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2. Polymer gel dosimetry for the TG-43 dosimetric characterization of a new 125I interstitial brachytherapy seed

Author

Papagiannis, P, Pantelis, E, Georgiou, E, Karaiskos, P, Angelopoulos, A, Sakelliou, L, Stiliaris, S, Baltas, D, and Seimenis, I

Abstract

In this work, a polymer gel–magnetic resonance (MR) imaging method is employed for the dosimetric characterization of a new 125I low dose rate seed (IsoSeed model I25.S17). Two vials filled with PABIG gel were prepared in-house and one new seed as well as one commercially available 125I seed of similar dose rate and well-known dosimetric parameters (IsoSeed model I25.S06) were positioned in each vial. Both seeds in each vial were MR scanned simultaneously on days 11 and 26 after implantation. The data obtained from the known seed in each vial are used to calibrate the gel dose response which, for the prolonged irradiation duration necessitated by the investigated dose rates, depends on the overall irradiation time. Data for this study are presented according to the AAPM TG-43 dosimetric formalism. Polymer gel results concerning the new seed are compared to corresponding, published dosimetric results obtained, for the purpose of the new seed clinical implementation, by our group using the established methods of Monte Carlo (MC) simulation and thermo-luminescence dosimetry (TLD). Polymer gel dosimetry yields an average dose rate constant value of Λ = (0.921 0.031) cGy h−1 U−1 relative to MC? = (0.929 0.014) cGy h−1 U−1, TLD? = (0.951 0.044) cGy h−1 U−1 and the average value of Λ = (0.940 0.051) cGy h−1 U−1 proposed for the clinical implementation of the new seed. Results for radial dose function, gL(r), and anisotropy function, F(r, θ), also agree with corresponding MC calculations within experimental uncertainties which are smaller for the polymer gel method compared to TLD. It is concluded that the proposed polymer gel–magnetic resonance imaging methodology could be used at least as a supplement to the established techniques for the dosimetric characterization of new low energy and low dose rate interstitial brachytherapy seeds.

Published
2006

3. Radiological evaluation of the metal-bone interface of a porous tantalum monoblock acetabular component

Author

Macheras, G. A., Papagelopoulos, P. J., Kateros, K., Kostakos, A. T., Baltas, D., and Karachalios, T. S.

Abstract

Between January 1998 and December 1998, 82 consecutive patients (86 hips) underwent total hip arthroplasty using a trabecular metal monoblock acetabular component. All patients had a clinical and radiological follow-up evaluation at six, 12 and 24 weeks, 12 months, and then annually thereafter. On the initial post-operative radiograph 25 hips had a gap between the outer surface of the component and the acetabular host bed which ranged from 1 to 5 mm. All patients were followed up clinically and radiologically for a mean of 7.3 years (7 to 7.5). The 25 hips with the 1 to 5 mm gaps were studied for component migration at two years using the Einzel-Bild-Roentgen-Analyse (EBRA) digital measurement method. At 24 weeks all the post-operative gaps were filled with bone and no acetabular component had migrated. The radiographic outcome of all 86 components showed no radiolucent lines and no evidence of lysis. No acetabular implant was revised. There were no dislocations or other complications. The bridging of the interface gaps (up to 5 mm) by the trabecular metal monoblock acetabular component indicates the strong osteoconductive, and possibly osteoinductive, properties of trabecular metal.

Published
2006
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4. The effect of patient inhomogeneities in oesophageal <SUP>192</SUP>Ir HDR brachytherapy: a Monte Carlo and analytical dosimetry study

Author

Anagnostopoulos, G, Baltas, D, Pantelis, E, Papagiannis, P, and Sakelliou, L

Abstract

The effect of patient inhomogeneities surrounding the oesophagus on the dosimetry planning of an upper thoracic oesophageal 192Ir HDR brachytherapy treatment is studied. The MCNPX Monte Carlo code is used for dosimetry in a patient-equivalent phantom geometry and results are compared in terms of isodose contours as well as dose volume histograms with corresponding calculations by a contemporary treatment planning system software featuring a full TG-43 dose calculation algorithm (PLATO BPS version 14.2.4). It is found that the presence of patient inhomogeneities does not alter the delivery of the planned dose distribution to the planning treatment volume. Regarding the organs at risk, the common practice of current treatment planning systems (TPSs) to consider the patient geometry as a homogeneous water medium leads to a dose overestimation of up to 13% to the spinal cord and an underestimation of up to 15% to the sternum bone. These findings which correspond to the dose region of about 5–10% of the prescribed dose could only be of significance when brachytherapy is used as a boost to external beam therapy. Additionally, an analytical dosimetry model, which is efficient in calculating dose in mathematical phantoms containing inhomogeneity shells of materials of radiobiological interest, is utilized for dosimetry in the patient-equivalent inhomogeneous phantom geometry. Analytical calculations in this work are in good agreement with corresponding Monte Carlo results within the bone inhomogeneities of spinal cord and sternum bone but, like treatment planning system calculations, the model fails to predict the dose distribution in the proximal lung surface as well as within the lungs just as the TPS does, due to its inherent limitation in treating lateral scatter and backscatter radiation.

