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Objective: The aim of the study is to compare the accuracy of dose calculation for different dose calculation algorithms with different prescription points (air, tissue, air--tissue interface in carcinoma lung patients and bone, tissue, and bone--tissue interface in carcinoma buccal Mucosa tumors). Materials and Methods: Forty-one patients with carcinoma lung and buccal mucosa were retrospectively selected for this study. A three-dimensional conformal radiotherapy reference plan was created using the prescription point in the tissue with Monte Carlo (MC) algorithms for both the groups of patients. The reference plan was modified by changing the prescription point and algorithms in the tissue, air, air--tissue interface for lung patients and tissue, bone, and bone--tissue interface for buccal mucosa patients. The dose received by the target volume and other organs at risk (OAR) structures was compared. To find out the statistical difference between different prescription points and algorithms, the statistical tests were performed with repeated measures ANOVA. Results: The target volume receiving 95% dose coverage in lung patients decreased to -3.08%, -5.75%, and -1.87% in the dose prescription point at the air--tissue interface with the dose calculation algorithms like MC, collapsed cone (CC), and pencil beam (PB), respectively, compared to that of the MC tissue. Spinal cord dose was increased in the CC and PB algorithms in all prescription points in patients with lung and buccal mucosa. OAR dose calculated by PB in all prescription points showed a significant deviation compared to MC tissue prescription point. Conclusion: This study will help demonstrate the accuracy of dose calculation for the different dose prescription points with the different treatment algorithms in radiotherapy treatment planning. [ABSTRACT FROM AUTHOR]

Background: Intensity-modulated radiation therapy (IMRT) may have too many peaks and valleys, making the treatment plan undeliverable. When there are too many fluency differences between adjacent pixels in the X or Y directions, the X and Y smoothing factors are utilized as weighting factors to penalize this behavior. Generally, a high degree of complexity is accompanied by many monitor units (MUs), large number of segments, small sized segments, and complex segment shapes. The degree of plan delivery uncertainty can all increase with a higher detailed fluence map. Aim: This study aims to evaluate the dosimetric effects of various smoothing levels on the planning target volume (PTV) and organs at risk (OARs) for cervix cancer. Materials and Methods: IMRT treatment plans were re‑optimized by combining several values of the X and Y penalty between 0 and 100. The dose–volume histogram assessed various dosimetric indicators for PTV and OARs. Additionally, gamma passing rates were evaluated and noted as an indicator of the complex treatment plan. Results: At X = 60, Y = 60 fluence map penalty, the conformity index (CI) value reached its highest value of 0.996 ± 0.004. At X = 0, Y = 0, the homogeneity index (HI) was determined to have a maximum value of 0.0628 ± 0.0235. The highest and lowest MU values were 2424.30 ± 471.12 and 1087.80 ± 91.57, respectively, with X = 0, Y = 0 and X = 100, Y = 100. At X = 100, Y = 100, the gamma passing rate reaches its highest value of 99.28% ± 0.44% and minimum value of 85.93% ± 3.87% at X = 0, Y = 0. Conclusion: The CI and HI values showed no discernible fluctuation, and the OAR doses were barely affected as smoothing was increased. When the smoothing factor was raised, the number of MUs sharply dropped, and a decrease in the number of segments and higher gamma passing rates were also seen. [ABSTRACT FROM AUTHOR]

Background: The process of radiotherapy treatment planning and delivery involves multiple steps and professionals causing it to be prone to errors. Radiotherapy centers equipped with old telecobalt machines have certain peculiar challenges to workflow. We designed and tested a checklist for radiotherapy technicians (RTTs) to reduce chances of error during treatment delivery on a telecobalt machine. Materials and Methods: A physical checklist was designed for RTTs to use in the pretreatment pause using a template advocated by the American Association of Physicists in Medicine. It was tested on 4 RTTs over 1000 radiotherapy delivery sittings. Results: The checklist helped to rectify 41 documentary lapses and 28 errors in radiotherapy treatment parameters while also identifying 12 instances where treatment plan modifications were due and 30 where the patient was due for review by the radiation oncologist. The average time to go through the checklist was between 2.5 and 3 min. Conclusions: The development and use of the checklist has helped in reducing errors and also improving workflow in our department. It is recommended to utilize such physical checklists in all radiotherapy centers with telecobalt machines. The success of the checklist depends upon leadership, teamwork, acceptance of a need to inculcate a "safety culture," with voluntary error-reporting and a willingness to learn from such errors. [ABSTRACT FROM AUTHOR]

Purpose: The present study aims to design and fabricate a novel, versatile, and cost-effective Polymethyl Methacrylate (PMMA) head phantom for the dosimetric pretreatment verification of radiotherapy (RT) treatment plans. Materials and Methods: The head phantom designing involves slice-wise modeling of an adult head using PMMA. The phantom has provisions to hold detectors such as ionization chambers of different sizes, Gafchromic films, gel dosimeter, and optically stimulated luminescence dosimeter. For the point dose verification purpose, 15 volumetric modulated arc therapy patient plans were selected, and doses were measured using a CC13 ionization chamber. The percentage gamma passing rate was calculated for acceptance criteria 3%/3 mm and 2%/2 mm using OmniPro I'mRT film QA software, and Gafchromic EBT3 films were used for 2D planar dose verification. Results: Treatment planning system calculated, and the measured point doses showed a percentage deviation ranged from 0.26 to 1.92. The planar dose fluence measurements, for set acceptance criteria of 3%/3 mm and 2%/2 mm, percentages of points having gamma value <1 were in the range of 99.17 ± 0.25 to 99.88 ± 0.15 and 93.16 ± 0.38 to 98.89 ± 0.23, respectively. Measured dose verification indices were within the acceptable limit. Conclusions: The dosimetric study reveals that head phantom can be used for routine pretreatment verification for the cranial RT, especially for stereotactic radiosurgery/RT as a part of patient-specific quality assurance. The presently fabricated and validated phantom is novel, versatile, and cost-effective, and many institutes can afford it. [ABSTRACT FROM AUTHOR]

