RYAN G. SALEM
A Dosimetric Comparison of the Field- in- Field Method versus Electronic Compensation in the Treatment of Left Sided, Early Stage Breast Cancer: A Case Study.Authors: Ryan Salem, BS, RT(T), Christina Ong BS, Sean Ferguson BS, RT(T), Rodger Williams, BS, CMD, RT(R)(T)Medical Dosimetry Program at the University of Wisconsin – La Crosse, WIAbstractIntroduction: The objective of the case study was to perform a dosimetric comparison between the 3D conformal field- in- field (FIF) and electronic compensation, or irregular surface compensator (ISC), techniques in whole breast radiation therapy for earlylow stage breast cancer. The metrics of target coverage, healthy tissue constraints, and maximum dose regions were analyzed to determine the more effective treatment method. Case Description: For this retrospective study, 10Ten patients, retrospectively, from a single cancer center were selected from a single cancer center who were diagnosed with earlylow stage, left sided breast cancer ranging from ductal carcinoma in situ (DCIS) to Stage II T2N0M0. All patients received a lumpectomy procedure prior to radiation treatment planning. The patients’ planning target volume (PTV) and gross tumor volume (GTV) , representative of the breast tissue and lumpectomy site, respectively, were contoured by 1a single physician according to Radiation Therapy Oncology Group (RTOG) 1005 guidelines for all the CT datasets. The PTV_EVAL from this protocol was also contoured and was the PTV used for treatment planning. The PTV_EVAL is limited to exclude the PTV outside the ipsilateral breast, the 5mm of tissue under the skin, and most of the chest wall. Per RTOG 1005 the PTV_EVAL is used for dose constraints and coverage analysis. Treatment plans were created by 2 amedical single dosimetrists, one for each respective treatment method following RTOG 1005 recommendations and a series of dose delivery metrics. Following treatment planning, comparisons dosimetric comparisons were made regarding the two breast treatment methods. Conclusion: Field in Field and ISC treatment methods for left-sided, early stage breast cancer can result in dosimetric differences in radiation therapy. The FIF method may be advantageous when compared to ISC in increasing dose conformity while lowering dose to critical structures and healthy tissue. Key Words: Field- in- field, electronic compensation, irregular surface compensator, earlylow stage breast cancerIntroduction: In women, breast cancer has the highest incidence of all cancers in the United States at 125 cases per 100,000 women, per the Center for Disease Control. It is also the second deadliest cancer in women behind lung and bronchus cancer.1 Whole breast, or intact breast, radiotherapy is a common way to treat early stage breast cancer. Radiotherapy is the use of high energy x-ray beams to kill cancer cells while sparing the healthy tissue surrounding the tumor. Both FIF and ISC techniques are modern methods used in breast radiotherapy, as they use advanced technology to improve dose conformity while reducing dose to healthy tissues throughout treatment.2 Research has not yet shown a direct comparison between the 3D FIF and ISC techniques with modern planning technology to the whole breast. Multiple studies have found treatment differences when the PTV is determined by a GTV expansion, but not with a physician contoured PTV representative of the whole breast on the affected side. Irregular surface compensation and the FIF technique are used in whole breast therapy due to the way dose can be specially constructed and targeted by a dosimetrist. The FIF technique is a widely preferred method of delivering tangential whole breast radiation therapy by utilization of multi leaf collimation (MLC) field shaping. Open tangential fields are created by use of MLCs to carry deliver a mostmarjority of the dose. To further increase target dose, the FIF technique incorporates subfields with MLCs to block high dose regions, resulting in increased dose conformity. Many studies suggest that the FIF technique results in better dose homogeneity, reducing hot regions, and limiting dose to healthy tissue.3 Irregular surface compensation is a tangential, forward planning technique