Article

Verification of radiosurgery target point alignment with an electronic portal imaging device (EPID).

Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, USA.
Medical Physics (impact factor: 2.83). 03/1997; 24(2):263-7. pp.263-7
Source: PubMed

ABSTRACT A procedure has been developed using an electronic portal imaging device (EPID) to verify that the center of a patient's lesion is aligned with the center of a treatment cone prior to treatment in a linac-based stereotactic radiosurgery procedure. The coordinates of the lesion center are set on the Brown-Roberts-Wells phantom base using a target simulator. A 3 mm tungsten ball, mounted on the target simulator, is used as the reference point for the planned isocenter. The target simulator is then attached to an adapter mounted on the linac couch, and an EPID image of the simulated target is acquired. The center of the circular-shaped radiation field is calculated from the centroid of the segmented EPID image, and the center of the tungsten ball is identified by an automated computer search algorithm. A summation filter is used to find the position of the lowest radiation intensity coincident with the center of the ball. The alignment error is defined as the difference between the center of the radiation field and the center of the ball. The accuracy of this method was tested and found to be within 0.2 mm. The advantage of the EPID-based procedure is that it can give quantitative offset values quickly for immediate readjustment. We have found that the method is also a convenient tool for testing room laser alignment and the accuracy of the treatment cones.

0 0
 · 
0 Bookmarks
 · 
21 Views
  • Source
    Article: Tumor Localization Using Radio Frequency Implants
    John E. McGary
    [show abstract] [hide abstract]
    ABSTRACT: The first step in the project is to develop the theoretical framework necessary for designing an analog prototype of the localizing transmitter. To date, much of the theoretical foundation is developed to characterize the design parameters of the system including the dipole antenna power support. The design parameters for the system are identified as: the dipole and transmitter inductor radii, inductance, capacitance, and magnetic field strength. Using the size constraints imposed by the implant transmitter, the time scales and associated transmitter field strengths are found to be plausible for a clinical environment. This demonstrates that the concept is possible in terms of physical properties of the system. With this analysis, further details of the system can be derived and an analog system can be created for experimental verification. Additional measurements will be used to supplement theory as empirical models to increase the prediction accuracy for creating a detailed transmitter design.
    02/2005;
  • Source
    Article: Theoretical foundation for real-time prostate localization using an inductively coupled transmitter superconducting quantum interference devices
    J. E. McGary
    Journal of Applied Clinical Medical Physics 04/2004; · 1.29 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.

Keywords

alignment error
 
automated computer search algorithm
 
Brown-Roberts-Wells phantom base
 
circular-shaped radiation field
 
convenient tool
 
electronic portal imaging device
 
EPID-based procedure
 
immediate readjustment
 
lesion center
 
linac couch
 
linac-based stereotactic radiosurgery procedure
 
lowest radiation intensity coincident
 
patient's lesion
 
planned isocenter
 
radiation field
 
reference point
 
simulated target
 
summation filter
 
testing room laser alignment
 
treatment cones
 

L Dong