-
[show abstract]
[hide abstract]
ABSTRACT: BACKGROUND: The accuracy of the two dose calculation engines available for RapidArc planning (both released for clinical use) is investigated in comparison to the COMPASS data. METHODS: Two dose calculation algorithms (Acuros-XB and Anisotropic Analytic Algorithm (AAA)) were used to calculate RA plans and compared to calculations with the Collapsed Cone Convolution algorithm (CC) from the COMPASS system (IBA Dosimetry). CC calculations, performed on patient data, are based on experimental fluence measurements with a 2D array of ion chambers mounted on the linac head. The study was conducted on clinical cases treated with RA. Five cases for each of the following groups were included: Brain, Head and Neck, Thorax, Pelvis and stereotactic body radiation therapy for hypo-fractionated treatments with small fields. COMPASS measurements were performed with the iMatrixx-2D array. RapidArc plans were optimized for delivery using 6MV photons from a Clinac-iX (Varian, Palo Alto, USA). Accuracy of the RA calculation was appraised by means of: 1) comparison of Dose Volume histograms (DVH) metrics; 2) analysis of differential dose distributions and determination of mean dose differences per organ; 3) 3D gamma analysis with distance-to-agreement and dose difference thresholds set to 3%/3mm or 2%/2mm for targets, organs at risks and for the volumes encompassed by the 50 and 10% isodoses. RESULTS: For almost all parameters, the better agreement was between Acuros-XB and COMPASS independently from the anatomical site and fractionation. The same result was obtained from the mean dose difference per organ with Acuros-CC average differences below 0.5% while for AAA-CC data, average deviations exceeded 0.5% and in the case of the pelvis 1%. Relevance of observed differences determined with the 3D gamma analysis resulted in a pass rate exceeding 99.5% for Acuros-CC and exceeding 97.5% for AAA-CC. CONCLUSIONS: This study demonstrated that i) a good agreement exists between COMPASS-CC calculations based on measured fluences with respect to dose distributions obtained with both Acuros-XB and AAA algorithms; ii) 3D dose distributions reconstructed from actual delivery coincide very precisely with the planned data; iii) a slight preference in favor of Acuros-XB was observed suggesting the preference for this algorithm in clinical applications.
Radiation Oncology 06/2013; 8(1):140. · 2.32 Impact Factor
-
The British journal of radiology 02/2013; · 2.11 Impact Factor
-
Marta Scorsetti,
Filippo Alongi,
Antonella Fogliata,
Sara Pentimalli,
Pierina Navarria,
Francesca Lobefalo,
Carlos A Garcia-Etienne,
Alessandro Clivio,
Luca Cozzi,
Pietro Mancosu, [......],
Arianna Rubino,
Andrea Sagona,
Stefano Arcangeli,
Wolfgang Gatzemeier,
Giovanna Masci,
Rosalba Torrisi,
Alberto Testori,
Marco Alloisio,
Armando Santoro,
Corrado Tinterri
[show abstract]
[hide abstract]
ABSTRACT: BACKGROUND: : To report results in terms of feasibility and early toxicity of hypofractionated simultaneous integrated boost (SIB) approach with Volumetric Modulated Arc Therapy (VMAT) as adjuvant treatment after breast-conserving surgery. METHOD: S: Between September 2010 and May 2011, 50 consecutive patients presenting early-stage breast cancer were submitted to adjuvant radiotherapy with SIB-VMAT approach using RapidArc in our Institution (Humanitas). Three out of 50 patients were irradiated bilaterally (53 tumors in 50 patients). All patients were enrolled in a phase I-II trial approved by the ICH ethical committee. All 50 patients enrolled in the study underwent VMAT-SIB technique to irradiate the whole breast with concomitant boost irradiation of the tumor bed. Doses to whole breast and surgical bed were 40.5 Gy and 48 Gy respectively, delivered in 15 fractions over 3 weeks. Skin toxicities were recorded during and after treatment according to RTOG acute radiation morbidity scoring criteria with a median follow-up of 12 months (range 8-16). Cosmetic outcomes were assessed as excellent/good or fair/poor. RESULTS: : The median age of the population was 68 years (range 36-88). According to AJCC staging system, 38 breast lesions were classified as pT1, and 15 as pT2; 49 cases were assessed as N0 and 4 as N1. The maximum acute skin toxicity by the end of treatment was Grade 0 in 20/50 patients, Grade 1 in 32/50, Grade 2 in 0 and Grade 3 in 1/50 (one of the 3 cases of bilateral breast irradiation). No Grade 4 toxicities were observed. All Grade 1 toxicities had resolved within 3 weeks. No significant differences in cosmetic scores on baseline assessment vs. 3 months and 6 months after the treatment were observed: all patients were scored as excellent/good (50/50) compared with baseline; no fair/poor judgment was recorded. No other toxicities or local failures were recorded during follow-up. CONCLUSIONS: : The 3-week course of postoperative radiation using VMAT with SIB showed to be feasible and was associated with acceptable acute skin toxicity profile. Long-term follow-up data are needed to assess late toxicity and clinical outcomes.
