Field-in-field Plans Research Articles

Comparison of Lung and Contralateral Scattered Breast Dose between Field-in-Field and Wedge Techniques in Patients with Early Breast Cancer

Purpose: This study aims to evaluate the dosimetric result of the Field-In-Field (FIF) plans compared with Tangential Wedged Beams (TWB) plans for whole breast radiotherapy of patients. Materials and Methods: In this survey, we entered fifty patients with breast-conserving surgery and postoperative whole-breast radiotherapy. FIF and a TWB plan were made for each patient to compare dosimetric outcomes. Results: The Homogeneity Index (HI) and Conformity Index (CI) were specified for the evaluation of Planning Target Volume (PTV). The mean dose of the ipsilateral lung and contra-lateral breast for the evaluation of organs at risk dose were used. The FIF plans had significantly lower HI (p < 0.01) and CI (p < 0.01) than those of the TWB plans. It means in the dosimetric comparisons of the PTV, the FIF plans were better than the TWB plans. The V10lung (31.152vs. 32.72%, p < 0.01), V20lung (25.6064vs. 26.6%, p < 0.01) V30lung (17.4% vs. 18.4%, p < 0.01) were lower with the FIF plans compared with those of the TWB plans, with statistical significance. The FIF plans had a lower mean dose for the lung than those of TWB plans (1225.48 vs. 1670.32 cGy) but no statistical significance (p=0.06). The mean dose in the contra-lateral of the breast in FIF plans was lower than in TWB plans (61.666 vs. 163.45 cGy), with statistical significance (p < 0.01). Conclusion: The FIF plans increased the dose homogeneity, and conformity of the target volume for the whole-breast irradiation compared with the TWB plans. Moreover, the doses of organs at risk (ipsilateral lung and contralateral breast) were reduced with FIF plans.

Dosimetric effect of rotational setup errors in volumetric modulated arc therapy and field-in-field treatment of left-sided breast cancer

Setup errors are an important factor in the dosimetric accuracy of radiotherapy delivery. In this study, we investigated how rotational setup errors influence the dose distribution in volumetric modulated arc therapy (VMAT) and tangential field-in-field (FiF) treatment of left-sided breast cancer with supraclavicular lymph node involvement in deep inspiration breath hold. Treatment planning computed tomography images and radiotherapy plans of 20 patients were collected retrospectively for the study. Rotational setup errors up to 3° were simulated by rotating the planning images, and the resulting dosimetric changes were calculated. With rotational setup errors up to 3°, the median decrease of V95% to clinical target volume was less than 0.8 percentage point in both VMAT and FiF plans. The dose distribution of the heart and left anterior descending artery was more stable with respect to rotations in VMAT plans compared to FiF plans. Correction of ≥1° setup errors is recommended due to increased doses to the heart and left anterior descending artery after 1° setup errors.

Dosimetric comparison of three-dimensional (3D), intensity-modulated radiotherapy (IMRT) and hybrid IMRT for left-sided postmastectomy radiation therapy (PMRT)

Abstract Purpose: This study aimed to determine the suitable breast treatment technique for a small facility’s hospital with limited staff and equipment resources. The benefits and drawbacks of each technique should be considered to guide radiation oncologists choose the appropriate treatment option for postmastectomy radiation therapy (PMRT) patients. Methods and Materials: This study included the computed tomography images of 15 patients who received left-sided PMRT. The patient’s characteristics were classified into two groups: 1. irradiation of only the chest wall (CW) and 2. CW lymph nodes plus supraclavicular lymph nodes (SPCs). All 15 PMRT patients were generated in 4 treatment techniques including 3DCRT, field-in-field (FiF), intensity-modulated radiotherapy (IMRT) and hybrid (3DCRT + IMRT). Each treatment technique’s dosimetric parameters and treatment time were compared. Result: All four treatment plans met the acceptable criteria. The IMRT plans achieved the highest plan quality scores for two groups of PMRT patients but require the longest treatment time, whereas the 3DCRT and FiF plans demonstrated superiority for organ at risk (OAR) sparing and required the shortest treatment time when compared with the IMRT and hybrid plans. Conclusion: The IMRT plan had the highest plan quality but required the most time to treat. Treatment times are critical in facilities with limited resources. As a result, the FiF plan was found to be a suitable technique for both CW-only and CW plus SPC irradiation due to its short treatment time and high plan quality scores for OAR dose sparing.

