Advanced optimization methods for whole pelvic and local prostate external beam therapy

PurposeRadiation treatment planning inherently involves multiple conflicting planning goals, which makes it a suitable application for multicriteria optimization (MCO). This study investigates a MCO algorithm for VMAT planning (VMAT–MCO) for prostate cancer treatments including pelvic lymph nodes and uses standard inverse VMAT optimization (sVMAT) and Tomotherapy planning as benchmarks.MethodsFor each of ten prostate cancer patients, a two stage plan was generated, consisting of a stage 1 plan delivering 22 Gy to the prostate, and a stage 2 plan delivering 50.4 Gy to the lymph nodes and 56 Gy to the prostate with a simultaneous integrated boost. The single plans were generated by three planning techniques (VMAT–MCO, sVMAT, Tomotherapy) and subsequently compared with respect to plan quality and planning time efficiency.ResultsPlan quality was similar for all techniques, but sVMAT showed slightly better rectum (on average D_mean −7%) and bowel sparing (D_mean −17%) compared to VMAT–MCO in the whole pelvic treatments. Tomotherapy plans exhibited higher bladder dose (D_mean +42%) in stage 1 and lower rectum dose (D_mean −6%) in stage 2 than VMAT–MCO. Compared to manual planning, the planning time with MCO was reduced up to 12 and 38 min for stage 1 and 2 plans, respectively.ConclusionMCO can generate highly conformal prostate VMAT plans with minimal workload in the settings of prostate-only treatments and prostate plus lymph nodes irradiation. In the whole pelvic plan manual VMAT optimization led to slightly improved OAR sparing over VMAT–MCO, whereas for the primary prostate treatment plan quality was equal.     

CyberKnife MLC-based treatment planning for abdominal and pelvic SBRT: Analysis of multiple dosimetric parameters,overall scoring index and clinical scoring

PurposeThis study evaluated the plan quality of CyberKnife MLC-based treatment planning in comparison to the Iris collimator for abdominal and pelvic SBRT. Multiple dosimetric parameters were considered together with a global scoring index validated by clinical scoring.Methods and materialsIris and MLC plans were created for 28 liver, 15 pancreas and 13 prostate cases including a wide range of PTV sizes (24–643 cm³). Plans were compared in terms of coverage, conformity (nCI), dose gradient (R50%), homogeneity (HI), OAR doses, PTV gEUD, MU, treatment time both estimated by TPS (t_TPS) and measured. A global plan quality score index was calculated for IRIS and MLC solutions and validated by a clinical score given independently by two observers.ResultsCompared to Iris, MLC achieved equivalent coverage and conformity without compromising OAR sparing and improving R50% (p < 0.001). MLC gEUD was slightly lower than Iris (p < 0.05) for abdominal cases. MLC reduced significantly MU (−15%) and t_TPS (−22%). Time reduction was partially lost when measured. The global score index was significantly higher for MLC solutions which were selected in 73% and 64% of cases respectively by the first and second observer.ConclusionIris and MLC comparison was not straightforward when based on multiple dosimetric parameters. The use of a mathematical overall score index integrated with a clinical scoring was essential to confirm MLC plans advantages over Iris solutions.     

Analysis of a volumetric-modulated arc therapy (VMAT) single phase prostate template as a class solution

AimTo assess a class solution template for volumetric-modulated arc therapy (VMAT) for prostate cancer using plan analysis software.BackgroundVMAT is a development of intensity-modulated radiotherapy (IMRT) with potential advantages for the delivery of radiotherapy (RT) in prostate cancer. Class solutions are increasingly used for facilitating RT planning. Plan analysis software provides an objective tool for evaluating class solutions.Materials and methodsThe class solution for VMAT was based on the current static field IMRT template. The plans of 77 prostate cancer patients were evaluated using a set of in-house plan quality metrics (scores) (PlanIQ™, Sun Nuclear Corporation). The metrics compared the class solution for VMAT planning with the IMRT template and the delivered clinical plan (CP). Eight metrics were associated with target coverage and ten with organs-at-risk (OAR). Individual metrics were summed and the combined scores were subjected to non-parametric analysis. The low-dose wash for both static IMRT and VMAT plans were evaluated using 40 Gy and 25 Gy isodose volumes.ResultsVMAT plans were of equal or better quality than the IMRT template and CP for target coverage (combined score) and OAR combined score. The 40 Gy isodose volume was marginally higher with VMAT than IMRT (4.9%) but lower than CP (−6.6%)(P = 0.0074). The 25 Gy volume was significantly lower with VMAT than both IMRT (−32.7%) and CP (−34.4%)(P < 0.00001).ConclusionsAutomated VMAT planning for prostate cancer is feasible and the plans are equal to or better than the current IMRT class solution and the delivered clinical plan.     

