J. Penninkhof

Surgical clips for position verification and correction of non-rigid breast tissue in simultaneously integrated boost (SIB) treatments

BACKGROUND AND PURPOSEnThe aim of this study is to investigate whether surgical clips in the lumpectomy cavity are representative for position verification of both the tumour bed and the whole breast in simultaneously integrated boost (SIB) treatments.nnnMATERIALS AND METHODSnFor a group of 30 patients treated with a SIB technique, kV and MV planar images were acquired throughout the course of the fractionated treatment. The 3D set-up error for the tumour bed was derived by matching the surgical clips (3-8 per patient) in two almost orthogonal planar kV images. By projecting the 3D set-up error derived from the planar kV images to the (u, v)-plane of the tangential beams, the correlation with the 2D set-up error for the whole breast, derived from the MV EPID images, was determined. The stability of relative clip positions during the fractionated treatment was investigated. In addition, for a subgroup of 15 patients, the impact of breathing was determined from fluoroscopic movies acquired at the linac.nnnRESULTSnThe clip configurations were stable over the course of radiotherapy, showing an inter-fraction variation (1 SD) of 0.5mm on average. Between the start and the end of the treatment, the mean distance between the clips and their center of mass was reduced by 0.9 mm. A decrease larger than 2mm was observed in eight patients (17 clips). The top-top excursion of the clips due to breathing was generally less than 2.5mm in all directions. The population averages of the difference (+/-1 SD) between kV and MV matches in the (u, v)-plane were 0.2+/-1.8mm and 0.9+/-1.5mm, respectively. In 30% of the patients, time trends larger than 3mm were present over the course of the treatment in either or in both kV and MV match results. Application of the NAL protocol based on the clips reduced the population mean systematic error to less than 2mm in all directions, both for the tumour bed and the whole breast. Due to the observed time trends, these systematic errors can be further reduced to about 1mm by using an eNAL protocol instead.nnnCONCLUSIONSnThe relative positions of implanted surgical clips in the lumpectomy cavity after breast-conserving surgery remain stable during the course of radiotherapy treatment. Application of a NAL or eNAL set-up correction protocol based on surgical clips allows for adequate treatment of both the tumour bed and the whole breast with tight CTV-PTV margins.

Practical Use of the Extended No Action Level (eNAL) Correction Protocol for Breast Cancer Patients With Implanted Surgical Clips

PURPOSEnTo describe the practical use of the extended No Action Level (eNAL) setup correction protocol for breast cancer patients with surgical clips and evaluate its impact on the setup accuracy of both tumor bed and whole breast during simultaneously integrated boost treatments.nnnMETHODS AND MATERIALSnFor 80 patients, two orthogonal planar kilovoltage images and one megavoltage image (for the mediolateral beam) were acquired per fraction throughout the radiotherapy course. For setup correction, the eNAL protocol was applied, based on registration of surgical clips in the lumpectomy cavity. Differences with respect to application of a No Action Level (NAL) protocol or no protocol were quantified for tumor bed and whole breast. The correlation between clip migration during the fractionated treatment and either the method of surgery or the time elapsed from last surgery was investigated.nnnRESULTSnThe distance of the clips to their center of mass (COM), averaged over all clips and patients, was reduced by 0.9 ± 1.2 mm (mean ± 1 SD). Clip migration was similar between the group of patients starting treatment within 100 days after surgery (median, 53 days) and the group starting afterward (median, 163 days) (p = 0.20). Clip migration after conventional breast surgery (closing the breast superficially) or after lumpectomy with partial breast reconstructive techniques (sutured cavity). was not significantly different either (p = 0.22). Application of eNAL on clips resulted in residual systematic errors for the clips COM of less than 1 mm in each direction, whereas the setup of the breast was within about 2 mm of accuracy.nnnCONCLUSIONSnSurgical clips can be safely used for high-accuracy position verification and correction. Given compensation for time trends in the clips COM throughout the treatment course, eNAL resulted in better setup accuracies for both tumor bed and whole breast than NAL.