Determination and comparison of dosimetric parameters of three-dimensional conformal radiotherapy, field in field, and intensity-modulated radiotherapy techniques in radiotherapy of breast conserving patients.

Three radiation therapy techniques for breast are common, namely three-dimensional conformal radiotherapy (3D-CRT), Field-in-Field (FIF), and Intensıty-Modulated Radıotherapy (IMRT). The purpose of this study was to determine and compare dosimetric parameters of three different treatment planning planning types; 3D-CRT, FIF, and IMRT in target and normal tissues after breast-conserving surgery. One hundred patients with left or right breast cancer cooperated in this study. They were divided into three categories (small, medium, and large size) based on breast volume. Three treatment planning techniques were carried out by planner for each patient in Prowess® 5.2 Treatment Planning System. The dosimetric parameters were obtained from dose-volume histograms using the CERR software (MATLAB Company, Washington, USA), which runs as an add-on in MATLAB software. 3D-CRT technique with the highest value of Dmax creates more hot spots than the other techniques in the tumor region (P = 0.013). IMRT and FIF showed the best uniformity compared to 3D-CRT in all groups with respect to the values of the parameters D98 and D2. IMRT provided the best coverage in the tumor compared to other methods (P < 0.001). 3D-CRT technique yielded a high volume receiving ≥107% of the prescription dose (P < 0.001). Among the three methods, the FIF method results in a lower dose to the lung for treatment based on the V5 and V20 parameters (P < 0.001). Homogeneity index for IMRT was better than FIF, as well as, conformity index (CI) for IMRT and FIF was better than 3D-CRT. IMRT and FIF plans offered excellent target coverage and uniformity, whereas FIF had better protection of healthy tissues. Thus FIF method is an efficient method to improve the quality of treatment for breast cancer patients.

Combining Step-and-Shoot Intensity Modulated Radiation Therapy Concomitant Boost to Tumor Bed and 3D Breast Field-in-Field Plans for Hypofractionated Breast Radiotherapy

<h3>Purpose/Objective(s)</h3> To investigate the efficacy and safety of step-and-shoot intensity modulated radiation therapy (IMRT) concomitant boost (CB) to tumor bed (TB) combined with 3D breast field-in-field (FIF) plans for hypofractionated breast radiotherapy. <h3>Materials/Methods</h3> We initiated prospective cohort study since January, 2020. The patients with early-stage breast cancer or breast ductal carcinoma in situ who received breast-conserving surgery underwent sixteen-fraction treatment. All received prescribed dose of 40 Gy 3D FIF plans to breast, CB with 8 Gy to TB by IMRT. We applied the identical contours and PTV coverage to compare the original plans with the re-plans using conventional fractions of breast FIF followed by en face electron beams to TB on the same patients. Plan quality including maximum dose, RTOG conformal index (CI) and homogeneity index (HI) of PTV_TB, mean dose and volumes irradiated to doses of 5 Gy (V₅) of heart and V₂₀ of ipsilateral lung, in addition to acute toxicity and any recurrence were evaluated. Lyman normal tissue complication probability (NTCP) model for moderate to severe breast fibrosis established by Cambridge and EORTC trials was also calculated. Paired sample t-test and Wilcoxon signed-rank test were used. <h3>Results</h3> Thirty patients with sixty treatment plans were reviewed. The majority (19/30) were pathological prognostic stage I breast cancer and half of the patients were left-sided diseases. No patient experienced more than grade 2 acute toxicity. No recurrence was observed during the follow-up. Mean HI (D₂-D₉₈/D_p × 100; where D₂ = minimum dose to the 2% of the target volume, D₉₈ = minimum dose to the 98% of the target volume, and D_p = prescribed dose) of PTV_TB is 9.4 vs. 18.5 (<i>P</i> < .05). Maximum dose divided by reference dose was also lower in the CB group by 2.9% (<i>P</i> < .05). Mean CI is 1.45 in the CB group compared to 1.63 in the conventional fraction plans (<i>P</i> = .07). In terms of EQD2, mean dose and V₅ of heart for left-sided breast cancer are similar (<i>P</i> = .12 and 0.10). Besides, mean dose and V₂₀ of ipsilateral lung are comparable (<i>P</i> = .26 and 0.43). NTCP for breast fibrosis were all lower in the CB group (Mean: 20.02% vs. 22.13%; <i>P</i> < .05). <h3>Conclusion</h3> Hypofractionated breast radiotherapy combing 3D FIF plans and IMRT CB to TB decreased breast moderate to severe fibrosis by Lyman NTCP model and improved homogenous dose distributions without excessive dose to normal tissue, when compared to conventional fractions using FIF and electron beams. It may reduce the toxicity, and is also labor-saving for patients, radiation oncologists and staff.

