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Purpose Image-guided radiation therapy could benefit from implementing adaptive radiation therapy (ART) techniques. A cycle-generative adversarial network (cycle-GAN)-based cone-beam computed tomography (CBCT)-to-synthetic CT (sCT) conversion algorithm was evaluated regarding image quality, image segmentation and dosimetric accuracy for head and neck (H&N), thoracic and pelvic body regions. Methods Using a cycle-GAN, three body site-specific models were priorly trained with independent paired CT and CBCT datasets of a kV imaging system (XVI, Elekta). sCT were generated based on first-fraction CBCT for 15 patients of each body region. Mean errors (ME) and mean absolute errors (MAE) were analyzed for the sCT. On the sCT, manually delineated structures were compared to deformed structures from the planning CT (pCT) and evaluated with standard segmentation metrics. Treatment plans were recalculated on sCT. A comparison of clinically relevant dose-volume parameters (D98, D50 and D2 of the target volume) and 3D-gamma (3%/3mm) analysis were performed. Results The mean ME and MAE were 1.4, 29.6, 5.4 Hounsfield units (HU) and 77.2, 94.2, 41.8 HU for H&N, thoracic and pelvic region, respectively. Dice similarity coefficients varied between 66.7 ± 8.3% (seminal vesicles) and 94.9 ± 2.0% (lungs). Maximum mean surface distances were 6.3 mm (heart), followed by 3.5 mm (brainstem). The mean dosimetric differences of the target volumes did not exceed 1.7%. Mean 3D gamma pass rates greater than 97.8% were achieved in all cases. Conclusions The presented method generates sCT images with a quality close to pCT and yielded clinically acceptable dosimetric deviations. Thus, an important prerequisite towards clinical implementation of CBCT-based ART is fulfilled.

BackgroundHypofractionation is increasingly being applied in radiotherapy for prostate cancer, requiring higher accuracy of daily treatment deliveries than in conventional image-guided radiotherapy (IGRT). Different adaptive radiotherapy (ART) strategies were evaluated with regard to dosimetric benefits.MethodsTreatments plans for 32 patients were retrospectively generated and analyzed according to the PACE-C trial treatment scheme (40 Gy in 5 fractions). Using a previously trained cycle-generative adversarial network algorithm, synthetic CT (sCT) were generated out of five daily cone-beam CT. Dose calculation on sCT was performed for four different adaptation approaches: IGRT without adaptation, adaptation via segment aperture morphing (SAM) and segment weight optimization (ART1) or additional shape optimization (ART2) as well as a full re-optimization (ART3). Dose distributions were evaluated regarding dose-volume parameters and a penalty score.ResultsCompared to the IGRT approach, the ART1, ART2 and ART3 approaches substantially reduced the V37Gy(bladder) and V36Gy(rectum) from a mean of 7.4cm3and 2.0cm3to (5.9cm3, 6.1cm3, 5.2cm3) as well as to (1.4cm3, 1.4cm3, 1.0cm3), respectively. Plan adaptation required on average 2.6 min for the ART1 approach and yielded doses to the rectum being insignificantly different from the ART2 approach. Based on an accumulation over the total patient collective, a penalty score revealed dosimetric violations reduced by 79.2%, 75.7% and 93.2% through adaptation.ConclusionTreatment plan adaptation was demonstrated to adequately restore relevant dose criteria on a daily basis. While for SAM adaptation approaches dosimetric benefits were realized through ensuring sufficient target coverage, a full re-optimization mainly improved OAR sparing which helps to guide the decision of when to apply which adaptation strategy.

Background and purpose: Reported plan quality improvements with autoplanning of radiotherapy of the prostate and seminal vesicles are poor. A system for automated multi-criterial planning has been validated for this treatment in a large international multi-center study. The system is configured with training plans using a mechanism that strives for quality improvements relative to those plans. Material and methods: Each of the four participating centers included thirty manually generated clinical Volumetric Modulated Arc Therapy prostate plans (manVMAT). Ten plans were used for autoplanning training. The other twenty were compared with an automatically generated plan (autoVMAT). Plan evaluations considered dosimetric plan parameters and blinded side-by-side plan comparisons by clinicians. Results: With equivalent Planning Target Volume (PTV) V95%, D2%, D98%, and dose homogeneity autoVMAT was overall superior for rectum with median differences of 3.4 Gy (p

Background/purpose To quantify the risk of radiation-induced optic neuropathy (RION) after stereotactic/image-guided positioning and intensity-modulated radiotherapy (IMRT) with ≥50 Gy to the anterior visual pathway (AVP). Methods Patients irradiated with ≥50 Gy to the AVP using stereotactic/image-guided positioning between 2002 and 2011 in Mannheim were identified. Detailed dosimetric data were collected and patients or family members were retrospectively asked to rate visual acuity and visual disorders. Results 125 patients fulfilled the eligibility criteria. Average maximum equivalent point dose (Dmax-EQD-2[α/β=1.6]) to the AVP was 53.1 ± 3.9 Gy. 99 patients received ≥50 Gy bilaterally (chiasm or both optic nerves), resulting in 224 (99x2 bilateral plus 26 unilateral) visual-fields-at-risk (VFAR) for RION. Eighty-two patients provided pre/post-IMRT visual status information (n = 151 VFARs). Permanent visual deterioration occurred in 18 (22%) patients. In seven, visual deterioration was possibly related to radiotherapy (two-sided deterioration in one patient) for a crude incidence of 8.5% (7/82 patients) and 5.3% (8/151 VFARs). Two cases were caused by chronic keratitis/conjunctivitis; in five patients RION could not be excluded (one two-sided). In one of 13 patients with Dmax-EQD-2 > 58 Gy, RION could not be excluded. In all affected patients, visual acuity post-IMRT had decreased only mildly (1–2 points on the 5-point-scale). One patient with relevant baseline visual impairment (3/5) developed unilateral blindness (crude incidence of blindness on patient-/VFAR-level: 1.2% and 0.66%; competing risk-adjusted/actuarial 24-month incidence: patient/VFAR-level: 1.8% and 0.95%). Conclusion Risk of RION was low in this cohort with accurate positioning and precise dosimetric information. Less conservative tolerance doses may be considered in patients with high risk of recurrence.

