Franz Schwab

Three dimensional variability in patient positioning using bite block immobilization in 3D-conformal radiation treatment for ENT-tumors

BACKGROUND AND PURPOSE The aim of this prospective study was to analyze the three-dimensional (3D) reproducibility of the isocenter position and of patient positioning with the use of bite block immobilization by means of a simple verification procedure for a complex beam arrangement applied for ENT-tumors. MATERIALS AND METHODS We analyzed the positioning data of 29 consecutive patients treated for ENT-tumors at the Department of Radiotherapy and Oncology of the University of Wurzburg. A total of 136 treatment sessions were analyzed. Patients were positioned and immobilized using an individualized bite block system and a head and neck support. A complex beam arrangement was applied combining two offset rotational and two oblique wedge fields on a 5 MV linear accelerator. Orthogonal verification films were taken once weekly. Four to six film pairs per patient were obtained (during 4-6 weeks) with a mean number of 4.7 film pairs per patient. These were compared to the corresponding orthogonal simulator films taken during primary simulation. Deviations of the verified isocenter from the isocenter on the simulator film were measured and analyzed in three dimensions in terms of overall, systematic and random categories. A 3D-deviation vector was calculated from these 3D data as well as a 2D-deviation vector (for comparison with literature data) from the lateral verification films. RESULTS The overall setup deviation showed standard deviations (SD) of 2.5, 2.7 and 3.1 mm along the cranio-caudal, anterior-posterior and medio-lateral axes, respectively. The random component ranged from SD 1.9 to 2.1 mm and the systematic component ranged from SD 1.8 to 2.2 mm. The mean length of the 3D-vector was 3.1 mm for the systematic as well as the random component. Ninety percent of 3D systematic and random deviations were less than 5 mm. The mean length of the 2D-vector was 2.4 mm for the random component and 2.2 mm for the systematic component. Ninety percent of 2D-random and systematic variations were less than 4 mm. CONCLUSIONS The presented individualized bite block immobilization device provides an accurate and reproducible patient positioning for 3D-conformal radiation therapy in the head and neck. Random and systematic deviations in each of the three directions are in the range of +/-4 mm (2 SD, comprising 95% of the deviations) and are within the range or even less than deviations described for most thermoplastic or PVC-mask fixation devices. These deviations should be taken into account during definition of planning target volume in head and neck tumors.

CARDIAC MAGNETIC RESONANCE IMAGING FINDINGS IN 20-YEAR SURVIVORS OF MEDIASTINAL RADIOTHERAPY FOR HODGKIN'S DISEASE

PURPOSE The recognition of the true prevalence of cardiac toxicity after mediastinal radiotherapy requires very long follow-up and a precise diagnostic procedure. Cardiac magnetic resonance imaging (MRI) permits excellent quantification of cardiac function and identification of localized myocardial defects and has now been applied to a group of 20-year Hodgkins disease survivors. METHODS AND MATERIALS Of 143 patients treated with anterior mediastinal radiotherapy (cobalt-60, median prescribed dose 40 Gy) for Hodgkins disease between 1978 and 1985, all 53 survivors were invited for cardiac MRI. Of those, 36 patients (68%) presented for MRI, and in 31 patients (58%) MRI could be performed 20-28 years (median, 24) after radiotherapy. The following sequences were acquired on a 1.5-T MRI: transversal T1-weighted TSE and T2-weighted half-fourier acquisition single-shot turbo-spin-echo sequences, a steady-state free precession (SSFP) cine sequence in the short heart axis and in the four-chamber view, SSFP perfusion sequences under rest and adenosine stress, and a SSFP inversion recovery sequence for late enhancement. The MRI findings were correlated with previously reconstructed doses to cardiac structures. RESULTS Clinical characteristics and reconstructed doses were not significantly different between survivors undergoing and not undergoing MRI. Pathologic findings were reduced left ventricular function (ejection fraction <55%) in 7 (23%) patients, hemodynamically relevant valvular dysfunction in 13 (42%), late myocardial enhancement in 9 (29%), and any perfusion deficit in 21 (68%). An association of regional pathologic changes and reconstructed dose to cardiac structures could not be established. CONCLUSIONS In 20-year survivors of Hodgkins disease, cardiac MRI detects pathologic findings in approximately 70% of patients. Cardiac MRI has a potential role in cardiac imaging of Hodgkins disease patients after mediastinal radiotherapy.

