addition, sources of artifacts are identified and techniques to decrease them are introduced, and the characteristic signs of residual tumor in T1-, T2-, and DWI are described. We hope to enable the reader to choose MR sequences that allow optimal therapy monitoring depending on the initial signal characteristics of the tumor as well as its size and location in the liver.

Alternative minimally invasive treatment options such as radiofrequency ablation (RFA) or laser-induced thermotherapy (LITT) are at present under investigation for achieving a nonsurgical targeted cytoreduction in benign and malignant thyroid lesions. So far, studies have not been able to show a secure advantage for neither LITT nor RFA. The aim of this study was to compare the two ablation procedures in terms of their effectiveness. Thermal lesions were induced in porcine thyroid glands either by LITT or bipolar RFA ex vivo (n = 110 each) and in vivo (n = 10 each) using power settings between 10 and 20 W. Temperature spread during application was documented in 5- and 10-mm distance of the applicator. Postinterventional lesion diameters were measured and lesion size was calculated. Furthermore, enzyme histochemical analysis of the thyroid tissue was performed in vivo. Lesion volumes induced by LITT ranged between 0.74 ± 0.18 cm(3) (10 W) and 3.80 ± 0.41 cm(3) (20 W) with a maximum of 5.13 ± 0.16 cm(3) at 18 W. The inducible lesion volumes by RFA were between 2.43 ± 0.68 cm(3) (10 W) and 0.91 ± 0.71 cm(3) (20 W) with a maximum of 2.80 ± 0.85 cm(3) at 14 W. The maximum temperatures were 112.9 ± 9.2°C (LITT) and 61.6 ± 13.9°C (RFA) at a distance of 5 mm and 73.2 ± 6.7°C (LITT) and 53.5 ± 8.6°C (RFA) at a distance of 10 mm. The histochemical analysis demonstrates a complete loss of NADPH dehydrogenase activity in thermal lesions as a sign of irreversible cell damage both for LITT and RFA. This study is the first to compare the effectiveness of laser-induced thermotherapy and radiofrequency ablation of thyroid tissue. LITT as well as RFA are suitable for singular thyroid nodules and induces reproducible clinically relevant lesions in an appropriate application time. The maximum inducible lesion volumes by LITT are significantly larger than by RFA with the devices used herein.

In situ ablation is increasingly being used for the treatment of liver malignancies. The application of these techniques is limited by the lack of a precise prediction of the destruction volume. This holds especially true in anatomically difficult situations, such as metastases in the vicinity of larger liver vessels. We developed a three-dimensional (3D) planning system for laser-induced thermotherapy (LITT) of liver tumors. The aim of the study was to validate the system for calculation of the destruction volume.LITT (28 W, 20 min) was performed in close contact to major hepatic vessels in six pigs. After explantation of the liver, the coagulation area was documented. The liver and its vascular structures were segmented from a pre-interventional CT scan. Therapy planning was carried out including the cooling effect of adjacent liver vessels. The lesions in vivo and the simulated lesions were compared with a morphometric analysis.The volume of lesions in vivo was 6,568.3 ± 3,245.9 mm(3), which was not different to the simulation result of 6,935.2 ± 2,538.5 mm(3) (P = 0.937). The morphometric analysis showed a sensitivity of the system of 0.896 ± 0.093 (correct prediction of destructed tissue). The specificity was 0.858 ± 0.090 (correct prediction of vital tissue).A 3D computer planning system for the prediction of thermal lesions in LITT was developed. The calculation of the directional cooling effect of intrahepatic vessels is possible for the first time. The morphometric analysis showed a good correlation under clinical conditions. The pre-therapeutic calculation of the ablation zone might be a valuable tool for procedure planning.

