Description and assessment of a registration-based approach to include bones for attenuation correction of whole-body PET/MRI

Marshall, Howard; Patrick, John; Laidley, David; Prato, Frank S.; Butler, John; Théberge, Jean; Thompson, R. Terry; Stodilka, Robert Z.

doi:10.1118/1.4816301

Cited by 32 publications

(38 citation statements)

References 38 publications

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“…Various strategies were proposed to incorporate bone tissue in PET/MRI attenuation maps in whole-body imaging ( Hofmann et al, 2011 ;Bezrukov et al, 2015 ;Ay et al, 2014 ;Arabi and Zaidi, 2016a ;Bezrukov et al, 2013 ;Marshall et al, 2013 ;Paulus et al, 2015 ). In whole-body imaging, almost all proposed methods, except joint attenuation-activity reconstruction techniques, rely on prior knowledge present in atlas images to predict bone from MRI.…”

Section: E-mail Address: Habibzaidi@hcugech (H Zaidi)mentioning

confidence: 99%

“…Basically two categories have emerged: atlas-guided attenuation map generation approaches ( Hofmann et al, 2011 ;Bezrukov et al, 2013 ;Arabi and Zaidi, 2016a ;Marshall et al, 2013 ;Arabi and Zaidi, 2016b ) and emission-based approaches ( Rezaei et al, 2012 ;Mehranian and Zaidi, 2015 ). Atlas-guided methods primarily rely on prior information provided by registration of an atlas into target image coordinates to allow classification of bone tissues.…”

Section: E-mail Address: Habibzaidi@hcugech (H Zaidi)mentioning

confidence: 99%

“…Here, the ranking process was repeated three times using the NMI, NCC and MSD similarity measures and for each one the optimum parameter a , which maximized the accuracy of segmented bone was determined. In some studies, the most similar subject is selected for either MRI segmentation or attenuation map generation in PET/MRI to reduce the computation time ( Rohlfing et al, 2004a ;Marshall et al, 2013 ). The most similar atlas can be determined before the registration process on the basis of meta-data and image processing features ( Marshall et al, 2013 ).…”

Section: Sdmentioning

confidence: 99%

“…In whole-body imaging, Hofmann et al (2011 ) proposed an atlas-based method combined with a pattern recognition technique, which resulted in less than 10% uptake error on average, thus outperforming standard segmentation methods in whole-body imaging. Marshall et al (2013 ) evaluated a method enabling to incorporate bony structures into attenuation maps based on a fast atlas-based approach. By including bone, the magnitude of the relative error was reduced to a range acceptable in clinical setting.…”

Section: E-mail Address: Habibzaidi@hcugech (H Zaidi)mentioning

confidence: 99%

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Comparison of atlas-based techniques for whole-body bone segmentation

Arabi

Zaidi

2017

Medical Image Analysis

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a b s t r a c tWe evaluate the accuracy of whole-body bone extraction from whole-body MR images using a number of atlas-based segmentation methods. The motivation behind this work is to find the most promising approach for the purpose of MRI-guided derivation of PET attenuation maps in whole-body PET/MRI. To this end, a variety of atlas-based segmentation strategies commonly used in medical image segmentation and pseudo-CT generation were implemented and evaluated in terms of whole-body bone segmentation accuracy. Bone segmentation was performed on 23 whole-body CT/MR image pairs via leave-one-out cross validation procedure. The evaluated segmentation techniques include: (i) intensity averaging (IA), (ii) majority voting (MV), (iii) global and (iv) local (voxel-wise) weighting atlas fusion frameworks implemented utilizing normalized mutual information (NMI), normalized cross-correlation (NCC) and mean square distance (MSD) as image similarity measures for calculating the weighting factors, along with other atlas-dependent algorithms, such as (v) shape-based averaging (SBA) and (vi) Hofmann's pseudo-CT generation method. The performance evaluation of the different segmentation techniques was carried out in terms of estimating bone extraction accuracy from whole-body MRI using standard metrics, such as Dice similarity (DSC) and relative volume difference (RVD) considering bony structures obtained from intensity thresholding of the reference CT images as the ground truth. Considering the Dice criterion, global weighting atlas fusion methods provided moderate improvement of whole-body bone segmentation (DSC = 0.65 ± 0.05) compared to non-weighted IA (DSC = 0.60 ± 0.02). The local weighed atlas fusion approach using the MSD similarity measure outperformed the other strategies by achieving a DSC of 0.81 ± 0.03 while using the NCC and NMI measures resulted in a DSC of 0.78 ± 0.05 and 0.75 ± 0.04, respectively. Despite very long computation time, the extracted bone obtained from both SBA (DSC = 0.56 ± 0.05) and Hofmann's methods (DSC = 0.60 ± 0.02) exhibited no improvement compared to non-weighted IA. Finding the optimum parameters for implementation of the atlas fusion approach, such as weighting factors and image similarity patch size, have great impact on the performance of atlas-based segmentation approaches. The voxel-wise atlas fusion approach exhibited excellent performance in terms of cancelling out the non-systematic registration errors leading to accurate and reliable segmentation results. Denoising and normalization of MR images together with optimization of the involved parameters play a key role in improving bone extraction accuracy.

