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Comparison of Two Different Respiratory Monitoring Systems Using External Surrogates for Respiratory-Guided Radiation Therapy
International Journal of Radiation Oncology Biology Physics
E690
Abstract 3644; Table Analysis of the impact of daily setup and anatomy variations for Lung SBRT plans. The intended and accumulative dose distribution is indicated as “Planned” and “Delivered”, respectively Patient
D95(PTV) Gy
Proton Plan – Planned (Delivered) 1 50 (38.7) 2 50 (45.5) 3 50 (46.85) Photon Plan – Planned (Delivered) 1 50 (48.0) 2 50 (49.5) 3 50 (49.9)
D95(ITV) Gy
V50Gy(ITV) %
Cordmax Gy
Heartmean Gy
Lungmean Gy
50 (43.1) 50.7 (48.3) 50 (48.9)
97.4 (36.4) 99.7 (82.5) 93.0 (45.5)
0 (0) 1.8 (1.8) 0.1 (0.1)
0 (0) 0.4 (0.4) 0 (0)
1.7 (1.4) 3.2 (3.2) 0.8 (0.8)
51.8 (51.4) 52.1 (51.5) 53.2 (52.9)
99.8 (99.3) 100 (99.6) 100 (100)
8.4 (8.2) 12.0 (11.9) 5.9 (5.4)
1.7 (1.7) 6.8 (6.9) 0.1 (0.1)
4.6 (4.5) 6.5 (6.6) 2.2 (2.2)
prescription dose was reduced from 96.7% of the volume to 54.8% for proton plans, and the reduction is less than 0.5% for photon plans. On the other hand, the proton doses to OARs are not changed significantly for all patients. Conclusion: The target coverage was significantly affected by daily setup and anatomy variations for proton plans, while impact is negligible for photon plans. The PTV expansion currently used for photon plans may not be appropriate for proton plan design. Author Disclosure: Y. Lin: None. M. Zhu: None. Q. Wu: None. F. Yin: Patent/License Fees/Copyright; Varian Medical Systems, Inc. The business and affairs of the ISRS will be managed by or under the direction of the Board of Directors, which will may exercise all such powers of the ISRS and take all lawful actions not prohibited by the Bylaws.; The International Stereotactic Radiosurger Society. organize act.
3645 Comparison of Photon and Proton Liver SBRT Plan Quality Affected by Daily Positioning and Anatomic Deviations Y. Lin,1 M. Fang,1,2 M. Zhu,3 Q. Wu,1 and F.F. Yin1; 1Duke University Medical Center, Durham, NC, 2Zhejiang Provincial People’s Hospital, hangzhou, China, 3University of Maryland, Baltimore, MD Purpose/Objective(s): To quantify the impact of daily setup and anatomy variations on both the proton and photon plan for liver SBRT treatment. Materials/Methods: Two liver SBRT patients previously treated using photon techniques were analyzed. For photon plans, IMRT or VMAT techniques were used to generate conformal dose distribution to the planning target volume (PTV), which is a 1 cm expansion to the internal target volume (ITV). The same target and organs at risk (OARs) used in photon plans were used to generate pencil beam scanning (PBS) proton plans. Two to three beams with multi-field optimization techniques were used. Both photon and proton plans were normalized so that 100% prescription dose covers 95% of PTV volume. The prescription dose is 54 Gy (RBE) to the targeted in 3 fractions or 50 Gy (RBE) in 5 fractions. The daily anatomy and setup variations were captured using clinical CBCT. Currently, we only included patients treated with free-breathing technique. The planning CT was mapped to daily CBCT through deformable image registration. The planned doses were recalculated on each deformed planning CT and the accumulative dose distribution taking into account of the daily setup and anatomy variations over the treatment course were evaluated and compared to the intended dose distribution.