Automated volumetric modulated arc therapy planning for whole pelvic prostate radiotherapy

BackgroundFor several tumor entities, automated treatment planning has improved plan quality and planning efficiency, and may enable adaptive treatment approaches. Whole-pelvic prostate radiotherapy (WPRT) involves large concave target volumes, which present axa0challenge for volumetric arc therapy (VMAT) optimization. This study evaluates automated VMAT planning for WPRT-VMAT and compares the results with manual expert planning.MethodsAxa0system for fully automated multi-criterial plan generation was configured for each step of sequential-boost WPRT-VMAT, with final “autoVMAT” plans being automatically calculated by the Monaco treatment planning system (TPS; Elekta AB, Stockholm, Sweden). Configuration was based on manually generated VMAT plans (manualVMAT) of 5xa0test patients, the planning protocol, and discussions with the treating physician on wishes for plan improvements. AutoVMAT plans were then generated for another 30xa0evaluation patients and compared to manualVMAT plans. For all 35xa0patients, manualVMAT plans were optimized by expert planners using the Monaco TPS.ResultsAutoVMAT plans exhibited strongly improved organ sparing and higher conformity compared to manualVMAT. On average, mean doses (Dmean) of bladder and rectum were reduced by 10.7 and 4.5u2009Gy, respectively, by autoVMAT. Prostate target coverage (V95%) was slightly higher (+0.6%) with manualVMAT. In axa0blinded scoring session, the radiation oncologist preferred autoVMAT plans to manualVMAT plans for 27/30xa0patients. All treatment plans were considered clinically acceptable. The workload per patient was reduced by >xa070xa0min.ConclusionAutomated VMAT planning for complex WPRT dose distributions is feasible and creates treatment plans that are generally dosimetrically superior to manually optimized plans.ZusammenfassungHintergrundAutomatisierte Bestrahlungsplanung zeigte bei einigen Tumorentitäten Vorteile durch verbesserte Planqualität und höhere Planungseffizienz, was die Einführung adaptiver Bestrahlungstechniken erleichtern könnte. Die Ganzbecken-Prostatabestrahlung (WPRT) beinhaltet große konkave Zielvolumina und stellt eine Herausforderung für die Optimierung der volumenmodulierten Arc-Therapie (VMAT) dar. Die Studie evaluiert die automatisierte VMAT-Planung für WPRT und vergleicht die Ergebnisse mit der manuellen Planung.MethodenEin System für die vollautomatisierte multikriterielle Planung wurde für die WPRT mit sequenziellem Boost konfiguriert, wobei die finalen AutoVMAT-Pläne im Monaco-Planungssystem (Elekta AB, Stockholm, Schweden) berechnet wurden. Die Konfiguration basierte auf manuell erstellten VMAT-Plänen (ManualVMAT) von 5xa0Testpatienten, dem klinischen Planungsprotokoll und Diskussionen mit dem behandelten Arzt zu Planverbesserungen. AutoVMAT-Pläne wurden für weitere 30xa0Evaluierungspatienten erstellt und mit ManualVMAT-Plänen verglichen. Die ManualVMAT-Pläne wurden für alle 35xa0Patienten von erfahrenen Planern in Monaco optimiert.ErgebnisseAutoVMAT-Pläne wiesen stark verbesserte Organschonung und höhere Konformität im Vergleich zu ManualVMAT-Plänen auf. Die mittlere Dosis (Dmean) von Harnblase und Rektum wurden im Durchschnitt um 10,7 und 4,5u2009Gy mit AutoVMAT reduziert. Die Zielgebietsabdeckung der Prostata (V95%) war für ManualVMAT etwas höher (+0,6u2009%). In einer Blindbewertung bevorzugte der behandelnde Radioonkologe den AutoVMAT-Plan gegenüber dem ManualVMAT-Plan bei 27/30 Patienten. Alle Bestrahlungspläne wurden als klinisch akzeptabel bewertet. Der manuelle Arbeitsaufwand pro Patient reduzierte sich um >xa070xa0min.SchlussfolgerungDie automatisierte VMAT-Planung ist für komplexe Dosisverteilungen bei WPRT durchführbar und generiert im Allgemeinen Bestrahlungspläne, die den manuell optimierten Plänen dosimetrisch überlegen sind.