Published
2004

5. Abstracts der 3. Gemeinsamen Brachytherapiekonferenz SASRO/DEGRO/OEGRO

Author

Ott, O., Strnad, V., Pötter, R., Hammer, J., Hildebrandt, G., Resch, A., Kovács, G., Beckmann, M., Sauer, R., Niehoff, P., Polgar, C., Ostertag, H., Major, T., Eidtmann, H., Jonat, W., Kimmig, B., Roddiger, S., Kolotas, C., Kuner, R., Martin, T., Kurek, R., Baltas, D., Rogge, B., Kautschur, H., Hoffmann, G., Pollow, B., Kontova, M., Zamboglou, N., Ott, O., Lotter, M., Gallino, A., Mahler, F., Niewald, M., Jafari, F., Hennen, B., Wisser, L., Fleckenstein, J., Rübe, Ch., Böhm, M., Micke, O., Wagner, W., Schäfer, U., Willich, N., Greiner, R., Pallas, A., Pajic, B., Collen, T., Meurer, N., Töpfer, M., Ries, G., Leutloff, U., Frei, S., Warszawski, A., Baumann, R., Möller, T., Niedermeyer, J., Karstens, J., Gripp, S., Muskalla, K., Pulte, T., Ohmann, C., Röddiger, S., Dannenberg, T., Tunn, U., Dimopoulos, J., Schard, G., Kirisits, C., Lang, S., Goldner, G., Wachter, S., Wachter-Gerstner, N., Helbich, T., Weise, C., Bendel, M., Kocher, M., Müller, R.-P., Engelmann, U., Aebersold, D., Isaak, B., Vetterli, D., Kemmerling, L., Thalmann, G., Behrensmeier, F., Mini, R., Baier, K., Wulf, J., Nürnberg, N., Egberts, J., Galalae, R., Maurer, U., Maurer, G., Lang, K., Zumbé, J., Block, T., Czempiel, H., Machtens, S., Ponholzer, A., Riedl, A., Oismüller, R., Somay, C., Hawliczek, R., Maier, U., Madersbacher, S., Hoinkis, C., Winkler, C., Lehmann, D., Hakenberg, O., Herrmann, T., Messer, P., Gottfried, H.-W., Schneider, E., Röttinger, E., Haverkamp, U., Prümer, B., Krause, K., Tschuschke, C., Blumberg, J., Benkel, P., Fischedick, A., Geiger, M., Hoffmann, T., Reible, M., Meyer-Venter, R., Plümpe, A., Bund, J., Dreikorn, K., Staar, S., Horn, G., Zimmermann, J., Pfeiffer, D., Tauber, R., Bruns, T., Osieka, R., Blumstein, N., Schmidt, W., Büchler, F., Prikler, L., Seelentag, W., Koch, K., Haker, H., König, F., Oesterwitz, H., Schütz, R., Stahl, H., Ullmann, A., Sztankay, A., Rachbauer, F., Kreczy, A., Sununu, T., Bach, C., Nogler, M., Krismer, M., Eichberger, P., Schiestl, B., Lukas, P., Wolf, A., Hänsgen, G., Dunst, J., Utzig, D., Knocke-Abulesz, T., Baldass, M., Kucera, H., Weitmann, H., Waldhäusl, C., Nechvile, E., Knocke, T.-H., Georg, D., Krause, U., Fröhlich, D., Glatzel, M., Büntzel, J., Schröder, D., Küttner, K., Pfreundnerx, L., Willner, J., Bratengeier, K., Schwager, K., Hoppe, F., Schwab, F., Sauer, O., Flentje, M., Tselis, N., Schneider, O., Stückle, C., Adamietz, I., Weitman, H., Tepel, J., Schmid, A., Kohr, P., Kremer, B., Moh’d, Suleiman, Frey, J., Tschopp, J., Bieri, S., Jeszensky, D., Liebsch, N., Seelentag, W., Karle, H., Jacob-Heutmann, D., Born, C., Mohr, W., Kutzner, J., Thelen, M., Blochberger, P., Wächtler, M., Kaulich, T., Zurheide, J., Haug, T., Nüsslin, F., Bamberg, M., Curschmann, J., Kranzbühler, H., Greiner, R., Cossmann, P., Caversaccio, M., Pappas, I., and Nolte, L.