Comparison of Wedge versus Segmented Techniques in Whole Breast Irradiation

Purpose:To compare two irradiation techniques for whole breast irradiation: tangential wedged beams (WT) versus “open” fields (without wedges) with forward planned segments (ST).Patients and Methods:For 20 patients two comparative 3-D plans were defined using Pinnacle P3D and analyzed with respect to dose, dose homogeneity in the target volume, and scattered dose to organs at risk. The plans of six patients were reproduced in an Alderson phantom. Measurements were performed in the planning target volume (PTV), contralateral breast, lungs, heart, thyroid gland and in mid-pelvis.Results:Dose distribution in the PTV was nearly identical for WT and ST with the exception of D1. Scattered doses were significantly smaller for ST. In the contralateral breast the doses per 2-Gy fraction were 7.3 cGy ± 2.1 cGy (WT), and 4.7 cGy ± 1.9 cGy (ST; p < 0.01). Similar doses were measured for lung and heart. In mid pelvis the largest difference was observed (WT: 1.0 cGy ± 0.2 cGy, ST: 0.2 cGy ± 0.1 cGy; p < 0.01).Conclusion:Partial volume segments can replace wedges for improved dose coverage and homogeneity in the PTV. The ST causes significantly less scattered dose to extra-target organs. This may have implications for long-term risks after exposure to low radiation doses.Ziel:Vergleich zweier Bestrahlungstechniken für die Brustbestrahlung: tangentiale Keilfiltertechnik (WT) versus „offene“ Felder (ohne Keil) mit vorwärts geplanten Segmenten (ST).Patienten und Methodik:Bei 20 Patientinnen wurden je ein Bestrahlungsplan mit Keilfiltern und ein Plan mit segmentierten Feldern erstellt und bezüglich Dosis, Dosishomogenität im Zielvolumen und Streuanteil in Risikoorganen analysiert. Die Pläne von sechs Patientinnen wurden am Alderson-Phantom reproduziert. Messungen wurden im Zielvolumen (PTV), der kontralateralen Brust, den Lungen, dem Herzen, der Schilddrüse und im kleinen Becken durchgeführt.Ergebnisse:Die Dosisverteilung im Planungszielvolumen (PTV) war für WT und ST nahezu identisch mit Ausnahme von D1. Der Streuanteil für Risikoorgane war für die ST signifikant geringer. In der kontralateralen Mamma betrug die Dosis pro 2-Gy-Fraktion mit der WT 7,3 cGy ± 2,1 cGy und mit der ST 4,7 cGy ± 1,9 cGy (p < 0,01). Ähnliche Ergebnisse wurden für die Dosen in Lunge und Herz gemessen. Der größte Unterschied zwischen WT und ST zeigte sich im kleinen Becken (WT 1,0 cGy ± 0,2 cGy, ST 0,2 cGy ± 0,1 cGy; p < 0,01).Schlussfolgerung:Teilvolumensegmente können Keile in Bezug auf Zielvolumenabdeckung und Dosishomogenität im PTV ersetzen. Die ST verursacht signifikant weniger Streuanteil außerhalb des Zielvolumens. Dies kann Einfluss auf Langzeitrisiken nach Exposition niedriger Strahlendosen haben.

Comparison of wedge versus segmented techniques in whole breast irradiation: effects on dose exposure outside the treatment volume.