Radiation Oncology 08/2012; 7(1):145. · 2.32 Impact Factor
-
Antonella Fogliata,
Marta Scorsetti,
Piera Navarria,
Maddalena Catalano,
Alessandro Clivio,
Luca Cozzi,
Francesca Lobefalo,
Giorgia Nicolini,
Valentina Palumbo,
Chiara Pellegrini,
Giacomo Reggiori,
Antonella Roggio, Eugenio Vanetti,
Filippo Alongi,
Sara Pentimalli,
Pietro Mancosu
[show abstract]
[hide abstract]
ABSTRACT: Background. To appraise the potential of volumetric modulated arc therapy (VMAT, RapidArc) and proton beams to simultaneously achieve target coverage and enhanced sparing of bone tissue in the treatment of soft-tissue sarcoma with adequate target coverage. Material and methods. Ten patients presenting with soft-tissue sarcoma of the leg were collected for the study. Dose was prescribed to 66.5 Gy in 25 fractions to the planning target volume (PTV) while significant maximum dose to the bone was constrained to 50 Gy. Plans were optimised according to the RapidArc technique with 6 MV photon beams or for intensity modulated protons. RapidArc photon plans were computed with: 1) AAA; 2) Acuros XB as dose to medium; and 3) Acuros XB as dose to water. Results. All plans acceptably met the criteria of target coverage (V(95%) >90-95%) and bone sparing (D(1cm3) <50 Gy). Significantly higher PTV dose homogeneity was found for proton plans. Near-to-maximum dose to bone was similar for RapidArc and protons, while volume receiving medium/low dose levels was minimised with protons. Similar results were obtained for the remaining normal tissue. Dose distributions calculated with the dose to water option resulted ∼5% higher than corresponding ones computed as dose to medium. Conclusion. High plan quality was demonstrated for both VMAT and proton techniques when applied to soft-tissue sarcoma.
Acta oncologica (Stockholm, Sweden) 06/2012; · 2.27 Impact Factor
-
Giorgia Nicolini,
Sarbani Ghosh-Laskar,
Shyam Kishore Shrivastava,
Sushovan Banerjee,
Suresh Chaudhary,
Jai Prakash Agarwal,
Anusheel Munshi,
Alessandro Clivio,
Antonella Fogliata,
Pietro Mancosu, Eugenio Vanetti,
Luca Cozzi
[show abstract]
[hide abstract]
ABSTRACT: A feasibility study was performed to evaluate RapidArc (RA), and the potential benefit of flattening filter-free beams, on advanced esophageal cancer against intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT).
The plans for 3D-CRT and IMRT with three to seven and five to seven fixed beams were compared against double-modulated arcs with avoidance sectors to spare the lungs for 10 patients. All plans were optimized for 6-MV photon beams. The RA plans were studied for conventional and flattening filter-free (FFF) beams. The objectives for the planning target volume were the volume receiving ≥ 95% or at most 107% of the prescribed dose of <1% with a dose prescription of 59.4 Gy. For the organs at risk, the lung volume (minus the planning target volume) receiving ≥ 5 Gy was <60%, that receiving 20 Gy was <20%-30%, and the mean lung dose was <15.0 Gy. The heart volume receiving 45 Gy was <20%, volume receiving 30 Gy was <50%. The spinal dose received by 1% was <45 Gy. The technical delivery parameters for RA were assessed to compare the normal and FFF beam characteristics.
RA and IMRT provided equivalent coverage and homogeneity, slightly superior to 3D-CRT. The conformity index was 1.2 ± 0.1 for RA and IMRT and 1.5 ± 0.2 for 3D-CRT. The mean lung dose was 12.2 ± 4.5 for IMRT, 11.3 ± 4.6 for RA, and 10.8 ± 4.4 for RA with FFF beams, 18.2 ± 8.5 for 3D-CRT. The percentage of volume receiving ≥ 20 Gy ranged from 23.6% ± 9.1% to 21.1% ± 9.7% for IMRT and RA (FFF beams) and 39.2% ± 17.0% for 3D-CRT. The heart and spine objectives were met by all techniques. The monitor units for IMRT and RA were 457 ± 139, 322 ± 20, and 387 ± 40, respectively. RA with FFF beams showed, compared with RA with normal beams, a ∼20% increase in monitor units per Gray, a 90% increase in the average dose rate, and 20% reduction in beam on time (owing to different gantry speeds).
RA demonstrated, compared with conventional IMRT, a similar target coverage and some better dose sparing to the organs at risk; the advantage against conventional 3D-CRT was more evident. RA with FFF beams resulted in minor improvements in plan quality but with the potential for additional useful reduction in the treatment time.
International journal of radiation oncology, biology, physics 03/2012; 84(2):553-60. · 4.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To assess the clinical impact of the Acuros XB algorithm (implemented in the Varian Eclipse treatment-planning system) in non-small-cell lung cancer (NSCLC) cases.