Background: Radiotherapy plays an important role in the management of cancer. Although the improved technologies increase therapeutic index, different delivery techniques deliver different dose pattern to the healthy tissue within and outside treatment volume. Objective: The objective of this study was to evaluate the low, intermediate, and high dose to healthy tissue within and outside the treatment volume and to find the relation between tumor volume and various doses received healthy tissue volume. Materials and Methods: A total of 150 patients were included. For all patients, planning computed tomography images were acquired. Tumors, critical structures, and healthy tissue volumes at different regions were delineated. Two sets of plans, one with volumetric-modulated arc therapy and another with intensity-modulated radiation therapy (IMRT) were created, optimized for 6 MV photons and dose was calculated. Dosimetry results for tumor, organs at risks (OARs), and healthy tissue from both the techniques were evaluated and compared. Results: Tumor coverage and dose to OARs was significantly better with volumetric-modulated arc therapy (VMAT). Volume of healthy tissue received high-dose within the treatment volume as well as volume of healthy tissue received low and intermediate-dose out of treatment volume were significantly (P < 0.002) lesser with VMAT. Besides, the results showed that as the tumor volume increased, the various dose received healthy tissue volume also increased. Conclusions: VMAT plan can reduce the risk of secondary malignancy while treating different sites of cancer. VMAT is the most appropriate technique than IMRT, especially in the treatment of large tumor volume. Special attention has to be given, especially while treating women and children. [ABSTRACT FROM AUTHOR]

Aim: Several plan quality metrics are available for the evaluation of stereotactic radiosurgery/radiotherapy plans. This is a retrospective analysis of 60 clinical treatment plans of arteriovenous malformation (AVM) patients to study clinical usefulness of selected plan quality metrics. Materials and Methods: The treatment coverage parameters Radiation Therapy Oncology Group (RTOG) Conformity Index (CIRTOG), RTOG Quality of Coverage (QRTOG), RTOG Homogeneity Index (HIRTOG), Lomax Conformity Index (CILomax), Paddick's Conformity Index (CIPaddick), and dose gradient parameters Paddick's Gradient Index (GIPaddick) and Equivalent Fall-off Distance (EFOD) were calculated for the cohort of patients. Before analyzing patient plans, the influence of calculation grid size on selected plan quality metrics was studied on spherical targets. Results: It was found that the plan quality metrics are independent of calculation grid size =2 mm. EFOD was found to increase linearly with increase in target volume, and a linear fit equation was obtained. Conclusions: The analysis shows that RTOG indices and EFOD would suffice for routine clinical radiosurgical treatment plan evaluation if a dose distribution is available for visual inspection. [ABSTRACT FROM AUTHOR]

Introduction: Three-dimensional (3D) treatment planning of patient undergoing radiotherapy uses complex and meticulous computational algorithms. These algorithms use 3D voxel data of the patient to calculate the radiation dose distribution and display it over the CT image dataset for treatment plan evaluation. Aims and Objective: The purpose of the present study is the development and implementation of radiobiological evaluation of the radiotherapy treatment plan incorporating the tissue-specific radiobiological parameters. Material and Method: An indigenous program was written in MATLAB® software (version 2011b of Mathworks Inc.) to extract the patient treatment plan data from DICOM-RT files which are exported from the treatment planning system. CT-, Structures- and Dose-Cube matrices are reconstructed from the exported patient plan data. BED and EQD2 based dose volume histograms (DVHs), colorwash and iso-effective dose curves were generated from the physical Dose-Cube using the linear-quadratic (LQ) formalism and tissue-specific radiobiological parameters (α/β). Results and Conclusion: BED-and EQD2-colorwash and iso-effective curves along with BED and EQD2 dose volume histograms provide superior radiobiological information as compared to those of physical doses. This study provides supplementary recipes of radiobiological doses along with the physical doses which are useful for the evaluation of complex radiotherapy treatment plan of the patients. [ABSTRACT FROM AUTHOR]

Introduction: Radiation Therapy Oncology Group (RTOG) report #0813 and 0915 recommends using D2cm and R50% as plan quality metrics for evaluation of normal tissue sparing in stereotactic body radiation therapy (SBRT) of lung lesion. This study introduces dose falloff gradient (DFG) as a tool for analyzing the dose beyond the planning target volume (PTV) extending into normal tissue structures. In ascertaining the impact of PTV size and SBRT planning techniques in DFG, this study questions the independence of the RTOG recommended metrics. Materials and Methods: In this retrospective study, 41 RapidArc lung SBRT plans with 2 or 3 complete or partial arcs were analyzed. PTV volumes ranged between 5.3 and 113 cm3 and their geographic locations were distributed in both lungs. 6MV, 6 MV-FFF, 10 MV, or 10 MV-FFF energies were used. RTOG-0915 metrics conformity index, homogeneity index, D2cm, R50%, and HDloc were evaluated. DFG was computed from the mean and maximum dose in seven concentric 5 mm wide rings outside the PTV. DFG was investigated against the volume of normal lung irradiated by 50% isodose volume. Treatment plans with alternate energy and couch rotations were generated. Results: The dose falloff beyond PTV was modeled using a double exponential fit and evaluated for relationship with intermediate lung dose. Photon energy and beam configuration had a minimal impact on the dose falloff outside. The product of normalized D2cm and R50% was estimated to have a slowly varying value. Conclusions: Dose falloff outside PTV has been studied as a function of radial distance and ascertained by intermediate dose to normal lung. DFG can serve as a complementary plan quality metric. [ABSTRACT FROM AUTHOR]

Concerning clinical trials, intracavitary hyperthermia has already shown antitumor activity and has a potential role in the treatment of prostate cancer. The aim of this study was to document a new intracavitary applicator operating at 433 MHz, designed for transrectal hyperthermia, as well as to assess the specific absorption rate (SAR) distributions in terms of temperature measurements in a soft-tissue phantom. The microwave applicator consists of a dipole-type λ/2, a reflector, and the cooling system. The applicator was placed into a soft-tissue gel-phantom box that was mimicking the dielectric properties of the normal tissue. A calibrated thermometer was implanted inside the phantom at specific locations, to calculate temperature distributions. The maximum value of the SAR was 108 W/kg on the surface's central area at the footprint of the antenna, while the penetration depth was at around 3 cm. Our experimental measurements confirmed the role of the reflector concerning the directivity in a certain area and non icotropic, by means of protecting normal tissues around the prostate. The SAR experimental measurements showed that our applicator might be used effectively as a treatment device for prostate cancer, demonstrating a clear advantage over other similar transrectal devices. [ABSTRACT FROM AUTHOR]