Results: The results are shown in the Table. The proton plans show significantly lower OAR doses for both patients. This is due to the superior physical characteristic of proton beam which completely stops beyond Bragg Peak. Both photon and photon plans showed comparable robustness in terms of target coverage as well as OAR sparing during the course of treatment. For instance, the D95 for ITV was only reduced by average of less than 1% for both proton and photon plans. Conclusion: The proton plan shows superior OARs sparing and similar target coverage compared to photon plan. This is particularly important for liver SBRT treatment since the effective liver volume irradiated is highly associated with toxicity and limits the dose that can be prescribed to the target. For both techniques, the doses to target as well OARs are not significantly affected by daily setup and anatomy variations. Author Disclosure: Y. Lin: None. M. Fang: None. M. Zhu: None. Q. Wu: None. F. Yin: Patent/License Fees/Copyright; Varian Medical Systems, Inc. The business and affairs of the ISRS will be managed by or under the direction of the Board of Directors, which will may exercise all such powers of the ISRS and take all lawful actions not prohibited by the Bylaws; The International Stereotactic Radiosurger Society. organize act.
3646 Comparison of Two Different Respiratory Monitoring Systems Using External Surrogates for Respiratory-Guided Radiation Therapy J. Liu, T. Lin, J. Fan, L. Chen, R.A. Price Jr, Y. Dong, and C.M.C. Ma; Fox Chase Cancer Center, Philadelphia, PA Purpose/Objective(s): Two different respiratory monitoring systems using external surrogates are used in our institution for four-dimensional computed tomography (4DCT). The RPM system tracks two infrared reflecting markers placed on the abdomen to measure the abdominal surface movement as the respiratory signal. The Anzai belt employs a pressure sensor on the abdomen to measure the pressure change during breathing. The objective of this study was to compare these two systems in the respiratory signal and the 4DCT images reconstructed based on both systems and to assess the effect of mixed use of different systems in 4DCT imaging for treatment planning and in respiratory gated radiotherapy treatment. Materials/Methods: The respiratory signals were acquired simultaneously using both surrogates for the same patient during the 4DCT scan on a Siemens SOMATOM Definition AS (Open 20 RT). Ten patients with regular breathing traces were included for data analysis. Comparisons were
Abstract 3645; Table Analysis of the impact of daily setup and anatomy on photon and proton liver SBRT plans. The intended dose distribution is indicated as “Planned”, and the accumulative dose distribution over the course of treatment is indicated as “Delivered”. VPI indicated the volume receiving prescription dose. Patient
D95(PTV) Gy
Proton Plan – Planned (Delivered) 1 54 (50.4) 2 50 (45) Photon Plan – Planned (Delivered) 1 54 (51.9) 2 50 (42.5)
D95(ITV) Gy
VPI(ITV) %
Cordmax Gy
(Liver-ITV)mean
Livermean
54.7 (54.6) 50 (49.8)
100 (99.3) 95 (92.1)
0 (0) 0.1 (0.2)
4.4 (4.7) 4.4 (4.2)
7.1 (7.3) 9.2 (8.9)
56.1 (56.0) 51.8 (51.6)
100 (100) 100 (98.6)
8.5 (8.8) 16.9 (15.2)
10.8 (11.3) 10.1 (10.1)
13.3 (13.7) 14.4 (14.3)
Volume 99 Number 2S Supplement 2017
Poster Viewing E691
made between the two breathing traces to evaluate the phase shift in signal acquisition and the difference in breathing patterns. Two sets of 4DCT images with the same raw sinogram data for the same patient were reconstructed using the respiratory signals acquired by both systems. An amplitude-based sorting algorithm was applied to obtain the images of ten respiratory phases. The images reconstructed from the two different respiratory signals were compared for each individual phase. Image segmentation was performed in the treatment planning system to assess the differences in lung contours and the position of the diaphragm. Results: The phase shifts calculated by the time latency at the end inhalation between the two breathing traces were consistent for all ten patients and were measured as 0.20.1 seconds. The breathing trace measured by the Anzai pressure sensor had a steeper falloff curve during exhalation than the RPM trace measured by the abdominal surface movement. In the 4DCT images reconstructed separately, changes in lung contouring and shifts in position of diaphragm were observed in each individual phase. Largest shifts of more than 5mm in the diaphragm location were found in phases between 40% exhalation and 20% inhalation. Conclusion: Phase shifts between breathing traces and differences in breathing patterns as measured by the abdominal pressure change and surface displacement were observed in this study. The internal thoracic motion during 4DCT scan can have different correlation relationships with different respiratory monitoring systems using external surrogates. This implicates that mixed use of different respiratory monitoring systems in 4DCT imaging for treatment planning and in respiratory gated treatment delivery may result in errors in the dose distribution received by the patient. Author Disclosure: J. Liu: None. T. Lin: None. J. Fan: None. L. Chen: Fox Chase Cancer Center. R.A. Price: None. Y. Dong: None. C. Ma: Research Grant; Accuray. committee members; AAPM.
