Field of view extension and truncation correction for MR‐based human attenuation correction in simultaneous MR/PET imaging

Blumhagen, Jan Ole; Braun, Heinrich; Ladebeck, Ralf; Fenchel, Matthias; Faul, David; Scheffler, Klaus; Quick, Harald H.

doi:10.1118/1.4861097

Cited by 46 publications

(63 citation statements)

References 35 publications

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“…During the development of PET/CT, this issue was also a problem, but it could be solved by implementing dedicated procedures for expanding the field of view (25). Similar promising and effective procedures have already been proposed and validated for PET/MR imaging and can be used to overcome this problem (26,27).…”

Section: Discussionmentioning

confidence: 99%

Reproducibility of MRI Dixon-Based Attenuation Correction in Combined PET/MR with Applications for Lean Body Mass Estimation

et al. 2016

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The aim of this study was to assess the reproducibility of standard, Dixon-based attenuation correction (MR-AC) in PET/MR imaging. A further aim was to estimate a patient-specific lean body mass (LBM) from these MR-AC data. Methods: Ten subjects were positioned in a fully integrated PET/MR system, and 3 consecutive multibed acquisitions of the standard MR-AC image data were acquired. For each subject and MR-AC map, the following compartmental volumes were calculated: total body, soft tissue (ST), fat, lung, and intermediate tissue (IT). Intrasubject differences in the total body and subcompartmental volumes (ST, fat, lung, and IT) were assessed by means of coefficients of variation (CVs) calculated across the 3 consecutive measurements and, again, across these measurements but excluding those affected by major artifacts. All subjects underwent a body composition measurement using air displacement plethysmography (ADP) that was used to calculate a reference LBM ADP . A second LBM estimate was derived from available MR-AC data using a formula incorporating the respective tissue volumes and densities as well as the subject-specific body weights. A third LBM estimate was obtained from a sex-specific formula (LBM Formula ). Pearson correlation was calculated for LBM ADP , LBM MR-AC , and LBM Formula . Further, linear regression analysis was performed on LBM MR-AC and LBM ADP. Results: The mean CV for all 30 scans was 2.1 ± 1.9% (TB). When missing tissue artifacts were excluded, the CV was reduced to 0.3 ± 0.2%. The mean CVs for the subcompartments before and after exclusion of artifacts were 0.9 ± 1.1% and 0.7 ± 0.7% for the ST, 2.9 ± 4.1% and 1.3 ± 1.0% for fat, and 3.6 ± 3.9% and 1.3 ± 0.7% for the IT, respectively. Correlation was highest for LBM MR-AC and LBM ADP (r 5 0.99). Linear regression of data excluding artifacts resulted in a scaling factor of 1.06 for LBM MR-AC . Conclusion: LBM MR-AC is shown to correlate well with standard LBM measurements and thus offers routine LBM-based SUV quantification in PET/MR. However, MR-AC images must be controlled for systematic artifacts, including missing tissue and tissue swaps. Efforts to minimize these artifacts could help improve the reproducibility of MR-AC. Dual -modality PET/CT imaging systems, combining CT with PET into a single imaging system, have become standard for acquiring colocalized metabolic and anatomic information in clinical practice (1). The effectiveness of PET/CT is due, in part, to the complementary role of CT in providing both an anatomic framework and reliable, quantitative attenuation values for tissues inside the field of view of the PET for CT-based attenuation correction (2). After the introduction of dual-modality MR and PET imaging (PET/MR), novel clinical applications of hybrid imaging are being actively developed (3). PET/MR imaging has the advantage of offering superior soft-tissue (ST) contrast and a wide array of functional, morphologic, and even metabolic clinical imaging protocols (4) within a single examination. However, correct att...

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Section: Discussionmentioning

confidence: 99%

Reproducibility of MRI Dixon-Based Attenuation Correction in Combined PET/MR with Applications for Lean Body Mass Estimation

et al. 2016

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“…The panelists reported on continuous refinement of strategies for MR-AC that included the integration of bone structure mapping and the acceptance of attenuation map templates for special MR coils, radiotherapy (RT) tables and ancillary devices, thus, making way for quantitative PET/MRI-guided radiation therapy planning [55][56][57]. Also, MR-based motion compensation has advanced beyond initial pilot data [54] towards more refined applications in neurology.…”

