Journal List > Prog Med Phys > v.26(3) > 1098472

TOOLS
Lee, Kim, Kim, Park, Min, Shin, Choi, Park, and Huh: Dosimetric Evaluation of Amplitude-based Respiratory Gating for Delivery of Volumetric Modulated Arc Therapy
Original Article

Progress in Medical Physics 2015;26(3):127-136.

Published online: 20 September 2015

DOI: https://doi.org/10.14316/pmp.2015.26.3.127

Dosimetric Evaluation of Amplitude-based Respiratory Gating for Delivery of Volumetric Modulated Arc Therapy

Chang Yeol Lee∗, Woo Chul Kim∗, Hun Jeong Kim∗, Jeong Hoon Park∗, Chul Kee Min†, Dong Oh Shin‡, Sang Hyoun Choi§, Seungwoo Park§, Hyun Do Huh∗

∗Department of Radiation Oncology, College of Medicine, Inha University, Incheon

†Department of Radiation Oncology, College of Medicine, Soonchunhyang University, Cheonan

‡Department of Radiation Oncology, College of Medicine, KyungHee University, Seoul

§Research Institute of Radiological and Medical Sciences, Korea Institute of Radiological and Medical Sciences, Seoul, Korea

Correspondence:HyunDoHuh(hyundohuh@gmail.com) Tel:82-32-890-3073, Fax:82-32-890-3082

Received 13 August 2015       Revised 31 August 2015       Accepted 8 September 2015

Copyright © 2015 Korean Society of Medical Physics

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The purpose of this study is to perform a dosimetric evaluation of amplitude-based respiratory gating for the delivery of volumetric modulated arc therapy (VMAT). We selected two types of breathing patterns, subjectively among patients with respiratory-gated treatment log files. For patients that showed consistent breathing patterns (CBP) relative to the 4D CT respiration patterns, the variability of the breath-holding position during treatment was observed within the thresholds. However, patients with inconsistent breathing patterns (IBP) show differences relative to those with CBP. The relative isodose distribution was evaluated using an EBT3 film by comparing gated delivery to static delivery, and an absolute dose measurement was performed with a 0.6 cm3 Farmer-type ion chamber. The passing rate percentages under the 3%/3 mm gamma analysis for Patients 1, 2 and 3 were respectively 93.18%, 91.16%, and 95.46% for CBP, and 66.77%, 48.79%, and 40.36% for IBP. Under the more stringent criteria of 2%/2 mm, passing rates for Patients 1, 2 and 3 were respectively 73.05%, 67.14%, and 86.85% for CBP, and 46.53%, 32.73%, and 36.51% for IBP. The ion chamber measurements were within 3.5%, on average, of those calculated by the TPS and within 2.0%, on average, when compared to the static-point dose measurements for all cases of CBP. Inconsistent breathing patterns between 4D CT simulation and treatment may cause considerable dosimetric differences. Therefore, patient training is important to maintain consistent breathing amplitude during CT scan acquisition and treatment delivery.

Keywords: Amplitude-based respiratory gating, Respiratory motion, Volumetric Modulated Arc Therapy (VMAT)

References

1. M Teoh, C H Clark, K Wood, et al. Volumetricmodulated arctherapy: areviewofcurrentliteratureandclinicalusein practice. Br J Radiol. 84:967–996. 2011.
2. Li R, Mok E, Han B, et al. Evaluationofthegeometricaccu-racyofsurrogate-basedgatedVMATusingintrafractionkilovoltagex-rayimages. Med Phys. 39:2686–2693. 2012.
3. Choi K, Xing L, Koong A, et al. Firststudyofon-treatment volumetricimagingduringrespiratorygatedVMAT.Medical physics.UnitedStates: AmericanAssociationofPhysicistsin Medicine.40 (. 2013.
4. Jiwon Sung, Myonggeun Yoon, Weon Kuu Chung, et al. EvaluationoftheAccuracyforRespiratory-gatedRapidArc. PROGRESSinMEDICALPHYSICS.24, No.2 (. 2013.
5. G. Nicolini, E. Vanetti, A. Clivio, et al: Preclinicalevaluationofrespiratory-gateddeliveryofvolumetricmodulatedarc therapywithRapidArc.Phys.Med.Biol. 55:347–357. 2010.
6. J. Qian, L. Xing, W. Liu, et al: Doseverificationforrespiratorygatedvolumetricmodulatedarctherapy.Phys.Med.Biol. 56:4827–838. 2011.
7. Craig Riley, Yong Yang, Tianfang Li, et al. Dosimetric evaluationoftheinterplayeffectinrespiratory-gatedRapidArc radiationtherapy. Med. Phys. 41:011715. 2014.
8. Otto K. Volumetricmodulatedarctherapy: IMRTinasingle gantryarc. Med. Phys. 35(1):310–17. 2008.
9. D. A. Low, W. B. Harms, S. Mutic, et al: Atechniquefor thequantitativeevaluationofdosedistributions.Med.Phys. 25:656–661. 1998.
10. N. Agazaryan, T. D. Solberg, J. J. DeMarco: Patient specificqualityassuranceforthedeliveryofintensitymodulated radiotherapy.J.Appl.Clin.Med.Phys. 4:40–50. 2003.
11. Valeria Casanova Borca, Massimo Pasquino, Giuliana Russo, et al. DosimetriccharacterizationanduseofGAFCH-ROMICEBT3filmforIMRTdoseverification.J.ofAppl.Clin. Med.Phys.14: No.2 (. 2013.
12. Kan MWK, Cheung JYC, Leung LHT, et al. Theaccuracy ofdosecalculationsbyanisotropicanalyticalalgorithmsforster-eotacticradiotherapyinnasopharyngealcarcinoma.Phys.Med. Biol. 56:397. 2011.

