Search

Downloading of the abstract is permitted for personal use only. Photoablative laser therapy is in common use for selective destruction of malignant masses, vascular and brain abnormalities. Tissue ablation and coagulation are irreversible processes occurring shortly after crossing a certain thermal exposure threshold. As a result, accurate mapping of the temperature field is essential for optimizing the outcome of these clinical interventions. Here we demonstrate four-dimensional optoacoustic temperature mapping of the entire photoablated region. Accuracy of the method is investigated in tissue-mimicking phantom experiments. Deviations of the volumetric optoacoustic temperature readings provided at 40ms intervals remained below 10% for temperature elevations above 3°C, as validated by simultaneous thermocouple measurements. The excellent spatio-temporal resolution of the new temperature monitoring approach aims at improving safety and efficacy of laser-based photothermal procedures.

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.

An analysis of the use of minimally invasive interventions - laser-induced thermotherapy (LITT), ethanol destruction (ED) under ultrasound guidance, a combination of these methods in the treatment of сystic-col- loidal nodes (CCN) of thyroid nodules in 120 patients. ED carried out in 31 patients with cystic destruction of a site of more than 70%. Marked decrease in the average volume with 4.68 ± 2.25 cm3 to 1.15 ± 0.9 cm3. In 4 patients remained cystic cavity of small size, which required a combination of LITT (CombiLITT). Nine patients underwent LITT solid residue of more than 1 cm3. The average size of nodules within 6 months after the primary surgery was 0.9 ± 0.3 cm3. СombiLITT performed in 42 patients with cystic cavity from 20 to 70%. The volume of units decreased from 7.98 ± 4.56 to 1.87 ± 0.9 cm3. After 3 months, 11 patients with the size of a solid residue of more than 1 cm3 held LITT. All of them when viewed after 3 months observed decrease of more than 50%. LITT performed 23 patients with major nodes and cystic cavities less than 20% of the node. Marked decrease in the amount of nodes with 2.89 ± 1.25 cm3 to 1.42 ± 0.8 cm3. Retesting LITT took 2 patients. After 6 months, the average amount of units was 0.7 ± 0.2 cm3 LITT conducted in 24 patients with small cystic nodes to 1 cm3. Marked decrease in size from 0.69 ± 0.23 cm3 to 0.29 ± 0.12 cm3. Varied selection of minimally inva- sive treatment of CCN is effective and in most cases, to achieve reduction of the size of nodes.

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.

Specialized gold nanostructures are of interest for the development of alternative treatment methods in medicine. Photothermal therapy combined with gene therapy that supports hyperthermia is proposed as a novel multimodal treatment method for prostate cancer. In this work, photothermal therapy using small (

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.

This work is based on the production of a bioprobe that is compatible with magnetic resonance imaging (MRI) for laser-induced thermotherapy (LITT) in liver cancer laser therapy. This probe is made of an alumina tube (3-mm diameter) in which an optical fibre is centred and fixed. A shooting window (20mm) is created using a mechanical rectifier. The device is then consolidated by the injection of a transparent and heat-resistant resin. Through numerical modelling, the thermal power damping of the laser source is evaluated as well as the propagation of the heat in the ex vivo liver tissue according to different heating scenarios. These analyses allow for an estimation of the irradiated volume. Ex vivo tests were performed on bovine liver to confirm the adequacy of the bioprobe for LITT and of the irradiated volumes predicted by the numerical model. There was a difference of 8% between the simulations and ex vivo experiments. The pulsed mode heating scenario was the most effective under the experimental conditions.

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.

