Normal tissue complication probabilities (NTCP) for modified reverse hockey stick technique (MRHS)

BackgroundSeveral treatment techniques are used for irradiation of patients with breast cancer after mastectomy. There is no one technique accepted as the “gold standard”. In the Holycross Cancer Centre a novel technique – the modified reverse hockey stick technique – is used.AimEvaluation of the risk of heart and lung injury in patients treated with the MRHS technique. Comparison of the risk for MRHS and tangential techniques.Materials/MethodsThe 3D CT based dose distributions for 25 left-sided and 25 right-sided patients after mastectomy were calculated. For each patient before the NTCP was calculated all physical doses were converted into biological doses according to an α/β model with an α/β value of 3Gy. The NTCP for the lung was for each patient calculated with generalized Lyman model with two parameters: the biological mean dose and the volume above a biological threshold dose of 13Gy (V13). For the heart the NTCP was calculated using the seriality model. The parameters of the models were taken from the literature. For the heart, for each patient the partial volume of the heart receiving more than 30Gy (V30) was also obtained. The correlation between NTCP and V30 for the heart and between the mean physical dose and the mean biological dose for the lungs were determined.ResultsFor all left-sided patients but two for the MRHS technique the NTCP for the heart was smaller than 0.01. For tangential technique, the calculated risk of heart injury was higher. A very high correlation between V30 and NTCP was obtained for both techniques. Larger NTCPs were obtained for both techniques for patients treated on the right side. About two times higher values of NTCP were obtained if calculated with the V13 parameter. Based on the mean dose on the left side NTCP is always smaller than 0.05. For some patients treated on the right side, NTCP exceeded 0.1. NTCP values for patients treated either on the left or the right lungs for both techniques were similar. There was a high correlation between the mean physical and biological doses.ConclusionsFor left sided-patients, the MRHS technique is safe for the heart and is superior to the tangential technique. The risk of lung injury is higher for patients treated on the right side. Regarding the risk of lung injury, there is no difference between the two techniques. There is a very high correlation between NTCP and V30 for the heart and between the mean physical and biological doses for the lungs

Dose gradient based algorithm for beam weights selection in 3D-CRT plans

AbstractAimIn this work we test the usage of dose gradient based algorithm for the selection of beam weights in 3D-CRT plans for different cancer locations. Our algorithm is easy to implement for three fields technique with wedges defined by planner.Background3D-CRT is usually realized with forward planning which is quite time consuming. Several authors published a few methods of beams weights optimization applicable to the 3D-CRT.Materials and methodsOptimization is based on an assumption that the best plan is achieved if dose gradient at ICRU point is equal to zero. Method was tested for 120 patients, treated in our clinic in 2011-2012, with different cancer locations. For each patient, three fields conformal plan (6MV and 15MV X-ray) with the same geometry as proposed by experienced planners was prepared. We compared dose distributions achieved with the proposed method and those prepared by experienced planners. The homogeneity of dose distributions was compared in terms of STD and near minimum and near maximum doses in the PTV.ResultsMean difference of STD obtained by the proposed algorithm and by planners was 0.1%: 0.1% for prostate cancer, 0.3% for lung cancer, −0.1% for esophagus cancer, 0.1% for rectum cancer, −0.1% for gynecology cancer, −0.1% for stomach cancer.ConclusionsApplying the proposed algorithm leads to obtain the similar dose distribution homogeneity in the PTV as these achieved by planners and therefore can serve as a support in creating 3D-CRT plans. It is also simple to use and can significantly speed up the treatment planning process

What new dose distribution statistics may be included in the optimization of dose distribution in radiotherapy for post-mastectomy patients

Introduction. The main aim of this study was to evaluate the doses delivered to heart substructures and calculate normal tissue complication probability (NTCP) for the intensity modulation radiotherpy (IMRT) irradiated group of left-sided post-mastectomy patients. Material and methods. In this retrospective study for 30 randomly chosen breast cancer patients, the mean dose, V2, V4, V10, V20 and D2% in the heart substructures were evaluated. Results. The mean heart dose was 12.3 Gy, the mean left anterior descending artery (LAD) dose was 28.5 Gy. The average value of long-term cardiac mortality was 0.17%, pericarditis 0.0%, left ventricle perfusion defects 24.5% and LAD toxicity 0.2%. In the literature, for the IMRT technique for left-sided mastectomy patients, the mean heart dose ranged from 8.7–14.0 Gy and the V20 10.5–14%. Additional studies are needed to describe the cardiac toxicity. Conclusions. It is necessary to contour cardiac substructures for reliable assessment of the dose distribution, although the mean heart dose is simplification for modern radiotherapy techniques