A CT dataset of 10 patients presenting with advanced NSCLC was selected and contoured for planning target volume, lungs, heart, and spinal cord. Plans were created for 6-MV and 15-MV beams using three-dimensional conformal therapy, intensity-modulated therapy, and volumetric modulated arc therapy with RapidArc. Calculations were performed with Acuros XB and the Anisotropic Analytical Algorithm. To distinguish between differences coming from the different heterogeneity management and those coming from the algorithm and its implementation, all the plans were recalculated assigning Hounsfield Unit (HU) = 0 (Water) to the CT dataset.
Differences in dose distributions between the two algorithms calculated in Water were <0.5%. This suggests that the differences in the real CT dataset can be ascribed mainly to the different heterogeneity management, which is proven to be more accurate in the Acuros XB calculations. The planning target dose difference was stratified between the target in soft tissue, where the mean dose was found to be lower for Acuros XB, with a range of 0.4% ± 0.6% (intensity-modulated therapy, 6 MV) to 1.7% ± 0.2% (three-dimensional conformal therapy, 6 MV), and the target in lung tissue, where the mean dose was higher for 6 MV (from 0.2% ± 0.2% to 1.2% ± 0.5%) and lower for 15 MV (from 0.5% ± 0.5% to 2.0% ± 0.9%). Mean doses to organs at risk presented differences up to 3% of the mean structure dose in the worst case. No particular or systematic differences were found related to the various modalities. Calculation time ratios between calculation time for Acuros XB and the Anisotropic Analytical Algorithm were 7 for three-dimensional conformal therapy, 5 for intensity-modulated therapy, and 0.2 for volumetric modulated arc therapy with RapidArc.
The availability of Acuros XB could improve patient dose estimation, increasing the data consistency of clinical trials.
International journal of radiation oncology, biology, physics 01/2012; 83(5):1587-95. · 4.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The RapidArc volumetric modulated arc therapy (VMAT) planning process is based on a core engine, the so-called progressive resolution optimizer (PRO). This is the optimization algorithm used to determine the combination of field shapes, segment weights (with dose rate and gantry speed variations), which best approximate the desired dose distribution in the inverse planning problem. A study was performed to assess the behavior of two versions of PRO. These two versions mostly differ in the way continuous variables describing the modulated arc are sampled into discrete control points, in the planning efficiency and in the presence of some new features. The analysis aimed to assess (i) plan quality, (ii) technical delivery aspects, (iii) agreement between delivery and calculations, and (iv) planning efficiency of the two versions.
RapidArc plans were generated for four groups of patients (five patients each): anal canal, advanced lung, head and neck, and multiple brain metastases and were designed to test different levels of planning complexity and anatomical features. Plans from optimization with PRO2 (first generation of RapidArc optimizer) were compared against PRO3 (second generation of the algorithm). Additional plans were optimized with PRO3 using new features: the jaw tracking, the intermediate dose and the air cavity correction options.
Results showed that (i) plan quality was generally improved with PRO3 and, although not for all parameters, some of the scored indices showed a macroscopic improvement with PRO3. (ii) PRO3 optimization leads to simpler patterns of the dynamic parameters particularly for dose rate. (iii) No differences were observed between the two algorithms in terms of pretreatment quality assurance measurements and (iv) PRO3 optimization was generally faster, with a time reduction of a factor approximately 3.5 with respect to PRO2.
These results indicate that PRO3 is either clinically beneficial or neutral in terms of dosimetric quality while it showed significant advantages in speed and technical aspects.
Medical Physics 11/2011; 38(11):5844-56. · 2.83 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To assess the accuracy against measurements of two photon dose calculation algorithms (Acuros XB and the Anisotropic Analytical algorithm AAA) for small fields usable in stereotactic treatments with particular focus on RapidArc(®).
Acuros XB and AAA were configured for stereotactic use. Baseline accuracy was assessed on small jaw-collimated open fields for different values for the spot sizes parameter in the beam data: 0.0, 0.5, 1, and 2 mm. Data were calculated with a grid of 1 × 1 mm(2). Investigated fields were: 3 × 3, 2 × 2, 1 × 1, and 0.8 × 0.8 cm(2) with a 6 MV photon beam generated from a Clinac2100iX (Varian, Palo Alto, CA). Profiles, PDD, and output factors were measured in water with a PTW diamond detector (detector size: 4 mm(2), thickness 0.4 mm) and compared to calculations. Four RapidArc test plans were optimized, calculated and delivered with jaw settings J3 × 3, J2 × 2, and J1 × 1 cm(2), the last was optimized twice to generate high (H) and low (L) modulation patterns. Each plan consisted of one partial arc (gantry 110° to 250°), and collimator 45°. Dose to isocenter was measured in a PTW Octavius phantom and compared to calculations. 2D measurements were performed by means of portal dosimetry with the GLAaS method developed at authors' institute. Analysis was performed with gamma pass-fail test with 3% dose difference and 2 mm distance to agreement thresholds.
