Thermal Ablation (thermal + ablation)

Distribution by Scientific Domains
Distribution within Medical Sciences


Selected Abstracts


IMPACT OF BLOOD FLOW OCCLUSION ON LIVER NECROSIS FOLLOWING THERMAL ABLATION

ANZ JOURNAL OF SURGERY, Issue 1-2 2006
Mehrdad Nikfarjam
Background: Laser, radiofrequency and microwave are common techniques for local destruction of liver tumours by thermal ablation. The main limitation of thermal ablation treatment is the volume of necrosis that can be achieved. Blood flow occlusion is commonly advocated as an adjunct to thermal ablation to increase the volume of tissue necrosis based on macroscopic and histological assessment of immediate or direct thermal injury. This study examines the impact of blood flow occlusion on direct and indirect laser induced thermal liver injury in a murine model using histochemical methods to assess tissue vitality. Methods: Thermal ablation produced by neodymium yttrium-aluminium-garnet laser (wavelength 1064 nm) was applied to the liver of inbred male CBA strain mice at 2 W for 50 s (100 J). Treatment was performed with and without temporary portal vein and hepatic artery blood flow occlusion. Animals were killed upon completion of the procedure to assess direct thermal injury or at 24, 48 and 72 h to assess the progression of tissue damage. The maximum diameter of necrosis was assessed by vital staining for nicotinamide adenine dinucleotide (NADH) diaphorase. Microvascular changes were assessed by laser Doppler flowmetry, confocal in vivo microscopy and scanning electron microscopy. Results: The direct thermal injury (mean SE) assessed by NADH diaphorase staining was significantly greater following thermal ablation treatment without blood flow occlusion than with blood flow occlusion (3.3 (0.4) mm vs 2.9 (0.3) mm; P = 0.005). Tissue disruption, cracking and vacuolization was more pronounced adjacent to the fibre insertion site in the group treated with thermal ablation combined with blood flow occlusion. There was an equivalent increase in the extent of injury following therapy in both groups that reached a peak at 48 h. The maximum diameter of necrosis in the thermal ablation alone group at 48 h was significantly greater than the thermal ablation combined with blood flow occlusion group (5.8 (0.4) mm vs 5.3 (0.3) mm; P = 0.011). The patterns of microvascular injury were similar in both groups, varying in extent. Conclusion: Temporary blood flow inflow occlusion appears to decrease the extent of initial injury measured by vital staining techniques and does not alter the time sequence of progressive tissue injury following thermal ablation therapy. [source]


Evaluation of Radiofrequency Thermal Ablation Results in Inferior Turbinate Hypertrophies by Magnetic Resonance Imaging

THE LARYNGOSCOPE, Issue 4 2007
Tarik Sapci MD
Abstract Objectives: Nasal obstruction caused by inferior turbinate hypertrophies is one of the most frequent problems in otolaryngology. Treatment of this disease may involve medical and surgical methods. Thermal ablation with radiofrequency energy has become quite popular in the recent years as one of the surgical methods used when medical therapy is not adequate. Study Design: Prospective, clinical trial. Methods: Thermal ablation with radiofrequency energy was used in this study on the inferior turbinates of 21 patients who had nasal obstruction caused by inferior turbinate hypertrophy only. The results were evaluated subjectively by preoperative and postoperative patient- and physician-assigned visual analogue scales and objectively by magnetic resonance imaging (MRI) investigation. Results: By the end of the postoperative week 10, 64.76% recovery was detected according to the patient evaluation, and 40.75% recovery was detected according to the physician evaluation. Measurement of the average volumes of the inferior turbinates by MRI revealed a 8.70% postoperative reduction. The most significant change was detected in the anterior-posterior length measurement performed in the axial plane. Conclusions: These results suggest that thermal ablation with radiofrequency energy is an easily applied, efficient, and reliable technique in treatment of the inferior turbinate hypertrophy, and that anterior-posterior length measurement in the axial section of the inferior turbinate by MRI, which is thought as an objective evaluation method, could be an efficient diagnostic tool in detecting the efficiency of radiofrequency on inferior turbinate. [source]