utilizing fluence.4 The modification of fluence is done performed by the MLC leaves which improves dose homogeneity when delivering treatment to an irregular surface, such as a breast. The ISC has been found to reduce hot regions of dose and acute toxicity in women, particularly those with larger breast and inferior tumors.5 By increasing dose homogeneity and reducing dose to healthy tissue, many post-treatment complications from breast radiotherapy can be reduced. Common post-treatment complications include tumor recurrence, chest wall recurrence, contralateral breast tumors, heart toxicity, and radiation pneumonitis.6 Guidelines in RTOG 1005 were followed for both target delineation and OAR dose constraints. A single physician drew all target volumes in this study.7Many studies that have demonstrated comparisons in common breast radiotherapy techniques, including FIF and ISC, have shown mixed results in terms of the best treatment planning method for early, tangential breast treatment.8,9 Sometimes, increased amounts of variability in the research could have swayed the accuracy of results10 in breast sizes with PTVs not drawn consistently, and tumors of variable stages. Various treatment machines, manufacturers, MLC sizes, and treatment energies are also mixed into the same studies, posing high variability in treatment planning results.2 Some research has found treatment differences when the PTV is determined by a GTV expansion, but not with a physician contoured PTV representative of the whole breast on the affected side.10 Treatment differences have also been found in studies comparing treatment methods where the treatment targets were site specific, rather than protocol consistent.2 Additionally, different dose algorithms and different TPSs have also been used in studies with a single patient population. The accuracy of correction factors and calculation methods can also lead to result inaccuracies. This case study A primary objective of this to limit variables within treatment planning to ensure the accuracy of the results. Common normalization methods were also used to provide a true comparison of the two techniques.The objective of this study was to perform a comparison between the FIF and ISC techniques in tangential 3D conformal, whole breast radiotherapy. By minimizing variables in the patient selection, target delineation, and planning process, the this study provideda a true comparison of two modern planning techniques was used to distinguish whether one technique was advantageous over the other. By using the sameWhile using the same controls within the study for patient population and dose delivery metrics, both treatment methods were compared. to the sameThis study aims to compare the contoured targets and OARs, the two planning methods can be compared regarding dose homogeneity, target coverage, maximum dose regions, and OAR doses for whole breast tangents. If one treatment method proves significantly better than the other, further research on a larger patient population will be needed to confirm the findings. Case Description:Patient Selection & Setupn Ten patients were selected retrospectively who were diagnosed with earlylow stage breast cancer ranging from DCIS to T2N0M0 in the left breast were retrospectively selected for this studyonly. Only patients with a lumpectomy procedure were selected so that the physician could delineate the lumpectomy cavity, or GTV. Left sided breast patients were selected so that breast tissue, heart, lung, and contralateral breast doses could all be analyzed and compared at the completion of treatment planning. The “bridge” separation, or distance between the medial and lateral borders was taken into consideration to avoid cases of larger breasted womenextreme s. Although variable breast sizes and lumpectomy site locations were used, the largest cases were avoided because there are other methods of immobilization and treatment setup for these patients.11All patientsThe patients selected patients underwent a free breathing CT simulation from a Phillips Brilliance large bore CT scanner with 3 mm slices at a single cancer center. Planning for each patient was completed utilizing a 3D, free breathing CT scan. All patients selected for thein