Stereotactic radiosurgery (SRS) is the accurate, conformal delivery of high‐dose radiation to well‐defined targets while minimizing normal structure doses via steep dose gradients. While inverse treatment planning (ITP) with computerized optimization algorithms are routine, many aspects of the planning process remain user‐dependent. We performed an international, multi‐institutional benchmark trial to study planning variability and to analyze preferable ITP practice for spinal robotic radiosurgery. 10 SRS treatment plans were generated for a complex‐shaped spinal metastasis with 21 Gy in 3 fractions and tight constraints for spinal cord (normalV14Gy<2 cc, normalV18Gy<0.1 cc) and target (coverage >95%). The resulting plans were rated on a scale from 1 to 4 (excellent‐poor) in five categories (constraint compliance, optimization goals, low‐dose regions, ITP complexity, and clinical acceptability) by a blinded review panel. Additionally, the plans were mathematically rated based on plan indices (critical structure and target doses, conformity, monitor units, normal tissue complication probability, and treatment time) and compared to the human rankings. The treatment plans and the reviewers' rankings varied substantially among the participating centers. The average mean overall rank was 2.4 (1.2‐4.0) and 8/10 plans were rated excellent in at least one category by at least one reviewer. The mathematical rankings agreed with the mean overall human rankings in 9/10 cases pointing toward the possibility for sole mathematical plan quality comparison. The final rankings revealed that a plan with a well‐balanced trade‐off among all planning objectives was preferred for treatment by most participants, reviewers, and the mathematical ranking system. Furthermore, this plan was generated with simple planning techniques. Our multi‐institutional planning study found wide variability in ITP approaches for spinal robotic radiosurgery. The participants', reviewers', and mathematical match on preferable treatment plans and ITP techniques indicate that agreement on treatment planning and plan quality can be reached for spinal robotic radiosurgery.PACS number(s): 87.55.de

Background: Late effects induced by radiotherapy (RT) are of great concern for mediastinal Hodgkin's lymphoma (HL) patients and it is therefore important to reduce normal tissue dose. The aim of this study was to investigate the impact on the normal tissue dose and target coverage, using various combinations of intensity modulated proton therapy (IMPT), volumetric modulated arc therapy (VMAT) and 3-dimensional conformal RT (3D-CRT), planned in both deep inspiration breath hold (DIBH) and free breathing (FB). Material and methods: Eighteen patients were enrolled in this study and planned with involved site RT. Two computed tomography images were acquired for each patient, one during DIBH and one during FB. Six treatment plans were created for each patient; 3D-CRT in FB, 3D-CRT in DIBH, VMAT in FB, VMAT in DIBH, IMPT in FB and IMPT in DIBH. Dosimetric impact on the heart, left anterior descending (LAD) coronary artery, lungs, female breasts, target coverage, and also conformity index and integral dose (ID), was compared between the different treatment techniques. Results: The use of DIBH significantly reduced the lung dose for all three treatment techniques, however, no significant difference in the dose to the female breasts was observed. Regarding the heart and LAD doses, large individual variations were observed. For VMAT, the mean heart and LAD doses were significantly reduced using DIBH, but no significant difference was observed for 3D-CRT and IMPT. Both IMPT and VMAT resulted in improved target coverage and more conform dose distributions compared to 3D-CRT. IMPT generally showed the lowest organs at risk (OAR) doses and significantly reduced the ID compared to both 3D-CRT and VMAT. Conclusions: The majority of patients benefited from treatment in DIBH, however, the impact on the normal tissue dose was highly individual and therefore comparative treatment planning is encouraged. The lowest OAR doses were generally observed for IMPT in combination with DIBH.

High plan quality for complex spinal radiosurgery was achieved among all systems and all participating centers in this planning challenge. This study concludes that simple IMAT techniques can generate significantly better plan quality compared to previous established CKRS benchmarks.