The delivery consistency of a Varian Edge linear accelerator over the entire course of treatment for nasopharynx carcinoma (NPC) and prostate cancer intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) treatment plans was investigated using four different approaches. Three NPCs and three prostate plans were delivered in 34 and 29 consecutive days, respectively, using a Varian Edge equipped with a 120 high-definition (HD) multileaf collimator (MLC). All deliveries were measured with an electronic portal imaging device (EPID), and MapCheck2 and ArcCheck commercial systems with gamma analysis used to compare the results of all daily measurements against the pretreatment patient-specific quality assurance. The daily log files generated were also assessed for differences between the actual and planned doses using an in-house program to replace the original values in the DICOM plan files with the delivered parameter values from the log file, and then exporting the plans back to the treatment planning system for reconstruction of the actual dose delivered. The trajectory log file and EPID methods showed very good agreement, with minimal deviations between the daily delivered and reference doses. However, comparisons of the MapCheck2 and ArcCheck with the EPID revealed statistically significant differences (P < 0.001, one-tailed) with greater daily fluctuations, raising concerns over the performance, and reliability of the MapCheck2 and ArcCheck systems when being used to identify IMRT and VMAT plans with poor dosimetric accuracy. We conclude that the Varian Edge linear accelerator equipped with a 120 HD MLC can consistently deliver IMRT and VMAT plans over the entire treatment course. [ABSTRACT FROM AUTHOR]

Dosimetric accuracy of a volumetric modulated arc therapy (VMAT) plan is directly related to the beam model, particularly with multileaf collimator characterization. Inappropriate dosimetric leaf gap (DLG) value can lead to a suboptimal beam model, with significant failure in patient-specific quality assurance (PSQA) of VMAT plans. This study addressed the systematic issue of beam modeling and developed a practical method to determine the optimal DLG value for a beam model. Several complex VMAT plans were selected for the quality assurance analysis using the variable DLG values. The results of three-dimensional (3D) Gamma analysis as a function of the DLG at 3%/3 mm, 2%/2 mm, and 1%/1 mm criteria were fitted by a polynomial curve. The DLG value corresponding to the maximum Gamma passing rate for each polynomial fitting function was derived, and the average was calculated to be the optimal DLG value for each model. The 3D Gamma analysis was repeated with the optimal DLG value to verify the dosimetric accuracy of each VMAT case by PSQA. Gamma passing rates are seen to vary considerably with the DLG values and different analysis criteria (3%/3 mm, 2%/2 mm, and 1%/1 mm) for each case. The optimal DLG derived for each model was 1.16 mm and 1.10 mm, much larger than the measured value (about 0.3 mm). The beam models with the optimal DLG was able to produce an average Gamma passing rate of 97.1% (range, 94.6%-99.1%) at 3%/3 mm and 93.5% (range, 89.0%-96.5%) at 2%/2 mm for one beam model, and 97.1% (range, 94.8%-99.1%) at 3%/3 mm, and 93.3% (range, 88.8%-96.7%) at 2%/2 mm for another. The overall accuracy of dose calculation for VMAT plans should be optimized with a compromise of varied modulation complexities in a beam model. We have developed a practical method to derive the optimal DLG value for each beam model based on the Gamma passing criterion. This technique should be applicable in general for all beam energies and patient cases. [ABSTRACT FROM AUTHOR]

Purpose: Validation of a new software version of a Monte Carlo treatment planning system through comparing plans generated by two software versions in volumetric-modulated arc therapy (VMAT) for lung cancer. Materials and Methods: Three patients who were treated with 60 Gy/30 fractions in Elekta Synergy™ linear accelerator by VMAT technique with 2% statistical uncertainty (SU) were chosen for the study. Multiple VMAT plans were generated using two different software versions of Monaco treatment planning system TPS (V5.10.02 and V5.11). By keeping all other parameters constant, originally accepted plans were recalculated for the SUs of 0.5%, 1%, 2%, 3%, 4%, and 5%. For plan evaluation, the metrics compared were conformity Index (CI), homogeneity Index (HI), dose coverage to planning target volume (PTV), organ at risk (OAR) doses to spinal cord, pericardium, bilateral lungs-PTV, esophagus, liver, normal tissue integral dose (NTID), volumes receiving dose >5 and >10 Gy, calculation time (tCT), and gamma pass rates. Results: In both versions, CI and HI improved as the SU increased from 0.5% to 5%. No significant dose difference was observed in Dmean to PTV, bilateral lungs-PTV, pericardium, esophagus, liver, normal tissue volume receiving >5, and >10 Gy and NTID. It was observed that while the tCT and gamma pass rates decreased, the maximum dose to PTV increased as the SU increased. No other significant dose differences were observed between the two MC versions compared. Conclusion: For lung VMAT plans, in both versions, SU could be accepted up to 3% per plan with reduced tCT without compromising plan quality and deliverability by accepting variations in point dose and an inhomogeneous dose within the target. The plan quality of Monaco™V5.10.02 was similar to Monaco™TPS-V5.11 except for tCT. [ABSTRACT FROM AUTHOR]

The aim of this study is to compare the physical wedge (PW) with enhanced dynamic wedge (EDW) to determine the difference in the dose distribution affecting the treated breast and the contralateral breast, lungs, heart, esophagus, spine, and surrounding skin in the radiotherapy of breast cancer. Computed tomography (CT) data sets of 30 breast cancer patients were selected from the database for the study. The treatment plans which were executed with PW were re-planned with EDW without changing the beam parameters. Keeping the wedge angles same, the analytic anisotropic algorithm (AAA) with heterogeneity correction was used for dose calculation in all plans. The prescription was 50 Gy in 25 fractions. The dose-volume histogram (DVH) of the planning target volume (PTV) and critical structures of both PW and EDW plans were analyzed. The analysis showed that the maximum dose within the target volume is higher in EDW plan compared to PW plan. However the PTV conformity index (CI) remained the same in both plans. For all the critical structures, the EDW technique offered less dose compared to PW technique. The effect of volume of the contralateral breast on the dose to contralateral breast and the effect of volume of PTV breast for patients with carcinoma left breast on the dose to heart were studied and analyzed for the two wedges. No correlation between volumes and dose parameters was found for the two techniques. The number of monitor units to deliver a particular dose with EDW field is less than that of PW field due to change in wedge factor. As EDW produces less scattered dose to structures outside the treatment field, the risk of a second malignancy can be reduced with this technique. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the potential of jaw tracking with the volumetric-modulated arc therapy (VMAT) to reduce the normal tissue dose. Plans of nasopharynx, lung, and prostate cancers (10 plans for each) were used to perform VMAT with and without jaw tracking. The dose reduction was evaluated in terms of organ doses and integral doses. Organ-dose reduction with jaw tracking was statistically significant in the volume receiving a dose of 5 Gy (V5) of bladder, rectum, and lung, the volume receiving a dose of 10 Gy (V10) of bladder, rectum, and lung, and the mean dose of lung (P < 0.05). Integral-dose reduction with jaw tracking was statistically significant in almost all the treatment plans (P < 0.05). For organ-dose reduction, jaw tracking in VMAT plan was effective in reducing V5 and V10. For integral-dose reduction, jaw tracking in VMAT plan is an efficient method for decreasing V5. [ABSTRACT FROM AUTHOR]