Effect of beam spoiler on radiation dose in the build-up region for 6-MV X-ray

CelZbadanie wpływu płyty rozpraszającej umieszczonej w polu promieniowania X o energii 6 MeV na rozkład dawki w obszarze narastania.Materiały i metodyPomiary wykonano dla promieniowania X o energii 6 MeV generowanego w akceleratorze Mevatron KD2. Rozkłady dawki w osi centralnej wiązki zmierzono dla pól kwadratowych o boku 5, 10, 15 i 20 cm w odległości SSD=100 cm. Wykonano pomiary dla pól otwartych, modyfikowanych klinami 15o, 30o, 45o i 60o oraz dla pól modyfikowanych płytą umieszczoną w odległości 10, 15 i 20 cm od powierzchni fantomu.Wyniki1.Obecność płyty zwiększa dawkę w obszarze narastania i przybliża maksimum dawki do powierzchni. 2.Wzrost dawki jest tym większy, im płyta znajduje się bliżej absorbenta.WnioskiZastosowanie płyty rozpraszającej znacząco zmienia rozkład dawki w obszarze narastania, co umożliwia zastosowanie promieniowania X o energii 6 MeV w terapii nowotworu piersi oraz w tych wszystkich przypadkach, dla których konieczne jest zastosowanie promieniowania fotonowego o stosunkowo wysokiej energii i równoczesne napromienianie płytko położonych tkanek.PurposeTo determine the effects of a lucite spoiler on the dose distribution in the build-up region for 6-MV X-rays.Methods and MaterialsBuild-up depth-dose measurements were performed for 6-MV X-ray beams generated in a Mevatron KD2 accelerator. Dose distributions were measured with a parallelplate ionisation chamber 5 × 5, 10 × 10, 15 × 15 and 20 × 20-cm fields sizes at 100 cm SSD. Measurements were performed either for open or for 15, 30, 45 and 60 degrees wedged beams. The spoiler was placed at three different spoiler-water phantom distances of 10, 15 and 20 cm.ResultsThe spoiler increased the surface and the build-up dose and shifted the depth of the maximum dose toward the surface. The smaller is the spoiler-phantom distance the larger is the influence of the spoiler on the dose distribution in the build-up region.ConclusionsThe spoiler changed the dose distribution in the build-up region. It allowed using a 6-MV X-ray beam for breast treatment and for all other cases in which the superficial dose should be high enough

Coping with interfraction time trends in tumor setup

Purpose: Interfraction tumor setup variations in radiotherapy are often reduced with image guidance procedures. Clinical target volume (CTV)–planning target volume (PTV) margins are then used to deal with residual errors. We have investigated characterization of setup errors in patient populations with explicit modelling of occurring interfraction time trends. Methods: The core of a “trendline characterization” of observed setup errors in a population is a distribution of trendlines, each obtained by fitting a straight line through a patient's daily setup errors. Random errors are defined as daily deviations from the trendline. Monte Carlo simulations were performed to predict the impact of offline setup correction protocols on residual setup errors in patient populations with time trends. A novel CTV-PTV margin recipe was derived that assumes that systematic underdosing of tumor edges in multiple consecutive fractions, as caused by trend motion, should preferentially be avoided. Similar to the well-known approach by van Herk et al. for conventional error characterization (no explicit modelling of trends), only a predefined percentage of patients (generally 10%) was allowed to have nonrandom (systematic + trend) setup errors outside the margin. Additionally, a method was proposed to avoid erroneous results in Monte Carlo simulations with setup errors, related to decoupling of error sources in characterizations. The investigations were based on a database of daily measured setup errors in 835 prostate cancer patients that were treated with 39 fractions, and on Monte Carlo–generated patient populations with time trends. Results: With conventional characterization of setup errors in patient populations with time trends, predicted standard deviations of residual systematic errors ((∑res)) after application of an offline correction protocol could be underestimated by more than 50%, potentially res

Comparison of image registration performed with MV cone beam CT and CT on rails and Syngo™ Adaptive Targeting software