IMRT (0.7660.055, 7598.5167.9, p<0.01), cVMAT (0.7890.045, 7507.7107.8, p<0.05) and ncVMAT (0.7710.049, 7632.8184.7, p<0.01) respectively. Furthermore, MRT improved dose sparing of lens (D1%Z 633.947.1) compared with IMRT (723.168.7,p<0.01), cVMAT (686.030.4, p<0.01) and ncVMAT (721.757.9,p<0.01). MRT reduced optic nerves dose (D1%Z 4547.5678.3) compared with IMRT (5434.0372.3,p<0.01), cVMAT (4683.8569.4,p<0.05) and ncVMAT (4666.5501.2, p<0.05;) However, the dose of brain stem was increased in MRT (D1%Z4117.9159.1) but kept in the nomal threshold compared with IMRT (3114.5201.3,p<0.01), cVMAT (2735.2253.1, p<0.01) and ncVMAT (2872.0192.2,p<0.01). Additionally, MRT increased optic chiasm dose (D1%Z4831.9231.2) compared with IMRT (3828.6307.8, p<0.01), cVMAT (4628.2221.4, p<0.01) and ncVMAT (3889.6183.5, p<0.01). MRT greatly reduced MU (376.223.7) compared with IMRT (895.359.4, p<0.01), cVMAT (403.928.6,p<0.05) and ncVMAT (398.020.3,p<0.05). Conclusion: MRT is superior to IMRT or VMAT for SNC for better target coverage and protection of lens and optic nerves, reduced MU. The dose of brain stem and optic chiasm is slightly increased but kept in the nomal threshold. MRT is a good option for SNC. Author Disclosure: M. Liu: None. H. Wang: None. B. Liu: None. W. Xia: None. Y. Gao: None. W. Shi: None. L. Dong: None.
3647
Purpose/Objective(s): The definite indication of flattening filter free Rapid-ARC is still unclear yet. Our study compared the dose distribution of target volumes, dose fall, protection of normal organs at risk (OAR) and monitor unit (MU) of 3 radiotherapy techniques (Rapid-ARC FFF, IMRT FF and Rapid-ARC FF) in superficial tumors of head and neck. Materials/Methods: Nine patients were enrolled. The three RT plans mentioned above were designed for each patient with 6MV X-ray. The prescribed dose was 54Gy/30f/1.8Gy to PTV concurrent with 64.2Gy/30f/ 2.14Gy to PGTV. The target volume coverage indicators included conformity and homogeneity index (CI, HI). The dose fall indicators included V40 and V20 (the covered volume by 40Gy and 20Gy, respectively). OARs included the brainstem and spinal cord. All the optimized parameters and target values for plans were consistent. Results: Rapid-ARC FFF provided significantly improved conformity (0.7620.013) and homogeneity (1.0730.022) of PGTV than IMRT FF (CIZ 0.6770.076, p<0.01; HIZ 1.1160.048, p<0.05), and RapidARC FF (CIZ 0.7170.077, HIZ 1.0800.018, p<0.05). Rapid-ARC FFF has a better CI (0.8000.049) of PTV compared with IMRT FF (0.7540.071, p<0.05) and Rapid-ARC FF (0.7680.074, p<0.05) respectively.Furthermore, RapidArc FFF had a rapider dose fall. RapidArc and FFF remarkably reduced V40 (445.85213.60cm3) V20(972.42428.70cm3) compared with IMRT FF (V40Z 472.62219.63cm3, V20Z 1000.18445.74cm3, p<0.01) and RapidARC FF (V40Z 454.51221.50cm3, V20Z 1018.17475.67cm3, p<0.01). However, the dose of brain stem was increased in RapidArc FFF (D1ccZ2669.46927.05cGy) but kept in the nomal