Positron emission tomography (PET) attenuation correction artefacts in PET/CT and PET/MRI

Buchbender, Christian; Hartung-Knemeyer, Verena; Forsting, Michael; Antoch, Gerald; Heusner, Till A.

doi:10.1259/bjr.20120570

Cited by 36 publications

(26 citation statements)

References 14 publications

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“…This property is of particular relevance in PET/MR imaging because MR-based attenuation correction is generally less accurate than its PET/ CT counterpart (10-13). Not only are the attenuation coefficients a priori estimates rather than measurements, but there are also several sources of artifacts that can affect the attenuation map (14,15): field-of-view truncation, fat-water swaps, metal artifacts, and others.…”

Section: Implication For Patient Carementioning

confidence: 99%

Effect of Time-of-Flight Information on PET/MR Reconstruction Artifacts: Comparison of Free-breathing versus Breath-hold MR-based Attenuation Correction

Delso¹,

Khalighi²,

E³

et al. 2017

Radiology

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Purpose To evaluate the magnitude and anatomic extent of the artifacts introduced on positron emission tomographic (PET)/magnetic resonance (MR) images by respiratory state mismatch in the attenuation map. Materials and Methods The method was tested on 14 patients referred for an oncologic examination who underwent PET/MR imaging. The acquisition included standard PET and MR series for each patient, and an additional attenuation correction series was acquired by using breath hold. PET data were reconstructed with and without time-of-flight (TOF) information, first by using the standard free-breathing attenuation map and then again by using the additional breath-hold map. Two-tailed paired t testing and linear regression with 0 intercept was performed on TOF versus non-TOF and freebreathing versus breath-hold data for all detected lesions. Results Fluorodeoxyglucose-avid lesions were found in eight of the 14 patients included in the study. The uptake differences (maximum standardized uptake values) between PET reconstructions with free-breathing versus breath-hold attenuation ranged, for non-TOF reconstructions, from -18% to 26%. The corresponding TOF reconstructions yielded differences from -15% to 18%. Conclusion TOF information was shown to reduce the artifacts caused at PET/MR by respiratory mismatch between emission and attenuation data. (©) RSNA, 2016 Online supplemental material is available for this article. DOI: https://doi.org/10. 1148/radiol.2016152509 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-125777 Published Version Originally published at: Delso, Gaspar; Khalighi, Mohammed; Ter Voert, Edwin E G W; Barbosa, Felipe; Sekine, Tetsuro; Hüllner, Martin; Veit-Haibach, Patrick (2016 Purpose:To evaluate the magnitude and anatomic extent of the artifacts introduced on positron emission tomographic (PET)/ magnetic resonance (MR) images by respiratory state mismatch in the attenuation map. Materials and Methods:The method was tested on 14 patients referred for an oncologic examination who underwent PET/MR imaging. The acquisition included standard PET and MR series for each patient, and an additional attenuation correction series was acquired by using breath hold. PET data were reconstructed with and without time-of-flight (TOF) information, first by using the standard free-breathing attenuation map and then again by using the additional breath-hold map. Two-tailed paired t testing and linear regression with 0 intercept was performed on TOF versus non-TOF and free-breathing versus breath-hold data for all detected lesions. Results:Fluorodeoxyglucose-avid lesions were found in eight of the 14 patients included in the study. The uptake differences (maximum standardized uptake values) between PET reconstructions with free-breathing versus breath-hold attenuation ranged, for non-TOF reconstructions, from 218% to 26%. The corresponding TOF reconstructions yielded differences from 215% to 18%. Conclusion:TOF information was shown to red...

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Section: Implication For Patient Carementioning

confidence: 99%

Effect of Time-of-Flight Information on PET/MR Reconstruction Artifacts: Comparison of Free-breathing versus Breath-hold MR-based Attenuation Correction

Delso¹,

Khalighi²,

E³

et al. 2017

Radiology

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“…MR‐based AC is still a new concept that is supposed to support PET data quantification in the best possible way. All deviations from the real physical gamma quanta attenuation will ultimately lead to false values in PET quantification following attenuation correction . Administration of contrast agents before application of MR‐based AC due to changes in contrast potentially may lead to errors in tissue segmentation .…”