Purpose: To assess the feasibility, precision, and accuracy of real-time temperature mapping (TMap) during laser-induced thermotherapy (LITT) for clinical practice in patients liver with a gradient echo (GRE) sequence using the proton resonance frequency (PRF) method. Materials and Methods: LITT was performed on 34 lesions in 18 patients with simultaneous real-time visualization of relative temperature changes. Correlative contrast-enhanced T1-weighted magnetic resonance (MR) images of the liver were acquired after treatment using the same slice positions and angulations as TMap images acquired during LITT. For each slice, TMap and follow-up images were registered for comparison. Afterwards, segmentation based on temperature (T) >52°C on TMap and based on necrosis seen on follow-up images was performed. These segmented structures were overlaid and divided into zones where the TMap was found to either over- or underestimate necrosis on the postcontrast images. Regions with T>52°C after 20 minutes were defined as necrotic tissue based on data received from two different thermal dose models. Results: The average intersecting region of TMap and necrotic zone was 87% ± 5%, the overestimated 13% ± 4%, and the underestimated 13% ± 5%. Conclusion: This study demonstrates that MR temperature mapping appears reasonably capable of predicting tissue necrosis on the basis of indicating regions having greater temperatures than 52°C and could be used to monitor and adjust the thermal therapy appropriately during treatment. J. Magn. Reson. Imaging 2011;33:704–712. © 2011 Wiley-Liss, Inc.

The purpose of this study was to evaluate local tumor control and survival after use of a downstaging protocol of repeated transarterial chemoembolization (TACE) with two chemotherapeutic combinations followed by laser-induced thermotherapy in the care of patients with liver metastasis of breast cancer.This prospective study included 161 patients with liver metastasis of breast cancer origin. TACE (mean, 3.5 [SD, 1.3] sessions per patient; range, 1-9 sessions) was performed as downstaging treatment to achieve the size and number of metastatic lesions that met the requirements for laser-induced thermotherapy (diameter5 cm, number ≤ 5). The TACE protocol was performed with either mitomycin C alone (n = 53) or mitomycin C in combination with gemcitabine (n = 108).In response to TACE overall, the mean reduction in diameter based on the longest diameter of the target lesions was 27%. The difference between diameter reduction in the mitomycin C group and that in the mitomycin C-gemcitabine group was not statistically significant (p = 0.65). The mean survival time of all patients was 32.5 months, calculation starting from the first TACE treatment. The mean local tumor control period calculated as of completion of therapy was 13 months, and the mean time to progression was 8 months. In the mitomycin-gemcitabine group, mean time to progression was 10.7 months, and in the mitomycin group it was 6.9 months (p = 0.5).TACE can be used for sufficient downstaging of liver metastatic lesions of breast cancer to allow laser-induced thermotherapy. A combination of mitomycin C and gemcitabine seems to improve the reduction achieved with TACE.

Der vorliegende Beitrag stellt interventionelle Therapieverfahren auf der Basis thermischer Ablationsverfahren wie Radiofrequenzablation (RFA), laserinduzierte Thermotherapie (LITT) und Mikrowellenablation (MWA) fur die palliative Therapie von malignen primaren und sekundaren Leber- und Lungentumoren vor. Er befasst sich mit der vergleichenden Bewertung der lokalen Tumorkontrollraten, Langzeituberlebensraten (LUR), das progressionsfreie Uberleben („progression-free survival“, PFS) und Komplikationen. Bei Lebermetastasen des kolorektalen Karzinoms (CRC) liegen die Daten fur RFA, LITT und MWA fur die lokale Tumorkontrollrate bei jeweils ca. 85%, 95% und 93%, die LUR bei 22, 37 und 32 Monaten und das PFS bei 84, 97 und 93 Monaten. Neue Studien zeigen verbesserte Ergebnisse bei Kombinationen mit systemischer und regionaler Chemotherapie (TACE). Seltenere Indikationen fur die Thermoablation stellen lokale Rezidive von Kopf-Hals-Malignomen, Lymphknoteninfiltrationen und Beckenneoplasien dar.

To evaluate the feasibility and safety of a novel LITT applicator for thermal ablation of liver malignancies in 1.0-T high-field open MRI.A miniaturised 6-F double-tubed protective catheter with a closed cooling circuit was used with a flexible laser fibre, connected to a 1,064-nm Nd:YAG laser and evaluated in non-perfused porcine livers (18-30 W for 10-20 min, 2-W and 2-min increments; n = 210/applicator) in reference to an established 9-F system. As a proof of concept, MR-guided LITT was performed in two healthy domestic pigs in high-field open MRI.Ex-vivo, the coagulation volumes induced by the 6-F system with maximum applicable power of 24 W for 20 min (33.0 ± 4.4 cm(3)) did not differ significantly from those set with the 9-F system at 30 W for 20 min (35.8 ± 4.9 cm(3)) (p = 0.73). A flow-rate of 15 ml/min of the cooling saline solution was sufficient. MR navigation and thermometry were feasible.The miniaturised 6-F applicator can create comparable coagulation sizes to those of the 9-F system. Applicator guidance and online-thermometry in high-field open MRI are feasible.