Published
2004
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6. DEGRO 2004

Author

Wendt, Thomas, Gademann, G., Pambor, C., Grießbach, I., Specht, H., Martin, T., Baltas, D., Kurek, R., Röddiger, S., Tunn, U., Zamboglou, N., Eich, H., Staar, S., Gossmann, A., Hansemann, K., Semrau, R., Skripnitchenko, R., Diehl, V., Müller, R.-P., Sehlen, S., Willich, N., Rühl, U., Lukas, P., Dühmke, E., Engel, K., Tabbert, E., Bolck, M., Knaack, S., Annweiler, H., Krempien, R., Hoppe, H., Harms, W., Daeuber, S., Schorr, O., Treiber, M., Debus, J., Alber, M., Paulsen, F., Birkner, M., Bakai, A., Belka, C., Budach, W., Grosser, K.-H., Kramer, R., Kober, B., Reinert, M., Schneider, P., Hertel, A., Feldmann, H., Csere, P., Hoinkis, C., Rothe, G., Zahn, P., Alheit, H., Cavanaugh, S., Kupelian, P., Reddy, C., Pollock, B., Fuss, M., Roeddiger, S., Dannenberg, T., Rogge, B., Drechsler, D., Herrmann, T., Alberti, W., Schwarz, R., Graefen, M., Krüll, A., Rudat, V., Huland, H., Fehr, C., Baum, C., Glocker, S., Nüsslin, F., Heil, T., Lemnitzer, H., Knips, M., Baumgart, O., Thiem, W., Kloetzer, K.-H., Hoffmann, L., Neu, B., Hültenschmidt, B., Sautter-Bihl, M.-L., Micke, O., Seegenschmiedt, M., Köppen, D., Klautke, G., Fietkau, R., Schultze, J., Schlichting, G., Koltze, H., Kimmig, B., Glatzel, M., Fröhlich, D., Bäsecke, S., Krauß, A., Strauß, D., Buth, K.-J., Böhme, R., Oehler, W., Bottke, D., Keilholz, U., Heufelder, K., Wiegel, T., Hinkelbein, W., Rödel, C., Papadopoulos, T., Munnes, M., Wirtz, R., Sauer, R., Rödel, F., Lubgan, D., Distel, L., Grabenbauer, G., Sak, A., Stüben, G., Pöttgen, C., Grehl, S., Stuschke, M., Müller, K., Pfaffendorf, C., Mayerhofer, A., Köhn, F., Ring, J., Beuningen, D., Meineke, V., Neubauer, S., Keller, U., Wittlinger, M., Riesenbeck, D., Greve, B., Exeler, R., Ibrahim, M., Liebscher, C., Severin, E., Ott, O., Pötter, R., Hammer, J., Hildebrandt, G., Beckmann, M., Strnad, V., Fehlauer, F., Tribius, S., Bajrovic, A., Höller, U., Rades, D., Warszawski, A., Baumann, R., Madry-Gevecke, B., Karstens, J., Grehn, C., Hensley, F., Berns, C., Wannenmacher, M., Semrau, S., Reimer, T., Gerber, B., Ketterer, P., Koepcke, E., Hänsgen, G., Strauß, H., Dunst, J., Füller, J., Kalb, S., Wendt, T., Weitmann, H., Waldhäusl, C., Knocke, T.-H., Lamprecht, U., Classen, J., Kaulich, T., Aydeniz, B., Bamberg, M., Wiezorek, T., Banz, N., Salz, H., Scheithauer, M., Schwedas, M., Lutterbach, J., Bartelt, S., Frommhold, H., Lambert, J., Hornung, D., Swiderski, S., Walke, M., Siefert, A., Pöllinger, B., Krimmel, K., Schaffer, M., Koelbl, O., Bratengeier, K., Vordermark, D., Flentje, M., Hero, B., Berthold, F., Combs, S., Gutwein, S., Schulz-Ertner, D., Kampen, M., Thilmann, C., Kocher, M., Kunze, S., Schild, S., Ikezaki, K., Müller, B., Sieber, R., Weiß, C., Wolf, I., Wenz, F., Weber, K.-J., Schäfer, J., Engling, A., Laufs, S., Veldwijk, M., Milanovic, D., Fleckenstein, K., Zeller, W., Fruehauf, S., Herskind, C., Weinmann, M., Jendrossek, V., Rübe, C., Appold, S., Kusche, S., Hölscher, T., Brüchner, K., Geyer, P., Baumann, M., Kumpf, R., Zimmermann, F., Schill, S., Geinitz, H., Nieder, C., Jeremic, B., Molls, M., Liesenfeld, S., Petrat, H., Hesselmann, S., Schäfer, U., Bruns, F., Horst, E., Wilkowski, R., Assmann, G., Nolte, A., Diebold, J., Löhrs, U., Fritz, P., Hans-Jürgen, K., Mühlnickel, W., Bach, P., Wahlers, B., Kraus, H.-J., Wulf, J., Hädinger, U., Baier, K., Krieger, T., Müller, G., Hof, H., Herfarth, K., Brunner, T., Hahn, S., Schreiber, F., Rustgi, A., McKenna, W., Bernhard, E., Guckenberger, M., Meyer, K., Willner, J., Schmidt, M., Kolb, M., Li, M., Gong, P., Abdollahi, A., Trinh, T., Huber, P., Christiansen, H., Saile, B., Neubauer-Saile, K., Tippelt, S., Rave-Fränk, M., Hermann, R., Dudas, J., Hess, C., Schmidberger, H., Ramadori, G., Andratschke, N., Price, R., Ang, K.