摘要:

AbstractThis clinical trial was performed to evaluate the safety and feasibility of interactive MR‐guided radiofrequency (RF) interstitial thermal ablation (ITA) performed entirely within the MR imager. RF‐ITA was performed on 11 intra‐abdominal metastatic tumors during 13 sessions. The RF electrode was placed under MR guidance on a .2‐T system using rapid fast imaging with steady state precession (FISP) and true FISP images. A custom 17‐gauge electrode was used and was modified in four sessions to allow circulation of iced saline for cooling during ablation. Tissue necrosis monitoring and electrode repositioning were based on rapid T2‐weighted and short‐inversion‐time inversion recovery (STIR) sequences. Morbidity and toxicity were assessed by clinical and imaging criteria. The region of tissue destruction was visible in all 11 tumors treated, as confirmed on subsequent contrast‐enhanced images. No significant morbidity was noted, and patient discomfort was minimal. In conclusion, interactive MR‐guided RF‐ITA is feasible on a clinical .2‐T C‐arm system with supplemental interventional accessories with only minor patient morbidity. The ability to completely ablate tumors with RF‐ITA depends on

ISSN:1053-1807    

DOI:10.1002/jmri.1880080112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractThis study describes the MR appearances of malignant hypervascular liver lesions pre‐ and post‐hepatic‐arterial chemoembolization, with correlation to serial imaging and clinical responses. Eight patients with malignant hypervascular liver lesions underwent pretreatment and posttreatment MR examination on a 1.5‐T MR imager. MR sequences included T1‐weighted spoiled gradient echo (SGE), T2‐weighted fat‐suppressed spin echo or turbo spin echo, and dynamic gadolinium‐enhanced SGE images. All patients underwent pretreatment, initial posttreatment, and subsequent posttreatment MR studies. The histology of primary tumors included various types of hepatocellular carcinoma (HCC) (four patients: fibrolamellar HCC [one patient], HCC [two patients], mixed HCC/cholangiocarcinoma [one patient]) and liver metastases (four patients: untyped islet cell tumor [two patients], gastrinoma [one patient], carcinoid [one patient]). Response to chemoembolization was determined by three assessments: MR response, serial imaging response, and clinical response. The appearance of MR response to chemoembolization was determined based on the correlation with clinical and serial imaging response. The MR response of lesions that showed good clinical response included: increase in signal intensity on T1‐weighted images (three patients), decrease in signal intensity on T2‐weighted images (three patients), and negligible or minimal enhancement on immediate postgadolinium images (four patients) after chemoembolization. The most marked change in lesion appearance was observed in lesions<1 cm, which had intense homogeneous enhancement on pretreatment MR studies and negligible enhancement on initial posttreatment MR examinations. MR response of lesions that showed moderate clinical response demonstrated a variety of lesion appearances from substantial change to minimal change. MR response of lesions that showed poor clinical response demonstrated no change in lesion appearances compared with the pretreatment MR study. Our results demonstrated change in appearance of liver lesions between pre‐ and post‐hepatic‐arterial chemoembolization MR studies. MR response correlated with response determined by serial imaging stud

ISSN:1053-1807    

DOI:10.1002/jmri.1880080113

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractLaser‐induced interstitial thermal therapy (LITT) is a preferred method of minimally invasive therapy. MRI is a noninvasive method by which to monitor the thermal effects of LITT. To properly control such effects, changes in MRI parameters during and after LITT should be correlated with changes in the tissue. T1‐weighted fast spin echo (FSE) MRI (1 image/10 seconds) at 1.5 T monitored LITT in vivo in rabbit liver (n= 6) using an interstitial bare delivery fiber (600‐μm diameter; 3.0 W; 1,064 nm; 150 seconds). During laser irradiation, MRI signal intensity decreased around the fiber tip; after irradiation, this hypointensity proved reversible and permanent lesions were evident. The lesions had hyperintense margins that were brighter than surrounding normal tissue (P<.001); the tissue in these bright regions was mapped to tissue necrosis characterized by the presence of thermally damaged ghost red blood cells amid generally normal hepatocytes. T1‐FSE identified the spatial extent of the LITT

ISSN:1053-1807    

DOI:10.1002/jmri.1880080114

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to determine the suitability of MRI to accurately detect radiofrequency (RF) thermoablative lesions created under MR guidance. In vivo RF lesions were created in the livers of six New Zealand White rabbits using a 2‐mm‐diameter titanium alloy RF electrode with a 20‐mm exposed tip and a 50‐W RF generator. This was performed using a 0.2T clinical C‐arm MR imager for guidance and monitoring. Each animal was sacrificed and gross evaluation was performed. Histologic correlation was performed on the first two animals. The MR‐compatible RF electrode was easily identified on rapid gradient‐echo images used to guide electrode placement. A single lesion was created in each rabbit liver. Lesions ranged from approximately 10 to 17 mm in diameter (mean, 13.5 mm). T2‐weighted and short T1 inversion recovery (STIR) images demonstrated lesions ranging in diameter from 12 to 18 mm (mean, 14.6 mm). Lesion dimensions determined from images closely correlated with those determined at gross examination with the discrepancy never exceeding 2 mm, for anr2value of .87. MRI performed at the time of MR‐guided RF ablation accurately demonstrated created lesions. This modality may provide a new option for the treatment of local and regional n