threshold compared with IMRT FF (2593.97872.12cGy, p<0.05) and Rapid-ARC FF (2656.97909.73cGy,p<0.05). Similarly, the dose of cord was increased in RapidArc FFF (D1ccZ3031.25438.77cGy) but kept in the nomal threshold compared with IMRT FF (3027.76426.03cGy,p<0.05) and Rapid-ARC FF (3025.33487.39cGy,p<0.05). RapidArc FFF greatly reduced MU (344.0040.62) compared with IMRT FF (613.50100.06, p<0.01) but slightly increased MU compared with RapidArc FF (325.7531.15,p<0.05).
A Novel Mixed Radiation Therapy Technique For Sinonasal Cancer: Dosimetric Study To Determine the Best Plan M. Liu, H. Wang, B. Liu, W. Xia, Y. Gao, W. Shi, and L. Dong; Department of Radiation Oncology, The First Hospital, Jilin University, Changchun, China Purpose/Objective(s): Radiotherapy (RT) is essential for malignancies of the nasal cavity and paranasal sinuses (sinonasal cancer [SNC]). However, RT plan is challenging for high prescribed dose and close proximity of critical structures. Here, we developed a novel mixed RT (MRT) plan consisting of one 3D-CRT and two-arc VMAT fields and compared the dose distribution of target volumes, protection of normal organs at risk (OAR) and monitor unit (MU) of four radiotherapy techniques (MRT, noncoplanar IMRT, coplanar and non-coplanar VMAT[cVMAT, ncVMAT]). Materials/Methods: Thirteen patients were enrolled. The four RT plans mentioned above were designed for each patient with 6MV X-ray. The prescribed dose was 59.4Gy/33f/1.8Gy to PTV concurrent with 69.96Gy/ 33f/2.12Gy to PGTV. The target volume coverage indicators included conformity and homogeneity index (CI, HI), D1% and D99%. OARs included the lens, brainstem, optic nerves and chiasm. All the optimized parameters and target values for plans were consistent. Results: MRT provided improved conformity (0.8250.041) and homogeneity (1.0660.015) of PGTV than IMRT (CIZ 0.7930.042, HIZ 1.1170.018, p<0.05), cVMAT (CIZ 0.8200.037, HIZ 1.0710.031, p<0.05), and ncVMAT (CIZ 0.8010.050, HIZ 1.0980.026, p<0.05). The dose unit was cGy. MRT also reduced D1% of PGTV significantly (7470.5113.6) compared with IMRT (7635.7189.8,p<0.01), cVMAT (7571.0109.4,p<0.05) and ncVMAT (7697.7200.1,p<0.01). MRT increased D99% of PGTV remarkably (6529.7108.4) compared with IMRT (6347.6175.2,p<0.01), cVMAT (6507.5111.9,p<0.05) and ncVMAT (6267.3156.7,p<0.01). MRT has a significantly better CI (0.8070.039) and reduced D1% (7436.1112.3) of PTV compared with
3648 Dosimetric Analysis of Radiation Therapy Plans With or Without Flattening Filter in Superficial Tumors of Head and Neck M. Liu, H. Wang, B. Liu, K. Chen, Y. Shi, C. Ge, and L. Dong; Department of Radiation Oncology, The First Hospital, Jilin University, Changchun, China
E690
Abstract 3644; Table Analysis of the impact of daily setup and anatomy variations for Lung SBRT plans. The intended and accumulative dose distribution is indicated as “Planned” and “Delivered”, respectively Patient
D95(PTV) Gy
