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Volume comparison after radiofrequency ablation at two different target volumes by means of four different RF generators - MR volumetry in a 1.0 Tesla open MRI vs. macroscopic measurement
S140
Posters and Exhibits
Abstract No. 303 Volume comparison after radiofrequency ablation at two different target volumes by means of four different RF generators—MR volumetry in a 1.0 Tesla open MRI vs. macroscopic measurement H. Rathke1, F.V. Guettler2, B. Schnackenburg3, J. Rump1, B. Hamm1, U. Teichgraeber2, M. de Bucourt1; 1 Department of Radiology, Charité - University Medicine Berlin, Berlin, Germany; 2Department of Radiology, Jena University, Jena, Germany; 3Healthcare, Philips, Hamburg, Germany Purpose: In several studies radiofrequency ablation (RFA) was found to be safe and reliable for intervention of primary and secondary malignancies. The aim of this study was to evaluate MR volumetry directly after RFA in an open MRI and to validate the visualization of the produced necrosis volume. As the RF necrosis can be subdivided in three zones it was evaluated if the outer zone of the necrosis is detectable with the MR sequences used and whether or not there are differences with respect to lesion size and generator type. Materials and Methods: 64 liver specimens were ablated under constant simulated physiological conditions with four commercially available RF systems (A, B, C, D; n¼16 for each system; n¼8 for 3cm, and n¼8 for 5cm). Target volumes were set to 14.14cm3 (3cm lesion) and 65.45cm3(5cm lesion). T1 and PD weighted TSE sequences were acquired in a 1.0 Tesla open MRI and MR-volumetry was performed by semi-automatic software. After manual dissection actual macroscopic ablation diameters were recorded and volumes calculated. Results: For system A with the 3cm lesion, the manual measured macroscopic volume was 28.2cm3 in comparison to 15.2cm3/ 13.5cm3 (T1/PDW) using MR volumetry—with the 5cm lesion: 48.3cm3 vs. 19.3cm3/15.6cm3. System B: 3cm: 17.1cm3 vs. 6.5cm3/ 6.0cm3-5cm: 39.3cm3 vs. 16.7cm3/15.2cm3. System C: 3cm 29.7 cm3 vs. 12.9cm3/11.5cm3-5cm 71.8cm3 vs. 29.6cm3/27.4cm3. System D: 3cm 28.7cm3 vs. 11.3cm3/12.8cm3-5cm 93.9cm3 vs. 42.6cm3/37.5cm3. Conclusion: MR volumetry yielded smaller appearing volumes than manual measurement after dissection—irrespective of RF system used, target lesion size and MR sequence. Histopathological assessment showed an incomplete cellular damage in the transitional zone of the necrosis. As expected cellular apoptotic processes could not be detected immediately after RFA, probably also because of the ex vivo setting and missing blood perfusion.The exact transition from ablated to vital tissue could not be assessed directly after Intervention with the MR sequences investigated.
Posters and Exhibits
Abstract No. 304 Importance of functional Tc-99m-pertechnetate imaging in ultrasound guided percutaneous thermal microwave ablation of indifferent benign thyroid nodules H. Korkusuz, H. Christian, F. Grunwald; Department of Nuclear Medicine, Johann Wolfgang Goethe University Hospital, Frankfurt, Germany Purpose: Ultrasound guided percutaneous microwave ablation (MWA) is a new and promising method for minimal invasive thermal ablation of benign thyroid nodules.