Open square fields: penumbrae from open field profiles were in good agreement with diamond measurements for 1 mm spot size setting for Acuros XB, and between 0.5 and 1 mm for AAA. Maximum MU difference between calculations and measurements was 1.7% for Acuros XB (0.2% for fields greater than 1 × 1 cm(2)) with 0.5 or 1 mm spot size. Agreement for AAA was within 0.7% (2.8%) for 0.5 (1 mm) spot size. RapidArc plans: doses were evaluated in a 4 mm diameter structure at isocenter and computed values differed from measurements by 0.0, -0.2, 5.5, and -3.4% for Acuros XB calculations (1 mm spot size), and of -0.1, 0.3, 6.7, and -1.2% for AAA, respectively for J3 × 3, J2 × 2, J1 × 1H, J1 × 1L RapidArc plans. Gamma Agreement Index from 2D dose analysis was higher than 95% for J3 × 3 and J2 × 2 plans, being around 80% for J1 × 1 maps. Sensitivity with respect to the dosimetric leaf gap and transmission factor MLC parameters was evaluated in the four RapidArc plans, showing the need to properly set the dosimetric leaf gap for accurate calculations.
Acuros XB and AAA showed acceptable characteristics for stereotactic small fields if adequate tuning of configuration parameters is performed. Dose calculated for RapidArc stereotactic plans showed an acceptable agreement against point and 2D measurements. Both algorithms can therefore be considered safely applicable to stereotactic treatments.
Medical Physics 11/2011; 38(11):6228-37. · 2.83 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A new-generation low-energy linear accelerator (UNIQUE) was introduced in the clinical arena during 2009 by Varian Medical Systems. The world's first UNIQUE was installed at Oncology Institute of Southern Switzerland and put into clinical operation in June 2010. The aim of the present contribution was to report experience about its commissioning and first year results from clinical operation.
Commissioning data, beam characteristics and the modeling into the treatment planning system were summarized. Imaging system of UNIQUE included a 2D-2D matching capability and tests were performed to identify system repositioning capability. Finally, since the system is capable of delivering volumetric modulated arc therapy with RapidArc, a summary of the tests performed for such modality to assess its performance in preclinical settings and during clinical usage was included.
Isocenter virtual diameter was measured as less than 0.2 mm. Observed accuracy of isocenter determination and repositioning for 2D-2D matching procedures in image guidance was <1.2 mm. Concerning reproducibility and stability over a period of 1 year, deviations from reference were found <0.3 ± 0.2% for linac output, <0.1% for homogeneity, similarly to symmetry. Rotational accuracy of the entire gantry-portal imager system showed a maximum deviation from nominal 0.0 of <1.2 mm. Pre treatment quality assurance of RapidArc plans resulted with a Gamma Agreement Index (fraction of points passing the gamma criteria) of 97.0 ± 1.6% on the first 182 arcs verified.
The results of the commissioning tests and of the first period of clinical operation, resulted meeting specifications and having good margins respect to tolerances. UNIQUE was put into operation for all delivery techniques; in particular, as shown by the pre-treatment quality assurance results, it enabled accurate and safe delivery of RapidArc plans.
Radiation Oncology 09/2011; 6:129. · 2.32 Impact Factor
-
Antonella Fogliata,
Alessandro Clivio,
Luca Cozzi,
Giorgia Nicolini,
Gianfranco A Pesce,
Antonella Richetti, Eugenio Vanetti,
Stefan Bergström,
Per Hållström,
Ines Cafaro,
Emanuela Parietti,
Giovanna Dipasquale,
Damien C Weber,
Pietro Mancosu,
Piera Navarria,
Marta Scorsetti
Radiotherapy and Oncology 09/2011; 102(2):322-3. · 5.58 Impact Factor
-
Marta Scorsetti,
Filippo Alongi,
Simona Castiglioni,
Alessandro Clivio,
Antonella Fogliata,
Francesca Lobefalo,
Pietro Mancosu,
Pierina Navarria,
Valentina Palumbo,
Chiara Pellegrini,
Sara Pentimalli,
Giacomo Reggiori,
Anna M Ascolese,
Antonella Roggio,
Stefano Arcangeli,
Angelo Tozzi, Eugenio Vanetti,
Luca Cozzi
[show abstract]
[hide abstract]
ABSTRACT: To test feasibility and safety of clinical usage of Flattening Filter Free (FFF) beams for delivering ablative stereotactic body radiation therapy (SBRT) doses to various tumor sites, by means of Varian TrueBeam™ (Varian Medical Systems).
