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Color a MDACC alignment frame and b one of the depth measurement rods. The frame uses five tattoo points to align patient anatomy for treatment. The depth rods are marked with a millimeter resolution scale for depth measurements to evaluate patient positioning reproducibility.
Source publication
The planning target volume (PTV) includes the clinical target volume (CTV) to be irradiated and a margin to account for uncertainties in the treatment process. Uncertainties in miniature multileaf collimator (mMLC) leaf positioning, CT scanner spatial localization, CT-MRI image fusion spatial localization, and Gill-Thomas-Cosman (GTC) relocatable h...
Context in source publication
Context 1
... of the GTC frame was determined using a method described by Kooy et al. 5 The measured uncertainty in GTC repositioning is a combination of two quantities: 1 the actual repositioning uncertainty and 2 the uncertainty in the measurement itself. Our institution's in- house alignment frame and depth-measurement rod are shown in Fig. 5. The frame is attached to the GTC frame and is used to mark five alignment points on the patient's skin using a metal rod with a felt-pen marker at the end. There are two superior points, one anterior point, and two lateral points. Once it has been determined that there are no problems with the placement of the frame with respect to ...
Citations
... A number of Authors gave an explicit formula to determine the appropriate set-up margins in radiotherapy. [22][23][24][25][26] Each formula was built for specific situations of fractionations, beam profiles, target shapes, sites of irradiation, biological dose equivalence, or radiation techniques. Margins should take account of systematic uncertainties, as well as of random uncertainties in the positioning of the patient. ...
... Parker 23 measured the uncertainties in the multileaf collimator positioning, in CT and MRI spatial localization and fusion and in the relocatable head frame; then, he incorporated these data in a Monte Carlo calculation to evaluate various margins and fractionations. Systematic uncertainties were added linearly and combined in quadrature with random errors (assumed to have a Gaussian distribution). ...
Introduction:
A system for stabilizing and monitoring eye movements during LINAC-based photon beam one single fraction stereotactic radiotherapy was developed at our Institution. This study aimed to describe the feasibility and the efficacy of our noninvasive optical localization system that was developed, tested, and applied in 20 patients treated for uveal melanoma.
Methods:
Our system consisted of a customized thermoplastic mask to immobilize the head, a gaze fixation LED, and a digital micro-camera. The localization procedure, which required the active collaboration of the patient, served to monitor the eye movements during all phases of the treatment, starting from the planning computed tomography up to the administration of radiotherapy, and allowed the operators to suspend the procedure and to interact with the patient in case of large movements of the pupil.
Results:
Twenty patients were treated with stereotactic radiosurgery (27 Gy in one fraction) for primary uveal melanoma. All patients showed a good tolerance to the treatment; until now, all patients were in local control during the follow up and one died for distant progression 6 months after radiosurgery.
Conclusions:
This study showed that this noninvasive technique, based on eye position control, is appropriate and can contribute to the success of LINAC-based stereotactic radiotherapy. A millimetric safety margin to the clinical target volume was adequate to take account for the organ movement. All patients treated till now showed a good local control; failures in the disease control were due to metastatic spread.
... Liver movement due to breathing is one of the largest sources of internal organ movement. Target movement up to a few centimeters was obtained for liver, which indicates that liver motion is one of the largest sources of internal organ movement, second only to respiratory movement (9)(10)(11)(12)(13). Motion of tumor and adjacent organs during treatment may lead to an insufficient dose of tumors and/or over-irradiation of normal tissues. ...
... Lots of different methods can specify the margins required for those uncertainties, among which the extents of inter-and intra-fractional variation are significant factors when evaluating individual and population-based margins calculations. Most the margin recipes were expressed in terms population systematic error (S ) and random error (s ) (10,14,(46)(47)(48)(49)(50)(51)(52). Especially, the dose penumbra was also included in the margin formulas (43, 49,53). ...
... Sun et al. 10.3389/fonc.2022.1021119 in LR, AP and SI directions, respectively. The similar histograms for rotational angles around LR(q X ), AP(q Y ) and SI(q Z ) axes were displayed in Figure 3, which indicated that the rotation angles for 95% of the samples were not larger than 3.0 ∘ , 3.5 ∘ and 2.5 ∘ for q X , q Y and q Z , respectively. ...
