Clinical Implementation of HyperArc

doi:10.21203/rs.3.rs-489665/v1

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Clinical Implementation of HyperArc

https://doi.org/10.21203/rs.3.rs-489665/v1

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published 11 Apr, 2022

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The aim of this study was to present our experience on clinical implementation of HyperArc including dosimetric comparison between VMAT and HyperArc plans and dosimetric verification of HyperArc. In this study, eleven previously treated cases of brain metastasis were selected from our brain stereotactic radiotherapy program. The cases were retrospectively planned using HyperArc technique and the plan quality was evaluated. In addition, dosimetric effects of HyperArc plan with different energies and using jaw tracking technique were evaluated. Furthermore, dosimetric verification of HyperArc plans was performed using ion chamber and radiochromic film. Our results of dosimetric comparison shows that HyperArc technique improved both conformity index and gradient index compared to VMAT plans. We also found that using 6MV flattening filter free (6MV-FFF) beam improves gradient index in HyperArc plans compared to using 6MV flattening filter beam. Furthermore, our results show that jaw tracking technique reduces the size of low dose volume while maintaining similar target coverage, conformity index, and gradient index. In our dosimetric verification study, results of ion chamber and film measurement indicate no significant difference between VMAT and HyperArc plans. In conclusion, HyperArc simplifies planning of stereotactic treatment for brain and improves the dosimetry in treatment plans. Additionally, HyperArc provides safe and efficient treatment delivery to stereotactic treatment to brain.

Cancer Biology

HyperArc

Stereotactic radiosurgery

Stereotactic radiotherapy

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Table 1. Characteristics of eleven cases used in retrospective planning study during HyperArc commissioning at WRCC.

Case #	Prescription Dose	No. of Target	PTV Volume (cm³)
1	27Gy/3#	1	4.6
2	24Gy/3#	1	1.6
3	30Gy/5#	1	6.9
4	30Gy/5#	1	42.6
5	27Gy/3#	1	21.1
6	25Gy/5#	1	23.9
7	27Gy/3#	1	1.4
8	30Gy/5#	2	5.6
8	30Gy/5#	2	6.8
9	24Gy/3#	3	1.3
			3.2
			8.3
10	24Gy/3#	2	9.3
10	24Gy/3#	2	9.7
11	27Gy/3#	2	4.2
11	27Gy/3#	2	1.0

Table 2. Configuration of fields used in each plan of off-centre Winston Lutz test

Field	Gantry Angle (Deg)	Collimator Angle (Deg)	Couch Angle (Deg)
1	0	0	0
2	0	90	0
3	0	270	0
4	0	0	90
5	0	0	270
6	270	0	0
7	90	0	0
8	180	0	0

Table 3. Comparison of target quality metric of HyperArc plans obtained from TPS and manual calculations.

Test Plan	RTOG CI		Paddick CI		GI		ICRU83 HI
Test Plan	TPS	Manual	TPS	Manual	TPS	Manual	TPS	Manual
1	1.13	1.10	0.83	0.77	3.06	3.07	0.18	0.18
2	1.17	1.12	0.80	0.71	3.42	3.45	0.22	0.22
3	1.21	1.13	0.73	0.74	3.25	3.27	0.12	0.12
4	1.07	1.05	0.91	0.89	2.52	2.53	0.22	0.22
5	1.08	1.05	0.89	0.90	2.58	2.59	0.14	0.14
6	1.11	1.05	0.84	0.84	2.80	2.81	0.13	0.13
7	1.27	1.18	0.68	0.69	4.61	4.64	0.22	0.22

Table 4. Plan comparison between VMAT and HyperArc (HA) techniques in brain SRT.

Case #	PTV				Target Quality Metrics				Healthy Brain
	V_100% (%)		D_max (Gy)		Paddick CI		GI		V_18Gy (cm³)
	VMAT	HA	VMAT	HA	VMAT	HA	VMAT	HA	VMAT	HA
1	99.6	99.6	35.1	33.8	0.74	0.83	3.54	3.06	11.0	8.1
2	99.5	99.5	30.3	30.9	0.63	0.80	5.00	3.42	4.6	2.9
3	99.5	99.5	37.8	34.8	0.66	0.73	3.59	3.25	16.6	10.1
4	99.5	99.5	39.5	39.2	0.93	0.91	2.42	2.52	41.2	40.7
5	99.5	99.5	33.8	32.4	0.81	0.89	3.95	2.58	25.9	18.8
6	98.8	98.8	30.5	29.8	0.74	0.84	2.95	2.77	31.3	26.4
7	99.9	99.9	34.9	35.1	0.67	0.68	5.30	4.61	4.8	3.2
8	99.5	99.9	36.7	35.4	0.70	0.83	3.96	3.48	29.2	19.0
8	99.6	99.5	38.7	35.6	0.68	0.78	3.58	3.39	29.2	19.0
9	100	99.8	30.6	30.4	0.64	0.73	4.10	3.78	24.3	15.8
	99.9	99.6	29.5	30.4	0.70	0.78	3.40	3.45
	99.6	99.7	31.1	30.6	0.77	0.85	3.10	2.86
10	99.2	99.9	29.6	30.4	0.81	0.86	3.26	2.75	29.4	21.8
10	99.1	99.1	32.2	30.4	0.82	0.85	2.83	2.81	29.4	21.8
11	99.5	99.5	30.8	34.2	0.81	0.79	3.81	3.41	15.0	10.1
11	99.5	99.7	32.6	34.2	0.63	0.71	5.40	4.02	15.0	10.1