Seventy patients were treated with SBRT and FFF: 51 lesions were in the thorax (48 patients),10 in the liver, 9 in isolated abdominal lymph node, adrenal gland or pancreas. Doses ranged from 32 to 75 Gy, depending on the anatomical site and the volume of the lesion to irradiate. Lung lesions were treated with cumulative doses of 32 or 48 Gy, delivered in 4 consecutive fractions. The liver patients were treated in 3 fractions with total dose of 75 Gy. The isolated lymph nodes were irradiated in 6 fractions with doses of 45 Gy. The inclusion criteria were the presence of isolated node, or few lymph nodes in the same lymph node region, in absence of other active sites of cancer disease before the SBRT treatment.
All 70 patients completed the treatment. The minimum follow-up was 3 months. Six cases of acute toxicities were recorded (2 Grade2 and 2 Grade3 in lung and 2 Grade2 in abdomen). No patient experienced acute toxicity greater than Grade3. No other types or grades of toxicities were observed at clinical evaluation visits.
This study showed that, with respect to acute toxicity, SBRT with FFF beams showed to be a feasible technique in 70 consecutive patients with various primary and metastatic lesions in the body.
Radiation Oncology 09/2011; 6:113. · 2.32 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A new algorithm for photon dose calculation, Acuros XB, has been recently introduced in the Eclipse, Varian treatment planning system, allowing, similarly to the classic Monte Carlo methods, for accurate modelling of dose deposition in media. Aim of the present study was the assessment of its behaviour in clinical cases.
Datasets from ten breast patients scanned under different breathing conditions (free breathing and deep inspiration) were used to calculate dose plans using the simple two tangential field setting, with Acuros XB (in its versions 10 and 11) and the Anisotropic Analytical Algorithm (AAA) for a 6MV beam. Acuros XB calculations were performed as dose-to-medium distributions. This feature was investigated to appraise the capability of the algorithm to distinguish between different elemental compositions in the human body: lobular vs. adipose tissue in the breast, lower (deep inspiration condition) vs. higher (free breathing condition) densities in the lung.
The analysis of the two breast structures presenting densities compatible with muscle and with adipose tissue showed an average difference in dose calculation between Acuros XB and AAA of 1.6%, with AAA predicting higher dose than Acuros XB, for the muscle tissue (the lobular breast); while the difference for adipose tissue was negligible. From histograms of the dose difference plans between AAA and Acuros XB (version 10), the dose of the lung portion inside the tangential fields presented an average difference of 0.5% in the free breathing conditions, increasing to 1.5% for the deep inspiration cases, with AAA predicting higher doses than Acuros XB. In lung tissue significant differences are found also between Acuros XB version 10 and 11 for lower density lung.
Acuros XB, differently from AAA, is capable to distinguish between the different elemental compositions of the body, and suggests the possibility to further improve the accuracy of the dose plans computed for actual treatment of patients.
Radiation Oncology 08/2011; 6:103. · 2.32 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A study was realised to evaluate and determine relative figures of merit of a new algorithm for photon dose calculation when applied to inhomogeneous media.
The new Acuros XB algorithm implemented in the Varian Eclipse treatment planning system was compared against a Monte Carlo method (VMC++), and the Analytical Anisotropic Algorithm (AAA). The study was carried out in virtual phantoms characterized by simple geometrical structures. An insert of different material and density was included in a phantom built of skeletal-muscle and HU = 0 (setting "A"): Normal Lung (lung, 0.198 g/cm3); Light Lung (lung, 0.035 g/cm3); Bone (bone, 1.798 g/cm3); another phantom (setting "B") was built of adipose material and including thin layers of bone (1.85 g/cm3), adipose (0.92 g/cm3), cartilage (1.4745 g/cm3), air (0.0012 g/cm3). Investigations were performed for 6 and 15 MV photon beams, and for a large (13 × 13 cm2) and a small (2.8 × 13 cm2) field.
Results are provided in terms of depth dose curves, transverse profiles and Gamma analysis (3 mm/3% and 2 mm/2% distance to agreement/dose difference criteria) in planes parallel to the beam central axis; Monte Carlo simulations were assumed as reference. Acuros XB gave an average gamma agreement, with a 3 mm/3% criteria, of 100%, 86% and 100% for Normal Lung, Light Lung and Bone settings, respectively, and dose to medium calculations. The same figures were 86%, 11% and 100% for AAA, where only dose rescaled to water calculations are possible.
In conclusion, Acuros XB algorithm provides a valid and accurate alternative to Monte Carlo calculations for heterogeneity management.
Radiation Oncology 07/2011; 6:82. · 2.32 Impact Factor
-
Sai Subramanian,
Chilukuri Srinivas,
K Ramalingam,
M Babaiah,
S Thirumalai Swamy,
G Arun,
M Kathirvel,
S Ashok,
Alessandro Clivio,
Antonella Fogliata,
Giorgia Nicolini,
K Srinivasa Rao,
T Pratap Reddy,
Jotwani Amit, Eugenio Vanetti,
Luca Cozzi
[show abstract]
[hide abstract]
ABSTRACT: To evaluate, with a dosimetric and clinical feasibility study, RapidArc (a volumetric modulated arc technique) for hypofractionated stereotactic radiotherapy treatment of large arteriovenous malformations (AVMs).
