Field-in-field Research Articles

Comparison of skin doses of treated and contralateral breasts during whole breast radiotherapy for different treatment techniques using optically stimulated luminescent dosimeters

AbstractPurpose:To measure and compare the skin doses received by treated left breast and contralateral breast (CB) during whole breast radiotherapy using five treatment techniques in an indigenously prepared wax breast phantom.Materials and methods:Computed tomography (CT) images of the breast phantom were used for treatment planning and comparison of skin dose calculated from treatment planning system (TPS) with measured dose. Planning target volume (PTV) and the CB were drawn arbitrarily on the CT images acquired for the breast phantom with 10 numbers of calibrated optically stimulated luminescent dosimeters (OSLDs) fixed on the surface of both breasts. The TPS calculated surface doses of PTV breast and CB for five treatment planning techniques, viz., conventional wedge (CW), irregular surface compensator-based (ISC), field-in-field (FiF), intensity-modulated radiotherapy (IMRT) and rapid arc (RA) techniques were obtained for comparison. The plans were executed in Clinac iX Linear Accelerator with the OSLDs fixed at the same locations on the phantom as in simulation. The TPS calculated mean dose at the surface of the treated left breast and CB was noted for the 10 OSLDs from dose-volume histogram (DVH) and compared with the measured dose. Also, the mean chamber dose at the centre of the left breast was noted from the DVH for comparing with ion chamber measured dose.Results:With reference to the results, it is seen that the dose to the CB is lowest in ISC technique and FiF technique and greatest in IMRT technique. The CW technique also delivered a dose comparable to IMRT to the CB of the phantom. The dose to the surface of PTV breast was highest and comparable in CW plans and FiF plans (68% and 67%) and lowest in IMRT and RA plans (50% each).Findings:Analysis of the results shows that the FiF and ISC techniques are preferred while planning breast radiotherapy due to the reduced dose to the CB.

Hypofractionated Whole Breast Radiotherapy with Simultaneous Integrated Boost Following Breast Conservative Surgery for Early Breast Cancer

Background: Hypofractionated whole breast radiotherapy (HFWBRT) showed comparable efficacy and safety to conventional fractionated radiotherapy. Dose and fractionation of the tumor bed boost to be integrated during HF-WBRT schedules is still to be determined. Aim: to investigate the clinical feasibility of HF-WBRT with simultaneous integrated boost (SIB), in early breast cancer patients who underwent breast conserving surgery (BCS). Methods: This single arm prospective study included 40 female patients with pathologically proven stage I-II breast cancer following BCS with high risk factors. Patients received 3D conformal radiotherapy (3DCRT) with field in field (FIF) technique. The whole breast received a dose of 40 gray (Gy) over 15 fractions for 3 weeks with an additional SIB dose of 8 Gy over 15 fractions to be give daily during WBRT. Radiation toxicities were graded using the common terminology criteria for adverse events (NCI-CTCAE) scale version 4.03. Cosmetic outcome was assessed using Harvard cosmetic score. Kaplan Meier method was used to estimate the 3- year disease free (DFS) and overall survival (OS). Results: The median age at presentation was 48 years (range 33-68). No reported grade 3 or 4 toxicities. Grade 1 and 2 radiation dermatitis affected 80% of the patients, breast pain was observed in 62.5% of the patients while 25% had radiation pneumonitis. Most of the patients (95%) had excellent and good cosmetic outcomes. At 3 years the estimated DFS was 95% and OS was 97.5 %. Conclusion: WBRT-SIB using 3DCRT with FIF technique is clinically feasible for early stage breast cancer patients.

Tibialis Anterior Tendon Transfer for Correction of Residual Dynamic Supination of Clubfoot Treated with Ponseti Technique

Background: Hypofractionated whole breast radiotherapy (HF-WBRT) showed comparable efficacy and safety to conventional fractionated radiotherapy. Dose and fractionation of the tumor bed boost to be integrated during HF-WBRT schedules is still to be determined. Aim: to investigate the clinical feasibility of HF-WBRT with simultaneous integrated boost (SIB), in early breast cancer patients who underwent breast conserving surgery (BCS). Methods: This single arm prospective study included 40 female patients with pathologically proven stage I-II breast cancer following BCS with high risk factors. Patients received 3D conformal radiotherapy (3DCRT) with field in field (FIF) technique. The whole breast received a dose of 40 gray (Gy) over 15 fractions for 3 weeks with an additional SIB dose of 8 Gy over 15 fractions to be give daily during WBRT. Radiation toxicities were graded using the common terminology criteria for adverse events (NCI-CTCAE) scale version 4.03. Cosmetic outcome was assessed using Harvard cosmetic score. Kaplan Meier method was used to estimate the 3- year disease free (DFS) and overall survival (OS). Results: The median age at presentation was 48 years (range 33-68). No reported grade 3 or 4 toxicities. Grade 1 and 2 radiation dermatitis affected 80% of the patients, breast pain was observed in 62.5% of the patients while 25% had radiation pneumonitis. Most of the patients (95%) had excellent and good cosmetic outcomes. At 3 years the estimated DFS was 95% and OS was 97.5 %. Conclusion: WBRT-SIB using 3DCRT with FIF technique is clinically feasible for early stage breast cancer patients.