Introduction: In this article, we report the results of our investigation on comparison of radiobiological aspects of treatment plans with linear accelerator-based intensity-modulated radiation therapy and volumetric-modulated arc therapy for patients having hippocampal avoidance whole-brain radiation therapy. Materials and Methods: In this retrospective study using the dose-volume histogram, we calculated and compared biophysical indices of equivalent uniform dose, tumor control probability, and normal tissue complication probability (NTCP) for 15 whole-brain radiotherapy patients. Results and Discussions: Dose-response models for tumors and critical structures were separated into two groups: mechanistic and empirical. Mechanistic models formulate mathematically with describable relationships while empirical models fit data through empirical observations to appropriately determine parameters giving results agreeable to those given by mechanistic models. Conclusions: Techniques applied in this manuscript could be applied to any other organs or types of cancer to evaluate treatment plans based on radiobiological modeling. [ABSTRACT FROM AUTHOR]

Purpose/Aim: To describe a two-phase intensity-modulated radiation therapy (IMRT) treatment planning approach, that is, promising for reduction of oral mucositis risk in locally advanced head-and-neck cancer. Materials and Methods: Ten locally advanced head-and-neck cancer patients who underwent RT were retrospectively collected. Conventional IMRT and volumetric-modulated arc therapy (VMAT) plans were generated for these patients following clinical protocol. Following the first phase of generating conventional IMRT plans, our approach utilized data from Monte Carlo-based kernel superposition dose calculations corresponding to beam apertures (generated from the conventional IMRT plans) and used an exact mathematical programming-based optimization approach applying linear programming (LP) to dose optimization in the second phase. Results: Compared with conventional IMRT and VMAT treatment plans, our novel method achieved better preservation of oral cavity (16%-29% lower mean dose, P < 0.01), parotid glands (6%-17% lower mean dose, P < 0.04), and spinal cord (3-11 Gy lower maximum dose, P < 0.03) and lower doses to nonorgan-at-risk/nontarget normal tissues, with the same or better target coverage. Conclusions: Our LP-based method can be practically implemented in routine clinical use with a goal of limiting radiation-induced oral mucositis for head-and-neck cancer patients. [ABSTRACT FROM AUTHOR]

Cone-beam computed tomography (CBCT) images are presently used for geometric verification for daily patient positioning. In this work, we have compared the images of CBCT with the images of conventional fan beam CT (FBCT) in terms of image quality and Hounsfield units (HUs). We also compared the dose calculated using CBCT with that of FBCT. Homogenous RW3 plates and Catphan phantom were scanned by FBCT and CBCT. In RW3 and Catphan phantom, percentage depth dose (PDD), profiles, isodose distributions (for intensity modulated radiotherapy plans), and calculated dose volume histograms were compared. The HU difference was within ± 20 HU (central region) and ± 30 HU (peripheral region) for homogeneous RW3 plates. In the Catphan phantom, the difference in HU was ± 20 HU in the central area and peripheral areas. The HU differences were within ± 30 HU for all HU ranges starting from -1000 to 990 in phantom and patient images. In treatment plans done with simple symmetric and asymmetric fields, dose difference (DD) between CBCT plan and FBCT plan was within 1.2% for both phantoms. In intensity modulated radiotherapy (IMRT) treatment plans, for different target volumes, the difference was <2%. This feasibility study investigated HU variation and dose calculation accuracy between FBCT and CBCT based planning and has validated inverse planning algorithms with CBCT. In our study, we observed a larger deviation of HU values in the peripheral region compared to the central region. This is due to the ring artifact and scatter contribution which may prevent the use of CBCT as the primary imaging modality for radiotherapy treatment planning. The reconstruction algorithm needs to be modified further for improving the image quality and accuracy in HU values. However, our study with TG-119 and intensity modulated radiotherapy test targets shows that CBCT can be used for adaptive replanning as the recalculation of dose with the anisotropic analytical algorithm is in full accord with conventional planning CT except in the build-up regions. Patient images with CBCT have to be carefully analyzed for any artifacts before using them for such dose calculations. [ABSTRACT FROM AUTHOR]

Dedicated rapid access palliative radiation therapy improves patients' access to care, allowing more timely treatment which would positively impact on quality of life. The TomoTherapy (Accuray, Sunnyvale, CA) system provides megavoltage (MV) fan-beam computed tomography (FBCT) as the image guidance technique, and a module called "statRT" that allows the use of these MV FBCT images for direct planning. The possibility of using this imaging modality for palliative radiotherapy treatment planning is assessed against accepted planning CT standards by performing tests following AAPM TG 66 and an end-to-end measurement. Results have shown that MV FBCT images acquired by TomoTherapy are of sufficient quality for the purpose of target delineation and dose calculation for palliative treatments. Large image noise and extended scan acquisition time are the two main drawbacks, so this imaging modality should only be used for palliative treatments at areas with well-known, easily distinguishable, and relatively immobile targets such as spine and whole brain. [ABSTRACT FROM AUTHOR]

The current work describes the implementation of the American Association of Physicists in Medicine (AAPM)'s Task Group 119 report on a volumetric phantom (Delta4, Scandidos, Uppsala, Sweden) following the stated dose goals, to evaluate the step-and-shoot intensity modulated radiation therapy (IMRT) system. Delta4 consists of diode detectors, lying on two crossed planes, measuring the delivered dose, and providing two-dimensional dosimetric information. Seven plans of different goals and complexity were performed, with individual structure sets. TG199 structure sets and plans were transferred and implemented on the Delta4 phantom taking into account its cylindrical geometry. All plans were delivered with a 6 MV linear accelerator equipped with multileaf collimator of 1 cm thickness. Plan results for each test met the recommended dose goals. The evaluation was performed in terms of dose deviation, distance to agreement, and gamma index passing rate. In all test cases, the gamma index passing rate was measured >90%. Delta4 phantom has proven to be fast, applicable, and reliable for the step-and-shoot IMRT commissioning following TG119's recommended tests. Although AAPM's TG119 report is referring to the implementation of test plans that do not correspond to patient plans, it could be used as an evaluation tool of various IMRT systems, considering the local treatment planning system and the delivery system. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the impact of conformity index in the unified dosimetry index (UDI) score for two different planning techniques namely intensity-modulated radiotherapy (IMRT) and Rapid Arc. Rapid Arc and IMRT plans of 57 patients were evaluated and compared using UDI score which incorporates four indices. To determine the impact of conformity index on the IMRT and Rapid Arc plans, UDI at conformity index one of all plan (UDIunit_CI) score was calculated by assuming conformity index is equal to one. Mean and standard deviations of all indices were calculated. Rapid Arc technique plans of different treatment sites of all patients scored lesser UDI than IMRT plans, and the conformity index of Rapid Arc plan was significantly better than IMRT plan. The average dose gradient, homogeneity, coverage, and conformity index of all sites with Rapid Arc plans were 0.212 ± 0.05, 1.123 ± 0.03, 0.959 ± 0.03, and 1.056 ± 0.09; with IMRT plans were 0.190 ± 0.05, 1.113 ± 0.04, 0.950 ± 0.04, and 1.172 ± 0.16, respectively. UDI score value with actual conformity index of Rapid Arc and IMRT plans differed significantly (P < 0.001). However, UDIunit_CI score values with assumed conformity index equal to one did not differ significantly (P = 0.528). In the comparison of IMRT and Rapid Arc plans using the UDI score, the impact of conformity index was significant. [ABSTRACT FROM AUTHOR]