this study were simulated in the same, or similar treatment position to further avoid variability in the research. The patient position during simulation was head first, supine with both arms up holding a T-grip. A breast board was table-indexed with a vacuum bag under the arms and head area; head tilted away from the affected side. A knee cushion was used with a ring placed around the feet to limit leg movement during treatment All patients having the patient’s head ede and tbeing (Figures 1-4). Free breathing was used to further emphasize the importance of target coverage and OAR avoidance, as well as to limit variability between the locations of target volumes and lungs in this study.. Target DelineationTo allow for a quantitative analysis of treatment plan quality, the GTV, PTV, andboth breast tissue of the affected breast (PTV), and the lumpectomy site (GTV), and the PTV_EVAL were contoured according to RTOG 1005 by a single1 physician following the 3D CT simulation using the Varian Eclipse TPS version 13.6. This version makes use of the Anisotropic Analytical Algorithm (AAA) for photon energies in this study. The targets used in this study align with target definitions in RTOG 1005.7 part 6.4.2 for “Lumpectomy GTV” and “Breast PTV Eval”.7 The lumpectomy GTV wasis contoured usingdefined as the excision cavity volume, lumpectomy scar, seroma, and/or extenextension of surgical clips. All patients in the study had a clearly identifiable lumpectomy bed (Figure 5). The PTV. The breast PTV_EVAL was drawn to include the palpable breast tissue, apparent glandular breast tissue, and the lumpectomy site. This contour was limited to 5mm from the skin and extendeds no deeper than the anterior surface of the ribs.7 (Figure 5).Both treatment volumes and the contralateral breast can be seen in Figure 5. Contoured OARs included the contralateral breast, ipsilateral lung, contralateral lung, and heart, again in accordance with RTOG 1005. The contralateral breast included visible glandular tissue delineated from the CT while following the RTOG Breast Atlas. All lung volumes were contoured with auto-segmentation and manual editing and verification. The heart was contoured from where the pulmonary trunk branches bifurcation into the left and right pulmonary arteries and extended to its most inferior region in the diaphragm or lower.7Treatment PlanningThe prescription and fractionation schedule in this study were consistent with Arm 1 of RTOG 1005, Standard Whole Breast Irradiation with Sequential Boost, delivering 50 GyGy) in 25 fractions of 2Gy, 5 days a week for the primary tangential plan to the whole breast. Only the primary plans of 50Gy were analyzed for this study to compare FIF and ISC treatment techniques due to the variability in boost treatment modalities at different treatment centers.are Both FIF and ISC techniques were planned for treatment on a Varian TrueBeam linear accelerator with the same MLC configuration. Both treatment machines had an equal number of 0.5cm and 1.0cm MLC leaves used in collimation. Treatment planning was completed by 2 dosimetrists total, one assigned to each treatment method. Field in field had access to 6 megavoltage megavoltage (MV), 10MV, and 15MV beam energies available for planning. The 10MV beam energy was left available for the field in field method because the dosimetrist was proficient in using 10MV at her treatment facility. Irregular surface compensation had 6MV and 15MV beam energies available. In this study, 6MV beams were required in both planning modalities, and higher energies were used to achieve planning outcomes. All planning was completed using Varian Eclipse version 13.6 TPS, utilizing AAA. Beam angles for target volume coverage were determined by the medical dosimetrists based on external patient contours, RTOG constraint recommendations, and the visual analysis of a reviewing physician. The PTV breast tissue sizesize, GTV location, and beam energy avaienergy availability also contributed to establishing gantry angles. Collimator angles for the primary treatment beams were consistent with 0 or 90 degrees but could be modified in the FIFs or ISC. Primary collimator angles were kept this way to ensure that the radiation field was consistent