BackgroundMinimization of geometric errors in treatment delivery is essential in modern conformal and intensity-modulated techniques.AimIn this paper two Siemens systems, MVision megavoltage cone beam CT, and CTVision (CT on rails), are compared.Material and MethodsThe reproducibility and uncertainty of the image registration procedure performed with Adaptive Targeting (AT) software were evaluated. Both systems were evaluated by means of simulating the clinical situation with an anthropomorphic phantom in three anatomical sites: head & neck, thorax and pelvis.ResultsThe results for two methods of image registration, manual and automatic, were evaluated separately. The manual procedure was used by two users, more and less experienced.ConclusionsThe MVision system and CTVision and the Therapist Adaptive software ensure image registration with the uncertainty of about 2.0 mm (2 standard deviations). In the case of the automatic registration method better reproducibility of image registration was obtained for MVision. For CTVision the necessity of manual identification of the machine isocentre made the registration less reproducible. In the case of MVision, the automatic method was more reproducible than the manual one (smaller dispersion of results). In the case of CTVision, similar results were obtained for both registration methods. In the case of manual registration slightly better reproducibility for CT data acquired at 2 mm slice thickness and 2 mm slice separation than for data acquired at 5 mm slice thickness and 5 mm slice separation were obtained. Similar results of manual registration performed by more and less experienced users were obtained

Porównanie metod 3D-CRT i IMRT w napromienianiu chorych na raka piersi po operacji oszczędzającej bez i z objęciem węzłów chłonnych nadobojczykowo-pachowych