IMPACT OF BLOOD FLOW OCCLUSION ON LIVER NECROSIS FOLLOWING THERMAL ABLATION

ANZ JOURNAL OF SURGERY, Issue 1-2 2006
Mehrdad Nikfarjam
Background: Laser, radiofrequency and microwave are common techniques for local destruction of liver tumours by thermal ablation. The main limitation of thermal ablation treatment is the volume of necrosis that can be achieved. Blood flow occlusion is commonly advocated as an adjunct to thermal ablation to increase the volume of tissue necrosis based on macroscopic and histological assessment of immediate or direct thermal injury. This study examines the impact of blood flow occlusion on direct and indirect laser induced thermal liver injury in a murine model using histochemical methods to assess tissue vitality. Methods: Thermal ablation produced by neodymium yttrium-aluminium-garnet laser (wavelength 1064 nm) was applied to the liver of inbred male CBA strain mice at 2 W for 50 s (100 J). Treatment was performed with and without temporary portal vein and hepatic artery blood flow occlusion. Animals were killed upon completion of the procedure to assess direct thermal injury or at 24, 48 and 72 h to assess the progression of tissue damage. The maximum diameter of necrosis was assessed by vital staining for nicotinamide adenine dinucleotide (NADH) diaphorase. Microvascular changes were assessed by laser Doppler flowmetry, confocal in vivo microscopy and scanning electron microscopy. Results: The direct thermal injury (mean SE) assessed by NADH diaphorase staining was significantly greater following thermal ablation treatment without blood flow occlusion than with blood flow occlusion (3.3 (0.4) mm vs 2.9 (0.3) mm; P = 0.005). Tissue disruption, cracking and vacuolization was more pronounced adjacent to the fibre insertion site in the group treated with thermal ablation combined with blood flow occlusion. There was an equivalent increase in the extent of injury following therapy in both groups that reached a peak at 48 h. The maximum diameter of necrosis in the thermal ablation alone group at 48 h was significantly greater than the thermal ablation combined with blood flow occlusion group (5.8 (0.4) mm vs 5.3 (0.3) mm; P = 0.011). The patterns of microvascular injury were similar in both groups, varying in extent. Conclusion: Temporary blood flow inflow occlusion appears to decrease the extent of initial injury measured by vital staining techniques and does not alter the time sequence of progressive tissue injury following thermal ablation therapy. [source]


Association of ablation of Barrett's esophagus with high grade dysplasia and adenocarcinoma of the gastric cardia

DISEASES OF THE ESOPHAGUS, Issue 4 2006
R. E. Sampliner
SUMMARY., There has been increasing application of endoscopic ablation therapy for patients with high-grade dysplasia (HGD) and Barrett's esophagus (BE). Three cases are reported in which the patient developed adenocarcinoma of the gastric cardia after thermal ablation of HGD. A definition of BE including endoscopic abnormality and intestinal metaplasia by biopsy was used. Strict and standardized criteria were utilized for the endoscopic landmarks. Three cases are reported with long-segment BE and a nodule or mass in the endoscopic cardia post-thermal ablation. Biopsies documented adenocarcinoma of the gastric cardia. The development of adenocarcinoma of the cardia is unexpected. Speculation is offered as to the potential of increased proliferation and mutations at the new squamocolumnar interface after endoscopic ablation therapy to explain this association. [source]


Specific thermal ablation of tumor cells using single-walled carbon nanotubes targeted by covalently-coupled monoclonal antibodies