Purpose:To compare two irradiation techniques for whole breast irradiation: tangential wedged beams (WT) versus “open” fields (without wedges) with forward planned segments (ST).Patients and Methods:For 20 patients two comparative 3-D plans were defined using Pinnacle P3D and analyzed with respect to dose, dose homogeneity in the target volume, and scattered dose to organs at risk. The plans of six patients were reproduced in an Alderson phantom. Measurements were performed in the planning target volume (PTV), contralateral breast, lungs, heart, thyroid gland and in mid-pelvis.Results:Dose distribution in the PTV was nearly identical for WT and ST with the exception of D1. Scattered doses were significantly smaller for ST. In the contralateral breast the doses per 2-Gy fraction were 7.3 cGy ± 2.1 cGy (WT), and 4.7 cGy ± 1.9 cGy (ST; p < 0.01). Similar doses were measured for lung and heart. In mid pelvis the largest difference was observed (WT: 1.0 cGy ± 0.2 cGy, ST: 0.2 cGy ± 0.1 cGy; p < 0.01).Conclusion:Partial volume segments can replace wedges for improved dose coverage and homogeneity in the PTV. The ST causes significantly less scattered dose to extra-target organs. This may have implications for long-term risks after exposure to low radiation doses.Ziel:Vergleich zweier Bestrahlungstechniken für die Brustbestrahlung: tangentiale Keilfiltertechnik (WT) versus „offene“ Felder (ohne Keil) mit vorwärts geplanten Segmenten (ST).Patienten und Methodik:Bei 20 Patientinnen wurden je ein Bestrahlungsplan mit Keilfiltern und ein Plan mit segmentierten Feldern erstellt und bezüglich Dosis, Dosishomogenität im Zielvolumen und Streuanteil in Risikoorganen analysiert. Die Pläne von sechs Patientinnen wurden am Alderson-Phantom reproduziert. Messungen wurden im Zielvolumen (PTV), der kontralateralen Brust, den Lungen, dem Herzen, der Schilddrüse und im kleinen Becken durchgeführt.Ergebnisse:Die Dosisverteilung im Planungszielvolumen (PTV) war für WT und ST nahezu identisch mit Ausnahme von D1. Der Streuanteil für Risikoorgane war für die ST signifikant geringer. In der kontralateralen Mamma betrug die Dosis pro 2-Gy-Fraktion mit der WT 7,3 cGy ± 2,1 cGy und mit der ST 4,7 cGy ± 1,9 cGy (p < 0,01). Ähnliche Ergebnisse wurden für die Dosen in Lunge und Herz gemessen. Der größte Unterschied zwischen WT und ST zeigte sich im kleinen Becken (WT 1,0 cGy ± 0,2 cGy, ST 0,2 cGy ± 0,1 cGy; p < 0,01).Schlussfolgerung:Teilvolumensegmente können Keile in Bezug auf Zielvolumenabdeckung und Dosishomogenität im PTV ersetzen. Die ST verursacht signifikant weniger Streuanteil außerhalb des Zielvolumens. Dies kann Einfluss auf Langzeitrisiken nach Exposition niedriger Strahlendosen haben.

3-D reconstruction of anterior mantle-field techniques in Hodgkin's disease survivors: doses to cardiac structures

BackgroundThe long-term dose-effect relationship for specific cardiac structures in mediastinal radiotherapy has rarely been investigated. As part of an interdisciplinary project, the 3-D dose distribution within the heart was reconstructed in all long-term Hodgkins disease survivors (n = 55) treated with mediastinal radiotherapy between 1978 and 1985. For dose reconstruction, original techniques were transferred to the CT data sets of appropriate test patients, in whom left (LV) and right ventricle (RV), left (LA) and right atrium (RA) as well as right (RCA), left anterior descending (LAD) and left circumflex (LCX) coronary arteries were contoured. Dose-volume histograms (DVHs) were generated for these heart structures and results compared between techniques.ResultsPredominant technique was an anterior mantle field (cobalt-60). 26 patients (47%) were treated with anterior mantle field alone (MF), 18 (33%) with anterior mantle field and monoaxial, bisegmental rotation boost (MF+ROT), 7 (13%) with anterior mantle field and dorsal boost (MF+DORS) and 4 (7%) with other techniques. Mean ± SD total mediastinal doses for MF+ROT (41.7 ± 3.5 Gy) and for MF+DORS (42.7 ± 7.4) were significantly higher than for MF (36.7 ± 5.2 Gy). DVH analysis documented relative overdosage to right heart structures with MF (median maximal dose to RV 129%, to RCA 127%) which was siginificantly reduced to 117% and 112%, respectively, in MF+ROT. Absolute doses in right heart structures, however, did not differ between techniques. Absolute LA doses were significantly higher in MF+ROT patients than in MF patients where large parts of LA were blocked. Median maximal doses for all techniques ranged between 48 and 52 Gy (RV), 44 and 46 Gy (LV), 47 and 49 Gy (RA), 38 and 45 Gy (LA), 46 and 50 Gy (RCA), 39 and 44 Gy (LAD) and 34 and 42 Gy (LCX).ConclusionIn patients irradiated with anterior mantle-field techniques, high doses to anterior heart portions were partly compensated by boost treatment from non-anterior angles. As the threshold doses for coronary artery disease, cardiomyopathy, pericarditis and valvular changes are assumed to be 30 to 40 Gy, cardiac toxicity must be anticipated in these patients. Thus, dose distributions in individual subjects should be correlated to the corresponding cardiovascular findings in these long-term survivors, e. g. by cardiovascular magnetic resonance imaging.

