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Treatment of Liver Metastases Using an Internal Target Volume Method for Stereotactic Body Radiotherapy
Published on: May 8, 2018
Defining internal target volume (ITV) for hepatocellular carcinoma using four-dimensional CT
Mian Xi1, Meng-Zhong Liu, Xiao-Wu Deng
1Department of Radiation Oncology, Cancer Center, Sun Yat-sen University, Guangzhou, China.
Summary
Four-dimensional computed tomography (4DCT) improves hepatocellular carcinoma treatment by defining individualized internal target volumes (ITVs). This approach reduces planning target volumes, spares normal tissues, and allows for dose escalation in radiation therapy.
Area of Science:
- Radiation Oncology
- Medical Imaging
- Hepatocellular Carcinoma Treatment
Background:
- Hepatocellular carcinoma (HCC) treatment planning traditionally uses 3D imaging.
- Challenges exist in accurately defining target volumes due to respiratory motion.
- Individualized internal target volume (ITV) definition is crucial for effective HCC radiotherapy.
Purpose of the Study:
- To define individualized internal target volume (ITV) for hepatocellular carcinoma (HCC) using four-dimensional computed tomography (4DCT).
- To compare 3D and 4D treatment planning parameters for HCC.
- To evaluate the impact of 4DCT-based planning on target volume, normal tissue sparing, and dose escalation.
Main Methods:
- Contouring of gross tumor volumes (GTVs) and clinical target volumes (CTVs) across 10 respiratory phases of 4DCT scans in 10 HCC patients.
- Generation of 3D planning target volumes (PTVs) from a single CTV plus margins.
- Generation of 4D PTVs from an ITV encompassing all CTVs across respiratory phases plus setup margins.
Main Results:
- Average PTV volume was significantly smaller with 4D plans (328.4 cm³) compared to 3D plans (407.0 cm³).
- 4D plans demonstrated superior sparing of surrounding normal tissues, particularly the liver, with a reduced mean dose (20.3 Gy vs. 22.7 Gy).
- 4D plans enabled a dose escalation of 7.5% without increasing normal tissue complication probability (NTCP).
Conclusions:
- Conventional 3D planning for HCC can lead to geometric misses and unnecessary irradiation of normal tissues.
- 4DCT-based planning allows for reduced target volumes, enhanced normal tissue sparing, and potential for dose escalation in HCC radiotherapy.
- Individualized ITV definition using 4DCT offers a significant advantage over traditional 3D planning for HCC.