MRI was recognized for its potential use as a noninvasive in vivo thermometer 30 years ago. Today, the most popular application of MR thermometry is the guidance of thermal therapies for the treatment of cancer and other pathologies. These minimally invasive operations are routinely performed on patients who are not eligible for surgery in approximately 40 medical centers globally. The aim is to deliver or abduct thermal energy in order to cause local tissue necrosis or to sensitize a lesion to chemotherapy or radiotherapy without causing harm to the surrounding healthy tissue. Here we explain the principles of operation of MR thermometry and provide a critical review of the proposed methods, highlighting remaining fundamental and technical issues as well as recent progress. Emphasis is placed on hardware advances (RF receivers) for improved signal-to-noise ratio (SNR) which would lead to better accuracy, spatiotemporal resolution, and precise calibration. We conclude with a general outlook for the field.

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.

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.

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

The paper compares two different approaches to design an innovative probe with optimized heated area for laser ablation of solid tumors: micro-patterning of the fiber delivery tip, and exploitation of the dissipation of plasmonic waves at the metal-dielectric interface. Both probes integrate a fiber Bragg grating for real- time monitoring of the obtained temperature increase to provide feedback to surgeons in practical applications. Experimental characterizations carried out using liver phantoms and ex-vivo porcine livers have demonstrated that both approaches can be used for the devised application, although further optimizations and tests are still necessary before clinical assessment.

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.

Background and Objectives The therapeutic application of laser light is a promising alternative to surgical resection of colorectal liver metastases. The extent of tumor destruction achieved by this strategy depends primarily on light distribution in the target tissue. Knowledge about optical properties is necessary to predict light distribution in the tissue for careful irradiation planning. The aim of this study was to compare the optical behavior of healthy colon tissue with that of colorectal carcinomas and their hepatic metastases in the native and coagulated state in order to test the effect of malignant degeneration, metastasis, and thermal coagulation on optical parameters. Materials and Methods Ninety tissue samples were taken from patients with a colorectal carcinoma and concomitant liver metastases: healthy colon tissue (n = 30); colon carcinoma (n = 30); liver metastases (n = 30). Optical properties were measured according to the single integrating sphere principle in the native state and after thermal coagulation in the wavelength range of 800–1,100 nm and analyzed by inverse Monte Carlo simulation. Results The highest optical penetration depth for all tissue types was obtained at the end of the spectral range investigated. The highest penetration depths of 4.13 mm (healthy colon), 7.47 mm (colon carcinoma tissue), and 4.08 (liver metastases) were at 1,060 nm, although the values decreased significantly after thermal coagulation. Comparing healthy colon-to-colon carcinoma always revealed a significantly lower absorption and scattering coefficient in the tumor tissue. This resulted in a higher optical penetration depth of the laser light in the colon carcinoma tissue (P

Background Focal heat destruction has emerged as an effective treatment strategy in selected patients with malignant liver tumors. Radiofrequency ablation, interstitial laser thermotherapy, and microwave treatment are currently the most widely applied thermal ablative techniques. A major limitation of these therapies is incomplete tumor destruction and overall high recurrences. An understanding of the mechanisms of tissue injury induced by focal hyperthermia is essential to ensure more complete tumor destruction. Here, the currently available scientific literature concerning the underlying mechanisms involved in the destruction of liver tumors by focal hyperthermia is reviewed. Methods Medline was searched from 1960 to 2004 for literature regarding the use of focal hyperthermia for the treatment of liver tumors. All relevant literature was searched for further references. Results Experimental evidence suggests that focal hyperthermic injury occurs in two distinct phases. The first phase results in direct heat injury that is determined by the total thermal energy applied, tumor biology, and the tumor microenvironment. Tumors are more susceptible to heat injury than normal cells as the result of specific biological features, reduced heat dissipating ability, and lower interstitial pH. The second phase of hyperthermic injury is indirect tissue damage that produces a progression of tissue injury after the cessation of the initial heat stimulus. This progressive injury may involve a balance of several factors, including apoptosis, microvascular damage, ischemia–reperfusion injury, Kupffer cell activation, altered cytokine expression, and alterations in the immune response. Blood flow modulation and administration of thermosensitizing agents are two methods currently used to increase the extent of direct thermal injury. The processes involved in the progression of thermal injury and therapies that may potentially modulate them remain poorly understood. Conclusion Focal hyperthermia for the treatment of liver tumors involves complex mechanisms. Evidence suggests that focal hyperthermia produces both direct and indirect tissue injury by differing underlying processes. Methods to enhance the effects of treatment to achieve complete tumor destruction should focus on manipulating these processes.