Comparison of conventional and advanced radiotherapy techniques for left-sided breast cancer after breast conserving surgery

Whole breast radiotherapy (WBRT) after breast conserving surgery is the standard treatment to prevent recurrence and metastasis of early stage breast cancer. This study aims to compare seven WBRT techniques including conventional tangential, field-in-field (FIF), hybrid intensity-modulated radiotherapy (IMRT), IMRT, standard volumetric modulated arc therapy (STD-VMAT), noncoplanar VMAT (NC-VMAT), and multiple arc VMAT (MA-VMAT). Fifteen patients who were previously diagnosed with left-sided early stage breast cancer and treated in our clinic were selected for this study. WBRT plans were created for these patients and were evaluated based on target coverage and normal tissue toxicities. All techniques produced clinically acceptable WBRT plans. STD-VMAT delivered the lowest mean dose (1.1 ± 0.3 Gy) and the lowest maximum dose (7.3 ± 4.9 Gy) to contralateral breast, and the second lowest lifetime attributable risk (LAR) (4.1 ± 1.4%) of secondary contralateral breast cancer. MA-VMAT delivered the lowest mean dose to lungs (4.9 ± 0.9 Gy) and heart (5.5 ± 1.2 Gy), exhibited the lowest LAR (1.7 ± 0.3%) of secondary lung cancer, normal tissue complication probability (NTCP) (1.2 ± 0.2%) of pneumonitis, risk of coronary events (RCE) (10.3 ± 2.7%), and LAR (3.9 ± 1.3%) of secondary contralateral breast cancer. NC-VMAT plans provided the most conformal target coverage, the lowest maximum lung dose (46.2 ± 4.1 Gy) and heart dose (41.1 ± 5.4 Gy), and the second lowest LAR (1.8 ± 0.4%) of secondary lung cancer and RCE (10.5 ± 2.8%). MA-VMAT and NC-VMAT could be the preferred techniques for early stage breast cancer patients after breast conserving surgery.

Benefits and Limitations of Volumetric Modulated Arc Therapy in Treating Bilateral Breast Cancer with Regional Lymph Nodes

Purpose: The study was performed comparing dosimetric characteristics of volumetric modulated arc therapy (VMAT) and field-in-field (FiF) techniques on a patient with synchronous bilateral breast carcinoma. Methods: The patients with bilateral breast cancer treatment were included in this study. A total dose of 40.05 Gy in 15 fractions was prescribed to the Planning Target Volume (PTV) of the whole bilateral breast cancer with the supraclavicular and infraclavicular nodes, with a complementary boost of 10 Gy in 4 fractions to the surgical bed (PTVboost). For both radiotherapy techniques, several VxGy parameters were analyzed for the PTVs, together with the Conformity index (CI), the Homogeneity index (HI) and the critical organs at risk (OARs), lungs and heart. Results: The patient was treated by the VMAT technique and the daily treatment time was less than 20 minutes with daily CBCT imaging. In the VMAT plan, the PTV 95% dose covered 38.89 ± 0.81 Gy, compared to 37.26 ± 1.02 Gy in the FiF technique. The VMAT plan improved the dose homogeneity index and lower dose in lung towards high dose region. Conclusion: The study demonstrates the viability of the VMAT technique in the treatment of bilateral breast cancer. The introduced single isocentric VMAT technique is fast to deliver and it increases the dose homogeneity of the target volume with some limitations. The treatment was well tolerated, without interruption of the treatment courses caused by treatment-related toxicities.

