Improved Alignment of PET and CT Images in Whole-Body PET/CT in Cases of Respiratory Motion During CT

Hamill, James; Meier, Joseph; Cuellar, Sonia L. Betancourt; Sabloff, Bradley S.; Erasmus, Jeremy J.; Mawlawi, Osama

doi:10.2967/jnumed.119.235804

Cited by 9 publications

(14 citation statements)

References 17 publications

(24 reference statements)

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“…While longer acquisition times traditionally represent a balance between acquisition time and reduction in applied radiation dose, longer acquisitions can be associated with increased motion artefact, and point toward another key advantage in modern scanner design using proprietary endexpiratory PET acquisition for the reduction in respiratory motion artefact [25]. Likewise, while not the subject of this enquiry, the ability to increase numbers of patients examined through shorter-acquisition time is of considerable economic importance in an era of rapidly increasing utilisation of nuclear and molecular medicine imaging techniques.…”

Section: Discussionmentioning

confidence: 99%

Digital PET/CT allows for shorter acquisition protocols or reduced radiopharmaceutical dose in [18F]-FDG PET/CT

et al. 2021

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Purpose To establish the feasibility of shorter acquisition times (and by analogy, applied activity) on tumour detection and lesion contrast in digital PET/CT. Methods Twenty-one randomly selected patients who underwent oncological [18F]-FDG PET/CT on a digital PET/CT were retrospectively evaluated. Scan data were anonymously obtained and reconstructed in list-mode acquisition for a standard 2 min/bed position (bp), 1 min/bp and 30 s/bp (100%, 50% and 25% time or applied activity, respectively). Scans were randomized and read by two nuclear medicine physicians in a consensus read. Readers were blind to clinical details. Scans were evaluated for the number of pathological lesions detected. Measured uptake for lesions was evaluated by maximum and mean standardized uptake value (SUVmax and SUVmean, respectively) and tumour-to-backround ratio (TBR) were compared. Agreement between the three acquisitions was compared by Krippendorf’s alpha. Results Overall n = 100 lesions were identified in the 2 min and 1 min/bp acquisitions and n = 98 lesions in the 30 s/bp acquisitions. Agreement between the three acquisitions with respect to lesion number and tumour-to-background ratio showed almost perfect agreement (K’s α = 0.999). SUVmax, SUVmean and TBR likewise showed > 98% agreement, with longer acquisitions being associated with slightly higher mean TBR (2 min/bp 7.94 ± 4.41 versus 30 s/bp 7.84 ± 4.22, p < 0.05). Conclusion Shorter acquisition times have traditionally been associated with reduced lesion detectability or the requirement for larger amounts of radiotracer activity. These data confirm that this is not the case for new-generation digital PET scanners, where the known higher sensitivity results in clinically adequate images for shorter acquisitions. Only a small variation in the semi-quantitative parameters SUVmax, SUVmean and TBR was seen, confirming that either reduction of acquisition time or (by analogy) applied activity can be reduced as much as 75% in digital PET/CT without apparent clinical detriment.

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Section: Discussionmentioning

confidence: 99%

Digital PET/CT allows for shorter acquisition protocols or reduced radiopharmaceutical dose in [18F]-FDG PET/CT

et al. 2021

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“…Much work has been pursued previously to address these issues, namely respiratory gating of both PET and CT [ 5 – 8 ]. Until very recently, the only method used for gating PET or CT in clinical scans was external device-based gating (EDG) [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

Data-driven gated PET/CT: implications for lesion segmentation and quantitation

Thomas

Pan

2021

EJNMMI Phys

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Background Data-driven gating (DDG) can improve PET quantitation and alleviate many issues with patient motion. However, misregistration between DDG-PET and CT may occur due to the distinct temporal resolutions of PET and CT and can be mitigated by DDG-CT. Here, the effects of misregistration and respiratory motion on PET quantitation and lesion segmentation were assessed with a new DDG-PET/CT method. Methods A low-dose cine-CT was acquired in misregistered regions to enable both average CT (ACT) and DDG-CT. The following were compared: (1) baseline PET/CT, (2) PET/ACT (attenuation correction, AC = ACT), (3) DDG-PET (AC = helical CT), and (4) DDG-PET/CT (AC = DDG-CT). For DDG-PET, end-expiration (EE) data were derived from 50% of the total PET data at 30% from end-inspiration. For DDG-CT, EE phase CT data were extracted from cine-CT data by lung Hounsfield unit (HU) value and body contour. A total of 91 lesions from 16 consecutive patients were assessed for changes in standard uptake value (SUV), lesion glycolysis (LG), lesion volume, centroid-to-centroid distance (CCD), and DICE coefficients. Results Relative to baseline PET/CT, median changes in SUVmax ± σ for all 91 lesions were 20 ± 43%, 26 ± 23%, and 66 ± 66%, respectively, for PET/ACT, DDG-PET, and DDG-PET/CT. Median changes in lesion volume were 0 ± 58%, − 36 ± 26%, and − 26 ± 40%. LG for individual lesions increased for PET/ACT and decreased for DDG-PET, but was not different for DDG-PET/CT. Changes in mean HU from baseline PET/CT were dramatic for most lesions in both PET/ACT and DDG-PET/CT, especially for lesions with mean HU < 0 at baseline. CCD and DICE were both affected more by motion correction with DDG-PET than improved registration with ACT or DDG-CT. Conclusion As misregistration becomes more prominent, the impact of motion correction with DDG-PET is diminished. The potential benefits of DDG-PET toward accurate lesion segmentation and quantitation could only be fully realized when combined with DDG-CT. These results impress upon the necessity of ensuring both misregistration and motion correction are accounted for together to optimize the clinical utility of PET/CT.

