H. Wertz

Evaluation of Possible Prostate Displacement Induced by Pressure Applied during Transabdominal Ultrasound Image Acquisition

Background and Purpose:For accurate positioning of the prostate in external radiotherapy, transabdominal ultrasound localization and positioning systems are available. Reports have stated that probe pressure applied during image acquisition causes clinically relevant prostate displacement. The aim of this study was to investigate the prostate displacement due to the pressure applied during transabdominal ultrasound image acquisition with the BAT® ultrasound system.Material and Methods:For ten patients who had undergone iodine-125 seed implantation for brachytherapy of prostate cancer, X-ray simulations were performed before and during ultrasound image acquisition. The iodine seeds are visible on the X-ray images, representing the position of the prostate. The simulator’s crosshair, indicating the isocenter, was used as reference coordinate system. For each patient the change in prostate position was calculated based on the seed positions during and after ultrasound examination.Results:A maximum displacement of the prostate of 2.3 mm in anteroposterior and 1.9 mm in craniocaudal direction and a rotational change of up to 2.5° were observed. If the system was not handled correctly and too much pressure was applied, a shift of the prostate of up to 10 mm could be induced.Conclusion:Compared to the prostate displacement due to changes in rectal filling, which according to Crook et al. can be as much as 1.7 cm, the maximum displacement of less than 0.3 cm caused by the probe pressure is negligible. However, proper education of the staff and preparation of the patient are essential for the safe use of the system.Hintergrund und Ziel:Zur genauen Positionierung der Prostata in der Teletherapie stehen Ultraschall-Lokalisationssysteme zur Verfügung. Ziel der Studie war zu untersuchen, ob der Druck, der während der BAT®-Ultraschallaufnahme ausgeübt wird, eine klinisch relevante Verschiebung der Prostata bewirkt, die den Nutzen eines solchen Systems für die Patientenpositionierung in Frage stellt.Material und Methodik:Von zehn Patienten mit Iod-125-Seed-Implantaten wurden während und nach der Ultraschallaufnahme Röntgensimulationsaufnahmen angefertigt. Die in den Röntgenaufnahmen sichtbaren Seeds repräsentieren die Lage der Prostata. Das Fadenkreuz des Simulators wurde als Referenzkoordinatensystem verwendet. Für jeden Patienten wurde die Lageänderung der Prostata aus der Änderung der Seedpositionen bestimmt.Ergebnisse:Bei korrekter Anwendung des Ultraschallsystems wurde die Prostata maximal bis zu 2,3 mm in anteroposteriorer und 1,9 mm in kraniokaudaler Richtung verschoben und um maximal 2.5° rotiert. Durch falsche Handhabung des Systems mit zu hohem Druck konnte eine Verschiebung der Prostata um bis zu 10 mm bewirkt werden.Schlussfolgerung:Im Vergleich zu der natürlichen Lagevariation der Prostata durch unterschiedlich starke Rektumfüllung, die nach Crook et al. bis zu 1,7 cm betragen kann, ist eine maximale Verschiebung von weniger als 0,3 cm durch den Schallkopfdruck vernachlässigbar. Um das Potential des Systems voll zu nutzen, müssen eine korrekte Handhabung und Patientenvorbereitung gewährleistet sein.

Reduced rectal toxicity with ultrasound-based image guided radiotherapy using BAT™ (B-mode acquisition and targeting system) for prostate cancer