PURPOSE: To assess the effect of laser-induced thermotherapy (LITT) on liver metastases of various size from colon carcinoma in an animal model. MATERIALS AND METHODS: Liver metastases were implanted in 20 Wistar Albino Glaxo (WAG) rats by subcapsular injection of cells from a colorectal strain (CC531) (day 0). The animals were divided into two groups with regard to the measured tumor size of 0.05 - 0.06 cm (3) (group A) and 0.10 - 0.12 cm (3) (group B). On day 14 after laparotomy, the tumors were exposed to 1064 nm Nd:YAG laser light at 2 watts for 5 minutes after intratumoral placement of the laser applicator set. The tumor volumes before (V1, at day 13) and after treatment (V2, at day 28) were determined by MRI and the mean tumor growth ratio (V2/V1) was calculated. RESULTS: The mean tumor volumes V1 and V2 were 0.05 +/- 0.003 cm (3) and 0.23 +/- 0.016 cm (3) in group A, and 0.11 +/- 0.006 cm (3) and 0.68 +/- 0.037 cm (3) in group B. The mean tumor growth ratio (V2/V1) was 4.31 +/- 0.19 in group A and 6.11 +/- 0.14 in group B. The mean volume of the induced necrosis (0.15 +/- 0.01 cm (3)) was the same for both groups ( p > 0.05). Compared to group B, liver metastases of group A showed a significant slower tumor growth velocity (paired t-test, p < 0.0001). CONCLUSION: The interventional treatment of large hepatic tumors with LITT leads to faster tumor growth compared to smaller lesions.

Purpose: To investigate whether laser-induced thermotherapy (LITT) for tumors of the liver in central location is a sufficient and safe therapeutic option. Material and Methods: According to predefined criteria, 23 of 136patients were chosen to be treated with LITT because of malignant liver tumors. At the time of the first LITT, the patients had 28 central tumors (27 metastases, one HCC), which were treated in 34 sessions with 64 laser applications and had a clinical and imaging follow-up every 3 months. Results: The primary effectiveness rate was 74.1% and the secondary effectiveness rate 82.1 %. The mortality rate was 0%. Major complications occurred in one patient (hemorrhagic pleural effusion), while minor complications occurred in 10 patients. During the median follow-up of 20 months (range 3-57 months), local tumor progression developed in 22% of the tumors. The effectiveness rate was 78.6%, 71.4% and 64.3% after 3, 6 and 9 months. The median survival was 46.0 months (95 % confidence interval: 28.6-47.1 months). Conclusion: In our patients, complications and ablation rate of laser-induced thermotherapy for central liver tumors do not differ from those in peripheral location as described in the literature.

Background and Objectives In contrast to hepatic resection, thermally destroyed autologous tumor cells remain in situ after laser-induced thermotherapy (LITT). The aim of the study was to evaluate the effect of LITT and hepatic resection on the immune response to residual intrahepatic tumor tissue and the growth of untreated liver metastases. Study Design/Materials and Methods Two independent adenocarcinomas (CC531) were implanted into 60 WAG rats, one in the right (control 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 further investigation 24 hours, 96 hours, 7 days, and 10 days after treatment. Results Ten days after treatment, control tumor volumes were 296±46 mm_ after LITT and 1,181±192 mm_, 1,387±200 mm_ after hepatic resection and no treatment, respectively (P

Tissue vasculature plays an important role in the temperature responses of biological bodies subject to laser heating. For example, interfaces between blood vessel and its surrounding tissues may lead to reflection or absorption of the coming laser light. However, most of the previous efforts just treat this by considering a collective model. To date, little attention has been paid to the effect of a single blood vessel on tissue temperature prediction during laser-induced thermotherapy. To resolve this important issue in clinics, we propose to simultaneously solve the three-dimensional (3-D) light and heat transport in several typical tissue domains with either one single blood vessel or two countercurrent blood vessels running through. Both surface and intervenient laser irradiations are considered in these studies. The 3-D heat transfer and blood flow models are established to characterize the temperature transients over the whole area. Coupled equations for heat and blood flow in multiple regions are ...