Objective
Our study aims to estimate intra-fraction six-dimensional (6D) tumor motion with rotational correction and the related correlations between motions of different degrees of freedom (DoF), as well as quantify sufficient anisotropic clinical target volume (CTV) to planning target volume (PTV) margins during stereotactic body radiotherapy (SBRT) of liver cancer with fiducial tracking technique.MethodsA cohort of 12 patients who were implanted with 3 or 4 golden markers were included in this study, and 495 orthogonal kilovoltage (kV) pairs of images acquired during the first fraction were used to extract the spacial position of each golden marker. Translational and rotational motions of tumor were calculated based on the marker coordinates by using an iterative closest point (ICP) algorithm. Moreover, the Pearson product-moment correlation coefficients (r) were applied to quantify the correlations between motions with different degrees of freedom (DoFs). The population mean displacement (MP¯), systematic error (Σ) and random error (σ) were obtained to calculate PTV margins based on published recipes.ResultsThe mean translational variability of tumors were 0.56, 1.24 and 3.38 mm in the left-right (LR, X), anterior-posterior (AP, Y), and superior-inferior (SI, Z) directions, respectively. The average rotational angles θX , θY and θZ around the three coordinate axes were 0.88, 1.24 and 1.12, respectively. (|r|>0.4) was obtainted between Y -Z , Y - θZ , Z -θZ and θX - θY . The PTV margins calculated based on 13 published recipes in X, Y, and Z directions were 1.08, 2.26 and 5.42 mm, and the 95% confidence interval (CI) of them were (0.88,1.28), (1.99,2.53) and (4.78,6.05), respectively.Conclusions
The maximum translational motion was in SI direction, and the largest correlation coefficient of Y-Z was obtained. We recommend margins of 2, 3 and 7 mm in LR, AP and SI directions, respectively.
... Other recipes also may be difficult to accurately translate to cranial radiosurgery/therapy as well due to assumptions and differences in the targeted population [12][13][14]. Consequently, four published recipes have been selected for use in this study: International Council on Radiation Units and Measurements (ICRU) methodology, VHMF with effective uncertainty values, Zhang et al. and Parker et al. [13,[15][16][17]. The ICRU methodology is a generic base minimum recommendation for applying setup margin and therefore shall be applied as a baseline recipe [15]. ...
... Originally intended for single fraction regimens, however, it would present a maximum possible margin for comparison in multi-fraction cases as well [16,18]. Parker et al. developed their recipe for hypofractionation situations with the assumption of a 20%/mm beam penumbra which is decent for Gamma Knife though perhaps limited still since the penumbra of Gamma Knife are not symmetric and therefore some uncertainties exist in its Gamma Knife application [17]. ...
... This study sought to experimentally apply setup margins to frameless Gamma Knife treatment planning in order to observe quantitatively the effects on the dose distribution and discern a rational approach to setup margin application for frameless radiosurgery with the Gamma Knife Icon. Select published margin recipes ( Table 1) were used to provide setup margins recommendations that were then applied to targets of 30 previously treated patients [11,15,[17][18]20]. ...
Objective
The objective is to explore the possibility of optimal/rational application of setup margin during treatment planning for frameless stereotactic Gamma Knife radiosurgery/therapy.
Methods
Uncertainty measurements for frameless Gamma Knife Icon treatment were used to calculate the necessary setup margin via four different published recipes and these margins were subsequently applied to treatment plans of 30 previously treated patients and replans were generated meeting comparable plan quality metrics. All plans were then analyzed based on the ability to maintain normal tissue dose tolerances and the relative increase in target dose coverage probability using a pass/fail scoring system based on published normal tissue dose constraints and an in-house developed optimal scoring method.
Results
Gross tumor volume/planning target volume (GTV/PTV) size strongly correlated with both meeting normal tissue tolerances and optimal scores for single fraction plans corroborating published clinical outcomes. The Van Herk Margin Formula (VHMF) and Parker margin formulae were indicated as good candidates for high probabilities of both meeting normal tissue goals and high optimal scores which generally translated to just over 1 mm in GTV to PTV margin.
Conclusion
For single fraction treatment, GTV size is highly significant in predicting failure to meet normal tissue goals whereas whether setup margin was used was not a significant predictor. Setup margin can rationally be applied when fraction number is dictated by clinically indicated metrics regarding GTV size of greater or less than 4 cc. 1 mm is a reasonable practical application of margin added to GTV to ensure physical prescription dose target coverage for most cases when clinically desired based on disease type and intended outcome.