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JVIR
Compared to radiofrequency ablation, MWA offers several advantages with comparable success rates. For verification of effectiveness, functional imaging with Tc-99m-pertechnetate is advisable. Aim of this study was to assess feasibility of MWA and applicability of functional imaging to verify effectiveness. Materials and Methods: Nine indifferent benign thyroid nodules of four patients (1f, 3m) were treated with MWA. MWA was performed under local anesthesia using a microwave generator (Avecure MWG881, MedWaves, Inc. San Diego, CA) with a wavelength field of 902 to 928 MHz. The field size varied from one to four cm. Target temperature ranged between 60 and 801C, with an output of 24 to 28 W. Pre- and post ablation, all patients received Tc-99mpertechnetate imaging concordant to the German guideline. To compare pre- and post ablative images, a Functional Imaging Score (FIS) was developed by classification of nodules in contrast to the surrounding parenchyma of the thyroid as: no storage (0 points), less storing (1 point), indifferent/neutral (2 points) and exceeding storage (3 points). Results: After MWA, the ablation zone showed a reduction of Tc-99m-pertechnetate uptake in reference to the sonographically defined zone. FIS showed a statistically significant average decrease of 1.33 points (po0.05). All patients reported slight pain and a feeling of pressure during ablation. Pain decreased with reduction of temperature and vanished after ablation. Conclusion: MWA was well tolerated and no severe complications could be observed. Therefore, MWA is a safe and effective method of treating benign thyroid nodules. Functional imaging with Tc-99m-pertechnetate is essential for early verification of effectiveness of thermal ablation and to evaluate therapy success. FIS allows a quantification of effectiveness and success of MWA.
Educational Exhibit
Abstract No. 305
A primer on immunology for the interventional oncologist D. Tabriz1, K. Zhang2, J.P. Erinjeri3; 1Radiology, University of Florida / Shands, Gainesville, FL; 2 Radiology, SUNY Downstate Medical Center, Brooklyn, NY; 3Radiology, Memorial Sloan-Kettering Cancer Center, New York, NY Learning Objectives: General immunological concepts introduced are: 1) Structure and function of the immune response with emphasis on adaptive immunity. 2) B cell and antibody biology. 3) T cell biology and main subtypes. 4) Cytokines and intercellular signaling5) Ablation and tumor immunology. Background: The immune system divides into innate and adaptive immunity. Innate immunity is the nonspecific preformed "first-line" of defense against pathogens. Adaptive immunity specifically and selectively removes agents, and provides memory if re-introduction of the offending agent occurs. B lymphocytes are antibody producers. Each B cell has antibodies that recognize antigens in their natural, undigested state. T lymphocytes recognize specific peptides broken down from larger antigens. Two main subtypes are cytotoxic (Tc) and helper (Th). Tc cells are destructive cells specialized at killing ("Top Gun pilots"). Th cells support and coordinate immune responses and consist of two main subtypes: Th1 and Th2 cells. Th1 cells support Tc cells ("Top Gun ground crew") and Th2 coordinate
Posters and Exhibits
Abstract No. 303 Volume comparison after radiofrequency ablation at two different target volumes by means of four different RF generators—MR volumetry in a 1.0 Tesla open MRI vs. macroscopic measurement H. Rathke1, F.V. Guettler2, B. Schnackenburg3, J. Rump1, B. Hamm1, U. Teichgraeber2, M. de Bucourt1; 1 Department of Radiology, Charité - University Medicine Berlin, Berlin, Germany; 2Department of Radiology, Jena University, Jena, Germany; 3Healthcare, Philips, Hamburg, Germany Purpose: In several studies radiofrequency ablation (RFA) was found to be safe and reliable for intervention of primary and secondary malignancies. The aim of this study was to evaluate MR volumetry directly after RFA in an open MRI and to validate the visualization of the produced necrosis volume. As the RF necrosis can be subdivided in three zones it was evaluated if the outer zone of the necrosis is detectable with the MR sequences used and whether or not there are differences with respect to lesion size and generator type. Materials and Methods: 64 liver specimens were ablated under constant simulated physiological conditions with four commercially available RF systems (A, B, C, D; n¼16 for each system; n¼8 for 3cm, and n¼8 for 5cm). Target volumes were set to 14.14cm3 (3cm lesion) and 65.45cm3(5cm lesion). T1 and PD weighted TSE sequences were acquired in a 1.0 Tesla open MRI and MR-volumetry was performed by semi-automatic software. After manual dissection actual macroscopic ablation diameters were recorded and volumes calculated. Results: For system A with the 3cm lesion, the manual measured macroscopic volume was 28.2cm3 in comparison to 15.2cm3/ 13.5cm3 (T1/PDW) using MR volumetry—with the 5cm lesion: 48.3cm3 vs. 19.3cm3/15.6cm3. System B: 3cm: 17.1cm3 vs. 6.5cm3/ 6.0cm3-5cm: 39.3cm3 vs. 16.7cm3/15.2cm3. System C: 3cm 29.7 cm3 vs. 12.9cm3/11.5cm3-5cm 71.8cm3 vs. 29.6cm3/27.4cm3. System D: 3cm 28.7cm3 vs. 11.3cm3/12.8cm3-5cm 93.9cm3 vs. 42.6cm3/37.5cm3. Conclusion: MR volumetry yielded smaller appearing volumes than manual measurement after dissection—irrespective of RF system used, target lesion size and MR sequence. Histopathological assessment showed an incomplete cellular damage in the transitional zone of the necrosis. As expected cellular apoptotic processes could not be detected immediately after RFA, probably also because of the ex vivo setting and missing blood perfusion.The exact transition from ablated to vital tissue could not be assessed directly after Intervention with the MR sequences investigated.