Nine patients were subject to multimodality imaging (magnetic resonance, computed tomography, and digital subtraction angiography) to determine nidus and target volumes, as well as involved organs at risk (optical structures, inner ear, brain stem). Plans for multiple intensity-modulated arcs with a single isocenter were optimized for a fractionation of 25 Gy in 5 fractions. All plans were optimized for 6-MV photon beams. Dose-volume histograms were analyzed to assess plan quality. Delivery parameters were reported to appraise technical features of RapidArc, and pretreatment quality assurance measurements were carried out to report on quality of delivery.
Average size of AVM nidus was 26.2 cm(3), and RapidArc plans provided complete target coverage with minimal overdosage (V(100%) = 100% and V(110%) < 1%) and excellent homogeneity (<6%). Organs at risk were highly spared. The D(1%) to chiasm, eyes, lenses, optic nerves, and brainstem (mean ± SD) was 6.4 ± 8.3, 1.9 ± 3.8, 2.3 ± 2.2, 0.7 ± 0.9, 4.4 ± 7.2, 12.2 ± 9.6 Gy, respectively. Conformity index (CI(95%)) was 2.2 ± 0.1. The number of monitor units per gray was 277 ± 45, total beam-on time was 2.5 ± 0.3 min. Planning vs. delivery γ pass rate was 98.3% ± 0.9%. None of the patients developed acute toxicity. With a median follow-up of 9 months, 3 patients presented with deterioration of symptoms and were found to have postradiation changes but responded symptomatically to steroids. These patients continue to do well on follow-up. One patient developed headache and seizures, which was attributed to intracranial bleed, confirmed on imaging.
Hypofractionated stereotactic radiotherapy can be successfully delivered using the RapidArc form of volumetric arc technology for intracranial AVMs. The quality of delivery and calculated parameters are in agreement with each other and are in line with published reports for other sites.
International journal of radiation oncology, biology, physics 04/2011; 82(3):1278-84. · 4.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A new algorithm, Acuros® XB Advanced Dose Calculation, has been introduced by Varian Medical Systems in the Eclipse planning system for photon dose calculation in external radiotherapy. Acuros XB is based on the solution of the linear Boltzmann transport equation (LBTE). The LBTE describes the macroscopic behaviour of radiation particles as they travel through and interact with matter. The implementation of Acuros XB in Eclipse has not been assessed; therefore, it is necessary to perform these pre-clinical validation tests to determine its accuracy. This paper summarizes the results of comparisons of Acuros XB calculations against measurements and calculations performed with a previously validated dose calculation algorithm, the Anisotropic Analytical Algorithm (AAA). The tasks addressed in this paper are limited to the fundamental characterization of Acuros XB in water for simple geometries. Validation was carried out for four different beams: 6 and 15 MV beams from a Varian Clinac 2100 iX, and 6 and 10 MV 'flattening filter free' (FFF) beams from a TrueBeam linear accelerator. The TrueBeam FFF are new beams recently introduced in clinical practice on general purpose linear accelerators and have not been previously reported on. Results indicate that Acuros XB accurately reproduces measured and calculated (with AAA) data and only small deviations were observed for all the investigated quantities. In general, the overall degree of accuracy for Acuros XB in simple geometries can be stated to be within 1% for open beams and within 2% for mechanical wedges. The basic validation of the Acuros XB algorithm was therefore considered satisfactory for both conventional photon beams as well as for FFF beams of new generation linacs such as the Varian TrueBeam.
Physics in Medicine and Biology 03/2011; 56(6):1879-904. · 2.83 Impact Factor
-
Antonella Fogliata,
Stefan Bergström,
Ines Cafaro,
Alessandro Clivio,
Luca Cozzi,
Giovanna Dipasquale,
Per Hållström,
Pietro Mancosu,
Piera Navarria,
Giorgia Nicolini,
Emanuela Parietti,
Gianfranco A Pesce,
Antonella Richetti,
Marta Scorsetti, Eugenio Vanetti,
Damien C Weber
[show abstract]
[hide abstract]
ABSTRACT: To report the treatment of cranio-spinal irradiation (CSI) with volumetric modulated arc therapy (RapidArc) in adults and a child.
Five patients from 5 institutions were treated with CSI using RapidArc technology. Patient age varied between 7 and 45 years. The lengths of the planning target volumes (PTV) and dose prescriptions ranged from 54.6 to 78.4 cm, and from 12 to 36 Gy, respectively. Different arc arrangements were used, with two or three isocentres, from two to six modulated arcs, for patient positioned either in prone (n=3) or supine position (n=2). Doses to PTV, organs at risk and non-target tissue are reported for each of the five patients. Data concerning imaging strategy and pre-treatment quality assurance are also reported.