-K., Schwarz, S., Kulka, U., Busch, M., Schlenger, L., Bohsung, J., Eichwurzel, I., Matnjani, G., Sandrock, D., Richter, M., Wurm, R., Budach, V., Feussner, A., Gellermann, J., Jordan, A., Scholz, R., Gneveckow, U., Maier-Hauff, K., Ullrich, R., Wust, P., Felix, R., Waldöfner, N., Seebass, M., Ochel, H.-J., Dani, A., Varkonyi, A., Osvath, M., Szasz, A., Messer, P., Blumstein, N., Gottfried, H.-W., Schneider, E., Reske, S., Röttinger, E., Grosu, A.-L., Franz, M., Stärk, S., Weber, W., Heintz, M., Indenkämpen, F., Beyer, T., Lübcke, W., Levegrün, S., Hayen, J., Czech, N., Mbarek, B., Köster, R., Thurmann, H., Todorovic, M., Schuchert, A., Meinertz, T., Münzel, T., Grundtke, H., Hornig, B., Hehr, T., Dilcher, C., Chan, R., Mintz, G., Kotani, J.-I., Shah, V., Canos, D., Weissman, N., Waksman, R., Wolfram, R., Bürger, B., Schrappe, M., Timmermann, B., Lomax, A., Goitein, G., Schuck, A., Mattke, A., Int-Veen, C., Brecht, I., Bernhard, S., Treuner, J., Koscielniak, E., Heinze, F., Kuhlen, M., Schorlemer, I., Ahrens, S., Hunold, A., Könemann, S., Winkelmann, W., Jürgens, H., Gerstein, J., Polivka, B., Sykora, K.-W., Bremer, M., Thamm, R., Höpfner, C., Gumprecht, H., Jäger, R., Leonardi, M., Frank, A., Trappe, A., Lumenta, C., Östreicher, E., Pinsker, K., Müller, A., Fauser, C., Arnold, W., Henzel, M., Groß, M., Engenhart-Cabillic, R., Schüller, P., Palkovic, S., Schröder, J., Wassmann, H., Block, A., Bauer, R., Keffel, F.-W., Theophil, B., Wisser, L., Rogger, M., Niewald, M., Lengen, V., Mathias, K., Welzel, G., Bohrer, M., Steinvorth, S., Schleußner, C., Leppert, K., Röhrig, B., Strauß, B., Oorschot, B., Köhler, N., Anselm, R., Winzer, A., Schneider, T., Koch, U., Schönekaes, K., Mücke, R., Büntzel, J., Kisters, K., Scholz, C., Keller, M., Winkler, C., Prause, N., Busch, R., Roth, S., Haas, I., Willers, R., Schultze-Mosgau, S., Wiltfang, J., Kessler, P., Neukam, F., Röper, B., Nüse, N., Auer, F., Melzner, W., Geiger, M., Lotter, M., Kuhnt, T., Müller, A., Jirsak, N., Gernhardt, C., Schaller, H.-G., Al-Nawas, B., Klein, M., Ludwig, C., Körholz, J., Grötz, K., Huppers, K., Kunkel, M., Olschewski, T., Bajor, K., Lang, B., Lang, E., Kraus-Tiefenbacher, U., Hofheinz, R., Gerstenberg-Helldorf, B., Willeke, F., Hochhaus, A., Roebel, M., Oertel, S., Riedl, S., Buechler, M., Foitzik, T., Ludwig, K., Klar, E., Meyer, A., Meier zu Eissen, J., Schwab, D., Meyer, T., Höcht, S., Siegmann, A., Sieker, F., Pigorsch, S., Milicic, B., Acimovic, L., Milisavljevic, S., Radosavljevic-Asic, G., Presselt, N., Baum, R., Treutler, D., Bonnet, R., Schmücking, M., Sammour, D., Fink, T., Ficker, J., Pradier, O., Lederer, K., Weiss, E., Hille, A., Welz, S., Sepe, S., Friedel, G., Spengler, W., Susanne, E., Kölbl, O., Hoffmann, W., Wörmann, B., Günther, A., Becker-Schiebe, M., Güttler, J., Schul, C., Nitsche, M., Körner, M., Oppenkowski, R., Guntrum, F., Malaimare, L., Raub, M., Schöfl, C., Averbeck, T., Hacker, I., Blank, H., Böhme, C., Imhoff, D., Eberlein, K., Weidauer, S., Böttcher, H., Edler, L., Tatagiba, M., Molina, H., Ostertag, C., Milker-Zabel, S., Zabel, A., Schlegel, W., Hartmann, A., Wildfang, I., Kleinert, G., Hamm, K., Reuschel, W., Wehrmann, R., Kneschaurek, P., Münter, M., Nikoghosyan, A., Didinger, B., Nill, S., Rhein, B., Küstner, D., Schalldach, U., Eßer, D., Göbel, H., Wördehoff, H., Pachmann, S., Hollenhorst, H., Dederer, K., Evers, C., Lamprecht, J., Dastbaz, A., Schick, B., Fleckenstein, J., Plinkert, P., Rübe, Chr., Merz, T., Sommer, B., Mencl, A., Ghilescu, V., Astner, S., Martin, A., Momm, F., Volegova-Neher, N., Schulte-Mönting, J., Guttenberger, R., Buchali, A., Blank, E., Sidow, D., Huhnt, W., Gorbatov, T., Heinecke, A., Beckmann, G., Bentia, A.-M., Schmitz, H., Spahn, U., Heyl, V., Prott, P.-J., Galalae, R., Schneider, R., Voith, C., Scheda, A., Hermann, B., Bauer, L., Melchert, F., Kröger, N., Grüneisen, A., Jänicke, F., Zander, A., Zuna, I., Schlöcker, I., Wagner, K., John, E., Dörk, T., Lochhas, G., Houf, M., Lorenz, D., Link, K.