INTERNATIONAL JOURNAL OF CANCER, Issue 12 2009
Radu Marches
Abstract CD22 is broadly expressed on human B cell lymphomas. Monoclonal anti-CD22 antibodies alone, or coupled to toxins, have been used to selectively target these tumors both in SCID mice with xenografted human lymphoma cell lines and in patients with B cell lymphomas. Single-walled carbon nanotubes (CNTs) attached to antibodies or peptides represent another approach to targeting cancer cells. CNTs convert absorbed near-infrared (NIR) light to heat, which can thermally ablate cells that have bound the CNTs. We have previously demonstrated that monoclonal antibodies (MAbs) noncovalently coupled to CNTs can specifically target and kill cells in vitro. Here, we describe the preparation of conjugates in which the MAbs are covalently conjugated to the CNTs. The specificity of both the binding and NIR-mediated killing of the tumor cells by the MAb-CNTs is demonstrated by using CD22+CD25, Daudi cells, CD22,CD25+ phytohemagglutinin-activated normal human peripheral blood mononuclear cells, and CNTs covalently modified with either anti-CD22 or anti-CD25. We further demonstrate that the stability and specificity of the MAb-CNT conjugates are preserved following incubation in either sodium dodecyl sulfate or mouse serum, indicating that they should be stable for in vivo use. 2009 UICC [source]


Current status and future potential of MRI-guided focused ultrasound surgery

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2008
Ferenc A. Jolesz MD
Abstract The combination of the imaging abilities of magnetic resonance imaging (MRI) with the ability to delivery energy to targets deep in the body noninvasively with focused ultrasound presents a disruptive technology with the potential to significantly affect healthcare. MRI offers precise targeting, visualization, and quantification of temperature changes and the ability to immediately evaluate the treatment. By exploiting different mechanisms, focused ultrasound offers a range of therapies, ranging from thermal ablation to targeted drug delivery. This article reviews recent preclinical and tests clinical of this technology. J. Magn. Reson. Imaging 2008;27:391,399. 2008 Wiley-Liss, Inc. [source]


Design and development of a prototype endocavitary probe for high-intensity focused ultrasound delivery with integrated magnetic resonance imaging

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2007
Iain P. Wharton MRCS
Abstract Purpose To integrate a high intensity focused ultrasound (HIFU) transducer with an MR receiver coil for endocavitary MR-guided thermal ablation of localized pelvic lesions. Materials and Methods A hollow semicylindrical probe (diameter 3.2 cm) with a rectangular upper surface (7.2 cm 3.2 cm) was designed to house a HIFU transducer and enable acoustic contact with an intraluminal wall. The probe was distally rounded to ease endocavitary insertion and was proximally tapered to a 1.5-cm diameter cylindrical handle through which the irrigation tubes (for transducer cooling) and electrical connections were passed. MR compatibility of piezoceramic and piezocomposite transducers was assessed using gradient-echo (GRE) sequences. The radiofrequency (RF) tuning of identical 6.5 cm 2.5 cm rectangular receiver coils on the upper surface of the probe was adjusted to compensate for the presence of the conductive components of the HIFU transducers. A T1-weighted (T1-W) sliding window dual-echo GRE sequence monitored phase changes in the focal zone of each transducer. High-intensity (2400 W/cm,2), short duration (<1.5 seconds) exposures produced subtherapeutic temperature rises. Results For T1-W images, signal-to-noise ratio (SNR) improved by 40% as a result of quartering the conductive surface of the piezoceramic transducer. A piezocomposite transducer showed a further 28% improvement. SNRs for an endocavitary coil in the focal plane of the HIFU trans-ducer (4 cm from its face) were three times greater than from a phased body array coil. Local shimming improved uniformity of phase images. Phase changes were detected at subtherapeutic exposures. Conclusion We combined a HIFU transducer with an MR receiver coil in an endocavitary probe. SNRs were improved by quartering the conductive surface of the piezoceramic. Further improvement was achieved with a piezocomposite transducer. A phase change was seen on MR images during both subtherapeutic and therapeutic HIFU exposures. J. Magn. Reson. Imaging 2007. 2007 Wiley-Liss, Inc. [source]