Fully automated, multi-criterial planning for Volumetric Modulated Arc Therapy – An international multi-center validation for prostate cancer

BACKGROUND AND PURPOSEnReported 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.nnnMATERIAL AND METHODSnEach 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.nnnRESULTSnWith equivalent Planning Target Volume (PTV) V95%, D2%, D98%, and dose homogeneity autoVMAT was overall superior for rectum with median differences of 3.4u202fGy (pu202f<u202f0.001) in Dmean, 4.0% (pu202f<u202f0.001) in V60Gy, and 1.5% (pu202f=u202f0.001) in V75Gy, and for bladder Dmean (0.9u202fGy, pu202f<u202f0.001). Also the clinicians plan comparisons pointed at an overall preference for autoVMAT. Advantages of autoVMAT were highly treatment center- and patient-specific with overall ranges for differences in rectum Dmean and V60Gy of [-4,12] Gy and [-2,15]%, respectively.nnnCONCLUSIONnObserved advantages of autoplanning were clinically relevant and larger than reported in the literature. The latter is likely related to the multi-criterial nature of the applied autoplanning algorithm, with for each center a dedicated configuration that aims at plan improvements relative to its (clinical) training plans. Large variations among patients in differences between manVMAT and autoVMAT point at inconsistencies in manual planning.

Individualized Selection of Beam Angles and Treatment Isocenter in Tangential Breast Intensity Modulated Radiation Therapy

PURPOSE AND OBJECTIVEnPropose a novel method for individualized selection of beam angles and treatment isocenter in tangential breast intensity modulated radiation therapy (IMRT).nnnMETHODS AND MATERIALSnFor each patient, beam and isocenter selection starts with the fully automatic generation of a large database of IMRT plans (up to 847 in this study); each of these plans belongs to a unique combination of isocenter position, lateral beam angle, and medial beam angle. The imposed hard planning constraint on patient maximum dose may result in plans with unacceptable target dose delivery. Such plans are excluded from further analyses. Owing to differences in beam setup, database plans differ in mean doses to organs at risk (OARs). These mean doses are used to construct 2-dimensional graphs, showing relationships between: (1) contralateral breast dose and ipsilateral lung dose; and (2) contralateral breast dose and heart dose (analyzed only for left-sided). The graphs can be used for selection of the isocenter and beam angles with the optimal, patient-specific tradeoffs between the mean OAR doses. For 30 previously treated patients (15 left-sided and 15 right-sided tumors), graphs were generated considering only the clinically applied isocenter with 121 tangential beam angle pairs. For 20 of the 30 patients, 6 alternative isocenters were also investigated.nnnRESULTSnComputation time for automatic generation of 121 IMRT plans took on average 30xa0minutes. The generated graphs demonstrated large variations in tradeoffs between conflicting OAR objectives, depending on beam angles and patient anatomy. For patients with isocenter optimization, 847 IMRT plans were considered. Adding isocenter position optimization next to beam angle optimization had a small impact on the final plan quality.nnnCONCLUSIONnA method is proposed for individualized selection of beam angles in tangential breast IMRT. This may be especially important for patients with cardiac risk factors or an enhanced risk for the development of contralateral breast cancer.