PurposeTo evaluate the effect of image guided radiotherapy with stereotactic ultrasound BAT (B-mode acquisition and targeting system) on rectal toxicity in conformal radiotherapy of prostate cancer.Patients and Methods42 sequential patients with prostate cancer undergoing radiotherapy before and after the introduction of BAT were included. Planning computed tomography (CT) was performed with empty rectum and moderately filled bladder. The planning target volume (PTV) included the prostate and seminal vesicles with a safety margin of 1.5 cm in anterior and lateral direction. In posterior direction the anterior 1/3 of the rectum circumference were included. Total dose was 66 Gy and a boost of 4 Gy excluding the seminal vesicles.22 patients (BAT group) were treated with daily stereotactic ultrasound positioning, for the other 20 patients (NoBAT group) an EPID (electronic portal imaging device) was performed once a week. Acute and late genito-urinary (GU) and rectal toxicity and PSA values were evaluated after 1.5, 3, 6, 9 and 12 months. The total median follow up of toxicity was 3 years in the BAT group and 4 years in the NoBAT group.ResultsIn the NoBAT group significant more rectal toxicity occurred, while in GU toxicity no difference was seen. Two patients in the NoBAT group showed late rectal toxicity grade 3, no toxicity > grade 2 occurred in the BAT group. There was no significant difference in PSA reduction between the groups.ConclusionWithout BAT significant more acute and a trend to more late rectal toxicity was found. With regard to dose escalation this aspect is currently evaluated with a larger number of patients using intensity-modulated radiotherapy (IMRT).ZusammenfassungHintergrundZiel dieser Auswertung war es, den Effekt der bildgebungsgestützen Strahlentherapie mittels stereotaktischem Ultraschall-BAT (B-mode Acqusition and Targeting-System) auf die Akut- und Spättoxizität am Rektum sowie auf den Verlauf der PSA-Werte zu ermitteln.Patienten und Methodik42 Patienten mit Prostatakarzinom wurden in die Auswertung eingeschlossen (Tabelle 1). Die Planung erfolgte standardisiert mit entleertem Rektum und moderat gefüllter Blase. Es wurde ein Planungszielvolumen (PTV) unter Einschluss der Prostata und Samenblasen mit einem Sicherheitsabstand lateral und anterior von 1,5 cm definiert. Posterior wurde maximal das vordere Rektumdrittel eingeschlossen. Die Gesamtdosis betrug 66 Gy mit einem Boost unter Ausschluss der Samenblasen mit nochmals 4 Gy.Bei 22 Patienten erfolgte die tägliche Lagerungskontrolle mit stereotaktischem Ultraschall (BAT-Gruppe), bei den restlichen 20 (NoBAT-Gruppe) wurde einmal wöchentlich eine Verifikationsaufnahme (EPID) zur Lagerungskontrolle durchgeführt. Die Akuttoxizität und Spättoxizität an der Blase und am Rektum sowie der Verlauf der PSA-Werte nach 1,5, 3, 6, 9 und 12 Monaten wurden ermittelt. Der Beobachtungszeitraum der Patienten ohne BAT war 3–4 Jahre und mit BAT 2–3 Jahre.ErgebnisseIn der NoBAT-Gruppe trat signifikant häufiger eine höhergradige Rektumtoxizität auf (Abbildungen 1 und 2), während sich bei der Blasentoxizität kein wesentlicher Unterschied in beiden Gruppen zeigte. Zwei Patienten aus der NoBAT-Gruppe hatten als Spättoxizität eine persistierende rektale Blutung. In der BAT-Gruppe fand sich keine Spättoxizität > Grad 2. Der Verlauf der PSA-Werte zeigte keinen relevanten Unterschied (Abbildung 3).SchlussfolgerungOhne BAT trat signifikant mehr Akuttoxizität und tendenziell mehr Spättoxizität am Rektum auf. Dieser Aspekt wird insbesondere im Hinblick auf eine Dosiseskalation an einer größeren Patientengruppe mit intensitätsmodulierter Strahlentherapie (IMRT) evaluiert.

Accuracy of Ultrasound-Based (BAT) Prostate-Repositioning: A Three-Dimensional On-Line Fiducial-Based Assessment With Cone-Beam Computed Tomography