The mean conformity index CI(95%) was 1.05 ± 0.05 (range: 1.00, 1.13). Mean doses to the lenses, lungs, heart, and kidneys were, respectively, 7.6 ± 1.6, 6.6 ± 3.0, 5.7 ± 2.3, and 6.1 ± 2.1 Gy, keeping those value acceptably low. Mean non-target tissue dose was 21.0 ± 3.8% (5.6 ± 1.8 Gy, range: 3.0-8.1 Gy). All patients were successfully planned and treated with RapidArc.
RapidArc techniques achieved highly conformal treatment plans for 5 adults or paediatric patients. Beam-on time was short, and RapidArc plans were satisfactorily delivered to all presented patients.
Radiotherapy and Oncology 03/2011; 99(1):79-85. · 5.58 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A preclinical investigation was undertaken to explore a treatment technique for total marrow irradiation using RapidArc, a volumetric modulated arc technique.
Computed tomography datasets of 5 patients were included. Plans with eight overlapping coaxial arcs were optimized for 6-MV photon beams. Dose prescription was 12 Gy in 2 Gy per fraction, normalized so that 100% isodose covered 85% of the planning target volume (PTV). The PTV consisted of the whole skeleton (including ribs and sternum), from the top of the skull to the medium distal third of the femurs. Planning objectives for organs at risk (OARs) were constrained to a median dose <6 to 7 Gy. OARs included brain, eyes, oral cavity, parotids, thyroid, lungs, heart, kidneys, liver, spleen, stomach, abdominal cavity, bladder, rectum, and genitals. Pretreatment quality assurance consisted of portal dosimetry comparisons, scoring the delivery to calculation agreement with the gamma agreement index.
The median total body volume in the study was 57 liters (range, 49-81 liters), for an average diameter of 47 cm (range, 46-53 cm) and a total length ranging from 95 to 112 cm. The median PTV volume was 6.8 liters (range, 5.8-10.8 liters). The mean dose to PTV was 109% (range, 107-112%). The global mean of median dose to all OARs was 4.9 Gy (range, 4.5-5.1 Gy over the 5 patients). The individual mean of median doses per organ ranged from 2.3 Gy (oral cavity) to 7.3 Gy (bowels cavity). Preclinical quality assurance resulted in a mean gamma agreement index of 94.3 ± 5.1%. The delivery time measured from quality assurance runs was 13 minutes.
Sparing of normal tissues with adequate coverage of skeletal bones was shown to be feasible with RapidArc. Pretreatment quality assurance measurements confirmed the technical agreement between expected and actually delivered dose distributions, suggesting the possibility of incorporating this technique in the treatment options for patients.
International journal of radiation oncology, biology, physics 01/2011; 80(2):628-36. · 4.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A study was carried out to evaluate the robustness and mutual interplay of two variables concurring to generate modulation patterns of the RapidArc (RapidArc) implementation of volumetric modulated are therapy. Dose rate (DR) and gantry speed (GS) are free parameters optimized alongside field aperture shape by the RapidArc engine; however, they are limited by machine constraints and mutually compensate in order to deliver the proper MU/deg during the gantry rotation.
Four test cases (one geometrical and three clinical) were selected and RapidArc plans were optimized using maximum allowed dose rates from 100 to 600 MU/min. The maximum gantry speed was fixed at 4.8 deg/s. Qualitative analysis of DR and GS patterns from these cases was summarized together with quantitative assessment of delivery parameters. Pretreatment quality assurance measurements and scoring of plan quality aimed to determine whether preferable initial conditions might be identified or the optimization engine might be invariant to those variables and capable of providing adequate plans independently from the limits applied.
The results of the study were: (i) High dynamic range in MU/deg is achievable across all dose rates by means of gantry speed modulation; (ii) there is a robust compensation mechanism between the two variables; (iii) from a machine delivery point-of-view, slightly improved accuracy is achieved when lower DRs are applied; however, this does not have practical consequences since measurements and plan evaluation showed a lack of clinically relevant deviation; and (iv) reduced total treatment time is a major advantage of high DR.
A trend toward improved plan quality for clinical cases was observed with high DR but cannot be generalized, due to the limited amount of cases investigated and the consequent limited significance of the observed differences. As a minimum benefit, the reduced total treatment time should be considered as well.
Medical Physics 01/2011; 38(1):264-71. · 2.83 Impact Factor
-
Umesh Mahantshetty,
Swamidas Jamema,
Reena Engineer,
Deepak Deshpande,
Rajiv Sarin,
Antonella Fogliata,
Giorgia Nicolini,
Alessandro Clivio, Eugenio Vanetti,
Shyamkishore Shrivastava,
Luca Cozzi
[show abstract]
[hide abstract]
ABSTRACT: A study was performed to assess dosimetric characteristics of volumetric modulated arcs (RapidArc, RA) and fixed field intensity modulated therapy (IMRT) for Whole Abdomen Radiotherapy (WAR) after ovarian cancer.
