Dosimetric Evaluation of Plans Converted with the DVH-Based Plan Converter

Minsoo Chun; Chang Heon Choi; Jung-in Kim; Jeongmin Yoon; Sung Young Lee; Ohyun Kwon; Jaeman Son; Hyun Joon An; Seong-Hee Kang; Jong Min Park

doi:10.14316/pmp.2018.29.4.157

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Chun, Choi, Kim, Yoon, Lee, Kwon, Son, An, Kang, and Park: Dosimetric Evaluation of Plans Converted with the DVH-Based Plan Converter

Original Article

Progress in Medical Physics 2018;29(4):157-163.

Published online: 19 January 2018

DOI: https://doi.org/10.14316/pmp.2018.29.4.157

Dosimetric Evaluation of Plans Converted with the DVH-Based Plan Converter

Minsoo Chun^∗,^†,^‡, Chang Heon Choi^∗,^†,^‡, Jung-in Kim^∗,^†,^‡, Jeongmin Yoon^∗,^†,^‡, Sung Young Lee^∗,^†, Ohyun Kwon^∗,^†, Jaeman Son^∗,^†, Hyun Joon An^∗,^†, Seong-Hee Kang^ΙΙ, Jong Min Park^∗,^†,^‡,^§,

^∗Department of Radiation Oncology, Seoul National University Hospital

^†Biomedical Research Institute, Seoul National University Hospital

^‡Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul

^§Center for Convergence Research on Robotics, Advanced Institutes of Convergence Technology, Suwon

^ΙΙDepartment of Radiation Oncology, Seoul National University Bundang Hospital, Seongnam, Korea

Corresponding author Jong Min Park (leodavinci@naver.com) Tel: 82-2-2072-2527 Fax: 82-2-2072-2527

Received 28 November 2018 Revised 14 December 2018 Accepted 14 December 2018

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

Plans converted using dose-volume-histogram-based plan conversion (DPC) were evaluated by comparing them to the original plans. Changes in the dose volumetric (DV) parameters of five volumetric modulated arc therapy (VMAT) plans for head and neck (HN) cancer and five VMAT plans for prostate cancer were analyzed. For the HN plans, the homogeneity indices (HIs) of the three planning target volumes (PTV) increased by 0.03, 0.02, and 0.03, respectively, after DPC. The maximum doses to the PTVs increased by 1.20, 1.87, and 0.92 Gy, respectively, after DPC. The maximum doses to the optic chiasm, optic nerves, spinal cord, brain stem, lenses, and parotid glands increased after DPC by approximately 4.39, 3.62, 7.55, 7.96, 1.77, and 6.40 Gy, respectively. For the prostate plans after DPC, the HIs for the primary and boost PTVs increased by 0.05 and 0.03, respectively, and the maximum doses to each PTV increased by 1.84 and 0.19 Gy, respectively. After DPC, the mean doses to the rectum and femoral heads increased by approximately 6.19 and 2.79 Gy, respectively, and those to the bladder decreased by 0.20 Gy when summing the primary and boost plans. Because clinically unacceptable changes were sometimes observed after DPC, plans converted by DPC should be carefully reviewed before actual patient treatment.

Keywords: DVH-based plan converter, Volumetric modulated arc therapy, Step-and-shoot IMRT, Dose-volumetric parameters, Plan quality

REFERENCES

1.Krishna GS., Srinivas V., Ayyangar K., Reddy PY. Comparative study of old and new versions of treatment planning system using dose volume histogram indices of clinical plans. J Med Phys. 2016. 41(3):192.

2.Hirata T., Kishi N., Imai Y, et al. Dose Volume Parameters as Predictors for Radiation-Induced Hypothyroidism After IMRT or VMAT for Head and Neck Squamous Cell Carcinoma: Comparison of the Availability Between Mean Thyroid Dose and Median Thyroid Dose. Int J Radiat Oncol Biol Phys. 2016. 96(2):E365.

3.Kim MY., Yu T., Wu H-G. Dose-volumetric parameters for predicting hypothyroidism after radiotherapy for head and neck cancer. Jpn J Clin Oncol. 2014. 44(4):331–37.

4.Park JM., Park S-Y., Choi CH., Chun M., Kim JH., Kim J-I. Treatment plan comparison between Tri-Co-60 magnetic-resonance image-guided radiation therapy and volumetric modulated arc therapy for prostate cancer. Oncotarget. 2017. 8(53):91174.