Proton Plan – Planned (Delivered) 1 50 (38.7) 2 50 (45.5) 3 50 (46.85) Photon Plan – Planned (Delivered) 1 50 (48.0) 2 50 (49.5) 3 50 (49.9)
D95(ITV) Gy
V50Gy(ITV) %
Cordmax Gy
Heartmean Gy
Lungmean Gy
50 (43.1) 50.7 (48.3) 50 (48.9)
97.4 (36.4) 99.7 (82.5) 93.0 (45.5)
0 (0) 1.8 (1.8) 0.1 (0.1)
0 (0) 0.4 (0.4) 0 (0)
1.7 (1.4) 3.2 (3.2) 0.8 (0.8)
51.8 (51.4) 52.1 (51.5) 53.2 (52.9)
99.8 (99.3) 100 (99.6) 100 (100)
8.4 (8.2) 12.0 (11.9) 5.9 (5.4)
1.7 (1.7) 6.8 (6.9) 0.1 (0.1)
4.6 (4.5) 6.5 (6.6) 2.2 (2.2)
prescription dose was reduced from 96.7% of the volume to 54.8% for proton plans, and the reduction is less than 0.5% for photon plans. On the other hand, the proton doses to OARs are not changed significantly for all patients. Conclusion: The target coverage was significantly affected by daily setup and anatomy variations for proton plans, while impact is negligible for photon plans. The PTV expansion currently used for photon plans may not be appropriate for proton plan design. Author Disclosure: Y. Lin: None. M. Zhu: None. Q. Wu: None. F. Yin: Patent/License Fees/Copyright; Varian Medical Systems, Inc. The business and affairs of the ISRS will be managed by or under the direction of the Board of Directors, which will may exercise all such powers of the ISRS and take all lawful actions not prohibited by the Bylaws.; The International Stereotactic Radiosurger Society. organize act.
3645 Comparison of Photon and Proton Liver SBRT Plan Quality Affected by Daily Positioning and Anatomic Deviations Y. Lin,1 M. Fang,1,2 M. Zhu,3 Q. Wu,1 and F.F. Yin1; 1Duke University Medical Center, Durham, NC, 2Zhejiang Provincial People’s Hospital, hangzhou, China, 3University of Maryland, Baltimore, MD Purpose/Objective(s): To quantify the impact of daily setup and anatomy variations on both the proton and photon plan for liver SBRT treatment. Materials/Methods: Two liver SBRT patients previously treated using photon techniques were analyzed. For photon plans, IMRT or VMAT techniques were used to generate conformal dose distribution to the planning target volume (PTV), which is a 1 cm expansion to the internal target volume (ITV). The same target and organs at risk (OARs) used in photon plans were used to generate pencil beam scanning (PBS) proton plans. Two to three beams with multi-field optimization techniques were used. Both photon and proton plans were normalized so that 100% prescription dose covers 95% of PTV volume. The prescription dose is 54 Gy (RBE) to the targeted in 3 fractions or 50 Gy (RBE) in 5 fractions. The daily anatomy and setup variations were captured using clinical CBCT. Currently, we only included patients treated with free-breathing technique. The planning CT was mapped to daily CBCT through deformable image registration. The planned doses were recalculated on each deformed planning CT and the accumulative dose distribution taking into account of the daily setup and anatomy variations over the treatment course were evaluated and compared to the intended dose distribution.