-H., Prott, F.-J., Thoma, M., Schauer, R., Heinemann, V., Romano, M., Reiner, M., Quanz, A., Oppitz, U., Bahrehmand, R., Tine, M., Naszaly, A., Patonay, P., Mayer, Á., Markert, K., Mai, S.-K., Lohr, F., Dobler, B., Pinkawa, M., Fischedick, K., Treusacher, P., Cengiz, D., Mager, R., Borchers, H., Jakse, G., Eble, M., Asadpour, B., Krenkel, B., Holy, R., Kaplan, Y., Block, T., Czempiel, H., Haverkamp, U., Prümer, B., Christian, T., Benkel, P., Weber, C., Gruber, S., Reimann, P., Blumberg, J., Krause, K., Fischedick, A.-R., Kaube, K., Steckler, K., Henzel, B., Licht, N., Loch, T., Krystek, A., Lilienthal, A., Alfia, H., Claßen, J., Spillner, P., Knutzen, B., Souchon, R., Schulz, I., Grüschow, K., Küchenmeister, U., Vogel, H., Wolff, D., Ramm, U., Licner, J., Rudolf, F., Moog, J., Rahl, C., Mose, S., Vorwerk, H., Weiß, E., Engert, A., Seufert, I., Schwab, F., Dahlke, J., Zabelina, T., Krüger, W., Kabisch, H., Platz, V., Wolf, J., Pfistner, B., Stieltjes, B., Wilhelm, T., Schmuecking, M., Junker, K., Treutier, D., Schneider, C., Leonhardi, J., Niesen, A., Hoeffken, K., Schmidt, A., Mueller, K.-M., Schmid, I., Lehmann, K., Blumstein, C., Kreienberg, R., Freudenberg, L., Kühl, H., Stahl, M., Elo, B., Erichsen, P., Stattaus, H., Welzel, T., Mende, U., Heiland, S., Salter, B., Schmid, R., Stratakis, D., Huber, R., Haferanke, J., Zöller, N., Henke, M., Lorenzen, J., Grzyska, B., Kuhlmey, A., Adam, G., Hamelmann, V., Bölling, T., Job, H., Panke, J., Feyer, P., Püttmann, S., Siekmeyer, B., Jung, H., Gagel, B., Militz, U., Piroth, M., Schmachtenberg, A., Hoelscher, T., Verfaillie, C., Kaminski, B., Lücke, E., Mörtel, H., Eyrich, W., Fritsch, M., Georgi, J.-C., Plathow, C., Zieher, H., Kiessling, F., Peschke, P., Kauczor, H.-U., Licher, J., Schneider, O., Henschler, R., Seidel, C., Kolkmeyer, A., Nguyen, T., Janke, K., Michaelis, M., Bischof, M., Stoffregen, C., Lipson, K., Weber, K., Ehemann, V., Jürgen, D., Achanta, P., Thompson, K., Martinez, J., Körschgen, T., Pakala, R., Pinnow, E., Hellinga, D., O’Tio, F., Katzer, A., Kaffer, A., Kuechler, A., Steinkirchner, S., Dettmar, N., Cordes, N., Frick, S., Kappler, M., Taubert, H., Bartel, F., Schmidt, H., Bache, M., Frühauf, S., Wenk, T., Litzenberger, K., Erren, M., Valen, F., Liu, L., Yang, K., Palm, J., Püsken, M., Behe, M., Behr, T., Marini, P., Johne, A., Claussen, U., Liehr, T., Steil, V., Moustakis, C., Griessbach, I., Oettel, A., Schaal, C., Reinhold, M., Strasssmann, G., Braun, I., Vacha, P., Richter, D., Osterham, T., Wolf, P., Guenther, G., Miemietz, M., Lazaridis, E., Forthuber, B., Sure, M., Klein, J., Saleske, H., Riedel, T., Hirnle, P., Horstmann, G., Schoepgens, H., Eck, A., Bundschuh, O., Oosterhut, A., Xydis, K., Theodorou, K., Kappas, C., Zurheide, J., Fridtjof, N., Ganswindt, U., Weidner, N., Buchgeister, M., Weigel, B., Müller, S., Glashörster, M., Weining, C., Hentschel, B., Sauer, O., Kleen, W., Beck, J., Lehmann, D., Ley, S., Fink, C., Puderbach, M., Hosch, W., Schmähl, A., Jung, K., Stoßberg, A., Rolf, E., Damrau, M., Oetzel, D., Maurer, U., Maurer, G., Lang, K., Zumbe, J., Hahm, D., Fees, H., Robrandt, B., Melcher, U., Niemeyer, M., Mondry, A., Kanellopoulos-Niemeyer, V., Karle, H., Jacob-Heutmann, D., Born, C., Mohr, W., Kutzner, J., Thelen, M., Schiebe, M., Pinkert, U., Piasswilm, L., Pohl, F., Garbe, S., Wolf, K., Nour, Y., Barwig, P., Trog, D., Schäfer, C., Herbst, M., Dietl, B., Cartes, M., Schroeder, F., Sigingan-Tek, G., Feierabend, R., Theden, S., Schlieck, A., Gotthardt, M., Glowalla, U., Kremp, S., Hamid, O., Riefenstahl, N., Michaelis, B., Schaal, G., Liebermeister, E., Niewöhner-Desbordes, U., Kowalski, M., Franz, N., Stahl, W., Baumbach, C., Thale, J., Wagner, W., Justus, B., Huston, A., Seaborn, R., Rai, P., Rha, S.-W., Sakas, G., Wesarg, S., Zogal, P., Schwald, B., Seibert, H., Berndt-Skorka, R., Seifert, G., Schoenekaes, K., Bilecen, C., Ito, W., Matschuck, G., and Isik, D.

