Abstract
Objective: To evaluate the image registration accuracy and efficiency of CT and MRI fusion using three algorithms in nasopharyngeal carcinoma (NPC). Methods and materials: Twelve sets of CT and MRI scans of 12 NPC patients were fused using three image registration algorithms, respectively: Mark‐and‐link, Interactive, and Normalized Mutual Information (NMI). Registration accuracy was evaluated by performing statistical analysis of the coordinate differences between CT and MR anatomical landmarks along the x‐, y‐ and z‐axes. The time required to complete the registration process using three algorithms was also recorded. One‐way ANOVA was used to analyze the difference of the three registration methods. Results: The mean time required for CT/MRI registration using the three different registration algorithms, mark‐and‐link, interactive, and NMI, was 6.25 min, 5.25 min, and 5.15 min, respectively. The mark‐and‐link method was more time consuming (F=8.74,p=0.001); however no statistical difference was found between the time required using interactive and NMI methods (p=0.77). Mean registration errors of the three methods along the x‐axis were 0.66 mm, 0.70 mm, and 0.68 mm, respectively (F=0.09,p=0.91). Along the y‐axis, the mean registration errors were 1.03 mm, 1.04 mm, and 1.03 mm, respectively (F=0.02,p=0.98). Along the z‐axis, they were 0.58 mm, 0.64 mm, and 0.56 mm, respectively (F=0.21,p=0.81).Conclusions: All three registration algorithms, mark‐and‐link, interactive, and NMI, can provide accurate CT/MRI registration. However the mark‐and‐link method was most time consuming.PACS number: 87.57.nj
Highlights
Correct determination of tumor localization and extension is of major importance in radiation oncology
MR imaging suffers from geometric distortion at the edges of the field of view and are susceptible of artifacts at interfaces between bone and air. It does not provide the intrinsic information on electron density, which thereby precludes its use as the sole imaging modality for treatment planning in nasopharyngeal carcinoma (NPC)
An accurate image registration of CT and MRI scans is essential in treatment planning,(2-4) because the complementary information contained in the two modalities can provide more accurate tumor definition.[5,6,7,8,9]
Summary
Correct determination of tumor localization and extension is of major importance in radiation oncology. This is especially true from the perspective of modern radiotherapy (RT) techniques such as 3D conformal and intensity-modulated radiotherapy (IMRT). MR imaging suffers from geometric distortion at the edges of the field of view and are susceptible of artifacts at interfaces between bone and air. It does not provide the intrinsic information on electron density, which thereby precludes its use as the sole imaging modality for treatment planning in NPC. An accurate image registration of CT and MRI scans is essential in treatment planning,(2-4) because the complementary information contained in the two modalities can provide more accurate tumor definition.[5,6,7,8,9]
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