Results: The results are shown in the Table. The proton plans show significantly lower OAR doses for both patients. This is due to the superior physical characteristic of proton beam which completely stops beyond Bragg Peak. Both photon and photon plans showed comparable robustness in terms of target coverage as well as OAR sparing during the course of treatment. For instance, the D95 for ITV was only reduced by average of less than 1% for both proton and photon plans. Conclusion: The proton plan shows superior OARs sparing and similar target coverage compared to photon plan. This is particularly important for liver SBRT treatment since the effective liver volume irradiated is highly associated with toxicity and limits the dose that can be prescribed to the target. For both techniques, the doses to target as well OARs are not significantly affected by daily setup and anatomy variations. Author Disclosure: Y. Lin: None. M. Fang: None. M. Zhu: None. Q. Wu: None. F. Yin: Patent/License Fees/Copyright; Varian Medical Systems, Inc. The business and affairs of the ISRS will be managed by or under the direction of the Board of Directors, which will may exercise all such powers of the ISRS and take all lawful actions not prohibited by the Bylaws; The International Stereotactic Radiosurger Society. organize act.
3646 Comparison of Two Different Respiratory Monitoring Systems Using External Surrogates for Respiratory-Guided Radiation Therapy J. Liu, T. Lin, J. Fan, L. Chen, R.A. Price Jr, Y. Dong, and C.M.C. Ma; Fox Chase Cancer Center, Philadelphia, PA Purpose/Objective(s): Two different respiratory monitoring systems using external surrogates are used in our institution for four-dimensional computed tomography (4DCT). The RPM system tracks two infrared reflecting markers placed on the abdomen to measure the abdominal surface movement as the respiratory signal. The Anzai belt employs a pressure sensor on the abdomen to measure the pressure change during breathing. The objective of this study was to compare these two systems in the respiratory signal and the 4DCT images reconstructed based on both systems and to assess the effect of mixed use of different systems in 4DCT imaging for treatment planning and in respiratory gated radiotherapy treatment. Materials/Methods: The respiratory signals were acquired simultaneously using both surrogates for the same patient during the 4DCT scan on a Siemens SOMATOM Definition AS (Open 20 RT). Ten patients with regular breathing traces were included for data analysis. Comparisons were
Abstract 3645; Table Analysis of the impact of daily setup and anatomy on photon and proton liver SBRT plans. The intended dose distribution is indicated as “Planned”, and the accumulative dose distribution over the course of treatment is indicated as “Delivered”. VPI indicated the volume receiving prescription dose. Patient
D95(PTV) Gy
Proton Plan – Planned (Delivered) 1 54 (50.4) 2 50 (45) Photon Plan – Planned (Delivered) 1 54 (51.9) 2 50 (42.5)
D95(ITV) Gy
VPI(ITV) %
Cordmax Gy
(Liver-ITV)mean
Livermean
54.7 (54.6) 50 (49.8)
100 (99.3) 95 (92.1)
0 (0) 0.1 (0.2)
4.4 (4.7) 4.4 (4.2)
7.1 (7.3) 9.2 (8.9)
56.1 (56.0) 51.8 (51.6)
100 (100) 100 (98.6)
8.5 (8.8) 16.9 (15.2)
10.8 (11.3) 10.1 (10.1)
13.3 (13.7) 14.4 (14.3)
Volume 99 Number 2S Supplement 2017
Poster Viewing E691
made between the two breathing traces to evaluate the phase shift in signal acquisition and the difference in breathing patterns. Two sets of 4DCT images with the same raw sinogram data for the same patient were reconstructed using the respiratory signals acquired by both systems. An amplitude-based sorting algorithm was applied to obtain the images of ten respiratory phases. The images reconstructed from the two different respiratory signals were compared for each individual phase. Image segmentation was performed in the treatment planning system to assess the differences in lung contours and the position of the diaphragm. Results: The phase shifts calculated by the time latency at the end inhalation between the two breathing traces were consistent for all ten patients and were measured as 0.20.1 seconds. The breathing trace measured by the Anzai pressure sensor had a steeper falloff curve during exhalation than the RPM trace measured by the abdominal surface movement. In the 4DCT images reconstructed separately, changes in lung contouring and shifts in position of diaphragm were observed in each individual phase. Largest shifts of more than 5mm in the diaphragm location were found in phases between 40% exhalation and 20% inhalation. Conclusion: Phase shifts between breathing traces and differences in breathing patterns as measured by the abdominal pressure change and surface displacement were observed in this study. The internal thoracic motion during 4DCT scan can have different correlation relationships with different respiratory monitoring systems using external surrogates. This implicates that mixed use of different respiratory monitoring systems in 4DCT imaging for treatment planning and in respiratory gated treatment delivery may result in errors in the dose distribution received by the patient. Author Disclosure: J. Liu: None. T. Lin: None. J. Fan: None. L. Chen: Fox Chase Cancer Center. R.A. Price: None. Y. Dong: None. C. Ma: Research Grant; Accuray. committee members; AAPM.