The objective of our study was to use perfusion CT to prospectively monitor early vascular changes in tumor perfusion of pulmonary metastases after laser-induced thermotherapy (LITT) and to determine whether any of the perfusion parameters would predict technical success after therapy.Twelve patients with histologically proven pulmonary metastases undergoing LITT were enrolled prospectively in this study. Perfusion CT was performed before treatment, 1 day after treatment, and 4-6 weeks after therapy, and tumor blood flow, tumor blood volume (TBV), mean transit time (MTT), and permeability of the capillary wall surface (capillary permeability-surface product) in 22 pulmonary metastases were calculated. Perfusion parameters at baseline and after LITT were compared. Measurement of tumor diameter on long-term follow-up CT was the gold standard with which perfusion CT results were compared for local control.Median tumor blood flow, TBV, and capillary permeability-surface product had decreased significantly from baseline by 43%, 61%, and 73%, respectively, 1 day after LITT. Perfusion parameters obtained 4-6 weeks after treatment had not changed significantly compared with those obtained 1 day after therapy. There seems to be a good correlation between changes in perfusion CT parameters 1 day after therapy and local outcome, according to the Response Evaluation Criteria in Solid Tumors (RECIST), 1 year after therapy.Perfusion CT of pulmonary metastases has potential in the assessment of early vascular changes that result from LITT and predicting technical success immediately after treatment. Tumors with perfusion measurements that had not changed after therapy indicated progressive disease.

This paper presents a nonlinear dual-reciprocity boundary element method (DRBEM) for bioheat transfer in laser-induced thermotherapy. The nonlinearity stems from the dynamic changes of tissue thermophysical and optical properties and the blood perfusion rate during laser heating. The proposed DRBEM is coupled with a modified Monte Carlo method and the Arrhenius rate equation to investigate laser light propagation, bioheat transfer, and irreversible thermal damage in tumors. The computer code is justified by comparing the DRBEM results with the finite-difference results. The photothermal processes in interstitial laser thermotherapy with single or double laser fiber scattering applicators are chosen as the demonstrative examples. The dynamic nature, together with the unique advantages of "boundary-only" and excellent adaptability to complex anatomical geometries that the DRBEM method offers, makes the present nonlinear DRBEM a powerful tool for analysis and optimization of the parameters in laser surgical procedure.

AIM: This article reports on the use of magnetic resonance imaging to access the post-interventional necrosis volume of liver metastases immediately after and 48 hours after LITT. MATERIAL AND METHODS: In this prospective study, 56 liver metastases from 39 patients (16 females, 23 males, mean age 60.4 years) underwent LITT. The 56 metastases were divided into 4 groups according to the ablation strategy (dependent on multi-applicator technique and laser duration). Groups I and II were treated with an applicator and a time of ablation greater than 15 minutes and 20 minutes, respectively. In groups III and IV the multi-applicator technology with 3 or 4 applicators and a constant ablation time of 20 minutes were used. With the help of heightened contrast MRI of the liver, the portrayal of the post-interventional necrosis was conducted immediately after LITT and 48 hours after LITT. The post-interventional controls after 48 hours were performed during the inpatient stay. The protocol was complemented by an outpatient long-term control after more than 3 months. RESULTS: The local tumor control rate was initially 96.4 %. After 3 months it decreased to 92.1 %. The mean necrosis volume directly after LITT was: Group I (n = 11; 1 applicator, 30 watt, 10 - 15 minutes) 6.69 cm 3 ; Group II (n = 13; 1 applicator, 30 watt, 20 minutes) 10.95 cm 3 ; Group III (n = 28; 2 applicator, 30 watt, 10 - 15 minutes) 21.47 cm 3 ; Group IV (n = 4; 3 applicator, 30 watt, 20 minutes) 40.20 cm 3 . In comparison, the necrosis volume after 48 hours increased: Group I 10.56 cm 3 ; Group II 15.11 cm 3 ; Group III 31.33 cm 3 , Group IV 55.73 cm 3 ). CONCLUSION: After 48 hours a progressive increase of post-interventional necrosis volumes compared to volumes directly after LITT was able to be observed. An MRI control after 48 hours, as opposed to an MRI control directly after intervention, is a better indicator for post-interventional success after LITT.