5.Treutwein M., Hipp M., Koelbl O., Dobler B. Searching standard parameters for volumetric modulated arc therapy (VMAT) of prostate cancer. Radiat Oncol. 2012. 7(1):108.

6.Zulkafal H., Khan M., Ahmad M., Akram M., Buzdar S., Iqbal K. Volumetric modulated arc therapy treatment planning assessment for low-risk prostate cancer in radiotherapy. Clin Cancer Investig J. 2017. 6(4):179–83.

7.Emami B., Lyman J., Brown A, et al. Tolerance of normal tissue to therapeutic irradiation. Int J Radiat Oncol Biol Phys. 1991. 21(1):109–22.

8.Lesperance RN., Kjorstadt RJ., Halligan JB., Steele SR. Colorectal complications of external beam radiation versus brachytherapy for prostate cancer. Am J Surg. 2008. 195(5):616–20.

9.Lawton CA., Michalski J., El-Naqa I, et al. RTOG GU Radiation oncology specialists reach consensus on pelvic lymph node volumes for high-risk prostate cancer. Int J Radiat Oncol Biol Phys. 2009. 74(2):383–87.

Fig. 1

A representative patient's dose distributions for the head and neck case are presented before (upper row) and after (lower row) dose volume histogram based plan conversion. Doses are shown in color wash from 40% of the prescription dose to the maximum dose. Axial (a and d), coronal (b and e), and sagittal (c and f) planes are shown.

Fig. 2

A representative patient's dose volume histograms (DVHs) for the head and neck case are shown. DVHs from the original plan are plotted with solid lines, while those from the converted plan using the dose volume histogram based plan conversion are plotted with dashed lines.

Fig. 3

A representative patient's dose distributions for the prostate case is presented before (upper row) and after (lower row) dose volume histogram based plan conversion. Doses are shown in color wash from 30% of the prescription dose to the maximum dose. Axial (a and d), coronal (b and e), and sagittal (c and f) planes are shown.

Fig. 4

A representative patient's dose volume histograms (DVHs) for the prostate case are shown. DVHs from the original plan are plotted with solid lines, while those from the converted plan using the dose volume histogram based plan conversion are plotted with dashed lines.

Table 1.

Treatment plan parameters before and after DPC.

Treatment sites		Original plan	Converted plan
Head and neck	N^a	5
	Machine	TrueBeam STx	Trilogy
	Energy	6 MV	6 MV
	Treatment Technique	VMAT^b	SS-IMRT^c
	d Input N_Fd	-	8
	Actual N_F	2	14.8±2.2 (13~18)
	Total MU^e	581.9±181.0 (467.1~889.7)	730.4±60.9 (659.1~822.3)
	MU/Gy	258.6±80.5 (207.6~395.4)	324.6±27.1 (293.0~365.5)
	Beam-on time (minutes)	1.98±0.01 (1.98~2.00)	1.21±0.14 (1.1~1.5)
Prostate	N	10 (Primary: 5, Boost: 5)
	Machine	Trilogy	TrueBeam STx
	Energy	15 MV	15 MV
	Treatment Technique	VMAT	SS-IMRT
	b Input N_F	-	8
	Actual N_F	2	8
	Total MU	490.8±158.8 (365.5~886.2)	374.3±49.4 (326.6~470.5)
	MU/Gy	272.6±88.2 (203.0~192.3)	208.0±27.4 (181.4~261.4)
	Beam-on time (minutes)	2.49±0.03 (2.48~2.56)	0.63±0.08 (0.55~0.79)

^a N, number of patients;

^b VMAT, volumetric modulated arc therapy;

^c SS-IMRT, step-and-shoot intensity modulated radiation therapy;

^d N_F, number of fields;

^e MU, monitor unit. Numerical values are presented by mean ± standard deviation, as well as minimum and maximum values are within parenthesis.

Table 2.

The DV parameters before and after DPC for the HN VMAT plans.