An increasing number of patients undergoing radiotherapy (RT) have cardiac implantable electronic devices [CIEDs, cardiac pacemakers (PMs) and implanted cardioverters/defibrillators (ICDs)]. Ionizing radiation can cause latent and permanent damage to CIEDs, which may result in loss of function in patients with asystole or ventricular fibrillation. Reviewing the current literature, the interdisciplinary German guideline (DEGRO/DGK) was developed reflecting patient risk according to type of CIED, cardiac condition, and estimated radiation dose to the CIED. Planning for RT should consider the CIED specifications as well as patient-related characteristics (pacing-dependent, previous ventricular tachycardia/fibrillation). Antitachyarrhythmia therapy should be suspended in patients with ICDs, who should be under electrocardiographic monitoring with an external defibrillator on stand-by. The beam energy should be limited to 6 (to 10) MV CIEDs should never be located in the beam, and the cumulative scatter radiation dose should be limited to 2 Gy. Personnel must be able to respond adequately in the case of a cardiac emergency and initiate basic life support, while an emergency team capable of advanced life support should be available within 5 min. CIEDs need to be interrogated 1, 3, and 6 months after the last RT due to the risk of latent damage.

Background Intraoperative radiotherapy (IORT) using the INTRABEAM ® system promises a flexible use regarding radiation protection compared to other approaches such as electron treatment or HDR brachytherapy with 192 Ir or 60 Co. In this study we compared dose rate measurements of breast- and Kypho-IORT with C-arm fluoroscopy which is needed to estimate radiation protection areas. Materials and Methods C-arm fluoroscopy, breast- and Kypho-IORTs were performed using phantoms (silicon breast or bucket of water). Dose rates were measured at the phantom's surface, at 30 cm, 100 cm and 200 cm distance. Those measurements were confirmed during 10 Kypho-IORT and 10 breast-IORT patient treatments. Results The measured dose rates were in the same magnitude for all three paradigms and ranges from 20 μSv/h during a simulated breast-IORT at two meter distance up to 64 mSv/h directly at the surface of a simulated Kypho-IORT. Those measurements result in a circle of controlled area (yearly doses >6 mSv) for each paradigm of about 4 m ± 2 m. Discussion/ Conclusions All three paradigms show comparable dose rates which implies that the radiation protection is straight forward and confirms the flexible use of the INTRABEAM ® system.

Background and purpose We developed a simple and robust total body irradiation (TBI) method for standard treatment rooms that obviates the need for patient translation devices. Methods and materials Two generic arcs with rectangular segments for a patient thickness of 16 and 20 cm (arc16/arc20) were generated. An analytical fit was performed to determine the weights of the arc segments depending on patient thickness and gantry angle. Stability and absolute dose for both arcs were measured using EBT3 films in a range of solid water slab phantom thicknesses. Additionally ionization chamber measurements were performed every 10 cm at a source surface distance (SSD) of ∼200 cm. Results The measured standard deviation for arc16 is ±3% with a flatness ⩽9.0%. Arc20 had a standard deviation of ±3% with a flatness ⩽7.3% for all measured thicknesses. The theoretical curves proved to be accurate for the prediction of the segment weightings for the two arcs. In vivo measurements for the first 22 clinical patients showed a dose deviation of less than 3%. Conclusions Arc therapy is a convenient and stable method for TBI. This cost-effective approach has been introduced clinically, obviating the need for field patches and to physically move the patient.

Purpose Second cancer risk after breast conserving therapy is becoming more important due to improved long term survival rates. In this study, we estimate the risks for developing a solid second cancer after radiotherapy of breast cancer using the concept of organ equivalent dose (OED). Materials and methods Computer-tomography scans of 10 representative breast cancer patients were selected for this study. Three-dimensional conformal radiotherapy (3D-CRT), tangential intensity modulated radiotherapy (t-IMRT), multibeam intensity modulated radiotherapy (m-IMRT), and volumetric modulated arc therapy (VMAT) were planned to deliver a total dose of 50Gy in 2Gy fractions. Differential dose volume histograms (dDVHs) were created and the OEDs calculated. Second cancer risks of ipsilateral, contralateral lung and contralateral breast cancer were estimated using linear, linear-exponential and plateau models for second cancer risk. Results Compared to 3D-CRT, cumulative excess absolute risks (EAR) for t-IMRT, m-IMRT and VMAT were increased by 2±15%, 131±85%, 123±66% for the linear-exponential risk model, 9±22%, 82±96%, 71±82% for the linear and 3±14%, 123±78%, 113±61% for the plateau model, respectively. Conclusion Second cancer risk after 3D-CRT or t-IMRT is lower than for m-IMRT or VMAT by about 34% for the linear model and 50% for the linear-exponential and plateau models, respectively.

Objectives Dosimetric control of staff exposure during interventional procedures under fluoroscopy is of high relevance. In this paper, a novel ray casting approximation of radiation transport is presented and the potential and limitation vs. a full Monte Carlo transport and dose measurements are discussed. Method The x-ray source of a Siemens Axiom Artix C-arm is modeled by a virtual source model using single Gaussian-shaped source. A Geant4-based Monte Carlo simulation determines the radiation transport from the source to compute scatter from the patient, the table, the ceiling and the floor. A phase space around these scatterers stores all photon information. Only those photons are traced that hit a surface of phantom that represents medical staff in the treatment room, no indirect scattering is considered; and a complete dose deposition on the surface is calculated. To evaluate the accuracy of the approximation, both experimental measurements using Thermoluminescent dosimeters (TLDs) and a Geant4-based Monte Carlo simulation of dose depositing for different tube angulations of the C-arm from cranial-caudal angle 0° and from LAO (Left Anterior Oblique) 0°–90° are realized. Since the measurements were performed on both sides of the table, using the symmetry of the setup, RAO (Right Anterior Oblique) measurements were not necessary. Results The Geant4-Monte Carlo simulation agreed within 3% with the measured data, which is within the accuracy of measurement and simulation. The ray casting approximation has been compared to TLD measurements and the achieved percentage difference was −7% for data from tube angulations 45°–90° and −29% from tube angulations 0°–45° on the side of the x-ray source, whereas on the opposite side of the x-ray source, the difference was −83.8% and −75%, respectively. Ray casting approximation for only LAO 90° was compared to a Monte Carlo simulation, where the percentage differences were between 0.5–3% on the side of the x-ray source where the highest dose usually detected was mainly from primary scattering (photons), whereas percentage differences between 2.8–20% are found on the side opposite to the x-ray source, where the lowest doses were detected. Dose calculation time of our approach was 0.85 seconds. Conclusion The proposed approach yields a fast scatter dose estimation where we could run the Monte Carlo simulation only once for each x-ray tube angulation to get the Phase Space Files (PSF) for being used later by our ray casting approach to calculate the dose from only photons which will hit an movable elliptical cylinder shaped phantom and getting an output file for the positions of those hits to be used for visualizing the scatter dose propagation on the phantom surface. With dose calculation times of less than one second, we are saving much time compared to using a Monte Carlo simulation instead. With our approach, larger deviations occur only in regions with very low doses, whereas it provides a high precision in high-dose regions.

