Estimation of medical linear accelerator bremsstrahlung spectra

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5647532

Dawson, J E.B.

Improved characterization of the x-ray spectra of medical linear accelerators would improve the accuracy of several procedures that are involved in the radiation treatment of a patient with such units. Because of the experimental difficulties in measuring these spectra, reconstruction techniques such as attention analysis are quite attractive for characterization of the x-ray spectrum of a megavoltage unit. In the present work, the limitations of the current Laplace reconstruction methods to determine the bremsstrahlung spectrum form a medical linear accelerator through the analysis of transmission data are studied. The ill-posedness of the problem is analyzed, and the use of regularization is examined. The regularization technique is applied to simulated and actual transmission data from a 4 MeV x-ray linear accelerator, and the effect on the reconstruction of noise in the data is analyzed. To determine an optimal choice for the regularization parameter the discrepancy criterion and the cross validation method are used. The possibility of choosing this parameter by comparison to a standard is evaluated for its possible use in establishing the constancy of the peak energy of the beam in quality assurance studies. Results indicate that it is possible to determine the peak of the spectrum within 50 keV. The stability of the results makes regularization a valuable tool in quality assurance where the constancy of the beam energy is currently established by percentage depth dose (or other similar measurements). With good data, regularization predicts both the peak and the value of {vert bar}F{sub T}(E){vert bar} quite well.

• Research Organization: Missouri Univ., Columbia, MO (United States)
• OSTI ID: 5647532
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
430100* -- Particle Accelerators-- Design
Development
& Operation
ACCELERATORS
ACCURACY
BREMSSTRAHLUNG
DATA ANALYSIS
ELECTROMAGNETIC RADIATION
INTEGRAL TRANSFORMATIONS
LAPLACE TRANSFORMATION
LINEAR ACCELERATORS
MEDICINE
NOISE
NUCLEAR MEDICINE
QUALITY ASSURANCE
RADIATIONS
RADIOLOGY
RADIOTHERAPY
SPECTRA
STABILITY
THERAPY
TRANSFORMATIONS
X-RAY SPECTRA