This study demonstrated the feasibility and advantages of a hybrid, volumetric arc therapy technique that used two 90° coplanar arcs and two three-dimensional conformal tangential beams in the simultaneous-integrated boost radiotherapy of left-sided breast cancer after breast-conserving surgery. A total of nine patients with stage I, left-sided breast cancer who underwent breast-conserving surgery were selected for this retrospective study. For each patient, a hybrid arc plan was generated and then compared with two hybrid intensity-modulated radiotherapy plans. All plans were optimized using the same objectives and dose constraints. The prescription dose was 50.4 Gy to the planning target volume with simultaneous boost to 60 Gy to the expanded gross target volume in 28 fractions. The differences among these hybrid plans were analyzed by the Kolmogorov-Smirnov test or the Wilcoxon rank sum test. The hybrid arc plans achieved the clinical requirements of target dose coverage and normal tissue (NT) dose constraints. It was found that the hybrid arc plans showed advantages in the conformity index of the expanded gross target volume, the V5 of the heart, the D2 of the left ventricle, and the D2 and V50.4 of NTs. The average beam-on time and monitor units of the hybrid arc plans were significantly lower (P < 0.001). [ABSTRACT FROM AUTHOR]

Standardized uptake value (SUV) is an advanced tool for quantitative tumor identification and metabolic target volume delineation (TVD) in diagnostic and therapeutic settings. It is thus important to establish a quality assured process to maintain the traceability of data correctly by positron emission tomography (PET) systems. Patient administration of 18fluoro-deoxy-glucose is increasingly delivered by automated infusion systems (AISs). Whenever AIS is used, its accuracy and traceability measurement need verification. In addition, it was observed that the unreproducible SUV displayed in PET and the treatment planning system (TPS) may cause grave concerns for radiation oncologists for TVD. This concern may complicate the correlation of TVD on PET and TPS and their clinical reporting. The SUV traceability was established from the PET system to AIS. Its accuracy was verified by cross-referencing to the reference dose calibrator traceable to a primary standard. The SUV values were converted in TPS using the in-house "clinical tool" to be identical as in PET, to allow radiation oncologists to use SUV confidently. The outcome of this study enables the clinical groups to rely on the correct SUV values displayed on the TPS and to improve the quality of care for patients in clinical procedures. [ABSTRACT FROM AUTHOR]

Recently, Eclipse treatment planning system (TPS) version 8.8 was upgraded to the latest version 13.6. It is customary that the vendor gives training on how to upgrade the existing software to the new version. However, the customer is provided less inner details about changes in the new software version. According to manufacturer, accuracy of point dose calculations and irregular treatment planning is better in the new version (13.6) compared to the old version (8.8). Furthermore, the new version uses voxel-based calculations while the earlier version used point dose calculations. Major difference in intensity-modulated radiation therapy (IMRT) plans was observed between the two versions after re-optimization and re-calculations. However, minor difference was observed for IMRT cases after performing only re-calculations. It is recommended TPS quality assurance to be performed after any major upgrade of software. This can be done by performing dose calculation comparisons in TPS. To assess the difference between the versions, 25 clinical cases from the old version were compared keeping all the patient data intact including the monitor units and comparing the differences in dose calculations using dose volume histogram (DVH) analysis. Along with DVH analysis, uniformity index, conformity index, homogeneity index, and dose spillage index were also compared for both versions. The results of comparative study are presented in this paper. [ABSTRACT FROM AUTHOR]

To investigate the dose-volume variations of planning target volume (PTV) and organ at risks (OARs) in eleven prostate cancer patients planned with single and double arc volumetric modulated arc therapy (VMAT) when varying collimator angle. Single and double arc VMAT treatment plans were created using Monaco5.0® with collimator angle set to 0°. All plans were normalized 7600 cGy dose to the 95% of clinical target volume (CTV) volume. The single arc VMAT plans were reoptimized with different collimator angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°), and for double arc VMAT plans (0-0°, 15°-345, 30-330°, 45-315°, 60-300°, 75-285°, 90-270°) using the same optimization parameters. For the comparison the parameters of heterogeneity index (HI), dose-volume histogram and minimum dose to the 95% of PTV volume (D95 PTV) calculated and analyzed. The best plans were verified using 2 dimensional ion chamber array IBA Matrixx® and three-dimensional IBA Compass® program. The comparison between calculation and measurement were made by the γ-index (3%/3 mm) analysis. A higher D95 (PTV) were found for single arc VMAT with 15° collimator angle. For double arc, VMAT with 60-300° and 75-285° collimator angles. However, lower rectum doses obtained for 75-285° collimator angles. There was no significant dose difference, based on other OARs which are bladder and femur head. When we compared single and double arc VMAT's D95 (PTV), we determined 2.44% high coverage and lower HI with double arc VMAT. All plans passed the γ-index (3%/3 mm) analysis with more than 97% of the points and we had an average γ-index for CTV 0.36, for PTV 0.32 with double arc VMAT. These results were significant by Wilcoxon signed rank test statistically. The results show that dose coverage of target and OAR's doses also depend significantly on the collimator angles due to the geometry of target and OARs. Based on the results we have decided to plan prostate cancer patients in our clinic with double arc VMAT and 75°-285° collimator angles. [ABSTRACT FROM AUTHOR]