Table 5. Plan comparison between HyperArc plans using 6MV flattened beam (6MV) and 6MV flattening free filter beam (6MV-FFF).

Case #	PTV				Target Quality Metrics					Healthy Brain			Normalized MU/Gy
	V_100% (%)		D_max (Gy)		Paddick CI		GI			V_18Gy (cm³)			Normalized MU/Gy
	6MV	6MV-FFF	6MV	6MV-FFF	6MV	6MV-FFF	6MV	6MV-FFF	6MV		6MV-FFF	6MV		6MV-FFF
2	99.3	99.3	30.9	30.4	0.80	0.81	3.42	3.34	2.9		2.9	286		289
3	99.5	99.5	34.8	34.9	0.73	0.73	3.25	3.22	10.1		9.9	266		252
4	99.9	99.5	39.2	39.0	0.91	0.92	2.52	2.48	40.7		39.6	252		263
7	99.9	99.9	35.1	35.0	0.68	0.68	4.61	4.39	3.2		3.1	238		307
8	99.9	100.0	35.4	36.2	0.83	0.81	3.48	3.31	19.0		18.8	192		204
8	99.5	99.5	35.6	35.8	0.78	0.78	3.39	3.28	19.0		18.8	192		204
9	99.8	99.7	30.4	30.2	0.78	0.81	3.78	3.65	15.8		15.5	257		284
	99.6	99.6	30.4	30.3	0.73	0.73	3.45	3.32
	99.7	99.8	30.6	30.4	0.85	0.85	2.86	2.78
11	99.5	99.6	34.2	34.5	0.79	0.78	3.41	3.36	10.1		10.2	281		320
11	99.7	99.5	34.2	34.5	0.71	0.71	4.02	3.97	10.1		10.2	281		320

Table 6. Plan comparison between HyperArc plans using static jaw technique (SJT) and jaw tracking technique (JTT).

Case #	Energy	Target Quality Metrics				Low Dose Volume (cm³)
		Paddick CI		GI		V_10%			V_20%			V_30%
		SJT	JTT	SJT	JTT	SJT	JTT	% Diff	SJT	JTT	% Diff	SJT	JTT	% Diff
1	6MV	0.83	0.83	3.06	3.12	242	222	-8	72	64	-11	36	34	-5
2	6MV	0.80	0.81	3.42	3.41	83	67	-18	27	22	-19	14	12	-11
	6MV-FFF	0.81	0.80	3.34	3.19	79	67	-15	25	21	-17	13	12	-10
3	6MV	0.73	0.74	3.25	3.18	226	210	-7	91	84	-8	52	49	-6
6	6MV	0.84	0.84	2.77	2.60	540	463	-14	239	202	-16	141	123	-13
8	6MV	0.83	0.83	3.48	3.38	576	528	-8	185	173	-6	100	96	-4
		0.78	0.78	3.39	3.37
	6MV-FFF	0.81	0.83	3.31	3.46	545	523	-4	175	169	-4	97	96	-1
		0.78	0.78	3.28	3.34
9	6MV	0.73	0.73	3.78	3.74	874	736	-16	266	222	-16	109	100	-8
		0.78	0.78	3.45	3.37
		0.85	0.85	2.86	2.84
	6MV-FFF	0.73	0.73	3.65	3.66	831	709	-15	244	213	-13	102	95	-6
		0.78	0.78	3.32	3.25
		0.85	0.85	2.78	2.71
10	6MV	0.86	0.87	2.75	2.76	1001	848	-15	275	233	-15	129	119	-8
		0.85	0.86	2.81	2.79
11	6MV	0.79	0.78	3.41	3.34	481	360	-25	92	83	-11	45	43	-4
		0.71	0.71	4.02	4.19
	6MV-FFF	0.78	0.79	3.36	3.34	442	333	-25	88	79	-9	43	42	-3
		0.71	0.71	3.97	4.13

Table 7. Results of dosimetric verification of VMAT and HyperArc plans listed in Table 4.