Ex vivo and in vivo evaluation of laser-induced thermotherapy for nodular thyroid disease

LASERS IN SURGERY AND MEDICINE, Issue 7 2009
Jrg-P.
Abstract Background and Objective The prevalence of thyroid nodules ranges between 2% and 60% depending on the population studied. However, minimally invasive procedures like laser-induced thermotherapy (LITT) are increasingly used to treat tumors of parenchymatous organs and seem to be suitable for singular thyroid nodules 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 LITT of thyroid nodules. Materials and Methods Thermal lesions were induced in healthy porcine thyroid glands ex vivo (n,=,110) and in vivo (n,=,10) using an Nd:YAG laser (1,064,nm). Laser energy was applied for 300,seconds in a power range of 10,20,W. During the ablation, continuous temperature measurement at a distance of 5 and 10,mm from the applicator was performed. The lesions were longitudinally and transversally measured, and the volume was calculated. Furthermore, enzyme histochemical analysis of the thyroid tissue was performed. Results The maximum inducible lesion volumes were between 0.74,,0.18,cm3 at a laser power of 10,W and 3.80,,0.41,cm3 at 20,W. The maximum temperatures after ablation were between 72.9,,2.9C (10,W) and 112.9,,9.2C (20,W) at a distance of 5,mm and between 49.5,,2.2C (10,W) and 73.2,,6.7C (20,W) at a distance of 10,mm from the applicator. The histochemical analysis demonstrates a complete loss of NADPH dehydrogenase activity in thermal lesions as a sign of irreversible cell damage. Conclusions This study is the first to demonstrate a dose,response relationship for LITT of thyroid tissue. LITT is suitable for singular thyroid nodules and induces reproducible clinically relevant lesions with irreversible cell damage in an appropriate application time. Lasers Surg. Med. 41:479,486, 2009. 2009 Wiley-Liss, Inc. [source]


Real-time MR temperature mapping of rabbit liver in vivo during thermal ablation

MAGNETIC RESONANCE IN MEDICINE, Issue 2 2003
Claudia Weidensteiner
Abstract It has been shown that quantitative MRI thermometry using the proton resonance frequency (PRF) method can be used to noninvasively monitor the evolution of tissue temperature, and to guide minimally-invasive tumor ablation based on local hyperthermia. Although hepatic tumors are among the main targets for thermal ablation, PRF-based temperature MRI of the liver is difficult to perform because of motion artifacts, fat content, and low T. In this study the stability of real-time thermometry was tested on a clinical 1.5 T scanner for rabbit liver in vivo. The fast segmented EPI principle was used together with respiratory gating to limit respiratory motion artifacts. Lipid signal suppression was achieved with a binomial excitation pulse. Saturation slabs were applied to suppress artifacts due to flowing blood. The respiratory-gated MR thermometry in the rabbit liver in vivo showed a standard deviation (SD) of 1,3C with a temporal resolution of 3 s per slice and 1.4 mm 1.9 mm spatial resolution in plane (slice thickness = 5 mm). The method was used to guide thermal ablation experiments with a clinical infrared laser. The estimated size of the necrotic area, based on the thermal dose calculated from MR temperature maps, corresponded well with the actual lesion size determined by histology and conventional MR images obtained 5 days posttreatment. These results show that quantitative MR temperature mapping can be obtained in the liver in vivo, and can be used for real-time control of thermal ablation and for lesion size prediction. Magn Reson Med 50:322,330, 2003. 2003 Wiley-Liss, Inc. [source]


Extent of thermal ablation suffered by model organic microparticles during aerogel capture at hypervelocities

