From the Dual-Energy CT scan, two CT images, generated with different X-ray spectra, are available for further processing. They contain substantially more information on required tissue characteristics than with the previous standard method using conventional CT. Nevertheless, patients are not exposed to a higher X-Ray dose compared to conventional CT. The only difference is that they are moved twice through the CT scanner.

The scientists in Dresden were also able to prove that the advantage of the previous method for calculating range and dose is not only theoretical, but that it is clinically highly relevant. "We have seen that the comprehensively validated DirectSPR approach, that was already proven to be more accurate, results in a proton range that is four to eight millimeters different from the previous standard method - for deep-seated tumors. At that moment, the high clinical relevance of this innovation was immediately clear to us," says Prof. Esther Troost, Director of the Department of Radiotherapy and Radiation Oncology at the University Hospital Dresden and head of the research group “Image-guided High Precision Radiotherapy” at the HZDR.


"As the results of the studies were so unequivocal, we wanted our patients to benefit from the new approach as quickly as possible. The lower radiation volume, for example in the brain, allows an even better protection of important neurological structures, such as the brain stem or the optic nerves. Thereby, we reduce side effects and make proton therapy even more tolerable for each individual patient," adds Prof. Mechthild Krause, also Director of the Department of Radiotherapy and Radiation Oncology at Dresden University Hospital and Director of the OncoRay Center. In concrete terms, this means a reduction of the safety margin for prostate treatments by around 35 percent, for brain tumor treatments even up to 40 percent.

As early as 2015, scientists from the German Cancer Research Center (DKFZ) in Heidelberg together with colleagues from Dresden developed and optimized the calculation algorithm. With DirectSPR, the relative electron density and the effective atomic number are determined individually in each voxel and are then used to determine the stopping behavior, the so-called stopping power, of the tissue. The abbreviation SPR stands for "Stopping Power Ratio" and expresses the energy loss of the protons per distance travelled relative to the energy loss in water.

Rad Oncology Homepage