Plans for IMRT and RA were optimised for 5 patients prescribing 25 Gy to the whole abdomen (PTV_WAR) and 45 Gy to the pelvis and pelvic nodes (PTV_Pelvis) with Simultaneous Integrated Boost (SIB) technique. Plans were investigated for 6 MV (RA6, IMRT6) and 15 MV (RA15, IMRT15) photons. Objectives were: for both PTVs V90% > 95%, for PTV_Pelvis: Dmax < 105%; for organs at risk, maximal sparing was required. The MU and delivery time measured treatment efficiency. Pre-treatment Quality assurance was scored with Gamma Agreement Index (GAI) with 3% and 3 mm thresholds.
IMRT and RapidArc resulted comparable for target coverage. For PTV_WAR, V90% was 99.8 ± 0.2% and 93.4 ± 7.3% for IMRT6 and IMRT15, and 98.4 ± 1.7 and 98.6 ± 0.9% for RA6 and RA15. Target coverage resulted improved for PTV_Pelvis. Dose homogeneity resulted slightly improved by RA (Uniformity was defined as U5-95% = D5%-D95%/Dmean). U5-95% for PTV_WAR was 0.34 ± 0.05 and 0.32 ± 0.06 (IMRT6 and IMRT15), 0.30 ± 0.03 and 0.26 ± 0.04 (RA6 and RA15); for PTV_Pelvis, it resulted equal to 0.1 for all techniques. For organs at risk, small differences were observed between the techniques. MU resulted 3130 ± 221 (IMRT6), 2841 ± 318 (IMRT15), 538 ± 29 (RA6), 635 ± 139 (RA15); the average measured treatment time was 18.0 ± 0.8 and 17.4 ± 2.2 minutes (IMRT6 and IMRT15) and 4.8 ± 0.2 (RA6 and RA15). GAIIMRT6 = 97.3 ± 2.6%, GAIIMRT15 = 94.4 ± 2.1%, GAIRA6 = 98.7 ± 1.0% and GAIRA15 = 95.7 ± 3.7%.
RapidArc showed to be a solution to WAR treatments offering good dosimetric features with significant logistic improvements compared to IMRT.
Radiation Oncology 11/2010; 5:106. · 2.32 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A study was carried out to evaluate the possibility of delivering volumetric modulated arc therapy with the RapidArc technology under respiratory-gated conditions. The experiments were performed in the framework of a non-clinically released environment. Plans of six patients, all realized for a single arc, were used for the experiments. The Real-time Position Management (RPM) respiratory gating system from Varian was used to generate gate-open signals of different durations. Arcs were delivered applying the different gates creating sequences of beam-hold/beam-on during the dose delivery: the average number of interruptions for a single arc ranged from 0 to 45. Dose prescription was set to 2 Gy and different gate-open periods of 30, 15 and 5 s to keep gantry speed constant at maximum. 5 Gy and 15 Gy doses were then applied to gate-open signals of 5 and 8 s, respectively, to mimic the most challenging conditions of slow gantry rotation and high-frequency interruptions. The 5 and 15 Gy experiments represent dose conditions of clinical interest for stereotactic treatments. For each patient and gating condition, pre-treatment 2D verification measurements were performed using the PTW-729 array in conjunction with the Octavius phantom (PTW, Freiburg); measurements were performed on different days (one per patient, with the complete setup of phantom and detectors every time), while each gating experiment was repeated seven consecutive times for reproducibility (without a new setup of the measurement equipment). Measurements were compared with dose calculations in the treatment planning system (performed without any gating) to appraise the dosimetric impact of the presence of gating and the eventual dependence from the number of interruptions during a single arc. Analysis of machine-registered log files in terms of average deviations between actual and expected positions (from automatic measurements every 50 ms) resulted in mean Delta MU (monitor units) <0.02% for all gating conditions. Delta(Gantry angle) = 0.38 +/- 0.01 degrees for 2 Gy (all gate periods), 0.24 +/- 0.01 degrees for 5 Gy, and 0.10 +/- 0.01 degrees for 15 Gy deliveries. Average deviations for multileaf collimator (MLC) positions (root mean square over all 120 leaves) were 0.45 +/- 0.01 mm for 2 Gy (all gate periods), 0.32 +/- 0.01 mm for 5 Gy and 0.14 +/- 0.01 mm for 15 Gy. Results in terms of dose measurements confirmed that the application of gating to RapidArc delivery does not affect the quality of the dose delivery. With criteria of Delta D = 3%, DTA = 3 mm, the gamma test was passing in a range of 99 to 100% of the measured points for most of the cases (with maximum number of interruptions of about 20 per arc) and from 97 to 98% for the extreme case of 15 Gy and 8 s gate-open signal (corresponding to almost 50 interruptions per arc). In conclusion, RapidArc delivery proved, in a pre-clinical phase and non-clinically released framework, to be reliable and dosimetrically accurate also when applied in conjunction with gating procedures.
Physics in Medicine and Biology 06/2010; 55(12):N347-57. · 2.83 Impact Factor