Dosimetric Parameters Comparison of Four-Field and Field-in-Field Radiotherapy Planning in Treatment of Prostate Cancer

Purpose: Prostate cancer is one of the most common malignant cancers. Several radiotherapy planning methods have been suggested for the treatment of prostate cancer. In this study, four-field, and Field-In-Field (FIF) planning methods were compared based on dosimetric parameters.&#x0D; Materials and Methods: In the radiotherapy Treatment Planning System (TPS) for 10 patients who were treated with the common four-field method, the planning was also performed by the FIF method. Dosimetric parameters were measured for Planning Target Volume (PTV), rectum, and bladder. These parameters included maximum dose, minimum dose, mean dose, V15%, V25%, V30%, and V35%, as well as Homogeneity Index (HI) and Conformity Index (CI). Two treatment planning methods based on dosimetric parameters were compared using paired t-test.&#x0D; Results: Maximum, minimum and mean dose in PTV, rectum, and bladder were significantly different for the two techniques. There was no significant difference between the two planning techniques in dosimetric parameters of V15%, V25%, V30%, and V35% for rectum and bladder. The FIF technique delivers more doses to the tumor. HI was better in the FIF method than in the four-field method, but CI was not significantly different. In both techniques, the rectum and bladder did not receive doses above 60 Gy.&#x0D; Conclusion: In the treatment of prostate cancer in both Four-field and FIF planning methods, the dose to the rectum and bladder is less than the tolerance dose. FIF technique is recommended to better control the tumor. Based on dosimetric parameters, no significant findings were obtained that prove the superiority of FIF over the four-field technique in the treatment of prostate cancer.

Automation of radiation treatment planning for rectal cancer.

PurposeTo develop an automated workflow for rectal cancer three‐dimensional conformal radiotherapy (3DCRT) treatment planning that combines deep learning (DL) aperture predictions and forward‐planning algorithms.MethodsWe designed an algorithm to automate the clinical workflow for 3DCRT planning with field aperture creations and field‐in‐field (FIF) planning. DL models (DeepLabV3+ architecture) were trained, validated, and tested on 555 patients to automatically generate aperture shapes for primary (posterior–anterior [PA] and opposed laterals) and boost fields. Network inputs were digitally reconstructed radiographs, gross tumor volume (GTV), and nodal GTV. A physician scored each aperture for 20 patients on a 5‐point scale (>3 is acceptable). A planning algorithm was then developed to create a homogeneous dose using a combination of wedges and subfields. The algorithm iteratively identifies a hotspot volume, creates a subfield, calculates dose, and optimizes beam weight all without user intervention. The algorithm was tested on 20 patients using clinical apertures with varying wedge angles and definitions of hotspots, and the resulting plans were scored by a physician. The end‐to‐end workflow was tested and scored by a physician on another 39 patients.ResultsThe predicted apertures had Dice scores of 0.95, 0.94, and 0.90 for PA, laterals, and boost fields, respectively. Overall, 100%, 95%, and 87.5% of the PA, laterals, and boost apertures were scored as clinically acceptable, respectively. At least one auto‐plan was clinically acceptable for all patients. Wedged and non‐wedged plans were clinically acceptable for 85% and 50% of patients, respectively. The hotspot dose percentage was reduced from 121% (σ = 14%) to 109% (σ = 5%) of prescription dose for all plans. The integrated end‐to‐end workflow of automatically generated apertures and optimized FIF planning gave clinically acceptable plans for 38/39 (97%) of patients.ConclusionWe have successfully automated the clinical workflow for generating radiotherapy plans for rectal cancer for our institution.

