Department of Physics

An improved method is introduced for prediction of local tumor control following lung
stereotactic body radiation therapy (SBRT) for early stage non-small cell lung cancer
(NSCLC) patients using 18F-fluorodeoxyglucose positron emission tomography (18F-FDG
PET). A normalized background-corrected tumor maximum Standard Uptake Value
(SUVcmax) is introduced using the mean uptake of adjacent aorta (SUVref), instead of
the maximum uptake of lung tumor (SUVmax). This method minimizes the variations
associated with SUVmax and objectively demonstrates a strong correlation between the
low SUVcmax (< 2.5-3.0) and local control of post lung SBRT. The false positive rates
of both SUVmax and SUVcmax increase with inclusion of early (<6 months) PET scans,
therefore such inclusion is not recommended for assessing local tumor control of post
lung SBRT.

The coupled equations of motion describing electrostatic plasma oscillations
are derived using a collective coordinate approach. The
boundary between the physical and nonphysical regions of phase space
is discussed. The two mode case is studied in detail for both small
and large initial disturbances. For small initial disturbances the
motion was found to be periodic. For large initial disturbances, non-periodic
growing solutions were found that approached one of two
asymptotic limits. For these solutions, the variables became infinitely
large in a finite time.