Laser-induced thermotherapy (LITT) is a minimally invasive laser hyperthermia procedure for the treatment of localized tumors. Mathematical modeling of the photothermal processes in laser-irradiated tissues is essential for optimal treatment planning. In this study, A Monte Carlo method is introduced to simulate photon transport in the tumor tissues with complex geometries. The dual reciprocity boundary element method (DRBEM) is then formulated to solve the bioheat transfer equation in the tumors. The model is validated with the finite difference solutions. To illustrate the applications of the proposed DRBEM, several laser delivery schemes, including external laser irradiation, single or multiple laser fiber delivery applicators, are studied for tumors with regular or irregular geometric shapes. The temperature transients, laser energy distribution and coagulation patterns for different laser delivery modes are demonstrated. The unique advantages of the DRBEM, such as easy adaptability to complex tumor geometries and no need to discretize the inner domain, may make it well-suited and robust approach for predicting and controlling the temperature evolution in laser-induced thermotherapy procedure.

Object Developments in open magnetic resonance imaging (MRI) magnets have made possible the use of reproducible thermosensitive sequences to determine temperature distribution inside biological tissue. This study aimed to compare MR thermal mapping during laser-induced interstitial thermal therapy (LITT) with macroscopically observed thermal lesions in order to estimate the 3D size of the coagulative necrosis.

a DRK Kliniken Westend, Berlin , Germany; b UFR Bichat-Beaujon-Louis Mourier, Service de Chirurgie Digestive, Hopital Louis Mourier, Colombes , France; c Medicine and Surgery, General Surgery Section, MED/18 – General Surgery and d Department of Pathology, University of Verona, Verona , Italy; e Netherlands Cancer Centre, Amsterdam , and f Department of Nuclear Medicine, Erasmus University Medical Center, Rotterdam , The Netherlands

Thermal ablation techniques like radiofrequency or laser-induced thermotherapy (LITT) are increasingly used to treat tumors of parenchymatous organs. Minimal access, parenchymal preservation, and a low complication rate render them suitable for pulmonary tumors as well. Their successful clinical application depends on the induction of sufficiently large lesions and a knowledge of the energy parameters required for complete thermal ablation. The aim of this study was to establish a dose-response relationship for a percutaneous and an intraoperative system for LITT of lung tissue. Thermal lesions were induced in healthy porcine lungs using an Nd:YAG laser (1,064 nm). LITT was performed with a percutaneous application system in group I (n = 18) and an intraoperative application system in group II (n = 90). Laser energy was applied for 600-1,200 s in a power range of 20-32 W (12,000-38,400 J). The lesions were longitudinally and transversally measured, and the volume was calculated after the intervention. Furthermore, an open application system was used to perform LITT under in vivo conditions during lung perfusion and ventilation in domestic pigs. Lesion volumes in both groups showed a plateau-like curve when the laser power increased from an initial level of 25 W. With the percutaneous puncture system (group I), the application of 28 W (16,800 J) for 10 min generated the largest lesions with a volume of 12.54 +/- 1.33 cm(3), an axial diameter of 39.33 +/- 2.52 mm, and a diametrical diameter of 24.67 +/- 1.15 mm. A longer application time was not possible due to thermal instability of the applicator. Moreover, group I started developing extensive carbonizations at a laser power of 22 W (13,200 J). The intraoperative application system (group II) achieved the largest lesion volumes of 11.03 +/- 2.54 cm(3) with diameters of 34.6 +/- 4.22 mm (axial) and 25.6 +/- 2.51 mm (diametrical) by an exposure time of 20 min and a power of 32 W (38,400 J). Here extensive carbonizations only started to occur at 28 W (33,600 J). Under in vivo conditions, all pigs tolerated the LITT procedure well without complications. Besides a typical cooling effect in the vicinity of blood vessels, the thermal lesions were about three times smaller than the ex vivo lesions. Both the percutaneous and the open LITT application system induced reproducible, clinically relevant lung lesions. The percutaneous puncture set generated large relevant lesions, although its usability is limited by its restricted capacity and high carbonization risk. It is suitable for powers up to 22 W. The intraoperative application system allows higher energy exposure to induce larger lesion volumes. This study elucidates the dose-effect relation of two clinically relevant puncture sets.