between both treatment modalities. To accurately compare both treatment methods, all plans were normalized to achieve 3 goals for the coverage to thespecifics regarding the PTV_EVAL and GTV: (1) the maximum permissible hot spot for any plan was 115%; (2) 95% of the PTV_EVAL was required to be covered by 95% of the prescription dose; (3) 100% of the GTV was to be covered by 99% of the prescription dose. To push both treatment methods capabilities, coverage requirements exceeded those of RTOG guidelines. Tcould not go over Additionally, bothisodoseisodoseThe medical dosimetrist is to choose a chose a normalization method value that achieved all 3 of these requirements, even if OAR dose constraints failed. There was no modification of target coverage doses in this study to accommodate OAR limitations . This is to help distinguish the capabilities of each treatment modality regarding target coverage and OAR avoidance. To allow for a comparison of treatment methods, all plans were normalized to achieve minimum coverage of all three requirements.Delivered doses to OARs were to not not exceed the regulations per the RTOG 1005 protocol or be kept as low as possible without sacrificing target coverage.. The contralateral breast was not to exceed 310 cGy anywhere, and no more than 5% of the tissue was to exceed 186cGy. Per RTOG, the volume of the ipsilateral lung receiving 20 Gy can was to be no more than 15% (V20 < 15%). Additionally, for the ipsilateral lung, the V10 must was to be less than 35% (V10 < 35%) and the V5 must bewas to be less than 50% (V5 < 50%). For the contralateral lung, 5Gy could not exceed 10% of the contoured organ (V5 < 10%). No more than 5% of the whole heart was to exceed 20Gy (V20 < 5%). Also, no more than 30% of the whole heart was to exceed 10Gy (V10 < 30%). The heart also had a mean dose limit of 400cGy.7 It is of moral responsibility of dosimetrists to ensure that OAR not only meet the regulations, but also are made as low as possible while meeting other metrics. The medical dosimetrists in this study ensured that OAR doses were as low as they could be given the target dose requirements. Plan Analysis and EvaluationGiven the range of differences between FIF and ISC dosimetry, the same patient was planned in different ways depending on several factors. The dosimetrists were expected to make the best possible treatment plan using their respected method despite having differences in their own planning processes. The separation, or distance between the medial and lateral borders of the treatment field, location of the GTV, and overall size of the breast were key components in how each medical dosimetrist completed their treatment plans. Table 1 shows the bridge distances and volumetric differences of the PTV_Eval and GTV in all patients in the study. Tables 2-5 describe the results of the treatment planning for both techniques. Target coverages, dose conformity, and OAR dose statistics are shown. All plans were normalized to meet the coverage conditions mentioned earlier. Every plan was normalized so that 100% of the GTV was covered by 99% of the prescribed dose in order to meet all conditions. Following normalization, the ISC technique had an average maximum point dose of 105.73%, with FIF having 106.35%. This result indicated that the ISC technique was less than 1% less hot than the FIF technique. Additionally, the FIF method averaged 97.4% coverage to 95% of the PTV_Eval, with ISC averaging 97.2% isodose. With a 0.2% difference, both maximum point doses and target coverages were only marginally different, indicating that neither technique posed an advantage to the other in terms of hot spots, PTV_Eval, and GTV coverage for a primary breast radiation plan (Table 2). Overall dose conformality was evaluated using a conformity index (CI). The CI was implemented into the study to evaluate PTV_Eval coverage based on the 95% isodose line. The conformity index was defined as a ratio between the volume covered by the reference isodose line and the target volume. This definition was taken from RTOG and ICRU guidelines and was presented by the equationCI = VRI / TVwhere VRI = reference isodose volume and TV = target volume. A CI equal to 1 corresponds to the ideal dose