Immer komplexere Bestrahlungstechniken wie z. B. dynamische Techniken sind nur noch digital und bildgesteuert sinnvoll einsetzbar. Dadurch erhohen sich standig die Anforderungen an die Bilddokumentation und -archivierung. Diese Arbeit soll detailliert die aktuellen Anforderungen an das Bildmanagement in der Radioonkologie und mogliche Bildadministrationsstrategien darstellen. Es werden die Grundlagen der Bildspeicherung und -administration (DICOM-Standard, Besonderheiten in der Strahlentherapie) entlang des typischen Patientenpfads beschrieben (demografische Daten, Bestrahlungsplanung, Signatur/Approval und Archivierung von Plan- und Bildinformationen). Verschiedene Strategien des Bildmanagements werden konzeptionell gegenubergestellt (applikationsbezogene Bildarchivierung vs. integraler Ansatz mit zentraler Datenspeicherung in einem DICOM-RT-fahigen PACS unter Steuerung eines Radioonkologie-Informationssystems (ROKIS)). Anforderungen an die Infrastruktur (Speicherbedarf abhangig vom Bildaufkommen etc.) werden diskutiert. Applikationsbezogenes Bildmanagement ermoglicht gegenwartig jeweils unmittelbar den vollumfanglichen Zugriff auf Bilddaten einschlieslich aller relevanten Zusatze. Dieser Ansatz ist aber aufgrund zu erwartender Systemmigrationen wenig zukunftssicher. Eine zentrale, patienten- und behandlungsschrittbezogene und primar applikationsunabhangige Bildarchivierung ist daher, trotz gelegentlicher Schwierigkeiten bei der Visualisierung bestimmter Datenelemente, vorzuziehen. Die Speicherung von Bilddaten im DICOM-Format ist unabdingbare Voraussetzung.

Volumetric modulated arc therapy (VMAT) has the potential to deliver dose distributions comparable to the established intensity-modulated radiotherapy techniques for a multitude of target paradigms. Prior to implementing VMAT into their clinical routine in December 2008, the authors evaluated the dose calculation/delivery accuracy of 24 sample VMAT plans (prostate and anal cancer target paradigms) with film and ionization dosimetry. After the start of the clinical program, in vivo measurements with a rectal probe were performed.The VMAT plans were generated by the treatment-planning system (TPS) ERGO++ (Elekta, Crawley, UK) and transferred to a phantom. Film dosimetry was performed with Kodak EDR2 films, and evaluated with dose profiles and gamma-index analysis. Appropriate ionization chambers were used for absolute dose measurements in the phantom and for in vivo measurements. The ionization chamber was used with localization of the measurement volume based on positioning cone-beam computed tomography.Plans were transferred from ERGO++ to the record and verify (RV) system/linear accelerator (linac). The absolute dose deviations recorded with the ionization chamber were 1.74% +/- 1.62% across both indications. The gamma-index analysis of the film dosimetry showed no deviation3%/3 mm in the high-dose region. On in vivo measurements, a deviation between calculation and measurement of 2.09% +/- 2.4% was recorded, when the chamber was successfully positioned in the high-dose region.VMAT plans can be planned and treated reproducibly in high quality after the commissioning of the complete delivery chain consisting of TPS, RV system and linac. The results of the individual plan verification meet the commonly accepted requirements. The first in vivo measurements confirm the reproducible precision of the delivered dose during clinical treatments.

Purpose Postoperative intravaginal brachytherapy for endometrial carcinoma is usually performed with 192 Ir high-dose rate (HDR) afterloading. A potential alternative is treatment with a broadband 50kV X-ray point source, the advantage being its low energy and the consequential steep dose gradient. The aim of this study was to create and evaluate a homogeneous cylindrical energy deposition around a newly designed vaginal applicator. Methods and Materials To create constant isodose layers along the cylindrical plastic vaginal applicator, the source (INTRABEAM system) was moved in steps of 17–19.5 mm outward from the tip of the applicator. Irradiation for a predetermined time was performed at each position. The axial shift was established by a stepping mechanism that was mounted on a table support. The total dose/dose distribution was determined using film dosimetry (Gafchromic EBT) in a "solid water" phantom. The films were evaluated with Mathematica 5.2 and OmniPro-I'mRT 1.6. The results (dose D0/D5/D10 in 0/5/10 mm tissue depth) were compared with an 192 Ir HDR afterloading plan for multiple sampling points around the applicator. Results Three different dose distributions with lengths of 3.9–7.3 cm were created. The irradiation time based on the delivery of 5/7 Gy to a 5 mm tissue depth was 19/26 min to 27/38 min. D0/D5/D10 was 150%/100%/67% for electronic brachytherapy and 140%/100%/74% for the afterloading technique. The deviation for repeated measurements in the phantom was Conclusions It is possible to create a homogeneous cylindrical dose distribution, similar to 192 Ir HDR afterloading, through the superimposition of multiple spherical dose distributions by stepping a kilovolt point source.

Background and Purpose— Animal models developed in rats and mice have become indispensable in preclinical cerebrovascular research. Points of interest include the investigation of the vascular bed and the morphology and function of the arterial, capillary, and venous vessels. Because of their extremely small caliber, in vivo examination of these vessels is extremely difficult. In the present study we have developed a method to provide fast 3D in vivo analysis of cerebral murine vessels using volume computed tomography-angiography (vCTA). Methods— Using an industrial X-ray inspection system equipped with a multifocus cone beam X-ray source and a 12-bit direct digital flatbed detector, high-speed vCTA (180° rotation in 40 s. at 30 fps) was performed in anesthetized mice. During the scan an iodinated contrast agent was infused via a tail vein. Images were reconstructed using a filtered backprojection algorithm. Image analysis was performed by maximum intensity projection (MIP) and 3D volume reconstruction. Results— All mice tolerated i.v. injection of the iodinated contrast agent well. Smallest achievable voxel size of raw data while scanning the whole neurocranium was 16 μm. Anatomy of cerebral vessels was assessable in all animals, and anatomic differences between mouse strains could easily be detected. Mean vessel diameter was measured in C57BL/6 and BALBc mice. Changes of vessel caliber were assessable by repeated vCTA. Conclusions— Ultra fast in vivo vCTA of murine cerebral vasculature is feasible at resolutions down to 16 μm. The technique allows the assessment of vessel caliber changes in living mice, thus providing an interesting tool to monitor different features such as vasospasm or vessel patency.