Optimization of autogenerated chest-wall radiation treatment plans developed for postmastectomy breast cancer patients in underserved clinics

Over the past decade, several strides have been made to improve the management of breast cancer in developing countries; however, there are still obstacles present. In the area of radiation therapy, these hurdles include limited access to radiotherapy treatment and scarcity of oncology specialists. In an effort to reduce inequities in cancer care while improving patient outcomes, our research is focused on developing automated postmastectomy radiation therapy (PMRT) plans for breast cancer patients in these underserved communities that can be further improved upon through treatment planning system (TPS) specific optimization guidelines. The automated planning tool utilized algorithms integrated with Varian's Eclipse TPS. The tool created PMRT plans that used monoisocentric tangents and supraclavicular (SCV) fields with a mix of high and low energy photon beams along with field-in-field (FIF) segments. The completed autogenerated PMRT plans were imported into Phillip's Pinnacle 9.10 and Varian's Eclipse 13.6 TPSs to be further improved through manual optimization; the time required to complete this step was measured and assessed. A senior dosimetrist, physicist, and physician evaluated the optimized plans for clinical acceptability. Guidelines were developed for the planning systems that can be implemented by personnel with either limited experience in radiation treatment planning or those with limited time to produce treatment plans. The autogenerated plans in conjunction with our guidelines have shown to significantly reduce the time required to produce a clinically acceptable PMRT plan from approximately 120 ± 60 minutes to just 13 ± 11 (Pinnacle) and 12 ± 7 (Eclipse) minutes, reducing the total uninterrupted treatment planning time by an average of 108 ± 51 minutes. The results from this research indicate that the autogenerated PMRT plans along with the optimization guidelines are a viable option to provide quality and clinically acceptable PMRT plans that are more efficient and consistent for postmastectomy breast cancer patients in severely underserved communities.

Field-in-field breast planning for a jawless, double-stack MLC LINAC using flattening-filter-free beams.

BackgroundThis study intends to develop an efficient field‐in‐field (FiF) planning technique with the Eclipse treatment planning system (TPS) to determine the feasibility of using the Halcyon treatment delivery system for 3D treatment of breast cancer.MethodsTen treatment plans were prepared on the Halcyon treatment planning system and compared to the same patients’ clinically delivered TrueBeam plans which used flattened 6 MV and 10 MV beams. Patients selected for this study were treated via simple, tangential breast irradiation and did not receive radiotherapy of the supraclavicular or internal mammary lymph nodes. Planning target volumes (PTV) volumes ranged from 519 cc to 1211 cc with a mean target volume of 877 cc. Several planning techniques involving collimator, gantry rotation, and number of FiF segments were investigated as well as the use of the dynamically flattened beam (DFB) — a predefined MLC pattern that is designed to provide a flattened beam profile at 10 cm depth on a standard water phantom. For comparison, the clinically delivered TrueBeam plans remained unaltered except for normalization of the target coverage to more readily compare the two treatment delivery techniques.ResultsUsing the physician defined PTV, normalized such that 98% of the volume was covered by 95% of the prescribed dose, the Halcyon plans were deemed clinically acceptable and comparable to the TrueBeam plans by the radiation oncologist. Resulting average global maximum doses in the test patients were identical between the TrueBeam and Halcyon plans (108% of Rx) and a mean PTV dose of 102.5% vs 101.6%, respectively.ConclusionsFrom this study a practical and efficient planning method for delivering 3D conformal breast radiotherapy using the Halcyon linear accelerator has been developed. When normalized to the clinically desired coverage, hot spots were maintained to acceptable levels and overall plan quality was comparable to plans delivered on conventional C‐arm LINACs.

Correlation of hot spot to breast separation in patients treated with postlumpectomy tangent 3D-CRT using field-in-field technique and mixed photon energies

Radiotherapy to an intact breast was previously determined to have a positive correlation between breast separation measurement and hot spot dose. As breast separation measurement increased, hot spot dose increased. The purpose of this retrospective study was to determine if this correlation persisted despite current techniques including field-in-field (FiF) blocking and mixed photon energies. Radiation treatment plans on unilateral intact breasts from 90 female, early stage breast cancer patients treated with lumpectomy were analyzed. Plans were created using 3-dimensional conformal radiation therapy (3D-CRT) nondivergent opposing tangent beams, FiF technique, and 6 MV with or without higher energy photons. Data collected included breast separation measurement, hot spot point dose and location, number of beams, photon energy, clinical target volume (CTV) coverage and breast volume coverage. Correlations between breast separation measurement and each of these values were determined. The positive correlation between breast separation measurement and hot spot dose persisted despite incorporating FiF and mixed photon energies. Correlations were also found between breast separation and the number of beams as well as breast separation and photon energy. Larger breast separations tended to be treated with additional beams of higher photon energy. There were no correlations found between breast separation and CTV or breast volume coverage. The data in this study suggested the medical dosimetrist should expect hot spots above prescription dose of 106%, 107%, and 108% for small, medium and large breast separation sizes respectively. Additionally, adding a high energy photon bean may be indicated with medium and large breast separations.