coverage. The further the CI is from 1, poorer dose conformity is apparent as the irradiated volume further exceeds the target volume and is being deposited in healthy tissue.12 In this study, all CI values were greater than 1 because of mandatory and similar plan normalization. The FIF technique produced plans with an average CI of 1.522, whereas ISC produced plans with a CI of 1.721 on average. The study indicated that the FIF technique was able to achieve similar coverage of target volumes with better dose conformality (Table 2).Contralateral breast and contralateral lung maximum doses were evaluated for the maximum dose delivered to these structures in cGy based on dose volume histograms (DVH) in each plan. Because these doses were relatively low as the structures are on the opposite side of the body, maximum doses were evaluated rather than mean dose. With the FIF technique, the average maximum point dose to the contralateral breast was 165cGy, with the highest dose in Patient H at 299cGy. The average maximum dose to the contralateral breast with the ISC technique was 327.4cGy, with a highest dose also in Patient H as 664cGy. This resulted in the FIF technique having a 49.5% lower dose to the contralateral breast. Following plan normalization, the ISC technique did not meet the constraint of 310cGy in 6 pateints, where the FIF technique had zero patients fail that constraint (Table 3). The average maximum dose to the contralateral lung for the FIF and ISC techniques was 98.4cGy and 196.6cGy, respectively. The FIF average max dose to the contralateral lung was 50.1%, or 98.2cGy less. In both treatment methods, all patients passed the V5 < 10% constraint (Table 3). The research suggests that the FIF technique may be advantageous when compared to the ISC technique regarding contralateral OAR constraints and overall doses.All treatment plans passed the 3 ipsilateral lung constraints. The V20, V10, and V5 for the FIF technique on average was 5.6%, 9.4%, and 15.7%, respectively. The ISC technique yielded 11.3%, 16.6%, and 26% for the same ipsilateral lung constraints. The FIF technique was 5.7% lower, 7.2% lower, and 10.3% lower when evaluating the V20, V10, and V5 of the ipsilateral lung when compared with the ISC technique (Table 4). The research suggests that the FIF method may be better at keeping the ipsilateral lung dose lower than treatments utilizing the ISC technique. All treatment plans passed the 3 heart constraints as well. The average V20 of the heart for the FIF technique was .7% and for the ISC technique was .9%. The averagV10 of the heart for the FIF technique was 1.38% and for the ISC technique was 1.73%. There was less than a .5% difference between the two treatment methods for both constraints. The average mean dose of the heart was 148.9cGy for FIF and 192cGy for ISC, resulting in a difference 43cGy on average in favor of the FIF technique. The research suggests that heart dose may be kept marginally lower with the FIF technique without making a tangible clinical difference as all plans passed the constraint by a large margin in both techniques (Table 5).Overall, both treatment methods were effective in meeting all the coverage requirement and most of the dose constraints as only the contralateral breast maximum point dose was not met by the ISC method in all cases. Considering that all plans were forcibly normalized to deliver 99% coverage to the entire GTV, it was expected that some dose constraints would fall out of spec. The largest takeaways from the results include the differences in dose conformity, contralateral OAR doses, and ipsilateral lung doses. The FIF method consistently provided plans with a better CI without sacrificing maximum hot spots and target volume coverage. A CI in between 1 and 2 is considered in accordance with RTOG standards, so in only one case dose conformity deviated from protocol standards.12 It also produced plans that gave about 50% dose to both the contralateral breast and contralateral lung. Neither planning method was unable to produce acceptable plans based on RTOG guidelines, so the research may only suggest that already acceptable treatment plans can be improved by using the FIF method with 6MV, 10MV, and 15MV treatment beams (Tables 1-4).ConclusionWith so many variables in previous studies comparing different methods of whole breast radiation therapy, this study emphasized a comparison with limited variability. By using the same treatment machines, planning systems, and patient datasets, the treatment plans in this study were extremely limited in variability. With the use of a single protocol and physician to outline PTVs, GTVs, and OAR, the analysis of dose delivery was expected to be more accurate than previous research. The only notable variables in this study include having different dosimetrists perform each method of planning and the option to use 10MV beams in the FIF treatment technique. The research was intended to represent a wide range of the left-sided, early stage breast cancer patient population, as the study utilized retrospective treatment planning CT scans of patients with different breast volumes, body sizes, and lumpectomy cavity locations.When variables are limited, and normalization methods are consistent between planning techniques, the research suggests that the FIF method may be advantageous to the ISC method in primary, free-breathing radiotherapy for early stage breast cancer for a variety of patients. Both methods were extremely comparable to each other in terms of maximum point dose and target volume coverage. The maximum hot spot was well below the limit of 115% in both treatment techniques even with the entire GTV covered by the 99% isodose line in all cases. In terms of dose conformity of the 95% isodose line, the FIF technique was able to provide plans with a CI much closer to 1 than ISC. It was likely that because the 95% line was tighter around the PTV when using the FIF technique that the corresponding OAR doses were also lower. Based on the study findings, a similar study with a larger number of patients may further suggest that the FIF technique can be advantageous to ISC. Further research should include not only a larger study population, but also patients with larger bridge separations and amounts of breast tissue. The differences in both contralateral and ipsilateral lung and heart doses may be a result of patient respiration, so the use of deep inspiration breath hold (DIBH) may yield different results regarding dose to these OARs. Because DIBH is practiced at many cancer treatment facilities for left-sided breast cancer radiotherapy, a similar study involving this technique would extend this research. ReferencesBreast Cancer Statistics. Centers for Disease Control and Prevention Web site. . Updated June 12, 2018. Accessed July 23rd, 2018Koivumaki?T,?Fogliata?A,?Zeverino?M, et al.?Dosimetric?evaluation of modern radiation therapy techniques for left breast in deep-inspiration breath-hold.?Physica?Medica.?2018;45:82-87.?? H, Hayashi S, Hoshi H. Determination of the optimal method for the field-in-field technique in breast tangential radiotherapy. J RRSRadiat Res. 2014;55(;4):769-773. M. An overview of electronic tissue?compensation (ECOMP) for breast radiotherapy. Poster presented at: Combined Scientific Meeting; 2014; Melbourne, Australia.CSM.?2014;R-0170.?, James HV. Irregular surface compensation for radiotherapy of the breast: Correlating depth of the compensation surface with breast size and resultant dose distribution. Br J?Radiol. 2010;83(986):159-165.?, et al.?Radiation induced pneumonitis following whole breast radiotherapy treatment in early breast cancer patients treated with breast conserving surgery: A single institution study.?Hippokratia.?2013;17(3):233-238. . Accessed July 23, 2018. Vicini FA, Freedman GM, White JR, et al. A phase III trial of accelerated whole breast irradiation with hypofractionation plus concurrent boost versus standard whole breast irradiation plus sequential boost for early-stage breast cancer. Radiation Therapy Oncology Group (RTOG). . Updated 2014. Accessed July 23rd, 2018.Al-Rahbi?ZS, Ravichandran R,?Binukumar?JP, Davis CA,?Satyapal?N, Al-Mandhari?Z. A?dosimetric?comparison of radiotherapy techniques in the treatment of carcinoma of breast.?J Cancer?Ther.?2013;4:10-17. N,?Torfeh?T,?Sheim?S, Petric P,?Paloor?S,?Hammoud?R. Indications for intensity modulated radiation therapy using field-in-field and electronic compensator for the treatment of large left breast volumes.?Phy Med.?2016;32(3):322-323.? F, Nao K, Hiroyuki H, Hiroshi K, Haruyuki F. Improvement of dose distribution with irregular surface compensator in whole breast radiotherapy.?J Med Phys. 2013;38(3):115-119. LM, Cohen R, Sopka DM, et al. Effect of bra use during radiation therapy for large-breasted women: Acute toxicity and treated heart and lung volumes. Practical Rad Onc. 2013;3(1):9-15. D, Smickovska S, Lazarevska E. Conformity index and homogeneity index of the postoperative whole breast radiotherapy. Open Access Maced J Med Sci. 2017;5(6):736-739. 