Radiotherapy of prostate cancer with multileaf collimators (MLCs) optimization of the undulating dose distribution at the MLC edge

Background and Purpose:A technical modification for radiotherapy of prostate cancer is presented to smooth the scalloped dose pattern that occurs at treatment field edge, when a multileaf collimator (MLC) has been used.Material and Methods:Ten patients with prostate cancer receiving postoperative, adjuvant irradiation were studied prospectively. By a three-dimensional planning system (TMS, Helax 6.1B) the irradiation was planned for an 18-MV linear accelerator (Primus 1, Siemens). The volumes of interest (VOI) were the planning target volume (PTV; the region of the prostate including the seminal vesicles), the volume of rectum (Vrectum) and urinary bladder (Vbladder). Two four-field techniques (0°, 90°, 180°, 270°) were planned using “beam’s eye view” for setting the leaf position of the MLC. For technique A the MLC was adapted to the PTV using a 0° collimator angle for the lateral fields. For technique B the collimator angle of the lateral fields was optimized to compensate the cascade field shape. Dose-volume histograms of PTV, Vrectum and Vbladder were analyzed. The dose was prescribed for the reference point according to ICRU 50. Film dosimetry was used to show the dose pattern at the field edge produced by the two techniques.Results:Dose to PTV did not differ between technique A and B. Median dose to Vrectum was 82.6% for technique A and 77.3% for technique B (p < 0.001). Technique A irradiates a larger Vrectum than technique B being significant for all isodose levels tested. Median dose to Vbladder did not differ for technique A and B (p > 0.05).Conclusion:The presented technical modification is an effective method to blur the staggered dose distribution that results, when the MLC is conventionally stepped to adapt to the dorsal, irregular PTV border in irradiation of prostate. Especially for irradiation to escalated dose levels, this modification may reduce the dose to the rectum and thus the rectal side effects in comparison to the conventional MLC fields.Hintergrund und Ziel:Eine Modifikation der Bestrahlungstechnik beim Prostatakarzinom wird vorgestellt, die den mehrstufigen Dosisverlauf am Feldrand ausgleicht, wie er bei Verwendung eines Multileaf-Kollimators (MLC) entsteht.Material and Methodik:Zehn Patienten wurden in die Analyse einbezogen. Mittels eines dreidimensionalen Bestrahlungsplanungssystems (Helax TMS 6.1B) wurden die Bestrahlungstechniken für einen 18-MV-Linearbeschleuniger (Primus 1, Siemens) berechnet. Als „volumes of interest“ (VOI) wurden das Planungszielvolumen (PTV; Prostataregion inkl. Samenblasen) sowie das Volumen von Rektum (Vrectum) und Harnblase (Vbladder) definiert. Zwei Vierfeldertechniken (Gantry: 0°, 90°, 180°, 270°) wurden unter Verwendung des „beam’s eye view“ geplant. Bei Technik A wurde der MLC in jedem Feld bei einem Kollimatorwinkel von 0° an das PTV angepasst, bei Technik B wurde der Kollimatorwinkel der seitlichen Felder so optimiert, dass sich die in den seitlichen Feldern entstehenden Stufen gegenseitig ausglichen. Die Dosis-Volumen-Histogramme von PTV, Vrectum und Vbladder wurden ausgewertet. Die Dosisangabe bezieht sich auf den Referenzpunkt gemäß ICRU 50. Durch Filmdosimetrie wurde der Dosisverlauf am Feldrand bei beiden Techniken überprüft.Ergebnisse:Die Dosis im PTV unterschied sich bei Technik A und B nicht. Die mediane Dosis in Vrectum betrug 82,6% für Technik A und 77,3% für Technik B (p < 0,001). Die Werte für Vrectum waren in allen untersuchten Dosisbereichen für Technik A größer als für Technik B. Die mediane Dosis in Vbladder unterschied sich bei beiden Techniken nicht (p > 0,05).Schlussfolgerung:Die vorgestellte Modifikation ist eine einfache und effektive Methode zum Ausgleich der stufigen Feldränder und Dosisverläufe, wie sie bei der Verwendung von MLC entstehen. Bei der Bestrahlung des Prostatakarzinoms ist dadurch eine Dosisreduktion im Bereich des Rektums mit evtl. reduzierten Nebenwirkungen möglich.