METEORITICS & PLANETARY SCIENCE, Issue 10 2009
M. J. Burchell
Commercial polystyrene particles (20 ,m diameter) were coated with an ultrathin 20 nm overlayer of an organic conducting polymer, polypyrrole. This overlayer comprises only 0.8% by mass of the projectile but has a very strong Raman signature, hence its survival or destruction is a sensitive measure of the extent of chemical degradation suffered. After aerogel capture, microparticles were located via optical microscopy and their composition was analyzed in situ using Raman microscopy. The ultrathin polypyrrole overlayer survived essentially intact for impacts at ,1 km s,1, but significant surface carbonization was found at 2 km s,1, and major particle mass loss at ,3 km s,1. Particles impacting at ,6.1 km s,1 (the speed at which cometary dust was collected in the NASA Stardust mission) were reduced to approximately half their original diameter during aerogel capture (i.e., a mass loss of 84%). Thus significant thermal ablation occurs at speeds above a few km s,1. This suggests that during the Stardust mission the thermal history of the terminal dust grains during capture in aerogel may be sufficient to cause significant processing or loss of organic materials. Further, while Raman D and G bands of carbon can be obtained from captured grains, they may well reflect the thermal processing during capture rather than the pre-impact particle's thermal history. [source]


Evaluation of Radiofrequency Thermal Ablation Results in Inferior Turbinate Hypertrophies by Magnetic Resonance Imaging

THE LARYNGOSCOPE, Issue 4 2007
Tarik Sapci MD
Abstract Objectives: Nasal obstruction caused by inferior turbinate hypertrophies is one of the most frequent problems in otolaryngology. Treatment of this disease may involve medical and surgical methods. Thermal ablation with radiofrequency energy has become quite popular in the recent years as one of the surgical methods used when medical therapy is not adequate. Study Design: Prospective, clinical trial. Methods: Thermal ablation with radiofrequency energy was used in this study on the inferior turbinates of 21 patients who had nasal obstruction caused by inferior turbinate hypertrophy only. The results were evaluated subjectively by preoperative and postoperative patient- and physician-assigned visual analogue scales and objectively by magnetic resonance imaging (MRI) investigation. Results: By the end of the postoperative week 10, 64.76% recovery was detected according to the patient evaluation, and 40.75% recovery was detected according to the physician evaluation. Measurement of the average volumes of the inferior turbinates by MRI revealed a 8.70% postoperative reduction. The most significant change was detected in the anterior-posterior length measurement performed in the axial plane. Conclusions: These results suggest that thermal ablation with radiofrequency energy is an easily applied, efficient, and reliable technique in treatment of the inferior turbinate hypertrophy, and that anterior-posterior length measurement in the axial section of the inferior turbinate by MRI, which is thought as an objective evaluation method, could be an efficient diagnostic tool in detecting the efficiency of radiofrequency on inferior turbinate. [source]


IMPACT OF BLOOD FLOW OCCLUSION ON LIVER NECROSIS FOLLOWING THERMAL ABLATION

ANZ JOURNAL OF SURGERY, Issue 1-2 2006
Mehrdad Nikfarjam
Background: Laser, radiofrequency and microwave are common techniques for local destruction of liver tumours by thermal ablation. The main limitation of thermal ablation treatment is the volume of necrosis that can be achieved. Blood flow occlusion is commonly advocated as an adjunct to thermal ablation to increase the volume of tissue necrosis based on macroscopic and histological assessment of immediate or direct thermal injury. This study examines the impact of blood flow occlusion on direct and indirect laser induced thermal liver injury in a murine model using histochemical methods to assess tissue vitality. Methods: Thermal ablation produced by neodymium yttrium-aluminium-garnet laser (wavelength 1064 nm) was applied to the liver of inbred male CBA strain mice at 2 W for 50 s (100 J). Treatment was performed with and without temporary portal vein and hepatic artery blood flow occlusion. Animals were killed upon completion of the procedure to assess direct thermal injury or at 24, 48 and 72 h to assess the progression of tissue damage. The maximum diameter of necrosis was assessed by vital staining for nicotinamide adenine dinucleotide (NADH) diaphorase. Microvascular changes were assessed by laser Doppler flowmetry, confocal in vivo microscopy and scanning electron microscopy. Results: The direct thermal injury (mean SE) assessed by NADH diaphorase staining was significantly greater following thermal ablation treatment without blood flow occlusion than with blood flow occlusion (3.3 (0.4) mm vs 2.9 (0.3) mm; P = 0.005). Tissue disruption, cracking and vacuolization was more pronounced adjacent to the fibre insertion site in the group treated with thermal ablation combined with blood flow occlusion. There was an equivalent increase in the extent of injury following therapy in both groups that reached a peak at 48 h. The maximum diameter of necrosis in the thermal ablation alone group at 48 h was significantly greater than the thermal ablation combined with blood flow occlusion group (5.8 (0.4) mm vs 5.3 (0.3) mm; P = 0.011). The patterns of microvascular injury were similar in both groups, varying in extent. Conclusion: Temporary blood flow inflow occlusion appears to decrease the extent of initial injury measured by vital staining techniques and does not alter the time sequence of progressive tissue injury following thermal ablation therapy. [source]


