Precise positioning of intracranial small tumors to the linear accelerator's isocenter, using a stereotactic radiotherapy computed tomography system (SRT-CT).
RT-CT was developed as a simulator using CT scan for radiotherapy. Following three-dimensional treatment planning using CT images, the treatment center and treatment fields are projected to the patients' surface by laser beam on the C arm. The prototype had an accuracy of 3 mm which was equivalent to conventional X-ray simulators but was not adequate for use in stereotactic radiotherapy. A new RT-CT system was developed to have a precise localization capability for stereotactic radiotherapy. Using this stereotactic RT-CT (SRT-CT) after three-dimensional planning, the treatment center is projected to the stereotactic frame automatically. In this study, the values of the x, y and z coordinates of the target center determined by SRT-CT are compared with those determined by the traditional method using CT localizing plates. The discrepancies were within 1.0 mm in 90% and 1.5 mm in 100% of 30 measurements in 16 patients. The disadvantages of SRT-CT may be that the accuracy of localization depends on the quality of calibration of laser beams. The traditional CT localizing method has superiority over SRT-CT because of its solid coordinates but its accuracy is vulnerable to alignment of CT fiducial marker plates. Therefore, the SRT-CT and traditional CT localizing methods would be complementary to each other for precise localization.
Shirato
H
H
Department of Radiology, Faculty of Medicine, Hokkaido University, Sapporo, Japan.
Suzuki
K
K
Nishioka
T
T
Kamada
T
T
Kagei
K
K
Kitahara
T
T
Morisawa
H
H
Tsujii
H
H
D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy / Q000601:surgery*; D002138:Calibration; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007834:Lasers; D008961:Models, Structural; D010315:Particle Accelerators; D010347:Patient Care Planning; D016634:Radiosurgery / Q000295:instrumentation / Q000379:methods*; D011879:Radiotherapy Dosage; D011881:Radiotherapy, Computer-Assisted; D011882:Radiotherapy, High-Energy / Q000295:instrumentation / Q000379:methods; D013238:Stereotaxic Techniques / Q000295:instrumentation; D014057:Tomography, X-Ray Computed