Generating patient specific pseudo-CT of the head from MR using atlas-based regression

Sjölund, Jens; Forsberg, Daniel; Andersson, Mats; Knutsson, Hans

doi:10.1088/0031-9155/60/2/825

Cited by 134 publications

(124 citation statements)

References 35 publications

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“…While providing promising results, they are not practical since these special sequences are not generally available in clinic. DIR‐based methods have also been explored to generate S‐CT 12 , 13 , 14 , 15 , 16 . However, using DIR algorithms directly 12 , 13 to map HU from the CT images in the atlas library to an S‐CT image suffers from inherent registration errors due to large anatomical differences between different patients.…”

Section: Introductionmentioning

confidence: 99%

MR image‐based synthetic CT for IMRT prostate treatment planning and CBCT image‐guided localization

Chen

Hong

Qin

et al. 2016

J Applied Clin Med Phys

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The purpose of this study was to propose and evaluate a method of creating a synthetic CT (S‐CT) from MRI simulation for dose calculation and daily CBCT localization. A pair of MR and CT images was obtained in the same day from each of 10 prostate patients. The pair of MR and CT images was preregistered using the deformable image registration (DIR). Using the corresponding displacement vector field (atlas‐DVF), the CT image was deformed to the MR image to create an atlas MR‐CT pair. Regions of interest (ROI) on the atlas MR‐CT pair were delineated and used to create atlas‐ROI masks. ‘Leave‐one‐out’ test (one pair of MR and CT was used as subject‐MR and subject‐CT for evaluation, and the remaining 9 pairs were in the atlas library) was performed. For a subject‐MR, autosegmentation and DVFs were generated using DIR between the subject‐MR and the 9 atlas‐MRs. An S‐CT was then generated using the corresponding 9 paired atlas‐CTs, the 9 atlas‐DVFs and the corresponding atlas‐ROI masks. The total 10 S‐CTs were evaluated using the Hounsfield unit (HU), the calculated dose distribution, and the auto bony registration to daily CBCT images with respect to the 10 subject‐CTs. HU differences false(mean±STDfalse) were false(2.4±25.23false), false(1.18±39.49false), false(32.46±81.9false), false(0.23±40.13false), and false(3.74±144.76false) for prostate, bladder, rectal wall, soft tissue outside all ROIs, and bone, respectively. The discrepancy of dose‐volume parameters calculated using the S‐CT for treatment planning was small (≤0.22% with 95% confidence). Gamma pass rate (2% & 2 mm) was higher than 99.86% inside PTV and 98.45% inside normal structures. Using the 10 S‐CTs as the reference CT for daily CBCT localization achieved the similar results compared to using the subject‐CT. The translational vector differences were within 1.08 mm false(0.37±0.23 mmfalse), and the rotational differences were within 1.1° in all three directions. S‐CT created from a simulation MR image using the proposed approach with the preconstructed atlas library can replace the planning CT for dose calculation and daily CBCT image guidance.PACS number(s): 87.57.nf, 87.57.nm

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Section: Introductionmentioning

confidence: 99%

MR image‐based synthetic CT for IMRT prostate treatment planning and CBCT image‐guided localization

Chen

Hong

Qin

et al. 2016

J Applied Clin Med Phys

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“…In this case, localization was typically provided by stereotactic head frame. Efforts have been made to create “synthetic” or “pseudo” CTs from MR images that can be used for dose calculation and localization 7, 8, 9, 10, 11, 12, 13, 14. These methods show promise in terms of geometric and dosimetric accuracy, but are not in widespread clinical use at this time.…”

Section: Introductionmentioning

confidence: 99%

Do we need a new CT scan for retreatment of intracranial SRS patients?

Wiant

Manning

Koch

et al. 2017

J Applied Clin Med Phys

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PurposeTo determine if the treatment planning computed tomography scan (CT) from an initial intracranial stereotactic radiosurgery (SRS) treatment can be used for repeat courses of SRS.Methods and materialsTwenty‐five patients with 40 brain metastases that received multiple courses of SRS were retrospectively studied. Magnetic resonance scans from repeat SRS (rMR) courses were registered to CT scans from the initial SRS (iCT) and repeat SRS (rCT). The CT scans were then registered to find the displacement of the rMR between iCT and rCT registrations. The distance from each target to proximal skull surface was measured in 16 directions on each CT scan after registration. The mutual information (MI) coefficients from the registration process were used to evaluate image set similarity. Targets and plans from the rCTs were transferred to the iCTs, and doses were recalculated on the iCT for repeat plans. The two dose distributions were compared through 3D gamma analysis.ResultsThe magnitude of the mean linear translations from the MR registrations was 0.6 ± 0.3 mm. The mean differences in distance from target to skull on a per target basis were 0.3 ± 0.2 mm. The MI was 0.582 ± 0.042. Registration between a comparison group of 30 CT scans that had the same data resampled and 30 scans that were intercompared with different patients gave MI = 0.721 ± 0.055 and MI = 0.359 ± 0.031, respectively. The mean gamma passing rates were 0.997 ± 0.007 for 1 mm/1% criteria.ConclusionsThe rMR can be aligned to the iCT to accurately define targets. The skull shows minimal change between scans so the iCT can be used for set‐up at repeat treatments. The dosimetry provided by the iCT dose calculation is adequate for repeat SRS. Treatment based on iCT is feasible.

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“…The technique was later extended to the synthesis of images by propagating intensity images instead of segmented images, for example CT images [3]. Multi-atlas CT synthesis methods have been developed for RTP [4][5][6] but only a few have been applied outside of the brain [7,8].…”

Section: Introductionmentioning

confidence: 99%

Joint Segmentation and CT Synthesis for MRI-only Radiotherapy Treatment Planning

Burgos

Guerreiro

McClelland

et al. 2016

Medical Image Computing and Computer-Assisted Intervention – MICCAI 2016

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Abstract. Accurate knowledge of organ location and tissue attenuation properties are the two essential components to perform radiotherapy treatment planning (RTP). Computed tomography (CT) has been the modality of choice for RTP as it easily provides electron density information. However, its low soft tissue contrast limits the accuracy of organ delineation. On the contrary, magnetic resonance (MR) provides images with excellent soft tissue contrast but its use for RTP is limited by the fact that it does not readily provide tissue attenuation information. In this work we propose a multi-atlas information propagation scheme that jointly segments the organs at risk and generates pseudo CT data from MR images. We demonstrate that the proposed framework is able to automatically generate accurate pseudo CT images and segmentations in the pelvic region, bypassing the need for CT scan for accurate RTP.

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Generating patient specific pseudo-CT of the head from MR using atlas-based regression

Cited by 134 publications

References 35 publications

MR image‐based synthetic CT for IMRT prostate treatment planning and CBCT image‐guided localization

MR image‐based synthetic CT for IMRT prostate treatment planning and CBCT image‐guided localization

Do we need a new CT scan for retreatment of intracranial SRS patients?

Joint Segmentation and CT Synthesis for MRI-only Radiotherapy Treatment Planning

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