Percutaneous radiofrequency thermoablation as an alternative to surgery for treatment of liver tumour recurrence after hepatectomy

BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 6 2002
Dr D. Elias
Background: Radiofrequency (RF) current, converted into heat through ion agitation and friction, can destroy liver tumours by means of coagulation necrosis. This study assessed whether percutaneous RF ablation is a useful and safe technique for the treatment of liver tumour recurrence after hepatectomy. Methods: Forty-seven patients presenting with local recurrence after hepatectomy for malignant tumours (29 with colorectal secondaries) were treated with percutaneous RF ablation instead of repeat hepatectomy. RF thermal ablation was performed under image guidance for 12,15 min. This group represented 63 per cent of 75 patients treated with curative intent for liver recurrence in the same time interval. The other 28 patients underwent repeat hepatectomy. Results: The mean(s.d.) number of liver metastases destroyed was 14(07) (range 1,3) and their diameter was 21(8) (range 9,35) mm. Twenty-six patients presented with liver recurrence at least once but up to three times after the initial RF application. Incomplete local RF treatment was observed in six of 47 patients. Fifteen patients developed extrahepatic recurrence. The mean(s.d.) interval between RF ablation and the last follow-up visit was 144(101) (range 55,40) months. One death and three major complications occurred. Survival rates at 1 and 2 years were 88 and 55 per cent respectively. A retrospective study of the authors' database over two similar consecutive periods showed that RF ablation increased the percentage of curative local treatments for liver recurrence after hepatectomy from 17 to 26 per cent and decreased the proportion of repeat hepatectomies from 100 to to 39 per cent. Conclusion: Percutaneous RF treatment increases the number of patients eligible for curative treatment. It should be preferred to repeat hepatectomy when feasible and safe because it is less invasive. Repeat hepatectomy is indicated only when percutaneous RF ablation is contraindicated or fails. 2002 British Journal of Surgery Society Ltd [source]


High-intensity focused ultrasound for noninvasive functional neurosurgery,

ANNALS OF NEUROLOGY, Issue 6 2009
Ernst Martin MD
Transcranial magnetic resonance (MR)-guided high-intensity focused ultrasound (tcMRgHIFU) implies a novel, noninvasive treatment strategy for various brain diseases. Nine patients with chronic neuropathic pain were treated with selective medial thalamotomies. Precisely located thermal ablations of 4mm in diameter were produced at peak temperatures of 51C to 60C under continuous visual MR guidance and MR thermometry. The resulting lesions are clearly visible on follow-up MR imaging. All treatments were well tolerated, without side effects or neurological deficits. This is the first report on successful clinical application of tcMRgHIFU in functional brain disorders, portraying it as safe and reliable for noninvasive neurosurgical interventions. Ann Neurol 2009;66:858,861 [source]