PURPOSEnTo assess the accuracy of ultrasound-based repositioning (BAT) before prostate radiation with fiducial-based three-dimensional matching with cone-beam computed tomography (CBCT).nnnPATIENTS AND METHODSnFifty-four positionings in 8 patients with 125I seeds/intraprostatic calcifications as fiducials were evaluated. Patients were initially positioned according to skin marks and after this according to bony structures based on CBCT. Prostate position correction was then performed with BAT. Residual error after repositioning based on skin marks, bony anatomy, and BAT was estimated by a second CBCT based on user-independent automatic fiducial registration.nnnRESULTSnOverall mean value (MV+/-SD) residual error after BAT based on fiducial registration by CBCT was 0.7+/-1.7 mm in x (group systematic error [M]=0.5 mm; SD of systematic error [Sigma]=0.8 mm; SD of random error [sigma]=1.4 mm), 0.9+/-3.3 mm in y (M=0.5 mm, Sigma=2.2 mm, sigma=2.8 mm), and -1.7+/-3.4 mm in z (M=-1.7 mm, Sigma=2.3 mm, sigma=3.0 mm) directions, whereas residual error relative to positioning based on skin marks was 2.1+/-4.6 mm in x (M=2.6 mm, Sigma=3.3 mm, sigma=3.9 mm), -4.8+/-8.5 mm in y (M=-4.4 mm, Sigma=3.7 mm, sigma=6.7 mm), and -5.2+/-3.6 mm in z (M=-4.8 mm, Sigma=1.7 mm, sigma=3.5 mm) directions and relative to positioning based on bony anatomy was 0+/-1.8 mm in x (M=0.2 mm, Sigma=0.9 mm, sigma=1.1 mm), -3.5+/-6.8 mm in y (M=-3.0 mm, Sigma=1.8 mm, sigma=3.7 mm), and -1.9+/-5.2 mm in z (M=-2.0 mm, Sigma=1.3 mm, sigma=4.0 mm) directions.nnnCONCLUSIONSnBAT improved the daily repositioning accuracy over skin marks or even bony anatomy. The results obtained with BAT are within the precision of extracranial stereotactic procedures and represent values that can be achieved with several users with different education levels. If sonographic visibility is insufficient, CBCT or kV/MV portal imaging with implanted fiducials are recommended.

Deep Inspiration Breath Hold-Based Radiation Therapy: A Clinical Review.

Several recent developments in linear accelerator-based radiation therapy (RT) such as fast multileaf collimators, accelerated intensity modulation paradigms like volumeric modulated arc therapy and flattening filter-free (FFF) high-dose-rate therapy have dramatically shortened the duration of treatment fractions. Deliverable photon dose distributions have approached physical complexity limits as a consequence of precise dose calculation algorithms and online 3-dimensional image guided patient positioning (image guided RT). Simultaneously, beam quality and treatment speed have continuously been improved in particle beam therapy, especially for scanned particle beams. Applying complex treatment plans with steep dose gradients requires strategies to mitigate and compensate for motion effects in general, particularly breathing motion. Intrafractional breathing-related motion results in uncertainties in dose delivery and thus in target coverage. As a consequence, generous margins have been used, which, in turn, increases exposure to organs at risk. Particle therapy, particularly with scanned beams, poses additional problems such as interplay effects and range uncertainties. Among advanced strategies to compensate breathing motion such as beam gating and tracking, deep inspiration breath hold (DIBH) gating is particularly advantageous in several respects, not only for hypofractionated, high single-dose stereotactic body RT of lung, liver, and upper abdominal lesions but also for normofractionated treatment of thoracic tumors such as lung cancer, mediastinal lymphomas, and breast cancer. This review provides an in-depth discussion of the rationale and technical implementation of DIBH gating for hypofractionated and normofractionated RT of intrathoracic and upper abdominal tumors in photon and proton RT.

Multiple breath-hold CBCT for online image guided radiotherapy of lung tumors: Simulation with a dynamic phantom and first patient data

BACKGROUND AND PURPOSEnComputer controlled breath-hold effectively reduces organ motion for image-guided precision radiotherapy of lung tumors. However, the acquisition time of 3D cone-beam-CT (CBCT) exceeds maximum breath-hold times. We have developed an approach enabling online verification using CBCT image acquisition with ABC®-based breath-hold.nnnMETHODSnPatient CBCT images were acquired with ABC®-based repeat breath-hold. The clinical situation was also simulated with a Motion Phantom. Reconstruction of patient and phantom images with selection of free-breathing and breath-hold projections only was performed.nnnRESULTSnCBCT-imaging in repeat breath-hold resulted in a precisely spherical appearance of a tumor-mimicking structure in the phantom. A faint ghost structure (free-breathing phases) can be clearly discriminated. Mean percentage of patient breath-hold time was 66%. Reconstruction based on free-breathing-only shows blurring of both tumor and diaphragm, reconstruction based on breath-hold projections only resulted in sharp contours of the same structures. From the phantom experiments, a maximal repositioning error of 1mm in each direction can be estimated.nnnDISCUSSION AND CONCLUSIONnCBCT during repetitive breath hold provides reliable soft-tissue-based positioning. Fast 3D-imaging during one breath-hold is currently under development and has the potential to accelerate clinical linac-based volume imaging.

