Investigation of magnetic resonance imaging for prostate radiation therapy planning with cone-beam CT-based image guided radiation therapy

1 1 . Introduction and Theory . 3 1.1 – Background and Aims of the Thesis . 3 1.1.1 – Aims of the Thesis . 3 1.1.2 – Format of the Thesis . 4 1.1.3 – Publications and Contributions . 4 1.1.4 – Conference Presentations . 6 1.2 – Anatomy of the Prostate . 7 1.3 – Prostate Cancer . 8 1.3.1 – Prostate Cancer Statistics . 8 1.3.2 – Location and Staging of Prostate Cancer . 9 1.4 – External Beam Radiotherapy (EBRT) . 10 1.4.1 – Overview of the Radiotherapy Process . 10 1.4.2 – Treatment Planning . 12 1.4.3 – Dose Calculation . 17 1.4.4 – Radiotherapy Treatment of Prostate Cancer . 19 1.5 – Image Guided Radiation Therapy and Adaptive Radiotherapy . 24 2 . Literature Review . 29 2.1 – Tissue Segmentation . 29 2.2 – MR Distortions . 33 2.2.1 – General Distortion Correction . 33 2.2.2 – Correction of Motion Artefacts . 36 2.3 – MR-Based DRRs and Bulk Electron Density Planning . 37 2.4 – CT Atlases and Possible Image Registration Techniques . 44 2.5 – Image Guided Radiotherapy (IGRT) and Adaptive Radiotherapy (ART) . 46 2.6 – Electron Density Information in Cone Beam CT Images . 48 2.7 – Summary . 51 3 . MR Uniformity Measurements . 52 3.1 – Overview . 52 3.2 – Methods . 52 3.3 – Results . 57 3.4 – Discussion . 62 4 . Planning With Bulk Electron Densities . 64 4.1 – Overview . 64 4.2 – Methods . 64 4.2.1 – Patient Acquisition and Planning . 64 4.2.2 – Calculation of Bulk Electron Density Values . 70 4.2.3 – Comparison of CT and MR Plans With Bulk Electron Densities (Assigned to Manually Defined Bone Contours) to the Gold-Standard FullDensity CT Plan . 72 4.2.4 – Point Dose Comparisons . 73 4.2.5 – Dose Volume Histogram (DVH) Comparisons . 73 4.2.6 – Dose Distribution Comparison . 74 4.2.7 – Contour, Organ Volume, Source to Surface Distance (SSD), and Skin Marker Comparisons . 75 4.2. 8 – Dose Comparisons For Bulk Density Plans Generated With Automatic Bone Contours to Bulk-Density Plans Generated With Manually Contoured Bone . 78 4.2. 9 – Digitally Reconstructed Radiographs (DRRs) . 78 4.3 – Results . 79 4.3.1 – Calculation of Bulk Electron Density Values . 79 4.3.2 – Point Dose Comparisons . 80 4.3.3 – Dose Volume Histogram (DVH) Comparisons . 83 4.3.4 – Dose Distributions Comparison . 90 4.3. 5 – Contour, Source to Surface Distance (SSD), and Skin Marker Measurements . 95 4.3. 6 – Dose Comparisons For Bulk Density Plans Generated With Automatic Bone Contours to Bulk-Density Plans Generated With Manually Contoured Bone . 102 4.3. 7 – Digitally Reconstructed Radiographs (DRRs) . 104 4.4 – Discussion . 109 4.4.1 – Calculation of Bulk Electron Density Values . 109 4.4.2 – Point Dose Comparisons . 111 4.4.3 – Dose Volume Histogram (DVH) Comparisons . 114 4.4.4 – Dose Distribution Comparison . 116 4.4. 5 – Contour, Organ Volume, Source to Surface Distance (SSD), and Skin Marker Measurements . 118 4.4. 6 – Dose Comparisons for Bulk Density Plans Generated With Automatic Bone Contours to Bulk-Density Plans Generated With Manually Contoured Bone . 122 4.4. 7 – Digitally Reconstructed Radiographs (DRRs) . 122 5 . Planning With Pseudo CTs . 124 5.1 – Overview . 124 5.2 – Methods . 124 5.3 – Results . 125 5.4 – Discussion . 128 6 . Image-Guided Radiation therapy Using Cone-Beam CT . 129 6.1 – Overview . 129 6.2 – Methods . 129 6.2.1 – Cone Beam CT Patient Acquisition and Planning . 129 6.2.2 – Image Guided Radiation Therapy (IGRT) on Cone Beam CT Images . 130 6.2.3 – Application of Bulk Electron Densities to Cone Beam CT Images . 131 6.3 – Results . 132 6.3.1 – Image Guided Radiation Therapy (IGRT) on Cone Beam CT Plans . 132 6.3.2 – Application of Bulk Electron Densities to Cone Beam CT Images . 137 6.4 – Discussion . 144 6.4.1 – Image Guided Radiation Therapy (IGRT) on Cone-Beam CT Images . 144 6.4.2 – Application of Bulk Electron Densities to Cone Beam CT Images . 147 6.4.3 – Acquisition of Cone Beam CT Images With MR Images . 149 7 . Test of the Entire MR-Based Workflow . 150 7.1 – Overview . 150 7.2 – Test of Entire MR-Based Workflow . 150 7.3 – Results . 154 7.4 – Discussion . 160 8 . Summary and Future Work . 162 9 . Appendices .