Evaluation of a commercial automatic treatment planning system for liver stereotactic body radiation therapy treatments

PurposeAutomated treatment planning is a new frontier in radiotherapy. The Auto-Planning module of the Pinnacle³ treatment planning system (TPS) was evaluated for liver stereotactic body radiation therapy treatments.MethodsTen cases were included in the study. Six plans were generated for each case by four medical physics experts. The first two planned with Pinnacle TPS, both with manual module (MP) and Auto-Planning one (AP). The other two physicists generated two plans with Monaco TPS (VM). Treatment plan comparisons were then carried on the various dosimetric parameters of target and organs at risk, monitor units, number of segments, plan complexity metrics and human resource planning time. The user dependency of Auto-Planning was also tested and the plans were evaluated by a trained physician.ResultsStatistically significant differences (Anova test) were observed for spinal cord doses, plan average beam irregularity, number of segments, monitor units and human planning time. The Fisher-Hayter test applied to these parameters showed significant statistical differences between AP e MP for spinal cord doses and human planning time; between MP and VM for monitor units, number of segments and plan irregularity; for all those between AP and VM. The two plans created by different planners with AP were similar to each other.ConclusionsThe plans created with Auto-Planning were comparable to the manually generated plans. The time saved in planning enables the planner to commit more resources to more complex cases. The independence of the planner enables to standardize plan quality.     

Comparison between two treatment planning systems for volumetric modulated arc therapy optimization for prostate cancer

PurposeTo investigate the performances of two commercial treatment planning systems (TPS) for Volumetric Modulated Arc Therapy (VMAT) optimization regarding prostate cancer. The TPS were compared in terms of dose distributions, treatment delivery parameters and quality control results.Materials and methodsFor ten patients, two VMAT plans were generated: one with Monaco TPS (Elekta) and one with Pinnacle TPS (Philips Medical Systems). The total prescribed dose was 78 Gy delivered in one 360° arc with a Synergy^® linear accelerator equipped with a MLCi2^®.ResultsVMAT with Monaco provided better homogeneity and conformity indexes but lower mean dose to PTVs than Pinnacle. For the bladder wall (p = 0.019), the femoral heads (p = 0.017), and healthy tissues (p = 0.005), significantly lower mean doses were found using Monaco. For the rectal wall, VMAT with Pinnacle provided a significantly (p = 0.047) lower mean dose, and lower dose into 50% of the volume (p = 0.047) compared to Monaco. Despite a greater number of monitor units (factor 1.5) for Monaco TPS, the total treatment time was equivalent to that of Pinnacle. The treatment delivery parameter analysis showed larger mean MLC area for Pinnacle and lower mean dose rate compared to Monaco. The quality control results gave a high passing rate (>97.4%) for the gamma index for both TPS but Monaco provided slightly better results.ConclusionFor prostate cancer patients, VMAT treatment plans obtained with Monaco and Pinnacle offered clinically acceptable dose distributions. Further investigations are in progress to confirm the performances of the two TPS for irradiating more complex volumes.     