Aim of the study. The aim of this study was to compare the IMRT (Intensity Modulated Radiation Therapy) and 3D-CRT (3-Dimensional Conformal Radiation Therapy) techniques as far as the planning target volume (PTV) coverage and normal tissue sparing in concerned.Material and methods. IMRT and 3D-CRT plans for 15 patients with early breast cancer after breast conservation therapy were prepared with the Eclipse treatment planning system. For plan comparison in PTVbreast and in PTVnodes the minimal dose — Dmin, maximal dose — Dmax, standard deviation — SD, and Coverage Index — CovI were evaluated. For organs at risk (both lungs, heart, coronary arteries and healthy breast) during preparation of 3D-CRT and IMRT plans dose volume constrains were established.Results. In the group of patients with left breast cancer only, without involved lymph nodes, lower SD values (mean 0.8%) and higher values of CovI (mean 0.03) were obtained for IMRT technique. In the group of patients requiring supraclaviculary and axillary lymph nodes irradiation, a lower value of SD 1.3% vs 4.4% for left side and 1.4% vs 5.0% for right side were obtained for IMRT. In the IMRT technique a higher value of CovI 0.99, independent of the irradiated side, were obtained as compared to 0.55 for left side and 0.39 for right side in the 3D-CRT. The 3D-CRT technique offers more sparing to organs at risk in comparison with coplanar fields in IMRT. In the group of patients without irradiated lymph nodes, the mean heart volume receiving 20 Gy or more was lower in 3D-CRT — 0.2% compared to 2.6% in IMRT. For coronary arteries Dmax — was 33.7 Gy in IMRT vs 37.5 Gy in 3D-CRT, Dmean in IMRT — was 9.1 Gy vs 3.2 Gy w 3D-CRT. Mean volume of lung on irradiated side receiving dose of 20 Gy was 20% in IMRT and 7.4% in 3D-CRT. Mean value of Dmean in right lung was 14.7 Gy in IMRT vs 4.8 Gy in 3D-CRT. In the group of patients with irradiated breast and lymph nodes on the left side the mean Dmax in coronary arteries is 7 Gy lower and the Dmean is 5 Gy higher in the IMRT technique. The volumes of lung on the irradiated side receiving a dose of 20 Gy were similar in both techniques — 27.3% in IMRT vs 26.3% in 3D-CRT. Dmean for lung on irradiated side was 5 Gy higher in the IMRT. The Dmean doses for right lung and right breast were 5.9 Gy and 4.6 Gy in the IMRT compared to 0.8 Gy and 0.7 Gy in the 3D-CRT.Conclusions. Dose distributions in both techniques for patients with left side breast only were similar. The differences were observed for patients with involved lymph nodes, regardless of the side of involved breast. Conventional breast irradiation 3D-CRT was better for sparing of normal tissue. However, the constraints for the organs at risk for the IMRT were also fulfilled.Cel. Celem opracowania było porównanie rozkładu dawki dla obszarów tarczowych i narządów krytycznych w dwóchtechnikach leczenia: konwencjonalnej trójwymiarowej konformalnej radioterapii 3D-CRT (3 Dimensional ConformalRadiation Therapy) oraz radioterapii z modulowaną intensywnością dawki IMRT (Intensity Modulated Radiation Therapy)u chorych na raka piersi napromienianych na pierś i okolice węzłowe nadobojczykowo-pachowe.Materiał i metody. W pracy przeanalizowano 15 planów radioterapeutycznych przygotowanych dla chorych na wczesnegoraka piersi poddanych leczeniu oszczędzającemu BCT (Breast Conservation Therapy). Dla każdego z piętnastuplanów wykonano w systemie Eclipse testowe plany IMRT w technice dynamicznej (sliding window) i porównano jez planami w technice 3D-CRT, którymi chore były uprzednio napromieniane. Do porównania planów leczenia w obszarzetarczowym PTVpierś i PTVwęzły wykorzystano: dawkę minimalną (Dmin), dawkę maksymalną (Dmax), odchyleniestandardowe dawki (SD), indeks pokrycia jednorodności (Coverage Index — CovI). Dla narządów krytycznych (obapłuca, serce, naczynia wieńcowe oraz zdrowa pierś) przy tworzeniu planów 3D-CRT oraz IMRT ustalono ograniczeniadawek zgodnie z protokołem przyjętym w Centrum Onkologii Warszawa Ursynów.Wyniki. W grupie pacjentek z nowotworem lewej piersi, bez konieczności napromieniania węzłów, w technice IMRTdla obszaru PTVpierś otrzymano niższe wartości odchylenia standardowego (średnio o 0,8%) oraz wyższą dla technikiIMRT wartość CovI (średnio o 0,03). Dla chorych, u których wymagane było napromienienie okolic węzłowych,w technice IMRT dla obszaru PTVwęzły otrzymano niższe odchylenie standardowe: 1,3% vs 4,4% dla strony lewej oraz1,4% vs 5,0% dla strony prawej. W planach IMRT otrzymano również wyższą wartość CovI — 0,99 niezależnie odstrony napromienianej w porównaniu z 0,55 dla strony lewej i 0,39 dla strony prawej w planach 3D-CRT. Technika3D-CRT gwarantuje lepszą ochronę narządów krytycznych w porównaniu do techniki IMRT. W przypadku pacjentekbez napromienianych węzłów chłonnych średnia objętość serca otrzymująca dawkę 20 Gy lub większą jest mniejszaw technice 3D-CRT 0,2% w stosunku do 2,6% w IMRT. Pomimo mniejszej Dmax — 33,7 Gy w IMRT vs 37,5 Gy w 3D-CRTdla naczyń wieńcowych, dawka średnia Dmean była większa w technice IMRT — 9,1 Gy w porównaniu z 3,2 Gy w 3D-CRT.Średnia objętość płuca po stronie napromienianej otrzymująca dawkę 20 Gy wyniosła 20% w technice IMRT i 7,4%w technice 3D-CRT. Średnia wartość Dmean uzyskanych u pojedynczych pacjentów w płucu po stronie napromienianejbyła większa w IMRT (14,7 Gy vs 4,8 Gy w 3D-CRT). W przypadku napromieniania piersi i węzłów nadobojczykowo- pachowych po stronie lewej średnia wartość dawek maksymalnych Dmax w naczyniach wieńcowych jest o około7 Gy mniejsza w technice IMRT. Dawka średnia natomiast jest większa o 5 Gy. Bardzo podobne w obu technikach byłyobjętości płuca po stronie napromienianej (lewej), otrzymujące dawki większe od 20 Gy (27,3% vs 26,3% w 3D-CRT),przy Dmean większej o 5 Gy w technice IMRT. Średnia Dmean dla płuca i piersi po stronie nienapromienianej (prawej)wynosiła odpowiednio 5,9 Gy i 4,6 Gy w IMRT w stosunku do 0,8 Gy i 0,7 Gy w 3D-CRT.Podsumowanie. W planach wykonanych techniką IMRT z polami komplanarnymi otrzymuje się porównywalną (napromienianie piersi bez węzłów) lub znacząco lepszą (dla obszarów węzłowych) w stosunku do techniki 3D-CRT jednorodność w obszarze tarczowym. W konsekwencji wyższe dawki otrzymują narządy krytyczne, aczkolwiek nadal zachowane są dawki tolerancji

Evaluation of the technical status of radiotherapy simulators involved in clinical trials