Ce travail basé sur les mouvements respiratoires de 70 patients a pour objectif de quantifier le sens, la direction, la vitesse et l'amplitude du mouvement des tumeurs pulmonaires traitées en condition stéréotaxiques (SBRT), afin de pouvoir déterminer la technique de traitement la plus adéquate.Les images dynamiques (4D) obtenues pendant les cycles respiratoires nous ont permis d’observer et analyser le mouvement des tumeurs en fonction de leur localisation dans les poumons. Le mouvement dans les lobes inférieurs est prédominant dans la direction cranio-caudale (CC) avec ou sans hystérésis avec un déplacement maximal de 24 mm. Dans les lobes supérieurs, les mouvements sont plus complexes : elliptique, diagonal (plan x, y) et antéro-postérieur (AP), avec un déplacement maximal de 10.1 mm. Les vitesses de déplacement sont plus élevées dans le lobe inférieur par rapport au lobe supérieur, où la vitesse de la tumeur est plus grande dans la région centrale, en particulier dans le poumon gauche (44 mm/s). Sur un cycle, la vitesse de la tumeur varie selon les phases et passe par un minimum où l’accélération est nulle sur plusieurs phases (4 - 5 phases en expiration). La vitesse de la tumeur va déterminer le choix de la technique.Dans le cas d’une vitesse tumorale > 25 mm/s, sans phase stable (accélération non nulle), la vitesse de la tumeur change pendant le cycle respiratoire et dépend de la phase. Dans certaines phases, la vitesse de la tumeur peut être supérieure à la vitesse des lames du collimateur multi-lames (MLC) et peut, à son tour, introduire une incertitude géométrique supplémentaire pendant l'administration du traitement. Dans ce cas, le traitement doit porter sur l’ITV, de manière à intégrer tous les déplacements de la tumeur durant le cycle respiratoire.Si vitesse de la lésion est < à 25 mm/s, sans phase stable, nous pouvons utiliser la technique de tracking à condition que la vitesse de la tumeur ne dépasse pas la vitesse du MLC. Quand la vitesse de la lésion reste faible (< 5 mm/s) et constante (accélération nulle) durant quelques phases (40 % du cycle) la technique de gating semble la plus adaptée.L’objectif est de diminuer le volume traité. Dans le parenchyme pulmonaire, le traitement sur l’ITV, génère un volume traité plus important et de faible densité ce qui entraine une augmentation du nombre d’UM et de la dose aux OARs.Sur l’ITV, outrepasser la densité de l’ITV permet de réduire le nombre d’UM et la dose aux OARs. Nous avons déterminé que pour une densité du PTV < 0,36 g/cm3 il était recommandé d’affecter à l’ITV une densité de 0,8 g/cm3.Pour diminuer le volume traité, et limiter à la fois l’importance de la densité et le mouvement des OARs, nous avons évalué la capacité de l’accélérateur Truebeam STx à irradier selon les techniques gating basées sur la phase ou l’amplitude, avec des faisceaux 6 MV FFF (IQ : 0,63). En délivrant les doses en mode gated et non-gated, nous avons trouvé que l’output facteur est 1,4 % inférieur à 2 % selon les recommandations de l’AAPM TG 142. L'écart de dose entre les résultats planifiés et mesurés avec une chambre d’ionisation PinPoint (PTW), dans les deux modes (phase and amplitude) est inférieur à 3 % pour une respiration régulière et de 7 % pour une respiration irrégulière.Pour conclure, les tumeurs pulmonaires en SBRT possédant des phases stables dans le cycle peuvent être traitées en mode gating : en phase, sur des phases de 30 à 60 % ou en amplitude avec un seuil de l’ordre du tiers de l’amplitude maximale. En respiration régulière, le mode amplitude assure un facteur d’utilisation de faisceau élevé (53 %) plus élevé qu’en mode phase. En respiration irrégulière, le mode phase parait le plus adéquat si le niveau d’irrégularité de la courbe porte sur la période ou l’amplitude. En cas de complexités plus élevées cumulant toutes les irrégularités de phase et d’amplitude, aucun mode n’est adapté et un traitement sur l’ITV doit être préconisé.
Objective:
Frameless treatment with the Gamma Knife Icon is still relatively new as a treatment option. As a result, additional confidence/knowledge about the uncertainty that exists within each portion of the treatment workflow could be gained especially regarding steps that have not been previously studied in the literature.
Methods:
The Icon base delivery device (Perfexion) uncertainty is quantified and validated. The novel portions of the Icon such as mask immobilization, cone-beam computed tomography image guidance, and the intrafraction motion management methods are studied specifically and to a greater extent to determine a total workflow uncertainty of frameless treatment with the Icon.
Results:
The uncertainty of each treatment workflow step has been identified with the total workflow uncertainty being identified in this work as 1.3 mm with a standard deviation of 0.51 mm.
Conclusion:
The total uncertainty of frameless treatment with the Icon has been evaluated and this data may indicate the need for setup margin in this setting with data that could be used by other institutions to calculate needed setup margin per their preferred recipe after validation of this data in their context.