Radiotherapy of Prostate Cancer with Multileaf Collimators (MLCs)

Background and Purpose:A technical modification for radiotherapy of prostate cancer is presented to smooth the scalloped dose pattern that occurs at treatment field edge, when a multileaf collimator (MLC) has been used.Material and Methods:Ten patients with prostate cancer receiving postoperative, adjuvant irradiation were studied prospectively. By a three-dimensional planning system (TMS, Helax 6.1B) the irradiation was planned for an 18-MV linear accelerator (Primus 1, Siemens). The volumes of interest (VOI) were the planning target volume (PTV; the region of the prostate including the seminal vesicles), the volume of rectum (Vrectum) and urinary bladder (Vbladder). Two four-field techniques (0°, 90°, 180°, 270°) were planned using “beam’s eye view” for setting the leaf position of the MLC. For technique A the MLC was adapted to the PTV using a 0° collimator angle for the lateral fields. For technique B the collimator angle of the lateral fields was optimized to compensate the cascade field shape. Dose-volume histograms of PTV, Vrectum and Vbladder were analyzed. The dose was prescribed for the reference point according to ICRU 50. Film dosimetry was used to show the dose pattern at the field edge produced by the two techniques.Results:Dose to PTV did not differ between technique A and B. Median dose to Vrectum was 82.6% for technique A and 77.3% for technique B (p < 0.001). Technique A irradiates a larger Vrectum than technique B being significant for all isodose levels tested. Median dose to Vbladder did not differ for technique A and B (p > 0.05).Conclusion:The presented technical modification is an effective method to blur the staggered dose distribution that results, when the MLC is conventionally stepped to adapt to the dorsal, irregular PTV border in irradiation of prostate. Especially for irradiation to escalated dose levels, this modification may reduce the dose to the rectum and thus the rectal side effects in comparison to the conventional MLC fields.Hintergrund und Ziel:Eine Modifikation der Bestrahlungstechnik beim Prostatakarzinom wird vorgestellt, die den mehrstufigen Dosisverlauf am Feldrand ausgleicht, wie er bei Verwendung eines Multileaf-Kollimators (MLC) entsteht.Material and Methodik:Zehn Patienten wurden in die Analyse einbezogen. Mittels eines dreidimensionalen Bestrahlungsplanungssystems (Helax TMS 6.1B) wurden die Bestrahlungstechniken für einen 18-MV-Linearbeschleuniger (Primus 1, Siemens) berechnet. Als „volumes of interest“ (VOI) wurden das Planungszielvolumen (PTV; Prostataregion inkl. Samenblasen) sowie das Volumen von Rektum (Vrectum) und Harnblase (Vbladder) definiert. Zwei Vierfeldertechniken (Gantry: 0°, 90°, 180°, 270°) wurden unter Verwendung des „beam’s eye view“ geplant. Bei Technik A wurde der MLC in jedem Feld bei einem Kollimatorwinkel von 0° an das PTV angepasst, bei Technik B wurde der Kollimatorwinkel der seitlichen Felder so optimiert, dass sich die in den seitlichen Feldern entstehenden Stufen gegenseitig ausglichen. Die Dosis-Volumen-Histogramme von PTV, Vrectum und Vbladder wurden ausgewertet. Die Dosisangabe bezieht sich auf den Referenzpunkt gemäß ICRU 50. Durch Filmdosimetrie wurde der Dosisverlauf am Feldrand bei beiden Techniken überprüft.Ergebnisse:Die Dosis im PTV unterschied sich bei Technik A und B nicht. Die mediane Dosis in Vrectum betrug 82,6% für Technik A und 77,3% für Technik B (p < 0,001). Die Werte für Vrectum waren in allen untersuchten Dosisbereichen für Technik A größer als für Technik B. Die mediane Dosis in Vbladder unterschied sich bei beiden Techniken nicht (p > 0,05).Schlussfolgerung:Die vorgestellte Modifikation ist eine einfache und effektive Methode zum Ausgleich der stufigen Feldränder und Dosisverläufe, wie sie bei der Verwendung von MLC entstehen. Bei der Bestrahlung des Prostatakarzinoms ist dadurch eine Dosisreduktion im Bereich des Rektums mit evtl. reduzierten Nebenwirkungen möglich.