	Original plan	Converted plan
PTV_67.5Gy ^a
^b (Gy) D_5%	70.8±0.6	72.1±1.0
D_95% (Gy)	66.9±0.1	66.4±0.3
^c (Gy) D_max	73.3±1.3	74.5±1.6
^d (Gy) D_min	52.0±11.8	55.2±61.7
^e (Gy) D_mean	69.0±0.3	69.7±0.5
CI^f	1.04±0.08	1.19±0.14
HI^g	0.05±0.01	0.08±0.02
PTV_54Gy
D_5% (Gy)	65.1±1.3	65.6±1.2
D_95% (Gy)	53.6±0.2	53.5±1.0
D_max (Gy)	70.8±0.8	72.7±1.2
D_min (Gy)	31.6±5.2	35.9±3.7
D_mean (Gy)	57.4±0.6	58.1±0.9
HI	0.25±0.02	0.27±0.03
PTV_48Gy
D_5% (Gy)	51.8±1.3	52.5±1.2
D_95% (Gy)	47.7±0.5	47.6±0.5
D_max (Gy)	57.4±2.9	58.4±3.6
D_min (Gy)	39.1±3.7	41.5±2.9
D_mean (Gy)	49.7±0.6	50.0±0.7
HI	0.11±0.03	0.14±0.04
Organs at risk
D_max to optic chiasm (Gy)	16.5±18.4	20.9±19.5
D_max to left optic nerve (Gy)	14.9±13.2	19.3±16.1
D_max to right optic nerve (Gy)	14.6±13.0	17.4±13.3
D_max to spinal cord (Gy)	42.5±2.1	50.0±6.0
D_max to brain stem (Gy)	44.7±12.8	52.7±12.7
D_max to left lens (Gy)	3.8±1.7	5.5±3.9
D_max to right lens (Gy)	3.5±1.6	5.3±3.1
D_mean to left parotid gland (Gy)	20.2±1.8	26.4±2.1
D_mean to right parotid gland (Gy)	21.0±7.8	27.6±10.7

^a PTV_nGy, planning target volume prescribed by n Gy;

^b D_n%, dose received by at least n% volume of a structure;

^c D_max, maximum dose;

^d D_min, minimum dose;

^e D_mean, Mean dose;

^f CI, Conformity index;

^g HI, Homogeneity index.

Table 3.

The DV parameters before and after DPC for the prostate VMAT plans. Note that the DV parameters for the OARs were evaluated in the sum plan.

	Original plan	Converted plan
Primary PTV^a
^b (Gy) D_5%	52.2±0.2	54.2±1.0
D_95% (Gy)	49.9±0.1	49.5±0.1
^c (Gy) D_max	53.9±0.6	55.8±1.3
^d (Gy) D_min	40.0±10.2	42.7±1.3
^e (Gy) D_mean	51.2±0.1	52.6±0.5
CI^f	0.92±0.01	1.01±0.04
HI^g	0.04±0.01	0.09±0.02
Boost PTV
D_5% (Gy)	31.7±0.1	32.3±0.5
D_95% (Gy)	30.3±0.0	30.1±0.1
D_max (Gy)	32.5±0.2	32.7±0.5
D_min (Gy)	27.8±0.4	27.2±0.6
D_mean (Gy)	31.1±0.1	31.5±0.3
CI	0.91±0.00	0.94±0.03
HI	0.04±0.00	0.07±0.02
Organs at risk Rectum
D_60% (Gy)	32.1±2.3	42.0±4.7
D_20% (Gy)	63.4±2.0	66.4±1.8
D_mean (Gy)	41.7±2.2	47.8±3.5
^h (cc) V_70Gy	11.0±6.3	12.1±7.3
Bladder
D_50% (Gy)	20.0±11.6	20.2±11.3
D_20% (Gy)	49.2±9.6	49.4±10.4
D_mean (Gy)	28.8±9.4	28.6±9.1
V_70Gy (cc)	17.4±3.7	18.2±4.1
Femur head
D_max (Gy)	31.3±4.4	39.3±4.6
D_mean (Gy)	14.0±4.4	16.8±5.3
D_50% (Gy)	13.4±5.5	16.8±7.1
D_10% (Gy)	21.9±3.2	27.6±3.7

^a PTV, planning target volume;

^b D_n%, dose received by at least n% volume of a structure;

^c D_max, maximum dose;

^d D_min, Minimum dose;

^e D_mean, mean dose;

^f CI, conformity index;

^g HI, homogeneity index;

^h V_nGy, the percent volume receiving n Gy.

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