Monte Carlo dose verification of VMAT treatment plans using Elekta Agility 160-leaf MLC

In this study, we verified volumetric modulated arc therapy (VMAT) plans in an Elekta Synergy system with an integrated Agility 160-leaf multileaf collimator (MLC) by comparing them with Monte Carlo (MC)-calculated dose distributions using the AAPM TG-119 structure sets. The head configuration of the linear accelerator with the integrated MLC was simulated with the EGSnrc/BEAMnrc code. Firstly, the dosimetric properties of the MLC were evaluated with the MC technique and film measurements. Next, VMAT plans were created with the Pinnacle³ treatment planning system (TPS) for four regions in the AAPM TG-119 structures. They were then verified by comparing them with MC-calculated dose distributions using dose volume histograms (DVHs) and three-dimensional (3D) gamma analysis. The MC simulations for the Agility MLC dosimetric properties were in acceptable agreement with measurements. TPS-VMAT plans using TG-119 structure sets agreed with MC dose distributions within 2% in the comparison of D₉₅ in planning target volumes (PTVs) evaluated from DVHs. In contrast, higher dose regions such as D₂₀, D₁₀, and D₅ in PTVs for TPS tended to be smaller than MC values. This tendency was particularly noticeable for mock head and neck with complicated structures. In 3D gamma analysis, the passing rates with 3%/3mm criteria in PTVs were ≥99%, except for mock head and neck (89.5%). All passing rates for organs at risk (OARs) were in acceptable agreement of >96%. It is useful to verify dose distributions of PTVs and OARs in TPS-VMAT plans by using MC dose calculations and 3D gamma analysis.     

Dosimetric comparison of dynamic conformal arc integrated with segment shape optimization and variable dose rate versus volumetric modulated arc therapy for liver SBRT

AimThe aim is a dosimetric comparison of dynamic conformal arc integrated with the segment shape optimization and variable dose rate (DCA_SSO_VDR) versus VMAT for liver SBRT and interaction of various treatment plan quality indices with PTV and degree of modulation (DoM) for both techniques.BackgroundThe DCA is the state-of-the-art technique but overall inferior to VMAT, and the DCA_SSO_VDR technique was not studied for liver SBRT.Materials and methodsTwenty-five patients of liver SBRT treated using the VMAT technique were selected. DCA_SSO_VDR treatment plans were also generated for all patients in Monaco TPS using the same objective constraint template and treatment planning parameters as used for the VMAT technique. For comparison purpose, organs at risk (OARs) doses and treatment plans quality indices, such as maximum dose of PTV (D_max%), mean dose of PTV (D_mean%), maximum dose at 2 cm in any direction from the PTV (D_2cm%), total monitor units (MU’s), gradient index R_50%, degree of modulation (DoM), conformity index (CI), homogeneity index (HI), and healthy tissue mean dose (HTMD) were compared.ResultsSignificant dosimetric differences were observed in several OARs doses and lowered in VMAT plans. The D_2cm%, R_50%, CI, HI and HTMD are dosimetrically inferior in DCA_SSO_VDR plans. The higher DoM results in poor dose gradient and better dose gradient for DCA_SSO_VDR and VMAT treatment plans, respectively.ConclusionsFor liver SBRT, DCA_SSO_VDR treatment plans are neither dosimetrically superior nor better alternative to the VMAT delivery technique. A reduction of 69.75% MU was observed in DCA_SSO_VDR treatment plans. For the large size of PTV and high DoM, DCA_SSO_VDR treatment plans result in poorer quality.     

Reducing inter- and intra-planner variability in radiotherapy plan output with a commercial knowledge-based planning solution