Intrafraction motion of the prostate during an IMRT session: a fiducial-based 3D measurement with Cone-beam CT.

BackgroundImage-guidance systems allow accurate interfractional repositioning of IMRT treatments, however, these may require up to 15 minutes. Therefore intrafraction motion might have an impact on treatment precision. 3D geometric data regarding intrafraction prostate motion are rare; we therefore assessed its magnitude with pre- and post-treatment fiducial-based imaging with cone-beam-CT (CBCT).Methods39 IMRT fractions in 5 prostate cancer patients after 125I-seed implantation were evaluated. Patient position was corrected based on the 125I-seeds after pre-treatment CBCT. Immediately after treatment delivery, a second CBCT was performed. Differences in bone- and fiducial position were measured by seed-based grey-value matching.ResultsFraction time was 13.6 ± 1.6 minutes. Median overall displacement vector length of 125I-seeds was 3 mm (M = 3 mm, Σ = 0.9 mm, σ = 1.7 mm; M: group systematic error, Σ: SD of systematic error, σ: SD of random error). Median displacement vector of bony structures was 1.84 mm (M = 2.9 mm, Σ = 1 mm, σ = 3.2 mm). Median displacement vector length of the prostate relative to bony structures was 1.9 mm (M = 3 mm, Σ = 1.3 mm, σ = 2.6 mm).Conclusiona) Overall displacement vector length during an IMRT session is < 3 mm.b) Positioning devices reducing intrafraction bony displacements can further reduce overall intrafraction motion.c) Intrafraction prostate motion relative to bony structures is < 2 mm and may be further reduced by institutional protocols and reduction of IMRT duration.

Intensity-Modulated Radiation Therapy (IMRT)with Different Combinations ofTreatment-Planning Systems and Linacs

Purpose:Purpose: To compare different combinations of intensity-modulated radiation therapy (IMRT) system components with regard tonquality assurance (QA), especially robustness against malfunctions and dosimetry.Material and Methods:Three different treatment-planning systems (TPS), two types of linacs and three multileaf collimatorn(MLC) types were compared: commissioning procedures were performed for the combination of the TPS Corvus® 5.0 (Nomos) andnKonRad® v2.1.3 (Siemens OCS) with the linacs KD2® (Siemens) and Synergy® (Elekta). For PrecisePLAN® 2.03 (Elekta) measurementsnwere performed for Elekta Synergy only. As record and verify (R&V) system Multi-Access v7® (IMPAC) was used. The use ofnthe serial tomotherapy system Peacock® (Nomos) was investigated in combination with the Siemens KD2 linac.Results:In the comparison of calculated to measured dose, problems were encountered for the combination of KonRad andnElekta MLC as well as for the Peacock system. Multi-Access failed to assign the collimator angle correctly for plans with multiplencollimator angles per beam. Communication problems of Multi-Access with both linacs were observed, resulting in incorrect recordingnof the treatment. All reported issues were addressed by the manufacturers.Conclusion:For the commissioning of IMRT systems, the whole chain from the TPS to the linac has to be investigated. Componentsnthat passed the commissioning in another clinical environment can have severe malfunctions when used in a new environment.nTherefore, not only single components but the whole chain from planning to delivery has to be evaluated in commissioningnand checked regularly for QA.Ziel:Ziel: Vergleich verschiedener Kombinationen von IMRT-Systemkomponenten (intensitätsmodulierte Strahlentherapie) hinsichtlichnQualitätssicherung (QA), insbesondere Dosimetrie und Anfälligkeit für Fehlfunktion.Material und Methodik:Es wurden die Kombinationen der Planungssysteme Corvus® 5.0 (Nomos) und KonRad® v2.1.3 (SiemensnOCS) mit den Linacs KD2® (Siemens) und Synergy® (Elekta) sowie des TPS PrecisePLAN® 2.03 (Elekta) mit dem Synergy-Linacn(Elekta) anhand von Standardmethoden der IMRT-QA verglichen. Als R&V-System („record and verify“) wurde Multi-Access v7®n(IMPAC) verwendet. Zusätzlich wurde das Tomotherapiesystem Peacock® (Nomos) für den Einsatz am KD2-Linac (Siemens) überprüft.Ergebnisse:Beim Vergleich von berechneter zu gemessener Dosis zeigte KonRad Probleme in Kombination mit dem Elekta MLCn(Multileaf-Kollimator). Pläne mit mehreren Kollimatorwinkeln pro Feld wurden von Multi-Access mit nur einem Kollimatorwinkelnimportiert. Kommunikationsprobleme zwischen dem R&V-System und den beiden Linacs führten zu einer fehlerhaften Protokollierungnder Bestrahlung. Alle Probleme wurden sofort an die Hersteller gemeldet.Schlussfolgerung:Komponenten, die sich bereits in einer anderen Umgebung bewährt haben, können schwere Mängel aufweisen,nwenn sie in einer neuen Kombination verwendet werden. Daher sollten nicht nur einzelne Komponenten, sondern immer diengesamte Bestrahlungskette kommissioniert und regelmäßig überprüft werden.