Published
2004
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7. Evaluation of a TG-43 compliant analytical dosimetry model in clinical <SUP>192</SUP>Ir HDR brachytherapy treatment planning and assessment of the significance of source position and catheter reconstruction uncertainties

Author

Pantelis, E, Papagiannis, P, Anagnostopoulos, G, Baltas, D, Karaiskos, P, Sandilos, P, and Sakelliou, L

Abstract

A simple, time efficient, analytical model incorporating heterogeneities and body dimensions around a point 192Ir source is generalized for accurate dosimetry around commercially available 192Ir brachytherapy sources. The generalized model was verified in dosimetry of a clinical 192Ir high dose rate prostate monotherapy application, involving 16 catheters and 83 source dwell positions, through comparison with corresponding treatment planning system data. The computational time efficiency and accuracy of the proposed model allowed the assessment of the impact that uncertainties in source dwell positions and catheter reconstruction may have on dose distributions, and how these could potentially affect the clinical outcome. Results revealed that a 0.1 cm catheter reconstruction uncertainty and a 0.15 cm source position uncertainty along the catheter lead to a dose uncertainty of less than 2% for doses lower than 200% of the prescribed dose, reaching up to 5% for points lying in close proximity to the catheters. These uncertainties were found to have no impact (less than 1%) on dose volume histogram results of both the planning target volume and the urethra. A catheter reconstruction uncertainty as high as 0.2 cm results in a dose uncertainty greater than 2%, reaching up to 9%, only for points inside the 150% contour. However, even in this case, the impact on dose volume histogram calculations is less than 3%.