Der Arbeitsablauf (Workflow) in der Radiotherapie (RT) ist gegenwartig durch neue Techniken und Behandlungsparadigmen wie intensitatsmodulierte Radiotherapie (IMRT) und zunehmende bildgestutzte Radiotherapie (IGRT [„image-guided radiotherapy“]) im Umbruch. Daraus resultiert eine starke Zunahme von Daten verschiedener Datenklassen. Dies erfordert fur die Steuerbarkeit einer Abteilung eine zunehmende patienten- und behandlungsserienzentrierte Integration verschiedener Systeme. Der Workflow in einer RT-Abteilung ist multidimensional und multidirektional und umfasst mindestens funf Datenklassen (RT-/Bestrahlungsdaten, patientenbezogene Dokumente wie z.B. Befunde und Arztbriefe, arztliche Akteneintrage, Bilddaten im DICOM-Format [Digital Imaging and Communications in Medicine] sowie Non-DICOM-Bilddaten). Diese Daten mussen sequentiell, u.U. auch im Rahmen von adaptiven Feedbackschleifen in die Patientenhistorie eingebunden werden. Dieses Vorgehen kontrastiert stark mit einer diagnostischen Radiologieabteilung, in der im Wesentlichen DICOM-Bilddaten und Befunde erzeugt werden und im Zugriff bleiben. Diese Daten mussen nach Abschluss des Prozesses kaum noch manipuliert werden. Es handelt sich also um einen uberwiegend unidirektionalen Prozess. Im Gegensatz zu dieser innerhalb der diagnostischen Radiologie etablierten Standardkombination aus Radiologie-Informationssystem (RIS) und Picture Archiving and Communication System (PACS) muss ein integriertes elektronisches Radio-Onkologie-Klinik-Informationssystem (ROKIS) mit Moglichkeiten zur Speicherung/Administration von Bilddaten zusatzliche gesetzliche Rahmenbedingungen berucksichtigen (langere Speicherfristen, prozesssichere Dokumentation von wesentlichen Therapieentscheidungen sowie Abzeichnen von Bestrahlungsplanen und Dosisverschreibungen, komplexe Patienteneinverstandnisse etc.). Der Ubergang zu einer papier- und filmlosen Arbeitsumgebung in der Medizin, insbesondere in der Strahlentherapie, ist vor dem Hintergrund notwendiger Effizienzsteigerungen und steigender Archivierungskosten unausweichlich. Die vorliegende Ubersichtsarbeit stellt eine mogliche apparative und organisatorische Struktur fur ein ROKIS unter Fuhrung eines Krankenhaus-Informationssystems (KIS) vor. Ein solches System vereinigt in einer Kombination und Erweiterung der originaren Merkmale eines Record-and-Verify-(R&V-)Systems Merkmale einer elektronischen Patienten-/Fallakte (ePA) und integriertes Bildmanagement mit einem PACS.

Quality assurance of external beam (radio)therapy (EBT) requires tools with specific characteristics. A radiochromic film dubbed “Gafchromic™ EBT” (G-EBT) that is particularly suited for external beam therapy because of its features was introduced in 2004. Its characteristics, especially the high spatial resolution, make it suitable for measurement of dose distributions in radiotherapy, especially intensity-modulated radiation therapy (IMRT). While several aspects of the film characteristics have been previously reported separately, we present a comprehensive evaluation centered on practical IMRT verification, leading to an optimized protocol. Therefore the constancy within one batch, the relationship between optical density (OD) and dose (dose range between 1.4Gy and 8.4Gy) and the dose rate dependence for four dose rates (55, 108, 217, 441 MU/min) were investigated. In addition to these characteristics, energy dependence between two energies (50 kV and 6 MV), tissue equivalency, post irradiation coloration over one month, pressure and temperature sensitivity were evaluated. We then optimized the protocol using the G-EBT films, in combination with an EPSON-Expression™ 1680pro flatbed scanner, for IMRT QA, while either striving to keep the compound error as small as possible or trying to reduce evaluation time. As a basis for this protocol optimization, the characteristics of the scanner (such as inhomogeneity of the scanning field) and its software (such as consequences of extracting only the red color channel) had to be determined first. The interaction of film and scanner (variation of the OD depending on the scanning direction or the scanning resolution) was assessed as well. Using the optimized protocol for IMRT QA, the compound error could be reduced to approximately 2% for a quality-driven approach and maximum 5.5% for an approach attempting to reduce procedure time. While the quality-driven approach provides appropriate accuracy for individual patient QA, the procedure-time driven approach can only be used for preliminary measurements.

Die intraoperative Radiotherapie (IORT) des Tumorbettes mit dem INTRABEAM-System (Carl Zeiss, Oberkochen) wahrend der brusterhaltenden Operation wird derzeit in einer randomisierten klinischen Studie (TARGIT) an einem hochselektionierten Patientinnenkollektiv untersucht. Patientinnen >50 Jahre mit einem unifokalen, duktal-invasiven Karzinom

Purpose: To compare different combinations of intensity-modulated radiation therapy (IMRT) system components with regard to quality assurance (QA), especially robustness against malfunctions and dosimetry. Three different treatment-planning systems (TPS), two types of linacs and three multileaf collimator (MLC) types were compared: commissioning procedures were performed for the combination of the TPS Corvus® 5.0 (Nomos) and KonRad® v2.1.3 (Siemens OCS) with the linacs KD2® (Siemens) and Synergy® (Elekta). For PrecisePLAN® 2.03 (Elekta) measurements were performed for Elekta Synergy only. As record and verify (R&V) system Multi-Access v7® (IMPAC) was used. The use of the serial tomotherapy system Peacock® (Nomos) was investigated in combination with the Siemens KD2 linac. In the comparison of calculated to measured dose, problems were encountered for the combination of KonRad and Elekta MLC as well as for the Peacock system. Multi-Access failed to assign the collimator angle correctly for plans with multiple collimator angles per beam. Communication problems of Multi-Access with both linacs were observed, resulting in incorrect recording of the treatment. All reported issues were addressed by the manufacturers. For the commissioning of IMRT systems, the whole chain from the TPS to the linac has to be investigated. Components that passed the commissioning in another clinical environment can have severe malfunctions when used in a new environment. Therefore, not only single components but the whole chain from planning to delivery has to be evaluated in commissioning and checked regularly for QA.