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Section: E-mail Address: Habibzaidi@hcugech (H Zaidi)mentioning

confidence: 99%

Section: E-mail Address: Habibzaidi@hcugech (H Zaidi)mentioning

confidence: 99%

Section: Sdmentioning

confidence: 99%

Section: E-mail Address: Habibzaidi@hcugech (H Zaidi)mentioning

confidence: 99%

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Comparison of atlas-based techniques for whole-body bone segmentation

Arabi

Zaidi

2017

Medical Image Analysis

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“…Our findings corroborate the notion that the high electron density of cortical bone substantially attenuates PET photons arising within the marrow space, resulting in lower SUVs for bone lesions when MRI-based AC is used in place of CTbased AC. Novel approaches to AC for PET/MRI, including atlas-based methods, CT co-registration, and segmentation algorithms employing ultrashort echo times to detect MR signal from cortical bone, may soon be widely available to correct this problem [16][17][18][19].…”

Section: Discussionmentioning

confidence: 99%

Conspicuity of FDG-Avid Osseous Lesions on PET/MRI Versus PET/CT: a Quantitative and Visual Analysis

Fraum

Fowler

McConathy

2016

Nucl Med Mol Imaging

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Background Because standard MRI-based attenuation correction (AC) does not account for the attenuation of photons by cortical bone, PET/MRI may have reduced sensitivity for FDG-avid focal bone lesions (FFBLs). This study evaluates whether MRI-based AC compromises detection of FFBLs, by comparing their conspicuity both quantitatively and qualitatively on PET/MRI versus PET/CT. Methods One hundred ninety general oncology patients underwent whole-body PET/CT followed by whole-body PET/MRI, utilizing the same FDG dose. Thirteen patients with a total of 50 FFBLs were identified. Using automated contouring software, a volumetric contour was generated for each FFBL. Adjacent regions of normal background bone (BB) were selected manually. For each contour, SUV-max and SUV-mean were determined. Lesion-to-background SUV ratios served as quantitative metrics of conspicuity. Additionally, two blinded readers evaluated the relative conspicuity of FFBLs on PET images derived from MRI-based AC versus CT-based AC. Visibility of an anatomic correlate for FFBLs on the corresponding CT and MR images was also assessed. Results SUV-mean was lower on PET/MRI for both FFBLs (-6.5 %, p = 0.009) and BB (-20.5 %, p < 0.001). SUV-max was lower on PET/MRI for BB (-14.2 %, p = 0.002) but not for FFBLs (-6.2 %, p = 0.068). The ratio of FFBL SUV-mean to BB SUV-mean was higher for PET/MRI (+29.5 %, p < 0.001). Forty of 50 lesions (80 %) were visually deemed to be of equal or greater conspicuity on PET images derived from PET/MRI. Thirty-five of 50 FFBLs (70 %) had CT correlates, while 40/50 FFBLs (80 %) had a correlate on at least one MRI sequence. The mean interval from tracer administration to imaging was longer (p < 0.001) for PET/MRI (127 v. 62 min). Conclusions Both FFBLs and BB had lower mean SUVs on PET/MRI than PET/CT. This finding was likely in part due to differences in the handling of cortical bone by MRI-based AC versus CT-based AC. Despite this systematic bias, FFBLs had greater conspicuity on PET/MRI, both qualitatively and quantitatively. This difference was likely due to the longer tracer uptake times for PET/MRI, which allowed for more tracer accumulation by FFBLs and more tracer washout from BB. Our results suggest that whole-body PET/MRI and PET/CT provide comparable sensitivity for detection of FDG-avid focal bone lesions.

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PET/MRI attenuation estimation in the lung: A review of past, present, and potential techniques

et al. 2020

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Positron emission tomography/magnetic resonance imaging (PET/MRI) potentially offers several advantages over positron emission tomography/computed tomography (PET/CT), for example, no CT radiation dose and soft tissue images from MR acquired at the same time as the PET. However, obtaining accurate linear attenuation correction (LAC) factors for the lung remains difficult in PET/MRI. LACs depend on electron density and in the lung, these vary significantly both within an individual and from person to person. Current commercial practice is to use a single‐valued population‐based lung LAC, and better estimation is needed to improve quantification. Given the under‐appreciation of lung attenuation estimation as an issue, the inaccuracy of PET quantification due to the use of single‐valued lung LACs, the unique challenges of lung estimation, and the emerging status of PET/MRI scanners in lung disease, a review is timely. This paper highlights past and present methods, categorizing them into segmentation, atlas/mapping, and emission‐based schemes. Potential strategies for future developments are also presented.

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Description and assessment of a registration-based approach to include bones for attenuation correction of whole-body PET/MRI

Cited by 32 publications

References 38 publications

Comparison of atlas-based techniques for whole-body bone segmentation

Comparison of atlas-based techniques for whole-body bone segmentation

Conspicuity of FDG-Avid Osseous Lesions on PET/MRI Versus PET/CT: a Quantitative and Visual Analysis

PET/MRI attenuation estimation in the lung: A review of past, present, and potential techniques

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