BackgroundRadiotherapy simulators play an important role in the preparation of radiation treatment. Their mechanical and geometrical parameters have to be identical with those of the treatment machines. Therefore, quality control protocols for the simulators should be comprehensive and the tolerance limits as high as those for treatment machines.AimEvaluation of the technical status of radiotherapy simulators involved in clinical trials.Materials/MethodsIn this paper, results of quality control tests conducted in 12 Polish radiotherapy centres are presented. The tests were carried out within the framework of Polish research project KBN No. 6 P05C 032 20. 12 radiotherapy simulators installed in Polish radiotherapy centres were thoroughly tested. In order to control technical conditions of the simulators, a set of 24 tests was elaborated. The tests were divided into six thematic groups. The detailed range of the parameters controlled and the accepted ranges of tolerance limits are given. The values of tolerance limits are based on data found in the available literature.ResultsThe control of 12 simulators revealed the violation of accepted tolerance limits for 13 out of 24 controlled parameters. The most frequent violations of accepted tolerance limits occurred in the case of geometrical parameters of light simulation and mechanical parameters of the couch, both very important for the accuracy of the simulation process.For 2 simulators almost 30% of controlled parameters were outside the tolerance limits.ConclusionsThe control of radiotherapy simulators undertaken within the framework of the clinical trial revealed that in the majority of cases the simulators were in good technical condition. In 2 cases almost 30% of controlled parameters were outside the tolerance limits. In such cases the manufacturers' service should be called urgently for necessary repairs and regulations. After repeated quality control tests a decision should be taken regarding the accepted range of operations which could be used in clinical practice. A QA and QC system for radiotherapy simulators should be introduced in each radiotherapy centre

Comparison of 3D-CRT and IMRT techniques in radiotherapy for post-prostatectomy patients with a higher risk of nodal involvement

Background. Irradiation of a larger volume of the target may lead to an increase of the doses delivered to the surrounding organs at risk (OAR) for post-prostatectomy patients with a higher risk of nodal involvement. It was anticipated that IMRT significantly improved OAR sparing. The aim of this study was to provide a dosimetric comparison between conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) treatment plans for patients with prostate cancer irradiated to the prostate bed and pelvic lymph-nodal area. Materials and methods. The 3D-CRT and IMRT plans were created for ten patients after prostatectomy. The treatment plans were generated for the prostate bed (PTV1) and the pelvic lymph nodes (PTV2). The sum of PTV1 and PTV2 was irradiated to a mean dose of 46 Gy in 23 fractions, and additionally PTV1 was irradiated to a mean dose of 18 Gy in 9 fractions. Target coverage and the doses delivered to the pelvic bones, the rectum, the bladder, the bowel bag, and the femurs, were compared between techniques. The Wilcoxon signed-rank test was used to compare the dosimetric parameters. Results. The dosimetric quality of 3D-CRT and IMRT plans were comparable for target coverage (the mean value of PTV1 V95%, the mean value of PTV2 V95% all > 99%). The IMRT plans resulted in significant reductions in the pelvic bones V30[%], V40[%], the rectum V40[%], V50[%], V60[%], the bladder V40[%], V50[%], V60[%], the bowel bag V45[cc] and the femurs V40[%]. Conclusions. The analysis presented in this paper demonstrates that the IMRT technique reduces the delivered dose to the OARs. Most interesting was the possibility of reducing the delivered dose to the pelvic bones and the bowel bag. This allowed us to expect a decreased risk of acute hematologic toxicity and acute gastrointestinal toxicity

Comparison of 3D-CRT and IMRT techniques in radiotherapy for post-prostatectomy patients with a higher risk of nodal involvement

Background. Irradiation of a larger volume of the target may lead to an increase of the doses delivered to the surrounding organs at risk (OAR) for post-prostatectomy patients with a higher risk of nodal involvement. It was anticipated that IMRT significantly improved OAR sparing. The aim of this study was to provide a dosimetric comparison between conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) treatment plans for patients with prostate cancer irradiated to the prostate bed and pelvic lymph-nodal area. Materials and methods. The 3D-CRT and IMRT plans were created for ten patients after prostatectomy. The treatment plans were generated for the prostate bed (PTV1) and the pelvic lymph nodes (PTV2). The sum of PTV1 and PTV2 was irradiated to a mean dose of 46 Gy in 23 fractions, and additionally PTV1 was irradiated to a mean dose of 18 Gy in 9 fractions. Target coverage and the doses delivered to the pelvic bones, the rectum, the bladder, the bowel bag, and the femurs, were compared between techniques. The Wilcoxon signed-rank test was used to compare the dosimetric parameters. Results. The dosimetric quality of 3D-CRT and IMRT plans were comparable for target coverage (the mean value of PTV1 V95%, the mean value of PTV2 V95% all > 99%). The IMRT plans resulted in significant reductions in the pelvic bones V30[%], V40[%], the rectum V40[%], V50[%], V60[%], the bladder V40[%], V50[%], V60[%], the bowel bag V45[cc] and the femurs V40[%]. Conclusions. The analysis presented in this paper demonstrates that the IMRT technique reduces the delivered dose to the OARs. Most interesting was the possibility of reducing the delivered dose to the pelvic bones and the bowel bag. This allowed us to expect a decreased risk of acute hematologic toxicity and acute gastrointestinal toxicity