Introduction Intraoperative radiotherapy (IORT) with low-energy X-rays (30–50 KV) is an innovative technique that can be used both for accelerated partial breast irradiation (APBI) and intraoperative boosting in patients affected by breast cancer. Immediately after tumor resection the tumor bed can be treated with low-distance X-rays by a single high dose. Whereas often a geographic miss in covering the boost target occurs with external beam boost radiotherapy (EBRT), the purpose of IORT is to cover the tumor bed safely. This report will focus on the feasibility and technical aspects of the Intrabeam™ device and will summarize our experience with side effects and local control. Materials and methods Between February 2002 and June 2003 57 breast cancer patients, all eligible for breast conserving surgery (BCS), were treated at the Mannheim Medical Center with IORT using the mobile X-ray system Intrabeam™. The patient population in this feasibility study was not homogeneous consisting of 49 patients with primary stage I or II breast cancer, seven with local recurrence after previous EBRT and one with a second primary in a previously irradiated breast. The selection criteria for referral for IORT included tumor size, tumor cavity size, margin status and absence of an extensive intraductal component. The previously irradiated patients with local recurrences and 16 others received IORT as single modality. In all other cases IORT was followed by EBRT with a total dose of 46 Gy in 2-Gy fractions. The intraoperatively delivered dose after tumor resection was 20 Gy prescribed to the applicator surface. EBRT was delivered with a standard two-tangential-field technique using linear accelerators with 6- or 18-MV photons. Patients were assessed every three months by their radiation oncologist or surgeon during the first year after treatment and every six months thereafter. Breast ultrasound for follow-up was done every six months and mammographies once yearly. Acute side effects were scored according to the CTC/EORTC score and late side effects according to the Lent-Soma classification. Results Twenty-four patients received IORT only; eight patients because they had received previous radiotherapy, 16 because of a very favorable risk profile or their own preference. Thirty-three patients with tumor sizes between 1 and 30 mm and no risk factors were treated by IORT as a boost followed by EBRT. The Intrabeam™ system was used for IORT. The Intrabeam source produces 30–50 KV X-rays and the prescribed dose is delivered in an isotropic dose distribution around spherical applicators. Treatment time ranged between 20 and 48 minutes. No severe acute side effects or complications were observed during the first postoperative days or after 12 months. One local recurrence occurred 10 months after surgery plus IORT followed by EBRT. In two patients distant metastases were diagnosed shortly after BCS. Discussion IORT with the Intrabeam system is a feasible method to deliver a single high radiation dose to breast cancer patients. As a preliminary boost it has the advantage of reducing the EBRT course by 1.5 weeks, and as APBI it might be a promising tool for patients with a low risk of recurrence. The treatment is well tolerated and does not cause greater damage than the expected late reaction in normal tissue.

The purpose of this study was to model the distribution of biological effect around a miniature isotropic X-ray source incorporating spherical applicators for single-dose or hypo-fractionated partial-breast intraoperative radiotherapy. A modification of the linear-quadratic formalism was used to calculate the relative biological effectiveness (RBE) of 50 kV X rays as a function of dose and irradiation time for late-reacting normal tissue and tumor cells. The response was modeled as a function of distance in the tissue based on the distribution of equivalent dose and published dose-response data for pneumonitis and subcutaneous fibrosis after single-dose conventional irradiation. Furthermore, the spatial distribution of tumor cell inactivation was assessed. The RBE for late reactions approached unity at the applicator surface but increased as the absorbed dose decreased with increasing distance from the applicator surface. The ED50 for pneumonitis was estimated to be reached at a depth of 6-11 mm in the tissue and that for subcutaneous fibrosis at 3-6 mm, depending on the applicator diameter and whether the effect of recovery was included. Thus lung tissue would be spared because of the thickness of the thorax wall. The RBE for tumor cells was higher than for late-reacting tissue. The applicator diameter is an important parameter in determining the range of tumor cell control in the irradiated tumor bed.

Purpose Data from the randomized Intergroup Trial 116 suggest effectiveness of adjuvant radiochemotherapy in patients with advanced gastric cancer. Late toxicity, however, especially with respect to the kidneys, may pose significant longtime problems. Intensity-modulated radiotherapy (IMRT) may reduce toxicity to organs at risk. To evaluate the relative merits of different IMRT approaches, we performed a plan comparison between a step-and-shoot class solution and an AP-PA setup, a conventional box technique and the Peacock tomotherapy approach. Methods and materials Computed tomographies and structure data from 15 patients who had been treated postoperatively for advanced (T3/T4/N+) gastric cancer at our department formed the basis of our plan comparison study. For each patient data set, 5 plans or plan combinations (conventional 3D plan, AP-PA plan, step-and-shoot IMRT, tomotherapy with 1-cm or 2-cm collimation) were chosen, and evaluation was performed for a total dose of 45 Gy delivered as the median dose to the target volume for each plan or plan combination. Results Median kidney dose generated from the IMRT plans is reduced individually by >50% for the kidney with the highest exposure (usually the left kidney) from 20 to 30 Gy with conventional 3D planning down to values between 8 and 10 Gy for IMRT. On average, median dose to the right kidney is the same for the conventional box technique and IMRT (between 8 and 10 Gy) but lower for the AP-PA technique. In 3 patients, kidney dose might have been ablative for both kidneys with both the AP-PA technique and the box technique, whereas it was acceptable with IMRT. Median dose to the liver was subcritical with all modalities but lowest with AP-PA fields. Differences between step-and-shoot IMRT and tomotherapy plans are small when compared to the differences between IMRT plans and conventional conformal 3D plans. For some patients, however, their body and target diameters obviate treatment with tomotherapy. Treatment time for the step-and-shoot approach and for tomotherapy with 2-cm collimation can be kept Conclusions For postoperative radiotherapy of advanced gastric cancer, step-and-shoot IMRT as well as tomotherapy can deliver efficient doses to target volumes while delivering dose to the kidneys in a fashion that is different from a conventional technique and is clearly advantageous in a small number of patients. An advantage for the majority of patients is likely with the normal tissue complication probability data presented in this series, but, given the uncertainty of the reaction of the kidney to inhomogeneous dose distributions, cannot be considered unequivocal at the moment. Different technical limitations apply to the different IMRT techniques. The choice of approach is therefore determined by departmental circumstances.