3D-CT-geplante interstitielle HDR-Brachytherapie + perkutane Bestrahlung und Chemotherapie bei inoperablen Pankreaskarzinomen

PURPOSE Clinical experiences in interstitial 192-iridium HDR brachytherapy for the treatment of unresectable pancreatic carcinoma are presented. Brachytherapy has been used as boost irradiation in a multimodality treatment concept together with external radiotherapy and simultaneous chemotherapy. Practicability during clinical routine, tolerability and toxicity of treatment are investigated. PATIENTS AND METHODS Nineteen patients (9 female, 10 male, median age 67 years) with unresectable carcinoma of the pancreas have been treated with interstitial brachytherapy. Distribution according to UICC stages showed 4, 10 and 5 patients in stage II to IV respectively. In all cases afterloading technique with 192-iridium in HDR-modus was used. A total dose of 10 to 34 Gy to the reference isodose was delivered (single dose 1.88 to 5 Gy, median 2.5 Gy). Brachytherapy was followed by external radiotherapy, delivering an additional dose of 40 to 58 Gy. Nine patients received simultaneous chemotherapy (5-fluorouracil, leucovorin). Treatment planning was performed based on CT scans, allowing spatial correlation of isodose curves to the patients anatomy. RESULTS Median survival time was 6 months. A trend of lower survival rates with advanced stage of disease (median survival stage IV 4 months, stage II and III 6.5 months) was seen. Local control rate was 70%. Brachytherapy treatment was well tolerated, severe acute side effects were not observed. One patient developed pancreatic fistulae 4 months and 1 patient a gastric ulcer 7 months after treatment. Pain release was achieved in all patients. CONCLUSIONS 192-iridium HDR-brachytherapy is an effective tool in the treatment of unresectable pancreatic carcinoma with a high rate of local control and a low rate of side effects and is comparable IORT or seed implantation.ZusammenfassungZielUntersuchung der Praktikabilität, Verträglichkeit und Nebenwirkungen der interstitiellen 192-Iridium-HDR-Brachytherapie im Afterloadingverfahren in der Behandlung des nichtresektablen Pankreaskarzinoms. Die Brachytherapie wurde dabei als Boostbehandlung im Rahmen eines multimodalen therapiekonzepts, bestehend aus interstiteller Brachytherapie, perkutaner Radiatio und simultaner Chemotherapie, eingesetzt.Patienten und Methoden19 Patienten (neun Frauen, zehn Männer) mit einem inoperablen Adenokarzinom des Pankreas (UICC-Stadium IV n=5, Stadium III n=10, Stadium II n=4) im Alter von median 67 Jahren wurden mit einer interstitiellen Brachytherapie mit 192-Iridium HDR im Afterloadingverfahren behandelt. Die auf die Referenzisodose eingestrahlten Dosen lagen zwischen 10 und 34 Gy, bei Einzeldosen von 1,88 bis 5 Gy (median 2,0 Gy). Der interstitiellen Therapie schloß sich eine perkutane Radiatio mit Gesamtdosen zwischen 40 und 58 Gy an. Bei neun Patienten wurde zusätzlich eine Chemotherapie mit 5-Fluorouracil und Leucovorin appliziert. Für die interstitielle Brachytherapie wurde ein CT-gestütztes Planungsverfahren angewandt, das eine räumliche Zuordnung der Isodosenverteilung zur Patientenanatomie gestattet.ErgebnisIm Patientenkollektiv wurde eine mediane Überlebenszeit von sechs Monaten beobachtet, wobei sich ein Trend zur Abhängigkeit der Überlebenszeit vom Stadium der Tumorerkrankung zeigt (mediane Überlebenszeit Stadium IV vier Monate, Stadium II und III 6,5 Monate). Die lokale Tumorkontrollrate lag bei etwa 70%. Die Therapie zeichnete sich durch eine gute Verträglichkeit aus. Schwerwiegende akute Nebenwirkungen wurden nicht beobachtet. Eine Pankreasfistelung wurde vier Monate und ein unkompliziertes Magenulkus sieben Monate nach Therapiebeginn beobachtet. Bei allen Patienten konnte eine rasche und anhaltende Schmerzlinderung erreicht werden.SchlußfolgerungDie 3D-CT-geplante interstitielle HDR-Brachytherapie zeichnet sich beim nichtresektablen Pankreaskarzinom durch die geringe Nebenwirkungsrate im Vergleich zu konkurrierenden Verfahren wie der IORT und der interstitiellen Seedimplantation aus. Trotz der hohen lokalen Kontrollrate kann durch die frühzeitig einsetzende Fernmetastasierung keine Steigerung der medianen Überlebenszeit im Vergleich mit konkurrierenden Therapieverfahren erreicht werden.AbstractPurposeClinical experiences in interstitial 192-iridium HDR brachytherapy for the treatment of unresectable pancreatic carcinoma are presented. Brachytherapy has been used as boost irradiation in a multimodality treatment concept together with external radiotherapy and simultaneous chemotherapy. Practicability during clinical routine, tolerability and toxicity of treatment are investigated.Patients and MethodsNineteen patients (9 female, 10 male, median age 67 years) with unresectable carcinoma of the pancreas have been treated with interstitial brachytherapy. Distribution according to UICC stages showed 4, 10 and 5 patients in stage II to IV respectively. In all cases afterloading technique with 192-iridium in HDR-modus was used. A total dose of 10 to 34 Gy to the reference isodose was delivered (single dose 1.88 to 5 Gy, median 2.5 Gy). Brachytherapy was followed by external radiotherapy, delivering an additional dose of 40 to 58 Gy. Nine patients received simulatenous chemotherapy (5-fluorouracil, leucovorin). Treatment planning was performed based on CT scans, allowing spatial correlation of isodose curves to the patient’s anatomy.ResultsMedian survival time was 6 months. A trend of lower survival rates with advanced stage of disease (median survival stage IV 4 months, stage II and III 6.5 months) was seen. Local control rate was 70%. Brachytherapy treatment was well tolerated, severe acute side effects were not observed. One patient developed pancreatic fistulae 4 months and 1 patient a gastric ulcer 7 months after treatment. Pain release was achieved in all patients.Conclusions192-iridium HDR-brachytherapy is an effective tool in the treatment of unresectable pancreatic carcinoma with a high rate of local control and a low rate of side effects and is comparable IORT or seed implantation.

