Which is the most suitable number of photon beam portals in coplanar radiation therapy?
- Univ. of Stockholm (Sweden)
Computer-controlled milling machines for compensator manufacture, dynamic multileaf collimators, and narrow scanned electron or bremsstrahlung photon beams have opened up new possibilities to shape nonuniform fluence profiles and have thus, paved the road for truly three dimensional (3D) dose delivery. The present paper investigates the number of beam portals required to optimize coplanar radiation therapy using uniform and nonuniform dose delivery. Nonuniform dose delivery allows a considerable improvement in the treatment outcome compared to uniform dose delivery. The results also show a close relationship between the dose distribution parameters and the probability of achieving complication-free tumor control. To achieve optimal expectation value of the treatment outcome, within an accuracy of a few percent as measured by the probability of achieving complication-free tumor control, it is generally sufficient to use three nonuniform beam portals. A very large number of coplanar beams may only raise the probability of achieving complication-free tumor control by 1 to 2%. However, good treatment outcome with three beam portals requires that the directions of incidence of the coplanar nonuniform beams are optimally selected. If, on the other hand, the treatment is performed using uniform beams, it is not possible, even with an infinite number of fields, to obtain as high a level of complication-free tumor control as with a few nonuniform beams. From an optimization point of view, it is sufficient to reach a relative standard deviation of the mean dose to the target volume of around 3%. Improved dose homogeneity beyond this level will, in general, not significantly improve the complication-free tumor control. 20 refs., 5 figs., 2 tabs.
- OSTI ID:
- 430959
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 33, Issue 1; Other Information: PBD: 30 Aug 1995
- Country of Publication:
- United States
- Language:
- English
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