Evaluation of field-in-field, three-field, and four-field techniques for treatment planning of radiotherapy of pancreatic cancer.

Pancreatic adenocarcinoma is a lethal condition with poor outcomes by various treatment modalities and an increasing incidence. The aim of this study is to evaluate the advantages of field-in-field (FIF) versus three-field and four-field radiation treatment planning techniques in three-dimensional treatment of patients with pancreatic cancer. Materials and Methods: The evaluations of these planning techniques were performed in terms of physical and biological criteria. Radiotherapy treatment data of 20 patients with pancreatic cancer were selected and evaluated for FIF, three-field, and four-field treatment techniques. The patients were treated by 6 MV photon beam of a medical linac, and these three treatment planning techniques were evaluated for all the 20 patients. The plans were compared based on dose distribution in the target volume, monitor unit (MU), and dose to organs at risk (OARs). Results: The results have shown that, with assuming the same prescribed dose to planned target volume, FIF plans have some advantages over three-field and four-field treatment plans, based on MU values, V20 Gy in the right lung, V20 Gy in the left lung, Dmean in the left kidney, Dmean in the liver, and Dmean in the spinal cord. Based on the obtained results, the use of FIF technique reduces MUs compared to the three-field and four-field techniques. Conclusion: Having a less MU for performing treatment reduces scattered radiation and therefore reduces the risk of secondary cancer in normal tissues. In addition, the use of FIF technique has advantage of less radiation dose to some OARs.

Semiautomatic Treatment Planning for the Field-in-field Technique in Whole Brain Irradiation.

In radiation therapy, the field-in-field (FIF) technique is used to prevent the administration of unnecessarily high doses to reduce toxicity. Recently, the FIF technique has been used for whole brain irradiation (WBI). Using the FIF technique, the volume that receives a higher than prescribed dose (hotspot) can be largely reduced; however, the treatment planning requires time. Therefore, to reduce the burden on the treatment planners, we propose a semiautomatic treatment planning method for the FIF technique. In the semiautomatic FIF technique, hotspot regions in a treatment plan without the FIF technique are identified three-dimensionally, and beams with blocks that cover the hotspot regions using a multileaf collimator (sub-beams) are automatically created. The sub-beams are added to the original plan, and weights are assigned based on the maximum dose of the original plan to decrease the doses in the hotspot regions. This method was applied to 22 patients previously treated with WBI, wherein treatment plans were originally created without the FIF technique. In the semiautomatic FIF plans, the hotspots almost disappeared. The dose to 95% of the volume and the volume receiving at least 95% of the prescribed dose in the planning target volume decreased by only 0.3% ± 0.2% and 0.0% ± 0.1%, respectively, on average compared with those in the original plan. The average semiautomatic FIF processing time was 28 ± 4 s. The proposed method reduced the hotspot regions with a slight change in the target coverage.

Is it advantageous to use deep inspiration breath hold (DIBH) over free breathing for FAST-Forward dose fractionation scheme in treating carcinoma of left-sided breast? A dosimetric study

