| Part OneDCE-MRI Monitoring Blood-Tumor-Barrier Opening in Brain Metastases after Radiation TherapyPurpose:Blood-tumor barrier(BTB)is a limiting factor for effectiveness of systemic therapy to brain metastases(BM).This study aimed to assess the extent and time course of BTB opening in BM following whole-brain radiotherapy(WBRT)or stereotactic radiosurgery(SRS)to deternirie the optimal timing for systemic therapy.Materials and Method:30 patients received WBRT or SRS and a total of 64 metastatic lesions were analyzed.Dynamic contrast-enhanced(DCE)-MRI were acquired,to quantify a transfer constant(Ktrans),pre-RT,1-2 weeks after starting RT(Wk 1-2),and 1-month post-RT(1M-post).Lesions were categorized as either low or high permeability based upon the pre-RT percentage volume of a lesion with Ktrans>0.005 min-1(%Vall)less or greater than 50%.Time-course changes of%Vaii after RT were analyzed.Results:In the low-permeability lesions,%Vall increased from a pre-RT mean value of 6.4%to 30.2%at Wk1-2(p=0.1)and further to 52.6%1M-post(p=0.01).In the high-permeability tumors.%Vall decreased non-significantly following RT(from 81.6%pre-RT to 75.6%1M-post).Also,a heterogeneous RT response was noted in different lesions within the same patients.Conclusion:There may be an optimal time-window for combining systemic therapy with RT,especially for the initial low permeability lesions.Part TwoImplications of FDG-PET,DCE MRI and DWI in Head-and-neck Cancer Patients for Dose PaintingPurpose:The central question in dose painting for head-and-neck cancer(HNC)is to identify the highly resistant tumor subvolumes and thereby targeted for boosting.A number of promising medical imaging modalities identified spatial variation in resistance to therapy,including 18F-deoxyglucose-positron emission tomography(18F-FDG-PET),dynamic contrast enhanced-magnetic resonance imaging(DCE-MRI)and diffusion weighted-MRI(DWI).Most current ongoing clinical trials used single imaging modality to guide dose painting.However,the spatial relationship between them is still unclear.Therefore,this study aimed to identify whether FDG-PET,DCE MRI and DWI identify the same or different regions for dose painting and the correlations between these imaging indicators.Materials and methods:Forty patients with advanced HNC were enrolled in an IRB-approved randomized phase ? clinical trial.FDG-PET/CT,DCE MRI and DW-MRI scans were performed before treatment.All image volumes were registered to the contrast-enhanced T1-weighted volume.Gross tumor volume(GTV)was contoured based on contrast-enhanced T1-weighted images by a radiation oncologist.Subvolumes with standard uptake value(SUV)value above the SUV50%max were generated as metabolic tumor volume(MTV50%).Low blood tumor volume(LBV)was defined as BV<7.636 ml/100g within GTV.Low ADC tumor volume(LADCV)was defined as ADC>0.1×10-6mm2/s and<1200×10-6mm2/s within GTV.Overlaps between GTV,MTV50%,LBV and LADCV were calculated.The correlations between each two imaging modalities were analyzed voxel by voxel by using single line regression coefficient(R).Results:Forty patients with FDG-PET and DCE MRI were included in the analysis and 32 patients were included in the ADC map analysis.The median values of GTV,MTV50%,LBV and LADCV were 69.1,15.5,10.9 and 25.9 cc,respectively.MTV and LBV contoured different subvolumes with relatively small overlap between them,as 10.3%(0-77.7%).The R values ranged from-0.14 to 0.55 between SUV and BV within GTV for each patient,with the median value of 0.11.However,the overlap between MTV50%and LADCV was much larger,as 46.1%(3.8%-93.0%).Most patients(30/32)showed negative correlations between SUV and ADC,with the median R value of-0.37(-0.61-0.16).Conclusion:FDG-PET,DCE-MRI and DWI provided different information in HNC and single imaging modality may be in sufficient for dose painting in HNSCC.Boosting targets based on DCE-MRI were different with those based on FDG-PET and DWI,which may lead to different clinical outcomes. |
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