Hypofractionated image-guided stereotactic ablative radiotherapy (igSABR) is effective in small lung/liver lesions. Computer-assisted breath-hold reduces intrafraction motion but, as every gating/triggering strategy, reduces the duty cycle, resulting in long fraction times if combined with intensity-modulated radiotherapy (IMRT). 10 MV flattening-filter-free IMRT reduces daily fraction duration to10 min for single doses of 5-20 Gy.

For pre-treatment plan verification of advanced treatment techniques such as intensity-modulated arc therapy, a fast and reliable dosimetric device is required. In this study, we investigated the suitability of MatriXX in different setups for verification of volumetric modulated arc therapy (VMAT) plans. If MatriXX is used in a stationary phantom (MULTICube), the measured dose is dependent on the beam angle. For the first setup (MatriXX/MULTICube), we developed correction factors (CFs) for each detector element (1020 CFs). We investigated the accuracy of these CFs by verifying 12 VMAT plans. In the second setup, we also assessed the suitability of MatriXX in a dedicated holder. Using this setup (MatriXX/Holder), 30 additional VMAT plans were verified. Deviations of up to ∼17% and ∼11% were noted for one of the ion chambers at 90° and 180° gantry positions. The influence of the beam angle dependence (MULTICube) can explicitly be seen when a gamma criterion of 2%/2 mm was chosen. An overall improvement of 4.3% of passing pixels (pp) was noted after applying beam angular-dependent CFs. When the gamma criterion was 3%/3 mm, the %pp was ≥ 95% without and ∼100% with correction. With the second setup, MatriXX/holder, we showed excellent agreement between measurements and calculations. The %pp averaged over all plans (30 VMAT treatment plans) was nearly ∼100%. The combination of MatriXX with MULTICube or with holder proved to be a fast and reliable method for pretreatment verification of arc therapy with sufficient accuracy.

We validate the dosimetric performance of COMPASS®, a novel 3D quality assurance system for verification of volumetric-modulated arc therapy (VMAT) treatment plans that can correlate the delivered dose to the patient's anatomy, taking into account the tissue inhomogeneity. The accuracy of treatment delivery was assessed by the COMPASS® for 12 VMAT plans, and the resulting assessments were evaluated using an ionization chamber and film measurements. Dose–volume relationships were evaluated by the COMPASS® for three additional treatment plans and these were used to verify the accuracy of treatment planning dose calculations. The results matched well between COMPASS® and measurements for the ionization chamber (≤3%) and film (73–99% for gamma(3%/3 mm) < 1 and 98–100% for gamma(5%/5 mm) < 1) for the phantom plans. Differences in dose–volume statistics for the average dose to the PTV were within 2.5% for three treatment plans. For the structures located in the low-dose region, a maximum difference of

Background/Purpose Radiotherapy (RT) volumes for anal cancer are large and of moderate complexity when organs at risk (OAR) such as testis, small bowel and bladder are at least partially to be shielded. Volumetric intensity modulated arc therapy (VMAT) might provide OAR-shielding comparable to step-and-shoot intensity modulated radiotherapy (IMRT) for this tumor entity with better treatment efficiency. Materials and methods Based on treatment planning CTs of 8 patients, we compared dose distributions, comformality index (CI), homogeneity index (HI), number of monitor units (MU) and treatment time (TTT) for plans generated for VMAT, 3D-CRT and step-and-shoot-IMRT (optimized based on Pencil Beam (PB) or Monte Carlo (MC) dose calculation) for typical anal cancer planning target volumes (PTV) including inguinal lymph nodes as usually treated during the first phase (0-36 Gy) of a shrinking field regimen. Results With values of 1.33 ± 0.21/1.26 ± 0.05/1.3 ± 0.02 and 1.39 ± 0.09, the CI's for IMRT (PB-Corvus/PB-Hyperion/MC-Hyperion) and VMAT are better than for 3D-CRT with 2.00 ± 0.16. The HI's for the prescribed dose (HI36) for 3D-CRT were 1.06 ± 0.01 and 1.11 ± 0.02 for VMAT, respectively and 1.15 ± 0.02/1.10 ± 0.02/1.11 ± 0.08 for IMRT (PB-Corvus/PB-Hyperion/MC-Hyperion). Mean TTT and MU's for 3D-CRT is 220s/225 ± 11MU and for IMRT (PB-Corvus/PB-Hyperion/MC-Hyperion) is 575s/1260 ± 172MU, 570s/477 ± 84MU and 610s748 ± 193MU while TTT and MU for two-arc-VMAT is 290s/268 ± 19MU. Conclusion VMAT provides treatment plans with high conformity and homogeneity equivalent to step-and-shoot-IMRT for this mono-concave treatment volume. Short treatment delivery time and low primary MU are the most important advantages.

Purpose Intraoperative radiotherapy (IORT) during breast-conserving surgery (BCS) has been recently introduced using different devices. We report the first 5 years of a single-center experience after introduction of a novel approach to deliver IORT as a tumor bed boost during BCS for breast cancer. Methods and Materials A total of 155 breast cancers in 154 women (median age, 63 years; range, 30–83 years; T1/T2 = 100/55; N0/N+ = 108/47) were treated between February 2002 and December 2007 at the University Medical Center Mannheim, in whom IORT as tumor bed boost was applied using 50-kV X-rays (20 Gy) followed by 46–50 Gy whole-breast external-beam radiotherapy (EBRT). Chemotherapy, if indicated, was given before EBRT. The median interval between BCS plus IORT and EBRT was 40 days. Median follow-up was 34 months (maximum 80 months, 1 patient lost to follow-up). Overall survival and local relapse-free survival were calculated at 5 years using the Kaplan-Meier method. Seventy-nine patients were evaluated at 3-year follow-up for late toxicity according to the Late Effects in Normal Tissues–Subjective, Objective, Management, and Analytic system. Results Ten patients died, 2 had in-breast relapse, and 8 developed distant metastases (5-year overall survival = 87.0%; 5-year local relapse-free survival = 98.5%). Grade 3 fibroses of the tumor bed were detected in 5% of the patients after 3 years. Skin toxicity was mild (telangiectases and hyperpigmentations in approximately 6% each). Conclusions Intraoperative radiotherapy as a tumor bed boost during BCS for breast cancer using low-kilovoltage X-rays followed by EBRT yields low recurrence and toxicity rates.

