Set-up errors in helical tomotherapy for breast cancer patients

doi:10.3877/cma.j.issn.1674-0807.2015.03.005

Abstract

Abstract:

Objective

To analyze the set-up errors of breast cancer patients based on helical tomotherapy treatment with mega-voltage CT (MVCT), and measure the margins of planning target volume(PTV).

Methods

We enrolled fourteen breast cancer patients treated with helical tomotherapy in Department of Radiation Oncology, Air Force General Hospital from August 2011 to November 2014.MVCT scanning was performed before each treatment and registered with the kilo-voltage CT (kVCT) image.The set-up errors of the transverse profile rotation (Roll), left-right (X), anterior-posterior (Y) and superior-inferior (Z) positions were recorded.The PTV margin was calculated based on the formula M=2.5∑+0.7δ-3.

Results

Three hundred and fourteen MVCT images were received for all patients.The set-up error frequency within 5 mm in the X, Y and Z directions was 89.81%(282/314), 82.17%(258/314) and 97.13%(305/314) respectively,and within 2° in the Roll direction was 91.08%(286/314).The average set-up errors were (4.26±3.70) mm,(3.10±2.80) mm, (2.02±1.50) mm and (0.70±0.40)° in the X, Y, Z and Roll directions respectively.The PTV margins in X, Y, and Z directions were 4.56,3.44 and 2.79 mm.

Conclusions

The breast cancer patients' set-up errors are acceptable based on MVCT of helical tomotherapy, and it can provide a certain quality assurance with the PTV margins of 5,3 and 3 mm in X, Y and Z directions respectively.

Key words: Breast neoplasms, Radiotherapy, Tomography, spiral computed

Fuhai Zhu, Xiaolong Hu, Hefei Liu, Weizhang Wu, Yingjie Wang, Tingyi Xia. Set-up errors in helical tomotherapy for breast cancer patients[J]. Chinese Journal of Breast Disease(Electronic Edition), 2015, 09(03): 178-181.

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误差值	X方向		Y方向		Z方向
误差值	次数	百分比(%)	次数	百分比(%)	次数	百分比(%)
＜3mm	260	82.80	192	61.15	281	89.49
3～5mm	22	7.01	66	21.02	24	7.64
＞5mm	32	10.19	56	17.83	9	2.87

误差值	X方向		Y方向		Z方向
误差值	次数	百分比(%)	次数	百分比(%)	次数	百分比(%)
＜3mm	260	82.80	192	61.15	281	89.49
3～5mm	22	7.01	66	21.02	24	7.64
＞5mm	32	10.19	56	17.83	9	2.87

患者编号	X(mm)	Y(mm)	Z(mm)	Roll(°)
1	-3.96±4.80	-0.83±0.90	0.02±0.20	0.41±0.40
2	-3.29±1.90	-1.08±1.90	0.08±0.80	-0.19±0.10
3	0.56±1.50	4.62±5.00	-1.36±1.80	-0.28±0.10
4	-5.08±5.80	3.04±2.50	0.31±0.20	1.18±1.10
5	-4.86±4.40	2.10±2.80	-0.52±0.00	0.40±0.30
6	-3.49±2.60	3.26±3.70	-0.52±0.20	0.04±0.00
7	-4.75±5.20	2.00±2.30	-2.23±3.20	0.36±0.45
8	3.13±3.30	-0.18±0.65	0.22±0.25	-0.69±0.60
9	-5.96±7.10	1.22±1.00	0.05±0.30	1.46±1.10
10	2.50±3.25	1.91±1.16	-0.81±0.08	-0.10±0.00
11	-1.66±2.05	4.30±4.30	2.85±2.80	-0.17±0.00
12	-0.59±1.18	1.70±2.10	-0.76±1.30	0.18±0.25
13	3.52±2.70	2.44±2.55	2.34±2.55	-0.60±0.30
14	2.65±2.75	0.78±0.95	1.51±1.70	-0.30±0.00

患者编号	X(mm)	Y(mm)	Z(mm)	Roll(°)
1	-3.96±4.80	-0.83±0.90	0.02±0.20	0.41±0.40
2	-3.29±1.90	-1.08±1.90	0.08±0.80	-0.19±0.10
3	0.56±1.50	4.62±5.00	-1.36±1.80	-0.28±0.10
4	-5.08±5.80	3.04±2.50	0.31±0.20	1.18±1.10
5	-4.86±4.40	2.10±2.80	-0.52±0.00	0.40±0.30
6	-3.49±2.60	3.26±3.70	-0.52±0.20	0.04±0.00
7	-4.75±5.20	2.00±2.30	-2.23±3.20	0.36±0.45
8	3.13±3.30	-0.18±0.65	0.22±0.25	-0.69±0.60
9	-5.96±7.10	1.22±1.00	0.05±0.30	1.46±1.10
10	2.50±3.25	1.91±1.16	-0.81±0.08	-0.10±0.00
11	-1.66±2.05	4.30±4.30	2.85±2.80	-0.17±0.00
12	-0.59±1.18	1.70±2.10	-0.76±1.30	0.18±0.25
13	3.52±2.70	2.44±2.55	2.34±2.55	-0.60±0.30
14	2.65±2.75	0.78±0.95	1.51±1.70	-0.30±0.00

方向	系统误差	随机误差的标准差(δ)	系统误差的标准差(Σ)	间距值(M)
X	-1.52	1.98	2.47	4.56
Y	1.81	2.20	1.96	3.44
Z	0.08	0.20	0.03	2.79

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