Avtor/Urednik		Stanescu, Teodor; Hans-Sonke, Jans; Stavrev, Pavel; Fallone, Gino B
Naslov		3T MR-based treatment planning for radiotherapy of brain lesions
Prevedeni naslov		Načrtovanje obsevanja možganskih sprememb s pomočjo 3T MR tehnike
Tip		članek
Vir		Radiol Oncol
Vol. in št.		Letnik 40, št. 2
Leto izdaje		2006
Obseg		str. 125-32
Jezik		eng
Abstrakt		Purpose. The aim of this work is to develop a complete treatment planning procedure for radiation therapy of intracranial lesions based solely on 3T magnetic resonance imaging (MRI), i.e. MRI simulation. Methods. The proposed 3T MR-based radiotherapy treatment planning procedure consists of converting the MR images into CT-like images by assigning electron density information (related to CT values) to organ structures. Firstly, the 3D distortion field present in the MR volumes is determined and rectified by using an in-house developed distortion correction method. The MR volumes are segmented into anatomical structures, i.e. brain, bone and scalp, by using a combination of the "Profile" and Autocontouring" tools available on Pinnacle (Philips Medical Systems) treatment planning system (TPS). Bulk electron density values are assigned to the 3D volumes in Pinnacle by overriding thei default MR values. Once the MR images contain the target volume along with the electron density information, they are ready to be used for dose calculations. The resulting CT+MR and MR only based plans were compared in terms of isodose distributions and dose-volume histrograms (DVHs). For plan ranking we use a tumor-control probability (TCP)-based procedure for heterogeneous irradiation, which does not require the knowledge of radiobiological parameters. Results. For all patients investigated, the 3T MR only and CT+MR-based plans are in good agreement in terms of isodose distributions, DVHs and TCPs (within 1%) following our clinical criteria. Conclusions. The proposed 3T MR only based treatment planning procedure performs as good as the standard clinical procedure that relies on both CT and MR studies. MRI simulation can significantly reduce the patient treatment cost and save staff and machine time, and avoid any errors that may be associated with the image fusion process.
Izvleček		Izhodišča. Namen pričujoče raziskave je bil oblikovati postopek za načrtovanje obsevanja možganskih sprememb s pomočjo 3T magnetne resonančne preiskave (MRI), t.i. MRI simulacije. Metode. Pri načrtovanju obsevanja s 3T MR načinom spremenimo MR slike v CT-ju podobne slike in pri tem uporabimo podatke elektronske gostote organov. Ker pri MR volumnih ugotavljamo 3D izkrivljanje, smo razvili posebno korektivno metodo. Najprej smo MR volumne razdelili glede na anatomske strukture kot so možgani, kosti in koža ter pri tem uporabili orodja programa Pinnacle (Philips Medical Systems), ki je del sistema za načrtovanja obsevanja (treatment planning system - TPS). Izračun smo naredili, ko smo MR slikam določili tarčne volumne z elektronsko gostoto. Primerjali smo načrte obsevanja s pomočjo CT+MR tehnike in samo MR simulacije. Zanimala nas je razporeditev izodoz in dozavolumen histogrami (dose-volume histograms - DVHs). Ob ugotavljanju heterogenosti obsevanja smo ocenjevali verjetnost tumorske kontrole (tumor-control probability - TCP), kar ni zahtevalo poznavanje radiobioloških parametrov. Rezultati. Pri vseh bolnikih smo ugotovili, da so obsevalni načrti s CT+MR tehniko in 3T MR tehniko podobni, bodisi ob primerjavi izodozne distribucije, bodisi DVHs in TCP. Razlike niso bile večje kot 1%, če smo upoštevali naše klinične kriterije. Zaključki. Uporaba predlagane 3T MR tehnike načrtovanja obsevanja je enako natančna kot uporaba kombinacije CT+MR tehnike. MRI simulacija obsevanja lahko poceni obravnavo bolnikov in prihrani čas obravnave, če jo primerjamo s CT+MR tehniko, prav tako pa se lahko izognemo napakam, ki bi lahko nastale pri združevanju CT in MR slik.
Deskriptorji		BRAIN NEOPLASMS RADIOTHERAPY PLANNING, COMPUTER-ASSISTED MAGNETIC RESONANCE IMAGING TOMOGRAPHY, X-RAY COMPUTED PHANTOMS, IMAGING