Fig. 1.
Experimental setup of the programmable respiratory motion phantom. The insert containing the film or ion chamber moves in the inferior-superior direction, and the top platform moves in the anterior-posterior direction for the RPM block.
pmp-26-127f1.tif
Fig. 2.
The respiratory curves for Patient 1 corresponding to 1st (a), 2nd (b), and 3rd (c) fraction of the treatment. The beam “ON” is triggered at the gating window.
pmp-26-127f2.tif
Fig. 3.
The breath-holding position from marker signals are shown specifically for Patients 1 (a), 2 (b), and 3 (c). The error bars represent the amplitude standard deviations determined over the duration of the treatment. Subjectively selected patients' breathing patterns (d) are shown.
pmp-26-127f3.tif
Fig. 4.
Isodose distributions and gamma statistics comparison of gated VMAT (thin solid) vs static (thick solid) dose delivery based on the patient's respiratory trace data sets. The isodose levels shown are 90%, 70%, 50%, and 30%, and the gamma pass-rate maps show a 3% dose difference, with a 3 mm distance-to-agreement criteria.
pmp-26-127f4.tif
Fig. 5.
Vertical dose profiles for the gated VMAT (solid) vs static (dash dot dot) dose delivery based on the patients' respiratory trace data sets. The results for Patient 1 (a), 2 (b), and 3 (c) are shown.
pmp-26-127f5.tif
Table 1.
Characteristics of the study patients derived from 4D CT.
      Tumor infor mation∗    
Patient Gender/Age Pathology Location GTV (cm3) Max liver motion amplitude (mm) Breathing period (s)
1 M†/59 HCC‡ S6§ 5.85 7.2 3.4
2 M/60 HCC PVTT∥ 68.41 14.1 5.1
3 M/39 HCC S5 – S8 2,764.86 9.2 5

∗ Patients are listed in ascending order of target volume. Prescribed percentage is defined to cover 95% PTV. Hepatocellular Carcinoma,

§ S6: Segment 6,

∥ PVTT: Portal Vein Tumor Thrombosis.

† M: Male,

‡ HCC:

Table 2.
Summary of the gated VMAT treatment plans investigated in this study.
Patient PTV (cm3) Energy (MV) Field Total monitor unit Prescribed dose (Gy) Fractions
1 15.28 6 7 partial-arcs 7,081 57 3
2 124.61 6 2 full-arcs, 1 partial- –arc 4,043 40 4
3 3,656.38 6 2 full-arcs 387 45 25
Table 3.
Characteristics of respiration determined over the treatment duration for individual patients.
  Patient Total delivery time Total Breath-holding time Number of breath-holding Mean breath-holding tpb‡ (s) Breath-holding amplitude position (mm)
Mean Std
1 (CBP∗) (IBP†) 30 min 05 s 30 min 02 s 12 min 22 s 11 min 57 s 79 83 9.4 8.3 −3.82 −1.67 0.30 0.85
2 (CBP) 24 min 44 s 8 min 48 s 56 9.4 −3.75 0.43
  (IBP) 21 min 28 s 8 min 23 s 47 10.7 −1.91 0.68
3 (CBP) 10 min 48 s 3 min 13 s 39 4.9 −4.21 0.23
  (IBP) 9 min 14 s 3 min 10 s 26 7.3 1.50 0.17

∗ CBP: Correct Breathing Pattern,

† IBP: Incorrect Breathing Pattern,

‡ tpb: time per breath-holding.

Table 4.
Percentage difference in dose from the ion chamber measurements.
Patient Compared to static (%) Compared to TPS (%) Difference between static delivery and TPS (%)
1 (CBP∗) 2.12±0.21 3.65±0.21 1.6
(IBP†) 6.51±0.73 7.94±0.71  
2 (CBP) 2.48±0.12 3.98±0.12 2.3
(IBP) 8.23±0.41 9.86±0.40  
3 (CBP) 1.52±0.96 2.88±0.94 1.4
(IBP) 55.54±0.66 56.23±0.65  

∗ CBP: Consistent Breathing Pattern,

† IBP: Inconsistent Breathing Pattern.

TOOLS
Similar articles