Effect of dose constraint on the thyroid gland during locoregional intensity-modulated radiotherapy in breast cancer patients.

The aim of the present study was to compare radiation dose received by thyroid gland using different radiotherapy (RT) techniques with or without thyroid dose constraint (DC) for breast cancer patients. Computerized tomography (CT) image sets for 10 patients with breast cancer were selected. All patients were treated originally with opposite tangential field‐in field (FinF) for the chest wall and anteroposterior fields for the ipsilateral supraclavicular field. The thyroid gland was not contoured on the CT images at the time of the original scheduled treatment. Four new treatment plans were created for each patient, including intensity‐modulated radiotherapy (IMRT) and helical tomotherapy (HT) plans with thyroid DC exclusion and inclusion (IMRTDC(−), IMRTDC(+), HTDC(−), and HTDC(+), respectively). Thyroid DCs were used to create acceptable dose limits to avoid hypothyroidism as follows: percentage of thyroid volume exceeding 30 Gy less than 50% (V 30 < 50%) and mean dose of thyroid (TDmean) ≤ 21 Gy. Dose‐volume histograms (DVHs) for TDmean and percentages of thyroid volume exceeding 10, 20, 30, 40, and 50 Gy (V 10, V 20, V 30, V 40, and V 50, respectively) were also analyzed. The Dmean of the FinF, IMRTDC(−), HTDC(−), IMRTDC(+) and HTDC(+) plans were 30.56 ± 5.38 Gy, 25.56 ± 6.66 Gy, 27.48 ± 4.16 Gy, 18.57 ± 2.14 Gy, and 17.34 ± 2.70 Gy, respectively. Median V30 values were 55%, 33%, 36%, 18%, and 17%, for FinF, IMRTDC(−), HTDC(−), IMRTDC(+), and HTDC(+), respectively. Differences between treatment plans with or without DC with respect to D mean and V 30 values were statistically significant (P < 0.05). When thyroid DC during breast cancer RT was applied to IMRT and HT, the TDmean and V 30 values significantly decreased. Therefore, recognition of the thyroid as an organ at risk (OAR) and the use of DCs during IMRT and HT planning to minimize radiation dose and thyroid volume exposure are recommended.

Feasibility study of conformal forward planned simultaneous integrated boost technique comparable to IMRT and VMAT in pelvic irradiation for locally advanced cervical cancer

Abstract Aim: To check the feasibility of simultaneous integrated boost (SIB) using a forward planned field in field (FIF) conformal technique for the treatment of carcinoma of the cervix IIIB and compare it dosimetrically with other advanced inverse planning techniques. Methods: In our study 33 patients of carcinoma of the cervix IIIB were planned for SIB using conformal FIF technique and they were compared with retrospectively planned IMRT and VMAT techniques. SIB using conformal FIF was planned by two different methods. Results: The results of our study indicate that forward planned Conformal SIB techniques are comparable with inverse planned techniques dosimetrically, in terms of conformity Index, Homogeneity Index, Maximum dose, etc. The ability of FIF SIB plans to produce dose contrast in differential dose accumulation was compared and analyzed and the results were encouraging. To treat an advanced/bulky disease like Carcinoma of the Cervix IIIB in centers with large patient load, utilizing advanced techniques such as IMRT and VMAT is both technically and practically difficult. Despite VMAT’s shorter delivery time, the procedures involved are time-consuming. Conclusion: Hence forward planned SIB techniques may be used to achieve similar dosimetric effects of IMRT and VMAT techniques without much compromise in plan quality and patient throughput for treating bulky carcinoma of the cervix IIIB cases. However, the clinical results need to be carefully compared and evaluated and reported.

Comparison of Dosimetric Parameters Between Field in Field and Conformal Radiation Therapy Techniques in Early Stage of Left Breast Cancer Patients