PurposeThis study measured to which extent RapidPlan can drive a reduction of the human-caused variability in prostate cancer treatment planning.MethodsSeventy clinical prostate plans were used to train a RapidPlan model. Seven planners, with different levels of planning experience, were asked to plan a VMAT treatment for fifteen prostate cancer patients with and without RapidPlan assistance. The plans were compared on the basis of target coverage, conformance and OAR sparing. Inter-planner and intra-planner variability were assessed on the basis of the Plan Quality Metric formalism. Differences in mean values and InterQuartile Ranges between patients and operators were assessed.ResultsRapidPlan-assisted plans matched manual planning in terms of target coverage, homogeneity, conformance and bladder sparing but outperformed it for rectum and femoral heads sparing. 8 out of 15 patients showed a statistically significant increase in overall quality. Inter-planner variability is reduced in RapidPlan-assisted planning for rectum and femoral heads while bladder variability was constant. The inter-planner variability of the overall plan quality, IQR of PQM%, was approximately halved for all patients. RapidPlan assistance induced a larger increase in plan quality for less experienced planners. At the same time, a reduction in intra-planner variability is measured with a significant overall reduction.ConclusionsThe assistance of RapidPlan during the optimization of treatments for prostate cancer induces a significant increase of plan quality and a contextual reduction of plan variability. RapidPlan is proven to be a valuable tool to leverage the planning skills of less experienced planners ensuring a better homogeneity of treatment plan quality.     

Dose-escalated volumetric modulated arc therapy for total marrow irradiation: A feasibility dosimetric study with 4DCT planning and simultaneous integrated boost

PurposeTo evaluate the planning feasibility of dose-escalated total marrow irradiation (TMI) with simultaneous integrated boost (SIB) to the active bone marrow (ABM) using volumetric modulated arc therapy (VMAT), and to assess the impact of using planning organs at risk (OAR) volumes (PRV) accounting for breathing motion in the optimization.MethodsFive patients underwent whole-body CT and thoraco-abdominal 4DCT. A planning target volume (PTV) including all bones and ABM was contoured on each whole-body CT. PRV of selected OAR (liver, heart, kidneys, lungs, spleen, stomach) were determined with 4DCT. Planning consisted of 9–10 full 6 MV photon VMAT arcs. Four plans were created for each patient with 12 Gy prescribed to the PTV, with or without an additional 4 Gy SIB to the ABM. Planning dose constraints were set on the OAR or on the PRV. Planning objective was a PTV D_mean < 110% of the prescribed dose, a PTV V_110% < 50%, and OAR D_mean ≤ 50–60%.ResultsPTV D_mean < 110% was accomplished for most plans (n = 18/20), while all achieved V_110%<50%. SIB plans succeeded to optimally cover the boost volume (median ABM D_mean = 16.3 Gy) and resulted in similar OAR sparing compared to plans without SIB (median OAR D_mean = 40–54% of the ABM prescribed dose). No statistically significant differences between plans optimized with constraints on OAR or PRV were found.ConclusionsAdding a 4 Gy SIB to the ABM for TMI is feasible with VMAT technique, and results in OAR sparing similar to plans without SIB. Setting dose constraints on PRV does not impair PTV dosimetric parameters.     

Commissioning and clinical implementation of Mobius3D and MobiusFX: Experience on multiple linear accelerators

PurposeTo provide practical guidelines for Mobius3D commissioning based on experiences of commissioning/clinical implementation of Mobius3D and MobiusFX as patient-specific quality assurance tools on multiple linear accelerators.MethodsThe vendor-suggested Mobius3D commissioning procedures, including beam model adjustment and dosimetric leaf gap (DLG) optimization, were performed for 6 MV X-ray beams of six Elekta linear accelerators. For the beam model adjustment, beam data, such as the percentage depth dose, off-axis ratio (OAR), and output factor (OF), were measured using a water phantom and compared to the vendor-provided reference values. DLG optimization was performed to determine an optimal DLG correction factor to minimize the mean difference between Mobius3D-calculated and measured doses for multiple volumetric modulated arc therapy (VMAT) plans. Small-field VMAT plans, in which Mobius3D has dose calculate uncertainties, were initially included in the DLG optimization, but excluded later.ResultsThe measured beam data were consistent across the six linear accelerators. Relatively large differences between the reference and measured values were observed for the OAR at large off-axis distances (>5 cm) and for the OF for small fields (<3 × 3 cm²). The optimal DLG correction factor was 0.6 ± 0.3 (range: 0.3–1.0) with small-field plans and 0.2 ± 0.2 (0.0–0.5) without them.ConclusionsA reasonable agreement was found between the vendor-provided reference and measured beam models. DLG optimization results were dependent on the selection of the VMAT plans, requiring careful attention to the known dose calculation uncertainties of Mobius3D when determining a DLG correction factor.     