Published
2004

8. Global convergence analysis of fast multiobjective gradient-based dose optimization algorithms for high-dose-rate brachytherapy

Author

Lahanas, M, Baltas, D, and Giannouli, S

Abstract

We consider the problem of the global convergence of gradient-based optimization algorithms for interstitial high-dose-rate (HDR) brachytherapy dose optimization using variance-based objectives. Possible local minima could lead to only sub-optimal solutions. We perform a configuration space analysis using a representative set of the entire non-dominated solution space. A set of three prostate implants is used in this study. We compare the results obtained by conjugate gradient algorithms, two variable metric algorithms and fast-simulated annealing. For the variable metric algorithm BFGS from numerical recipes, large fluctuations are observed. The limited memory L-BFGS algorithm and the conjugate gradient algorithm FRPR are globally convergent. Local minima or degenerate states are not observed. We study the possibility of obtaining a representative set of non-dominated solutions using optimal solution rearrangement and a warm start mechanism. For the surface and volume dose variance and their derivatives, a method is proposed which significantly reduces the number of required operations. The optimization time, ignoring a preprocessing step, is independent of the number of sampling points in the planning target volume. Multiobjective dose optimization in HDR brachytherapy using L-BFGS and a new modified computation method for the objectives and derivatives has been accelerated, depending on the number of sampling points, by a factor in the range 10–100.

Published
2003
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9. A hybrid evolutionary algorithm for multi-objective anatomy-based dose optimization in high-dose-rate brachytherapy

Author

Lahanas, M, Baltas, D, and Zamboglou, N

Abstract

Multiple objectives must be considered in anatomy-based dose optimization for high-dose-rate brachytherapy and a large number of parameters must be optimized to satisfy often competing objectives. For objectives expressed solely in terms of dose variances, deterministic gradient-based algorithms can be applied and a weighted sum approach is able to produce a representative set of non-dominated solutions. As the number of objectives increases, or non-convex objectives are used, local minima can be present and deterministic or stochastic algorithms such as simulated annealing either cannot be used or are not efficient. In this case we employ a modified hybrid version of the multi-objective optimization algorithm NSGA-II. This, in combination with the deterministic optimization algorithm, produces a representative sample of the Pareto set. This algorithm can be used with any kind of objectives, including non-convex, and does not require artificial importance factors. A representation of the trade-off surface can be obtained with more than 1000 non-dominated solutions in 2–5 min. An analysis of the solutions provides information on the possibilities available using these objectives. Simple decision making tools allow the selection of a solution that provides a best fit for the clinical goals. We show an example with a prostate implant and compare results obtained by variance and dose-volume histogram (DVH) based objectives.

Published
2003

10. CT imaging based digitally reconstructed radiographs and their application in brachytherapy

Author

Milickovic, N, Baltas, D, Giannouli, S, Lahanas, M, and Zamboglou, N

Abstract

The aim of our study was to develop an algorithm to simulate the digitally reconstructed radiograph (DRR) calculation process for different beam qualities (photon energies) in the range 50 keV to 12 MeV. This was achieved using volumetric anatomical data for the patient obtained from three-dimensional diagnostic CT images. These DRR images can be used in three-dimensional treatment planning for external beam radiotherapy as well as for brachytherapy in the same way as conventional radiographic films. The advantages of using such DRRs in modern 3D brachytherapy treatment planning are shown. A number of tools are described, illustrating that the application of DRRs in brachytherapy is very useful.

Published
2000
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13. Anatomy‐based three‐dimensional dose optimization in brachytherapy using multiobjective genetic algorithms

Author

Lahanas, M., Baltas, D., and Zamboglou, N.

Abstract

In conventional dose optimization algorithms, in brachytherapy, multiple objectives are expressed in terms of an aggregating function which combines individual objective values into a single utility value, making the problem single objective, prior to optimization. A multiobjective genetic algorithm (MOGA) was developed for dose optimization based on an a posterioriapproach, leaving the decision‐making process to a planner and offering a representative trade‐off surface of the various objectives. The MOGA provides a flexible search engine which provides the maximum of information for a decision maker. Tests performed with various treatment plans in brachytherapy have shown that MOGA gives solutions which are superior to those of traditional dose optimization algorithms. Objectives were proposed in terms of the COIN distribution and differential volume histograms, taking into account patient anatomy in the optimization process.

Published
1999
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16. CT guided interstitial high dose rate brachytherapy for recurrent malignant gliomas.

