Department of Oncology Dedicated Magnetic Resonance Imaging in radiation therapy at Herlev Hospital Faisal Mahmood MR och Strålterapi, Varberg 12. november 2013
Overview MRI projects in radiation therapy at Herlev Hospital MRI QA for radiation planning MRI for treatment response assessment
Why MRI in RT Superior soft tissue contrast cancer diagnostics (No radiation)
The (new) role of MRI in RT From supplement to Planning Delivery Response assessment
Challenges Geometrical distortion CT numbers Unfamiliarity
MRI QA for radiation planning Evaluation, prediction and correction of geometrical distortion in MR images
The need for geometric fidelity MRI simulation MRI - CT co-registration to delineate target (Morphological MRI, physiological MRI ) Electron density assignment to segmented MR images, for MRI based treatment planning.
Geometrical distortions MR imaging principles: Frequency Basic assumptions: Frequency differences are induced by linear gradients only. Violations: B 0 field inhomogeneities, chemical shift differences Gradient are not linear
Geometrical distortions Susceptibility artifact (ferromagnetic)
Aims 1. To determine the degree of geometrical distortion in the RT MRI system. 2. To estimate the degree of geometrical distortion in patients. 3. To suggest an MRI protocol that reduces geometrical distortion
Dedicated 1T MRI system
Methods 2D (or 3D) linearity phantom TRA SAG COR Investigate geometrical distortion in all gradient directions (evaluation) Introduce materials with strong/weak magnetic susceptibility (prediction) Investigate influence of sequence parameters, for example, shape of RF in slice direction, step-and-shoot sequence (correction).
MRI for treatment response assessment Multi parametric diffusion MRI for intra-treatment monitoring of local response of brain metastases to radiation therapy
Strålebehandlingseffekten på Hjernemetastaser Målt med Diffusions MR Faisal Mahmood 1, Helle Hjorth Johannesen 2, Poul Geertsen 1, Rasmus Hvass Hansen 3 1 Onkologisk afd. Herlev Hospital, 2 Nuklearmedicinsk afd. Rigshospitalet, 3 Radiologisk afd. Herlev Hospital HYPOTESE / FORMÅL: Tidlige forandringer i kræftvæv under strålebehandling kan forudsige det langsigtede behandlingsrespons. I dette studie måler vi vands diffusion i kræftvæv vha. MR skanninger og undersøger om dette kan prædiktere strålebehandlingseffekten på hjernemetastaser. Volumetrisk respons ses først uger eller måneder after afsluttet strålebehandling. Cellulære (mikroskopiske) forandringer begynder allerede få sekunder efter bestråling.
DIFFUSION Einstein described the Brownian motion (self-diffusion) in 1905 Gaussian distribution 2D 2 x = 2D x Free Hindered Restricted Gaussian Non-Gaussian
RF reorients spin 90 DIFFUSION WEIGHTED MRI Magnetic Gradient Dephases δ g RF reiorients spin 180 Magnetic Gradient Rephases δ Δ tid No diffusion Diffusion B 0 B 0 SIGNAL B 0 B 0 SIGNAL
GAUSSIAN DIFFUSION METRIC: ADC s( b) = s(0)exp( b ADC) (Stejskal and Tanner 1965) log(s) Apparent Diffusion Coefficient (ADC) b-value
NON-GAUSSIAN METRIC: KURTOSIS (K) log(s) Perfusion K > 0 K < 0 Apparent K > 0 K < 0 Diffusion Coefficient (ADC) High b-value region Non-Gaussian Gaussian b-value
Strålebehandlingseffekten på Hjernemetastaser Målt med Diffusions MR Faisal Mahmood 1, Helle Hjorth Johannesen 2, Poul Geertsen 1, Rasmus Hvass Hansen 3 1 Onkologisk afd. Herlev Hospital, 2 Nuklearmedicinsk afd. Rigshospitalet, 3 Radiologisk afd. Herlev Hospital METODE: Åben MR skanner i stråleterapien T1W+k T2W T2*W DW (b=400) Volumen Ødem Blødning Diffusion
Strålebehandlingseffekten på Hjernemetastaser Målt med Diffusions MR Faisal Mahmood 1, Helle Hjorth Johannesen 2, Poul Geertsen 1, Rasmus Hvass Hansen 3 1 Onkologisk afd. Herlev Hospital, 2 Nuklearmedicinsk afd. Rigshospitalet, 3 Radiologisk afd. Herlev Hospital STATUS / DATA: Atten patienter er inkluderet (okt. 2013). I øjeblikket er data for de første patienter ved at blive evalueret. Forsøget afsluttes når 25 patienter er inkluderet. Dette forventes at være nået inden udgangen af 2013. Anatomisk skanning (venstre) viser metastaser i højre hjernehalvdel før start af stråleterapien. Højre side viser et såkaldt ADC map, som giver et billede af de beregnede diffusions forhold i hjernen, på baggrund af diffusions MR.