Intensity-modulated radiation therapy (IMRT) with different combinations of treatment-planning systems and linacs: issues and how to detect them.

Purpose:Purpose: To compare different combinations of intensity-modulated radiation therapy (IMRT) system components with regard tonquality assurance (QA), especially robustness against malfunctions and dosimetry.Material and Methods:Three different treatment-planning systems (TPS), two types of linacs and three multileaf collimatorn(MLC) types were compared: commissioning procedures were performed for the combination of the TPS Corvus® 5.0 (Nomos) andnKonRad® v2.1.3 (Siemens OCS) with the linacs KD2® (Siemens) and Synergy® (Elekta). For PrecisePLAN® 2.03 (Elekta) measurementsnwere performed for Elekta Synergy only. As record and verify (R&V) system Multi-Access v7® (IMPAC) was used. The use ofnthe serial tomotherapy system Peacock® (Nomos) was investigated in combination with the Siemens KD2 linac.Results:In the comparison of calculated to measured dose, problems were encountered for the combination of KonRad andnElekta MLC as well as for the Peacock system. Multi-Access failed to assign the collimator angle correctly for plans with multiplencollimator angles per beam. Communication problems of Multi-Access with both linacs were observed, resulting in incorrect recordingnof the treatment. All reported issues were addressed by the manufacturers.Conclusion:For the commissioning of IMRT systems, the whole chain from the TPS to the linac has to be investigated. Componentsnthat passed the commissioning in another clinical environment can have severe malfunctions when used in a new environment.nTherefore, not only single components but the whole chain from planning to delivery has to be evaluated in commissioningnand checked regularly for QA.Ziel:Ziel: Vergleich verschiedener Kombinationen von IMRT-Systemkomponenten (intensitätsmodulierte Strahlentherapie) hinsichtlichnQualitätssicherung (QA), insbesondere Dosimetrie und Anfälligkeit für Fehlfunktion.Material und Methodik:Es wurden die Kombinationen der Planungssysteme Corvus® 5.0 (Nomos) und KonRad® v2.1.3 (SiemensnOCS) mit den Linacs KD2® (Siemens) und Synergy® (Elekta) sowie des TPS PrecisePLAN® 2.03 (Elekta) mit dem Synergy-Linacn(Elekta) anhand von Standardmethoden der IMRT-QA verglichen. Als R&V-System („record and verify“) wurde Multi-Access v7®n(IMPAC) verwendet. Zusätzlich wurde das Tomotherapiesystem Peacock® (Nomos) für den Einsatz am KD2-Linac (Siemens) überprüft.Ergebnisse:Beim Vergleich von berechneter zu gemessener Dosis zeigte KonRad Probleme in Kombination mit dem Elekta MLCn(Multileaf-Kollimator). Pläne mit mehreren Kollimatorwinkeln pro Feld wurden von Multi-Access mit nur einem Kollimatorwinkelnimportiert. Kommunikationsprobleme zwischen dem R&V-System und den beiden Linacs führten zu einer fehlerhaften Protokollierungnder Bestrahlung. Alle Probleme wurden sofort an die Hersteller gemeldet.Schlussfolgerung:Komponenten, die sich bereits in einer anderen Umgebung bewährt haben, können schwere Mängel aufweisen,nwenn sie in einer neuen Kombination verwendet werden. Daher sollten nicht nur einzelne Komponenten, sondern immer diengesamte Bestrahlungskette kommissioniert und regelmäßig überprüft werden.