ISSN:1053-1807    

DOI:10.1002/jmri.1880080115

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractThe present paper is a study of theoretic modeling and experimental tests of that modeling for the local heating due to radiofrequency thermal ablation. A model is developed for the current and the associated electric field produced by a radiofrequency ablation probe. The temperature distributions resulting from the induced ohmic currents in the surrounding material are considered. A comparison is made between the theoretic temperature profiles and the shapes of thermal ablation ‘lesions’ produced in a controlled gelatin sample experiment. Comparison with the contours of human thermally induced liver lesions found in MRI studies also provides a validation of the success of the modeling. Successful modeling should lead to methods for optimization of the ablation procedure, especially as it is used in interventional

ISSN:1053-1807    

DOI:10.1002/jmri.1880080116

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractThere are many potential applications of three‐dimensional (3D) image registration in MR‐guided radiofrequency (RF) thermal ablation of tumors. For example, after registration of image volumes obtained before and after thermal ablation, a variety of quantitative and visual assessments of therapy were performed. For liver tumors, the accuracy of rigid body, manual registration on 19 pairs of image volumes was evaluated, almost all of which were obtained during thermal treatment sessions. Registration error was estimated as a distance between anatomical landmarks, including both internal vascular structures as well as the surface of the liver. Over all image pairs and throughout a large portion of the liver, the registration error was 3.1 mm (mean + 1 SD). From the bottom to the top of the liver, error increased on the order of 13%, probably because of liver motion and deformation resulting from respiration. Although probably insufficient for blind guidance of therapy, registration accuracy was undoubtedly sufficient for interesting applications in the planning, assessment, and optimization of interventional MR‐guided thermal treatment of liver t

ISSN:1053-1807    

DOI:10.1002/jmri.1880080117

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractThis is a report of our experience with percutaneous, MRI‐guided biopsies in 25 patients with skeletal lesions using a 1.5‐T MR hybrid system. Twenty‐five consecutive patients with skeletal lesions were referred for MRI‐guided biopsy. Biopsies were performed with a 1.5‐T Philips Gyroscan (Philips Medical Systems, Best, The Netherlands) combined with a c‐arm fluoroscopy. Specimens were obtained percutaneously either with a 14‐ or 18‐gauge “side‐slit” type of biopsy needle (n= 10 skeletal lesions that had penetrated through the cortex), or using a prototype coaxial drill system powered either by hand or an optional motor (n= 15 skeletal lesions still covered with cortical bone). All but two biopsies could be completed within the MR unit. For one patient, who required a transpedicular approach to a lumbar vertebra, and for one child, who required general anesthesia, we decided to switch to CT guidance. In 19 of the 25 cases (17 of the 23 cases performed in MR), the sample was sufficient and the histopathologic diagnosis was confirmed. Three patients had an inadequate sample, and three others had adequate samples but inaccurate results. No procedural complications occurred. Percutaneous biopsy of skeletal lesions performed under MRI‐guidance was found to be safe and reasonably accurate. There were no procedural complications in our small series. MRI may be used as an alternative to CT, but its role vis‐à‐vis

ISSN:1053-1807    

DOI:10.1002/jmri.1880080118

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractMRI was used to target and evaluate the tissue effects of focused ultrasound ablation on tumors implanted in the skeletal muscle of rabbits in vivo. First, MRI was used to localize the tumors and plan the ultrasound therapy. Second, temperature‐sensitive phase‐difference images were acquired to monitor the location of the ultrasound focus and to estimate the effects of temperature rise. After the treatment, the spatial and temporal temperature profiles for defining boundaries of tissue coagulation were calculated. Finally, these boundaries were compared to T2‐weighted and contrast‐enhanced T1‐weighted images obtained immediately after therapy. The results indicate that using MRI for planning and evaluating focused ultrasound surgery is feasible. We showed a linear relationship between applied power and shifts in the proton resonant frequency. Fluctuations in the location of the focus about the target location were on the order of the resolution of the MR images. The temperature rise and lesion size varied significantly. Regions of tissue coagulation calculated from MR data correlated well with post‐ther

ISSN:1053-1807    

DOI:10.1002/jmri.1880080119

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractGene therapy is a promising approach to the treatment of many forms of disease, including cancer. Of critical concern in its implementation is the ability to control the location, duration, and level of expression of the therapeutic gene. Here, we propose the use of local heat in combination with a heat‐sensitive promoter to help accomplish this. Certain members of the family of heat shock protein (hsp) promoters display a regulation that depends strongly on temperature. We present a study of natural hsp70 induction in rat leg by MRI‐guided focused ultrasound to investigate the hsp70 promoter as a possible candidate for use in control of gene expression with local heat. A temperature increase of 5–8°C in the focal region for 45 minutes led to a differential expression of the hsp70 mRNA between the focal region and the surrounding tissue ranging from a factor of 3

ISSN:1053-1807    

DOI:10.1002/jmri.1880080120

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY

摘要:

AbstractThe purpose of this paper was to investigate the feasibility of MR‐guided insertion of a temporary vena cava filter on an open low‐field imager. In vivo procedures were performed on four anesthetized pigs using a common nonferromagnetic temporary vena cava filter and a special prototype guidewire developed for vascular interventions guided by low‐field MRI. Breath‐hold spoiled gradient‐echo sequences (fast low‐angle shot [FLASH]) with flow compensation were used for position monitoring of the passively visualized intravascular devices. Using the described technique and equipment, all steps of the procedure were feasible in the MR unit. Practicability of the procedure seems to be sufficient for clinical purposes but was inferior compared to the conventional technique of filte

ISSN:1053-1807    

DOI:10.1002/jmri.1880080121

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1998

数据来源: WILEY