Summary Laser-induced thermotherapy (LITT) is an established minimally invasive technique which has been proven to be successful for many years, especially in the treatment of liver metastases. The lung is the organ most affected by metastases, next to the liver. Many patients do not meet the criteria of inclusion for metastasectomy which is considered the gold standard (3, 4). LITT could be a safe and effective alternative for these inoperable patients. In case of bilateral lung disease, segmental excision or lobectomy can be complemented by LITT of solitary focuses in other lobes. For a successful therapy management of lung metastases, lesion sizes are required for creating situations comparable to RO excision. For this purpose, the dose-effect relation between the applied Nd:YAG laser power and the coagulation size attainable was investigated for a clinically established applicator system. The tests were made ex vivo on porcine lungs using a LITT puncture set for open surgery. The laser power ranging from 20 to 32 watts was applied to the tissue through an internally cooled diffusor-tip applicator. The induced coagulation lesions were measured for volumes and maximum extensions. While the tested LITT system proved to be suitable for application with powers up to 32 watts, its maximum efficacy had been reached already at 25 watts and an exposure time of 20 minutes. Higher powers did not generate substantially larger lesions, but caused a temperature holdup and subsequent carbonisation. The data on the dose-effect relation obtained by this study contribute essentially to clinical application and lay the ground for a safe and validated therapy control.

Summary The head and neck area includes a multitude of small, complexly arranged anatomic structures; intimate knowledge of normal spatial relationships and variations is necessary to plan and implement appropriate therapy. Lesions often lie near vital structures, complicating diagnostic and therapeutic procedures. Improved visualization using MRI during such procedures can therefore provide the physician with critical information and is permitting innovative procedures. However, palliative treatment options for recurrent head and neck cancer are limited by the proximity of vital vascular and neural structures and the aggressive nature of these tumors. Depending from the localization of the recurrent tumor a minimally invasive treatment modality such as interventional MR-guided laser-induced thermotherapy offers a potential treatment benefits. This paper is describing the indications and technique of MR-guided LITT using a Nd:YAG laser (1064 nmm) for the treatment of recurrent head and neck tumors.

Summary Objectives: Evaluation of technical aspects, side-effects, complications and results of percutaneous MR-guided LITT in lung metastases. Material and methods: The technique of laser-induced thermotherapy (LITT) is presented. Computed tomography (CT) or magnetic resonance imaging (MRI) are used to control the insertion of the catheter in the patients. For LITT a specially cooled application system was developed. Percutaneous LITT was performed in 34 metastases of 26 patients. Inclusion criteria were metastases ≤3 cm in diameter in unresectable patients. Results: In our patient group, all patients tolerated the LITT procedure well under mild sedation. The pneumothorax rate was 8% (3/34 procedures). Local tumor control rate in the 6-month period was 91%. 95% of the patients treated are still alive. Conclusion: Pulmonary LITT allows a safe thermal ablation of lung metastases ≤3 cm in diameter with an acceptable tumor control rate.

