Feasibility of MRI-based reference images for image-guided radiotherapy of the pelvis with either cone-beam computed tomography or planar localization images

Korhonen, Juha; Kapanen, Mika; Sonke, Jan‐Jakob; Wee, Leonard; Salli, Eero; Keyriläinen, Jani; Seppälä, Tiina; Tenhunen, Mikko

doi:10.3109/0284186x.2014.958197

Cited by 41 publications

(58 citation statements)

References 32 publications

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“…figure 3) to be adequate for assessing rectal and bladder filling. Quantitative IGRT results were also reported by Korhonen et al in a separate study (Korhonen et al 2015). The SDs of differences in manual registrations with planar KV and MV localization images using bony match were ≤1.0 mm and ≤1.7 mm respectively.…”

Section: Resultssupporting

confidence: 75%

Dosimetric and workflow evaluation of first commercial synthetic CT software for clinical use in pelvis

et al. 2017

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To evaluate a commercial synthetic CT (syn-CT) software for use in prostate radiotherapy. Twenty-five prostate patients underwent CT and MR simulation scans in treatment position on a 3T MR scanner. A commercially available MR protocol was used that included a T2w turbo spin-echo sequence for soft-tissue contrast and a dual echo 3D mDIXON fast field echo (FFE) sequence for generating syn-CT. A dual-echo 3D FFE B0 map was used for patient-induced susceptibility distortion analysis and a new 3D balanced-FFE sequence was evaluated for identification of implanted gold fiducial markers and subsequent image-guidance during radiotherapy delivery. Tissues were classified as air, adipose, water, trabecular/spongy bone and compact/cortical bone and assigned bulk HU values. The accuracy of syn-CT for treatment planning was analyzed by transferring the structures and plan from planning CT to syn-CT and recalculating the dose. Accuracy of localization at the treatment machine was evaluated by comparing registration of kV radiographs to either digitally reconstructed radiographs (DRRs) generated from syn-CT or traditional DRRs generated from the planning CT. Similarly, accuracy of setup using CBCT and syn-CT was compared to that using the planning CT. Finally, a MR-only simulation workflow was established and end-to-end testing was completed on five patients undergoing MR-only simulation. Dosimetric comparison between the original CT and syn-CT plans was within 0.5% on average for all structures. The de-novo optimized plans on the syn-CT met institutional clinical objectives for target and normal structures. Patient-induced susceptibility distortion based on B0 maps was within 1 mm and 0.5 mm in the body and prostate respectively. DRR and CBCT localization based on MR-localized fiducials showed a standard deviation of <1 mm. End-to-end testing and MR simulation workflow was successfully validated. MRI derived synthetic CT can be successfully used for a MR-only planning and treatment for prostate radiotherapy.

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Section: Resultssupporting

confidence: 75%

Dosimetric and workflow evaluation of first commercial synthetic CT software for clinical use in pelvis

et al. 2017

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“…6,7,[11][12][13] The sCTs can also be used as reference images for image-guided RT. 14 Thus, the entire RTP workflow can be conducted with MRI only. 15 At certain clinics, the prostate MRI only workflow has been used for standard clinical practice since 2012.…”

Section: Introductionmentioning

confidence: 99%

Registration free automatic identification of gold fiducial markers in MRI target delineation images for prostate radiotherapy

et al. 2017

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Purpose: The superior soft tissue contrast of magnetic resonance imaging (MRI) compared to computed tomography (CT) has urged the integration of MRI and elimination of CT in radiotherapy treatment (RT) for prostate. An intraprostatic gold fiducial marker (GFM) appears hyperintense on CT. On T2-weighted (T2w) MRI target delineation images, the GFM appear as a small signal void similar to calcifications and post biopsy fibrosis. It can therefore be difficult to identify the markers without CT. Detectability of GFMs can be improved using additional MR images, which are manually registered to target delineation images. This task requires manual labor, and is associated with interoperator differences and image registration errors. The aim of this work was to develop and evaluate an automatic method for identification of GFMs directly in the target delineation images without the need for image registration. Methods: T2w images, intended for target delineation, and multiecho gradient echo (MEGRE) images intended for GFM identification, were acquired for prostate cancer patients. Signal voids in the target delineation images were identified as GFM candidates. The GFM appeared as round, symmetric, signal void with increasing area for increasing echo time in the MEGRE images. These image features were exploited for automatic identification of GFMs in a MATLAB model using a patient training dataset (n = 20). The model was validated on an independent patient dataset (n = 40). The distances between the identified GFM in the target delineation images and the GFM in CT images were measured. A human observatory study was conducted to validate the use of MEGRE images. Results: The sensitivity, specificity, and accuracy of the automatic method and the observatory study was 84%, 74%, 81% and 98%, 94%, 97%, respectively. The mean absolute difference in the GFM distances for the automatic method and observatory study was 1.28 AE 1.25 mm and 1.14 AE 1.06 mm, respectively. Conclusions: Multiecho gradient echo images were shown to be a feasible and reliable way to perform GFM identification. For clinical practice, visual inspection of the results from the automatic method is needed at the current stage.

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“…We envisage that an efficient MRI-alone treatment workflow for prostate cancer (Refs. [14][15][16][17] will involve seven main stages: 1. MRI scan acquisition (in treatment position); 2. automatically contoured organs; 3. automatically contoured gold seed locations; 4. sCT generation from MRI; 5. manual quality assurance of automatic contours; 6. dose planning conducted from the sCT; and 7. patient setup and treatment at a linear accelerator (using sCT-based DRRs with seed positions for position verification).…”

Section: Introductionmentioning

confidence: 99%

MRI-alone radiation therapy planning for prostate cancer: Automatic fiducial marker detection

et al. 2016

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An novel automatic framework for gold fiducial marker detection in MRI is proposed and evaluated with detection accuracies comparable to manual detection. When radiation therapists are unable to determine the seed location in MRI, they refer back to the planning CT (only available in the existing clinical framework); similarly, an automatic quality control is built into the automatic software to ensure that all gold seeds are either correctly detected or a warning is raised for further manual intervention.

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Feasibility of MRI-based reference images for image-guided radiotherapy of the pelvis with either cone-beam computed tomography or planar localization images

Abstract: This study demonstrated that it is feasible to conduct IGRT of the pelvis with MRI-based reference images.

Cited by 41 publications

References 32 publications

Dosimetric and workflow evaluation of first commercial synthetic CT software for clinical use in pelvis

Dosimetric and workflow evaluation of first commercial synthetic CT software for clinical use in pelvis

Registration free automatic identification of gold fiducial markers in MRI target delineation images for prostate radiotherapy

MRI-alone radiation therapy planning for prostate cancer: Automatic fiducial marker detection

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