IMRT (0.7660.055, 7598.5167.9, p<0.01), cVMAT (0.7890.045, 7507.7107.8, p<0.05) and ncVMAT (0.7710.049, 7632.8184.7, p<0.01) respectively. Furthermore, MRT improved dose sparing of lens (D1%Z 633.947.1) compared with IMRT (723.168.7,p<0.01), cVMAT (686.030.4, p<0.01) and ncVMAT (721.757.9,p<0.01). MRT reduced optic nerves dose (D1%Z 4547.5678.3) compared with IMRT (5434.0372.3,p<0.01), cVMAT (4683.8569.4,p<0.05) and ncVMAT (4666.5501.2, p<0.05;) However, the dose of brain stem was increased in MRT (D1%Z4117.9159.1) but kept in the nomal threshold compared with IMRT (3114.5201.3,p<0.01), cVMAT (2735.2253.1, p<0.01) and ncVMAT (2872.0192.2,p<0.01). Additionally, MRT increased optic chiasm dose (D1%Z4831.9231.2) compared with IMRT (3828.6307.8, p<0.01), cVMAT (4628.2221.4, p<0.01) and ncVMAT (3889.6183.5, p<0.01). MRT greatly reduced MU (376.223.7) compared with IMRT (895.359.4, p<0.01), cVMAT (403.928.6,p<0.05) and ncVMAT (398.020.3,p<0.05). Conclusion: MRT is superior to IMRT or VMAT for SNC for better target coverage and protection of lens and optic nerves, reduced MU. The dose of brain stem and optic chiasm is slightly increased but kept in the nomal threshold. MRT is a good option for SNC. Author Disclosure: M. Liu: None. H. Wang: None. B. Liu: None. W. Xia: None. Y. Gao: None. W. Shi: None. L. Dong: None.
3647
Purpose/Objective(s): The definite indication of flattening filter free Rapid-ARC is still unclear yet. Our study compared the dose distribution of target volumes, dose fall, protection of normal organs at risk (OAR) and monitor unit (MU) of 3 radiotherapy techniques (Rapid-ARC FFF, IMRT FF and Rapid-ARC FF) in superficial tumors of head and neck. Materials/Methods: Nine patients were enrolled. The three RT plans mentioned above were designed for each patient with 6MV X-ray. The prescribed dose was 54Gy/30f/1.8Gy to PTV concurrent with 64.2Gy/30f/ 2.14Gy to PGTV. The target volume coverage indicators included conformity and homogeneity index (CI, HI). The dose fall indicators included V40 and V20 (the covered volume by 40Gy and 20Gy, respectively). OARs included the brainstem and spinal cord. All the optimized parameters and target values for plans were consistent. Results: Rapid-ARC FFF provided significantly improved conformity (0.7620.013) and homogeneity (1.0730.022) of PGTV than IMRT FF (CIZ 0.6770.076, p<0.01; HIZ 1.1160.048, p<0.05), and RapidARC FF (CIZ 0.7170.077, HIZ 1.0800.018, p<0.05). Rapid-ARC FFF has a better CI (0.8000.049) of PTV compared with IMRT FF (0.7540.071, p<0.05) and Rapid-ARC FF (0.7680.074, p<0.05) respectively.Furthermore, RapidArc FFF had a rapider dose fall. RapidArc and FFF remarkably reduced V40 (445.85213.60cm3) V20(972.42428.70cm3) compared with IMRT FF (V40Z 472.62219.63cm3, V20Z 1000.18445.74cm3, p<0.01) and RapidARC FF (V40Z 454.51221.50cm3, V20Z 