Cone Beam CT Image Guidance for Intracranial Stereotactic Treatments: Comparison With a Frame Guided Set-Up

Journal Article · Tue Jul 01 04:00:00 EDT 2008 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/j.ijrobp.2008.03.006· OSTI ID:21124334

Masi, Laura ^[1]; Casamassima, Franco ^[2]; Polli, Caterina; Menichelli, Claudia; Bonucci, Ivano ^[3]; Cavedon, Carlo ^[4]

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1. Medical Physics Department, Casa di Cura S. Chiara, Firenze (Italy)
2. Clinical Radiobiological Institute, University of Firenze, Firenze (Italy)
3. Radiotherapy Department, Casa di Cura S. Chiara, Firenze (Italy)
4. Medical Physics Department, Vicenza Hospital, Vicenza (Italy)

Purpose: An analysis is performed of the setup errors measured by a kV cone beam computed tomography (CBCT) for intracranial stereotactic radiotherapy (SRT) patients immobilized by a thermoplastic mask and a bite-block and positioned using stereotactic coordinates. We evaluated the overall positioning precision and accuracy of the immobilizing and localizing systems. The potential of image-guided radiotherapy to replace stereotactic methods is discussed. Methods and Materials: Fifty-seven patients received brain SRT. After a frame-guided setup, before each fraction (131 fractions), a CBCT was acquired and the detected displacements corrected online. Translational and rotational errors were analyzed calculating overall mean and standard deviation. A separate analysis was performed for bite-block (in conjunction with mask) and for simple thermoplastic mask. Interobserver variability for CBCT three-dimensional registration was assessed. The residual error after correction and intrafractional motion were calculated. Results: The mean module of the three-dimensional displacement vector was 3.0 {+-} 1.4 mm. Setup errors for bite block and mask were smaller (2.9 {+-} 1.3 mm) than those for thermoplastic mask alone (3.2 {+-} 1.5 mm), but statistical significance was not reached (p = 0.15). Interobserver variability was negligible. The maximum margin calculated for residual errors and intra fraction motion was small but not negligible (1.57 mm). Conclusions: Considering the detected setup errors, daily image guidance is essential for the efficacy of SRT treatments when mask immobilization is used, and even when a bite-block is used in conjunction. The frame setup is still used as a starting point for the opportunity of rotational corrections. Residual margins after on-line corrections must be evaluated.

• OSTI ID: 21124334
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 3 Vol. 71; ISSN IOBPD3; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
ACCURACY
BRAIN
COMPUTERIZED TOMOGRAPHY
CORRECTIONS
ERRORS
IMAGE PROCESSING
IMAGES
PATIENTS
RADIOTHERAPY
RESPIRATORS
THERMOPLASTICS