Summary Objectives: To evaluate the clinical value of neoadjuvant transarterial chemoembolization (TACE) before MR-guided laser-induced thermotherapy (LITT) for different large-sized liver tumors. Materials and methods : Repeated TACE were performed in 289 patients (mean 4.1 per patient) with unresectable HCC (n = 48) or liver metastases (n = 241) in a neoadjuvant intention using 10 mg/m 2 mitomycin as chemotherapeutic agent and 10 ml/m 2 lipiodol and microspheres for vessel occlusion. Tumor volume was measured by MR-imaging. As soons as the diameter of the tumor was observed to have decreased to less than 50 mm, the patients were treated with MRI-guided LITT 4 to 6 weeks after embolization. Survival rates of the different liver tumors of the combined protocol were compared to the results of the patients who were treated only with TACE or with the results of the patients who were treated directly with LITT. Results: In the neoadjuvant group repeated TACE enabled a reduction in tumor size and tumor perfusion in 166 patients (80 cases of metastases of colorectal cancer, 39 cases of metastases of breast cancer, 12 cases of metastases of other primary tumors, 3 cases of carcinoids and 32 cases of HCC), forming the basis of the performance of 322 (mean 2.0) MR-guided LITT procedures. The median survival period for patients with HCC was after the first treatment 25.0 months for the TACE group, 33.3 months for the LITT group and was statistically significant higher with 36.0 months in the patients with the combined treatment. In contrast to this the median survival for patients with colorectal liver metastases was 15.2 months for the TACE group, 23.6 months for the neoadjuvant treated patients and 32.6 months for the patients treated only with LITT. Conclusion: The combined treatment protocol (TACE followed by MR-guided LITT) appears to be a safe and effective treatment of large unresectable liver tumors. The combination of TACE and LITT results in significant superior survival rates in comparison to the results of TACE alone. HCC showed a better response to the treatment than liver metastases.

To evaluate a treatment protocol with repeated transarterial chemoembolization (TACE) before laser-induced thermotherapy (LITT) in patients with unresectable liver metastases that are too large for LITT alone.One hundred sixty-two patients who had unresectable liver metastases, with the largest lesion as large as 80 mm in diameter, and no more than four lesions were treated with repeated TACE between March 1999 and December 2001. TACE was performed with a maximum of 10 mg/m2 mitomycin for chemotherapy and a maximum of 15 mL/m2 of iodized oil and microspheres for vessel occlusion. Tumor volume before and during treatment was measured at magnetic resonance (MR) imaging. If the diameter of the tumor decreased to less than 50 mm, the patients were treated with MR imaging-guided LITT 4-6 weeks following embolization.Eighty-two patients (62 with metastases from colorectal cancer, 14 with metastases from breast cancer, and six with metastases from other primary tumors) responded to TACE, with a mean reduction in tumor size of 35% +/- 14 (SD), and were treated with LITT. Each patient underwent two to seven TACE treatments (mean, 4.3) prior to LITT. In 47 patients, no reduction in tumor size was achieved, which led to further follow-up. In 33 patients, disease progression was found, with either an increasing size of the lesions (n = 18) or newly developing metastases (n = 15), and these results led to further TACE treatments or change to systemic chemotherapy. Median survival of patients who responded to this combined treatment was 26.2 months; in patients treated with only TACE, median survival was 12.8 months (range, 0.3-29.4 months).With repeated TACE, reduction in size of primary unresectable hepatic metastases is achieved in 50.6% of cases and allows local ablative treatments such as MR imaging-guided LITT.

The paper presents our recent results towards the development of a miniaturized all-fiber probe for laser induced thermal ablation of tumor cells, which combines the optimal delivery of a near-infrared high power ablating beam, a low power visible aiming beam and fast Bragg grating (FBG) temperature sensors. Specific combiner and probe end-cap based on dual cladding fibers have been developed to allow the simultaneous handling of the laser beams and of the signal that feeds the temperature sensor. Moreover, a very fast FBG interrogation system has been implemented to track abrupt temperature variations during medical treatment.