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“…Respiratory motion can cause tumor motion, which may introduce misregistration between CT and PET. Both tumor motion and PET/CT misregistration degrade the quantification accuracy of the tumor, posing a significant challenge for quantification, localization, and treatment response assessment of the functional PET data 3,4 …”

Section: Introductionmentioning

confidence: 99%

“…However, this may cause uncertainty in the deformed CT anatomy because CT is acquired in free breathing, not breath hold. Deforming the PET data to misaligned CT guided by both the CT and PET respiratory signals was also reported 4 . However, this was an EDG method that required an RMD and associated computer for the acquisition of the respiratory signals of CT and PET data.…”

Section: Introductionmentioning

confidence: 99%

“…Both tumor motion and PET/CT misregistration degrade the quantification accuracy of the tumor, posing a significant challenge for quantification, localization, and treatment response assessment of the functional PET data. 3,4 The conventional approach to freeze tumor motion is to use external device gating (EDG) to bin PET data to multiple phases of respiration according to a respiratory signal produced by an external sensor that tracks the patient's breathing. 5,6 Several issues hinder the application of this method, including (1) effort and time to set up a gating device; (2) additional radiation exposure to the technologist for placing a respiratory monitoring device (RMD) on the patient injected with a radiopharmaceutical; (3) additional scan time for a preselected region potentially impacted by the respiratory motion during the scan; (4) complex post-processing of multiple phases of PET data 7 ; and (5) the requirement of EDG CT such as 4D CT 8 to match with EDG PET.…”

Section: Introductionmentioning

confidence: 99%

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Data‐driven gated CT: An automated respiratory gating method to enable data‐driven gated PET/CT

2022

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Background The accuracy of positron emission tomography (PET) quantification and localization can be compromised if a misregistered computed tomography (CT) is used for attenuation correction (AC) in PET/CT. As data‐driven gating (DDG) continues to grow in clinical use, these issues are becoming more relevant with respect to solutions for gated CT. Purpose In this work, a new automated DDG CT method was developed to provide average CT and DDG CT for AC of PET and DDG PET, respectively. Methods An automatic DDG CT was developed to provide the end‐expiratory (EE) and end‐inspiratory (EI) phases of images from low‐dose cine CT images, with all phases being averaged to generate an average CT. The respiratory phases of EE and EI were determined according to lung region Hounsfield unit (HU) values and body outline contours. The average CT was used for AC of baseline PET and DDG CT at EE phase was used for AC of DDG PET at the quiescent or EE phase. The EI and EE phases obtained with DDG CT were used for assessing the magnitude of respiratory motion. The proposed DDG CT was compared to two commercial CT gating methods: (1) 4D CT (external device based) and (2) D4D CT (DDG based) in 38 patient datasets with respect to respiratory phase image selection, lung HU, lung volume, and image artifacts. In a separate set of twenty consecutive PET/CT studies containing a mix of 18F‐FDG, 68Ga‐Dotatate, and 64Cu‐Dotatate scans, the proposed DDG CT was compared with D4D CT for impacts on registration and quantification in DDG PET/CT. Results In the EE phase, the images selected by DDG CT and 4D CT were identical 62.5% ± 21.6% of the time, whereas DDG CT and D4D CT were 6.5% ± 9.7%, and 4D CT and D4D CT were 8.6% ± 12.2%. These differences in EE phase image selection were significant (p < 0.0001). In the EI phase, the images selected by DDG CT and 4D CT were identical 68.2% ± 18.9% of the time, DDG CT and D4D CT were 63.9% ± 18.8%, and 4D CT and D4D CT were 61.2% ± 19.8%. These differences were not significant. The mean lung HU and volumes were not statistically different (p > 0.1) among the three methods. In some studies, DDG CT was better than D4D or 4D CT in the appropriate selection of the EE and EI phases, and D4D CT was found to reverse the EE and EI phases or not select the correct images by visual inspection. A statistically significant improvement of DDG CT over D4D CT for AC of DDG PET was also demonstrated with PET quantification analysis. When irregular breath cycles were present in the cine CT, DDG CT could be used to replace average CT for the improved AC of baseline PET. Conclusion A new automatic DDG CT was developed to tackle the issues of misregistration and tumor motion in PET/CT imaging. DDG CT was significantly more consistent than D4D CT in selecting the EE phase images as the clinical standard of 4D CT. When compared to both commercial gated CT methods of 4D CT and D4D CT, DDG CT appeared to be more robust in the lower lung and upper diaphragm regions where misregistration and tumor motion often occur. ...

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Improved Alignment of PET and CT Images in Whole-Body PET/CT in Cases of Respiratory Motion During CT

Cited by 9 publications

References 17 publications

Digital PET/CT allows for shorter acquisition protocols or reduced radiopharmaceutical dose in [18F]-FDG PET/CT

Digital PET/CT allows for shorter acquisition protocols or reduced radiopharmaceutical dose in [18F]-FDG PET/CT

Data-driven gated PET/CT: implications for lesion segmentation and quantitation

Data‐driven gated CT: An automated respiratory gating method to enable data‐driven gated PET/CT

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