Section: Recent Advances or Achievementsmentioning

confidence: 99%

“…It cannot be stressed too greatly that one of the potential drivers for PET/MRI is improved quantitative information provided by a multimodality imaging approach. One example is the use of MRI navigator sequences to estimate a time-dependent motion vector that can then be incorporated into the PET reconstruction algorithm to further improve spatial resolution and reduce motion artefacts [54], or the use of the MRI data in attenuation correction of the PET emission data [55].…”

Section: Dialogue Board 5: Advanced Pet/ Mri-multi-parametric Imagingmentioning

confidence: 99%

Combined PET/MRI: Multi-modality Multi-parametric Imaging Is Here

et al. 2015

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This paper summarises key themes and discussions from the 4th international workshop dedicated to the advancement of the technical, scientific and clinical applications of combined positron emission tomography (PET)/magnetic resonance imaging (MRI) systems that was held in Tübingen, Germany, from February 23 to 27, 2015. Specifically, we summarise the three days of invited presentations from active researchers in this and associated fields augmented by round table discussions and dialogue boards with specific topics. These include the use of PET/MRI in cardiovascular disease, paediatrics, oncology, neurology and multi-parametric imaging, the latter of which was suggested as a key promoting factor for the wider adoption of integrated PET/MRI. Discussions throughout the workshop and a poll taken on the final day demonstrated that attendees felt more strongly that PET/MRI has further advanced in both technical versatility and acceptance by clinical and research-driven users from the status quo of last year. Still, with only minimal evidence of progress made in exploiting the true complementary nature of the PET and MRI-based information, PET/MRI is still yet to achieve its potential. In that regard, the conclusion of last year's meeting "the real work has just started" still holds true.

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“…Several approaches have been introduced recently that compensate for distortions and truncations in simultaneous PET/MR scanning. 26,27 For appropriate PET image quality and quantification, AC of the RT hardware components is essential. For easy and automatic AC of the devices, they should provide a rigid geometry and have a fixed position on the PET/MR systems patient table.…”

Section: Discussionmentioning

confidence: 99%

Towards integration of PET/MR hybrid imaging into radiation therapy treatment planning

et al. 2014

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Purpose: Multimodality imaging has become an important adjunct of state-of-the-art radiation therapy (RT) treatment planning. Recently, simultaneous PET/MR hybrid imaging has become clinically available and may also contribute to target volume delineation and biological individualization in RT planning. For integration of PET/MR hybrid imaging into RT treatment planning, compatible dedicated RT devices are required for accurate patient positioning. In this study, prototype RT positioning devices intended for PET/MR hybrid imaging are introduced and tested toward PET/MR compatibility and image quality. Methods: A prototype flat RT table overlay and two radiofrequency (RF) coil holders that each fix one flexible body matrix RF coil for RT head/neck imaging have been evaluated within this study. MR image quality with the RT head setup was compared to the actual PET/MR setup with a dedicated head RF coil. PET photon attenuation and CT-based attenuation correction (AC) of the hardware components has been quantitatively evaluated by phantom scans. Clinical application of the new RT setup in PET/MR imaging was evaluated in an in vivo study. Results: The RT table overlay and RF coil holders are fully PET/MR compatible. MR phantom and volunteer imaging with the RT head setup revealed high image quality, comparable to images acquired with the dedicated PET/MR head RF coil, albeit with 25% reduced SNR. Repositioning accuracy of the RF coil holders was below 1 mm. PET photon attenuation of the RT table overlay was calculated to be 3.8% and 13.8% for the RF coil holders. With CT-based AC of the devices, the underestimation error was reduced to 0.6% and 0.8%, respectively. Comparable results were found within the patient study. Conclusions:The newly designed RT devices for hybrid PET/MR imaging are PET and MR compatible. The mechanically rigid design and the reproducible positioning allow for straightforward CT-based AC. The systematic evaluation within this study provides the technical basis for the clinical integration of PET/MR hybrid imaging into RT treatment planning.

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Field of view extension and truncation correction for MR‐based human attenuation correction in simultaneous MR/PET imaging

Cited by 46 publications

References 35 publications

Reproducibility of MRI Dixon-Based Attenuation Correction in Combined PET/MR with Applications for Lean Body Mass Estimation

Reproducibility of MRI Dixon-Based Attenuation Correction in Combined PET/MR with Applications for Lean Body Mass Estimation

Combined PET/MRI: Multi-modality Multi-parametric Imaging Is Here

Towards integration of PET/MR hybrid imaging into radiation therapy treatment planning

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