Introduction Volumetric modulated arc therapy (VMAT), a complex treatment strategy for intensity-modulated radiation therapy, may increase treatment efficiency and has recently been established clinically. This analysis compares VMAT against established IMRT and 3D-conformal radiation therapy (3D-CRT) delivery techniques. Methods Based on CT datasets of 9 patients treated for prostate cancer step-and-shoot IMRT, serial tomotherapy (MIMiC), 3D-CRT and VMAT were compared with regard to plan quality and treatment efficiency. Two VMAT approaches (one rotation (VMAT1x) and one rotation plus a second 200° rotation (VMAT2x)) were calculated for the plan comparison. Plan quality was assessed by calculating homogeneity and conformity index (HI and CI), dose to normal tissue (non-target) and D 95% (dose encompassing 95% of the target volume). For plan efficiency evaluation, treatment time and number of monitor units (MU) were considered. Results For MIMiC/IMRT MLC /VMAT2x/VMAT1x/3D-CRT, mean CI was 1.5/1.23/1.45/1.51/1.46 and HI was 1.19/1.1/1.09/1.11/1.04. For a prescribed dose of 76Gy, mean doses to organs-at-risk (OAR) were 50.69Gy/53.99Gy/60.29Gy/61.59Gy/66.33Gy for the anterior half of the rectum and 31.85Gy/34.89Gy/38.75Gy/38.57Gy/55.43Gy for the posterior rectum. Volumes of non-target normal tissue receiving ⩾70% of prescribed dose (53Gy) were 337ml/284ml/482ml/505ml/414ml, for⩾50% (38Gy) 869ml/933ml/1155ml/1231ml/1993ml and for⩾30% (23Gy) 2819ml/3414ml/3340ml/3438ml /3061ml. D 95% was 69.79Gy/70.51Gy/71,7Gy/71.59Gy/73.42Gy. Mean treatment time was 12min/6min/3.7min/1.8min/2.5min. Conclusion All approaches yield treatment plans of improved quality when compared to 3D-conformal treatments, with serial tomotherapy providing best OAR sparing and VMAT being the most efficient treatment option in our comparison. Plans which were calculated with 3D-CRT provided good target coverage but resulted in higher dose to the rectum.

Purpose Three-dimensional (3D) treatment planning has reduced the cardiac dose in postoperative radiotherapy for breast cancer; however, the overall cardiac toxicity is still an issue because of more aggressive adjuvant treatment. Toxicity models have suggested that a reduction of the heart volume treated to high doses might be particularly advantageous. We compared aperture-based multifield intensity-modulated radiotherapy (IMRT) plans to 3D-planned tangent fields using dose–volume histograms, cardiac toxicity risk, and the robustness to positioning errors. Methods and Materials For 14 computed tomography data sets of patients with left-sided breast cancer (unfavorable thoracic geometry), a 3D treatment plan and an IMRT plan were created. The dose–volume histograms were evaluated for the target and risk organs. Excess risk of cardiac mortality was calculated for both approaches using a relative seriality model. Positioning errors were simulated by moving the isocenter. Results IMRT reduced the maximal dose to the left ventricle by a mean of 30.9% (49.14 vs. 33.97 Gy). The average heart volume exposed to >30 Gy was reduced from 45 cm 3 to 5.84 cm 3 . The mean dose to the left ventricle was reduced by an average of 10.7% (10.86 vs. 9.7 Gy), and the mean heart dose increased by an average of 24% (from 6.85 to 8.52 Gy). The model-based reduction of the probability for excess therapy-associated cardiac death risk was from 6.03% for the 3D plans to 0.25% for the IMRT plans. Conclusion Aperture-based IMRT for left-sided breast cancer significantly reduces the maximal dose to the left ventricle, which might translate into reduced cardiac mortality. Biological modeling might aid in deciding to treat with IMRT but has to be validated prospectively.

Purpose: The shielding of organs at risk (OAR) like testis, small bowel and bladder increases the complexity of a treatment for anal cancer. The new rotation therapy volumetric intensity modulated arc therapy (VMAT) may have the potential to reduce the treatment time while producing a comparable dose distribution as the intensity modulated radiation therapy(IMRT).Method and Materials: CT datasets of 8 patients with anal cancer from our department formed the basis of this study. The routinely applied refined 3D‐Treatment Plan (Masterplan, Theranostic) was compared to a 9 beam step and shoot IMRT (Corvus 6.3, Nomos) and a VMAT plan with 2 rotations generated with ERGO++ 1.6 by Elekta. All three treatment planning systems used the identical CT datasets and the same OAR's. To compare these three techniques, the dose volume histograms (DVH) of PTV and OAR's as well as the total treatment time (TTT) were used. The homogeneity index (HI) and the conformality index (CI) calculated as suggested by the RTOG guidelines were analysed. Results: VMAT provided the best PTV coverage as indicated by the following metrics (isodose as percentage of prescription dose (PD) encompassing 95% of the PTV / percentage of tissue outside the PTV encompassed by 95% of PD). For 3D‐RT the mean values were (94.7±0.6% / 5.4±1.5%), for IMRT (89.8±1% / 0.7±2.6%) and for VMAT (93.7±1% / 2.9±1.3%). The mean CI and HI over all 8 patients was (2.00±0.17, 1.06±0.01) for 3D‐RT, for IMRT (1.56±0.16, 1.15±0.02) and for VMAT (1.71±0.13, 1.09±0.03). The TTT for 3D‐RT (220 seconds) was much shorter than for IMRT (557 seconds). The estimated TTT of the VMAT technique is 180 seconds. Conclusion: The new VMAT technique provides excellent treatment planes with highest conformality and homogeneity. The short treatment delivery time together with low primary monitor units is the most important advantage.