Abstract. Patient-specific IMRT QA is dependent on the dosimetry system and the evaluation procedure. The ICRU report 83 provides recommendations of tolerated deviations between measured and calculated absorbed dose distributions for QA of IMRT treatment plans. The result of doing IMRT patient-specific QA with the Delta 4 dosimetry system and using the ICRU recommendations for evaluation is studied. To be able to investigate the QA procedure the original IMRT treatment plans were modified in the treatment planning system to create calculated dose distributions with dosimetric deviations from the original treatment plans. The modified dose distributions were compared to the dose distributions from the Delta 4 measurements of the original treatment plans and the differences were evaluated with criteria and tolerance levels according to the recommendations from ICRU. The evaluation for all 28 modified dose distributions have gamma passing rates higher than the tolerance level recommended from ICRU and will therefore pass the patient-specific QA. More than half of the evaluations have a gamma passing rate of 100 %. Evaluation of the differences between the modified and the original calculated dose distributions revealed in several cases large unacceptable dose differences in the PTV volumes and the organs at risk, for example an increase in the near-maximum dose D 2 % to the spinal cord of 5.5 Gy. This study indicates that patient-specific QA with the Delta 4 dosimetry system and the ICRU recommendations for evaluation can not be used to distinguish differences between planned and measured dose of dosimetrical relevance.

Die groBe praktische Bedeutung, welche allgemein der kiinstlichen Atmung beim Menschen zuerkannt wird, hat eine intensive Arbeit uber die bisherigen Fragen veranlaBt. Teils hat man in zahlreichen Tierversuchen genaue Studien iiber die Phanomene gemacht, welche das Ertrinken und die Erstickung begleiten, teils hat man eine Menge verschiedener Methoden zur kunstliohen Atmung angegeben. Untersuchungen uber den praktischen Wert dieser 1\1ethoden sind zahlreich ausgefiihrt worden, jedoch herrscht in wichtigen Punkten nooh Unklarheit. Die Frage nach dem Wert der Methoden ist offenbar ziemlich komplizierter Art, und die Antwort wird von einer ganzen Reihe verschiedener Faktoren bestimmt. Von diesen erwahnen wir: Einfachheit und Ausfuhrbarkeit, die Wirkungen auf den Kreislauf, die GroBe der erhaltenen Ventilation, ob die Zunge unter anderem in dem einen oder anderen Falle ein Hindernis ist oder nicht, ob das Entweichen des Wassers aus den Lungen beiordert wird, ob die Methode vielleicht Beschadigungen anrichten kann (z, B. Leberruptur, Rippenfraktur). In mehreren von diesen Punkten stehen nun, wie es scheint, die von verschiedenen Forschern erhaltenen Ergebnisse in schroffem Gegensatze zueinander. Auch uber die Bedeutung der genannten Faktoren gehen die Ansichten auseinander. Dies gilt auch besonders von der Bedeutung und GroBe der Ventilation, welche mit den versohiedenen Methoden erhalten worden ist. Schon im Jahre 1858 150 G. LILJESTRAND, G. WOLLIN UND J. O. l'ILSSON: hebt Silvester hervor (21: 301) 1, daB "it is, of course, of consequence to get as much air into the lungs as possible" (vgl. auch 30, Disk.), Diese Auffassung hat abel' in ihrer allgerneinen Form in den letzten Jahren Widerspruche gefunden. So hebt von Eysselstein (4) hervor, daB eine Uberventilation nicht notwendig sei; del' Ertrinkende befindet sich nach ihm in einem Zustande, ahnlich dem Winterschlafe gewisser Tiere, und hat eiu sehr kleines Sauerstoffbediirfnis, welches befriedigt werden muB. In derselben Richtung iiuBert sich Schafer (31). 'Vie spater naher entwickelt wird, ist Schafer zu dem Resultat gekommen, daB die von ihm eiugefuhrte Methode del' kunstlicheu Atmung den anderen gegeniiber die Vorteile hat, daB sie die eiufachste und gleichzeitig mit Riicksicht auf die Ventilation die beste ist, namlich mit einem Luftwechsel, del' mindestens ebenso groB ist, wie hei del' spontanen Atmung. Infolgedessen sagt Schafer (31): "Die Frage, ob andere und kompliziertere Methoden einen groferen oder geringeren Luftwechsel herbeifuhren als diejenige, welche einen geniigenden Luftwechsel bewirkt und dabei noch durch groBte Leichtigkeit und Einfaehheit sich auszeichnet, ist eine rein akademische." Hiergegen muB erstens bemerkt werden, daB es Angaben gibt, welche darauf hilldeuten, daB die Schiifersche Methode eine ungeniigende Ventilation herbeifiihren soli [Ploman (25)J. Es kommt abel' noch folgeudes hinzu. Wahrend die Ausfiihrung del' kiinstlichen Atmung nach Schafer zweifelsohne einfacher und weniger ermudend ist als nach del' Mehrzahl del' iibrigen gewoh...