PURPOSE: Evaluation of thermometry with fast MR sequences for laser-induced interstitial laser therapy (LITT) and verification of the thermometric results with a fiber-optic thermometer. METHOD AND MATERIALS: In vitro experiments were conducted using an agarose gel mixture and pig liver lobes. MR-guided LITT was performed using a laser power between 3 and 15 watts. Thermometry was performed using longitudinal relaxation time T1 and proton resonance frequency shift (PRF) methods under acquisition of amplitude and phase shift images. PRF was measured with a fast spoiled GRE sequence. Four different sequences were used for T1 thermometry: gradient echo (GE), TrueFISP (TRUFI), Saturation Recovery Turbo-FLASH (SRTF) and Inversion Recovery Turbo-FLASH (IRTF) sequences. The temperature was controlled using a fiber-optic Luxtron device and correlated with the MR temperature. The range of applied and monitored temperatures exceeded 80 degrees Celsius. RESULTS: The temperature dependence showed a good linear relationship up to 60 degrees Celsius. Calibration experiments for the T1 method delivered coefficients of determination from 0.977 to 0.997 for agarose and from 0.958 to 0.995 for the pig liver samples. The IRTF sequence had the highest temperature sensitivity (agarose 0.99, liver 1.19). During LITT the TRUE-FISP sequence exhibited a strong nonlinear relationship. R 2 of this sequence was 0.809 in the agarose experiments. The average temperature errors when heated up to 80 degrees Celsius were 3.86 - 11.38 degrees Celsius for Agarose gel and 5.7 - 12.16 degrees Celsius for the liver tissue. SRTF and IRTF sequences exhibited the most linear relationship with temperature but were more dependent on tissue differences. CONCLUSION: The accuracy of the temperature measurement is sufficient for controlling the coagulation area of the LITT. PRF is the method of choice since it shows the best linear correlation with fiber-optic temperature. If only T1 sequences are concerned, the FLASH sequence is preferred. It is the most robust, though not the most accurate, T1 sequence.

The purpose of this article is to present in a concise manner an overview of the most widely used locoregional transcatheter and ablative therapies for solid malignancies. An extensive MEDLINE search was performed for this review. Therapies used for liver cancer were emphasized because these therapies are used most commonly in the liver. Applications in pulmonary, renal, and bone tumors were also discussed. These approaches were divided into catheter-based therapies (such as transcatheter arterial chemoembolization, bland embolization, and the most recent transcatheter arterial approach with drug-eluting microspheres), ablative therapies (such as chemical [ethanol or acetic acid injection]), and thermal ablative therapies (such as radiofrequency ablation, laser induced thermotherapy, microwave ablation, cryoablation, and extracorporeal high-intensity focused ultrasound ablation). A brief description of each technique and analysis of available data was reported for all therapies. Locoregional transcatheter and ablative therapies continue to be used mostly for palliation, but have also been used with curative intent. A growing body of evidence suggests clear survival benefit, excellent results regarding local tumor control, and improved quality of life. Clinical trials are underway to validate these results. Image-guided transcatheter and ablative approaches currently play an important role in the management of patients with various types of cancer—a role that is likely to grow even more given the technological advances in imaging, image-guidance systems, catheters, ablative tools, and drug delivery systems. As a result, the outcomes of patients with cancer undoubtedly will improve.

