There are several other pieces of software that, like SpekCalc, can take a few input parameters and produce an energy spectrum of the emerging X-rays. A number of these - for example, those within the Institute of Physics and Engineering in Medicine's Report 78 - are based on a research paper dating from the late 1970s (R Birch and M Marshall Phys. Med. Biol. 24 505). These programs have been used in hospitals worldwide. So what's different about SpekCalc?
According to Poludniowski, the theory underlying SpekCalc is more comprehensive. "It will also produce results for the high tube voltages used in orthovoltage radiotherapy, something that's not available with most such software utilities," he explained.
Inside any X-ray tube, electrons are accelerated and directed into a metal target. As they hit this metal, the electrons slow down and generate bremsstrahlung. Poludniowski and his colleague Phil Evans published a model for this process in 2007, (Med. Phys. 34 2164; 2175). "We were able to get good agreement with experimental data, without having to resort to the empirical 'fixes' needed in other models such as Birch and Marshall's," Poludniowski told medicalphysicsweb.
Now, Frank Verhaegen and colleagues Guillaume Landry and Francois deBlois, at McGill University in Canada and Maastro Cancer Clinic in the Netherlands, have transferred this physical model into a user-friendly computer program. To perform the calculations, users input data - such as tube voltage, filtration thicknesses and take-off angle - via an intuitive GUI environment and SpekCalc generates the photon fluence spectrum at the click of a button.
SpekCalc has received a steady trickle of downloads in the last few months, and its creators are hoping that "this trickle will become a stream".