1018.17475.67cm3, p<0.01). However, the dose of brain stem was increased in RapidArc FFF (D1ccZ2669.46927.05cGy) but kept in the nomal threshold compared with IMRT FF (2593.97872.12cGy, p<0.05) and Rapid-ARC FF (2656.97909.73cGy,p<0.05). Similarly, the dose of cord was increased in RapidArc FFF (D1ccZ3031.25438.77cGy) but kept in the nomal threshold compared with IMRT FF (3027.76426.03cGy,p<0.05) and Rapid-ARC FF (3025.33487.39cGy,p<0.05). RapidArc FFF greatly reduced MU (344.0040.62) compared with IMRT FF (613.50100.06, p<0.01) but slightly increased MU compared with RapidArc FF (325.7531.15,p<0.05).
A Novel Mixed Radiation Therapy Technique For Sinonasal Cancer: Dosimetric Study To Determine the Best Plan M. Liu, H. Wang, B. Liu, W. Xia, Y. Gao, W. Shi, and L. Dong; Department of Radiation Oncology, The First Hospital, Jilin University, Changchun, China Purpose/Objective(s): Radiotherapy (RT) is essential for malignancies of the nasal cavity and paranasal sinuses (sinonasal cancer [SNC]). However, RT plan is challenging for high prescribed dose and close proximity of critical structures. Here, we developed a novel mixed RT (MRT) plan consisting of one 3D-CRT and two-arc VMAT fields and compared the dose distribution of target volumes, protection of normal organs at risk (OAR) and monitor unit (MU) of four radiotherapy techniques (MRT, noncoplanar IMRT, coplanar and non-coplanar VMAT[cVMAT, ncVMAT]). Materials/Methods: Thirteen patients were enrolled. The four RT plans mentioned above were designed for each patient with 6MV X-ray. The prescribed dose was 59.4Gy/33f/1.8Gy to PTV concurrent with 69.96Gy/ 33f/2.12Gy to PGTV. The target volume coverage indicators included conformity and homogeneity index (CI, HI), D1% and D99%. OARs included the lens, brainstem, optic nerves and chiasm. All the optimized parameters and target values for plans were consistent. Results: MRT provided improved conformity (0.8250.041) and homogeneity (1.0660.015) of PGTV than IMRT (CIZ 0.7930.042, HIZ 1.1170.018, p<0.05), cVMAT (CIZ 0.8200.037, HIZ 1.0710.031, p<0.05), and ncVMAT (CIZ 0.8010.050, HIZ 1.0980.026, p<0.05). The dose unit was cGy. MRT also reduced D1% of PGTV significantly (7470.5113.6) compared with IMRT (7635.7189.8,p<0.01), cVMAT (7571.0109.4,p<0.05) and ncVMAT (7697.7200.1,p<0.01). MRT increased D99% of PGTV remarkably (6529.7108.4) compared with IMRT (6347.6175.2,p<0.01), cVMAT (6507.5111.9,p<0.05) and ncVMAT (6267.3156.7,p<0.01). MRT has a significantly better CI (0.8070.039) and reduced D1% (7436.1112.3) of PTV compared with
3648 Dosimetric Analysis of Radiation Therapy Plans With or Without Flattening Filter in Superficial Tumors of Head and Neck M. Liu, H. Wang, B. Liu, K. Chen, Y. Shi, C. Ge, and L. Dong; Department of Radiation Oncology, The First Hospital, Jilin University, Changchun, China