Background
No consensus currently exists about the correct margin size to use for spinal SBRT. Margins have been proposed to account for various errors individually, but not with all errors combined to result in a single margin value. The purpose of this work was to determine a setup margin for five-fraction spinal SBRT based on known errors during radiotherapy to achieve at least 90% coverage of the clinical target volume with the prescription dose for at least 90% of patients and not exceed a 30 Gy point dose or 23 Gy to 10% of the spinal cord subvolume.
Methods
The random and systematic error components of intrafraction motion, residual setup error, and end-to-end system accuracy were measured. The patient’s surface displacement was measured to quantify intrafraction motion, the residual setup error was quantified by re-registering accepted daily cone beam computed tomography setup images, and the displacement between measured and planned dose profiles in a phantom quantified the end-to-end system accuracy. These errors and parameters were used to identify the minimum acceptable margin size. The margin recommendation was validated by assessing dose delivery across 140 simulated patient plans suffering from various random shifts representative of the measured errors.
Results
The errors were quantified in three dimensions and the analytical margin generated was 2.4 mm. With this margin applied in the superior/inferior direction only, at least 90% of the CTV was covered with the prescription dose for 96% of the 140 patients simulated with minimal negative effect on the spinal cord dose levels.
Conclusions
The findings of this work support that a 2.4 mm margin applied in the superior/inferior direction can achieve at least 90% coverage of the CTV for at least 90% of dual-arc volumetric modulated arc therapy spinal SBRT patients in the presence of errors when immobilized with vacuum bags.
PurposeTo determine whether setup errors during external beam radiation therapy (RT) for prostate cancer are influenced by the combination of androgen deprivation treatment (ADT) and RT. Materials and methodsData from 175 patients treated for prostate cancer were retrospectively analyzed. Treatment was as follows: concurrent ADT plus RT, 33 patients (19%); neoadjuvant and concurrent ADT plus RT, 91 patients (52%); RT only, 51 patients (29%). Required couch shifts without rotations were recorded for each megavoltage (MV) cone beam computed tomography (CBCT) scan, and corresponding alignment shifts were recorded as left–right (x), superior–inferior (y), and anterior–posterior (z). The nonparametric Mann–Whitney test was used to compare shifts by group. Pearson’s correlation coefficient was used to measure the correlation of couch shifts between groups. Mean prostate shifts and standard deviations (SD) were calculated and pooled to obtain mean or group systematic error (M), SD of systematic error (Σ), and SD of random error (σ). ResultsNo significant differences were observed in prostate shifts in any direction between the groups. Shifts on CBCT were all less than setup margins. A significant positive correlation was observed between prostate volume and the z‑direction prostate shift (r = 0.19, p = 0.04), regardless of ADT group, but not between volume and x‑ or y‑direction shifts (r = 0.04, p = 0.7; r = 0.03, p = 0.7). Random and systematic errors for all patient cohorts and ADT groups were similar. Conclusion
Hormone therapy given concurrently with RT was not found to significantly impact setup errors. Prostate volume was significantly correlated with shifts in the anterior–posterior direction only.
An integrated treatment delivery system for conformal stereotactic radiosurgery (CSRS) and radiotherapy (CSRT) has been developed through a collaboration involving Siemens Medical Systems, Inc., Tyco/Radionics, Inc., and The University of Texas M. D. Anderson Cancer Center. The system consists of a 6-MV linear accelerator (LINAC) equipped with a Tyco/Radionics miniature multileaf collimator (mMLC). For the conventional SRS treatment, the circular collimator housing can be attached to the opening window of the mMLC. The treatment delivery system is integrated with a radiotherapy treatment planning system and a record-and-verify system. The purpose of this study is to report the characteristics, performance, benefits, and the clinical applications of this delivery system. The technical specifications of the LINAC and mMLC were tested, and all the specifications were met. The 80% to 20% penumbral width for each mMLC leaf is approximately 3 mm and is nearly independent of the off-axis positions of a leaf. The maximum interleaf leakage is 1.4% (1.1% on average) and the maximum intra-leaf leakage is 1.0% (0.9% on average). The leaf position precision is better than 0.5 mm for all the leaves. The integration of the SRS/SRT treatment planning system, mMLC, and LINAC has been evaluated successfully for transferring the patient treatment data file through radiotherapy treatment planning system to the patient information and treatment record-and-verify server and the mMLC controller. Subsequently, the auto-sequential treatment