1. An image showing how the arms and torso were positioned in CT simulation1343025241935Figure 2. An image showing how hands were positioned for all patients. The T-grip could be moved for comfort.2676525544830Figure 3. An image showing the torso from a lateral view in the treatment position, with the breast board visible.Figure s 1-4. An Eexample of how the legs and feet were positioned for all patients in this study. of how all patients were simulated and positioned at a single site, but for the left breast. Figure 5. Patient 8 –A visual representation of GTV, PTV_EVAL, and contralateral breast contoured by the physician. TablesTable 1. Information regarding the patients’ separation and GTV and PTV_EVAL sizes.Patient Maximum Bridge Separation (cm)GTV Volume (cc) PTV_Eval Volume (cc) B24.5? 37.2 1085.7 C19.7? 16.0 490.5 D26.9? 24.4 1058.0 E22.5? 22.7 608.8 F19.3 21.3 736.0 H24.2? 27.7 849.3 K26.9? 51.6 1460.8 R22.1? 31.5 781.1 S20.6? 11.6 211.7 T23.3? 4.2 607.4 Table 2. A comparative table of target coverages and dose conformity for both treatment methods.Maximum Point Dose?PTV_Eval?Coverage(% of PTV covered by % of Rx)?GTV Coverage(% of GTV covered by % of Rx)??Conformity Index (CI)*?Treatment Planning TechniqueFIFISCFIFISCFIFISCFIFISCPatient B? 106.7%106.1%?95% of 97%95% of 96%All treatment plans were normalized to 100% of GTV covered by 99% of Rx?1.331.47Patient C? 104.7%107.1%?95% of 99%95% of 99%?1.411.70Patient D??107.0%107.1%?95% of 96%95% of 98%?1.361.81Patient E??107.0%104.8%?95% of 98%95% of 96%?1.341.55Patient F??104.8%104.5%?95% of 97%95% of 98%?1.221.47Patient H??106.7%105.4%?95% of 97%95% of 97%?1.351.49Patient K??108.9%104.6%?95% of 99%95% of 95%?1.381.34Patient R??107.5%106.6%?95% of 99%95% of 99%?1.451.77Patient S??104.4%105.8%?95% of 95%95% of 99%?2.902.85Patient T??105.8%105.3%?95% of 97%95% of 95%?1.481.76Average106.35%105.73%97.4%97.2%1.5221.721DifferenceThe maximum point dose is 0.62% less for ISC than FIFThe PTV_Eval coverage at 95% is 0.02% higher for FIF than ISCThe CI is 0.2 lower for FIF than ISCTable 3. A comparison of Contralateral Breast and Contralateral Lung dose for both treatment methods.Contralateral Breast?Max Dose (cGy) (Max < 310cGy)Contralateral Lung Max Dose (cGy)?(V5 < 10%) TechniqueFIFISCFIFISCPatient B?248332176223Patient C?133348103253Patient D?1593755556Patient E?101247108212Patient F?80822435Patient H?299664100137Patient K?1654203251Patient R?2633962987Patient S?88231243570Patient T?114179114262Average165327.498.4196.6CommentFIF average max dose to contralateral breast tissue is 162.4 cGy or 49.5% lessFIF average max dose to contralateral lung is 98.2 cGy or 50.1% lessTable 4. A comparison Ipsilateral Lung dose for both treatment methods.Ipsilateral Lung V20 < 15 Volume (%) Ipsilateral Lung V10 < 35 Volume (%)Ipsilateral Lung V5 < 50 Volume (%) TechniqueFIFISCFIFISCFIFISCPatient B?91113172227Patient C?4128191630Patient D?310515924Patient E?91412201932Patient F?2639614Patient H?71311191928Patient K?387131623Patient R?6139171625Patient S?71310171624Patient T?61316201833Average5.611.39.416.615.726NotesFIF -5.7 %FIF -7.2 %FIF -10.3 %Table 5. A comparison of Heart dose for both treatment methods.HeartV20 < 5 Volume (%)HeartV10 < 30 Volume (%)HeartMean Dose (cGy) < 400cGyTechniqueFIFISCFIFISCFIFISCPatient B?.5.021.3137135Patient C?000.188127Patient D?1.722.0163177Patient E?.4.6.81.4129197Patient F?.91.422.5171223Patient H?.3.6.81.4153203Patient K?.04.6.21.5122162Patient R?22.533.6210288Patient S?12.423.6175253Patient T?1.52.9141155Average.7.91.381.73148.9192FIF -.2 %FIF -.35 %FIF -43 cGy ................
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