Direct aperture optimization as a means of reducing the complexity of intensity modulated radiation therapy plans

Intensity Modulated Radiation Therapy (IMRT) is a means of delivering radiation therapy where the intensity of the beam is varied within the treatment field. This is done by dividing a large beam into many small beamlets. Dose constraints are assigned to both the target and sensitive structures and computerised inverse optimization is performed to find the individual weights of this large number of beamlets. The computer adjusts the intensities of these beamlets according to the required planning dose objectives. The optimized intensity patterns are then decomposed into a series of deliverable multi leaf collimator (MLC) shapes in the sequencing step

Daily temperature and pressure series for Salem, Massachusetts (1786-1829)

The digitization and homogenization of a record with four daily thermometer and two daily barometer readings is described for the meteorological journal of Dr. E. A. Holyoke of Salem (Massachusetts). These records begin in January 1786 and span the period to March 1829 for temperature, and the period to December 1820 for pressure. The records are reconstructed and some inhomogeneities are identified and corrected for. The temperature data compares favourably with monthly temperature data from New Haven (Connecticut) and a comparison with independently reconstructed daily pressure data for nearby Cambridge (1780–1789) show that the temporal variations of the data agree very well. It is shown that the number of extremely cold days was considerably greater during 1786–1829 than recent times, while the number of warm days in the early and modern records are comparable. A probability distribution of daily winter pressure values shows a mean of the distribution which is 3 to 4 hPa lower during 1786–1820