This study investigated the dosimetric differences in treatment plans from flattened and flattening filter-free (FFF) beams from the TrueBeam System. A total of 104 treatment plans with static (sliding window) intensity-modulated radiotherapy beams and volumetric-modulated arc therapy (VMAT) beams were generated for 15 patients involving three cancer sites. In general, the FFF beam provides similar target coverage as the flattened beam with improved dose sparing to organ-at-risk (OAR). Among all three cancer sites, the head and neck showed more important differences between the flattened beam and FFF beam. The maximum reduction of the FFF beam in the mean dose reached up to 2.82 Gy for larynx in head and neck case. Compared to the 6 MV flattened beam, the 10 MV FFF beam provided improved dose sparing to certain OARs, especially for VMAT cases. Thus, 10 MV FFF beam could be used to improve the treatment plan. [ABSTRACT FROM AUTHOR]

In this study, we intend to estimate the effects of normal tissue sparing between intensity modulated radiotherapy (IMRT) treatment plans generated with and without a dose volume (DV)-based physical cost function using equivalent uniform dose (EUD). Twenty prostate cancer patients were retrospectively selected for this study. For each patient, two IMRT plans were generated (i) EUD-based optimization with a DV-based physical cost function to control inhomogeneity (EUDWith DV) and (ii) EUD-based optimization without a DV-based physical cost function to allow inhomogeneity (EUDWithout DV). The generated plans were prescribed a dose of 72 Gy in 36 fractions to planning target volume (PTV). Mean dose, D30%, and D5% were evaluated for all organ at risk (OAR). Normal tissue complication probability was also calculated for all OARs using BioSuite software. The average volume of PTV for all patients was 103.02 ± 27 cm³. The PTV mean dose for EUDwith DV plans was 73.67 ± 1.7 Gy, whereas for EUDwithout DV plans was 80.42 ± 2.7 Gy. It was found that PTV volume receiving dose more than 115% of prescription dose was negligible in EUDwith DV plans, whereas it was 28% in EUDWithout DV plans. In almost all dosimetric parameters evaluated, dose to OARs in EUDWith DV plans was higher than in EUDWithout DV plans. Allowing inhomogeneous dose (EUDWithout DV) inside the target would achieve better normal tissue sparing compared to homogenous dose distribution (EUDWith DV). Hence, this inhomogeneous dose could be intentionally dumped on the high-risk volume to achieve high local control. Therefore, it was concluded that EUD optimized plans offer added advantage of less OAR dose as well as selectively boosting dose to gross tumor volume. [ABSTRACT FROM AUTHOR]

The impetus behind our study was to establish a quantitative comparison between the IRIS collimator and the InCise multileaf collimator (MLC) (Accuray Inc. Synnyvale, CA) for prostate stereotactic body radiation therapy (SBRT). Treatment plans for ten prostate cancer patients were performed on MultiPlan™ 5.1.2 treatment planning system utilizing MLC and IRIS for 36.25 Gy in five fractions. To reduce the magnitude of variations between cases, the planning tumor volume (PTV) was defined and outlined for treating prostate gland only, assuming no seminal vesicle or ex-capsule involvement. Evaluation indices of each plan include PTV coverage, conformity index (CI), Paddick's new CI, homogeneity index, and gradient index. Organ at risk (OAR) dose sparing was analyzed by the bladder wall Dmax and V37Gy, rectum Dmax and V36Gy. The radiobiological response was evaluated by tumor control probability and normal tissue complication probability based on equivalent uniform dose. The dose delivery efficiency was evaluated on the basis of planned monitor units (MUs) and the reported treatment time per fraction. Statistical significance was tested using the Wilcoxon signed rank test. The studies indicated that CyberKnife M6™ IRIS and InCise™ MLC produce equivalent SBRT prostate treatment plans in terms of dosimetry, radiobiology, and OAR sparing, except that the MLC plans offer improvement of the dose fall-off gradient by 29% over IRIS. The main advantage of replacing the IRIS collimator with MLC is the improved efficiency, determined from the reduction of MUs by 42%, and a 36% faster delivery time. [ABSTRACT FROM AUTHOR]

This paper aims to introduce an algorithm called "sensitivity-based beam number selection (SBBNS)" for fully automated and case-specific determination of an optimal number of equispaced beams in intensity-modulated radiotherapy (IMRT). We tested the algorithm in five head and neck cases of varying complexity. We used direct machine parameter optimization method coupled with Auto Plan feature available in Pinnacle TPS (Version 9.10.0) for optimization. The Pearson correlation test shows a correlation of 0.88 between predicted and actual optimal number of beams, which indicates that SBBNS method is capable of predicting optimal number of beams for head and neck cases with reasonable accuracy. The major advantage of the algorithm is that it intrinsically takes into account various case- and machine-specific factors for the determination of optimal number. The study demonstrates that the algorithm can be effectively applied to IMRT scenarios to determine case specific and optimal number of beams for head and neck cases. [ABSTRACT FROM AUTHOR]

Adaptive radiotherapy may improve treatment outcomes for lung cancer patients. Because of the lack of an effective tool for quality assurance, this therapeutic modality is not yet accepted in clinic. The purpose of this study is to develop a deformable physical phantom for validation of dose accumulation algorithms in regions with heterogeneous mass. A three-dimensional (3D) deformable phantom was developed containing a tissue-equivalent tumor and heterogeneous sponge inserts. Thermoluminescent dosimeters (TLDs) were placed at multiple locations in the phantom each time before dose measurement. Doses were measured with the phantom in both the static and deformed cases. The deformation of the phantom was actuated by a motor driven piston. 4D computed tomography images were acquired to calculate 3D doses at each phase using Pinnacle and EGSnrc/DOSXYZnrc. These images were registered using two registration software packages: VelocityAI and Elastix. With the resultant displacement vector fields (DVFs), the calculated 3D doses were accumulated using a mass-and energy congruent mapping method and compared to those measured by the TLDs at four typical locations. In the static case, TLD measurements agreed with all the algorithms by 1.8% at the center of the tumor volume and by 4.0% in the penumbra. In the deformable case, the phantom's deformation was reproduced within 1.1 mm. For the 3D dose calculated by Pinnacle, the total dose accumulated with the Elastix DVF agreed well to the TLD measurements with their differences <2.5% at four measured locations. When the VelocityAI DVF was used, their difference increased up to 11.8%. For the 3D dose calculated by EGSnrc/DOSXYZnrc, the total doses accumulated with the two DVFs were within 5.7% of the TLD measurements which are slightly over the rate of 5% for clinical acceptance. The detector-embedded deformable phantom allows radiation dose to be measured in a dynamic environment, similar to deforming lung tissues, supporting the validation of dose mapping and accumulation operations in regions with heterogeneous mass, and dose distributions. [ABSTRACT FROM AUTHOR]