Background: Breast cancer is the most prevalent cancer in women all over the world. The most common and effective treatment for the early stage of breast cancer patients is breast conserving surgery (BCS) followed by radiotherapy. Objectives: The aim of this study is to evaluate and compare the dosimetric parameters of three-dimensional conformal radiation therapy (3D-CRT), using virtual wedge and field in field (FIF) techniques for patients having left breast cancer in early stages. Methods: Twenty-four patients with left breast cancer participated in this study. They were divided into thr3ee categories (small, medium, and large) based on breast volume: ≤ 1500 cc small, 1500 - 2000 cc medium, and > 2000 cc large. Two treatment planning techniques were generated for each patient by prowess treatment planning system. The following parameters were compared: Maximum, minimum, and mean dose in planning target volume (PTV), homogeneity (HI) and conformity indexes (CI), percentage of volume receiving greater than 107% of the prescribed dose (hot spots) and less than 95% of the prescribed dose (cold spots), and total monitor unit (MU) and doses received to organs at risks (OARs) such as heart and left lung. The mean values were compared using student’s t-test. Results: The FIF technique reduced either the maximum dose in PTV or hot spots in all groups significantly (P 0.05). Conclusions: It is recommended that two techniques can be combined and used together to cover their weak points. Also, it seems that if there is no equipment of intensity modulated radiation therapy (IMRT) techniques such as FIF in some centers, conformal technique by using virtual wedge is a proper alternative.

Usefulness of EZFluence software for radiotherapy planning of breast cancer treatment

This study compared the EZFluence planning technique for irradiation of the breast with commonly used Field-in-Field (FiF) technique by analyzing the dose uniformity, the dose to the lung, heart, and other organs at risk, the total Monitor Unit (MU), and the time spent for planning. Two different 3-dimensional conformal dose plans were created for 20 breast cancer patients. Six patients were treated to a dose of 5000 cGy in 25 fractions and 14 were treated to a dose of 4256 cGy in 16 fractions. Average breast volume was 800 cc (range 128 to 1892 cc). For the FiF technique, the planner manually created between 2 to 4 subfields per gantry angle and sequentially blocked the 115% and 110% isodose line until a homogenous dose distribution was achieved. For the EZFluence technique, the planner implemented the EZFluence script that created an optimal fluence pattern, which was then imported into Eclipse where dose was calculated. Both techniques were optimized to make sure 95% of the breast planning target volume (PTV) received at least 95% of the prescribed dose. Compared to FiF technique, the plans produced by using EZFluence technique, showed the MU increased by 36.9% (p = 0.0002), whereas the planning time decreased significantly by 84.6% (p = 0.00001). The mean heart dose and the relative volume of the heart receiving ≥ 30 Gy (V30) were similar for both techniques. The mean lung dose and the relative volume of lung receiving ≥ 20 Gy (V20) were also comparable between 2 techniques. The contralateral breast mean dose and its relative volume receiving ≥ 3 Gy (V3) and ≥10 Gy (V10) were equally spared and avoided. EZFluence planning technique yielded a 4.6% (p = 0.04) reduction in PTV receiving 105% of the prescribed dose (V105) for the large breast with separation > 22 cm and PTV volume > 650 cc. The EZFluence planning technique yielded the overall comparable or improved dosimetry while significantly reducing planning time.

Dosimetric comparison of conventional and field-in-field techniques in early stage breast cancer radiotherapy

Introduction: Breast conserving surgery followed by adjuvant radiotherapy (RT) of the whole breast is accepted as the treatment of choice in early stage breast cancer. Due to breast irregularities, it is difficult to access homogenous dose distribution with conventional techniques. Currently, it is possible to use varied breast irradiation techniques, such as field- in-field (FIF), to apply a more homogenous distribution of doses within target volumes, and organs at risk (OAR) sparing which lead to achieve better treatment outcome. This study aimed to compare conventional and FIF techniques dosimetrically Materials and Methods: Twenty patients with early-stage breast cancer underwent computed tomography (CT) with a 16 Slice CT simulator; datasets were transferred to the treatment planning system (TPS) via a digital imaging communications in medicine (DICOM). Two different treatment plans were created for each patient by the same medical physicist: a wedge base (conventional) plan and a FIF plan. Then, dosimetric and monitor unit (MU) results were compared. Results: Dosimetric indices in the planning target volume (PTV) were more satisfying with the FIF technique than with three dimensional-conformal RT (3D-CRT). FIF reduced the maximum doses of PTV and MU. In addition, the FIF technique reduced doses to the heart (in left-side irradiation cases) and ipsilateral lung by 7% and 8%, respectively. FIF also significantly reduced V40 (volume receiving 40 Gy) of heart in left side breast irradiation. V20 of lung (volume receiving 20 Gy), and also doses to the contralateral lung did not differ significantly. Conclusion: FIF can produce more homogenous doses within the PTV, and reduce doses to the OAR. Moreover, by using the FIF technique in breast irradiation, MUs required for therapy are significantly decreased compared with that required by 3D-CRT.