Abstract Aim: To study the effect of deep inspiration breath hold (DIBH) on Fast-Forward trial for left-sided breast radiotherapy dosimetrically using tangential field-in-field (FiF), flattening filtered volumetric-modulated arc therapy (FF-VMAT) and flattening filter free volumetric-modulated arc therapy (FFF-VMAT) in comparison with free breathing (FB). Methods: Computed tomography images were acquired on 15 patients with carcinoma of left breast in FB and DIBH. Planning target volume (PTV) and organs at risk were contoured on both image sets. Dose of 26 Gy in five daily fractions was prescribed to PTV. FiF, FF-VMAT and FFF-VMAT plans were created in treatment planning system on both FB and DIBH. PTV V95%, V107%, D0·1 cc, CI and HI, heart V1·5 Gy, V7 Gy, lung left V8 Gy, monitor units (MU) and beam ON time were used for evaluation. Different technique analysis in same breathing condition and FB versus DIBH for same planning technique were performed. Results: Mean of all 15 patients was reported as mean ± 1 standard deviation. PTV V95% was 97·55 ± 0·10 (FiF), 95·75 ± 0·66 (FF-VMAT) and 96·15 ± 0·46 (FFF-VMAT) in FB while 97·34 ± 0·50 (FiF), 96·03 ± 0·71 (FF-VMAT) and 95·86 ± 0·63 (FFF-VMAT) in DIBH. Heart V7 Gy was 8·53 ± 4·26 (FiF), 8·86 ± 2·20 (FF-VMAT) and 9·27 ± 2·46 (FFF-VMAT) in FB while 6·30 ± 2·98 (FiF), 5·23 ± 2·20 (FF-VMAT) and 4·68 ± 2·01 (FFF-VMAT) in DIBH. p-value of heart V7 Gy between FB and DIBH was 0·278 (FiF), 0·009 (FF-VMAT) and 0·003 (FFF-VMAT). Beam ON time for FFF-VMAT was reduced by 65% (FF-VMAT) and 11% (FiF). Conclusion: Conformal dose to PTV was achieved better with VMAT plans. FFF-VMAT was delivered in less time compared to FF-VMAT and FiF for 26 Gy in five fractions. Heart dose can be significantly minimised with DIBH for VMAT plans.

Tridimensional dose evaluation of the respiratory motion influence on breast radiotherapy treatments using conformal radiotherapy, forward IMRT, and inverse IMRT planning techniques.

To evaluate the respiratory motion influence on the tridimensional (3D) dose delivery to breast-shaped phantoms using conformal radiotherapy (3D-RT), Field-in Field (FiF), and IMRT planning techniques. This study used breast-shaped phantoms filled with MAGIC-f gel dosimeter to simulate the breast, and an oscillation platform to simulate the respiratory motion. The platform allowed motion in the anterior-posterior direction with oscillation amplitudes of 0.34cm, 0.88cm, and 1.22cm. CT images of the static phantom were used for the 3D-RT, FiF, and IMRT treatment planning. Five phantoms were prepared and irradiated for each planning technique evaluated. Phantom 1 was irradiated static, phantoms 2-4 were irradiated moving with the three different motion amplitudes, and phantom 5 was used as a reference. The 3D dose distributions were obtained by relaxometry of magnetic resonance imaging, and the respiratory motion influence in the doses distribution was accessed by gamma evaluations (3%/3mm/15% threshold) comparing the measurements of the phantoms irradiated under movement with the static ones. The mean gamma approvals for three oscillatory amplitudes were 96.44%, 93.23%, and 91.65%; 98.42%, 95.66%, and 94.31%; and 94.49%, 93.51%, and 86.62% respectively for 3D-RT, FiF and IMRT treatments. A gamma results profile per slice along the phantom showed that for FiF and IMRT irradiations, most of the failures occurred in the central region of the phantom. By increasing the respiratory motion movement, the dose distribution variations for the three planning techniques were more pronounced, being the FiF technique variations the smallest one.

Clinical Experience and Dosimetry Outcome in Treating Breast Cancer with Field-in-Field Technique