Case #	VMAT					HyperArc
	Point Dose	Film Gamma Passing Rate (%)				Point Dose	Film Gamma Passing Rate (%)
	Point Dose	Absolute		Relative		Point Dose	Absolute		Relative
	% Diff.	3%/1mm	5%/1mm	3%/1mm	5%/1mm	% Diff.	3%/1mm	5%/1mm	3%/1mm	5%/1mm
1	-0.4	81.4	97.7	98.9	99.2	2.9	77.0	88.2	98.8	99.7
2	3.4	94.4	98.0	94.8	97.8	4.8	93.2	96.6	100.0	100.0
3	0.1	92.6	94.4	97.8	100.0	1.8	78.7	93.5	99.5	100.0
4	2.6	91.7	99.3	97.9	99.6	1.4	89.6	97.6	98.7	99.7
5	1.5	99.2	99.7	99.4	99.8	1.4	72.5	79.7	96.3	99.5
6	1.2	94.5	98.8	90.1	95.4	1.8	86.9	97.9	95.5	99.6
7	0.7	72.8	93.8	83.9	100.0	1.5	92.1	95.7	97.8	99.6
8	2.6	97.9	99.8	98.1	99.8	1.2	91.2	98.3	95.5	98.7
8	1.2	94.1	95.9	98.3	99.1	0.1	99.3	100.0	99.2	100.0
9	1.1	83.2	96.1	82.9	96.4	2.3	85.1	94.9	99.7	100.0
	0.4	94.3	99.2	96.9	99.8	2.2	85.1	94.9	99.7	100.0
	-0.5	91.4	97.9	99.9	100.0	1.4	92.7	98.3	99.3	100.0
10	1.1	84.9	92.3	96.0	98.6	0.8	90.9	93.7	95.7	99.4
10	1.1	91.8	97.0	99.2	99.8	0.6	90.9	93.7	95.7	99.4
11	1.6	99.0	99.9	100.0	100.0	0.7	92.1	94.7	96.2	98.8
11	3.5	97.3	98.4	100.0	100.0	0.9	99.8	100.0	100.0	100.0
Mean	1.3	91.3	97.4	95.9	99.1	1.6	88.6	94.9	98.0	99.6
SD	1.2	7.2	2.3	5.5	1.4	1.1	8.0	5.4	1.8	0.4

Table 8. Results of dosimetric verification of HyperArc plans using 6MV and 6MV-FFF beam.

Case #	6MV					6MV-FFF
	Point Dose	Film Gamma Passing Rate (%)				Point Dose	Film Gamma Passing Rate (%)
	Point Dose	Absolute		Relative		Point Dose	Absolute		Relative
	% Diff.	3%/1mm	5%/1mm	3%/1mm	5%/1mm	% Diff.	3%/1mm	5%/1mm	3%/1mm	5%/1mm
2	4.8	93.2	96.6	100.0	100.0	5.0	98.2	99.0	99.7	100.0
3	1.8	78.7	93.5	99.5	100.0	0.3	73.7	89.6	98.0	100.0
4	1.4	89.6	97.6	98.7	99.7	1.3	85.8	97.2	93.6	99.0
7	1.5	92.1	95.7	97.8	99.6	-2.0	93.7	96.9	98.8	99.5
8	1.2	91.2	98.3	95.5	98.7	0.6	95.7	99.3	95.7	98.1
8	0.1	99.3	100.0	99.2	100.0	-0.2	93.9	99.7	99.9	100.0
9	2.3	85.1	94.9	99.7	100.0	2.3	83.9	94.9	99.8	100.0
	2.2	85.1	94.9	99.7	100.0	1.6	83.9	94.9	99.8	100.0
	1.4	92.7	98.3	99.3	100.0	1.1	95.8	99.5	98.7	99.9
11	0.7	92.1	94.7	96.2	98.8	0.5	100.0	100.0	99.9	100.0
11	0.9	99.8	100.0	100.0	100.0	0.5	97.9	98.8	100.0	100.0
Mean	1.7	91.4	96.9	98.6	99.7	0.9	91.9	97.5	98.4	99.6
SD	1.2	6.2	2.3	1.6	0.5	1.7	8.2	3.2	2.2	0.6

Table 9. Results of off-centre Winston Lutz test

Off-centre Distance (cm)	Maximum total delta of Winston Lutz test (mm)
	Phantom Shift Direction
	Lateral	Longitudinal	Vertical
0	0.67 ± 0.19	0.67 ± 0.19	0.67 ± 0.19
3	0.62 ± 0.17	0.75 ± 0.10	0.67 ± 0.16
5	0.85 ± 0.09	0.62 ± 0.14	0.61 ± 0.07
7	0.89 ± 0.05	0.85 ± 0.09	0.56 ± 0.10
9	1.00 ± 0.07	0.93 ± 0.36	0.55 ± 0.06

Download PDF

Journal Publication

published 11 Apr, 2022

Read the published version in Physical and Engineering Sciences in Medicine →

Reviews received at journal
14 Jul, 2021
Reviewers invited by journal
01 May, 2021
First submitted to journal
31 Mar, 2021

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Clinical Implementation of HyperArc

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