Purpose: VMAT is about to be established clinically on a wide basis and may increase the efficiency of Intensity Modulated Radiotherapy(IMRT)treatment. The goal of this investigation was to compare VMAT to established IMRT delivery techniques of serial Tomotherapy and segmental IMRT for prostate cancer.Method and Materials: Using CT data sets of 9 patients treated for prostate cancer,treatment plans for all three techniques were created. Segmental IMRT was planned for a conventional MLC (Elekta MLCi, 2×40leaves, 1cm) and serial Tomotherapy for the MIMiC Multivane‐Collimator (NOMOS, Corp.), using the Corvus 6.3 (Nomos; Pencil beam). VMAT was planned with ERGO++ R1.6 (3D Line Medical Systems/Elekta; Pencil beam). Segmental IMRT plans with MLC used 7 isotropic beams. Serial Tomotherapy plans were calculated in 1cm mode and for a 300° rotation. VMAT plans were created with a 360° and two 100° rotations. Evaluation of plan quality used metrics of conformity index (CI=Vtissue Dmin/Vtarget), homogeneity index (HI=Dmax/Dprescribed), dose to normal tissue and the isodose which encompasses 95% of the target volume. Results: Median indices for conformity and homogeneity of the Corvus plans were CI 2,34/HI 1,21; MLC based segmental IMRT CI 2,89/HI 1,22; and VMAT plans CI 2,02/HI 1,11. 76Gy were prescribed to the median dose of the PTV. The resulting median doses to organ at risk (OAR) for (MIMiC/MLC/VMAT) were as follows: for anterior rectum (52,2Gy/52,4Gy/60,5Gy), posterior rectum (32,3Gy/33,5Gy/34,3Gy) and bladder (44,9Gy/44,1Gy/53,7Gy). Volumes for 50% of prescribed dose (38Gy) in normal tissue were 1091ml/1583ml/1191ml. Dose encompassing 95% of PTV was (MIMiC/MLC/VMAT) 68,8Gy/66,6Gy/70,7Gy. Median treatment time (MIMiC/MLC/VMAT) was 15min/7,5min/3min. Conclusion: Rotational therapy techniques showed higher conformity, coverage and lower normal tissuedose. Homogeneity and dose to posterior rectum were similar for all approaches. VMAT plans are deliverable within a 3minute time slot which is the most efficient treatment option compared to the other approaches.

Background For patients suffering of recurrent breast cancer within the irradiated breast, generally mastectomy is recommended. The normal tissue tolerance does not permit a second full-dose course of radiotherapy to the entire breast after a second breast-conserving surgery (BCS). A novel option is to treat these patients with partial breast irradiation (PBI). This approach is based on the hypothesis that re-irradiation of a limited volume will be effective and result in an acceptable frequency of side effects. The following report presents a single center experience with intraoperative radiotherapy (IORT) during excision of recurrent breast cancer in the previously irradiated breast. Methods Between 4/02 and 11/06, 15 patients were treated for in-breast recurrences at a median of 10 years (3–25) after previous EBRT (10 recurrences in the initial tumor bed, 3 elsewhere in-breast failures, 2 invasive recurrences after previous DCIS). Additional 2 patients were selected for IORT with new primary breast cancer after previous partial breast EBRT for treatment of Hodgkin's disease. IORT with a single dose of 14.7 – 20 Gy 50 kV X-rays at the applicator surface was delivered with the Intrabeam™-device (Carl Zeiss, Oberkochen, Germany). Results After a median follow-up of 26 months (1–60), no local recurrence occurred. 14 out of 17 patients are alive and free of disease progression. Two patients are alive with distant metastases. One patient died 26 months after BCS/IORT due to pulmonary metastases diagnosed 19 months after BCS/IORT. Acute toxicity after IORT was mild with no Grade 3/4 toxicities and cosmetic outcome showed excellent/good/fair results in 7/7/3 cases. Conclusion IORT for recurrent breast cancer using low energy X-rays is a valuable option for patients with recurrent breast cancer after previous radiotherapy.

Purpose: Intraoperative radiotherapy (IORT) as a boost for breast cancer delivers a high single dose of radiation to a late-reacting tissue; therefore late toxicity is of particular interest, and long-term follow-up is warranted. To date there are only limited data available on breast cancer patients treated with IORT using low energy X-rays. We analyzed toxicity and cosmesis after IORT as a boost with a minimum follow-up of 18 months. Methods and Materials: A total of 73 patients treated with IORT (20 Gy/50 kV X-rays; INTRABEAM [Carl Zeiss Surgical, Oberkochen, Germany]) to the tumor bed during breast-conserving surgery as a boost followed by whole-breast radiotherapy (WBRT, 46 Gy) underwent a prospective, predefined follow-up (median, 25 months; range 18–44 months), including clinical examination and breast ultrasound at 6-months and mammographies at 1-year intervals. Toxicities were documented using the common toxicity criteria (CTC)/European Organization for Research and Treatment of Cancer and the LENT-SOMA score. Cosmesis was evaluated with a score from 1 to 4. Results: The IORT in combination with WBRT was well tolerated, with no Grade 3 or 4 skin toxicities and no telangiectasias. Fibrosis of the entire breast was observed in 5% of the patients. A circumscribed fibrosis around the tumor bed was palpable in up to 27% with a peak around 18 months after therapy and a decline thereafter. The observed toxicitiy rates were not influenced by age, tumor stage, or systemic therapy. The cosmetic outcome was good to excellent in ≥90% of cases. Conclusions: After IORT of the breast using low-energy X-rays, no unexpected toxicity rates were observed during long-term-follow-up.

Background and Purpose: Locoregional relapse is a problem frequently encountered with advanced gastric cancer. Data from the randomized Intergroup trial 116 suggest effectiveness of adjuvant radiochemotherapy, albeit with significant toxicity. The potential of intensity-modulated radiotherapy (IMRT) to reduce toxicity by significantly reducing maximum and median doses to organs at risk while still applying sufficient dose to the target volume in the upper abdomen was studied. Patient and Methods: For a typical configuration of target volumes and organs, a step-and-shoot IMRT plan (eight beam orientations), developed as a class solution for treatment of tumors in the upper abdomen (Figures 1 to 3), a conventional plan, a combination of the conventional plan with a kidney-sparing boost plan, and a conventional plan with noncoplanar ap and pa fields for improved kidney sparing were compared with respect to coverage of target volume and dose to organs at risk with a dose of 45 Gy delivered as the median dose to the target volume. Results: When using the conventional three-dimensionally planned box techniques, the right kidney could be kept below tolerance, but median dose to the left kidney amounted to between 14.8 and 26.9 Gy, depending on the plan. IMRT reduced the median dose to the left kidney to 10.5 Gy, while still keeping the dose to the right kidney < 8 Gy. Liver was spared better with IMRT. Dose to the lungs was not significantly different, and dose to the spinal cord was higher (but well below tolerance) with IMRT. The dose distribution within the target volume was less homogeneous than for the conventional plans. With regard to target coverage, > 90% of prescription dose were delivered to > 90% of target volume with IMRT (Table 1). Conclusion: IMRT has the potential to deliver efficient doses to target volumes in the upper abdomen, while delivering dose to organs at risk in a more advantageous fashion than a conventional technique. For clinical implementation, the possibility of extensive organ motion in the upper abdomen has to be taken into account for treatment planning and patient positioning. The multitude of potential risks related to its application has to be the subject of thorough follow-up and further studies.