Purpose: The study is aimed to establish the dosimetric characteristics of field-in-field (FiF) technique for carcinoma of breast treatment in Nepal. We assumed that FIF technique may result in improved dose distribution and reduced acute toxicity in these patients. Methods: Forty breast cancer patients participated in this study. A total dose of 50 Gy in 25 fractions was prescribed to the planning target volume. FiF plan was generated in treatment planning system. Dose volume histograms were evaluated for PTV and organs at risks. Several parameters were analyzed for the PTVs and organ at risks (OARs) together with the Conformity index (CI), and the Homogeneity index (HI). Results: The dose coverage of breast volume was achieved. The V95% (volume of 95%) of PTV covered D95% (Dose of 95%). The PTV dose was covered to 49.98 ± 0.9 Gy and 49.81 ± 1.1 Gy for the left and right breast, respectively. The mean lung dose was 14.87 ± 0.91 Gy. The homogeneity index (0.26 ± 0.17 and 0.22 ± 0.13) and conformity index (1.59 ± 0.75 and 1.36 ± 0.45) were analyzed for left and right breast, respectively. Conclusion: The study supports the viability of FiF technique in the treatment of breast cancer in Nepal. The FIF technique enables better dose distribution in the PTV and reduces dose to OARs. The FiF technique provides dosimetric advantages and requires less planning time.

Dosimetric comparison of intensity-modulated radiation therapy (IMRT) and field-in-field (FIF) technique for head-and-neck cancer

AbstractPurpose:This study compared the plan dosimetry between the intensity-modulated radiation therapy (IMRT) and field-in-field (FIF) technique for head-and-neck cancer using the Elekta Monaco treatment planning system (TPS).Materials and methods:A total of 20 head-and-neck cancer patients were selected in this study. IMRT and FIF plans for the patients were created on the Monaco TPS (ver. 5.11.02) using the 6-MV photon beam generated by the Elekta Synergy linear accelerator. The dose–volume histograms, maximum doses, minimum doses, mean doses of the target volumes and organs-at-risk (OARs), conformity index (CI), homogeneity index (HI) and monitor units (MUs) were determined for each IMRT and FIF plan. All IMRT plans passed the patient-specific quality assurance tests from the 2D diode array measurements (MatriXX Evolution System, IBA Dosimetry, Germany).Results:The results showed that the dose distribution to the target volumes of IMRT plans was better than FIF plans, while the dose (mean or max dose) to the OAR was significantly lower than FIF plan, respectively. IMRT and FIF resulted in planning target volume coverage with mean dose of 71·32 ± 0·76 and 73·12 ± 0·62 Gy, respectively, and HI values of 0·08 ± 0·01 (IMRT) and 0·19 ± 0·06 (FIF). The CI for IMRT was 0·98 ± 0·01 and FIF was 0·97 ± 0·01. For the spinal cord tolerance (maximum dose &lt; 45 Gy), IMRT resulted in 39·85 ± 2·04 Gy compared to 41·37 ± 2·42 Gy for FIF. In addition, the mean doses to the parotid grand were 27·27 ± 7·48 and 48·68 ± 1·62 Gy for the IMRT and FIF plans, respectively. Significantly more MUs were required in IMRT plans than FIF plans (on average, 846 ± 100 MU in IMRT and 467 ± 41 MU in FIF).Conclusions:It is concluded that the IMRT technique could provide a better plan dosimetry than the FIF technique for head-and-neck patients.

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.

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.

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.

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.

Automated Field-In-Field (FIF) Plan Framework Combining Scripting Application Programming Interface and User-Executed Program for Breast Forward IMRT.

Purpose:To develop an one-click option on treatment planning system that enables for the automated breast FIF planning by combining the Eclipse Scripting application programming interfaces and user-executed programming in Windows.Methods:Scripting application programming interfaces were designed to promote automation in clinical workflow associated with radiation oncology. However, scripting cannot provide all functions that users want to perform. Thus, a new framework proposes to integrate the benefits of the scripting application and user-executed programming for the automated field-in-field technique. We adopted the Eclipse Scripting applications, which provide an interface between treatment planning system server and client and enable for running the executed program to create dose clouds and adjust the planning parameters such as multi-leaf collimator placements and monitor unit values. Importantly, all tasks are designed to perform with one-click option on treatment planning system, including the automated pushback of the proposed plan to the treatment planning system.Results:The plans produced from the proposed framework were validated against the manual field-in-field plans with 40 retrospective breast patient cases in planning efficiency and plan quality. The elapsed time for running the framework was less than 1 minute, which significantly reduced the manual multi-leaf collimator/monitor unit adjustment time. It decreased the total planning time by more than 50%, relative to the manual field-in-field planning. In dosimetric aspects, the mean and maximum dose of the heart, lung, and whole breast did not exceed 1% deviation from the manual plans in most patient cases, while maintaining the target dose coverage and homogeneity index inside the target volume. From numerical analysis, the automated plans were demonstrated to be sufficiently close to the manual plans.Conclusion:The combination of scripting applications and user-executed programming for automated breast field-in-field planning accomplished a significant enhancement in planning efficiency without degrading the plan quality, relative to the manual field-in-field procedure.