Posters and Exhibits
Abstract No. 304 Importance of functional Tc-99m-pertechnetate imaging in ultrasound guided percutaneous thermal microwave ablation of indifferent benign thyroid nodules H. Korkusuz, H. Christian, F. Grunwald; Department of Nuclear Medicine, Johann Wolfgang Goethe University Hospital, Frankfurt, Germany Purpose: Ultrasound guided percutaneous microwave ablation (MWA) is a new and promising method for minimal invasive thermal ablation of benign thyroid nodules.
’
JVIR
Compared to radiofrequency ablation, MWA offers several advantages with comparable success rates. For verification of effectiveness, functional imaging with Tc-99m-pertechnetate is advisable. Aim of this study was to assess feasibility of MWA and applicability of functional imaging to verify effectiveness. Materials and Methods: Nine indifferent benign thyroid nodules of four patients (1f, 3m) were treated with MWA. MWA was performed under local anesthesia using a microwave generator (Avecure MWG881, MedWaves, Inc. San Diego, CA) with a wavelength field of 902 to 928 MHz. The field size varied from one to four cm. Target temperature ranged between 60 and 801C, with an output of 24 to 28 W. Pre- and post ablation, all patients received Tc-99mpertechnetate imaging concordant to the German guideline. To compare pre- and post ablative images, a Functional Imaging Score (FIS) was developed by classification of nodules in contrast to the surrounding parenchyma of the thyroid as: no storage (0 points), less storing (1 point), indifferent/neutral (2 points) and exceeding storage (3 points). Results: After MWA, the ablation zone showed a reduction of Tc-99m-pertechnetate uptake in reference to the sonographically defined zone. FIS showed a statistically significant average decrease of 1.33 points (po0.05). All patients reported slight pain and a feeling of pressure during ablation. Pain decreased with reduction of temperature and vanished after ablation. Conclusion: MWA was well tolerated and no severe complications could be observed. Therefore, MWA is a safe and effective method of treating benign thyroid nodules. Functional imaging with Tc-99m-pertechnetate is essential for early verification of effectiveness of thermal ablation and to evaluate therapy success. FIS allows a quantification of effectiveness and success of MWA.
Educational Exhibit
Abstract No. 305
A primer on immunology for the interventional oncologist D. Tabriz1, K. Zhang2, J.P. Erinjeri3; 1Radiology, University of Florida / Shands, Gainesville, FL; 2 Radiology, SUNY Downstate Medical Center, Brooklyn, NY; 3Radiology, Memorial Sloan-Kettering Cancer Center, New York, NY Learning Objectives: General immunological concepts introduced are: 1) Structure and function of the immune response with emphasis on adaptive immunity. 2) B cell and antibody biology. 3) T cell biology and main subtypes. 4) Cytokines and intercellular signaling5) Ablation and tumor immunology. Background: The immune system divides into innate and adaptive immunity. Innate immunity is the nonspecific preformed "first-line" of defense against pathogens. Adaptive immunity specifically and selectively removes agents, and provides memory if re-introduction of the offending agent occurs. B lymphocytes are antibody producers. Each B cell has antibodies that recognize antigens in their natural, undigested state. T lymphocytes recognize specific peptides broken down from larger antigens. Two main subtypes are cytotoxic (Tc) and helper (Th). Tc cells are destructive cells specialized at killing ("Top Gun pilots"). Th cells support and coordinate immune responses and consist of two main subtypes: Th1 and Th2 cells. Th1 cells support Tc cells ("Top Gun ground crew") and Th2 coordinate