An Interlaced IMRT Technique for Elongated Tumor Volumes

Treatment of large target volumes with intensity modulated radiotherapy (IMRT) can be restricted by the maximum field size of the multileaf collimator (MLC). In this work, a straightforward technique for MLC-based IMRT is presented, which is generally applicable and does not depend on the capabilities of the linear accelerators IMRT delivery system. A dual isocenter technique was developed that maximizes beam overlap. The beams at the first isocenter are arranged such that they interlace with the beams at the second isocenter. All beams contribute to the overlap region, whereas only some contribute to the superior and some to the inferior part of the target. The interlaced technique (9 beams) was compared with an alternative more complex approach (14 beams) for a head-and-neck case with simultaneous integrated boost and 3 different dose levels. The plans were compared in terms of complexity, dosimetry, and the effect of inaccurate translation between the isocenters. The interlaced and the more complex IMRT technique resulted in nearly identical dose distributions without clinically relevant differences. The total number of monitor units (MUs) was comparable with more MUs per segment for the interlaced technique. For the interlaced technique, the number of segments <or=5 MU was reduced by 43%. Simulation of isocenter setup errors of +/-1, +/-2, and +/-3 mm revealed maximum dose point errors of 1.8%, 3.8%, and 5.4% in the target volume for the interlaced technique. The interlaced IMRT technique resulted in an equivalent plan to the more complex technique without compromising the dose distribution. The technique is less complex and is robust against inaccurate isocenter translations of up to +/-1 mm. Due to the versatility of the technique, it can easily be applied to other anatomical regions and is well suited for clinical routine usage.

Implementing Volumetric Modulated Arc Therapy (VMAT): Initial Dosimetric Results for Retrospective Patient Study

Purpose: The aim of this work is to compare and evaluate the quality of treatment techniques: step-and shoot intensity modulation (IMRT) with Volumetric Modulated Arc Therapy (VMAT).