Background and Objectives Proliferation and synthesis of hepatocellular tissue after tissue damage are promoted by specific growth factors such as hepatic tissue growth factor (HGF) and connective growth factor (CTGF). Laser-induced thermotherapy (LITT) for the treatment of liver metastases is deemed to be a parenchyma-saving procedure compared to hepatic resection. The aim of this study was to compare the impact of LITT and hepatic resection on intrahepatic residual tumor tissue and expression levels of mRNA HGF/CTGF within liver and tumor tissue. Study Design/Materials and Methods Two independent adenocarcinomas (CC531) were implanted into 75 WAG rats, one in the right (untreated tumor) and one in the left liver lobe (treated tumor). The left lobe tumor was treated either by LITT or partial hepatectomy. The control tumor was submitted to in-situ hybridization of HGF and CTGF 24–96 hours and 14 days after intervention. Results Volumes of the untreated tumors prior to intervention were 38±8 mm3 in group I (laser), 39 ± 7 mm3 in group II (resection), and 42 ± 12 mm3 in group III (control) and did not differ significantly (P > 0.05). Fourteen days after the intervention the mean tumor±SEM volume of untreated tumor in group I (laser) [223 ± 36] was smaller than in group II (resection) [1233.28 ± 181.52; P

Laser-induced thermotherapy (LITT), i.e. tissue destruction induced by a local increase of temperature by means of laser light energy transmission, has been frequently used for minimally invasive treatments of various diseases such as benign thyroid nodules and liver cancer. The emerging photoacoustic (PA) imaging, when integrated with ultrasound (US), could contribute to LITT procedure. PA can enable a good visualization of percutaneous apparatus deep inside tissue and, therefore, can offer accurate guidance of the optical fibers to the target tissue. Our initial experiment demonstrated that, by picking the strong photoacoustic signals generated at the tips of optical fibers as a needle, the trajectory and position of the fibers could be visualized clearly using a commercial available US unit. When working the conventional US Bscan mode, the fibers disappeared when the angle between the fibers and the probe surface was larger than 60 degree; while working on the new PA mode, the fibers could be visualized without any problem even when the angle between the fibers and the probe surface was larger than 75 degree. Moreover, with PA imaging function integrated, the optical fibers positioned into the target tissue, besides delivering optical energy for thermotherapy, can also be used to generate PA signals for on-line evaluation of LITT. Powered by our recently developed PA physio-chemical analysis, PA measurements from the tissue can provide a direct and accurate feedback of the tissue responses to laser ablation, including the changes in not only chemical compositions but also histological microstructures. The initial experiment on the rat liver model has demonstrated the excellent sensitivity of PA imaging to the changes in tissue temperature rise and tissue status (from native to coagulated) when the tissue is treated in vivo with LITT.

In situ ablation of colorectal liver metastases is frequently assessed for palliative treatment only. The establishment of clinically relevant lesion size and a lack of long-term survival data were regarded as main limitations to using them with curative intention. In contrast to surgical liver resection, whose oncological findings seem to have remained unchanged over the years, the in situ ablation methods have considerably changed technically and clinically in the last few years.The aim of the paper was to point out experimental and clinical data underlining the impact of in situ ablation for potentially curative treatment of colorectal liver metastases.On the basis of experimental data, the aim of complete local tumor control (R0 ablation) can only be obtained if additional energy is applied after reaching the tumor-adapted maximal coagulation volume. Analogous to the oncological safety margin in surgical resection, we defined this decisive energy difference as the "energy safety margin" for in situ ablation. The energy safety margin is the energy that must be additionally applied after reaching the plateau in the energy/volume curve to achieve complete tumor coagulation. In addition to that, in situ ablation should be combined with temporary interruption of hepatic perfusion whenever possible to prevent intralesional recurrences. In this way, the thermoprotective mechanism of hepatic perfusion can be effectively eliminated. With restrictions, the survival data after ablation in specialized centers is comparable to surgical resection with concomitantly lower morbidity and mortality. Based on recent findings and with the corresponding expertise in the field of ablation and state-of-the-art equipment, ablation is, thus, an alternative to surgical resection. The combined application of surgical resection and ablation is also a suitable method for increasing the R0 rate and thus helps improve the prognosis of treated patients. In summary, it can be said that in situ ablation is a useful expansion of the therapeutic spectrum of liver metastases and can be applied as an alternative to or in combination with surgical resection.