We report a case of a 52-year-old woman with a palpable recurrent metastasis of a neuroendocrine carcinoma to the upper outer quadrant of the right breast. For the treatment of this lesion, MR-guided laser-induced thermotherapy was performed with a cooled power laser system (Nd:YAG-Laser). An open 0.2-T MR unit was used for the monitoring of the laser energy delivery to the breast; thus, a thermosensitive fast low-angle shot 2D sequence for MR thermometry was used, so the ablation of the tumor and the increase of laser-induced necrosis could be interactively visualized with the repetitive use of this sequence. The postinterventional MR control exams 1 day and 4 months after laser-induced thermotherapy at the 1.5-T MR unit (Magnetom Symphony Quantum, Siemens, Erlangen, Germany) verified the complete ablation of the tumor without any signs of residual or relapsing tumor.

PURPOSE Demonstration of techniques and clinical value of imaging diagnostics for screening, detection, interventional follow-up and therapy control of hepatocellular carcinoma (HCC). Diagnostic techniques for screening, detection and differential diagnosis of HCC are presented using color-coded duplex sonography (US), computer tomography (CT) and contrast-enhanced magnetic resonance techniques like MRI, MR angiography and MR cholangiopancreaticography (MRCP). Therapy control with imaging was performed for surgical methods like resection and liver transplantation as for well as transarterial chemoembolization (TACE), radiofrequency ablation (RF) and laser-induced thermotherapy (LITT). In screening, HCC color-coded duplex sonography reveals a sensitivity from 45 to 92 % and a specificity from 78 to 90 % when liver cirrhosis is present. The diagnostic results of CT were further improved with the newly developed techniques of multislice CT. The highest diagnostic accuracy can currently be achieved using contrast-enhanced MRI with a sensitivity from 82 to 96 %. TACE presents a palliative therapy concept; MR-guided LITT and radiofrequency ablation are used as thermoablative methods for local therapy and the therapy control is based on the above imaging techniques. Contrast-enhanced MRI proves to be the superior imaging technique for the early diagnosis, differential diagnosis and follow-up of hepatocellular carcinoma.

AIM Evaluation of sonography in the placement of catheters for laser-induced thermotherapy (LITT) as well as for the observation of the therapeutic procedure in cases of malignant liver tumours. METHODS Following the placement of 1-4 LITT applicators, 18 patients with malignant liver tumours (recurrence of hepatocellular carcinoma n = 5, metachronous liver metastases n = 13) were examined by ultrasound to determine the position of the applicators as well as the sonographic visualisation of the respective lesion. The laser treatment procedure was also observed sonographically. As standard reference method for the documentation of thermally induced necroses we used magnetic resonance tomography 24-48 hours after the procedure. RESULTS The tip of the applicator could be localised in all cases, and the position of the applicator relative to the lesion could be directly visualised in 78% of cases. The hyperechogenic thermal effect during LITT had a median size of 4.5 cm, thus proving to be significantly larger than the actual necrosis induced (p < 0.01). The sonographic observation of the procedure identified 8/10 primarily incomplete ablations which were then treated again immediately after correction of the position of the applicators. CONCLUSION Continuous sonographic observation of the procedure of LITT can yield important additional information.

Background and Objective The aim of this study was to evaluate the accuracy of Gd-DTPA MRI in the detection of recurrent tumor after laserinduced thermotherapy (LITT) of experimental liver metastases. Study Design/Materials and Methods LITT was performed at different energy levels in VX-2 tumor-bearing rabbits (n = 80). MRI and histology were placed at 0, 24, 96 hours, and 14 days. Signal intensities were calculated of the transition between thermally damaged and undamaged tissue (transition zone = TZ) and of the surrounding tissue (reference zone = RZ). Results Tumor recurrence was seen in 47 animals. At 24 hours sensitivity, specificity and accuracy was 92, 100, and 95% in TZ and 23, 100, and 50% in RZ. At 14 days sensitivity, specificity and accuracy was 100, 11, and 60% in TZ and 100, 89, and 95% in RZ. Conclusions Recurrence is best excluded in TZ at 24 hour and in RZ at 14 day with an accuracy up to 95%. Lasers Surg. Med. 30:280–289, 2002. © 2002 Wiley-Liss, Inc.