156. Dosimetric comparison between 3D-CRT, Field in Field and VMAT techniques in the adjuvant radiotherapy treatment of breast cancer

Purpose To compare 3D-CRT, Field-in-Field (FIF) and VMAT for adjuvant radiotherapy of breast cancer. Methods 26 patients (13 with left-sided breast cancer, 13 with right-sided) treated to a prescribed dose of 40 Gy (2.667 Gy/fraction; normalized to the target mean) were considered. For all patients a 3D-CRT and a VMAT plan were simulated. 3D-CRTs were planned with 2 primary tangential fields with physical wedges and 2 additional low weighted segments. VMAT plans were performed with a Rapid Arc (RA) technique using 2 partial arc. In a subgroup of 15 patients FIF technique was implemented, combining two open fields with 2–3 segments in two tangential beam directions, without using wedges. Comparisons were performed in terms of PTV coverage and OARs dose-volume histogram (DVH) parameters, considering optimal/acceptable constraints of RTOG-1005 protocol. The dosimetric value of omolateral (lung/heart) OARs were related to the OARs volume included in the chest concavity and to OAR’s inclusion maximum depth. Results Concerning PTV, coverage was similar for the three techniques. The mean dose to OARs are summarized in the table. RA was sub-optimal for all contralateral OARs because mean doses were significantly (p Conclusions The FIF (3D-CRT) technique is similar to RA for PTV data and presents the best results all contralateral OARs. Only when (omolateral) lung and heart have an inclusion in chest concavity >1.5 cm, RA significantly reduces dose in the high DVH region.

Feasibility Study for 3-Dimensional Treatment Planning with Flattening Filter Free (FFF) Beam and Jawless Dual-Level MLC Collimation for Breast Irradiation

Varian Halcyon system with 6MV flattening filter free (FFF) beam and jawless dual-level MLC collimation is mainly intended for faster IMRT/VMAT delivery. We examined if three- dimensional (3D) treatment planning is feasible for breast irradiation with Varian Halcyon system. Ten left sided breast cancer patients treated with conventional 6MV and 3D field in field (FIF) technique (group1; breast volume < 1000 cc) and 5 patients treated with mixed energy of 6/18 MV and 3D FIF technique (group2; breast volume ≥ 1000 cc) were selected to re-plan with Varian Halcyon system using 3D FIF technique. Treatment plans for both groups with Varian Halcyon system using 3D FIF were generated using a treatment planning system based on reference plan parameters previously used for the treatment. FIF planning process with Halcyon system for each case was similar to conventional 3D FIF technique, and the plan criteria was to achieve the same (or similar) D95% for breast planning target volume (PTV) as the reference plan. Plan quality was assessed using 1) V105% (PTV covered by 105% of prescription dose; dose homogeneity), 2) mean heart dose, 3) maximum heart dose, 4) V20Gy (ipsilateral lung volume covered by 20Gy) and compared to the reference plan for each case. In addition, three tangential beam IMRT breast plans treated with 6/18 MV mixed energies (group3) were re-planned with Halcyon system using IMRT technique. The mean breast volume for group 1 and group 2 were 548 cc (ranges 312-912 cc) and 1172 cc (ranges 1000- 1360 cc), respectively. D95% for PTV was almost identical between reference plan and Halcyon plan for both groups. Other mean dosimetric values with group1 were as following; 1) V105: 5.8 % vs. 8.3 % (p = 0.006), 2) Mean heart dose: 0.88 Gy vs. 1.13 Gy (p = 0.01), 3) Max heart dose: 13.1 Gy vs. 13.5 Gy (p = 0.8), 4) Ipsilateral lung V20 Gy: 8.7 % vs. 10.4 % (p = 0.26) for reference plan and Halcyon plan, respectively. Similarly for group 2; 1) V105: 5.9 % vs.22.2 % (p = 0.03), 2) Mean heart dose: 0.73 Gy vs. 1.18 Gy (p < 0.001), 3) Max heart dose: 7.7 Gy vs. 11.6 Gy (p = 0.2), 4) Ipsilateral lung V20 Gy: 7.0 % vs. 7.4 % (p = 0.85) for reference plan and Halcyon plan, respectively. For the IMRT plan comparison (group 3; breast volume ranges 1255-1687 cc), all 3 reference plans showed better dosimetric results compared to Halcyon plans; 1) V105: 5.2 % vs.18.1 %, 2) Mean heart dose: 0.85 Gy vs. 3.0 Gy, 3) Max heart dose: 10.6 Gy vs. 40.3 Gy, 4) Ipsilateral lung V20 Gy: 5.3 % vs. 14.9 % for reference plan and Halcyon plan, respectively. The 3D treatment planning with Varian Halcyon system is feasible for breast irradiation with comparable dose homogeneity and critical organs dosimetry for breast volume < 1000 cc. However, for large breast volumes the dose homogeneity is significantly worse with both 3D plan and IMRT probably because of having only low energy with non-flattened beam.