Section: Workflow and Standardizationmentioning

confidence: 99%

Integrated PET/MR

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Magnetic Resonance Imaging

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Integrated whole-body PET/MR hybrid imaging combines excellent soft tissue contrast and various functional imaging parameters provided by MR with high sensitivity and quantification of radiotracer metabolism provided by positron emission tomography (PET). While clinical evaluation now is under way, integrated PET/MR demands for new technologies and innovative solutions, currently subject to interdisciplinary research. Attenuation correction of human soft tissues and of hardware components has to be MR-based to maintain quantification of PET imaging because computed tomography (CT) attenuation information is missing. This brings up the question of how to provide bone information with MR imaging. The limited field-of-view in MR imaging leads to truncations in body imaging and MR-based attenuation correction. Another research field is the implementation of motion correction technologies to correct for breathing and cardiac motion in view of the relatively long PET data acquisition times. Initial clinical applications of integrated PET/MR in oncology, neurology, pediatric oncology, and cardiovascular disease are highlighted. The hybrid imaging workflow here has to be tailored to the clinical indication to maximize diagnostic information while minimizing acquisition time. PET/MR introduces new artifacts that need special observation and innovative solutions for correction. Finally, the rising need for appropriate phantoms and standardization efforts in PET/MR hybrid imaging is discussed.

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“…One of the main topics of controversy is how the attenuation correction of the PET images should be addressed (4)(5)(6). PET/CT machines provide the possibility of generating the annihilation photon attenuation map of the patient from a fast low-dose CT scan.…”

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confidence: 99%

Anatomic Evaluation of 3-Dimensional Ultrashort-Echo-Time Bone Maps for PET/MR Attenuation Correction

Delso¹,

Carl²,

Wiesinger³

et al. 2014

J Nucl Med

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Ultrashort-echo-time (UTE) sequences have been proposed in the past for MR-based attenuation correction of PET data, because of their ability to image cortical bone. In the present work we assessed the limitations of dual-echo UTE imaging for bone segmentation in head and neck imaging. Sequentially acquired MR and PET/CT clinical data were used for this purpose. Methods: Twenty patients referred for a clinical oncology examination were scanned using a trimodality setup. Among the MR sequences, a dual-echo UTE acquisition of the head was acquired and used to create tissue R2 maps. The different undesired structures present in these maps were identified by an experienced radiologist. Global and local measurements of the overlap between R2-based and CT-based bone masks were computed. Results: UTE R2 maps displayed a nonfunctional relation with CT data. The obtained bone masks showed acceptable overlap with the corresponding CT data, in the case of the skull itself (e.g., 47% mismatch for the parietal region), with decreased performance in the base of the skull and in the neck (e.g., 78% for the maxillary region). Unwanted structures were detected, both anatomic (e.g., sternocleidomastoid, temporal, and masseter muscles) and artifactual (e.g., dental implants and air-tissue interfaces). Conclusion: It is indeed possible to estimate the anatomic location of bone tissue using UTE sequences. However, using pure parametric maps for attenuation correction may lead to bias close to certain anatomic structures and areas of high magnetic field inhomogeneity. More sophisticated approaches are necessary to compensate for these effects. Twel ve years after its commercial introduction, integrated PET/CT has evolved into one of the major imaging procedures in oncology, infection imaging, and cardiology. However, PET/CT has several limitations, both technical and diagnostic, that have recently led to the emergence of hybrid PET/MR scanners (1-3). Among other advantages, PET/MR imaging offers superior soft-tissue contrast (e.g., higher sensitivity for small liver metastases, additional information for lesion characterization, and better depiction of pelvic structures) and lower radiation exposure to the patient. There are, however, several technical and clinical challenges that have to be solved before this modality can reach its full potential.One of the main topics of controversy is how the attenuation correction of the PET images should be addressed (4-6). PET/CT machines provide the possibility of generating the annihilation photon attenuation map of the patient from a fast low-dose CT scan. This has replaced the former slow measurement of this map by means of external 511-keV radiation sources, thus significantly reducing the total scan time.Several approaches are currently being investigated to generate valid annihilation photon attenuation maps from fast MR sequences (7-11). Comprehensive reviews of current MR-based attenuation correction methods, their advantages and limitations, are available in the literature (12,13).MR-...

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Positron emission tomography (PET) attenuation correction artefacts in PET/CT and PET/MRI

Cited by 36 publications

References 14 publications

Effect of Time-of-Flight Information on PET/MR Reconstruction Artifacts: Comparison of Free-breathing versus Breath-hold MR-based Attenuation Correction

Effect of Time-of-Flight Information on PET/MR Reconstruction Artifacts: Comparison of Free-breathing versus Breath-hold MR-based Attenuation Correction

Integrated PET/MR

Anatomic Evaluation of 3-Dimensional Ultrashort-Echo-Time Bone Maps for PET/MR Attenuation Correction

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