Dosimetric impact of statistical uncertainty on Monte Carlo dose calculation algorithm in volumetric modulated arc therapy using Monaco TPS for three different clinical cases

AimTo study the dosimetric impact of statistical uncertainty (SU) per plan on Monte Carlo (MC) calculation in Monaco? treatment planning system (TPS) during volumetric modulated arc therapy (VMAT) for three different clinical cases.BackgroundDuring MC calculation SU is an important factor to decide dose calculation accuracy and calculation time. It is necessary to evaluate optimal acceptance of SU for quality plan with reduced calculation time.Materials and methodsThree different clinical cases as the lung, larynx, and prostate treated using VMAT technique were chosen. Plans were generated with Monaco? V5.11 TPS with 2% statistical uncertainty. By keeping all other parameters constant, plans were recalculated by varying SU, 0.5%, 1%, 2%, 3%, 4%, and 5%. For plan evaluation, conformity index (CI), homogeneity index (HI), dose coverage to PTV, organ at risk (OAR) dose, normal tissue receiving dose ≥5 Gy and ≥10 Gy, integral dose (NTID), calculation time, gamma pass rate, calculation reproducibility and energy dependency were analyzed.ResultsCI and HI improve as SU increases from 0.5% to 5%. No significant dose difference was observed in dose coverage to PTV, OAR doses, normal tissue receiving dose ≥5 Gy and ≥10 Gy and NTID. Increase of SU showed decrease in calculation time, gamma pass rate and increase in PTV max dose. No dose difference was seen in calculation reproducibility and dependent on energy.ConclusionFor VMAT plans, SU can be accepted from 1% to 3% per plan with reduced calculation time without compromising plan quality and deliverability by accepting variations in point dose within the target.     

Flattening Filter-Free Beams in Intensity-Modulated Radiotherapy and Volumetric Modulated Arc Therapy for Sinonasal Cancer

Purpose

To evaluate the dosimetric impacts of flattening filter-free (FFF) beams in intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) for sinonasal cancer.

Methods

For fourteen cases, IMRT and VMAT planning was performed using 6-MV photon beams with both conventional flattened and FFF modes. The four types of plans were compared in terms of target dose homogeneity and conformity, organ-at-risk (OAR) sparing, number of monitor units (MUs) per fraction, treatment time and pure beam-on time.

Results

FFF beams led to comparable target dose homogeneity, conformity, increased number of MUs and lower doses to the spinal cord, brainstem and normal tissue, compared with flattened beams in both IMRT and VMAT. FFF beams in IMRT resulted in improvements by up to 5.4% for sparing of the contralateral optic structures, with shortened treatment time by 9.5%. However, FFF beams provided comparable overall OAR sparing and treatment time in VMAT. With FFF mode, VMAT yielded inferior homogeneity and superior conformity compared with IMRT, with comparable overall OAR sparing and significantly shorter treatment time.

Conclusions

Using FFF beams in IMRT and VMAT is feasible for the treatment of sinonasal cancer. Our results suggest that the delivery mode of FFF beams may play an encouraging role with better sparing of contralateral optic OARs and treatment efficiency in IMRT, but yield comparable results in VMAT.     

Delta4 Discover transmission detector: A comprehensive characterization for in-vivo VMAT monitoring