delivery for SRS, CSRS/CSRT, and the step-and-shoot intensity-modulated radiotherapy has also been tested successfully. The accuracy of dose delivery was evaluated for a 2-cm spherical target in a Radiological Physics Center SRS head phantom with GAFChromic films and TLD. Five non-coplanar arcs, using a 2-cm diameter circular collimator, were used for this simulation treatment. The accuracy to aim the center of the spherical target was within 0.5 mm and the deviation of dose delivery to the isocenter of the target was within 2% of the calculated dose. For the irregularly shaped tumor, a tissue-equivalent head phantom was used to evaluate the accuracy of dose delivery for using either geometric conformal treatment or IMRT The accuracy of dose delivery to the isocenter was within 2% and 3% of the calculated dose, respectively. From October 26, 1999 to September 30, 2002, we treated over 400 SRS patients and 70 SRT patients. Four representative cases are presented to illustrate the capabilities of this dedicated unit in performing conventional SRS, CSRS, and CSRT. For all the cases, the geometric conformal-plan dose distributions showed a high degree of conformity to the target shape. The degree of conformity can be evaluated using the target-volume-ratio (TVR). Our preferred TVR values for highly conformed dose distributions range from 1.6 to 2.0. The patient setup reproducibility for the Gill-Thomas-Cosman (GTC) noninvasive head frame ranges from 0.5 to 1 mm, and the head and neck noninvasive frame is within 2 mm. The integrated treatment delivery system offers excellent conformation for complicated planning target volumes with the stereotactic setup approach, ensuring that dose delivery can be achieved within the specified accuracy. In addition, the treatment time is comparable with that of single isocenter multiple-arc treatments.
PACS number(s): 87.53.Kn, 87.53.Ly
Background
Large tumor motion often leads to larger treatment volumes, especially the lung tumor located in lower lobe and adhered to chest wall or diaphragm. The purpose of this work is to investigate the impacts of planning target volume (PTV) margin on Stereotactic Body Radiotherapy (SBRT) in non-small cell lung cancer (NSCLC). Methods
Subjects include 20 patients with the lung tumor located in lower lobe and adhered to chest wall or diaphragm who underwent SBRT. Four-dimensional computed tomography (4DCT) were acquired at simulation to evaluate the tumor intra-fractional centroid and boundary changes, and Cone-beam Computer Tomography (CBCT) were acquired during each treatment to evaluate the tumor inter-fractional set-up displacement. The margin to compensate for tumor variations uncertainties was calculated with various margin calculated recipes published in the exiting literatures. ResultsThe means (±standard deviation) of tumor centroid changes were 0.16 (±0.13) cm, 0.22 (±0.15) cm, and 1.37 (±0.81) cm in RL, AP, and SI directions, respectively. The means (±standard deviation) of tumor edge changes were 0.21 (±0.18) cm, 0.50 (±0.23) cm, and 0.19 (±0.44) cm in RL, AP, and SI directions, respectively. The means (±standard deviation) of tumor set-up displacement were 0.03 (±0.24) cm, 0.02 (±0.26) cm, and 0.02 (±0.43) cm in RL, AP, and SI directions, respectively. The PTV margin to compensate for lung cancer tumor variations uncertainties were 0.88, 0.98 and 2.68 cm in RL, AP and SI directions, which were maximal among all margin recipes. Conclusions4DCT and CBCT imaging are appropriate to account for the tumor intra-fractional centroid, boundary variations and inter-fractional set-up displacement. The PTV margin to compensate for lung cancer tumor variations uncertainties can be obtained. Our results show that a conventional 1.0 cm margin in the SI plane dose not suffice to compensate the geometrical variety of the tumor located in lower lobe and adhered to chest wall and diaphragm.
The aim. The aim of this paper was to compare the methods of specifying margins in patients with gastric cancer. Material and methods. The material included 57 patients with gastric cancer during chemoradiotherapy in whom the positioning in the therapeutic system was verified using 2 kV images prior to each radiotherapy fraction. Subsequently, shifts in three axes were assessed. Based on the shifts obtained, systematic and random errors were calculated in given axes and margins were specified using the van Herk, Stroom and ICRU 62 formulae. Results. The margins resulting from the interfraction motion based of the van Herk, Stroom and ICRU formulae were as follows: 9 mm, 7 mm and 6 mm in the lateral axis, 16 mm, 14 mm and 11 mm in the craniocaudal axis as well as 8 mm, 7 mm and 5 mm in the anteroposterior axis, respectively for each formula. The lowest percentage of shifts that were greater than the calculated margin was observed in the van Herk method (1.5% in the lateral axis, 3.3% in the craniocaudal axis and 1.9% in the anteroposterior axis). Conclusions. Based on the material investigated, the margin recommended for centers in which daily patient position verification is not possible is the one calculated with the use of the van Herk formula.
