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Fewer Sessions Needed for Radiation Therapy

Siemens Healthcare recently introduced a new method that can shorten the time needed to treat cancer with radiation by up to 80 percent. Instead of about 30 treatment fractions over a period of six weeks, ten or fewer fractions are required using the new method, depending on the duration of the treatment. Known as Multiple-X(TM), the new feature makes it possible to use a radiation dose rate up to 2,000 monitor units (MU) per minute instead of the usual 50 to 500 MUs. The high dose rate may increase the effectiveness of the radiation and shorten the treatment time. This improved feature especially benefits patients undergoing stereotaxy - a highly precise radiation therapy method in which the patient is treated on the examination table for up to 60 minutes.

Radiation therapy involves the use of ionizing, highly energetic particles and X-radiation beams for therapeutic purposes. When radiation strikes a tumor, the latter's genetic material is modified in such a way that the tumor cells no longer divide but die instead. Healthy cells, by contrast, are damaged to a much lesser degree and regenerate more quickly, since their biochemical repair system functions much more efficiently. To ensure that as little healthy tissue is affected as possible, a multileaf collimator precisely adjusts the radiation beam in line with the tumor's size and shape. A flattening filter homogenizes the distribution of the energy across the beam's diameter.

However, such flattening is not needed for the highly precise, intensity-modulated radiation therapy (IMRT) in which the tumor is radiated from different directions in arcs. The lack of flattening makes it possible to use a wider radiation energy spectrum, enabling high dose rates of 2,000 MUs per minute. Because tumors are radiated with different levels of x-radiation energy depending on their type and location, Multiple-X supplies four different levels of energies without a flattening filter. However, Multiple-X continues to provide one flattened energy for 3D-conformal treatment and treatments where the flatten beams are desired such as with a large treatment area for irradiation from a single direction.

Multiple-X is a new feature for Siemens' Artiste linear accelerator, into which it can be retrofitted. The new method was presented at this year's congress of the European Society for Therapeutic Radiology and Oncology (ESTRO).

Photo: http://www.siemens.com/press/en/presspicture/?press=/en/presspicture/innovationnews/2011/in20110703-01.htm

idw :: 17.07.2011

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