SU-E-J-73: Extension of a Clinical OIS/EMR/R&V System to Deliver Safe and Efficient Adaptive Plan-Of-The-Day Treatments Using a Fully Customizable Plan-Library-Based Workflow

Purpose: To extend a clinical Record and Verify (R&V) system to enable a safe and fast workflow for Plan-of-the-Day (PotD) adaptive treatments based on patient-specific plan libraries. Methods: Plan libraries for PotD adaptive treatments contain for each patient several pre-treatment generated treatment plans. They may be generated for various patient anatomies or CTV-PTV margins. For each fraction, a Cone Beam CT scan is acquired to support the selection of the plan that best fits the patient’s anatomy-of-the-day. To date, there are no commercial R&V systems that support PotD delivery strategies. Consequently, the clinical workflow requires many manual interventions. Moreover, multiple scheduled plans have a high risk of excessive dose delivery. In this work we extended a commercial R&V system (MOSAIQ) to support PotD workflows using IQ-scripting. The PotD workflow was designed after extensive risk analysis of the manual procedure, and all identified risks were incorporated as logical checks. Results: All manual PotD activities were automated. The workflow first identifies if the patient is scheduled for PotD, then performs safety checks, and continues to treatment plan selection only if no issues were found. The user selects the plan to deliver from a list of candidate plans. After plan selection, the workflowmorexa0» makes the treatment fields of the selected plan available for delivery by adding them to the treatment calendar. Finally, control is returned to the R&V system to commence treatment. Additional logic was added to incorporate off-line changes such as updating the plan library. After extensive testing including treatment fraction interrupts and plan-library updates during the treatment course, the workflow is running successfully in a clinical pilot, in which 35 patients have been treated since October 2014. Conclusion: We have extended a commercial R&V system for improved safety and efficiency in library-based adaptive strategies enabling a wide-spread implementation of those strategies. This work was in part funded by a research grant of Elekta AB, Stockholm, Sweden.«xa0less

OC-0329: Extension of a commercial R&V system to improve safety and efficiency of library-based plan-of-the-day strategies

Also, national societies of medical physicists and RTTs have been addressed in order to gather information regarding legal requirements in the different countries. Through the dissemination of the results from these surveys, and an associated literature review, the goal of this task group is to make radiotherapy professionals familiar with industrial quality management tools, and how these methods can be applied in our field. It is our hope that this may help optimising time and resources spent on quality assurance procedures within radiotherapy in the future.

SU‐GG‐T‐02: Clinical Application of the ENAL Set‐Up Correction Protocol to Compensate for Time Trends in Breast Cancer Treatments

Purpose: Clinical evaluation of the extended NAL (eNAL) set‐up protocol (deBoer2007) for breast cancer patients treated with an integrated boost technique. Method and Materials: For 80 breast cancer patients, two orthogonal planar kilovoltage images and one megavoltage image (for the medio‐lateral beam) were acquired per fraction throughout the treatment course (14 fractions on average). Based on registration of surgical clips in the lumpectomy cavity (4.3 on average) set‐up corrections were derived after the first three fractions and updated once a week thereafter using eNAL. The stability of the clips during the fractionated treatment was derived. Using a t‐test the correlation between clip migration and either the method of surgery or the time elapsed from last surgery was quantified. The impact of the eNAL protocol on the set‐up accuracy for both the tumor bed and the whole breast was evaluated. Results: During the fractionated treatment the mean distance between the clips and their center of mass (COM) reduced by 0.9 ± 1.2 mm (1 SD). The clip migration was not statistically different between patients treated within 100 days after surgery or afterwards (p=0.20). Compared to conventional breast surgery (closing the lumpectomy cavity superficially), clip migration after oncoplastic surgery (suturing the lumpectomy cavity) was slightly smaller, but not significantly different (p=0.13). Throughout the treatment course timetrends in the COM position of the clips >3mm were observed for 61% of the patients. Application of the eNAL protocol on clips resulted in residual systematic errors for the tumor bed of <1 mm in each direction, while the whole breast was treated within about 2 mm accuracy. Conclusion: Surgical clips can safely be used for position verification and correction. By compensating for time trends, the eNAL protocol resulted in better set‐up accuracies for both the tumor bed and the whole breast than the NAL protocol.