Field-In-Field Plan Versus Tangential Wedged Beam Plan in Chest Wall Radiotherapy of Post-Mastectomy Patients: Treatment Planning Study

Introduction: In this study, dose distribution of the chest wall in post-mastectomy breast cancer patients was evaluated and compared in the tangential wedged beam (TWB) and field-in-field (FIF) plans. Materials and Methods: Thirty-six patients with left-sided breast cancer were enrolled in this study. The FIF and TWB plans were generated for each patient to compare dosimetric parameters of the chest wall. The maximum dose (Dmax), homogeneity index (HI), conformity index (CI), and uniformity index (UI) were defined and used for comparison of the dosimetric parameters of the planning target volume (PTV) in both FIF and TWB plans. The percentage of volumes receiving at least 10, 20, 30, and 40 Gy of the left lung and 5, 10, 20, 25 and 30 Gy of the heart were used to compare the dosimetric results of the organs at risk. Statistical analysis was performed using SPSS, version 20. Results: The FIF plan had significantly lower HI (P=0.000) than the TWB plan, indicating that the FIF plan was better than the TWB plan in PTV. The V40lung (15.36±4.35 vs. 18.37±4.42) and V30heart (8.15±3.75 vs. 10.94±3.94; P=0.000) were significantly lower in the FIF plan than in the TWB plan. In addition, the monitor unit (MU) was significantly lower in the FIF plan than in the TWB plan (227.76 vs. 323.59; P=0.000). Conclusion: The FIF plan significantly reduced the dose volume of the left lung and heart in post-mastectomy radiotherapy compared to the TWB plan. Therefore, the FIF plan is recommended for this purpose.

Dosimetric evaluation of the dose calculation accuracy of different algorithms for two different treatment techniques during whole breast irradiation

Purpose In this study, dosimetric comparison of field in field (FIF) and intensity modulated radiation therapy (IMRT) techniques used for treatment of whole breast radiotherapy (WBRT) were made. The dosimetric accuracy of treatment planning system (TPS) for Anisotropic Analytical Algorithm (AAA) and Acuros XB (AXB) algorithms in predicting PTV and OAR doses was also investigated. Methods Two different treatment planning techniques of left-sided breast cancer were generated for rando phantom. FIF and IMRT plans were compared for doses in PTV and OAR volumes including ipsilateral lung, heart, left ascending coronary artery, contralateral lung and the contralateral breast. PTV and OARs doses and homogeneity and conformality indexes were compared between two techniques. The accuracy of TPS dose calculation algorithms was tested by comparing PTV and OAR doses measured by thermoluminescent dosimetry with the dose calculated by the TPS using AAA and AXB for both techniques. Results IMRT plans had better conformality and homogeneity indexes than FIF technique and it spared OARs better than FIF. While both algorithms overestimated PTV doses they underestimated all OAR doses. For IMRT plan, PTV doses, overestimation up to 2.5% was seen with AAA algorithm but it decreased to 1.8% when AXB algorithm was used. Based on the results of the anthropomorphic measurements for OAR doses, underestimation greater than 7% is possible by the AAA. The results from the AXB are much better than the AAA algorithm. However, underestimations of 4.8% were found in some of the points even for AXB. For FIF plan, similar trend was seen for PTV and OARs doses in both algorithm. Conclusions When using the Eclipse TPS for breast cancer, AXB the should be used instead of the AAA algorithm, bearing in mind that the AXB may still underestimate all OAR doses.