Monitor units (MUs) calculated by radiotherapy treatment planning systems need to be verified independently. At extended source-surface distances (SSDs), different output factors (OFs) can be given by different independent MU checking packages due to the calculation methods used and assumptions made within them. The accuracy of two software packages - RadCalc® (LifeLine Software Inc., Austin, USA) and eDatabook (Y. Wang, Radiation Oncology Institute, Sydney, AUS) - was determined by comparing the calculated OFs directly to measured OFs for a series of standard electron cutouts on an Elekta Synergy linear accelerator at standard and extended SSDs (100 cm and above). For the majority of the measurements made, eDatabook provided OFs closer to the measured value than RadCalc; however, in two cases, eDatabook was unable to provide a factor. RadCalc failed to calculate the OFs accurately at extended SSDs as its calculation is based on the assumption that the established effective-SSD curve can accurately predict the data where there are no measurements available. The accuracy of eDatabook is due to its use of a linear interpolation to determine the OF at an extended SSD when there are no measurement data available. [ABSTRACT FROM AUTHOR]

Analyzing the characteristics of a low monitor unit (MU) setting is essential, particularly for intensity-modulated techniques. Intensity modulation can be achieved through intensity-modulated radiotherapy (IMRT) or volumetric-modulated arc therapy (VMAT). There is possibility for low MUs in the segments of IMRT and VMAT plans. The minimum MU/segment must be set by the physicist in the treatment planning system at the time of commissioning. In this study, the characteristics such as dose linearity, stability, flatness, and symmetry of 6 MV photon beam of a Synergy linear accelerator at low MU settings were investigated for different dose rates. The measurements were performed for Synergy linear accelerator using a slab phantom with a FC65-G chamber and Profiler 2. The MU linearity was studied for 1-100 MU using a field size of 10 cm x 10 cm. The linearity error for 1 MU was 4.2%. Flatness of the beam was deteriorated in 1 MU condition. The beam stability and symmetry was well within the specification. Using this study, we conclude that the treatment delivered with <3 MU may result in uncertainty in dose delivery. To ensure the correct dose delivery with less uncertainty, it is recommended to use ≥3 MU as the minimum MU per segment in IMRT and VMAT plans. [ABSTRACT FROM AUTHOR]

Modern treatment planning systems provide accurate dosimetry in heterogeneous media (such as a patient's body) with the help of tissue characterization based on computed tomography (CT) number. However, CT number depends on the type of scanner, tube voltage, field of view (FOV), reconstruction algorithm including artifact reduction and processing filters. The impact of these parameters on CT to electron density (ED) conversion had been subject of investigation for treatment planning in various clinical situations. This is usually performed with a tissue characterization phantom with various density plugs acquired with different tube voltages (kilovoltage peak), FOV reconstruction and different scanners to generate CT number to ED tables. This article provides an overview of inhomogeneity correction in the context of CT scanning and a new evaluation tool, difference volume dose-volume histogram (DVH), dV-DVH. It has been concluded that scanner and CT parameters are important for tissue characterizations, but changes in ED are minimal and only pronounced for higher density materials. For lungs, changes in CT number are minimal among scanners and CT parameters. Dosimetric differences for lung and prostate cases are usually insignificant (<2%) in three-dimensional conformal radiation therapy and < 5% for intensity-modulated radiation therapy (IMRT) with CT parameters. It could be concluded that CT number variability is dependent on acquisition parameters, but its dosimetric impact is pronounced only in high-density media and possibly in IMRT. In view of such small dosimetric changes in low-density medium, the acquisition of additional CT data for financially difficult clinics and countries may not be warranted. [ABSTRACT FROM AUTHOR]

With conventional diagnostic X-ray machines with over couch X-ray tubes, it is not possible to obtain anteroposterior (AP) and lateral (Lat) radiographs without changing the posture of the patients. In an old 300 mA X-ray machine with a fluoroscopy screen (12.4 kg) (1995 model), by substituting the screen with suitable counterweight and making provision to take the hoist pillar up to the edge of the wall, we could get isocentric setup for a hospital stretcher kept near the chest stand. This setup provided acceptable AP-Lat radiographs for brachytherapy localization using "Perspex jig" (Nucletron, Netherlands) and field check radiographs in head and neck, esophagus patients for treatment planning. [ABSTRACT FROM AUTHOR]

The objective of this study was to analyze the influence of the increment of gantry angle and the number of arcs on esophageal volumetric modulated arc therapy plan. All plans were done in Monaco planning system for Elekta Synergy linear accelerator with 80 multileaf collimator (MLC). Volumetric modulated arc therapy (VMAT) plans were done with different increment of gantry angle like 15°, 20°, 30° and 40°. The remaining parameters were similar for all the plans. The results were compared. To compare the plan quality with number of arcs, VMAT plans were done with single and dual arc with increment of gantry angle of 20°. The dose to gross tumor volume (GTV) for 60 Gy and planning target volume (PTV) for 48 Gy was compared. The dosimetric parameters D98%, D95%, D50% and Dmax of GTV were analyzed. The homogeneity index (HI) and conformity index (CI) of GTV were studied and the dose to 98% and 95% of PTV was analyzed. Maximum dose to spinal cord and planning risk volume of cord (PRV cord) was compared. The Volume of lung receiving 10 Gy, 20 Gy and mean dose was analyzed. The volume of heart receiving 30 Gy and 45 Gy was compared. The volume of normal tissue receiving greater than 2 Gy and 5 Gy was compared. The number of monitor units (MU) required to deliver the plans were compared. The plan with larger increment of gantry angle proved to be superior to smaller increment of gantry angle plans in terms of dose coverage, HI, CI and normal tissue sparing. The number of arcs did not make any difference in the quality of the plan. [ABSTRACT FROM AUTHOR]

A new planning method for Craniospinal Irradiation by Eclipse treatment planning system using Field alignment, Field-in-Field technique was developed. Advantage of this planning method was also studied retrospectively for previously treated five patients of medulloblastoma with variable spine length. Plan consists of half beam blocked parallel opposed cranium, and a single posterior cervicospine field was created by sharing the same isocenter, which obviates divergence matching. Further, a single symmetrical field was created to treat remaining Lumbosacral spine. Matching between a inferior diverging edge of cervicospine field and superior diverging edge of a Lumbosacral field was done using the field alignment option. 'Field alignment' is specific option in the Eclipse Treatment Planning System, which automatically matches the field edge divergence as per field alignment rule. Multiple segments were applied in both the spine field to manage with hot and cold spots created by varying depth of spinal cord. Plan becomes fully computerized using this field alignment option and multiple segments. Plan evaluation and calculated mean modified Homogeneity Index (1.04 and 0.1) ensured that dose to target volume is homogeneous and critical organ doses were within tolerance. Dose variation at the spinal field junction was verified using ionization chamber array (I'MatriXX) for matched, overlapped and gap junction spine fields; the delivered dose distribution confirmed the ideal clinical match, over exposure and under exposure at the junction, respectively. This method is simple to plan, executable in Record and Verify mode and can be adopted for various length of spinal cord with only two isocenter in shorter treatment time. [ABSTRACT FROM AUTHOR]