Accuracy of ultrasound-based image guidance for daily positioning of the upper abdomen: an online comparison with cone beam CT.

PURPOSEnImage-guided intensity-modulated radiotherapy can improve protection of organs at risk when large abdominal target volumes are irradiated. We estimated the daily positioning accuracy of ultrasound-based image guidance for abdominal target volumes by a direct comparison of daily imaging obtained with cone beam computed tomography (CBCT).nnnMETHODS AND MATERIALSnDaily positioning (n = 83 positionings) of 15 patients was completed by using ultrasound guidance after an initial CBCT was obtained. Residual error after ultrasound was estimated by comparison with a second CBCT. Ultrasound image quality was visually rated using a scale of 1 to 4.nnnRESULTSnOf 15 patients, 7 patients had good sonographic imaging quality, 5 patients had satisfactory sonographic quality, and 3 patients were excluded because of unsatisfactory sonographic quality. When image quality was good, residual errors after ultrasound were -0.1 +/- 3.11 mm in the x direction (left-right; group systematic error M = -0.09 mm; standard deviation [SD] of systematic error, Sigma = 1.37 mm; SD of the random error, sigma = 2.99 mm), 0.93 +/- 4.31 mm in the y direction (superior-inferior, M = 1.12 mm; Sigma = 2.96 mm; sigma = 3.39 mm), and 0.71 +/- 3.15 mm in the z direction (anteroposterior; M = 1.01 mm; Sigma = 2.46 mm; sigma = 2.24 mm). For patients with satisfactory image quality, residual error after ultrasound was -0.6 +/- 5.26 mm in the x (M = 0.07 mm; Sigma = 5.67 mm; sigma = 4.86 mm), 1.76 +/- 4.92 mm in the y (M = 3.54 mm; Sigma = 4.1 mm; sigma = 5.29 mm), and 1.19 +/- 4.75 mm in the z (M = 0.82 mm; Sigma = 2.86 mm; sigma = 3.05 mm) directions.nnnCONCLUSIONSnIn patients from whom good sonographic image quality could be obtained, ultrasound improved daily positioning accuracy. In the case of satisfactory image quality, ultrasound guidance improved accuracy compared to that of skin marks only minimally. If sonographic image quality was unsatisfactory, daily CBCT scanning improved treatment accuracy distinctly over that of ultrasound. Use of daily ultrasound or CBCT imaging can help to reduce PTV margins and protect organs at risk compared to the use of skin mark-based positioning.

Combined Adjuvant Radiochemotherapy With IMRT/XELOX Improves Outcome With Low Renal Toxicity in Gastric Cancer

OBJECTIVESnAdjuvant radiochemotherapy improves survival of patients with advanced gastric cancer. We assessed in two sequential cohorts whether improved radiotherapy technique (IMRT) together with intensified chemotherapy improves outcome vs. conventional three-dimensional conformal radiotherapy (3D-CRT) and standard chemotherapy in these patients while maintaining or reducing renal toxicity.nnnMATERIALS AND METHODSnSixty consecutive patients treated for gastric cancer either with 3D-CRT (n = 27) and IMRT (n = 33) were evaluated. More than 70% had undergone D2 resection. Although there was a slight imbalance in R0 status between cohorts, N+ status was balanced. Chemotherapy consisted predominantly of 5-fluorouracil/folinic acid (n = 36) in the earlier cohort and mostly of oxaliplatin/capecitabine (XELOX, n = 24) in the later cohort. Primary end points were overall survival (OS), disease-free survival (DFS), and renal toxicity based on creatinine levels.nnnRESULTSnMedian follow-up (FU) of all patients in the 3D-CRT group was 18 months and in the IMRT group 22 months (median FU of surviving patients 67 months in the 3D-CRT group and 25 months in the IMRT group). Overall median survival (and DFS) were 18 (13) months in the 3D-CRT group and both not reached in the IMRT group (p = 0.0492 and 0.0216). Actuarial 2-year survival was 37% and 67% in the 3D-CRT and IMRT groups, respectively. No late renal toxicity >Grade 2 (LENT-SOMA scale) was observed in either cohort.nnnCONCLUSIONnWhen comparing sequentially treated patient cohorts with similar characteristics, OS and DFS improved with the use of IMRT and intensified chemotherapy without signs of increased renal toxicity.