[Treatment planning with functional MRI].
OBJECTIVE
The aim of magnetic resonance imaging (MRI) guided radiotherapy is high precision in treatment delivery. With new developments it is possible to focus the high dose irradiation on the tumor while sparing the surrounding tissue. The achievements in precision of the treatment planning and delivery warrant equally precise tumor definition.


METHODS
In conventional radiation therapy it is necessary to carry out a planning computed tomography (CT). For many tumors there is also need for an additional morphological MRI because of more accurate tumor definition. In standard radiotherapy the tumor volume is irradiated with a homogeneous dose.


METHODS
The aim of functional multiparametric MRI is to visualize and quantify biological, physiological and pathological processes at the cellular and molecular levels. Based on this information it is possible to elucidate tumor biology and identify subvolumes of more aggressive behavior. They are often radiotherapy-resistant, leading to tumor recurrence thus requiring further dose escalation. The concept of inhomogeneous tumor irradiation according to its biological behavior is called dose painting.


METHODS
Dose painting is technically feasible. The expected clinical benefit is motivated by selective treatment adaptations based on biological tumor characteristics. Tumors show variable response to therapy underlining the need for individual treatment plans. This approach may lead not only to higher local control but also to better sparing of normal surrounding tissue.


RESULTS
With the clinical implementation of dose painting, improvements in the therapeutic outcome can be expected.


CONCLUSIONS
Due to the existing technical challenges, extensive collaboration between radiation oncologists, radiologists, medical physicists and radiation biologists is needed.
EBG MedAustron GmbH, Marie-Curie-Straße 5, 2700, Wiener Neustadt, Österreich. petra.georg@medaustron.at.|Christian Doppler Labor für die Medizinische Strahlenforschung, Medizinische Universität Wien, Wien, Österreich. petra.georg@medaustron.at.
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P
Georg
Christian Doppler Labor für die Medizinische Strahlenforschung, Medizinische Universität Wien, Wien, Österreich.|Abteilung für medizinische Strahlenphysik, Univ. Klinik für Strahlentherapie, Medizinische Universität Wien, Wien, Österreich.
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Andrzejewski
Christian Doppler Labor für die Medizinische Strahlenforschung, Medizinische Universität Wien, Wien, Österreich.|Abteilung für molekulare Bildgebung, Univ. Klinik für Radiologie und Nuklearmedizin, Medizinische Universität Wien, Wien, Österreich.
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Pinker
Christian Doppler Labor für die Medizinische Strahlenforschung, Medizinische Universität Wien, Wien, Österreich.|Abteilung für medizinische Strahlenphysik, Univ. Klinik für Strahlentherapie, Medizinische Universität Wien, Wien, Österreich.
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Georg
D005060:Europe; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009369:Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy*; D017410:Practice Guidelines as Topic; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*
Dose painting; Functional magnetic resonance imaging; Image guided radiotherapy; Intensity modulated radiotherapy; Ion beam therapy