It is widely accepted that a redundant independent dose calculation (RIDC) must be included in any treatment planning verification procedure. Specifically, volumetric modulated arc therapy (VMAT) technique implies a comprehensive quality assurance (QA) program in which RIDC should be included. In this paper, the results obtained in 1 year of clinical experience are presented. Eclipse from Varian is the treatment planning system (TPS), here in use. RIDC were performed with the commercial software; Diamond® (PTW) which is capable of calculating VMAT fields. Once the plan is clinically accepted, it is exported via Digital Imaging and Communications in Medicine (DICOM) to RIDC, together with the body contour, and then a point dose calculation is performed, usually at the isocenter. A total of 459 plans were evaluated. The total average deviation was -0.3 ± 1.8% (one standard deviation (1SD)). For higher clearance the plans were grouped by location in: Prostate, pelvis, abdomen, chest, head and neck, brain, stereotactic radiosurgery, lung stereotactic body radiation therapy, and miscellaneous. The highest absolute deviation was -0.8 ± 1.5% corresponding to the prostate. A linear fit between doses calculated by RIDC and by TPS produced a correlation coefficient of 0.9991 and a slope of 1.0023. These results are very close to those obtained in the validation process. This agreement led us to consider this RIDC software as a valuable tool for QA in VMAT plans. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the various dosimetric parameters of dynamic multileaf collimator (MLC) intensity modulated radiation therapy (IMRT) plans with volumetric modulated arc therapy (VMAT) plans for base of tongue cases. All plans were done in Monaco planning system for Elekta synergy linear accelerator with 80 MLC. IMRT plans were planned with nine stationary beams, and VMAT plans were done for 360° arc with single arc or dual arc. The dose to the planning target volumes (PTV) for 70, 63, and 56 Gy was compared. The dose to 95, 98, and 50% volume of PTV were analyzed. The homogeneity index (HI) and the conformity index (CI) of the PTV70 were also analyzed. IMRT and VMAT plan showed similar dose coverage, HI, and CI. Maximum dose and dose to 1-cc volume of spinal cord, planning risk volume (PRV) cord, and brain stem were compared. IMRT plan and VMAT plan showed similar results except for the 1 cc of PRV cord that received slightly higher dose in VMAT plan. Mean dose and dose to 50% volume of right and left parotid glands were analyzed. VMAT plan gave better sparing of parotid glands than IMRT . In normal tissue dose analyses VMAT was better than IMRT . The number of monitor units (MU) required for delivering the good quality of the plan and the time required to deliver the plan for IMRT and VMAT were compared. The number of MUs for VMAT was higher than that of IMRT plans. However, the delivery time was reduced by a factor of two for VMAT compared with IMRT . VMAT plans yielded good quality of the plan compared with IMRT, resulting in reduced treatment time and improved efficiency for base of tongue cases. [ABSTRACT FROM AUTHOR]

ViewRay, a novel technology providing soft-tissue imaging during radiotherapy is investigated for treatment planning capabilities assessing treatment plan dose homogeneity and conformity compared with linear accelerator plans. ViewRay offers both adaptive radiotherapy and image guidance. The combination of cobalt-60 (Co-60) with 0.35 Tesla magnetic resonance imaging (MRI) allows for magnetic resonance (MR)-guided intensity-modulated radiation therapy (IMRT) delivery with multiple beams. This study investigated head and neck, lung, and prostate treatment plans to understand what is possible on ViewRay to narrow focus toward sites with optimal dosimetry. The goal is not to provide a rigorous assessment of planning capabilities, but rather a first order demonstration of ViewRay planning abilities. Images, structure sets, points, and dose from treatment plans created in Pinnacle for patients in our clinic were imported into ViewRay. The same objectives were used to assess plan quality and all critical structures were treated as similarly as possible. Homogeneity index (HI), conformity index (CI), and volume receiving <20% of prescription dose (DRx) were calculated to assess the plans. The 95% confidence intervals were recorded for all measurements and presented with the associated bars in graphs. The homogeneity index (D5/D95) had a 1-5% inhomogeneity increase for head and neck, 3-8% for lung, and 4-16% for prostate. CI revealed a modest conformity increase for lung. The volume receiving 20% of the prescription dose increased 2-8% for head and neck and up to 4% for lung and prostate. Overall, for head and neck Co-60 ViewRay treatments planned with its Monte Carlo treatment planning software were comparable with 6 MV plans computed with convolution superposition algorithm on Pinnacle treatment planning system. [ABSTRACT FROM AUTHOR]

For the head-and-neck cancer bilateral irradiation, intensity-modulated radiation therapy (IMRT) is the most reported technique as it enables both target dose coverage and organ-at-risk (OAR) sparing. However, during the last 20 years, three-dimensional conformal radiotherapy (3DCRT) techniques have been introduced, which are tailored to improve the classic shrinking field technique, as regards both planning target volume (PTV) dose conformality and sparing of OAR's, such as parotid glands and spinal cord. In this study, we tested experimentally in a sample of 13 patients, four of these advanced 3DCRT techniques, all using photon beams only and a unique isocentre, namely Bellinzona, Forward-Planned Multisegments (FPMS), ConPas, and field-in-field (FIF) techniques. Statistical analysis of the main dosimetric parameters of PTV and OAR's DVH's as well as of homogeneity and conformity indexes was carried out in order to compare the performance of each technique. The results show that the PTV dose coverage is adequate for all the techniques, with the FPMS techniques providing the highest value for D95%; on the other hand, the best sparing of parotid glands is achieved using the FIF and ConPas techniques, with a mean dose of 26 Gy to parotid glands for a PTV prescription dose of 54 Gy. After taking into account both PTV coverage and parotid sparing, the best global performance was achieved by the FIF technique with results comparable to that of IMRT plans. This technique can be proposed as a valid alternative when IMRT equipment is not available or patient is not suitable for IMRT treatment. [ABSTRACT FROM AUTHOR]