Dosimetric Evaluation of The Field-In-Field Technique For Large Breast Cancer Irradiation.

The aim of this work is using multi-segmented conformal radiotherapy, field in field (FIF) for large breast cancer treatment, the dose coverage of the planning target volume (PTV) and evaluation the radiation load on the organs at risk (OARs). Ten patients with large breast of mean PTV was 1489 ± 335 Cm3 were included. Many parameters used in the dose evaluations in the planning target volume (PTV) and the organs at risk (OARs) volume including ipsi lateral lung, heart, and the contralateral breast, Dose homogeneity index (DHI) and conformity index (PITV). The FIF technique for all patients improved the homogeneity and conformity of the PTV, where the mean values of maximum dose of the PTV was 107%, the volumes over the prescription dose in irradiated volumes received very low doses. For each dosimetry of the organs at risk, the FIF technique reduced the dose received to theses organs. In conclude the FIF technique provided better dose distribution in the PTV and reduced the doses in the OARs and improving homogeneity and conformity of the planning volume.

A treatment planning comparison of contemporary photon-based radiation techniques for breast cancer.

Background and purposeAdjuvant radiation therapy (RT) of the whole breast (WB) is still the standard treatment for early breast cancer. A variety of radiation techniques is currently available according to different delivery strategies. This study aims to provide a comparison of six treatment planning strategies commonly adopted for breast-conserving adjuvant RT and to use the Pareto concept in an attempt to assess the degree of plan optimization.Materials and methodsTwo groups of six left- and five right-sided cases with different dose prescriptions were involved (22 patients in total). Field-in-Field (FiF), two and four Fields static-IMRT (sIMRT-2f and sIMRT-4f), Volumetric-Modulated-Arc-Therapy (VMAT), Helical Tomotherapy (HT) and Static-Angles Tomotherapy (TomoDirect™ – TD) were planned. Dose volume constraints were taken from the RTOG protocol 1005. Pareto fronts were built for a selected case to evaluate the reliability of the plan optimization process.ResultsThe best target dose coverage was observed for TD able to improve significantly (p < 0.01) the V95% in a range varying from 1.2% to 7.5% compared to other techniques. The V105% was significantly reduced up to 2% for HT (p < 0.05) although FiF and VMAT produced similar values. For the ipsilateral lung, V5Gy, V10Gy and Dmean were significantly lower than all other techniques (p < 0.02) for TD while the lowest value of V20Gy was observed for HT. The maximum dose to contralateral breast was significantly lowest for TD (p < 0.02) and for FiF (p < 0.05). Minor differences were observed for the heart in left-sided patients. Plans for all tested techniques were found to lie on their respective Pareto fronts.ConclusionsOverall, TD provided significantly better results in terms of target coverage and dose sparing of ipsilateral lung with respect to all other evaluated techniques. It also significantly minimized dose to contralateral breast together with FiF. Pareto front analysis confirmed the reliability of the optimization for a selected case.

Breast-conserving radiotherapy with simultaneous integrated boost; field-in-field three-dimensional conformal radiotherapy versus inverse intensity-modulated radiotherapy - A dosimetric comparison: Do we need intensity-modulated radiotherapy?

Background and Purpose:To examine the feasibility of improving breast-conserving radiotherapy with simultaneous integrated boost (SIB) and analyzing the efficiency of forward versus inverse intensity-modulated radiotherapy (IMRT) techniques in providing the same.Materials and Methods:Three-dimensional conformal radiotherapy (3DCRT) field-in-field (FIF) plans with simultaneous and sequential boost and IMRT SIB plans were generated for the datasets of 20 patients who had undergone breast-conserving surgery. The 3 plans were compared dosimetrically for efficiency in terms of planning target volume (PTV) coverage (PTV 95%), homogeneity and conformity, dose delivered to ipsilateral/contralateral lungs (I/L: V10, V20, C/L: Vmean, V5), heart and contralateral breast (Vmean, V30 for heart and Vmean, V1, V5 for C/L breast).Results:The FIF 3DCRT plan with SIB (PLAN B) was more homogeneous than the classical technique with sequential boost (PLAN A). There were less hot spots in terms of Dmax (63.7 ± 1.3) versus Dmax (68.9 ± 1), P < 0.001 and boost V107%, B (0.3 ± 0.7) versus A (3.5 ± 5.99), P = 0.001. The IMRT SIB (PLAN C) did not provide any significant dosimetric advantage over the 3DCRT SIB technique. IMRT SIB plan C was associated with increased dose to contralateral lung in-terms of V5 (10.35 +/- 18.23) vs. (1.13 +/- 4.24), P = 0.04 and Vmean (2.12 ± 2.18) versus Vmean (0.595 ± 0.89), P = 0.008. There was 3-fold greater exposure in terms of Monitor Unit (MU) (1024.9 ± 298.32 versus 281.05 ± 20.23, P < 0.001) and treatment delivery time.Conclusions:FIF 3DCRT SIB provides a dosimetrically acceptable and technically feasible alternative to the classical 3DCRT plan with sequential boost for breast-conserving radiotherapy. It reduces treatment time by 2 weeks. IMRT SIB does not appear to have any dosimetric advantage; it is associated with significantly higher doses to contralateral lung and heart and radiation exposure in terms of MU.