ObjectiveTo investigate the dosimetric behaviour, influence on photon beam fluence and error detection capability of Delta⁴ Discover transmission detector.MethodsThe transmission detector (TRD) was characterized on a TrueBeam linear accelerator with 6 MV beams. Linearity, reproducibility and dose rate dependence were investigated. The effect on photon beam fluence was evaluated in terms of beam profiles, percentage depth dose, transmission factor and surface dose for different open field sizes. The transmission factor of the 10x10 cm² field was entered in the TPS’s configuration and its correct use in the dose calculation was verified recalculating 17 clinical IMRT/VMAT plans. Surface dose was measured for 20 IMRT fields. The capability to detect different delivery errors was investigated evaluating dose gamma index, MLC gamma index and leaf position of 15 manually modified VMAT plans.ResultsTRD showed a linear dependence on MU. No dose rate dependence was observed. Short-term and long-term reproducibility were within 0.1% and 0.5%. The presence of the TRD did not significantly affect PDDs and profiles. The transmission factor of the 10x10 cm² field size was 0.985 and 0.983, for FF and FFF beams respectively. The 17 recalculated plans met our clinical gamma-index passing rate, confirming the correct use of the transmission factor by the TPS. The surface dose differences for the open fields increase for shorter SSDs and greater field size. Differences in surface dose for the IMRT beams were less than 2%. Output variation ≥2%, collimator angle variations within 0.3°, gantry angle errors of 1°, jaw tracking and leaf position errors were detected.ConclusionsDelta⁴ Discover shows good linearity and reproducibility, is not dependent on dose rate and does not affect beam quality and dose profiles. It is also capable to detect dosimetric and geometric errors and therefore it is suitable for monitoring VMAT delivery.     

Dosimetric effect of limited aperture multileaf collimator on VMAT plan quality: A study of prostate and head-and-neck cancers

Aim

The aim of study was to evaluate the dosimetric effect of collimator-rotation on VMAT plan quality, when using limited aperture multileaf collimator of Elekta Beam Modulator? providing a maximum aperture of 21 cm × 16 cm.

Critical Structure Sparing in Stereotactic Ablative Radiotherapy for Central Lung Lesions: Helical Tomotherapy vs. Volumetric Modulated Arc Therapy

Background

Helical tomotherapy (HT) and volumetric modulated arc therapy (VMAT) are both advanced techniques of delivering intensity-modulated radiotherapy (IMRT). Here, we conduct a study to compare HT and partial-arc VMAT in their ability to spare organs at risk (OARs) when stereotactic ablative radiotherapy (SABR) is delivered to treat centrally located early stage non-small-cell lung cancer or lung metastases.

Methods

12 patients with centrally located lung lesions were randomly chosen. HT, 2 & 8 arc (Smart Arc, Pinnacle v9.0) plans were generated to deliver 70 Gy in 10 fractions to the planning target volume (PTV). Target and OAR dose parameters were compared. Each technique’s ability to meet dose constraints was further investigated.

Results

HT and VMAT plans generated essentially equivalent PTV coverage and dose conformality indices, while a trend for improved dose homogeneity by increasing from 2 to 8 arcs was observed with VMAT. Increasing the number of arcs with VMAT also led to some improvement in OAR sparing. After normalizing to OAR dose constraints, HT was found to be superior to 2 or 8-arc VMAT for optimal OAR sparing (meeting all the dose constraints) (p = 0.0004). All dose constraints were met in HT plans. Increasing from 2 to 8 arcs could not help achieve optimal OAR sparing for 4 patients. 2/4 of them had 3 immediately adjacent structures.

Conclusion

HT appears to be superior to VMAT in OAR sparing mainly in cases which require conformal dose avoidance of multiple immediately adjacent OARs. For such cases, increasing the number of arcs in VMAT cannot significantly improve OAR sparing.     

Is IMAT the ultimate evolution of conformal radiotherapy? Dosimetric comparison of helical tomotherapy and volumetric modulated arc therapy for oropharyngeal cancer in a planning study

BackgroundIntensity Modulated Arc Therapy (IMAT) can be planned and delivered via several techniques. Advanced Radiotherapy (ARTORL) is a prospective study that aims to evaluate the treatment costs and clinical aspects of implementing these IMAT techniques for head and neck cancers. In this context, we evaluated the potential dosimetric gain of Helical Tomotherapy (TomoTherapy, Accuray, HT) versus VMAT (Rapid'Arc^®, Varian Medical System, RA) for oropharyngeal cancer (OC).Material and methodsThirty patients were selected from our database in whom bilateral neck irradiation and treatment to the primary were indicated. Each patient was planned twice using both HT and RA planning systems using a simultaneous integrated boost approach. For the planning target volumes (PTV) and organs at risk, ICRU 83 reporting guidelines were followed. RA and HT plans were compared using paired Student's t-test.ResultsRA and HT produced plans with a good coverage of PTVs and acceptable sparing of OARs. Although some dosimetric differences were statistically significant, they remained small. However, the near maximal dose to the PRV of spinal cord and brain stem was lower with HT. Regarding normal tissue, HT increased the volume irradiated at doses between 4 and 20 Gy compared to RA.ConclusionIn OC, HT and RA showed similar dosimetric results. They represent the maximum gains obtained with photon beams. The medicoeconomic evaluation of our study is ongoing and may reveal differences between these techniques in terms of MU number, fraction time, and clinical evaluation.     

