Target localization of 3D versus 4D cone beam computed tomography in lipiodol-guided stereotactic radiotherapy of hepatocellular carcinomas

Abstract Background: Radiotherapy of gastric mucosa-associated lymphoid tissue (MALT) lymphoma should be delivered to the entire stomach with planning target volume (PTV) that accounts for variations in stomach volume, respiratory movement, and patient set-up error. In this study, we evaluated whether the use of four-dimensional cone-beam computed tomography (4D-CBCT) reduces the PTV. Methods: Eight patients underwent radiotherapy with 15 fractions of gastric MALT lymphoma using 4D-CBCT. PTV structures of 5–30 mm margins (5 mm intervals) from the clinical target volume (CTV) delineated based on the 4D-CT images (CTV-4D) were generated. For the target localization, we performed matching based on skin marking (skin matching), bone anatomy (bone matching), and stomach anatomy (4D soft-tissue matching) based on registration between planning CT and 4D-CBCT images from 10 phases. For each patient, we calculated the covering ratio (CR) of the stomach with variable PTV structures, based on the 4D-CBCT images, with a total of 150 phases [CR (%) = (number of covering phases / 150 phases) × 100], for three target localization methods. We compared the CR values of the different target localization methods and defined the PTV with an average CR of ≥ 95 % for all patients. Results: The average CR for all patients increased from 17.9 % to 100 %, 19.6 % to 99.8 %, and 33.8 % to 100 %, in the skin, bone, and 4D soft-tissue matchings, respectively, as the PTV structures increased from 5 to 30 mm. The CR obtained by 4D soft-tissue matching was superior to that obtained by skin (P = 0.013) and bone matching (P = 0.008) for a PTV structure of 15 mm margin. The PTV required an additional margin of 20 mm (average CR: 95.2 %), 25 mm (average CR: 99.1 %), and 15 mm (average CR: 98.0 %) to CTV-4D for the skin, bone, and 4D soft-tissue matchings, respectively. Conclusions: This study demonstrates that the use of 4D-CBCT reduces the PTV when applying 4D soft-tissue matching, compared to skin and bone matchings. Additionally, bone matching does not reduce the PTV as compared with traditional skin matching.

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Comparison of daily cone-beam computed tomography and kilovoltage planar imaging for target localization in prostate cancer patients following radical prostatectomy

Practical Radiation Oncology ◽

10.1016/j.prro.2010.12.002 ◽

2011 ◽

Vol 1 (3) ◽

pp. 156-162 ◽

Cited By ~ 7

Author(s):

Daniel R. Simpson ◽

John P. Einck ◽

Sameer K. Nath ◽

Rajni A. Sethi ◽

Jia Zhu Wang ◽

...

Keyword(s):

Prostate Cancer ◽

Computed Tomography ◽

Radical Prostatectomy ◽

Cancer Patients ◽

Cone Beam Computed Tomography ◽

Target Localization ◽

Cone Beam ◽

Planar Imaging

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A Phantom Study on Target Localization Accuracy Using Cone-Beam Computed Tomography

Clinical medicine Oncology ◽

10.4137/cmo.s808 ◽

2008 ◽

Vol 2 ◽

pp. CMO.S808 ◽

Cited By ~ 1

Author(s):

Hui Yan ◽

Liwei Zhang ◽

Fang-Fang Yin

Keyword(s):

Computed Tomography ◽

Image Registration ◽

Cone Beam Computed Tomography ◽

Vertical Axis ◽

Target Localization ◽

Cone Beam ◽

Detection Error ◽

Localization Accuracy ◽

3 Dimensional ◽

Residual Errors

The purpose of this study is to evaluate the 3-dimensional target localization accuracy of cone-beam computed tomography (CBCT) using an on-board imager (OBI). An anthropomorphic pelvis phantom was used to simulate a range of offsets in the three translational directions and rotations around each of the three axes. After a translational or rotational offset was applied, a CBCT scan of the phantom was followed by image registration to detect the offsets in six degrees. The detected offsets were compared to the offset actually applied to give the detection error of the phantom position. Afterwards, the phantom was positioned by automatically moving the couch based on the detected offsets. A second CBCT scan followed by image registration was performed to give the residual error of the phantom positioning. On the average the detection errors and their standard deviations along the lateral, longitudinal and vertical axis are 0.3 ± 0.1, 0.3 ± 0.1 and 0.4 ± 0.1 mm respectively with respect to translational shifts ranging from 0 to 10 mm. The corresponding residual errors after positioning are 0.3 ± 0.1, 0.5 ± 0.1 and 0.3 ± 0.1 mm. For simulated rotational shifts ranging from 0 to 5 degrees, the average detection error and their standard deviation around lateral, longitudinal, and vertical axes are 0.1 ± 0.0, 0.2 ± 0.0, and 0.2 ± 0.0 degrees respectively. The residual errors after positioning are 0.4 ± 0.1, 0.6 ± 0.1, and 0.3 ± 0.1 mm along the lateral, longitudinal and vertical directions. These results indicate that target localization based on CBCT is capable of achieving sub-millimeter accuracy.

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