Improved dose homogeneity using electronic compensation technique for total body irradiation.

In total body irradiation (TBI) utilizing large parallel‐opposed fields, the manual placement of lead compensators has conventionally been used to compensate for the varying thickness throughout the body. The goal of this study is to pursue utilizing the modern electronic compensation (E‐comp) technique to more accurately deliver dose to TBI patients. Bilateral parallel‐opposed TBI treatment plans were created using E‐comp for 15 patients for whom CT data had been previously acquired. A desirable fluence pattern was manually painted within each field to yield a uniform dose distribution. The conventional compensation technique was simulated within the treatment planning system (TPS) using a field‐in‐field (FIF) method. This allows for a meaningful evaluation of the E‐comp technique in comparison to the conventional method. Dose–volume histograms (DVH) were computed for all treatment plans. The mean total body dose using E‐comp deviates from the prescribed dose (4 Gy) by an average of 2.4%. The mean total body dose using the conventional compensation deviates from the prescribed dose by an average of 4.5%. In all cases, the mean body dose calculated using E‐comp technique deviates less than 10% from that of conventional compensation. The average reduction in maximum dose using E‐comp compared to that of the conventional method was 30.3% ± 6.6% (standard deviation). In all cases, the s‐index for the E‐comp technique was lower (10.5% ± 0.7%) than that of the conventional method (15.8% ± 4.4%), indicating a more homogenous dose distribution. In conclusion, a large reduction in maximum body dose can be seen using the proposed E‐comp technique while still producing a mean body dose that accurately complies with the prescription dose. Dose homogeneity was quantified using s‐index which demonstrated a reduction in hotspots with E‐comp technique. Electronic compensation technique is capable of more accurately delivering a total body dose compared to conventional methods.

New approach to evaluating the gamma criteria for the breast field-in-field technique

The gamma evaluation method is widely used for accurate quantitative comparison of measured dose distribution and treatment plan verification in intensity-modulated radiotherapy. In the case of field-in-field (FIF) plans, the standard gamma criterion fails to distinguish clinically significant differences in planned and actual dose distributions. The proposed modified gamma evaluation algorithm takes into account only high-dose-gradient regions in calculating the value of the gamma criterion. The aim of this study is to test the new algorithm in FIF plans, evaluating the test’s sensitivity to dose, segment size and shape, and compare it with a commercially available gamma algorithm. For this study, several clinical cases were modeled using MATLAB® software. For segment shape and size tests a 20 × 20 cm base field was modeled. Randomly shaped rectangular segment fields with sizes from 5% to 50% of the base field area with 5% increments were added to the base field. Dose distribution was calculated using MATLAB® for use as a starting point to make distorted plans with segments displaced to simulate patient movement or positioning errors during irradiation. For sensitivity tests a 20 × 20 cm base field and rectangular segment with an area of 5% of the base field was added at the center. For the reference, 120 dose units were prescribed, 100 for the base field and 20 for the segment. Dose modulation was done by altering the segment dose in steps of two dose units per measurement. Segment dose-modulated fields were compared with the reference using the modified gamma criterion. Pixel acceptance criteria were based on dose difference ∆DM = 3% and distance-to-agreement (DTA) ∆dM = 3 mm. Only pixels in those regions where the dose gradient exceeded 5% were used; and 95% of all pixels in the region should be within this criterion for the treatment plan to be accepted. Comparison with commercially available gamma evaluation software demonstrated that the standard criterion is not able to detect clinically significant shifts of 5 mm in the FIF plans, but the new algorithm detected all shifts before they exceeded 3 mm. In turn, the commercial gamma criterion showed a higher dose sensitivity: dose alterations larger than two dose units show a steep drop of ‘passed’ pixel number below the 95% threshold level.