Dosimetric comparison of normal breathing and deep inspiration breath hold technique for synchronous bilateral breast cancer using 6MV flattened beam and flattening filter free beam

BackgroundThe present study was to investigate the usefulness of deep inspiration breath hold (DIBH) in bilateral breast patients using 6MV flattened beam (FB) and flattening filter free beam (FFFB).Materials and methodsTwenty bilateral breast cancer patients were simulated, using left breast patients treated with DIBH technique. CT scans were performed in the normal breathing (NB) and DIBH method. Three-dimensional conformal radiotherapy (3DCRT) and volumetric arc therapy (VMAT) plans were generated.ResultsIn our study the best organ at risk (OAR) sparing is achieved in the 3DCRT DIBH plan with adequate PTV coverage (V₉₅ ≥ 47.5 Gy) as compared to 6MV FB and FFFB VMAT DIBH plans. The DIBH scan plan reduces the heart mean dose significantly at the rate of 49% in 3DCRT (p = 0.00) and 22% in VMAT (p = 0.010). Similarly, the DIBH scan plan produces lesser common lung mean dose of 18% in 3DCRT (p = 0.011) and 8% in VMAT (0.007) as compared to the NB scan. The conformity index is much better in VMAT FB (1.04 ± 0.04 vs. 1.04 ± 0.05), p =1.00 and VMAT FFFB (1.04 ± 0.05 vs. 1 ± 0.24, p = 0.345) plans as compared to 3DCRT (1.63 ± 0.2 vs. 1.47 ± 0.28, p = 0.002). The homogeneity index of all the plans is less than 0.15. The global dmax is more in VMAT FFFB DIBH plan (113.7%). The maximum MU noted in the NB scan plan (478 vs. 477MU, 1366 vs. 1299 MU and 1853 vs. 1788 MU for 3DCRT, VMAT FB and VMAT FFFB technique as compared to DIBH scan.ConclusionWe recommend that the use of DIBH techniques for bilateral breast cancer patients significantly reduces the radiation doses to OARs in both 3DCRT and VMAT plans.     

Integrated scoring approach to assess radiotherapy plan quality for breast cancer treatment

BackgroundProposal of an integrated scoring approach assessing the quality of different treatment techniques in a radiotherapy planning comparison. This scoring method incorporates all dosimetric indices of planning target volumes (PTVs) as well as organs at risk (OARs) and provides a single quantitative measure to select an ideal plan.Materials and methodsThe radiotherapy planning techniques compared were field-in-field (FinF), intensity modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), hybrid IMRT (H-IMRT), and hybrid VMAT (H-VMAT). These plans were generated for twenty-five locally advanced left-sided breast cancer patients. The PTVs were prescribed a hypofractionation dose of 40.5 Gy in 15 fractions. The integrated score for each planning technique was calculated using the proposed formula.ResultsAn integrated score value that is close to zero indicates a superior plan. The integrated score that incorporates all dosimetric indices (PTVs and OARs) were 1.37, 1.64, 1.72, 1.18, and 1.24 for FinF, IMRT, VMAT, H-IMRT, and H-VMAT plans, respectively.ConclusionThe proposed integrated scoring approach is scientific to select a better plan and flexible to incorporate the patient-specific clinical demands. This simple tool is useful to quantify the treatment techniques and able to differentiate the acceptable and unacceptable plans.