Author

Kolotas, C, Birn, G, Baltas, D, Rogge, B, Ulrich, P, and Zamboglou, N

Abstract

This paper describes the technique and preliminary results of high dose rate (HDR) interstitial brachytherapy for recurrent grade III and grade IV gliomas. Although in the initial treatment of malignant gliomas brachytherapy has been shown to give better results than external beam therapy, this has previously always been with low dose rate (LDR) brachytherapy. Stereotactic frames are used for interstitial LDR brachytherapy but a CT image-guided technique does not require such a frame. The survival rates for our initial 53 patients do not significantly differ from LDR results. However, using HDR there are several advantages, including a much shorter treatment time with HDR than LDR and better patient comfort. HDR also allows better individualized optimization of the treatment than LDR.

Published
1999
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18. Prognostic evaluation of oestrogen-regulated protein immunoreactivity in ductal invasive (NOS) breast cancer

Author

Nakopoulou, L., Lazaris, A. C., Baltas, D., Giannopoulou, I., Kavantzas, N., and Tzonou, A.

Abstract

Determination of steroid receptors and several oestrogen-regulated proteins in mammary carcinomas is useful in the prediction of their evolution and of the likely success of endocrine therapy. Cathepsin D (Cat D), pS2 peptide and heat shock protein 27 (Hsp 27) were detected immunohistochemically in 63 infiltrating ductal (NOS) breast carcinomas, and our results were qualitatively correlated with several clinicopathological indicators and patients' overall survival. Cat D immunostaining of tumour cells was strongly associated with axillary nodal involvement (Pf=0.0005) and so, it is directly connected with the metastatic capacity of malignant cells. pS2 immunoreactivity was correlated with oestrogen and progesterone receptor positivity (Pf=0.0009 and Pf=0.05 respectively) and, nonsignificantly, with good differentiation of the tumours (Pf=0.06). Neoplastic cells expressing this protein are therefore characterised by a highly organised state of cellular physiology. Hsp 27 was expressed predominantly in tumours with one to four infiltrated lymph nodes (Pt=0.05), and Hsp 27-positive patients were inclined to rather short survival, possibly due to chemotherapy resistance. In future, prognostic estimation of each one of the examined markers should be performed in specific large subgroups of patients. The findings of this study contribute to the establishment of criteria by which these subgroups should be formed.

Published
1995
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19. Ein Qualitätssicherungsprogramm für Simulatoren in der Strahlentherapie

Author

Müller-Sievers, K., Baltas, D., and Kober, B.

Abstract

Zusammenfassung: Hintergrund: Seit Beginn der neunziger Jahre führen wir an einem seit nunmehr 16 Jahren betriebenen Therapiesimulator Konstanzprüfungen durch. Material und Methode: Die Konstanzprüfungen orientieren sich sowohl and den deutschen Normen zur Überprüfung von Beschleunigern wie auch an den Vorschlägen internationaler Gremien zur Simulatorüberprüfung (International Electrotechnical Commission). Die Prüfungen untergliedern sich in tägliche Sichtprüfungen (Lichtfeldanzeige, optischer Entfernungsmesser, Laserlichtvisiereinstellung, Winkelanzeigen für Tragarm und Blende) und in monatlich und jährlich wiederkehrende Konstanzprüfungen wesentlicher Kennmerkmale des Simulators. An einigen wesentlichen Beispielen wird die geringe Variation von Prüfmerkmalen während eines sechsjährigen Zeitraums dargestellt: Lageabweichung der Lichtfeldmitte bei Drehung der Meßblende, Durchmesser des Isozentrumkreises bei Tragarmdrehung, Genauigkeit der Anzeige des Isozentrums und Übereinstimmug von Lichtfeld und simuliertem Strahlenfeld. Ergebnisse: Es stellte sich heraus, daß nur durch diese engmaschigen Kontrollen sichergestellt werden kann, daß die unvermeidbar auftretende Verschlechterung von Einstellwerten schnell erkannt wird. Schlußfolgerung: Durch gerätetechnische Erneuerungen und gezielt angeforderte Einsätze von Servicetechnikern war es bisher möglich, an unserem in bezug auf das Baujahr alten Simulator eine so gute Reproduzierbarkeit der Einstellparameter zu erreichen und zu erhalten, wie sie nach internationaler Übereinkunft für eine moderne Strahlentherapie Voraussetzung ist.

Published
1997
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21. Apparative Voraussetzungen für eine Kurzzeit-Afterloading-Therapie

Author

Baltas, D., Ertan, E., Kober, B., Meier, H., and Müller-Sievers, K.

Abstract

Für die Brachytherapie wurde ein neuer Patiententisch entwickelt, der die Genauigkeitsanforderungen einer Hochdosisleistung-Afterloading-Therapie erfüllt und gleichzeitig eine flexible Applikations-, Lokalisationsund Bestrahlungsvorrichtung bietet. Unsere ersten Erfahrungen mit gynäkologischen Applikationen haben diese Vorteile der neuen Entwicklung bestätigt.

Published
1991
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