Influence of intravenous contrast agent on dose calculations of intensity modulated radiation therapy plans for head and neck cancer

Choi, Youngmin; Kim, Jeung-Kee; Lee, Hyung-Sik; Hur, Won-Joo; Hong, Young-Seoub; Park, Sungkwang; Ahn, Kijung; Cho, Heunglae

doi:10.1016/j.radonc.2006.09.010

« Previous Next »Radiotherapy & Oncology
Volume 81, Issue 2 , Pages 158-162, November 2006

Influence of intravenous contrast agent on dose calculations of intensity modulated radiation therapy plans for head and neck cancer

Youngmin Choi
- Department of Radiation Oncology, and
- Corresponding author. Youngmin Choi, Department of Radiation Oncology, College of Medicine, Dong-A University Hospital, 3-Ga-1 Dongdaesindong, Sugu, Busan 602-175, South Korea.
Jeung-Kee Kim
- Department of Radiation Oncology, and
Hyung-Sik Lee
- Department of Radiation Oncology, and
Won-Joo Hur
- Department of Radiation Oncology, and
Young-Seoub Hong
- Department of Preventive Medicine, College of Medicine, Dong-A University Hospital, Sugu, Busan, South Korea
Sungkwang Park
- Department of Radiation Oncology, College of Medicine, Inje University, Busan, South Korea
Kijung Ahn
- Department of Radiation Oncology, College of Medicine, Inje University, Busan, South Korea
Heunglae Cho
- Department of Radiation Oncology, College of Medicine, Inje University, Busan, South Korea

Received 16 January 2006; received in revised form 19 September 2006; accepted 22 September 2006.

Abstract

Background and purpose

To evaluate the effect of an intravenous contrast agent (CA) on dose calculations and its clinical significance in intensity modulated radiation therapy (IMRT) plans for head and neck cancer.

Materials and methods

Fifteen patients with head and neck cancer and involved neck nodes were enrolled. Each patient took two sets of computerized tomography (CT) in the same position before and after intravenous CA injections. Target volumes and organs at risk (OAR) were contoured on the enhanced CT, and then an IMRT plan of nine equiangular beams with a 6MV X-ray was created. After the fusion of non-enhanced and enhanced CTs, the contours and the IMRT plan created from the enhanced CT were copied and placed to the non-enhanced CT. Doses were calculated again from the non-enhanced CT by the same IMRT plan. The radiation doses calculated from the two sets of CTs were compared with regard to planning target volumes (PTV) and the three OARs, both parotid glands and the spinal cord, by Wilcoxon’s signed rank test.

Results

The doses (maximum, mean, and the dose of 95% of PTV received (D_95%)) of PTV70 and PTV59.4 calculated from the enhanced CTs were lower than those from the non-enhanced CTs (p<0.05), but the dose differences were less than 1% compared to the doses calculated from the enhanced CTs. The doses of PTV50.4, parotid glands, and spinal cord were not significantly different between the non-enhanced and enhanced CTs.

Conclusions

The difference between the doses calculated from the CTs with and without CA enhancement was tolerably small, therefore using intravenous CA could be recommended for the planning CT of head and neck IMRT.

Keywords: Contrast agent, Dose calculation, Intensity modulated radiation therapy, Head and neck cancer